JPH0823046B2 - Manufacturing method of non-oriented electrical steel sheet with excellent magnetic properties - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties, particularly high magnetic flux density.

[Problems to be Solved by Prior Art and Invention]

Conventionally, various manufacturing techniques have been developed in order to manufacture a non-oriented electrical steel sheet having good magnetic properties. Among the magnetic properties, the magnetic flux density is closely related to the texture of the steel sheet, and it is necessary to integrate the <100> axis, which is the easy axis of magnetization, on the surface of the steel sheet as much as possible. Therefore, the technology for improving the hot rolled sheet structure by hot rolled sheet annealing, the technology for controlling the recrystallization texture during the subsequent annealing by optimizing the cold pressure ratio, the cold pressure and the annealing twice or more There are known techniques for turbidity to obtain a texture that is preferable in terms of magnetic properties by carrying out the method, but in reality, no satisfactory improvement effect can be obtained.

[Means for solving the problem]

In view of such a conventional technique, the present invention attempts to improve the magnetic flux density by performing cold rolling using a roll having longitudinal grooves in the roll circumferential direction.

By the way, the cold rolling technology for electrical steel sheets using groove rolls (grooved rolls) has traditionally produced electrical steel sheets having a (100) plane cubic texture that combines the characteristics of grain-oriented electrical steel sheets and non-oriented electrical steel sheets. Have been considered as a possible means to achieve (for example, "Iron and Steel" 63 (1977) P.182.
8, P.1838, P.2335, "Iron and Steel" 70 (1984) P.2065).
The technical idea is that the width of the steel sheet is expanded during cold rolling, so that {100} <011> to {100} after recrystallization annealing.
To develop a <0vw> texture. As one based on such a technical idea, for example, Japanese Patent Publication No. 54-10
No. 922 and Japanese Patent Publication No. 53-30098 are proposed. But,
In these conventional reports, decarburization annealing and purification annealing at a temperature of 1000 ° C. or higher are added after rolling, and the steel composition (C> 0.
03%, Si: ~ 3%, Mn: ~ 0.2%, S> 0.01%, Al: ~ 20pp
Even if judged from m), it is clearly aimed at controlling the secondary recrystallization texture. On the other hand, heretofore, no example has been found in which the application of flute roll rolling to the texture control of general non-oriented electrical steel sheets was examined.

Under such circumstances, the present invention aims to improve the magnetic flux density of the non-oriented electrical steel sheet, and by applying rolling with a fluted roll to part of the cold rolling, during cold rolling. The formation of the texture is changed from a plane strain state as in the conventional smooth roll rolling to a state of deformation accompanied by a material flow in the strip width direction.

The present invention is that rolling by means of longitudinal grooved rolls is extremely effective for improving the magnetic properties of the steel sheet, and that the groove arrangement, size, etc. of the rolls used at that time have a great influence on the magnetic properties of the steel sheet. It was made based on these findings.

That is, the feature of the present invention is that, in% by weight,
C: 0.01%, Si: 7.0% or less, Mn: 0.1 to 1.5%, P: 0.15% or less, S: less than 0.01%, Al: 0.001% or less or 0.05 to 1.0
%, N: 0.005% or less, a hot-rolled steel strip having a composition consisting of the balance Fe and unavoidable impurities is annealed or not annealed once or twice or more by cold rolling or intermediate annealing. In producing a non-oriented electrical steel sheet by a series of steps of annealing after performing warm rolling,
In the cold rolling or warm rolling step, rolling in one or more rolling passes not including the final pass is performed in the circumferential direction of the roll surface in the groove pitch 1 (mm) and groove depth d (mm).
Is 0.5 ≦ (l / t) ≦ 2.5 0.1 ≦ (d / t) ≦ 0.5 with respect to the initial plate thickness t (mm) of the rolled material, and the groove pitch l in the section passing through the roll axis is
The roll groove cross-sectional area S (mm ² ) per hit is 0.15 ≤ [S / (ld)] ≤ 0.65 using a roll in which longitudinal grooves are arranged at equal intervals in the roll longitudinal direction, and the final The rolling in one or more rolling passes including the pass is performed by using a smooth roll having no longitudinal groove.

Further, in such a method of the present invention, in the cold rolling or warm rolling step, the rolling in the final pass of the rolling performed using the fluted roll, the convex portion of the material to be rolled after this rolling, That is, the cross-sectional area A (mm ² ) per groove pitch 1 (mm) of the steel sheet portion flowing into the roll groove is (A / S) ≧ with respect to the roll groove cross-sectional area S (mm ² ) per groove pitch 1 It is preferable to carry out under the condition of satisfying 0.6.

[Action]

Hereinafter, the details of the present invention will be described together with the reasons for limitation.

 First, the reasons for limiting the steel components will be described.

C: The present invention maximizes the advantages of carrying out decarburization of steelmaking, and further, on the purpose of solving the problem of structure formation during cold rolling, C is a final product. In practice, the upper limit is 0.01%. Regarding magnetic aging, it is preferable that C is small and the lower limit is not limited, but the lower limit is practically the limit of the steelmaking degassing technology.

Si: The technique of the present invention is practically effective regardless of the amount of Si, and therefore the lower limit is not particularly limited. Regarding the upper limit, it is a technology that can be applied to all in the practical range of Si content, but steel with a Si content of more than 7.0% has no merit in terms of utilization technology in addition to the difficulty of the manufacturing method. In the invention, 7.0% is the upper limit of Si.

Al: Al, like Si, has the effect of increasing the specific resistance and reducing iron loss, and is often added to non-oriented electrical steel sheets. In the present invention, the upper limit is set to 1.0% as a limit added to a general non-oriented electrical steel sheet. There is no restriction on the lower limit in order to exert the effects of the present invention. However, when a small amount of Al is added to the non-oriented electrical steel sheet, finely precipitated AlN hinders grain growth during the final annealing, resulting in an increase in iron loss value. The amount of Al that causes such a problem is in the range of more than 0.001% to less than 0.05%,
In the present invention, it is essential that the amount of Al in this range is not included. For the above reasons, Al is 0.001% or less or 0.05 to 1.0%
Stipulated.

With respect to other elements, it is not necessary to specifically limit them in relation to the action and effect of the present invention, but in consideration of the original influence of the component elements on magnetic properties, Mn: 0.1 to 1.5%, P
Specified as ≦ 0.15%, S <0.01%, N ≦ 0.005%.

Next, the manufacturing conditions of the present invention will be described. In the present invention, the hot-rolled steel strip having the above composition is annealed as necessary, and is subjected to one or two or more cold rolling or warm rolling with intermediate annealing, and then annealing, which is a series of steps. Non-oriented electrical steel sheet is manufactured by the above method, but the cold rolling or warm rolling process is extremely important. A part of this rolling is arranged in the circumferential direction of the roll surface at equal intervals in the longitudinal direction of the roll. It is characterized in that it is carried out by using a roll having a formed vertical groove.

In the present invention, it is essential that the grooves of the roll used in the grooved roll rolling are formed in the roll circumferential direction and arranged at equal intervals in the roll longitudinal direction. The grooves on the roll surface must be longitudinal grooves in the roll circumferential direction in order to form waviness with a large metal flow in the plate width direction during grooved roll rolling and flattening rolling. Further, if the intervals are irregular, the magnetic properties of the final product may change greatly depending on the position in the plate width direction, which is not preferable.

Further, regarding the arrangement of the vertical grooves of the vertical grooved roll, particularly the angle formed by the grooves with respect to the roll circumferential direction becomes a problem in relation to the occurrence of surface defects (microscopic baldness).

As described above, in the conventionally proposed manufacturing technique of the electrical steel sheet having the (100) face cubic texture, a roll having a horizontal groove as well as a vertical groove, or two intersecting directions angled with respect to the roll circumferential direction. Mostly, a roll having a groove is used. However, when a plate is rolled by a roll having such grooves intersecting with each other, the transferred convex portion is crushed by friction with the roll during flattening rolling, and a fine lamination is formed. Therefore, it is preferable to use a roll with vertical grooves that does not intersect with the vertical grooves. In the case of providing grooves having an angle with respect to the roll circumferential direction, it is necessary to symmetrically provide grooves whose inclinations are opposite to each other in order to meet the requirements of the passing plate. When the grooves are provided in this manner, it becomes unavoidable that the grooves intersect each other when the inclination angle becomes large to some extent. Therefore, even if the groove is formed at an angle with respect to the circumferential direction of the roll, the vertical groove should not intersect with each other. The angle of the vertical groove with respect to the roll circumferential direction is preferably 5 ° or less in consideration of the vertical groove interval and the like.

In the present invention, the groove cross-sectional shape of the roll used in the vertical grooved roll rolling is not particularly specified. The cross-sectional shape is V
Sufficient effects are recognized in any of a die, a U-shape, a semicircle, a trapezoid, a sine wave, and the like. 1 (A) to 1 (G) schematically show typical examples of groove cross-sectional shapes of the fluted roll used in the present invention.

On the other hand, the groove pitch l (mm), the groove depth d (mm), and the roll groove cross-sectional area (relative size of the groove) S (mm ² ) per groove pitch 1 in the cross section passing through the roll axis are Has a great impact on the effects of.

FIG. 2 shows the results of examination of the magnetic flux density B ₅₀ when the groove pitch 1 and the groove depth d of the roll were variously changed.
In the figure, t is the initial plate thickness (mm) of the rolled material, and ΔB
₅₀ indicates the amount of increase in the magnetic flux density B ₅₀ of the rolled material with longitudinal grooves as compared with the rolled material with normal smooth rolls. Each test material is
Hot-rolled sheet having the composition of Steel A in Table 1 (sheet thickness 1.6 mm, 2.0 m
m, 3.2 mm (3 types) using various fluted rolls, followed by flattening with smooth rolls, then 800 ° C
It was annealed at. The groove cross section is 1.6 mm thick.
Material is V type as shown in Fig. 1 (A), 2.0mm material is U type as shown in Fig. 1 (C), 3.2mm material is square type as shown in Fig. 1 (F). I was there.

As is clear from the figure, when the groove pitch 1 is too large or the groove depth d is too small, the effect of improving the magnetic flux density is small, and even if the initial plate thickness changes, the ratio of l and d to the initial plate thickness is small. When l / t and d / t are in the range of (l / t) ≦ 2.5 and (d / t) ≧ 0.1, a sufficient magnetic flux density improving effect is obtained. On the other hand, when the groove pitch 1 is too small or the groove depth d is too large, that is, (l / t) <0.5 or (d / t)> 0.5.
In the case of (4), when the steel plate convex portion is crushed by the friction with the roll during flattening rolling, a minute lamination is formed, which causes a surface defect (microscopic baldness), which is not preferable. For the above reason, in the present invention, the groove pitch l (mm) and the groove depth d (mm) of the roll are 0.5 ≦ (l / t) with respect to the initial plate thickness t (mm) of the material to be rolled. ) ≦ 2.5 0.1 ≦ (d / t) ≦ 0.5

Next, FIG. 3 shows the roll groove cross-sectional area S (mm ² ) per groove pitch 1 in the section passing through the roll axis and the groove pitch 1
The change in magnetic flux density when S / (ld) (relative size of the groove) defined by (mm) and groove depth d (mm) is used as a parameter is shown. Each test material was obtained by rolling a hot-rolled sheet (sheet thickness 2.0 mm) having the composition of steels A and B shown in Table 1 using various fluted rolls, followed by flattening rolling with smooth rolls, It was annealed at 780 ° C. Even if the pitch 1 and the depth d of the groove are within the above-mentioned optimum range, the groove cross-sectional area S changes depending on the difference in the groove cross-sectional shape, the groove opening width, and the like. Therefore, 0.15 ≦ [S /
(L / d)] ≦ 0.65, sufficient improvement of magnetic flux density is recognized. Therefore, in the present invention, the groove cross-sectional area S is limited to the range of 0.15 ≦ [S / (ld)] ≦ 0.65.

Such a fluted roll is usually produced by forming grooves on a smooth roll by machining or laser irradiation, but any other method may be used.

Further, the fluted roll rolling and flattening rolling in the present invention are not only cold rolling but also warm rolling (usually: 400 ° C. or less).
Even if it is carried out, the effect can be sufficiently obtained.

Further, in the present invention, the rolling of the final pass in the cold rolling or warm rolling step is required to be performed by using a smooth roll in order to completely eliminate the unevenness of the steel sheet surface, but for other rolling passes The combination of the fluted roll rolling and the flattening rolling is optional, and even if the fluted roll rolling and the flattening rolling are alternately repeated, or the fluted roll rolling is performed for several passes, the flattening rolling is performed. You may.

However, in order to make the effect of the present invention more remarkable, it is preferable to carry out the final pass rolling using the fluted rolls under specific rolling conditions. In the longitudinal grooved roll rolling, the rolling conditions are variously changed, and the cross-sectional area A (mm) per groove pitch 1 of the convex portion of the material to be rolled after the rolling by the final grooved roll, that is, the portion flowing into the roll groove. ² ) and the ratio A / S of the roll groove cross-sectional area S (mm ² ) per groove pitch 1 and the increase ΔB ₅₀ of the magnetic flux density B ₅₀ with respect to the normal rolled material were investigated. The results are shown in FIG. Also, the groove cross-sectional shape of the work roll used at this time is shown in FIG. The conditions (test material, annealing conditions, etc.) other than the groove cross-sectional shape and rolling conditions of the longitudinal grooved roll rolling were the same as in the case of FIG. From the results shown in FIG. 4, it can be seen that the effect of the present invention becomes extremely remarkable under the rolling conditions such that the A / S is 0.6 or more.

Incidentally, the cold rolling or warm rolling in the method of the present invention,
Not only tandem rolling, but also reverse rolling can be performed. Further, even when cold pressing is performed twice or more with intermediate annealing, it suffices to perform flattening rolling in one or more final passes, that is, one pass including the final pass of the final cold pressure. Is not particularly limited.

Example 1. A continuously cast slab having the composition shown in Steel No. 1 in Table 2 was heated to 1200 ° C.
After heating to 0.degree. C., it was subjected to rough rolling and finish rolling steps to obtain a 2.0 mm ^t hot rolled sheet, which was wound at 670.degree. After pickling, roll rolling with vertical groove on No. 1 to 3 stands of 5 stand continuous rolling mill,
In addition, flattening rolling with smooth rolls was performed on No. 4 and 5 stands. Rolling with longitudinal grooves was carried out by attaching four types of groove-shaped rolls shown in FIGS. 5 (A) to (D) to the upper rolls of the No. 1 to 3 stands. Also, as a comparative example
Rolling using a normal smooth roll was also carried out for No. 1 to 5 stands. After continuously annealing these at 800 ° C., their magnetic properties were measured. Further, these actual cold-pressed plates were annealed in a laboratory at various temperatures of 625 to 850 ° C. for a soaking time of 90 sec, and the X-ray integrated reflection intensity was measured.

FIG. 6 shows a photograph of the microstructure of the steel sheet C cross section after roll rolling with vertical grooves. (A) to (D) of the same figure are those rolled by the grooved rolls having the groove shapes of FIGS. 5 (A) to (D), respectively.

FIG. 7 (A) shows a (200) pole figure after flattening rolling of the rolled material by the grooved roll having the groove shape shown in FIG. 5 (A), and FIG. 7 (B) shows a normal smooth surface. The (200) pole figure after rolling of the rolled material is shown. Further, FIG. 8 (A) is a (200) pole figure of the steel sheet of FIG. 7 (A) after continuous annealing at 800 ° C., and FIG. 8 (B) is the same as that of the steel sheet of FIG. 7 (B).
The (200) pole figure after continuous annealing at 0 ° C is shown.

9 (A) to 9 (F), the groove shape is shown in FIG. 5 (B).
(C) (D) grooved roll (200) surface of the rolled material,
The X-ray integrated reflection intensity of the (222) plane is shown in comparison with a normal smooth roll rolled material.

From these results, it is understood that the rolled material with longitudinal grooves has a different deformation state during rolling from that of the smooth rolled material, and the rolling texture and primary recrystallization texture are changed.

Table 3 shows the measurement results of the magnetic properties. According to this,
Rolled material with vertical grooves is usually more smooth than smooth rolled material.
It can be seen that the magnetic properties, especially the magnetic flux density, are excellent.

Example 2. A continuous cast slab having the composition of steel numbers 2 to 4 in Table 2 was prepared.
After heating to 1140 ° C., a hot-rolled sheet of 2.0 mm ^t was subjected to rough rolling and finish rolling steps, and wound at 640 ° C.

Part of Steel No. 2 and Steel Nos. 3 and 4 were annealed by hot rolling. Steel No. 2 was as-wound material and annealed material, and Steel Nos. 3 and 4 were annealed materials after pickling and under various conditions. After performing roll rolling with vertical groove in, followed by flattening rolling to 0.5 mm ^t ,
Steel No. 2 was subjected to final annealing at 900 ° C, steel No. 3 at 950 ° C, and steel No. 4 at 960 ° C, and the magnetic properties after annealing were measured.
In the above hot-rolled sheet annealing, steel No. 2 was 750 ° C, steel Nos. 3 and 4
Was performed by box annealing (BA) at 850 ° C. This annealing is A
It can be carried out by continuous annealing of P line, etc.
For, the continuous annealing (AP) at 950 ° C was also performed. Steel No. 3 was also cold-rolled twice with intermediate annealing of 850 ° C. × 3 hr, and steel No. 4 was warm-rolled at a rolling temperature of 300 ° C. For comparison, the same test material was rolled only by a conventional smoothing roll, and its magnetic characteristics were measured. The results are shown in Table 4.

[Brief description of drawings]

FIGS. 1 (A) to 1 (G) are explanatory views showing the groove cross-sectional shape of a roll having vertical grooves. FIG. 2 shows a roll groove pitch l,
Is a diagram showing the relationship between the groove depth d and the magnetic flux density increases the amount .DELTA.B _50. Fig. 3 shows the parameter S / (l
d) as a diagram showing the relationship between the magnetic flux density B _50. Figure 4 shows
FIG. 5 is a diagram showing a relationship between rolling condition A / S and an increase amount ΔB _{50 of} magnetic flux density in roll rolling with longitudinal grooves. FIG. 5 is an explanatory view showing the groove cross-sectional shape and dimensions of the vertical grooved roll. FIGS. 6 (A) to 6 (D) are microscopic enlarged photographs showing the steel structure in the C-direction cross section of the steel plate after roll rolling with flutes. Fig. 7 (A)
(B) is a (200) pole figure which shows the rolling texture of this invention material and the conventional material, respectively. 8 (A) and (B)
It is a (200) pole figure which shows the primary recrystallized texture of this invention material and the conventional material, respectively. 9 (A) to 9 (F) are diagrams showing the textures of the material of the present invention and the conventional material.

Claims (2)

[Claims] 1. By weight%, C: 0.01% or less, Si: 7.0% or less,
Mn: 0.1-1.5%, P: 0.15% or less, S: less than 0.01%, Al: 0.00
1% or less or 0.05 to 1.0%, N: 0.005% or less, a hot-rolled steel strip having a composition consisting of balance Fe and unavoidable impurities is annealed or not annealed once or twice with intermediate annealing. In producing a non-oriented electrical steel sheet by a series of steps of performing annealing after performing the above cold rolling or warm rolling, in the cold rolling or warm rolling step, the final pass is not included 1 or more. Rolling in the rolling pass is performed in the circumferential direction of the roll surface in the groove pitch l.
(Mm) and groove depth d (mm) are the initial plate thickness t (m
m ≦ 0.5 ≦ (l / t) ≦ 2.5 0.1 ≦ (d / t) ≦ 0.5, and the roll groove cross-sectional area S (mm ² ) per groove pitch 1 in the section passing through the roll axis is 0.15. Rolling in one or more rolling passes including the final pass is performed by using rolls having longitudinal grooves arranged at equal intervals in the roll longitudinal direction such that ≦ [S / (ld)] ≦ 0.65. A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, which is performed by using a smooth roll having no magnetic field. 2. Cross-sectional area A per groove pitch l (mm) of a steel sheet portion that has flowed into a roll groove by rolling in the final pass of rolling performed using a roll having longitudinal grooves.
(Mm ² ) is the roll groove cross-sectional area S (m
m ² ) is performed under the condition that (A / S) ≥ 0.6 is satisfied.
The method for producing a non-oriented electrical steel sheet having excellent magnetic properties according to 1.