JP6524438B2 - Hot-rolled sheet for non-oriented electrical steel sheet, method for producing the same, non-oriented electrical steel sheet having excellent magnetic properties, and method for producing the same - Google Patents

Description

  The present invention simultaneously demands high energy efficiency and small size and high power, such as drive motors mounted on hybrid vehicles, electric vehicles and fuel cell vehicles, and small generators mounted on two-wheeled vehicles and household cogeneration systems. TECHNICAL FIELD The present invention relates to a non-oriented electrical steel sheet suitable for a core material of an electric device and a method of manufacturing the same. The present invention further relates to a hot rolled sheet for non-oriented electrical steel sheet used for non-oriented electrical steel sheet and a method of manufacturing the same.

  High-efficiency motors require non-oriented electrical steel sheets that have both low iron loss and high magnetic flux density. In recent years, the demand for a high efficiency motor has been increasing, and in particular, the demand for a non-oriented electrical steel sheet having both a low iron loss and a high magnetic flux density in a high frequency region tends to be strong. As a means for reducing iron loss in the high frequency region of the non-oriented electrical steel sheet, there is a high specific resistance by the addition of alloy elements such as Si and Al, but the magnetic flux density tends to decrease. In order to improve the magnetic flux density, there are known a technology that utilizes cold rolling interpass aging by solid solution C, and a technology that performs hot rolled sheet annealing in a batch annealing furnace on a high P material and utilizes grain boundary segregation of P. ing. For example, in Patent Document 1, a high magnetic flux density in the rolling direction is obtained by leaving solid solution C by performing an aging treatment at a temperature of 50 to 300 ° C. for 1 to 10 minutes between two or more cold rolling passes. A method of manufacturing a non-oriented electrical steel sheet having the Further, for example, Patent Document 2 discloses a method of improving the texture after cold rolling by segregating P at grain boundaries of a steel sheet before cold rolling to produce a non-oriented electrical steel sheet having a high magnetic flux density. ing.

JP 2011-256426 A JP 2005-200756 A

  The present inventors examined simultaneously utilizing the technology of improving the magnetic flux density by utilizing grain boundary segregation of P and the technology of improving the magnetic flux density by utilizing solid solution C by cold rolling interpass aging. .

  And, at the beginning of the study, I recognized that this combination had the following problems. That is, if P is segregated in grain boundaries during cold rolling with a high P material, the magnetic flux density after cold rolling annealing improves, but to segregate P into grain boundaries before cold rolling, after hot rolling Or it is necessary to make the cooling rate after hot-rolling annealing slow. However, if the cooling rate after the hot rolling annealing is low, solid solution C in the steel can not be obtained, and the improvement of the magnetic flux density due to the aging treatment between the cold rolling passes can not be achieved. In addition, high P material which segregates P in grain boundaries has a concern that cold ductility is originally reduced, but cold ductility is further lowered because cold rolling interpass aging hardens the steel sheet, and after hot rolling annealing When the cooling rate is low, cementite is formed at grain boundaries, and the cold ductility is significantly reduced.

  On the other hand, in order to cause solid solution C to remain in the hot-rolled sheet, it is necessary to increase the cooling speed after hot-rolled sheet annealing. However, if the cooling rate after hot-rolling annealing is high, improvement in the magnetic flux density due to grain boundary segregation of P can not be achieved. Thus, in addition to the control direction of the cooling rate to the hot-rolled sheet being reversed, the cold ductility is lowered by the respective actions of C and P, and the plate breakage is feared, so the cold by the solid solution C In order to simultaneously utilize rolling interpass aging and P segregation, it was necessary to develop new technology especially for cooling in hot rolled sheet and element segregation there.

  The present invention has been made in view of the above point, and it is a non-oriented electrical steel sheet having excellent magnetic properties by achieving both improvement of magnetic flux density by grain boundary segregation of P and improvement of magnetic flux density by solid solution C. The purpose is to get.

  As described above, grain boundary segregation of P and solid solution C (aging between cold rolling paths) are both effective in improving the texture, but it is necessary to slow the cooling by hot rolling to be slow cooling and to rapidly cool, respectively. Yes, both are difficult. In addition, cold ductility is reduced in both cases, which inhibits simultaneous utilization. In the present invention, noting that the temperature at which P segregates at grain boundaries and the temperature at which C segregates at grain boundaries (temperature at which solid solution C decreases) is different, each temperature range is controlled separately. As a result, a proper grain boundary P which secures both the improvement of the texture and the cold ductility reduction avoidance is secured, and further, the grain boundary P suppresses the grain boundary segregation of C (site competition), and as a result, the solid solution C also efficiently It will be secured. The gist of the present invention is as follows.

[1]
In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
And the balance consists of Fe and impurity elements,
A hot rolled sheet for a non-oriented electrical steel sheet, wherein the solid solution C concentration is 0.001 mass% or more and 0.005 mass% or less, and the P / Fe atomic ratio at the grain boundaries is 0.01 or more and 0.05 or less.

[2]
The hot rolled sheet for non-oriented electrical steel sheet according to [1], wherein the surface Vickers hardness H of the steel sheet and the Charpy transition temperature T (° C.) satisfy the following formula (1).
T (° C.) ≦ 4.5 × (225−H) ··· Formula (1)

[3]
In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
And the balance consists of Fe and impurity elements,
{200} plane ratio I ₂₀₀ / I ₂₂₂ of the X-ray integrated intensity I ₂₂₂ of the X-ray integrated intensity I ₂₀₀ {222} plane of is not less 1.00 or more,
The strength of {φ ₁ , ,, φ ₂ } = {25 °, 0 °, 45 °} in the crystal orientation distribution function is 6.00 or more, and {φ ₁ , ,, φ ₂ } = {30 °, 55 Satisfy the strength of less than 5.00 °, 45 °},
Satisfy the strength of {φ ₁ , ₂ , φ ₂ } = {25 °, 0 °, 45 °} ≧ {φ ₁ , ,, φ ₂ } = {20 °, 20 °, 45 °},
A non-oriented electrical steel sheet having a crystal grain size of 30 μm or more and a plate thickness of 0.10 mm or more and 0.50 mm or less.

[4]
It is a method of manufacturing the hot-rolled sheet for non-oriented electrical steel sheets according to [1] or [2],
In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
After hot-rolling and annealing a steel piece containing the balance of Fe and an impurity element, and then cooling the temperature range of 500 ° C. or more at a cooling rate of 10 ° C./s or more and 100 ° C./s or less, The manufacturing method of the hot-rolled sheet for non-oriented electrical steel sheets which cools a temperature range less than 500 ° C with a cooling rate larger than a cooling rate in a temperature range 500 ° C or more.

[5]
It is a method of manufacturing the hot-rolled sheet for non-oriented electrical steel sheets according to [1] or [2],
In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
Is hot rolled and the coil is wound at 700 ° C. or higher, and the temperature range of 500 ° C. or higher is cooled by 10 ° C./s or more and 100 ° C./s or less A method for producing a hot rolled sheet for non-oriented electrical steel sheet, comprising: cooling at a speed and cooling a temperature range of less than 500 ° C. at a cooling rate greater than a cooling rate in a temperature range of 500 ° C. or more.

[6]
A method of cold rolling the hot rolled sheet for non-oriented electrical steel sheet according to [1] or [2] and finish annealing to produce the non-oriented electrical steel sheet according to [3] ,
A method of manufacturing a non-oriented electrical steel sheet, wherein the cold rolling is multipass rolling with a total rolling reduction of 75% to 95%, and an aging treatment is performed at 100 ° C to 400 ° C for 1 to 60 minutes between each pass. .

[7]
Performing decarburization annealing after the cold rolling, after the, performing the final annealing method for producing a non-oriented electrical steel sheet according to [6].

  According to the present invention, it is possible to obtain a non-oriented electrical steel sheet having excellent magnetic properties by making the improvement of the magnetic flux density by grain boundary segregation of P and the improvement of the magnetic flux density by solid solution C compatible.

5 is an explanatory view of cold rolling in Experiment 1. FIG. FIG. 6 is an explanatory view of the influence of inter-pass aging on the magnetic flux density in Experiment 1; (The numbers at the top of the plot show the improvement from cold rolled material.) It is explanatory drawing of crystal orientation intensity | strength which shows the influence ((phi) ₂ = 45 degree) of the inter-pass aging on the texture after finish annealing in Experiment 1, (a) is a case of aging omission and (b) aging implementation. . 5 is an explanatory view of cold rolling in Experiment 2. FIG. It is explanatory drawing of the influence of the total cold rolling rate and aging which affect the magnetic flux density in experiment 2, (a) 0 degree from the rolling direction, (b) 22.5 degrees from the rolling direction, (c) 45 degrees from the rolling direction (d A) 67.5 ° from the rolling direction, (e) 90 ° from the rolling direction. It is explanatory drawing of the cold rolling in a reference example. It is an explanatory view of the influence (aging 2.0Si-0.2Mn-0.3Al base) on the magnetic flux density in a reference example, and (a) board thickness 0.25mm (total cold rolling ratio: 87.5% equivalent), (b) It is board thickness 0.20 mm (total cold rolling rate: 90.0% equivalent). The effect of aging and P on the magnetic flux density in the reference example (based on 2.5Si-0.2Mn-1.0Al), (a) plate thickness 0.25 mm (total cold rolling ratio: equivalent to 87.5%), (b) plate thickness 0.20 It is mm (total cold rolling rate: 90.0% equivalent).

  Hereinafter, the present invention will be described in detail. The hot-rolled sheet for non-oriented electrical steel sheets and the non-oriented electromagnetic sheet of the present invention have the following component composition. In addition, "%" is "mass%" about the component composition of steel.

2.0% ≦ Si ≦ 4.0%
Si increases the specific resistance of steel and also has the effect of reducing core loss. In order to obtain this effect, 2.0% or more is required. On the other hand, if Si exceeds 4.0%, the steel becomes brittle and the rollability is reduced. Therefore, Si is set to 2.0 to 4.0%. Preferably, it is 2.0 to 3.5%.

0.01% ≦ Al ≦ 3.0%
Al is effective as a deoxidizing material, and further, the nitride can be coarsened to be harmless. Also, like Si, it increases the specific resistance of steel and reduces iron loss. In order to obtain these effects, 0.01% or more is required. However, if it exceeds 3.0%, the steel becomes brittle and the rollability decreases. Therefore, Al is made 0.01 to 3.0%. Preferably, it is 0.2 to 2.0%.

0.05% ≦ Mn ≦ 2.5%
Mn increases the specific resistance of steel and also has the effect of coarsening sulfides to render them harmless. In order to obtain this effect, 0.05% or more is required. On the other hand, if Mn exceeds 2.5%, the magnetic flux density is lowered and the cost is increased, and also it is easily broken at the time of cold rolling. Therefore, Mn is made 0.05 to 2.5%. Preferably, it is 0.1 to 0.5%.

0.03% ≦ P ≦ 0.12%
P has the effect of improving the magnetic flux density. In order to obtain a high magnetic flux density effect, the P content is made 0.03% or more. On the other hand, if the P content exceeds 0.12%, breakage may occur during cold rolling. Therefore, the P content is set to 0.03 to 0.12%.

0.001% ≦ C ≦ 0.005%,
C improves the magnetic flux density by being present as solid solution C in the steel and developing a texture improvement effect by aging between passes during cold rolling. In order to obtain the effect, C is made 0.001% or more. On the other hand, if the content exceeds 0.005%, fine carbides precipitate and the magnetic properties deteriorate, so the C content is made 0.005% or less. Preferably, it is 0.002 to 0.005% by mass.

  The balance is Fe and impurities. Among the impurities, S and N form precipitates, prevent grain growth during annealing, and deteriorate magnetism. Therefore, the content of any of the elements is made 0.005% or less.

  The hot-rolled sheet for non-oriented electrical steel sheets of the present invention has the above component composition, the solid solution C concentration is 0.001 mass% or more and 0.005 mass% or less, and the P / Fe atomic ratio in grain boundaries is 0.01. The above is 0.05 or less.

When the solid solution C concentration is 0.001 mass% or more and 0.005 mass% or less and the solid solution C concentration is less than 0.001 mass%, the improvement of the magnetic flux density by the solid solution C is insufficient. On the other hand, if it exceeds 0.005 mass%, cementite will form at grain boundaries and cold ductility will decrease. In addition, there is a possibility of phase transformation, and when phase transformation is performed in the hot-rolled sheet annealing process, the {111} <uvw> orientation develops significantly more than in the case where phase transformation is not performed in the cold rolling process. } <uvw> orientation increases. It is desirable not to develop this orientation because it degrades the magnetic properties. The amount of solid solution C may be determined from the relationship between the following formulas (2) and (3) by measuring the snake peak value Qmax- ¹ of various samples before and after aging by the internal friction method.
Solid solution C amount (mass%) = K × Qmax ^-1 · · · Formula (2)
K = 1.55 × {Mn amount (mass%)} ^1/2 + 1.35 ・ ・ ・ Formula (3)

When the P / Fe atomic ratio at grain boundaries is 0.01 or more and 0.05 or less The P / Fe atomic ratio at grain boundaries is less than 0.01, the improvement in magnetic flux density utilizing grain boundary segregation of P is insufficient. On the other hand, if it exceeds 0.05, breakage may occur during cold rolling. A sample with a P / Fe atomic ratio of 2.0 mmt × 20 mm L × 3 mmW was placed in an Auger electron spectrometer, the sample was cooled with liquid nitrogen, and the sample was broken. The fractured surface of the sample with intergranular fracture should be found, the amount of Fe and P at the grain interface should be analyzed, and the P / Fe atomic ratio should be determined.

Moreover, as for the hot-rolled sheet for non-oriented electrical steel sheets of this invention, it is desirable for the surface Vickers hardness H of a steel sheet and Charpy transition temperature T (degreeC) to satisfy following formula (1).
T (° C.) ≦ 4.5 × (225−H) ··· Formula (1)
The present invention is characterized by utilizing P and solid solution C in order to improve the magnetic flux density in a steel grade containing relatively high concentrations of Si and Al in order to increase the specific resistance as described above, and combining the rollability Solve the problem. The content of these elements needs to be appropriately designed in consideration of the solid solution strengthening of these elements and the hardening of the steel sheet by cementite. In the present invention, this hardening can be represented by the surface Vickers hardness H of the steel sheet, and the invention can be preferably limited in relation to the Charpy transition temperature T (° C.) related to the rollability, and the above formula (1) is satisfied. In this case, a good balance of magnetic properties and rollability can be obtained.

  Further, the non-oriented electromagnetic plate of the present invention has the above component composition, the X-ray integral intensity of the {200} plane is 2.0 or more, the X-ray integral intensity of the {222} plane is 10.0 or less, The diameter is 30 μm or more, and the plate thickness is 0.10 mm or more and 0.50 mm or less.

X-ray integral intensity of {200} plane is 2.0 or more, X-ray integral intensity of {222} plane is 10.0 or less
The more the X-ray integral intensity of the {200} plane is, the more favorable the texture is to the magnetic characteristics. Therefore, the X-ray integral intensity of the {200} plane is 2.0 or more. On the other hand, as the X-ray integral intensity of the {222} plane increases, the texture becomes less desirable for the magnetic characteristics, so the X-ray integral intensity of the {222} plane is 10.0 or less. In the sample preparation method, a steel plate may be cut out and the thickness of the sample surface may be reduced to a plate thickness to be measured by chemical polishing. Moreover, the quantification method measures the pole figure of the {200}, {110}, {211} plane with the X-ray diffractometer for the prepared sample, and after creating the ODF, the {200} plane, {222 Find the integral intensity of the surface. If the variation in texture in the thickness direction is large, for example, textures of portions at positions 1/10 and 1/4 from the thickness surface may be measured, and the results may be averaged.

If the crystal grain size is 30 μm or more and the crystal grain size is less than 30 μm, good magnetic properties can not be obtained. Therefore, the crystal grain size is 30 μm or more. As a method, the metal structure in the cross section in the longitudinal direction and the thickness direction may be photographed at about 50 times and measured by the line segment method.

The board thickness is 0.10 mm or more and 0.50 mm or less Iron loss is reduced by thinning the board thickness. Therefore, from the viewpoint of achieving both low iron loss and high magnetic flux density, the plate thickness is 0.10 to 0.50 mm.

  Next, the manufacturing method will be described.

  In the present invention, the steel having the component composition described above is used as a steel slab (slab) by a general method such as a continuous casting method or a method of segmenting a steel ingot and hot rolling is performed. Although the slab heating temperature in the case of hot rolling is not specifically limited, It is preferable to set it as 1000-1300 degreeC from a viewpoint of cost and hot-rolling property. More preferably, it is 1050 to 1250 ° C. In addition, various conditions of hot rolling are not particularly limited when performing hot-rolled sheet annealing, and for example, according to general conditions such as a finishing temperature of 700 to 950 ° C. and a winding temperature of 750 ° C. or less You can do it.

  After hot rolling, either hot-rolled sheet annealing may be performed or hot-rolled sheet annealing may not be performed. When hot-rolled sheet annealing is performed, the hot-rolled sheet annealing is performed, for example, by continuous annealing held at 950 ° C. or more and 1050 ° C. or less for 10 seconds or more and 3 minutes or less. When the hot-rolled sheet annealing temperature exceeds the above range, the load on the equipment becomes large, and when the hot-rolled sheet annealing time exceeds the above range, the productivity is deteriorated. When the hot-rolled sheet annealing temperature and the hot-rolled sheet annealing time are below the above range, the effect of improving the magnetic characteristics is reduced.

  Then, after hot-rolled sheet annealing, the temperature range of 500 ° C. or more is cooled at a cooling rate of 10 ° C./s to 100 ° C./s, and the temperature range of less than 500 ° C. is a cooling rate at a temperature range of 500 ° C. or more Cooling is performed at a higher cooling rate to produce a hot-rolled sheet for non-oriented electrical steel sheet.

  On the other hand, when hot-rolled sheet annealing is not performed, after hot rolling and winding at 700 ° C. or more, a temperature range of 500 ° C. or more is performed at a cooling rate of 10 ° C./s or more and 100 ° C./s or less It cools and cools the temperature range less than 500 degreeC with the cooling rate larger than the cooling rate in the temperature range 500 degreeC or more, and manufactures a hot-rolled sheet for non-oriented electrical steel sheets. The winding temperature is desirably 750 ° C. or higher.

  In the present invention, noting that the temperature at which P segregates at grain boundaries and the temperature at which C segregates at grain boundaries (temperature at which solid solution C decreases) differs, the cooling rate in the temperature range effective for each element is separately determined. Control. Thereby, appropriate grain boundary segregation of P is secured, and at the same time as obtaining the texture improvement effect by P segregation, the decrease in cold ductility is avoided. At the same time, since P occupies grain boundaries, C is less likely to segregate at the grain boundaries (site competition), and as a result, securing of solid solution C can also be achieved.

  Since the grain boundary segregation of P is made not to cold-roll fracture and the magnetic flux density is improved by P segregation, in the cooling process after hot rolling and annealing, the cooling rate at 500 ° C. or more is 10 ° C./s or more, The temperature is set to 100 ° C./s or less. It is preferably 80 ° C./s or less, more preferably 50 ° C./s or less. The reason for setting the temperature to 10 ° C./s or more is to suppress breakage due to P segregation during cold rolling. The reason for setting the temperature to 100 ° C./s or less is to obtain an effect of improving the magnetic flux density by P segregation.

  Furthermore, in order to exert the interpass aging effect by solid solution C sufficiently, in the cooling process after hot rolling and annealing, the cooling rate at less than 500 ° C. is made larger than the cooling rate in the temperature range of 500 ° C. or more. C is sufficiently dissolved in the grains. A large amount of C solid-solved in the grains is fixed to the dislocation to aim at the improvement of the magnetic flux density. From these viewpoints, the cooling rate at 500 ° C. or less is 20 ° C./s or more, preferably 50 ° C./s or more, more preferably 100 ° C./s or more.

  Furthermore, in the present invention, the hot rolled sheet for non-oriented electrical steel sheet manufactured as described above is subjected to cold rolling for two or more passes across the aging treatment, and then finish annealing is performed to produce a non-oriented electrical steel sheet. Do. Also, in this way, the non-oriented electrical steel sheet may be subjected to an insulating film treatment, if necessary. Here, cold rolling is multi-pass rolling with a total rolling reduction of 75% or more and 95% or less, and an aging treatment at 100 ° C. to 400 ° C. for 1 to 60 minutes is performed between the respective passes.

Multipass rolling with a total rolling reduction of 75% or more and 95% or less By performing two or more passes of cold rolling sandwiching the aging treatment, a magnetic flux density higher than in the case of one cold rolling can be obtained. The total rolling reduction is determined from manufacturing constraints. For example, when the hot-rolled sheet thickness is 2.0 mm, the rolling reduction is 75% or more and 95% or less in order to obtain 0.10 mm or more and 0.50 mm or less which is the thickness retention of the non-oriented electrical steel sheet.

Aging treatment for 1 to 60 minutes at 100 ° C to 400 ° C between each pass Non-direction having high magnetic flux density in the rolling direction by performing aging treatment for 1 to 60 minutes at 100 to 400 ° C between cold rolling passes Magnetic steel sheet can be manufactured. The aging treatment conditions are preferably 100 to 300 ° C. for 1 to 60 minutes, more preferably 100 to 250 ° C. for 1 to 60 minutes, and still more preferably 150 to 250 ° C. for 1 to 60 minutes. The temperature was set to 100 ° C. to 400 ° C. from the viewpoint of satisfying both that C can diffuse and dislocations are difficult to diffuse. The time was set to 1 to 60 minutes to gain the frequency at which C fixed dislocations. The upper limit of time (60 min) is the upper limit from the viewpoint of productivity.

  In addition, after cold rolling, decarburization annealing may be performed to eliminate solid solution C, and further, finish annealing may be performed. This is because the iron core temperature may rise to 150 ° C. to 200 ° C. during actual operation of the electric device if there is a certain amount or more of carbon in the steel plate, so the magnetic characteristics of the iron core are due to the aging effect The purpose is to prevent the problem of deterioration. The conditions may be normal operating conditions.

  Hereinafter, the present invention will be specifically described by way of examples.

[Experiment 1]
An actual hot-rolled sheet (sheet thickness 1.8 mm) of Si: 2.95%, Mn: 0.2%, Al: 0.5% by mass% was subjected to hot-rolled sheet annealing which is maintained at 1000 ° C. for 1 min. Thereafter, finish annealing was performed soaking at 1000 ° C. for 30 seconds, and strain removing annealing performed soaking at 750 ° C. for 2 hours was performed. A 55 mm square magnetometry test was taken to measure the magnetic flux density B50 at 5000 A / m in the L and C directions.

  Here, the rolling process will be described. After interpass aging was carried out for 5 minutes at 200 ° C when various plate thicknesses (1.8, 1.6, 1.2, 0.8, 0.5 mm) were obtained during cold rolling, it was water cooled and cold rolled at room temperature (Fig. 1). .

Aging improves the flux density in the L and C directions (FIG. 2). This mechanism, in the texture after finish annealing, {111} <112> orientation _{({φ 1, Φ, φ} 2} = {30 °, 55 °, 45 °}) reduction and {100} of the <012> Due to the increase in the azimuthal neighborhood ({φ ₁ , ,, φ ₂ } = {20-25 °, 0 °, 45 °}) (FIG. 3).

[Experiment 2]
A vacuum-melt steel of 2.95% Si, 2. 9% Mn, 0.2% Al and 0.5% Al by mass% was produced in a laboratory by vacuum to prepare a hot-rolled sheet with a thickness of 2.0 mm, which was subjected to 1 minute soaking at 1000 ° C. It was rolled and annealed. Thereafter, finish annealing was performed soaking at 1000 ° C. for 30 seconds, and strain removing annealing performed soaking at 750 ° C. for 2 hours was performed. A 55 mm square magnetic measurement test was taken to measure the magnetic flux density B50 at an angle of 0, 22.5, 45, 67.5, 90 ° inclined from the rolling direction.

  Here, the rolling process will be described. After pass-to-pass aging was performed for 5 minutes at 200 ° C. when various plate thicknesses (2.0, 1.6, 1.2, 0.8, 0.5 mm) were obtained during cold rolling, it was water cooled and cold rolled at room temperature. Finished cold rolling is finished as it is for finished plate thickness 0.8 mm, and for finished plate thickness 0.5 mm or less, it is cold to finished plate thickness (0.5, 0.35, 0.30, 0.25, 0.20, 0.15 mm) as it is after reaching plate thickness 0.5 mm. Rolled (Figure 4).

  FIG. 5 shows the influence of the total cold rolling ratio * on the magnetic flux density. When the cold rolling ratio is 75% or more, the magnetic flux density is improved by aging, except in the direction inclined 45 ° from the rolling direction. The total cold rolling ratio = 100 × (1−thickness of finished annealing sheet / thickness of hot rolled sheet).

[Experiment 3]
The steel of the chemical composition shown in Table 1 was vacuum melted. It hot-rolled by heating at 1100 degreeC, finished to plate | board thickness 2.0 mm, and wound up at 750 degreeC. The hot-rolled sheet was subjected to hot-rolled sheet annealing to equalize at 30 ° C. for 30 seconds at 1000 ° C., the cooling rate at 500 ° C. or higher was furnace cooling at 20 ° C./s and the cooling rate at less than 500 ° C. was water cooled at 100 ° C./s.

  From the hot-rolled annealed sheet, a sample for aging index to check the amount of solid solution C and a sample for Auger electron spectroscopy to check the amount of grain boundary P segregation are prepared and prepared, respectively, the amount of solid solution C and P / Fe atoms The ratio was examined. The results are shown in Table 2.

  In steel Nos. 1 to 7, the solid solution C content was totally solid solution, and the grain boundary P / Fe was also in an appropriate range, but steel No. 8 had a large C content and C was not totally solid solution. In steel Nos. 9 and 10, the grain boundary P amount was not within the appropriate range.

[Experiment 4]
Using steel Nos. 1 and 8 shown in Table 1, the effect of the cooling rate at the time of winding after hot rolling and the cooling rate after hot-rolled sheet annealing have an effect on the amount of solid solution C and grain boundary P / Fe. Examined the impact. Moreover, cementite was observed by SEM and the number density was measured. Furthermore, the ductile-brittle transition temperature (hereinafter, transition temperature) is determined by the Charpy impact test, and the Vickers hardness at 1 kg of the cross section and the hardness parameter “4.5 × (225−H)” are shown in Table 3.

  In conditions 1-e and 1-j, the cooling rate at 500 ° C. or higher was too fast, and the grain boundary P / Fe was low. Under the conditions 8-a to 8-l, even if the cooling rate at less than 500 ° C. was controlled, C did not form a solid solution, and cementite was precipitated. In addition, the Charpy transition temperature exceeded the value of the hardness parameter. On the other hand, conditions 1-a, 1-b, 1-c, 1-d, 1-f, 1-g, 1-i are solid solution C and grain boundary P / Fe is in the appropriate range. there were.

[Experiment 5]
It cold-rolled by multipass rolling using the hot-rolled sheet annealing board of Table 2 produced in Experiment 3 and finished to 0.25 mm of board thickness (rolling reduction 87.5%). Inter-pass aging was performed at a plate thickness of 1.8, 1.6, 1.2, 0.8, and 0.5 mm while holding at 200 ° C. for 300 s. Moreover, the normal cold-rolled material which abbreviate | omitted the interpass aging as a comparison material was also prepared. These cold rolled sheets are subjected to finish annealing for 30 seconds at 1000 ° C., and magnetic flux densities B50 (0) and B50 at 5000 A / m in directions inclined 0 °, 22.5 °, 45 °, 67.5 ° and 90 ° from the rolling direction. (22.5), B50 (45), B50 (67.5), B50 (90) and iron loss W10 / 400 (0), W10 / 400 (22.5), W 10/400 (45) when magnetized to 1.0 T at 400 Hz ), W10 / 400 (67.5) and W10 / 400 (90) were measured. From these results, using the following equations (4) and (5), the all-round average of B50 and W10 / 400 was determined.
B50 = {B50 (0) + 2 x B50 (22.5) + 2 x B50 (45) + 2 x B50 (67.5) + B50 (90)} / 8 (4)
W10 / 400 = {W10 / 400 (0) + 2 × W10 / 400 (22.5) + 2 × W10 / 400 (45) + 2 × W10 / 400 (67.5) + W10 / 400 (90)} / 8. · (Five)
In addition, measure the X-ray integral intensity of {200}, {110}, and {211} planes of the thickness center layer, determine the crystal orientation distribution function ODF, and measure the integral intensity of {200} planes, {222} plane. Integrated intensity of {φ ₁ , ,, φ ₂ } = {25 °, 0 °, 45 °} (corresponding to the vicinity of {100} <012> orientation), {φ ₁ , ,, φ ₂ } = { Intensity of 30 °, 55 °, 45 °} (corresponding to {111} <112> orientation), {φ ₁ , ,, φ ₂ } = {20 °, 20 °, 45 °} ({411} <148> (Equivalent to the vicinity of the azimuth) was evaluated. The results are shown in Table 4.

The steel No. 1 subjected to inter-pass aging in any steel No. increased the X-ray integral strength of the {200} plane compared to the steel No. 2 in which inter-pass aging was not performed, but decreased the {222} plane. Further, the ratio I ₂₀₀ / I ₂₂₂ was 1.00 or more in the pass No. 1 which was subjected to inter-pass aging, but was less than 1.00 in the pass No. 2 where the inter-pass aging was not performed. These results indicate that the inter-pass aging increases the strength of {100} <012> orientation preferred for magnetic properties, decreases the strength of {111} <112> orientation not preferred for magnetic properties, and the magnetic flux density B50 Increased. In the sample with good characteristics (example), the strength of the {100} <012> orientation of the crystal orientation distribution function is 6.00 or more and the intensity of the {111} <112> orientation is less than 5.00 and {100 It was found that the intensity of the <012> orientation exceeded that of the {411} <148> orientation. Note that the {411} <148> orientation is also close to the {100} plane, so although it is a preferred orientation for the magnetic properties, the {100} <012> orientation is preferred for the magnetic properties, so the high magnetic flux density B50 It is desirable to increase the strength of the {100} <012> orientation in order to obtain. On the other hand, in the sample (comparative example) in which the characteristics were not good, the intensity of the {100} <012> orientation of the crystal orientation distribution function was less than 6.00, and the intensity of the {111} <112> orientation was 5.00 or more. And, it was found that the intensity of the {100} <012> orientation was lower than the intensity of the {411} <148> orientation. In steel No. 8, since solid solution C exceeded the base value and cementite was precipitated, steel No. 10 broke during rolling because the P / Fe ratio exceeded the specified value as shown in Table 2. Focusing on steels No. 9-1 and 9-2 which normally contain P content and steels No. 1-1 and 1-2 containing 0.078% P, the grain boundary P / Fe is high as shown in Table 2. As a result, as shown in Table 3, the magnetic flux density B50 was increased, but the intensity in the {100} <012> orientation was lower than the intensity in the {411} <148> orientation. Therefore, in order to obtain the characteristics of the examples, it is necessary to have a method of performing inter-pass aging during cold rolling using the materials represented by Table 2.

[Experiment 6]
In order to investigate the influence of interpass aging temperature on magnetic properties and the influence of interpass aging time, using steel Nos. 1-g and 8-g shown in Table 3, the plate thickness during cold rolling was 1.8, 1.6 The inter-pass aging was performed at 1.2, 0.8, and 0.5 mm, and was subjected to finish annealing with 30 ° C. soaking at 1000 ° C. The results are shown in Table 5. B50 and W10 / 400 were measured in the same manner as in Experiment 5, and the whole circumference average was obtained from Equation (4) and Equation (5) and evaluated.

  Steel Nos. 8-g-1 to 10 broke during rolling. This is because, as shown in Table 3, the relationship between the Charpy transition temperature and the hardness parameter was not satisfied. Although the aging time of steel No. 1-g-10 was longer than that of steel No. 1-g-9, the magnetic flux density improvement effect was not obtained. On the other hand, in steel Nos. 1-g-1 to 9, the magnetic properties were improved by inter-pass aging.

[Reference example] (Former Sumikin Research Report RE07345)
Tanaka et al. Examined the application of interpass aging to P additives. The experimental steps are shown in FIG. Steel containing 2.0% of Si, 0.2% of Mn, 0.2% of Al, 0.01% of P in 0.3% of Al, and Si: 2.5% of Mn, 0.2% of Al, 1.0% of Al: 0.01% of P The steel containing 0.08% was vacuum-melted in a laboratory to make a hot-rolled sheet with a thickness of 2.0 mm, and this was subjected to box annealing type hot-rolled sheet annealing which is subjected to soaking at 800 ° C. for 10 h and furnace cooling. . Thereafter, finish annealing was performed so as to achieve 1s soaking at 1050 ° C. A 55 mm square magnetic measurement test was taken, and the magnetic flux density B50 in the L direction and in the T direction (C direction) was measured.

  Here, the rolling process will be described. After 2 passes of rolling at room temperature, hold for 2 minutes in a furnace at 200 ° C, air-cool to room temperature, repeat 2 passes of rolling again, process to 0.40 mm thickness, and then cold rolling The plate thickness was 0.20 mm and 0.25 mm.

  The results are shown in FIG. 7 and FIG. It was found that the effect of P addition is added to the effect of improving the magnetic flux density due to the aging, and the magnetic flux density is further improved.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modifications or alterations within the scope of the idea described in the claims, and they are naturally within the technical scope of the present invention. It is understood that.

Claims (7)

In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
And the balance consists of Fe and impurity elements,
A hot rolled sheet for a non-oriented electrical steel sheet, wherein the solid solution C concentration is 0.001 mass% or more and 0.005 mass% or less, and the P / Fe atomic ratio at the grain boundaries is 0.01 or more and 0.05 or less. The hot rolled sheet for non-oriented electrical steel sheets according to claim 1, wherein the surface Vickers hardness H of the steel sheet and the Charpy transition temperature T (° C) satisfy the following formula (1).
T (° C.) ≦ 4.5 × (225−H) ··· Formula (1) In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
And the balance consists of Fe and impurity elements,
The ratio I200 / I222 of the X-ray integral intensity I200 of the {200} plane to the X-ray integral intensity I222 of the {222} plane is 1.00 or more,
The strength of {φ1, ,, φ2} = {25 °, 0 °, 45 °} in the crystal orientation distribution function is 6.00 or more, and {φ1, φ, φ2} = {30 °, 55 °, 45 ° The strength of} satisfies less than 5.00,
{φ1, φ, φ2} = {25 °, 0 °, 45 °} strength ≧ {φ1, φ, φ2} = {20 °, 20 °, 45 °} strength,
A non-oriented electrical steel sheet having a crystal grain size of 30 μm or more and a plate thickness of 0.10 mm or more and 0.50 mm or less. A method of manufacturing a hot-rolled sheet for non-oriented electrical steel sheet according to any one of claims 1 or 2,
In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
After hot-rolling and annealing a steel piece containing the balance of Fe and an impurity element, and then cooling the temperature range of 500 ° C. or more at a cooling rate of 10 ° C./s or more and 100 ° C./s or less, The manufacturing method of the hot-rolled sheet for non-oriented electrical steel sheets which cools a temperature range less than 500 ° C with a cooling rate larger than a cooling rate in a temperature range 500 ° C or more. A method of manufacturing a hot-rolled sheet for non-oriented electrical steel sheet according to any one of claims 1 or 2,
In mass%
2.0% ≦ Si ≦ 4.0%,
0.01% ≦ Al ≦ 3.0%,
0.05% ≦ Mn ≦ 2.5%,
0.03% ≦ P ≦ 0.12%,
0.001% ≦ C ≦ 0.005%,
S ≦ 0.005%,
N ≦ 0.005%
Is hot rolled and the coil is wound at 700 ° C. or higher, and the temperature range of 500 ° C. or higher is cooled by 10 ° C./s or more and 100 ° C./s or less A method for producing a hot rolled sheet for non-oriented electrical steel sheet, comprising: cooling at a speed and cooling a temperature range of less than 500 ° C. at a cooling rate greater than a cooling rate in a temperature range of 500 ° C. A method of manufacturing a non-oriented electrical steel sheet according to claim 3 by cold-rolling and hot-rolling the hot-rolled sheet for non-oriented electrical steel sheet according to any one of claims 1 or 2 ,
A method of manufacturing a non-oriented electrical steel sheet, wherein the cold rolling is multipass rolling with a total rolling reduction of 75% to 95%, and an aging treatment is performed at 100 ° C to 400 ° C for 1 to 60 minutes between each pass. . Performing decarburization annealing after the cold rolling, after the, performing the final annealing method for producing a non-oriented electrical steel sheet according to claim 6.