JPH03267319A - Production of nonoriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To improve magnetic flux density by carrying out a part of rollings prior to the annealing of a hot rolled plate by using a rolling roll having longitudinal grooves in which the arrangement, size, etc., of grooves arc specified and which are provided in the peripheral direction of the roll. CONSTITUTION:A hot rolled strip of a steel having a composition consisting of, by weight, <=0.01% C, <=7.0% Si, 0.1-1.5% Mn, <=0.1% P, <0.01% S, <=0.001% or 0.05-1.0% Al, <=0.005% N, and the balance Fe is used. This steel strip is subjected, if necessary, to annealing, cold- rolled or warm-rolled once or subjected to cold rolling or warm rolling twice or more while process-annealed between the cold or warm rolling stages, and then annealed, by which a silicon steel sheet is obtained. At this time, in the above cold or warm rolling stage, rollings in one or more passes not including the final pass are carried out by using a roll formed by arranging, in the peripheral direction of the roll surface, longitudinal grooves in which groove pitch (l)(mm) and groove depth (d)(mm) satisfy inequalities I, II with respect to the initial sheet thickness (t)(mm) of the stock to be rolled and also the cross-sectional area S(mm<2>) of the groove part per groove pitch (l) in the cross section passing a roll shaft satisfies an inequality III at equal spaces in the longitudinal direction of the roll. Then, rollings in one or more passes including the final pass are carried out by using smooth roll.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application 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.

[Prior Art and Problems to be Solved by the Invention] Conventionally, a number of manufacturing techniques have been developed in order to manufacture non-oriented electrical steel sheets 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 an axis of easy magnetization, on the surface of the steel sheet as much as possible. To this end, we have developed a technology to improve the hot-rolled sheet structure through hot-rolled sheet annealing, a technology to control the recrystallized texture during subsequent annealing by optimizing the cold-rolling rate, and a technique for cold-rolling and annealing two or more times. Techniques are known in which the texture is turbidized to have a preferable texture in terms of magnetic properties, but the reality is that none of these methods yields a sufficiently satisfactory improvement effect.

[Means to solve the problem]

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

By the way, cold rolling technology for electrical steel sheets using group rolls (grooved rolls) has conventionally been used to produce electrical steel sheets with a (100) surface cubic texture that combines the characteristics of grain-oriented and non-oriented electrical steel sheets. It has been considered as a powerful means to
) P, 1828, P, 1838, P, 2335, "Tetsu to Hagane J 70 (1984) P, 2065).The technical idea is that by making the width of the steel plate during cold rolling,
After recrystallization annealing (100) (011>~(100)
The goal is to develop the collective structure of Ovsu. Based on this technical idea, for example, Japanese Patent Publications No. 10922/1982 and Japanese Patent Publication No. 30098/1973 have been proposed. However, these conventional In the report, 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%, u: ~20p
Judging from pm), it is clearly aimed at controlling the secondary recrystallization texture. On the other hand, there has been no study on the application of fluted roll rolling to texture control of general non-oriented electrical steel sheets.

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

The present invention provides that rolling with vertically grooved rolls is extremely effective in improving the magnetic properties of steel sheets, and that the arrangement, size, etc. of the grooves of the rolls used at that time have a great effect on the magnetic properties of steel sheets. This study was based on this knowledge.

That is, the feature of the present invention is that, in weight %, C
: 0.01% or less, Si: 7.0% or less, Mn:
0.1-1.5%, P: 0.15% or less, S: 0.
less than 0.01%, Al2 0.001% or less or 0.05~
A hot rolled steel strip having a composition of 1.0%, N: 0.005% or less, the balance Fe and unavoidable impurities is annealed as necessary, and cooled once or twice or more with intermediate annealing. In manufacturing a non-oriented electrical steel sheet by a series of steps of performing inter-rolling or warm rolling and then annealing, one or more rolling passes not including the final pass in the above-mentioned cold rolling or warm rolling step. rolling in the circumferential direction of the roll surface with groove pitch Q (mm) and groove depth d (
mm) is 0.
5≦(l/l)≦2.5 0.1≦(d/l)≦0.5, and the groove pitch Q in the cross section passing through the roll axis
The per roll groove cross-sectional area 5 (an2) is 0.15≦
[S/(ld))≦0.65] is carried out using a roll in which vertical grooves are arranged at equal intervals in the longitudinal direction of the roll,
Another feature is that rolling in one or more rolling passes including the final pass is performed using smooth rolls having no vertical grooves.

In addition, in the method of the present invention, in the cold rolling or warm rolling step, (2) the roll having vertical grooves is used to roll the rolled material after this rolling. The cross-sectional area A (m2) per groove pitch Q (kaku) of the convex part, that is, the part of the steel plate that has flowed into the roll groove, is given by (A/S) with respect to the roll groove cross-sectional area S (■2) per groove pitch Q. )≧0.6.

[For production]

Hereinafter, the details of the present invention will be explained together with the reasons for its limitations.

First, the reason for limiting the steel components will be explained.

C; Since the present invention focuses on maximizing the benefits of steel decarburization and solving the problem of structure formation during cold rolling, C is the final product. The upper limit is 0.0 as the limit that is practically allowed in
Limited to 1%. Regarding magnetic aging, it is preferable to have a small amount of C, and although the lower limit is not limited, the lower limit is essentially the limit of steelmaking degassing technology.

Sj: 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, the technology is applicable to all practical Si content ranges, but steel with Si content exceeding 7.0%
In addition to the difficulty of the manufacturing method, there is no advantage regarding the technology used, and for this reason, in the present invention, the upper limit of Si is set at 7.0%.

Al: Like Si, Al has the effect of increasing specific resistance and reducing iron loss, so it is often added to non-oriented electrical steel sheets. In the present invention, the upper limit of addition to a non-oriented electrical steel sheet is defined as 1.0%.

Regarding the lower limit, there is no restriction in achieving the effects of the present invention. However, when a small amount of 80 is added to a non-oriented electrical steel sheet, finely precipitated MN inhibits grain growth during final annealing, resulting in an increase in iron loss value. The amount of Afl that causes such problems is more than 0.001% to 0.0
The amount of Al is in the range of less than 5%, and 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
．． 0.001% or less or 0.05 to 1.0%.

Regarding other elements, there is no need to impose any special restrictions in relation to the effects of the present invention, but considering the inherent influence of the component elements on magnetic properties, Mn: 0.1 to 1
．． 5%, P≦0.15%, S<0.01%, N≦0.0
05%.

Next, the manufacturing conditions of the present invention will be explained. In the present invention, a hot rolled steel strip having the above composition is annealed as necessary,
A non-oriented electrical steel sheet is manufactured by a series of steps in which cold rolling or warm rolling is performed once or twice or more with intermediate annealing, and then annealing is performed, but the above-mentioned cold rolling or warm rolling step is extremely important, and part of this rolling
It is characterized in that it is carried out using a roll having vertical grooves formed on the roll surface in the circumferential direction and arranged at equal intervals in the roll longitudinal direction.

In the present invention, it is essential that the grooves of the roll used for grooved roll rolling be formed in the circumferential direction of the roll and arranged at equal intervals in the longitudinal direction of the roll. In order to form large undulations in the metal flow in the width direction of the sheet during rolling with grooved rolls and flattening rolling, the grooves on the roll surface must be longitudinal grooves in the circumferential direction of the roll. Furthermore, if the spacing is irregular, the magnetic properties of the final product may vary greatly depending on the position in the sheet width direction, which is not preferable.

Furthermore, regarding the arrangement of the vertical grooves of a vertically grooved roll, the angle that the grooves make with respect to the circumferential direction of the roll poses a problem in relation to the occurrence of surface defects (micro-scratches).

In the conventionally proposed manufacturing technology for electrical steel sheets having a (100) bicubic texture, as described above, rolls have horizontal grooves as well as vertical grooves, or two intersecting directions at an angle to the roll circumferential direction are used. The main type uses rolls with grooves. However, when a plate is rolled with such rolls having intersecting grooves, the transferred convex portions are crushed by friction with the rolls during flattening rolling, resulting in the formation of minute laminations. Therefore, it is preferable to use a vertically grooved roll whose vertical grooves do not intersect. When providing grooves having an angle with respect to the roll circumferential direction, it is necessary to provide grooves with opposite inclinations symmetrically due to requirements for sheet threading. When grooves are provided in this manner, when the inclination angle becomes large to a certain extent, the grooves inevitably intersect with each other.

Therefore, even when the grooves are formed at an angle with respect to the roll circumferential direction, the vertical grooves should not intersect with each other.

In relation to the vertical groove spacing, etc., it is preferable that the angle of the vertical grooves with respect to the roll circumferential direction is 5° or less.

In the present invention, the groove cross-sectional shape of the roll used in the fluted roll rolling is not particularly defined. Sufficient effects can be found in any cross-sectional shape such as V-shape, U-shape, semicircle, trapezoid, or sinusoidal shape.

FIGS. 1(A) to 1(G) schematically show representative examples of the groove cross-sectional shapes of the vertically grooved roll used in the present invention.

On the other hand, the groove pitch R (mm), the groove depth d (al), and the roll groove cross-sectional area (relative groove size) S (mm2) per groove pitch Q in the cross section passing through the roll axis are It has a great influence on the working effect.

FIG. 2 shows the results of investigating the magnetic flux density B5o when the groove pitch Q and groove depth d of the roll were varied.

In the figure, t is the initial plate thickness of the material to be rolled, and ΔB
s0 indicates the amount of increase in magnetic flux density B5° of the vertically grooved roll-rolled material relative to the normal smooth roll-rolled material. Each test material was a hot-rolled plate (thickness: 1.6 m) having the composition of steel A in Table 1.
3 types (m, 2.0 m, and 3.2 m) were rolled using various vertically grooved rolls, and then flattened using smooth rolls, and then annealed at 800°C. Note that the cross-sectional shape of the groove is V-shaped as shown in Figure 1 (A) for the 1.6 m thick material, U-shaped as shown in Figure 1 (C) for the 2.0 m material, and 3.2 +
The s-shaped material used was a square one as shown in the same figure (F).

As is clear from the figure, if the groove pitch Q is too large or the groove depth d is too small, the magnetic flux density improvement effect is small, and even if the initial plate thickness changes, the ratio of Q and d to the initial plate thickness is small. Qha and dha are (lt)≦2.5 and (d/l)≧
When the value is in the range of 0.1, a sufficient effect of improving magnetic flux density is obtained. On the other hand, if the groove pitch Q is too small or the groove depth d
If is too large, that is, (l/l)<0.5 or (d/t)>0.5, minute laminations may occur when the convex portion of the steel plate is crushed by friction with the roll during flattening rolling. This is undesirable because it causes surface defects (micro-scratches). For the above reasons, in the present invention, the groove pitch Q (mn) of the roll,
The groove depth d (mm) is set to the initial plate thickness t (gn) of the rolled material as follows: 0.5 ≦ (l/l) ≦ 2.5 0.1 ≦ (d/l) ≦ 0.5 limited to a range.

Next, Fig. 3 shows the groove pitch Q in the cross section passing through the roll axis.
S/(f
ld) (relative size of the groove portion) as a parameter. Each sample material was steel A in Table 1.
, a hot-rolled sheet having a composition of B (thickness 2.01ffi (mm
) was rolled using various vertically grooved rolls, flattened using bowed continuous smooth rolls, and then annealed at 780°C. Even if the groove pitch Q and depth d are within the optimum ranges mentioned above, the groove cross-sectional area S will change due to differences in the cross-sectional shape of the groove, the width of the groove opening, etc.; As is clear, 0.15≦C8/CQ d ))≦0
．． A sufficient improvement in magnetic flux density is observed in the range of 65. Therefore, in the present invention, the groove cross-sectional area S is set to 0.
The range was limited to 15≦[S/(ld))≦0.65.

Such a vertically grooved roll is usually produced by forming grooves on a smooth roll by machining or laser irradiation, but it may be produced using any other method.

Furthermore, the fluted roll rolling and flattening rolling in the present invention can be carried out not only by cold rolling but also by warm rolling (usually at 400° C. or lower) to obtain sufficient effects.

Furthermore, in the present invention, the final pass of rolling in the cold rolling or warm rolling process must be carried out using smooth rolls in order to completely eliminate the unevenness on the surface of the steel sheet.
The combination of fluted roll rolling and flattening rolling for other rolling passes is arbitrary, and even if fluted roll rolling and flattening rolling are repeated alternately, or after several passes of fluted roll rolling are performed. , flattening rolling may be performed.

However, in order to make the effects of the present invention even more remarkable, the final pass of rolling using fluted rolls should be as follows:
It is preferable to carry out under specific rolling conditions. In rolling with fluted rolls, the rolling conditions are variously changed, and the cross-sectional area A (m , 2) and the roll groove cross-sectional area S (m2) per groove pitch Q, A/S, and the increase amount ΔBf0 of the magnetic flux density B5° relative to the normally rolled material was investigated. The results are shown in FIG. Moreover, the groove cross-sectional shape of the work roll used at this time is shown in FIG. 5(D). In addition, conditions other than the groove cross-sectional shape and rolling conditions (test material,
The annealing conditions, etc.) were the same as in the case of Fig. 3. From the results shown in FIG. 4, it can be seen that the effect of the present invention becomes extremely significant when the rolling conditions are such that A/S is 0.6 or more.

Note that the cold rolling or warm rolling in the method of the present invention is not limited to tandem rolling, but may also be performed by reverse rolling. Furthermore, even if cold rolling is performed two or more times with intermediate annealing in between, it is sufficient to perform flattening rolling in one or more passes including the final pass, that is, the last pass of the final cold rolling; There are no particular limitations.

Table 1 (1%) Example 1゜1200 continuous cast slabs having the composition shown in Perfume 1 of Table 2
After heating to ℃, it undergoes rough rolling and finish rolling process to 2.0a+t.
A hot-rolled sheet was prepared and coiled at 670°C. After pickling,
Rolling with fluted rolls was carried out on stands Nα1 to 3 of a 5-stand continuous rolling mill, and flattening rolling was carried out using smooth rolls on a stand Nα4.5. Rolling with vertical grooves is N
Figures 5 (A) to (D) on the upper roll of CLI~3 stand.
The tests were carried out using rolls with four types of groove shapes shown in the figure.

In addition, as a comparative example, rolling was also carried out using normal smooth rolls for both stands 1 to 5. 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 from 625 to 850° C. for a soaking time of 90 seconds, and the integrated X-ray reflection intensity was measured.

FIG. 6 shows a photograph of the cross-sectional microstructure of the steel sheet C after rolling with a fluted roll. (A) to (D) in the same figure are the fifth
It is rolled using a grooved roll having the groove shapes shown in Figures (A) to (D).

FIG. 7(A) shows the (200) pole figure after flattening rolling of the rolled material with the grooved roll having the groove shape of FIG. 5(A), and FIG. The (200) pole figure of the roll-rolled material after rolling is shown. Furthermore, Fig. 8(A) shows the (200) pole figure of the steel plate of Fig. 7(A) after continuous annealing at 800°C, and Fig. 8(B) shows the same < The (200) pole figure after continuous annealing at 800°C is shown.

In addition, the groove shapes in Figures 9 (A) to (F) are shown in Figure 5 (B).
(C) (D) (7) Grooved roll roll material (7)
The integrated X-ray reflection intensity of the (200) plane and the (222) plane is shown in comparison with that of a normal smooth roll rolled material.

From these results, it can be seen that the deformation state of the fluted roll-rolled material during rolling is different from that of the normal smooth roll-rolled material, and that the rolling texture and -original crystal texture are changed.

Table 3 shows the measurement results of magnetic properties. According to this, it can be seen that the fluted roll-rolled material is superior in magnetic properties, especially magnetic flux density, compared to the normal smooth roll-rolled material.

Example 2゜One continuous casting slab having the composition of perfumes 2 to 4 in Table 2
After heating to 140℃, rough rolling and finish rolling process to 2.0℃
A hot-rolled sheet having a diameter of 1.0 mm was prepared and wound up at 640°C.

Hot-rolled plate annealing was carried out for part of Perfume 2 and Perfume 3.4, and for Perfume 2, the as-rolled material and annealed material, and for Perfume 3.4, the annealed material were subjected to various conditions after pickling. After rolling with fluted rolls and then flattening to 0.5 degrees,
Perfume 2 is 900℃, Perfume 3 is 950℃, Perfume 4 is 960
Final annealing was performed at various temperatures of °C, and the magnetic properties after annealing were measured. In addition, the above hot rolled sheet annealing is performed at 750°C for fragrance adjustment 2;
Perfuming 3.4 was carried out by box annealing (BA) at 850°C. This annealing can also be carried out by continuous annealing on the AP line, etc., and for fragrances 3 and 4, continuous annealing at 950°C (A
P) was also carried out. Also, for perfume 3, 85
Cold rolling was performed twice with intermediate annealing at 0° C. for 3 hours, and warm rolling at a rolling temperature of 300° C. was also performed for perfume adjustment 4. For comparison, similar test materials were rolled using only conventional smooth rolls, and their magnetic properties were measured.

These results are shown in Table 4.

(Wisdom t%)

[Brief explanation of drawings]

FIGS. 1(A) to 1(G) are explanatory diagrams showing the cross-sectional shape of the grooves of the vertically grooved roll. Figure 2 shows the groove pitch Q of the roll,
FIG. 3 is a diagram showing the relationship between groove depth d and magnetic flux density increase amount ΔBso. Figure 3 shows the parameter S/, which represents the size of the vertical groove.
FIG. 3 is a diagram showing the relationship between (ld) and magnetic flux density B, a. FIG. 4 is a diagram showing the relationship between rolling conditions A/S and the amount of increase in magnetic flux density ΔB sn in fluted roll rolling. FIG. 5 is an explanatory diagram showing the groove cross-sectional shape and dimensions of the vertically grooved roll. FIGS. 6(A) to 6(D) are enlarged microscopic photographs showing the cross-sectional metallographic structure of the steel sheet in the C direction after rolling with fluted rolls. FIGS. 7(A) and 7(B) are (200) pole figures showing the rolling textures of the present invention material and the conventional material, respectively. 8th
Figures (A) and (B) are (200) pole figures showing the primary recrystallization texture of the present invention material and the conventional material, respectively. FIGS. 9(A) to 9(F) are diagrams showing textures of a material of the present invention and a conventional material. Pen t aYl-shaped 1.6 blemish V-shaped x 4 with face cut F! 1.0 0 3.0 t S/fl・d 4th Fig. 0.05 08 1 5 8 0 A/S Fig. 5 Fig. D Fig. 7 D Fig. D

Claims (2)

[Claims] (1) In weight%, C: 0.01% or less, Si: 7.0%
Below, Mn: 0.1 to 1.5%, P: 0.15% or less,
S: less than 0.01%, Al: 0.001% or less or 0
．． A hot rolled steel strip having a composition consisting of 0.05 to 1.0%, N: 0.005% or less, the balance Fe and unavoidable impurities is annealed as necessary, with one or intermediate annealing 2
In manufacturing a non-oriented electrical steel sheet by a series of steps of annealing after cold rolling or warm rolling more than once, the cold rolling or warm rolling step does not include the final pass. During rolling in the above rolling passes, the groove pitch l (mm) and groove depth d (mm) in the circumferential direction of the roll surface are 0.5≦( with respect to the initial plate thickness t (mm) of the rolled material. l/t)≦2.5 0.1≦(d/t)≦0.5, and the roll groove cross-sectional area S (mm^2) per groove pitch l in the cross section passing through the roll axis is 0. 15≦[S/(ld)]≦0.65 using a roll in which vertical grooves are arranged at equal intervals in the longitudinal direction of the roll, and rolling in one or more rolling passes including the final pass is carried out. A method for producing a non-oriented electrical steel sheet with excellent magnetic properties, characterized in that the method is carried out using a smooth roll having no vertical grooves. (2) Rolling in the final pass of rolling performed using rolls with vertical grooves is a cross-sectional area A (m
m^2) is the roll groove cross-sectional area S(
Claim (1) characterized in that the process is carried out under the condition that (A/S)≧0.6 is satisfied for mm^2).
A method for producing a non-oriented electrical steel sheet with excellent magnetic properties as described in .