JPH03267318A - Production of nonoriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To improve magnetic flux density by applying rolling by means of longitudinally grooved upper and lower rolls to a part of rollings prior to the annealing of a hot rolled plate. 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 the upper and the lower roll which has longitudinal grooves formed in a manner to be arranged so that they are equally spaced in the longitudinal direction of the roll in the peripheral direction of the roll surface and in which respective sectional forms of the grooves in the upper and the lower roll are identical and the deviation (e)(mm) of a groove pitch (l)(mm) between the upper and the lower roll satisfies an inequality. Then, rollings in one or more passes including the final pass are carried out by using smooth rolls as the upper and the lower 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 or warm rolling using upper and lower rolls having vertical grooves in the circumferential direction of the rolls.

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 exuding the steel plate during cold rolling, the (100 ) <011) ~(100)
The aim is to develop a texture of <Ovw). Based on such a technical idea, for example, Japanese Patent Publication No. 10922/1982 and Japanese Patent Publication No. 30098/1984 have been proposed. However, 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) is 0.03%, Si: ~3%, M
n: ~0.2%, S>0.01%, Al: ~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 such current circumstances, the present invention aims to improve the magnetic flux density of non-oriented electrical steel sheets, and applies rolling using upper and lower rolls with vertical grooves to a part of cold rolling or warm rolling. By doing so, the texture formation during rolling is changed from the plane strain state in conventional smooth roll rolling to a deformed state accompanied by material flow in the sheet width and sheet thickness directions. be.

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: 0.0
Less than 1%, Al2 0.001% or less or 0.05-1
．． 0%, N: 0.005% or less.

A hot-rolled copper strip having a composition consisting of the remainder Fe and unavoidable impurities is annealed as necessary, cold-rolled or warm-rolled once or twice or more with intermediate annealing, and then annealed. In manufacturing a non-oriented electrical steel sheet through a series of steps, in the cold rolling or warm rolling step, rolling in one or more rolling passes not including the final pass is carried out to improve the rolling surface of both the upper and lower rolls. It has vertical grooves arranged in the circumferential direction at equal intervals in the longitudinal direction of the roll, and the cross-sectional shapes of the grooves on the upper and lower rolls are the same, and the groove pitch between the upper and lower rolls is Q (m). Rolling is carried out using rolls whose deviation e satisfies Ce/Q) ≦ 0.25, and rolling in one or more rolling passes including the final pass is carried out using smooth rolls that do not have vertical grooves for both the upper and lower rolls. The reason is that this is done using the .

In addition, in such a method of the present invention, the rolling in the final pass using the upper and lower rolls having the above-mentioned longitudinal grooves is carried out using the convex portion of the rolled material after this rolling, that is, the rolling material flows into the roll groove due to rolling. Under the condition that the cross-sectional area A (m2) per groove pitch Q (m) of the steel plate portion satisfies (A/S)≧0.6 with respect to the roll groove cross-sectional area 5 (nu”) per groove pitch Q It is preferable to do so.

[For production]

The details of the present invention will be specifically explained below based on experimental results.

A continuous casting slab having the composition shown in #RA in Table 1,
A hot-rolled copper strip was prepared under the conditions shown in A of Table 2, and after pickling, it was subjected to fluted roll rolling, flattening rolling, and recrystallization annealing, and its microstructure, magnetic properties, and texture were investigated. For rolling with vertically grooved rolls, vertical grooves having the cross-sectional shape shown in FIG. Using work rolls, lubricated at room temperature, and unit 10kgf.
The work rolls at this time had a roll diameter of 106 lI, the groove shape was the same on both the upper and lower rolls, and the upper and lower rolls had the same groove shape. The grooves were arranged so as to face each other.In the flattening rolling performed after rolling with such vertically grooved rolls, the upper and
Both lower rows were rolled to a plate thickness of 0.50+e using smooth rolls (roll diameter 106 mm). Further, in the recrystallization annealing after this rolling, annealing was performed at various temperatures of 625 to 850°C for a soaking time of 90 seconds.

FIGS. 2(A) to 2(F) are photographs showing metal flow in a cross section perpendicular to the rolling direction (cross section C) after the grooved roll rolling of the above-mentioned double-sided grooved roll rolling material for 1st to 6th passes. According to this, the metal flow of steel plate C cross section is as follows.

It exhibits undulations that correspond to the roll groove pitch, and
It can be seen that the deformation states are clearly different between the convex portions and concave portions of the steel plate corresponding to the roll grooves.

In particular, when the number of rolling passes with the grooved roll is 3 or more,
It can be seen that in the thickness center layer of the steel sheet convex portion, the metal flow rises perpendicularly to the sheet thickness direction, which is significantly different from rolling using only ordinary smooth rolls.

Figure 3 (A) shows the cross-sectional microstructure of steel plate C after rolling of the rolled material using only ordinary smooth rolls, and Figure 3 (B)
These are photographs showing the cross-sectional microstructure of the steel plate C after flattening rolling of the above-mentioned longitudinally grooved roll-rolled 5-pass material. Also, Figures 4(A) and (B) are respectively similar to Figures 3(A) and (B).
3 is a photograph showing the microstructure of each steel plate shown in FIG. 1 after soaking at 800° C. for 90 seconds. As is clear from the photograph in Fig. 3 (B), the unevenness on the surface of the steel sheet after flattening rolling has completely disappeared in the grooved roll-rolled material, but unlike the normal smooth roll-rolled material, as shown in Fig. 2. As shown in the photo, the large undulations of the metal flow that rise perpendicularly to the plate thickness direction due to rolling with grooved rolls remain. However, as shown in the photograph of FIG. 4, in the ferrite structure after annealing, no significant difference is recognized between the grooved roll-rolled material and the normal smooth roll-rolled material.

FIG. 5 shows changes in the integrated X-ray reflection intensity depending on the annealing temperature. The same figures (A) and (B) respectively show the grooved roll-rolled 3-pass material, 5-pass material and the normal smooth roll-rolled material on the (200) plane, and (C) and (D) respectively show the (22
2) Comparison of grooved roll-rolled 3-pass material, 5-pass material and normal smooth roll-rolled material is shown.

According to this, the grooved roll-rolled material has higher (200) plane strength and lower (222) plane strength at all stages after rolling, at the initial stage of recrystallization, and after the completion of recrystallization, compared to normally rolled material. , the collective organization is clearly different. The difference is particularly noticeable in the 5-pass material, which has a high rolling reduction with grooved rolls.

Next, Table 3 shows the measurement results of magnetic properties after annealing at 800°C. According to this, the magnetic properties, especially the magnetic flux density, of vertically grooved roll-rolled materials are improved compared to ordinary smooth roll-rolled materials, and as the number of rolling passes of grooved roll rolling increases and the rolling reduction ratio increases, It can be seen that the improvement in magnetic flux density becomes remarkable. This effect of improving magnetic properties due to vertically grooved roll rolling is due to the fact that the deformation behavior of vertically grooved roll rolled materials during rolling is different from that of normal smooth roll rolled materials. This is presumed to be due to the formation of a primary recrystallized texture that is favorable for magnetic properties and changes into a shape different from that of a normally rolled material.

The present invention was made based on the above experimental results. The reasons for limiting the configuration of the present invention will be explained below.

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.

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, 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 Sj, 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 i 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 Al that causes such problems is more than 0.001% to 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 0.0
0.01% 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.

The present invention includes a series of steps in which a hot rolled steel strip having the above composition is annealed as necessary, cold rolled or warm rolled once or twice or more with intermediate annealing, and then annealed. Non-oriented electrical steel sheets are produced by the above-mentioned cold rolling or warm rolling process, and a part of this rolling is formed so as to be arranged at equal intervals in the circumferential direction of the roll surface in the longitudinal direction of the roll. It is characterized by the use of upper and lower rolls having vertical grooves.

In the present invention, it is essential that the roll grooves used for rolling with a grooved roll 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 sheet width direction as described above 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.

Further, it is preferable that the cross-sectional shape and groove pitch of the vertical grooves of the upper and lower rolls are the same. If the groove shapes and groove pitches of the upper and lower rolls are significantly different, the magnetic properties of the final product may change depending on the widthwise position of the steel plate, similar to when the vertical grooves are irregularly arranged in the longitudinal direction of the rolls. This is not preferable because it impairs the uniformity of magnetic properties.

Furthermore, the positional relationship between the upper and lower rolls when passing the steel sheet is extremely important, and ideally the grooves of the upper and lower rolls should accurately face each other.

However, in reality, some misalignment may occur between the upper and lower rolls.

Therefore, the upper and lower rolls used for rolling with double-sided grooved rolls are intentionally misaligned left and right with respect to the rolling direction.
) (e≦Q, Q: longitudinal groove pitch (, )), and the magnetic properties after flattening rolling and annealing were investigated. Figure 1 (B
). The test material was a hot-rolled steel plate having the composition of steel B in Table 1 and rolled under the conditions of B in Table 2. After pickling, the hot rolled steel plate was subjected to four passes of roll rolling with vertical grooves on both sides, and then .5++
It was flattened and rolled to w++ and then annealed at 800°C. The ratio e/Q of the deviation e between the upper and lower rolls to the vertical groove pitch Q, and the magnetic flux density Bs of the rolled material with grooves on both sides
Increase amount ΔB with respect to B5° of normal smooth roll rolled material of 0
The relationship between 5° and 5° is shown in Figure 6. According to this, e/
When fl'=O, ΔBs1l+ is the largest, and e/
It can be seen that as Q becomes larger, ΔB5° becomes smaller. In addition, if e/Q = 0.5, that is, if there is a misalignment between the upper and lower rolls by half the period of the vertical groove pitch, the steel plate will become a wavy plate in the width direction due to rolling with the vertical groove rolls, and the steel plate will become a wavy plate in the width direction. The plate tends to crack during hard rolling, which is also undesirable from the perspective of sheet threading. For the above reasons, the present invention defines (e/Q)≦0.25.

In the present invention, the groove cross-sectional shape of the roll used in the fluted roll rolling is not particularly defined. The cross-sectional shape is V-shaped.
Sufficient effects are observed in any of the U-shaped, trapezoidal, and sinusoidal waveforms. In addition, as will be clear from the examples described below, the effect changes depending on the groove pitch and groove depth.
Under all conditions, the effect of improving magnetic flux density is observed compared to ordinary smooth roll rolled material. However, if we dare to limit suitable conditions in relation to this effect, the groove pitch Q and the groove depth d are each 0.5≦(Q/l)≦ with respect to the initial plate thickness t of the rolled material. 2.5.0.1≦(d/l)≦
Preferably it is 0.5.

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.

In addition, in the present invention, the final pass of rolling in the cold rolling or warm rolling process must be carried out using smooth rolls for both the upper and lower 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 the rolling pass is arbitrary;
The fluted roll rolling and flattening rolling may be repeated alternately, or the flattening rolling may be performed after several passes of the fluted rolling.

However, in order to make the effects of the present invention more pronounced, the final pass of rolling using the fluted rolls is preferably carried out under specific rolling conditions. Up·
In rolling using a vertically grooved roll as the lower roll, the rolling conditions are varied, and the groove pitch per Ω of the convex part of the rolled material after rolling with the final grooved roll, that is, the part that flows into the roll groove. The ratio A/ of the cross-sectional area A (m+”) of
S and magnetic flux density B. Increase amount ΔB compared to normally rolled material
5゜Which relationship did you investigate? The results are shown in FIG. In this test example, the conditions other than the rolling conditions for longitudinally grooved roll rolling (sample material, groove cross-sectional shape, annealing conditions, etc.) were the same as the test example shown in FIG. 6. From the results shown in Figure 7, A/
It can be seen that the effect of the present invention becomes extremely significant when rolling conditions are such that 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 or warm rolling is performed two or more times with intermediate annealing in between, flattening rolling may be performed in one or more passes including the final pass, that is, the final pass of the final rolling. There are no particular limitations on other paths.

No. 1 table (V1%) No. table No. table 〔Example〕 The chemical composition of the test steel is shown in Table 4.

All of the sample steels were melted in a converter furnace, decarburized to a predetermined carbon content in an RH degassing facility, and then continuously cast into slabs of 200 mm. Perfume the slab-1 for 1200
After heating to 1140°C for both numbers -2 to 4, it is made into a 2.0111 t hot-rolled plate through rough rolling and finish rolling processes, and for perfume-1 to 700°C, to 1140°C, and for perfume-2 to 4. The winding was performed at 640°C.

Hot-rolled plate annealing was carried out for a part of Perfume-2 and Perfume-3 and 4, Perfume-1 is the as-rolled material, Perfume-2 is the as-rolled material and annealed material, Perfume-3 is the as-rolled material. , 4, the annealed materials were each subjected to scale removal by pickling, and then subjected to cold or warm rolling (0.5 m+t) specified by the present invention, and the magnetic properties after final annealing were measured. The hot rolled sheet annealing was carried out at 750°C for Steel-2 and at 850°C for Steels-3 and 4 using box annealing (BA). This annealing can also be carried out by continuous annealing such as an AP line, and for Steels-3 and 4, continuous annealing (AP) at 950°C was also carried out. In addition, for comparison, steel plates obtained by cold rolling using only conventional smooth rolls using similar test materials, and steel plates obtained by rolling with fluted rolls under conditions where e/Q is not specified in the present invention. The magnetic properties of the steel sheets obtained were also measured.

The results are shown in Tables 5 and 6.

Among these, in Example-(1) shown in Table 5, a 5-stand continuous rolling mill was used for cold rolling or warm rolling,
In the example of the present invention, rolling with rain surface fluted rolls was carried out in stands &1 to &3, and flattening rolling with smooth rolls was carried out in stands Nα4 and Ha5.

In addition, in Example-(II) shown in Table 6, a 5-stand continuous rolling mill was also used, but in this example, the groove shape of the fluted roll, the number of passes of the fluted roll rolling, the rolling reduction Cold rolling was carried out at different rates.

In addition, cold pressing was performed twice using Perfume-3, and its effects were also confirmed. The results are shown in Table 7 as Example-(I[[).

In this Example-(III), the slab of Perfume-3 was made into a hot-rolled plate under the same conditions as described above, and then the hot-rolled plate was annealed and scale removed by pickling. Cold pressing was performed twice with an intermediate annealing under the conditions specified by the above, and the magnetic properties after the final annealing were measured. Further, in this example, cold rolling was carried out using a 5-stand continuous rolling mill and a jingle-stand reverse rolling mill.

As is clear from Table 7, even in the double cold pressing method, 1
The same effect as the re-cooling pressure method is observed.

Table 4 Example-(1) Rolling conditions for fluted rolls using a 5-stand continuous rolling mill O Stands using fluted rolls: 1 to 3 stands. Roll with vertical grooves Double trapezoidal groove shape (Fig. 1-8) Groove depth: 0.58mm Groove spacing: 3. Omm. Cold rolling fluted roll Rolling conditions 0 Stands using fluted rolls: 1 to 3 stands. Vertical grooved roll: (same as above) O rolling temperature: 300℃

[Brief explanation of drawings]

FIGS. 1A and 1B are explanatory diagrams showing the cross-sectional shape of the grooves of the vertically grooved roll. FIGS. 2(A) to 2(F) are enlarged microscopic photographs showing the metal structure of a cross section in the C direction of the steel plate after rolling with a fluted roll. FIGS. 3(A) and 3(B) are enlarged microscopic photographs showing the metal structure of a cross section in the C direction of a steel plate after rolling by the conventional method and after rolling with fluted rolls and flattening rolling by the present invention, respectively. FIGS. 4(A) and 4(B) are enlarged microscopic photographs showing the metal structure of a cross section in the C direction after recrystallization annealing of steel sheets by the conventional method and the method of the present invention, respectively. Figure 5 (A)-(D
) is a diagram showing the texture of steel sheets produced by the method of the present invention and the conventional method. Figure 6 shows the positional deviation e/Q between the upper and lower rolls of vertically grooved roll rolling and the increase in magnetic flux density of the vertically grooved roll rolled material (increase relative to the magnetic flux density of conventional material).
It is a graph showing the relationship between Figure 7 shows the rolling conditions A/S in fluted roll rolling and the increase in magnetic flux density of the fluted roll rolled material (increase relative to the magnetic flux density of conventional material).
It is a graph showing the relationship between e/1 (/1) Cooking temperature (τ) Cooking temperature (9C) Figure (C) Cooking temperature (0C) Smoking degree (IIC)

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. Rolling in the above rolling passes is carried out by using a method in which both the upper and lower rolls have longitudinal grooves arranged in the circumferential direction of the roll surface at equal intervals in the longitudinal direction of the rolls, and the cross-sectional shape of the grooves of the upper and lower rolls. is the same, the groove pitch l (mm) and the deviation e (mm) between the upper and lower rolls satisfy (e/l)≦0.25, and one or more passes including the final pass are carried out. A method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties, characterized in that rolling in the rolling pass is performed using smooth rolls having no longitudinal grooves for both the upper and lower rolls. (2) Rolling in the final pass using upper and lower rolls having vertical grooves is performed using the cross-sectional area A (mm^2
) is the cross-sectional area of the roll groove per groove pitch l (mm^
2), claim (1) is characterized in that it is carried out under the condition that (A/S)≧0.6 is satisfied.
A method for producing a non-oriented electrical steel sheet with excellent magnetic properties as described in .