JPH0823045B2 - 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 or warm rolling using upper and lower rolls having longitudinal grooves in the roll circumferential direction.

By the way, the cold rolling technology for magnetic steel sheets using group rolls (grooved rolls) has conventionally produced magnetic steel sheets having a (100) plane cubic texture that combines the characteristics of grain-oriented and non-oriented steel sheets. Has been considered as a possible means to achieve (for example, "Iron and Steel" 63 (1977) P.1828,
P.1838, P.2335, "Iron and Steel" 70 (1984) P.2065). The technical idea is that the width of the steel sheet is extended during cold rolling, so that {100} <011> to {100} <0vw after recrystallization annealing.
> Is to develop a texture. As one based on such a technical idea, for example, Japanese Patent Publication No. 54-10922
And Japanese Patent Publication No. 53-30098 are proposed. However, in these conventional reports, decarburization annealing and refining 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 applies rolling using vertical grooved upper and lower rolls to part of cold rolling or warm rolling. By doing so, the texture formation during rolling can be changed by shifting from the plane strain state in the conventional smooth roll rolling to the deformation state involving the flow of the material in the plate width and plate thickness directions. is there.

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 balance Fe and unavoidable impurities is annealed or not annealed once or twice or more by cold rolling or warming with intermediate annealing. In producing a non-oriented electrical steel sheet by a series of steps of performing annealing after hot rolling, in the cold rolling or warm rolling step, rolling in one or more rolling passes not including the final pass is performed. , The upper and lower rolls have longitudinal grooves formed so as to be arranged at equal intervals in the roll longitudinal direction in the circumferential direction of the roll surface, and the groove shapes of the upper and lower rolls are the same, and the groove pitch l (Mm)
The deviation e (mm) between the upper and lower rolls is (e / l) ≦ 0.25, and the upper and lower rolls are rolled vertically in one or more rolling passes including the final pass. This is done by using a smooth roll having no groove.

Further, in such a method of the present invention, rolling in the final pass using the upper and lower rolls having the vertical groove,
The cross-sectional area A (mm ² ) per groove pitch 1 (mm) of the convex portion of the rolled material after rolling, that is, the steel plate portion flowing into the roll groove by rolling is the cross-sectional area S of the roll groove portion per groove pitch l. It is preferable to carry out under the condition that (A / S) ≧ 0.6 for (mm ² ).

[Action]

Hereinafter, details of the present invention will be specifically described based on experimental results.

A continuous cast slab having the composition shown in Steel A in Table 1
A hot-rolled steel sheet was prepared under the conditions shown in A of Table 2, pickled, and then subjected to roll rolling with flutes, flattening rolling and recrystallization annealing, and the microstructure, magnetic properties and texture were investigated. Roll rolling with vertical grooves is a work in which vertical grooves having the cross-sectional shape shown in FIG. 1 (A) are arranged at equal intervals in the roll circumferential direction on both the upper and lower stages of a 4high cold rolling mill. Using a roll, lubrication was performed at room temperature, and a front / rear tension of a unit of 10 kgf / mm ² was applied, and 1 to 6 pass rolling was performed. At this time, the work roll had a roll diameter of 106φ, the groove shape was the same for both the upper and lower rolls, and the groove portions of the upper and lower rolls were arranged to face each other. In the flattening rolling performed after such roll rolling with vertical grooves, both upper and lower stages were rolled to a sheet thickness of 0.50 mm using smooth rolls (roll diameter 106φ). In this recrystallization annealing after rolling, annealing was carried out at various temperatures of 625 to 850 ° C for a soaking time of 90 seconds.

FIGS. 2 (A) to (F) are photographs showing the cross section (C cross section) metal flow of the above-mentioned double-sided vertical grooved roll rolling 1 to 6 pass material in the direction perpendicular to the rolling direction after grooved roll rolling. According to this, it can be seen that the metal flow in the steel plate C cross section exhibits a waviness corresponding to the roll groove pitch, and the deformed state is obviously different between the steel plate convex portion and the concave portion corresponding to the roll groove portion. In particular, when the number of grooved roll rolling passes is three or more, the metal flow rises vertically in the plate thickness direction in the plate thickness center layer of the steel plate convex portion,
It can be seen that this is significantly different from rolling using only normal smooth rolls.

Fig. 3 (A) shows a microstructure of a steel sheet C section after rolling of a rolled material using only ordinary smooth rolls, and Fig. 3 (B) shows a flattened rolling of the above-mentioned flute-rolled 5-pass rolling material. 3 is a photograph showing the steel sheet C cross-section microstructure of FIG. 4 (A) and (B) are respectively FIG. 3 (A).
It is a photograph showing the microstructure of each steel sheet shown in (B) after annealing at 800 ° C for 90 seconds. As is clear from the photograph of FIG. 3 (B), in the grooved roll rolled material, the irregularities on the surface of the steel sheet after flattening rolling have completely disappeared, but unlike the normal smooth rolled material, as shown in FIG. As shown in the photograph, the large undulations of the metal flow rising vertically in the plate thickness direction due to the grooved roll rolling remain. However, as shown in the photograph of FIG. 4, in the ferrite structure after annealing,
No significant difference is observed between the grooved roll rolled material and the normal smooth rolled material.

FIG. 5 shows the change in the X-ray integrated reflection intensity depending on the annealing temperature. (A) and (B) in the figure show groove-rolled 3-pass material, 5-pass material and normal smooth rolled material on the (200) plane, and (C) and (D) respectively (222).
Regarding the surface, it is shown by comparing a grooved roll rolled 3-pass material and a 5-pass rolled material with a normal smooth rolled material. According to this, the rolled roll with groove has a higher (200) surface strength and a lower (222) surface strength at any stage after rolling, at the initial stage of recrystallization, and after completion of recrystallization, as compared with the ordinary rolled material. ,
Clearly, the organization is different. Especially, the difference is remarkable in the 5-pass material having a high rolling reduction in the grooved roll rolling.

Next, Table 3 shows the measurement results of the magnetic properties after annealing at 800 ° C. According to this, the vertical grooved roll rolled material has improved magnetic properties, particularly the magnetic flux density, compared to a normal smooth roll rolled material, the number of rolling passes of the grooved roll rolling increases, and the higher the rolling reduction, It can be seen that the improvement of the magnetic flux density is remarkable. As described above, the effect of improving the magnetic properties by the fluted roll rolling is that, in the fluted rolling material with the fluting as described above, the deformation behavior at the time of rolling is different from the deformation behavior of the smooth rolling material, so that the rolling texture is It is presumed that this is due to the formation of a primary recrystallized texture that changes into a shape different from that of the normally rolled material and is favorable for magnetic properties.

The present invention has been made based on the above experimental results. The reasons for limiting the configuration of the present invention will be described below.

 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 step is extremely important, and a part of this rolling is formed in the circumferential direction of the roll surface at equal intervals in the longitudinal direction of the roll. It is characterized by using upper and lower rolls having vertical grooves.

In the present invention, it is essential that the roll grooves used in the grooved roll rolling are formed in the roll circumferential direction and arranged at equal intervals in the roll longitudinal direction. In order to form the above-mentioned large waviness of the metal flow in the plate width direction during the grooved roll rolling and the flattening rolling, the grooves on the roll surface must be longitudinal grooves in the roll circumferential direction. 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 the plate is rolled by a roll having such grooves intersecting each other, the transferred convex portion is crushed by friction with the roll during flattening rolling, and a minute 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.

Further, it is preferable that the vertical grooves of the upper and lower rolls have the same cross-sectional shape and groove pitch. If the groove shape and groove pitch of the upper and lower rolls are greatly different, the magnetic properties of the final product may change depending on the widthwise position of the steel plate, as in the case where the arrangement of vertical grooves in the roll longitudinal direction is irregular. It is not preferable because it will impair the uniformity of magnetic properties.

Further, the positional relationship between the upper and lower rolls when passing the steel plate is extremely important, and it is ideal that the groove portions of the upper roll and the lower roll are exactly opposite to each other. However, in reality, some deviation may occur between the upper and lower rolls.

Therefore, the upper and lower rolls used for double-sided grooved roll rolling are intentionally displaced left and right with respect to the rolling direction.
(Mm) (e ≦ l, l: vertical groove pitch (mm)) was applied, rolling was performed, and the magnetic properties after flattening rolling and annealing were investigated. The sectional shape of the vertical groove of the work roll used at this time is shown in FIG. 1 (B). The test material has the composition of Steel B in Table 1,
And after pickling the hot rolled steel sheet rolled under the condition of B in Table 2,
Rolled with double-sided vertical groove for 4 passes, then 0.5mm
It was annealed at 800 ° C after flattening and rolling. Up·
The ratio e / l of the deviation e between the lower rolls to the vertical groove pitch l,
FIG. 6 shows the relationship between the magnetic flux density B ₅₀ of the double-sided grooved roll rolled material and the amount of increase ΔB ₅₀ with respect to the normal smooth roll rolled material B ₅₀ . According to this, it can be seen that ΔB ₅₀ is the largest when e / l≈0, and ΔB ₅₀ decreases as e / l increases. If e / l = 0.5, that is, if there is a gap between the upper and lower rolls for half the pitch of the vertical groove, the steel plate becomes a corrugated plate in the width direction due to roll rolling with vertical grooves, and subsequent flattening rolling. At times, plate cracks are likely to occur, which is not preferable from the perspective of passing the plate. For the above reasons, in the present invention (e /
l) Defined as ≤0.25.

In the present invention, the groove cross-sectional shape of the roll used in the vertical grooved roll rolling is not particularly specified. Cross section is V
Sufficient effect can be observed in any of the shapes, U-shape, trapezoid, sine wave, and the like. Further, as will be apparent from the examples described below, the action and effect thereof vary depending on the groove pitch and the groove depth, but under any condition, the effect of improving the magnetic flux density is recognized as compared with the ordinary smooth roll rolled material. However, if the preferable conditions are limited in relation to the effect, the groove pitch 1 and the groove depth d are 0.5 ≦ (l / t) ≦ 2.5 with respect to the initial plate thickness t of the rolled material, respectively. It is preferable that 0.1 ≦ (d / t) ≦ 0.5.

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 the warm rolling step is required to be performed by using the smooth rolls for both the upper and lower rolls in order to completely eliminate the unevenness of the steel sheet surface, but other The combination of the fluted roll rolling and the flattening rolling for the rolling pass is arbitrary, and even if the fluted roll rolling and the flattening rolling are alternately repeated, or after performing the fluted rolling for several passes, the flattening is performed. Chemical rolling may be carried out.

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 rolling using vertical grooved rolls for the upper and lower rolls, the rolling conditions are variously changed, and the groove pitch of the convex part of the material to be rolled after the final grooved roll, that is, the part that has flowed into the roll groove The ratio A / S of the cross-sectional area A (mm ² ) per 1 to the roll groove cross-sectional area S (mm ² ) per groove pitch l,
We investigated the relationship between the normal increase amount .DELTA.B ₅₀ for rolled material of the magnetic flux density B _50. The results are shown in FIG. In this test example, the conditions other than the rolling conditions of the fluted roll rolling (test material, groove cross-sectional shape, annealing conditions, etc.) were the same as those in the test example of FIG. From the results shown in FIG. 7, 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 performing cold rolling or warm rolling two or more times with intermediate annealing, it suffices to perform flattening rolling in one or more passes including the final pass, that is, the final pass of the final rolling. There are no particular restrictions on other paths.

[Example] Table 4 shows the chemical composition of the test steel.

Each of the test steels was melted in a converter, decarburized to a predetermined carbon content in an RH degassing facility, and then continuously cast into a 200 mm ^t slab. After heating the slab to 1200 ° C. for steel No.-1 and 1140 ° C. for steel Nos. 2 to 4, a rough rolling and finish rolling process was performed to obtain a hot rolled sheet of 2.0 mm ^t. Winding was performed at 700 ° C., and for steel Nos. 2 to 4 at 640 ° C.

Part of Steel No.-2 and Steel Nos.-3 and 4 were subjected to hot-rolled sheet annealing. Steel No.-1 was as-wound material, Steel No.-2 was as-wound material and annealed material, Steel No.-3. In No. 4, the annealed material was subjected to scale removal by pickling, and then subjected to warm rolling (0.5 mm ^t ) until cold as specified in the present invention,
The magnetic properties after the final annealing were measured. The hot-rolled sheet was annealed at 750 ° C for steel-2 and at 850 ° C for steel-3 and 4 using box annealing (BA). This annealing can also be performed by continuous annealing such as AP line, and in Steels-3 and 4, continuous annealing (AP) at 950 ° C was also performed. For comparison, a steel strip obtained by performing cold rolling only with a conventional smoothing roll for the same sample material, and e / l were subjected to longitudinal grooved roll rolling under conditions outside the scope of the present invention. The magnetic properties of the steel sheet thus obtained were also measured.

 The results are shown in Tables 5 and 6.

Among them, in Example- (I) shown as Table 5, a 5-stand continuous rolling mill is used for cold rolling or warm rolling, and in the present invention example, double-sided vertical grooves are used in No. 1 to No. 3 stands. No. 4 and No. 5 stand smooth rolls were used for flattening rolling.

Further, in Example- (II) shown as Table 6, the same 5-stand continuous rolling mill was used, but in this Example, the groove shape of the fluted roll, the number of passes of the fluted roll rolling, and the rolling reduction were performed. Cold rolling was carried out at different rates.

Further, cold pressing was performed twice using Steel No.-3, and its effect was also confirmed. The results are shown in Table 7 as Example- (III).

In this Example- (III), after the slab of steel No. 3 was formed into a hot-rolled sheet under the same conditions as described above, the hot-rolled sheet was annealed, and the scale was removed by pickling. Under the conditions specified by 1), cold pressure was performed twice with intermediate annealing, and the magnetic properties after the final annealing were measured. Further, in this example, cold rolling was carried out by a 5-stand continuous rolling mill and a single-stand reverse rolling mill.

As is clear from Table 7, the same effect as in the single cold pressing method is recognized in the double cold pressing method.

[Brief description of drawings]

FIGS. 1 (A) and 1 (B) are explanatory views showing the groove cross-sectional shape of a roll having vertical grooves. 2 (A) to (F) are microscopic enlarged photographs showing the metal structure of the steel sheet C-direction cross section after roll rolling with flutes. FIGS. 3 (A) and 3 (B) are microscopic enlarged photographs showing the metal structures of the steel sheet in the C-direction cross section, respectively, after the conventional rolling and after the longitudinal grooved roll rolling and the flattening rolling of the method of the present invention. FIGS. 4 (A) and 4 (B) are microscopic enlarged photographs showing the metal structures of the C-direction cross section after recrystallization annealing of the steel sheet by the conventional method and the method of the present invention, respectively. FIG. 5 (A)-
(D) is a figure which shows the texture of the steel plate by this invention method and the conventional method. Fig. 6 shows the relationship between the position deviation e / l between the upper and lower rolls with fluted rolls and the increase in the magnetic flux density of the fluted roll with fluting (the amount of increase with respect to the magnetic flux density of the conventional material). It is a graph shown. FIG. 7 is a graph showing the relationship between the rolling condition A / S in the fluted roll rolling and the magnetic flux density increase amount of the fluted roll rolled material (the increase amount with respect to the magnetic flux density of 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 of both upper and lower rolls has longitudinal grooves formed so as to be arranged at equal intervals in the roll longitudinal direction in the circumferential direction of the roll surface, and the cross-sectional shape of the grooves of the upper and lower rolls is Same as above, gap between upper and lower rolls with groove pitch l (mm) e (m
m) is performed using a roll satisfying (e / l) ≤ 0.25, and rolling in one or more rolling passes including the final pass is performed using smooth rolls having no vertical grooves for both upper and lower rolls. A method of manufacturing a non-oriented electrical steel sheet having excellent magnetic properties, which is characterized by the following. 2. A cross-sectional area A (mm ² ) per groove pitch 1 (mm) of a steel sheet portion flowing into the roll groove by the rolling in the final pass using upper and lower rolls having vertical grooves.
Is performed under the condition that (A / S) ≧ 0.6 with respect to the cross-sectional area S (mm ² ) of the roll groove portion per groove pitch 1 is satisfied.
The method for producing a non-oriented electrical steel sheet having excellent magnetic properties according to 1.