JP4192399B2 - Oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grain-oriented electrical steel sheet suitable for use as an iron core material for electrical equipment such as transformers, generators, and rotating machines, and a method for manufacturing the same, and particularly to improve not only material characteristics but also actual machine characteristics. It is intended to be illustrated.
[0002]
[Prior art]
The grain-oriented electrical steel sheet is mainly used as a material for transformer cores and wound cores. In particular, from the viewpoint of reducing transmission and distribution costs, such grain-oriented electrical steel sheets have energy loss (iron) due to power conversion. Loss) is required.
One of the techniques for reducing the iron loss is to align the <001> axis, which is the easy axis of iron crystal, with the rolling direction, and the iron crystal structure is referred to as the Goss orientation {110} <001> orientation It is known that high magnetic permeability can be obtained and the iron loss is reduced by highly accumulating it.
[0003]
In order to obtain a crystal structure accumulated in such a Goss orientation, a phenomenon called secondary recrystallization is used. That is, in the thermal growth process of primary recrystallized grains, a desired structure can be obtained by preferentially growing only goss-oriented crystal grains using abnormal grain growth with extremely strong orientation selectivity. At this time, it is important to control the two points of orientation selectivity and abnormal grain growth rate in order to obtain a secondary recrystallized structure having a high degree of accumulation in the Goth orientation.
For this purpose, the primary recrystallized structure before the secondary recrystallization is set to a predetermined texture, and the precipitated dispersed phase called an inhibitor that selectively suppresses the growth of the primary recrystallized grains is formed in a uniform and appropriate size. It is required to form.
[0004]
In order to achieve the latter purpose, Japanese Patent Publication No. 46-23820 discloses a technique for forming a complex precipitation phase of MnSe or MnS and AlN and acting as a powerful inhibitor.
However, even if a crystal structure having a high degree of integration in the Goth direction is obtained by these techniques, the iron loss of the product is not necessarily reduced. This is because the secondary recrystallization grain size inevitably becomes coarse.
In order to solve this problem, Japanese Patent Publication No. 59-20745 discloses a technique for reducing the iron loss by reducing the average grain size of secondary recrystallized grains, and Japanese Patent Publication No. 4-19296 discloses a technique for reducing iron loss. Techniques for reducing iron loss by controlling the number and distribution of fine secondary grains are disclosed. However, the technology for refining the secondary grains is not compatible with the recent technical idea of grain-oriented electrical steel sheets that seeks to obtain a high magnetic flux density by enlarging only grains that are very close to the Goss orientation. The characteristic was deteriorated.
[0005]
On the other hand, as a method of artificially introducing magnetic poles into a steel plate to reduce the eddy current loss by narrowing the magnetic domain width, a laser beam (Japanese Patent Publication No. 57-2252) or a plasma flame (Japanese Patent Publication No. 7-7230) In addition, the method of irradiating the steel, etc., as a heat-resistant magnetic domain refinement method, is a method of forming grooves in the steel plate after secondary recrystallization by mechanical processing (Japanese Patent Publication No. 62-53579) or rolling before final finish annealing. A method of introducing linear notches in a direction orthogonal to the direction (Japanese Patent Publication No. 3-69968) is disclosed.
However, the methods disclosed in Japanese Patent Publication No. 57-2252 and Japanese Patent Publication No. 7-7230 have a problem that the magnetic domain refinement effect disappears due to strain relief annealing. In addition, the methods disclosed in Japanese Patent Publication No. 62-53579 and Japanese Patent Publication No. 3-69968 have a problem that the magnetic flux density in the high magnetic field region is deteriorated by the magnetic poles formed by the grooves.
[0006]
On the other hand, a technique for reducing the iron loss by improving the non-uniformity of the magnetic flux density inside the steel sheet due to the secondary recrystallization orientation distribution is disclosed by the present inventors in Japanese Patent Laid-Open Nos. 8-49045 and 8-288115. This is disclosed in Japanese Patent Laid-Open No. 9-209043 and the like.
By adjusting the aspect ratio of the secondary recrystallized grains and the crystal orientation difference between the secondary recrystallized grains adjacent to the direction perpendicular to the rolling (difference in orientation within the rolling surface) within the appropriate range, The main focus is to improve the iron loss by reducing the non-uniformity of the magnetic flux distribution inside the material.
When these technologies are applied, an effect of reducing iron loss can be obtained regardless of the presence or absence of magnetic domain subdivision treatment, but the control of crystal orientation becomes unstable and may cause sudden deterioration of magnetic characteristics. It was.
[0007]
Japanese Patent Laid-Open No. 9-143637 discloses a technique for improving iron loss by reducing the non-uniformity of magnetic flux density by appropriately controlling the form of secondary recrystallized grains (grain oblique angle). It is disclosed.
Although this technique can achieve a desired effect to some extent, there is a problem that uniformization is not sufficient because the control of the magnetic flux density distribution relies only on the index of the oblique angle of the grain boundary. Also. There was also a problem in that it was difficult to stably obtain a low oblique angle due to fluctuations in the steel composition, decarburization annealing, final finish annealing atmosphere, and the like.
[0008]
Furthermore, in JP-A-6-89805, Bi is contained, and the size of secondary grains in the rolling direction and in the direction perpendicular to the rolling direction is controlled within a predetermined range, and further inside the coarse secondary grains. A method of dispersing fine particles is disclosed.
However, in the case of this method, the coarsening of the secondary grains sometimes causes non-uniformity of the magnetic flux density distribution inside the steel sheet, and there is a problem that a sufficient iron loss reduction effect cannot be obtained. Such deterioration of the iron loss cannot be sufficiently improved only by dispersing fine grains in coarse grains.
[0009]
[Problems to be solved by the invention]
The present invention advantageously solves the above problem, and has excellent iron loss characteristics at the material stage regardless of the presence or absence of magnetic domain subdivision treatment, and also in actual machine iron loss characteristics after being incorporated in a transformer. The object is to propose an excellent grain-oriented electrical steel sheet together with its advantageous manufacturing method.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the inventors have found that the non-uniform distribution of magnetic flux density inside the steel sheet as described in JP-A-8-49045 is an influencing factor on the iron loss of the grain-oriented electrical steel sheet. Attention was paid and research was carried out to reduce iron loss by improving this.
As a result, it is a grain-oriented electrical steel sheet containing Bi in the base metal of the product plate, the secondary recrystallization grain size in the direction perpendicular to the rolling direction is large, and the deviation of the crystal orientation in the rolling plane is small, and later It has been found that when the oblique angle of the defined grain boundary is small, the magnetic flux density distribution inside the steel plate becomes uniform and a material with low iron loss can be obtained.
The present invention is based on the above findings.
[0011]
  That is, the gist configuration of the present invention is as follows.
1. The steel is a grain-oriented electrical steel sheet containing Si: 2.0 to 5.0 mass%, Mn: 0.04 to 0.15 mass% and Bi: 0.0003 to 0.05 mass%, with the balance being a composition of Fe and inevitable impurities, The area average value of the deviation angle from the rolling direction in the rolling plane of the crystal orientation [001] of the secondary recrystallized grains excluding the crystal grains having an equivalent circle diameter of 5 mm or less is 4 ° or less, and the maximum length in the direction perpendicular to the rolling is Grain boundary line segment L that approximates the grain boundary of secondary recrystallized grains excluding crystal grains with an area ratio of secondary recrystallized grains of 30 mm or more in the entire steel sheet to 70% or more and equivalent circle diameter of 5 mm or less._i Between the rolling direction of the steel sheet and the direction perpendicular to the rolling direction θ_i, And grain boundary line segment L_iLength of l_i From the following formula, the oblique angle <θ> calculated by the following formula is 25 ° or less, the thickness of the steel plate is 6 μm or less, the surface roughness (Ra) is 0.4 μm or less, and the applied tension in the rolling direction of the steel plate is 4.9. -39.3 MPa (0.5-4.0 kgf / mm²1) A grain-oriented electrical steel sheet having a single or composite non-magnetic coating film satisfying (per one side of steel sheet).
                              Record
[Expression 1]
2. 2. The grain-oriented electrical steel sheet according to 1 above, wherein Cr: 0.05 to 0.5 mass% is further contained in the steel.
3. In addition to steel, Sb: 0.001 to 0.10 mass%, Mo: 0.001 to 0.20 mass%, Cu: 0.01 to 0.30 mass%, Sn: 0.005-0.20 mass%, Ge: 0.005-0.20 mass%andB: 0.0010-0.010 mass%of3. The grain-oriented electrical steel sheet according to 1 or 2 above, which contains one or more selected from among them.
[0012]
4. Lines or continuous grooves with a depth of 2 to 15% of the plate thickness, a width of 30 to 300 μm, a distance of 2 to 50 mm, and an angle with the rolling direction of 60 to 90 ° on one or both sides of the steel plate It is characterized by having1, 2 or 3 aboveThe grain-oriented electrical steel sheet described.
[0013]
5. The surface of the steel sheet has a linear region having an interval of 2 to 50 mm and an angle with the rolling direction of 60 to 90 ° or a strain region continuous in a linear shape.1, 2 or 3 aboveThe grain-oriented electrical steel sheet described.
[0014]
6. There is no forsterite coating on the steel plate surfaceAny of the above 1-5The grain-oriented electrical steel sheet described.
[0015]
7. C: 0.03-0.10 mass%,
    Si: 2.0-5.0 mass%,
    Mn: 0.04-0.15 mass%
    One or two selected from S and Se: 0.005 to 0.040 mass%,
    sol.Al: 0.015-0.035 mass% and N: 0.003-0.010 mass% and / or
    B: 0.0005 to 0.0050 mass% and N: 0.001 to 0.010 mass%
And including
    Bi: 0.001 to 0.070 mass%
ContainsAnd the rest Fe And inevitable impuritiesA series of silicon-containing steel slabs that are heated, then hot-rolled, then combined with annealing and cold rolling to finish to the final thickness, then decarburized and then final final-annealed. In the method for producing a grain-oriented electrical steel sheet comprising the steps of
  The surface roughness (Ra) of the final cold-rolled sheet is 0.5 μm or less, the width of the steel strip during final finish annealing is 800 mm or more, and the Bi content in the slab is c₀ (mass%) On the other hand, the Bi content in the product plate steel is c₁ (mass%) c₁Is within the range satisfying the conditions of the following formulas (1), (2), (3), and the application amount of the annealing separator applied to the steel sheet surface before the final finish annealing, and 900-1100 during the final finish annealing. A method for producing a grain-oriented electrical steel sheet, characterized by determining a rate of temperature rise in a temperature range of ° C.
                        Record
              c₁≦ 0.85c₀             --- (1)
              c₁≧ 0.36c₀−0.0072 --- (2)
        0.05 ≧ c₁≧ 0.0003 --- (3)
[0016]
8). C: 0.03-0.10 mass%,
    Si: 2.0-5.0 mass%,
    Mn: 0.04-0.15 mass%
    One or two selected from S and Se: 0.005 to 0.040 mass%,
    sol.Al: 0.015-0.035 mass% and N: 0.003-0.010 mass% and / or
    B: 0.0005 to 0.0050 mass% and N: 0.001 to 0.010 mass%
And including
    Bi: 0.001 to 0.070 mass%
ContainsAnd the rest Fe And inevitable impuritiesA series of silicon-containing steel slabs that are heated and then hot-rolled, combined with annealing and cold rolling to finish to the final thickness, then decarburized and then final final-annealed. In the method for producing a grain-oriented electrical steel sheet comprising steps,
  The surface roughness (Ra) of the final cold-rolled sheet is 0.5 μm or less, the width of the steel strip during final finish annealing is 800 mm or more, and the amount of annealing separator applied to the steel sheet surface before final finish annealing is 2-9g / m per side²The grain temperature of the grain-oriented electrical steel sheet is characterized by controlling the rate of temperature rise in the temperature range of 900-1100 ° C during the final finish annealing to a range satisfying the conditions of the following formulas (4), (5), (6): Production method.
                        Record
              v ≦ 3σ + 5 --- (4)
              v ≧ 3σ−21 --- (5)
              v ≧ 2 --- (6)
        Where, v: temperature rising rate of 900-1100 ° C. (° C./h)
                σ: coating amount of separating agent per one side of steel sheet (g / m²)
[0017]
9. 9. The method for producing a grain-oriented electrical steel sheet according to 7 or 8, wherein Cr: 0.05 to 0.5 mass% is further contained in the slab.
Ten . During the slab, Sb : 0.001 ~ 0.10mass %, Mo : 0.001 ~ 0.20mass %, Cu : 0.01 ~ 0.30mass %, Sn : 0.005 ~ 0.20mass %, Ge : 0.005 ~ 0.20mass % And B: 0.0010 ~ 0.010 mass 10. The method for producing a grain-oriented electrical steel sheet according to the above 7, 8, or 9, characterized by containing one or more selected from%.
[0018]
11. The total amount of S and Se in the slab is set to 0.02 mass% or less, and nitriding is performed after the final cold rolling until the end of secondary recrystallization.~ Ten EitherThe manufacturing method of the grain-oriented electrical steel sheet of description.
[0019]
12. After the final cold rolling, on the surface of the steel sheet, a line or wire having a depth of 2 to 15% of the plate thickness, a width of 30 to 300 μm, an interval of 2 to 50 mm, and an angle with the rolling direction of 60 to 90 ° It is characterized by forming a continuous grooveAbove 7 ~ 11 EitherThe manufacturing method of the grain-oriented electrical steel sheet of description.
[0020]
13. After the final finish annealing, it is characterized by forming a linear region having a spacing of 2 to 50 mm and an angle with a rolling direction of 60 to 90 ° or a linear strain region.Above 7 ~ 11 EitherThe manufacturing method of the grain-oriented electrical steel sheet of description.
[0021]
14. After final finish annealing, after removing surface oxide and mirroring the surface of the steel, a tension film is formed.Above 7 ~ 13The manufacturing method of the grain-oriented electrical steel sheet in any one of.
[0022]
15. It is characterized in that the final finish annealing is performed using an annealing separator that does not cause forsterite to be formed on the steel plate surface or inhibits the formation.Above 7 ~ 14The manufacturing method of the grain-oriented electrical steel sheet in any one of.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described.
First, the experimental results on which the present invention is based will be described.
C: 0.06 mass%, Si: 3.3 mass%, Mn: 0.07 mass%, sol.Al: 0.03 mass%, N: 0.009 mass%, Se: 0.02 mass% and Mo: 0.02 mass% are contained as basic components, And five kinds of slabs containing Bi, 0, 0.001, 0.005, 0.01 and 0.02 mass%, respectively, were prepared, heated to 1400 ° C for 60 minutes by induction heating, and then hot rolled to a thickness of 2.5 mm by hot rolling. A steel plate was used. Next, after hot-rolled sheet annealing at 950 ° C for 1 minute, pickling, followed by primary cold rolling to a thickness of 1.5 mm, followed by intermediate annealing at 1050 ° C for 1 minute, then pickling Then, it was finished to a final thickness of 0.23 mm by secondary cold rolling. The surface roughness (Ra) at this time was 0.3 μm.
Next, the oxidation potential P (H₂O) / P (H₂) = 0.50, decarburization annealing was performed at 850 ° C. for 100 seconds. Then, after applying a sinter separating agent mainly composed of MgO, it was wound into a coil and subjected to final finishing annealing at a maximum temperature of 1200 ° C. for 10 hours. Note that the width of the steel strip at the time of final finish annealing was 1000 mm.
After the final finish annealing, the remaining annealing separation agent is washed away with water, and then an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica is applied at 5 g / m per side of the steel sheet.²The product was coated and baked at a weight per unit area.
The tension in the rolling direction applied to the surface of the product obtained in the above process was measured by the insulation coating on one side of the steel sheet and the warpage amount after removing the forsterite layer, and 6.86 MPa (0.7 kgf / mm²)Met.
[0024]
In addition, from the product plate thus obtained, a specimen having a width of 100 mm and a length of 400 mm was cut out, subjected to strain relief annealing, and then subjected to each test using a single plate magnetic tester (SST). Iron loss W of a piece_17/50 (Iron loss at Bm = 1.7 T, f = 50 Hz) and B₈  (Magnetizing force: magnetic flux density at 800 A / m) was measured.
From the measured specimen (100mm x 400mm), B₈ Were selected as high as 1.96 to 1.98 T, and these were macro-etched to reveal secondary grain boundaries, and the size and morphology of secondary recrystallized grains were observed and measured.
[0025]
In FIG.₈ The result of having investigated about the relationship between the area average value (<(alpha)) of the shift | offset | difference angle ((alpha) angle | corner) from the rolling direction in the rolling surface of the crystal orientation [001] about the sample of 1.95-1. . Here, <α> is the average of the absolute values of the α angle.
As is apparent from the figure, the iron loss increases as <α> increases. If <α> is 4 ° or less, W is relatively stable._17/50 An iron loss value of ≦ 1.0 W / kg is obtained.
However, it can be seen that the variation of the iron loss value is large only by arranging by <α>, and it is difficult to reduce the iron loss only by the control of <α>.
[0026]
Then, next, it tried to arrange | position an iron loss value with the length of the rolling grain perpendicular direction of a secondary grain.
From the crystal structure obtained by macroetching, the maximum length and area of each secondary grain in the direction perpendicular to the rolling direction are measured, and the ratio of crystal grains whose maximum length in the direction perpendicular to the rolling direction is 30 mm or more to the total area of the sample is r_Three It was determined.
FIG. 2 shows a sample having a <α> of 4 ° or less in FIG._Three And iron loss W_17/50 The result of having investigated about the relationship with is shown.
As shown in the figure, r_Three As iron increases, the iron loss is improved, r_Three ≧ 70% W_17/50 It can be seen that ≦ 0.95 W / kg is achieved stably.
However, r_Three The iron loss still varies due to the introduction of <α> and r_Three It can be seen that it is difficult to stably reduce the iron loss only by the control of the above.
[0027]
In addition to the above factors, the existence of secondary recrystallization grain boundaries extending obliquely with respect to the rolling direction is expected to affect the non-uniformity of the magnetic flux density inside the steel sheet. As an index to make it easier, we introduced the “oblique angle” of grain boundaries.
Here, in the method as defined in JP-A-9-143637, the oblique angle of a material having a large secondary particle size as the object of the present invention cannot be correctly evaluated. The oblique angle was defined in a new way.
That is, in the present invention, the average value in the grain boundary direction measured by the following method is defined as “oblique angle”.
[0028]
In the following description, a point sharing a grain boundary of three or more crystal grains is referred to as a “grain boundary multiple point”, and an intersection of the boundary between the grain boundary and the evaluation region is also included in the grain boundary multiple point. Also, the grain boundaries are divided at the grain boundary multiple points, and these divided grain boundaries are called `` grain boundary elements '', and each line segment when the grain boundary element is approximated by several line segments is expressed as `` It will be called "grain boundary line segment".
(1) The secondary recrystallization grain boundary is observed and determined. As a method for this, macro etching, magnetic domain observation, grain boundary magnetic pole detection, or the like can be used, but the observation method is not particularly limited. The evaluation region of the secondary grain structure is preferably 150 mm or more in the rolling direction and 100 mm or more in the direction perpendicular to the rolling.
[0029]
Hereinafter, graphic processing for obtaining the oblique angle is performed.
(2) A crystal grain having a circle equivalent diameter of 5 mm or less and having a small grain size has little influence on the non-uniformity of magnetic flux density, and therefore, a process of erasing a part of the grain boundary of such a fine grain is performed (see FIG. 3 (a)).
(B) When the fine grain shares a grain boundary with other crystal grains, the grain boundary element having the longest length among the grain boundary elements constituting the fine grain is eliminated (FIG. 4 (a-1) DA disappeared).
(B) When the minute grains are isolated, all the grain boundaries are eliminated.
[0030]
(3) Subsequently, the grain boundary line segment (L) is drawn with respect to the grain boundary after the processing of (2) by the following method to approximate the grain boundary to a straight line (FIG. 3 (b)).
(C) A half line (end point: P) and auxiliary lines parallel to the half line are assumed on both sides of the half line (FIG. 4 (b-1)). The distance d between the half line and the auxiliary line is 3 mm.
(D) When a half-line end point P is fixed to a certain grain boundary multipoint, and the grain boundary multipoint (Q) adjacent to P is connected, the actual grain boundary exists only in the region between the two auxiliary lines. When doing so, let PQ be the grain boundary line segment (FIG. 4 (b-2)).
(E) However, if the grain boundary line cannot be drawn under the above conditions (when the grain boundary element is bent greatly), the grain boundary line is determined by the following procedure. P is fixed at a certain grain boundary multipoint, and a point P ′ is provided on the grain boundary element toward the adjacent grain boundary multipoint so that the half line passes through P ′. When P 'is moved on the grain boundary element, the distance P-P' is maximized under the condition that the actual grain boundary between P-P 'does not protrude from the region between the two auxiliary lines. P ′ is taken (R), and the line segment PR is taken as a grain boundary line segment (FIG. 4 (b-2)).
Similarly, RR ′ is subtracted from R, R ′ giving the longest RR ′ is set as S, and the next grain boundary line segment is set as RS (FIG. 4 (b-3)).
Similarly, a half line is drawn from S. If S and the grain boundary multiple point T (FIG. 4 (b-4)) are connected by a half line, if the half line ST can be drawn without the actual grain boundary protruding from the region between the two auxiliary lines, ST Is a grain boundary line segment.
Straighten all grain boundaries as described above.
[0031]
(4) A certain grain boundary line segment L_i The length of l_i And L_i The smaller of the angle between the rolling direction and the direction perpendicular to the rolling direction is θ_i In this case, the oblique angle <θ> is derived from all the grain boundary lines by the following equation (7). (Fig. 3 (c))
[Expression 1]
[0032]
FIG. 5 shows r in FIG._Three For samples with ≧ 70%, oblique angle <θ> and iron loss W_17/50 The result of having investigated about the relationship of is shown. In FIG. 5, the slant angle <θ> was obtained by setting the distance d between the grain boundary line segment and the auxiliary line to 3 mm.
As is apparent from the figure, the iron loss W is at an oblique angle of 25 ° or less._17/50 Excellent characteristics of ≦ 0.85 W / kg can be obtained._17/50 ≦ 0.80 W / kg, an extremely excellent iron loss value is obtained as a plain material.
In addition, the area ratio of the crystal grains having a maximum length of 60 mm or more in the direction perpendicular to the rolling to the whole is expressed as r.₆ And r₆ It can be seen that a lower iron loss value can be obtained by stricter the condition of ≧ 70%.
[0033]
As described above, from the results of FIG. 1, FIG. 2 and FIG. 5, the average value <α> of the secondary grains and the maximum length in the direction perpendicular to the rolling and the oblique angle <θ> were appropriately controlled. It has been found that a material with iron loss characteristics can be obtained.
[0034]
The following mechanism is estimated about the reason why the low iron loss is obtained by controlling the factors as described above.
(1) Reduction of iron loss by reducing the average α angle
In crystal grains having an α angle larger than 0 °, the magnetic flux density is nonuniform in the crystal grains as shown in FIG. 6 due to the action of magnetic poles generated on the grain boundaries extending in the rolling direction. Therefore, it can be considered that by reducing the average value of the α angle, the distribution of the magnetic flux density is made uniform and the iron loss is reduced.
That is, when improving the magnetic flux density distribution to reduce the iron loss, the deviation angle (α angle, that is, the crystal orientation) in the rolling plane is not the conventional deviation angle between the rolling direction and the [001] direction. It can be said that it is necessary to appropriately control the angle between the direction in which [001] is projected on the rolling surface and the rolling direction.
[0035]
(2) Reduction of iron loss by increasing the length in the direction perpendicular to rolling
As shown in FIG. 7, the longer the secondary grains in the direction perpendicular to the rolling direction, the smaller the decrease in magnetic flux density in the crystal grains. Therefore, as in (1) above, increasing the length in the direction perpendicular to rolling is considered to make the magnetic flux density distribution inside the steel plate uniform and reduce iron loss.
[0036]
(3) Reduction of iron loss by lowering the oblique angle
The mechanism for reducing the iron loss due to the decrease in the oblique angle is considered as follows.
Now, when considering secondary grains with a small oblique angle as shown in FIG. 8 (a), the length of each magnetic domain ([001] direction) is the same. The amount of magnetic poles generated at the grain boundaries is equal. Therefore, when a magnetic field is applied to this grain, the amount of domain wall movement is the same in any magnetic domain, and there is no bias in magnetic flux density within the crystal grain. On the other hand, in the case of a grain having a large oblique angle (FIG. 8B), the length of each magnetic domain is different, so that the magnetic flux distribution is not uniform within the grain as shown in FIG. 8B '. (That is, the domain wall displacement is not uniform).
That is, since the driving force of domain wall movement by the applied magnetic field is proportional to the length of the magnetic domain, the domain wall movement amount increases as the magnetic domain is longer in the rolling direction. For this reason, in the grain-oriented electrical steel sheet having a large oblique angle, it is considered that the magnetic flux distribution becomes non-uniform inside the crystal grains and the iron loss deteriorates.
It is presumed that iron loss was reduced by appropriately controlling the above factors (1) to (3) to make the magnetic flux distribution inside the steel plate uniform.
[0037]
Then, the stable manufacturing method of the grain-oriented electrical steel sheet which has said ideal secondary recrystallization form was examined.
FIG. 9 shows the amount of Bi added to the slab and the above conditions (<α> ≦ 4 °, r_Three ≧ 70%, <θ> ≦ 25 °) The relationship with the appearance frequency of the sample (width: 100 mm × length: evaluated at 400 mm size) is shown.
As shown in the figure, the addition of 0.001 mass% or more of Bi facilitates the generation of secondary grains in the form of secondary grains as defined in the present invention. It can be seen that it is extremely advantageous to contain Bi in the raw material in order to produce.
However, the ratio of obtaining ideal secondary grains is only about 50% only by adding Bi to the material, and it is difficult to stably reduce the iron loss.
[0038]
Therefore, the requirements of the present invention (<α> ≦ 4 °, r_Three ≧ 70%, <θ> ≦ 25 °) was examined for a method for more reliably manufacturing products satisfying the requirements.
In the examination experiment, when manufacturing the product in the same process as the above experiment, the application amount of the annealing separator mainly composed of MgO (per one side of the steel plate) is 1 to 12 g / m² When the temperature increase rate in the temperature range of 900 to 1100 ° C is changed in the range of 1 to 32.5 ° C / h during the final finish annealing, it remains in the steel due to such changes in the final finish annealing conditions. It was found that the amount of Bi changed.
[0039]
FIG. 10 shows the amount of Bi added to the material and the amount of Bi remaining in the product plate iron (<α> ≦ 4 °, r_Three (≧ 70%, <θ> ≦ 25 °) The results of examining the relationship with the occurrence frequency of the sample satisfying the conditions of:
From the results in Fig. 10, the Bi content in the material is expressed as c₀ (mass%), and Bi content in the product plate steel₁ (mass%) c₁Is controlled to satisfy the conditions of the following formulas (1), (2), and (3), it can be seen that the product of secondary grains defined in the present invention can be stably obtained.
Record
c₁≦ 0.85c₀             --- (1)
c₁≧ 0.36c₀−0.0072 --- (2)
0.05 ≧ c₁≧ 0.0003 --- (3)
[0040]
Next, Fig. 11 shows the results of investigating the relationship between the application amount of the annealing annealing separator and the temperature rise rate in the temperature range of 900 to 1100 ° C during the final finish annealing and the Bi residual amount in the product sheet iron. The case where the Bi content is (a) 0.03 mass% and (b) 0.01 mass% are shown respectively.
As is clear from the figure, the coating amount (per side) of the separating agent is σ (g / m²) And during final finish annealing, when the rate of temperature rise in the temperature range of 900 to 1100 ° C is assumed to be v (° C / h), σ and v are controlled within the range satisfying the conditions of the following formulas (4) and (5) By doing so, the amount of Bi in the product sheet metal can be set within the appropriate range found in FIG.
On the other hand, when the rate of temperature rise in the temperature range of 900 to 1100 ° C is lower than 2 ° C / hr, or the coating amount of the annealing separator is 9 g / m.²In the case of exceeding the above, magnetic deterioration, which appears to be due to deterioration of the precipitation dispersion type inhibitor (AlN, MnSe), occurred. Also, the application amount of annealing separator is 2g / m²If it is less than the range, the steel sheets laminated during the final finish annealing are fused together, so v and σ must satisfy Eqs. (6) and (7) simultaneously with Eqs. (4) and (5). There is.
Record
v ≦ 3σ + 5 --- (4)
v ≧ 3σ−21 --- (5)
v ≧ 2 --- (6)
2 ≦ σ ≦ 9 --- (7)
[0041]
As described above, it has been clarified that when an appropriate amount of Bi remains in the product plate steel, the secondary grain shape defined in the present invention can be obtained.
Here, the reason why the shape of the secondary grains is optimized by the appropriate amount of Bi remaining in the steel is not necessarily clearly clarified, but Bi is not limited to the extremely high temperature region during the final finish annealing. It is considered that the restraining force is maintained at a high temperature by remaining in the steel, and the effect of suppressing the generation of grain boundaries in the oblique direction is achieved while increasing the grain size in the direction perpendicular to the rolling. Moreover, when there is too much Bi remaining in the steel, it is presumed that the coarsening of the particle size proceeds excessively, and the frequency of occurrence of grain boundaries having a large oblique angle increases again.
In addition, from the results in Fig. 11, it is considered that the rate of temperature increase during final finish annealing and the amount of annealing separator applied affect the disappearance of Bi from the steel during the temperature increase process. It is possible to optimize the amount of Bi in the product plate iron.
[0042]
Next, when a model transformer was produced using the grain-oriented electrical steel sheet that achieved the low iron loss value by the secondary grain shape control and the iron loss of the actual machine was measured, it was higher than that of a normal product. F. (Ratio of actual machine iron loss to material iron loss).
This is because the amount of the magnetic field leaking from the grain boundary increases due to the shape change of the secondary recrystallized grain boundary. F. It is estimated that the increase of
[0043]
Therefore, in order to reduce the influence of the leakage magnetic field between the stacks, the thickness of the nonmagnetic material layer (forsterite + insulating coating) on the steel sheet surface and the surface roughness of the product were investigated.
As a result, by keeping both of these below a certain value, F. It was found that the increase in the amount can be prevented.
FIG. 12 shows the nonmagnetic layer thickness and surface roughness, F. Shows the relationship.
As can be seen from the figure, the thickness of the non-magnetic layer on the steel sheet surface is set to 6 μm or less and the surface roughness is set to 0.4 μm or less. F. It was found that a good value of 1.20 or less can be obtained.
[0044]
Next, the reason why the numerical values of the respective constituent requirements are limited to the above ranges for the grain-oriented electrical steel sheet of the present invention will be described.
Products in plate iron Si amount: 2.0 ~ 5.0 mass %
Si is an element necessary not only to increase the electric resistance and lower the iron loss, but also to stabilize the BCC structure of iron and enable high-temperature heat treatment, and requires at least 2.0 mass%. If it exceeds 5.0 mass%, cold rolling becomes difficult, so the Si content is limited to the range of 2.0 to 5.0 mass%.
[0045]
Products in plate iron Bi amount: 0.0003 ~ 0.05mass %
Bi is AIN, MnS, MnSe, Cu_2-X Se, Cu_2-X It is well known as an element that enhances the ability to suppress normal grain growth and improves the magnetic flux density by coexisting with a precipitation dispersion type inhibitor such as S. In the present invention, all Bi is added during final finish annealing. By making it not disappear from the steel, the ideal grain boundary shape defined in the present invention is obtained. Therefore, it is indispensable that Bi is present in the base iron of the product plate, but the effect of optimizing the grain boundary shape does not appear unless the Bi amount is less than 0.0003 mass%. On the other hand, when it exceeds 0.05 mass%, hysteresis loss increases. Therefore, it was limited to the range of 0.0003 to 0.05 mass% as the Bi amount in the product plate iron.
[0046]
The maximum length in the direction perpendicular to rolling is 30mm The area ratio of the above grains: 70 % Or more (preferably the maximum length in the direction perpendicular to rolling is 60mm The area ratio of the above grains: 70 %more than)
The present invention intends to achieve a low iron loss by uniformizing the distribution of magnetic flux density inside the steel sheet by controlling the form and orientation of secondary recrystallized grains. As shown in FIG. 7, as the length of the secondary grains in the direction perpendicular to the rolling direction increases, the area where the magnetic flux density is reduced due to the shift of the α angle becomes smaller, and the magnetic flux density distribution becomes uniform. Accordingly, a longer length in the direction perpendicular to the rolling is advantageous for uniforming the magnetic flux density distribution. From the results shown in FIG. 2, the area ratio r of crystal grains having a length in the direction perpendicular to the rolling of 30 mm or more._Three Is 70% or more, and a low iron loss is obtained. Therefore, it is limited to the above range. Further, as shown in FIG. 5, the area ratio r of crystal grains having a length in the direction perpendicular to the rolling of 60 mm or more.₆ Is less than 70%, and even lower iron loss can be stably obtained.₆ ≥70% is recommended.
Note that the maximum length of the secondary recrystallized grains in the direction perpendicular to the rolling direction is such that two straight lines parallel to the rolling direction do not cross the secondary grain boundaries from both sides of the secondary recrystallized grains, as shown in FIG. The distance between these lines should be in contact with.
[0047]
The maximum length in the direction perpendicular to rolling is 30mm Regarding the above grains, the area average value of the deviation angle (α angle) from the rolling direction in the rolling plane of the crystal orientation [001] is 4 ° or less.
With the mechanism described with reference to FIG. 6, the uniformity of the magnetic flux density is lost due to the increase of the α angle among the crystal orientations. Therefore, in order to make the magnetic flux density uniform, it is effective to reduce the average value of the α angle. Such an effect contributes greatly to the overall iron loss according to the area of the crystal grains, and is almost negligible for grains having an equivalent circle diameter of less than 5 mm. Therefore, the area of the α angle for grains having an equivalent circle diameter of 5 mm or more. It is better to take an average and set this as <α>.
Here, <α> is the sum of the absolute value of the α angle of each crystal grain multiplied by the grain area ratio (the ratio of the grain area to the total area of the evaluation frame).
As shown in FIG. 1, since the average value <α> of α angles of crystal grains having a maximum length in the direction perpendicular to the rolling of 30 mm or more is 4 ° or less, low iron loss can be obtained.
[0048]
Oblique angle: twenty five ° or less (preferably 20 ° or less)
By reducing the oblique angle (<θ>) of the secondary grains by the mechanism described in FIG. 8, it is considered that the magnetic flux density distribution is made uniform and the iron loss is reduced. As shown in FIG. 5, by setting <θ> to 25 ° or less, preferably 20 ° or less, extremely low iron loss can be stably obtained, so the oblique angle <θ> is limited to this range.
In addition, crystal grains having an equivalent circle diameter of 5 mm or less have a small effect on the distribution of magnetic flux density, and are therefore excluded from the evaluation of the oblique angle.
[0049]
As a method of measuring the oblique angle, the method described above is suitable as a method that can be evaluated even when the crystal grain size is large. In the method described with reference to FIG. 4, the distance d between the half line and the auxiliary line is 3 mm. However, when approximating the secondary recrystallized grain shape, d is preferably about 0.5 to 5 mm.
This is because if d exceeds 5 mm, the actual grain boundary and the approximate grain boundary due to the grain boundary line segment are greatly shifted, and the oblique angle cannot be accurately evaluated. On the other hand, if d is extremely small, l_i And θ_i This is because the measurement error becomes large and the oblique angle cannot be accurately evaluated.
In the above-described method for measuring the oblique angle, there is a slight error in <θ> depending on where the point at which the grain boundary line segment starts to be drawn (the point where the half line P is placed first) is generated. The value does not change significantly.
In addition, even if the method is different from the grain boundary approximation method defined in the present invention, as long as it is a method capable of linear approximation reflecting the actual grain boundary, as in the present invention, the oblique angle measurement method can be used. Can be used.
The evaluation region of the above secondary recrystallized grain morphology (length in the perpendicular direction of rolling, α angle, oblique angle) should be 200 mm or more in the rolling direction and 100 mm or more in the perpendicular direction of rolling. This is because if the evaluation region is too narrow, the number of crystal grains contained is extremely small, and accurate evaluation cannot be performed.
[0050]
Nonmagnetic layer thickness on steel plate surface: 6μ m Below, surface roughness (Ra) : 0.4 μ m Less than
Although the grain-oriented electrical steel sheet with extremely low iron loss can be obtained by taking the secondary grain form described above, when an actual transformer is produced using this grain-oriented electrical steel sheet, the building factor B.I. F. Deteriorates.
In order to avoid this, as shown in FIG. 12, it is necessary to limit the thickness of the nonmagnetic layer on the surface of the steel sheet to 6 μm or less and to suppress the surface roughness (Ra) to 0.4 μm or less.
[0051]
Here, the B.B. F. The reason for the reduction is not necessarily clear, but it is thought to be caused by a decrease in the nonmagnetic space between the steel plates.
That is, the transitional magnetic flux concentration between the steel plate surfaces occurs near the transformer joint due to the change in the shape of the crystal grain boundary. F. However, if the thickness of the non-magnetic space between the steel sheets is reduced, the transition area of the magnetic flux between the steel sheet surfaces will be dispersed, and it is estimated that the in-plane eddy current will be reduced. . Further, since the volume of the nonmagnetic space between the steel plates also increases with an increase in the roughness of the steel plate surface, it is necessary to consider it simultaneously with the thickness of the nonmagnetic layer such as a coating.
Here, when the thickness of the non-magnetic layer on the steel sheet surface exceeds 6 μm or the surface roughness (Ra) exceeds 0.4 μm, the volume of the non-magnetic space when the grain-oriented electrical steel sheet is assembled in the transformer increases. B. F. However, it was limited to the above range.
As a method for obtaining such a product, a method for reducing the surface roughness (Ra) of the final cold-rolled sheet to 0.5 μm or less, a method for reducing the addition amount of coarse silica in the insulating coating liquid, and the like are effective. is there.
[0052]
Applied tension in the rolling direction of the steel sheet surface: 4.9 ~ 39.3 MPa (0.5 ~ 4.0 kgf / mm ² ) (Per one side of steel plate)
It is known that the presence of a tension coating on the steel sheet surface reduces the eddy current loss by narrowing the magnetic domain width. However, when trying to reduce iron loss by making the magnetic flux density distribution uniform as in the present invention. In particular, it is necessary to increase the tension applied in the rolling direction of the steel sheet to enhance the fragmentation effect.
For this purpose, the surface coating may be a single coating or a composite coating of two or more. Usually, forsterite is formed as a coating on the surface of the ground iron, and a phosphate-based coating is formed thereon. In addition, there are known tension coatings such as TiN and glass coating, all of which are applicable to the present invention.
Here, as a measuring method of the tension in the rolling direction applied from the surface of the steel plate, a method of calculating from the warpage amount of the steel plate after removing the coating layer on one side of the steel plate is suitable.
The tension applied by such a surface coating is 4.9 MPa (0.5 kgf / mm²) Is less effective in reducing iron loss, while 39.3 MPa (4.0 kgf / mm²) Exceeds the above range because the effect of reducing iron loss by tension is saturated.
[0053]
Conditions for grooves and strain regions
By satisfying the above requirements, a grain-oriented electrical steel sheet with extremely low iron loss can be stably obtained. However, the effect of the present invention is achieved by uniformizing the magnetic flux density distribution inside the steel sheet. If the technology is applied, a further excellent iron loss reduction effect can be obtained by these addition effects.
As a method for subdividing magnetic domains, a method of forming grooves on the steel sheet surface is effective. On one or both surfaces of the steel sheet, depth: 2 to 15% of the plate thickness, width: 30 to 300 μm, interval: 2 to 50 mm, It is preferable to form a linear shape or a linearly continuous groove satisfying an angle of 60 to 90 ° with the rolling direction. Outside this range, the amount of magnetic poles generated on the groove wall surface becomes insufficient or excessive, and a sufficient iron loss reduction effect cannot be obtained.
In addition, it is also effective to obtain a magnetic domain refinement effect on the surface of the steel sheet by forming a linear region having a spacing of 2 to 50 mm and an angle between the rolling direction of 60 to 90 ° or a linearly strained region. However, if the strain region is out of the above range, the amount of magnetic pole introduced by the 90 ° magnetic domain generated in the strain region is out of the appropriate range, and a sufficient iron loss reduction effect cannot be obtained. did.
[0054]
Removal or non-formation of forsterite film on steel plate surface
The forsterite film present on the surface of ordinary grain-oriented electrical steel sheet is mainly composed of annealing separator MgO and SiO on the steel sheet surface.₂It is an excellent film that is formed during final finish annealing due to the reaction of, and has both a tension imparting effect and an insulating effect at the same time. Increase to increase hysteresis loss. This forsterite film is Mg₂SiO_Four Is the main component, but FeAl₂O_Four, TiN containing a trace amount is also targeted.
Hysteresis loss can be reduced by removing such a forsterite layer by pickling after final finish annealing or not forming it during final finish annealing.
Since the present invention is a technique for reducing iron loss by making the magnetic flux distribution inside the steel plate uniform, an effect of reducing iron loss can be additionally obtained by using it together with a technique for reducing pinning of domain wall motion. Furthermore, extremely excellent iron loss can be obtained by using such a technique in combination with the above-mentioned magnetic domain fragmentation treatment.
[0055]
Next, the reason for limitation regarding the manufacturing method of the grain-oriented electrical steel sheet of this invention is described.
In the material Bi Content and product in plate iron Bi Provisions regarding the content relationship
The grain-oriented electrical steel sheet of the present invention can be obtained by allowing Bi of 0.0003 mass% or more to remain in the product base metal. In order to obtain a product with a desired secondary grain shape more stably, FIG. As shown in Fig. 2, it is important to properly control the relationship between the amount of Bi in the slab and the amount of Bi in the product plate iron, and the Bi content in the slab c₀ (mass%) and Bi content in product plate iron₁ For (mass%), it is necessary to satisfy the relationships of the following formulas (1) to (3).
Record
c₁≦ 0.85c₀             --- (1)
c₁≧ 0.36c₀−0.0072 --- (2)
0.05 ≧ c₁≧ 0.0003 --- (3)
If the amount of Bi in the product plate iron is less than the values of the formulas (2) and (3), the Bi in the steel will rapidly escape during the final finish annealing. It is thought not to be. On the other hand, when the amount of Bi in the product plate steel exceeds the formula (1), it is estimated that the secondary recrystallization start temperature rises excessively and the desired secondary grains may not be obtained. The
Therefore, it is important to control the relationship between the Bi amount in the slab and the Bi amount in the product plate iron within a range that satisfies the equations (1), (2), and (3).
[0056]
Amount of annealing separator applied, heating rate during final finish annealing
The present invention is a grain-oriented electrical steel sheet having an ideal secondary recrystallized grain shape obtained by leaving a predetermined amount of Bi in the product plate iron, in order to stably produce this, It is important to control the amount of Bi in the product sheet metal to an appropriate range according to the amount of Bi in the slab.
The amount of Bi in the product plate can be appropriately controlled by the final finish annealing conditions. In other words, Bi disappears from the steel while affecting the secondary recrystallization in the temperature range of 900-1100 ° C during the temperature increase of the final finish annealing, so the temperature increase rate in this temperature range and the flowability between the coil layers It is necessary to control properly. When the rate of temperature rise is slower than the relationship of formula (5) (v ≧ 3σ−21), the disappearance of Bi in the steel during final finish annealing proceeds excessively, and good secondary grains cannot be obtained. On the other hand, when the rate of temperature increase exceeds the formula (4) (v ≦ 3σ + 5), the residual amount of Bi in the steel becomes excessive, and in this case, the secondary grain morphology also deteriorates.
[0057]
Also, the heating rate is less than 2 ° C / hr, or the separating agent coating amount is 9 g / m.²If it is too high, the precipitation-dispersed inhibitor such as AlN will deteriorate, and good magnetic properties cannot be obtained. On the other hand, the separating agent coating amount is 2 g / m²If it is less than the range, fusion between the steel plates occurs during the final finish annealing. Therefore, the application amount of the annealing separator is 2 to 9 g / m per one side of the steel plate.²During final finish annealing, the rate of temperature rise in the temperature range of 900 to 1100 ° C. is in a range that satisfies the following formulas (4), (5), and (6).
Record
v ≦ 3σ + 5 --- (4)
v ≧ 3σ−21 --- (5)
v ≧ 2 --- (6)
Where, v: temperature rising rate of 900-1100 ° C. (° C./h)
σ: coating amount of separating agent per one side of steel sheet (g / m²)
[0058]
Steel strip width during final finish annealing, surface roughness of final cold rolled sheet
As described above, if the flowability between the coil layers is excessively high during final finish annealing, Bi purification proceeds at a low temperature, and Bi depletion occurs in steel, making it impossible to obtain ideal secondary recrystallized grains. . For this reason, it is necessary not to excessively increase the gas flowability between the coil layers. The flowability of the atmosphere when Bi is purified decreases as the width of the steel strip increases, and improves as the surface roughness of the coil increases. Therefore, in order to keep the flowability of the atmosphere between the coil layers low, the width of the steel strip should be 800 mm or more, and the surface roughness (Ra) of the steel sheet after the final cold rolling should be 0.5 μm or less.
In the present invention, B.I. F. The surface roughness (Ra) of the product surface is specified to be 0.4 μm or less in order to prevent deterioration of the steel sheet.To satisfy this condition, however, the surface roughness (Ra) of the steel sheet after the final cold rolling should be 0.5 μm or less. There is a need to.
[0059]
Magnetic domain subdivision processing
When producing grain-oriented electrical steel sheets by the above method, it is possible to add a magnetic domain refinement treatment to the effect of reducing the iron loss by magnetic domain refinement to the effect of reducing the iron loss by homogenizing the magnetic flux distribution. it can.
The heat-resistant magnetic domain subdivision methods include the method of forming grooves in the final cold-rolled sheet and the steel sheet after final finish annealing by etching, or mechanically forming the grooves with a gear roll on the final finish annealed sheet or the plate after applying the insulating coating. The forming method and other groove forming techniques can be used.
Further, as a non-heat-resistant magnetic domain subdivision method, there is a method of introducing strain by local heating with laser light or plasma.
These heat-resistant magnetic domain subdivision methods and non-heat-resistant magnetic domain subdivision methods can be used in combination.
[0060]
Mirror treatment / Forsterite film not formed
Normally, forsterite formed during the final finish annealing is known to exhibit the effect of subdividing the magnetic domain by the tension on the steel sheet, and to reduce the eddy current loss. Has the effect of increasing the hysteresis loss. Therefore, the hysteresis loss can be reduced by applying a coating having a tension applying effect and an insulating effect after the surface of the ground iron is mirror-finished.
The present invention mainly aims to reduce eddy current loss by bringing the distribution of magnetic flux density inside the steel sheet closer to the ideal state through shape control of the secondary recrystallized grains. It is possible to reduce the iron loss very effectively by simultaneously performing the reduction. Further, as described above, the B.D. F. Although the surface roughness of the product was specified to prevent the deterioration of the surface, the surface roughness after coating application decreased due to the mirror surface treatment of the base iron surface. F. It also helps prevent deterioration.
[0061]
In order to obtain the smooth ground iron surface as described above, it is effective to remove the oxide on the surface of the final finish annealed plate by mechanical polishing or pickling and then mirror-finish it by pickling or electrolytic treatment. . In addition, the use of a technique in which forsterite is not present on the steel sheet surface on the surface of the final finish annealed sheet and the application of a method combining this with the above-described mirror finishing treatment also effectively reduce iron loss. As such a method, there are a method of using alumina or the like as a sinter separation agent, a method of adding a chloride in MgO, and the like, and any of them can be applied.
As described above, any known method such as an ion plantation method or a sol-gel method can be applied as a method for forming an insulating / tension coating on the final finish annealed plate having a mirror-finished surface.
[0062]
Nitriding between decarburization annealing and secondary recrystallization
In the present invention, Bi, AlN and / or BN, and MnS and / or MnSe are used as inhibitors.
Even when the amount of the inhibitor component in the slab is insufficient, the amount of nitrogen in the steel is increased during the production process to increase the fine dispersion of AlN and BN. It is possible to obtain characteristics. Such nitriding treatment is desirably performed after the final cold rolling with a thin plate thickness in order to efficiently perform nitriding. Moreover, it is necessary to carry out before the start of secondary recrystallization for the purpose of strengthening the ability to suppress normal grain growth in the primary grains.
[0063]
Next, the reason why the component composition of the material is limited to the above range in the production method of the present invention will be described.
C: 0.03 ~ 0.10mass%
C is not only effective for improving the hot-rolled structure by using the γ-α transformation, but is also an element useful for the generation of goth-oriented crystal grains, but if the content is less than 0.03 mass%, Since the addition effect is poor, and if it exceeds 0.10 mass%, there is a risk of decarburization failure during decarburization annealing, so the C content is limited to a range of 0.03 to 0.10 mass%.
[0064]
Si: 2.0 to 5.0 mass%
Si is an element necessary not only for increasing electric resistance and reducing iron loss, but also for stabilizing the BCC structure of iron and enabling high-temperature heat treatment, and requires at least 2.0 mass%. If it exceeds 5.0 mass%, cold rolling becomes difficult, so the Si content is limited to the range of 2.0 to 5.0 mass%.
[0065]
Mn: 0.04-0.15 mass%
  Mn not only effectively contributes to the improvement of hot brittleness of steel, but when S and Se are mixed, precipitates such as MnS and MnSe are formed and function as an inhibitor. . However, if the content is less than 0.04 mass%, the above effect is insufficient. On the other hand, if it exceeds 0.15 mass%, precipitates such as MnSe are coarsened and the effect as an inhibitor is lost. It was limited to the range of 0.15 mass%.
  Also this Mn : 0.04 ~ 0.15mass % Is an essential component in the grain-oriented electrical steel sheet as a product.
[0066]
S and / or Se: 0.005 to 0.040 mass%
Se and S combine with Mn and Cu to form MnSe, MnS, Cu_2-X Se, Cu_2-X It is a useful component that forms S and exhibits an inhibitory action as a dispersed second phase in steel. However, if the content is less than 0.005 mass%, the effect of addition is poor. On the other hand, if it exceeds 0.040 mass%, not only the solid solution during slab heating becomes incomplete, but it also causes defects on the product surface. In either case of single addition or composite addition, the content was within the range of 0.005 to 0.040 mass%.
When the slab heating temperature is a low temperature heating of 1350 ° C. or lower and the inhibitor is strengthened by nitriding after the end of the cold rolling process, S and Se are completely dissolved in the slab heating process. The total amount of Se is preferably 0.02 mass% or less. This is because when these total amounts are added in excess of 0.02 mass%, coarse precipitates of MnS and MnSe are generated and the magnetic properties are deteriorated.
[0067]
sol.Al: 0.015-0.035 mass%
Al is a useful element that forms an AIN in steel and acts as an inhibitor as a dispersed second phase. However, if the addition amount is less than 0.015 mass%, a sufficient amount of precipitation cannot be secured, while 0.035 mass% When added in excess of, AIN precipitates coarsely and loses its action as an inhibitor, so it was limited to a range of 0.015 to 0.035 mass% as sol.Al.
[0068]
B: 0.0005-0.0050 mass%
B is a useful element that forms BN in steel and acts as an inhibitor as a dispersed second phase in the same manner as AIN. However, if the content is less than 0.0005 mass%, the amount of precipitated BN is not sufficiently secured. On the other hand, if added over 0.0050 mass%, BN coarsely precipitates and the action as an inhibitor is lost. It limited to the range of 0.0005-0.0050 mass%.
In addition, since BN precipitates simultaneously with AIN and further enhances the ability to suppress normal grain growth and acts to improve the magnetism, a method of adding both Al and B is also recommended.
[0069]
N: 0.003 to 0.010 mass% (when used in combination with sol. Al: 0.015 to 0.035 mass%)
N: 0.001 to 0.010 mass% (when used in combination with B: 0.0005 to 0.0050 mass%)
N is an element necessary for forming AlN and BN. In order to make AlN function well as an inhibitor, it is necessary to add 0.003 to 0.010 mass%. When the addition amount is less than 0.003 mass%, precipitation of AlN becomes insufficient.
On the other hand, regarding the precipitation of BN, if the amount of N added is less than 0.001 mass%, the precipitation of BN becomes insufficient.
In both cases of AlN and BN, if the amount of N added exceeds 0.010 mass%, blistering or the like occurs during slab heating.
Therefore, the amount of N when adding Al is limited to the range of 0.003 to 0.010 mass%, and the amount of N when adding B is limited to the range of 0.001 to 0.010 mass%.
[0070]
Bi: 0.001 to 0.070 mass%
Bi preferentially concentrates at the grain boundaries of the primary recrystallized grains and lowers the mobility of the grain boundaries during annealing, thereby increasing the secondary recrystallization temperature and improving the magnetic flux density. These effects are similar to Sb, As, etc., but Bi has a particularly low solubility in iron and has a very low melting point of 271 ° C, so it is more segregated at grain boundaries than Sb, As. it is conceivable that. For this reason, it is considered that the effect of imparting a normal grain growth inhibiting force is high, and that it effectively acts to improve the orientation accumulation degree.
In addition, as described above, the secondary recrystallization is appropriately controlled by leaving an appropriate amount in the final finish annealed plate without being completely purified from the steel during the final finish annealing as described above. Secondary recrystallized grain structure can be formed.
However, if the Bi content in the material is less than 0.001 mass%, disappearance from the steel will occur early, so the above effect cannot be obtained. On the other hand, if it exceeds 0.070 mass%, the residual amount in the product steel plate The amount of Bi was limited to the range of 0.001 to 0.070 mass% because of the excessive increase in the hysteresis loss.
[0071]
Cr: 0.05-0.50mass%
When Bi is present in the steel, the formation of the forsterite film is hindered, and thus the film of the product tends to deteriorate. For this reason, an increase in the magnetic domain width due to insufficient tension on the steel sheet surface may offset the iron loss reduction effect by controlling the grain boundary oblique angle.
In this regard, when Cr is added to the steel, formation of a good forsterite film is promoted, and the iron loss reduction effect according to the present invention can be more effectively exhibited. Cr in steel is SiO in decarburized annealed plate surface subscale.₂Even if Bi is present in the final finish annealing atmosphere by changing the form of SiO₂It is considered that the reaction between MgO and MgO is sufficiently promoted. Here, when the amount of Cr in the steel is less than 0.05 mass%, the above effect is not exhibited. On the other hand, when it exceeds 0.50 mass%, the magnetic properties are deteriorated due to the formation of Cr carbide or the like. It limited to the range of 0.05-0.50mass%.
[0072]
  The basic components have been described above., Mo, Cu, Sn, Ge, B, etc., are added alone or in combination in order to further improve the magnetic properties.
  Sb IsLike Bi, it has the effect of segregating at the grain boundaries and increasing the suppression force, 0.It is desirable to add in the range of 001-0.10 mass%.
  Mo has the effect of sharpening the nuclei of secondary grains in the Goth direction, and the effect is remarkable in the range of 0.001 to 0.20 mass%.
  Cu, like Mn, is an element that combines with Se and S to form precipitates and increase the suppressive force, and its effect is remarkable in the range of 0.01 to 0.30 mass%..
  Sn, Ge is a component that effectively acts to reduce iron loss by increasing the frequency of secondary recrystallized grains, and it is preferable that both are contained in the range of 0.005 to 0.20 mass%.
  Also,B isIt has the function of further enhancing the ability to suppress normal grain growth by forming BN precipitates in steel.Because, B is in the range of 0.0010 to 0.010 mass%AtIt is desirable to add.
[0073]
【Example】
Example 1
C: 0.065 mass%, Si: 3.35 mass%, Mn: 0.070 mass%, Al: 0.022 mass%, N: 0.0085 mass%, Sb: 0.030 mass%, Se: 0.020 mass% and Mo: 0.020 mass%, In addition, a silicon steel slab containing 0, 0.001, 0.010, 0.030, 0.070 mass% of Bi and the balance substantially Fe composition is placed in a gas heating furnace and heated to 1230 ° C for 60 minutes. After holding, it was heated at 1400 ° C. for 40 minutes by induction heating, and then hot rolled into a 2.5 mm thick hot-rolled steel sheet. Then, after hot-rolled sheet annealing at 1000 ° C. for 1 minute, pickling and then primary cold rolling to a thickness of 1.6 mm, followed by intermediate annealing at 1000 ° C. for 1 minute, then pickling Then, it was finished to a final thickness of 0.23 mm by secondary cold rolling.
At this time, the surface roughness of the final cold rolled sheet was changed as shown in Table 1 by adjusting the surface roughness of the rolling roll.
[0074]
Next, the oxidation potential P (H₂O) / P (H₂) Decarburization annealing was performed at 850 ° C. for 100 seconds in an atmosphere of 0.50. After that, an annealing separator mainly composed of MgO was applied at various application amounts (weight per unit area) shown in Table 1, and wound up in a coil shape, then the maximum temperature reached: 1200 ° C, 10 hours The final finish annealing was performed.
At this time, in the temperature range of 900 to 1100 ° C. of the final finish annealing, the average heating rate was changed as shown in Table 1.
Next, after removing the unreacted separating agent by washing with water, an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica is applied to each side of the steel plate at 6 g / m 2.²It was applied and baked at a weight per unit area.
The thickness of the nonmagnetic layer (insulating coating + forsterite) on the surface of the product is 2.3μm, and the tension in the rolling direction applied to the steel sheet by these is 8.83 MPa (0.9 kgf / mm)²) (Per one side of the steel plate).
Thereafter, by applying a plasma flame, linear strain was introduced under the conditions of an interval in the rolling direction of 10 mm and an angle between the rolling direction of 80 ° and the magnetic domain.
The Bi content of the product plate thus obtained in the ground iron, the area ratio r of the crystal grains whose maximum length in the direction perpendicular to the rolling is 30 mm or more_Three The area average value <α> of the α angle, the oblique angle <θ>, and the surface roughness of the product plate were investigated.
In addition, an Epstein specimen: 500 g was taken from the product plate, and the magnetic flux density B was measured by the Epstein magnetic test method.₈ And iron loss W_17/50 Was measured.
Furthermore, with this product plate, a model transformer is manufactured and W_17/50 Was measured and compared with the iron loss by the Epstein test. F. Asked.
The obtained results are also shown in Table 1.
[0075]
[Table 1]
[0076]
As is apparent from the table, the product plate iron contains 0.0003 to 0.05 mass% Bi, and the secondary recrystallized grain structure is <α> ≦ 4 °, r_Three Any of the conforming examples that satisfy the conditions of ≧ 70% and <θ> ≦ 25 °_17/50 Is 0.70 W / kg or less and B.I. F. Shows an excellent characteristic value below 1.20. Among them, the symbols 1K, 1M, 1O, and 1P each have an oblique angle <θ> of 20 ° or less, so_17/50 A particularly excellent iron loss of less than 0.63 W / kg could be obtained.
[0077]
Example 2
C: 0.065 mass%, Si: 3.35 mass%, Mn: 0.070 mass%, Cu: 0.15 mass%, Al: 0.020 mass%, N: 0.0085 mass%, S: 0.030 mass% and Sn: 0.10 mass%, In addition, a silicon steel slab containing 0.010 mass% of Bi and the balance being substantially Fe composition was charged into a gas heating furnace, heated to 1230 ° C, held for 30 minutes, and then heated to 1400 ° C by induction heating. , Heated for 40 minutes, and then hot rolled into a 2.5 mm thick hot rolled steel sheet. Next, after hot-rolled sheet annealing at 1000 ° C for 1 minute, pickling, and then performing primary cold rolling to a thickness of 1.7 mm, followed by intermediate annealing at 1000 ° C for 1 minute, and then pickling Secondary cold rolling was performed to a final thickness of 0.23 mm.
Next, the oxidation potential P (H₂O) / P (H₂) = 0.45 Decarburization annealing was performed at 840 ° C. for 160 seconds. After that, MgO is the main component and MgCl₂5g / m of annealing separator with 10mass% added²It was applied at a basis weight (per side).
After that, a final finish annealing was performed for 10 hours at a maximum temperature of 1200 ° C.
At this time, the heating rate was set to 12 ° C./h in the temperature range of 900 to 1100 ° C. The coil width was 1200 mm.
[0078]
After the final finish annealing, the separating agent on the surface of the steel sheet is removed by washing with water, and then electropolished to a mirror state. Further, the grooves perpendicular to the rolling direction are etched, depth: 20 μm, width: 120 μm, spacing: It was formed at 3 mm. The surface roughness (Ra) of the portion other than the groove forming portion was 0.1 μm. Next, as shown in Table 2, after depositing TiN with a film thickness of 0.1 to 2.0 μm on the steel sheet surface, insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied in various basis weights. did.
From the product plate thus obtained, an Epstein specimen: 500 g was collected, and the magnetic flux density B was determined by the Epstein magnetic test method.₈ And iron loss W_17/50 Was measured.
Also, using this product plate, a model transformer is manufactured and W_17/50 Was measured and compared with the iron loss by the Epstein test. F. Asked.
The obtained results are also shown in Table 2.
[0079]
[Table 2]
[0080]
As shown in Table 2, W is a grain-oriented electrical steel sheet that satisfies the requirements of the present invention, and has a mirror finish and groove formation at the same time._17/50 Has a very good iron loss of less than 0.62 W / kg. F. Was as good as 1.20 or less, and peeling of the film did not occur.
[0081]
Example 3
C: 0.070 mass%, Si: 3.30 mass%, Mn: 0.070 mass%, Al: 0.027 mass%, N: 0.0090 mass%, Sb: 0.048 mass%, Se: 0.019 mass%, Cu: 0.12 mass% and Mo: A silicon steel slab containing 0.022 mass% and containing 0.01 mass% Bi with the balance being substantially Fe in composition was charged into a gas heating furnace and heated to 1230 ° C, and held for 60 minutes. It was heated at 1400 ° C for 40 minutes by induction heating, and then hot rolled into a hot rolled steel sheet having a thickness of 2.2 mm. Subsequently, after hot-rolled sheet annealing at 1100 ° C. for 1 minute, it was pickled and finished to a final sheet thickness of 0.27 mm by cold rolling.
Subsequently, the oxidation potential P (H₂O) / P (H₂) = 0.50 Decarburization annealing was performed at 840 ° C. for 100 seconds.
[0082]
Next, MgO is the main component and TiO₂3-10g / m of annealing separator with 6mass% added²Was applied at a weight per unit area (per side), and a final finish annealing was performed at a maximum temperature of 1200 ° C. for 10 hours. At this time, in the temperature range of 900 to 1100 ° C., as shown in Table 3, the heating rate was variously changed in the range of 1 to 20 ° C./h, and the application amount of the annealing separator was 3 to 3 per side of the steel plate. 10g / m²The range was changed. The coil width was 1000 mm. After the final finish annealing, after removing the separating agent on the steel sheet surface with water, apply an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica, and then perform magnetic domain fragmentation treatment with laser light in the rolling direction. The product was formed into a line at a pitch of 6 mm and an angle with the rolling direction: 80 °.
The thickness of the nonmagnetic layer of this product is 2.2 to 3.3 μm, and the tension applied in the rolling direction is 7.85 to 11.77 MPa (0.8 to 1.2 kgf / mm²)Met. Bi content in the ground iron of the product plate thus obtained, r_Three , R₆ , <Α> and <θ> were investigated.
In addition, an Epstein specimen: 500 g was taken from the product plate, and the magnetic flux density B was measured by the Epstein magnetic test method.₈ And iron loss W_17/50 Was measured.
Furthermore, with this product plate, a model transformer is manufactured and W_17/50 Was measured and compared with the iron loss by the Epstein test. F. Asked.
The results obtained are also shown in Table 3.
[0083]
[Table 3]
[0084]
As shown in the table, by using a material with Bi added to steel, the amount of annealing separator applied and the temperature increase rate of final finish annealing are controlled appropriately, so that the ideal two specified in the present invention can be obtained. The next recrystallized structure is obtained and W_17/50 A product with a low iron loss of less than 0.80 W / kg has been obtained.
In particular, the area ratio r of grains whose maximum width in the direction perpendicular to the rolling direction of secondary recrystallized grains exceeds 60 mm.₆ For 3B and 3D that satisfy the conditions of ≧ 70% and <θ> ≦ 20 °,_17/50 A product with extremely good iron loss of ≦ 0.75 W / kg or less is obtained.
[0085]
Example 4
C: 0.074 mass%, Si: 3.40 mass%, Mn: 0.068 mass%, B: 0.0040 mass%, N: 0.0070 mass%, Sb: 0.050 mass%, Se: 0.018 mass%, Cu: 0.10 mass% and Mo: A silicon steel slab containing 0.020 mass% as a basic component and containing 0, 0.030, 0.060 mass% of Bi respectively, and the balance being substantially Fe composition, is charged to a gas heating furnace up to 1230 ° C. After heating and holding for 60 minutes, it was heated at 1400 ° C. for 40 minutes by induction heating, and then hot-rolled to a thickness of 2.2 mm by hot rolling. Next, after pickling, primary cold rolling is performed to a thickness of 1.5 mm, intermediate annealing is performed at 1050 ° C. for 1 minute, pickling, and secondary cold rolling is performed to obtain a 0.22 mm final plate. Finished thick. At this time, the roughness of the work roll was partially changed to change the surface roughness of the cold rolled sheet.
Then, oxidation potential P (H₂O) / P (H₂) = 0.45 Decarburization annealing was performed at 840 ° C. for 160 seconds. Next, after applying an annealing separator mainly composed of MgO, final finishing annealing was performed at a maximum temperature of 1200 ° C. for 10 hours. At this time, the coil width is 1000mm, and the amount of annealing separator applied is 8g / m per side of the steel plate.²The heating rate in the temperature range of 900 to 1100 ° C. was 1 to 40 ° C./h.
[0086]
After the final finish annealing, the annealing separator on the surface of the steel sheet was removed by washing with water, and then an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied to obtain a product. The total thickness of forsterite and insulating coating on the surface of this grain-oriented electrical steel sheet is 3 μm, and the tension applied in the rolling direction is 8.83 MPa (0.9 kgf / mm per side of the steel sheet).²)Met.
Bi content in the ground iron of the product plate thus obtained, r_Three , <Α>, <θ> and the surface roughness of the product plate.
In addition, an Epstein specimen: 500 g was taken from the product plate, and the magnetic flux density B was measured by the Epstein magnetic test method.₈ And iron loss W_17/50 Was measured.
Furthermore, with this product plate, a model transformer is manufactured and W_17/50 Was measured and compared with the iron loss by the Epstein test. F. Asked.
Table 4 shows the obtained results.
[0087]
[Table 4]
[0088]
As is apparent from the table, the ideal secondary recrystallized structure defined in the present invention can be obtained by appropriately controlling the amount of Bi in steel and the temperature increase rate (900 to 1100 ° C) of final finish annealing. , Iron loss W of plain material_17/50 A product with a low iron loss of less than 0.85 W / kg is obtained. F. Was also good at 1.20 or less.
When the oblique angle <θ> is 15 ° C. or less, W_17/50 As a plain material with ≦ 0.80 W / kg, products with extremely low iron loss have been obtained.
[0089]
Example 5
Si: 3.25 mass%, Mn: 0.075 mass%, C: 0.070 mass%, S: 0.005 mass%, sol.Al: 0.025 mass%, N: 0.0080 mass%, Sn: 0.05 mass% and Cu: 0.12 mass% A silicon steel slab containing as basic components and containing 0.02 mass% Bi each, with the balance being essentially Fe composition, is charged into a gas heating furnace and heated to 1230 ° C and held for 60 minutes After that, a hot rolled steel sheet having a thickness of 2.2 mm was obtained by hot rolling. Then, after hot-rolled sheet annealing at 900 ° C for 1 minute, pickling, primary cold rolling to 1.5 mm thickness, intermediate annealing at 1050 ° C for 1 minute, then pickling, Subsequent cold rolling finished to a final thickness of 0.22 mm. At this time, the surface roughness (Ra) of the cold-rolled sheet was set to 0.35 μm. Next, the oxidation potential P (H₂O) / P (H₂) = 0.40, decarburization annealing was performed at 840 ° C. for 160 seconds, followed by nitriding in an ammonia atmosphere to increase the nitrogen amount to 0.020 mass%.
[0090]
Then, after applying an annealing separator mainly composed of MgO, a final finish annealing was performed at a maximum temperature of 1200 ° C. for 10 hours. At this time, the coil width is 1050 mm, and the amount of annealing separator applied is 5 g / m per side of the steel plate.²Or 9g / m²Further, the rate of temperature rise in the temperature range of 900 to 1100 ° C. was 3 ° C./h or 15 ° C./h.
After the final finish annealing, the separating agent on the surface of the steel sheet was removed by washing with water, and then a groove with a depth of 15 μm, a width of 60 μm, a spacing in the rolling direction of 15 mm, and an angle with the rolling direction of 10 ° was formed by a protruding roll. Thereafter, an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied to obtain a product. The total thickness of the forsterite and insulating coating on the surface of the grain-oriented electrical steel sheet thus obtained is 3 μm, and the tension applied in the rolling direction of the steel sheet is 9.02 MPa (0.92 kgf / mm²)Met.
Bi content in the ground iron of the product plate thus obtained, r_Three , <Α>, <θ> and the surface roughness of the product plate.
In addition, an Epstein specimen: 500 g was taken from the product plate, and the magnetic flux density B was measured by the Epstein magnetic test method.₈ And iron loss W_17/50 Was measured.
Furthermore, with this product plate, a model transformer is manufactured and W_17/50 Was measured and compared with the iron loss by the Epstein test. F. Asked.
The results obtained are shown in Table 5.
[0091]
[Table 5]
[0092]
As shown in the same table, the ideal secondary specified in the present invention is achieved by appropriately controlling the amount of Bi in steel, the amount of annealing separator applied, and the temperature increase rate (900 to 1100 ° C) of final finish annealing. A recrystallized structure is obtained and W_17/50 A product with a low iron loss of less than 0.70 W / kg is obtained. F. Was also good at 1.20 or less. Also, if the oblique angle <θ> is 15 ° or less, W_17/50 A product with extremely low iron loss of ≤ 0.62 W / kg has been obtained.
[0093]
Example 6
C: 0.070 mass%, Si: 3.3 mass%, Mn: 0.075 mass%, Al: 0.025 mass%, N: 0.0090 mass%, S: 0.0012 mass%, Cu: 0.07 mass%, Sn: 0.070 mass% and Bi: A silicon steel slab containing 0.070 mass% and containing Cr of 0, 0.02, 0.05, 0.20, 0.50, 0.70 mass%, with the balance being substantially Fe, was charged into a gas heating furnace. After heating to 1230 ° C, it was heated to 1400 ° C for 30 minutes in an induction heating furnace, and then hot rolled into a hot rolled steel sheet having a thickness of 2.2 mm. Next, after hot-rolled sheet annealing at 900 ° C for 1 minute, pickling and then primary cold rolling to a thickness of 1.4 mm, followed by intermediate annealing at 1100 ° C for 1 minute, then pickling Thereafter, a final cold rolled sheet having a sheet thickness of 0.23 mm and a surface roughness (Ra) of 0.36 μm was obtained by secondary cold rolling.
Next, the oxidation potential P (H₂O) / P (H₂) = 0.55 Decarburization annealing was performed at 820 ° C. for 150 seconds.
[0094]
After that, an annealing separator containing MgO as the main component is 6 g / m2²After coating and winding in a coil shape, the final finish annealing was performed under the conditions of maximum temperature reached: 1200 ° C., 10 hours, average temperature rising rate in the temperature range of 900 to 1100 ° C .: 13 ° C./h. The coil width during final finish annealing was 1150 mm.
Next, after removing the unreacted separating agent by washing with water, an insulating tension coating mainly composed of magnesium phosphate containing colloidal silica was applied to each side of the steel sheet at 5.5 g / m 2.²The coating weight was baked at 850 ° C. The applied tension in the rolling direction at this time is 2.94 to 14.7 MPa (0.3 to 1.5 kgf / mm²)Met.
Then, the magnetic domain refinement process was performed by introducing linear strain at an interval of 10 mm in the rolling direction and an angle of 10 ° with the rolling direction by plasma flame irradiation. The surface roughness (Ra) of the product thus obtained was 0.28 μm.
Bi content in the ground iron of the product plate thus obtained, r_Three , <Α>, <θ>, the thickness of the nonmagnetic layer, the tension applied to the steel plate, and the coating appearance.
In addition, an Epstein specimen: 500 g was taken from the product plate, and the magnetic flux density B was measured by the Epstein magnetic test method.₈ And iron loss W_17/50 Was measured.
Furthermore, with this product plate, a model transformer is manufactured and W_17/50 Was measured and compared with the iron loss by the Epstein test. F. Asked.
The results obtained are shown in Table 6.
[0095]
[Table 6]
[0096]
As shown in the table, by including 0.05 to 0.50 mass% of Cr in the product plate base iron, the coating properties, iron loss and B.I. F. Further improvement has been achieved.
[0097]
【The invention's effect】
Thus, according to the present invention, it goes without saying that the magnetic properties of the material are excellent, and it is possible to stably obtain a grain-oriented electrical steel sheet with low iron loss even when applied to an actual machine, and its industrial contribution is Very large.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between an area average value (<α>) of a deviation angle (α angle) from a rolling direction in a rolling plane having a crystal orientation [001] and iron loss.
[Fig. 2] Area ratio of crystal grains with maximum length in the direction perpendicular to rolling of 30 mm or more (r_Three ) And iron loss W_17/50 It is the graph which showed the relationship.
FIG. 3 is an explanatory diagram of a method for deriving a grain boundary component.
FIG. 4 is an explanatory diagram of a specific procedure for deriving a grain boundary component.
FIG. 5 Grain boundary oblique angle <θ> and iron loss W_17/50 It is the graph which showed this relationship.
FIG. 6 is an explanatory diagram of non-uniform magnetic flux density distribution accompanying an increase in α angle.
FIG. 7 is an explanatory diagram of non-uniform magnetic flux density distribution accompanying a decrease in length in the direction perpendicular to rolling.
FIG. 8 is an explanatory diagram of non-uniform magnetic flux density distribution accompanying an increase in grain boundary oblique angle <θ>.
FIG. 9 is a graph showing the relationship between the amount of Bi added in the material and the appearance frequency of ideal secondary recrystallized grains.
FIG. 10 is a graph showing the relationship between the Bi addition amount in the material and the Bi residual amount in the product plate iron and the ideal occurrence frequency of secondary recrystallized grains.
FIG. 11 is a graph showing the relationship between the coating amount of the annealing separator and the rate of temperature rise in the temperature range of 900 to 1100 ° C. during the final finish annealing and the amount of Bi remaining in the product sheet iron.
FIG. 12 shows the nonmagnetic layer thickness and surface roughness and F. It is the graph which showed the relationship.
FIG. 13 is a diagram showing a preferred method for measuring the maximum length of secondary recrystallized grains in the direction perpendicular to the rolling direction.

Claims (15)

The steel is a grain-oriented electrical steel sheet containing Si: 2.0 to 5.0 mass%, Mn: 0.04 to 0.15 mass% and Bi: 0.0003 to 0.05 mass%, the balance being a composition of Fe and inevitable impurities, The area average value of the deviation angle from the rolling direction in the rolling plane of the crystal orientation [001] of the secondary recrystallized grains excluding the crystal grains having an equivalent circle diameter of 5 mm or less is 4 ° or less, and the maximum length in the direction perpendicular to the rolling is The grain boundary line segment L _i that approximates the grain boundary of the secondary recrystallized grains excluding the crystal grains whose secondary recrystallized grains of 30 mm or more occupy the entire steel sheet have a ratio of 70% or more and the equivalent circle diameter of 5 mm or less. The angle θ _i between the rolling direction of the steel sheet and the direction orthogonal to the rolling direction and the length l _i of the grain boundary line segment L _i , and the oblique angle <θ> calculated by the following formula is 25 ° or less, and the steel plate Thickness: 6 μm or less, surface roughness (Ra): 0.4 μm or less, tension applied in the rolling direction of the steel sheet: 4.9 to 39.3 MPa (0.5 to 4.0 kgf / mm ² ) A grain-oriented electrical steel sheet characterized by having a single or composite non-magnetic coating satisfying (per one steel sheet surface).
Record
  The grain-oriented electrical steel sheet according to claim 1, further comprising Cr: 0.05 to 0.5 mass% in the steel. In steel, Sb: 0.001 to 0.10 mass% , Mo : 0.001 to 0.20 mass%, Cu: 0.01 to 0.30 mass% , Sn : 0.005 to 0.20 mass%, Ge: 0.005 to 0.20 mass% , and B: 0.0010 to The grain-oriented electrical steel sheet according to claim 1 or 2, wherein one or more selected from 0.010 mass % are contained.   On one or both sides of the steel sheet, a linear or linear groove having a depth of 2 to 15% of the plate thickness, a width of 30 to 300 μm, a distance of 2 to 50 mm, and an angle of 60 to 90 ° with the rolling direction The grain-oriented electrical steel sheet according to claim 1, 2 or 3.   4. A directional electromagnetic wave according to claim 1, 2 or 3, characterized in that the surface of the steel plate has a linear region or a strain region continuous in a linear shape with an interval of 2 to 50 mm and an angle with the rolling direction of 60 to 90 °. steel sheet.   The grain-oriented electrical steel sheet according to any one of claims 1 to 5, wherein a forsterite film is not present on the surface of the steel sheet. C: 0.03-0.10 mass%,
Si: 2.0-5.0 mass%,
Mn: 0.04-0.15 mass%
One or two selected from S and Se: 0.005 to 0.040 mass%,
sol.Al: 0.015-0.035 mass% and N: 0.003-0.010 mass% and / or B: 0.0005-0.0050 mass% and N: 0.001-0.010 mass%
And including
Bi: 0.001 to 0.070 mass%
Containing a silicon-Motoko slab balance consisting Fe and inevitable impurities, was heated, then hot rolled, then it was finished to a final thickness by combining the annealing and cold rolling, decarburization In the method for producing grain-oriented electrical steel sheets comprising a series of steps of performing annealing and then performing final final finishing annealing,
The surface roughness (Ra) of the final cold-rolled sheet is 0.5 μm or less, the width of the steel strip during final finish annealing is 800 mm or more, and the Bi content in the slab is c ₀ (mass%). When the Bi content in the steel is c ₁ (mass%), the steel plate surface before final finish annealing so that c ₁ falls within the range satisfying the conditions of the following formulas (1), (2), (3) A method for producing a grain-oriented electrical steel sheet, characterized by determining an application amount of an annealing separator to be applied to the substrate and a rate of temperature rise in a temperature range of 900 to 1100 ° C. during final finish annealing.
Record
c ₁ ≦ 0.85c ₀ --- (1)
c ₁ ≧ 0.36c ₀ −0.0072 --- (2)
0.05 ≧ c ₁ ≧ 0.0003 --- (3) C: 0.03-0.10 mass%,
Si: 2.0-5.0 mass%,
Mn: 0.04-0.15 mass%
One or two selected from S and Se: 0.005 to 0.040 mass%,
sol.Al: 0.015-0.035 mass% and N: 0.003-0.010 mass% and / or B: 0.0005-0.0050 mass% and N: 0.001-0.010 mass%
And including
Bi: 0.001 to 0.070 mass%
Contains, after the balance was finished silicon-Motoko slab consisting Fe and inevitable impurities, after heating, hot rolling, and then to the final thickness by combining the annealing and cold rolling, decarburization annealing In the method for producing a grain-oriented electrical steel sheet consisting of a series of steps, followed by final final annealing.
The surface roughness (Ra) of the final cold-rolled sheet is 0.5 μm or less, the width of the steel strip during final finish annealing is 800 mm or more, and the amount of annealing separator applied to the steel sheet surface before final finish annealing is 2-9g / m ² per side, and the rate of temperature rise in the temperature range of 900 to 1100 ° C during final finish annealing should be controlled within the range satisfying the conditions of the following formulas (4), (5), (6) A method for producing a grain-oriented electrical steel sheet.
Record
v ≦ 3σ + 5 --- (4)
v ≧ 3σ−21 --- (5)
v ≧ 2 --- (6)
Where, v: temperature rising rate of 900-1100 ° C. (° C./h)
σ: Amount of separating agent applied to one side of steel sheet (g / m ² )   The method for producing a grain-oriented electrical steel sheet according to claim 7 or 8, further comprising Cr: 0.05 to 0.5 mass% in the slab. During the slab, Sb : 0.001 ~ 0.10mass %, Mo : 0.001 ~ 0.20 mass %, Cu : 0.01 ~ 0.30mass %, Sn : 0.005 ~ 0.20mass %, Ge : 0.005 ~ 0.20mass % And B: 0.0010 ~ 0.010mass 10. The method for producing grain-oriented electrical steel sheets according to claim 7, 8 or 9, comprising one or more selected from the group consisting of 1% and 2%. The total amount of S and Se in the slab than 0.02 mass%, and after the final cold rolling according to any one of claims 7-10, characterized in that the nitriding process and before the secondary recrystallization ends A method for producing grain-oriented electrical steel sheets. After the final cold rolling, on the surface of the steel sheet, a line or wire having a depth of 2 to 15% of the plate thickness, a width of 30 to 300 μm, an interval of 2 to 50 mm, and an angle with the rolling direction of 60 to 90 ° method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 11, characterized in that a groove connecting to Jo. Since final annealing, according to any of claims 7-11 the interval 2 to 50 mm, angle between the rolling direction and forming a strain region continuous with the 60 to 90 ° linear or linear Method for producing a grain-oriented electrical steel sheet. The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 13 , wherein after the final finish annealing, the oxide on the surface is removed and the ground iron surface is mirror-finished, and then a tension coating is formed. . The method for producing a grain-oriented electrical steel sheet according to any one of claims 7 to 14 , wherein the final finish annealing is performed using an annealing separator that does not form forsterite on the steel sheet surface or inhibits the formation.