JPH0819464B2 - 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.

[Conventional technology and problems to be solved]

Heretofore, various manufacturing techniques have been disclosed 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 at the time of subsequent annealing by optimizing the cold pressure ratio, the cold pressure, the annealing twice or more Techniques such as selection of a texture that is preferable in terms of magnetic properties by carrying out the method are known, but in reality, none of them has sufficient improvement effects.

[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 upper-side 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.82.
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} <0 after recrystallization annealing.
It is to develop the texture of vw>. 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: 20ppm)
Judging from the above, it is clearly aimed at controlling the secondary recrystallization texture. On the other hand, heretofore, no example has been found in which application of flute roll rolling to control the superposition structure 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 the state of plane strain in the conventional flat rolling to the state of deformation accompanied by widening of the width.

That is, the feature of the present invention is that, in% by weight,
C: 0.01% or less, Si: 0.1 to 7.0%, Mn: 0.1 to 1.5%, P: 0.1
% Or less, S: less than 0.01%, Al: 0.001% or less or 0.05 to 1.
0%, N: 0.005% or less, hot-rolled steel strip having a composition consisting of balance Fe and unavoidable impurities, or without annealing, at least once, or cold-rolled at least two times with intermediate annealing or warm When manufacturing a non-oriented electrical steel sheet by performing annealing after rolling, in the cold rolling or warm rolling, rolling in one or more rolling passes not including the final pass is performed in the roll circumferential direction. This is because the roll having the flutes is used, and the rolling in one or more rolling passes including the final pass is performed using the smooth roll having no flutes.

In addition, in the present invention as described above, it is preferable that the above-described rolling with flutes is performed under the conditions that satisfy the following formula.

However, Ai: vertical groove pitch l after rolling of the i-th vertical grooved roll
Cross-sectional area of the rolled material per hit (mm ² ) A′i: Cross-sectional area per groove pitch l of the rolled material that has flowed into the roll groove after the i-th roll with longitudinal groove roll (mm ² ) l : Pitch of vertical groove (mm) t: Initial plate thickness of rolled material (mm) [Operation] In order to clarify the operation and effect of the present invention, the following experiment was conducted using a laboratory cold rolling mill. It was

After hot rolling the slabs of the components shown in Table 1 under the conditions shown in Table 2, the following steps for the hot-rolled sheet were carried out:
Flute roll rolling-smoothing rolling-annealing was performed, and the metal flow by flute roll rolling at this time, the cross-sectional microstructure after flattening rolling and after final annealing, the texture after final annealing, and the magnetic properties were determined. Examined. The results are shown in FIGS. 1 to 4. In roll rolling with vertical grooves,
A roll having a groove shape as shown in the figure was used.

In this experiment, the following effects were recognized by carrying out roll rolling with vertical grooves and flattening rolling.

The photograph shown in FIG. 1 shows a steel plate C after roll rolling with vertical grooves.
It shows the metal flow of the direction cross section, (A) ~ (D)
The pictures of the rolls with vertical groove are 1 pass, 2 passes,
The steel plate C direction cross section at the time of performing 3 passes and 4 passes is shown. According to this, by the roll rolling with vertical grooves, the metal flow in the cross section in the steel sheet C direction exhibits waviness corresponding to the groove pitch for each pass, and becomes more complicated waviness as the number of passes increases.

The photographs (A-1) to (D-1) in FIG. 2 show the steel sheet cross-sectional microstructures after the steel sheets (A) to (D) in FIG. 1 are flattened and rolled by a smooth roll. ing. According to this, the unevenness on the surface of the steel sheet as shown in FIG. 1 has completely disappeared by the flattening rolling. However, the waviness of the metal flow due to the fluted roll rolling remains even after the flattening rolling, which is clearly different from the conventional cold rolling structure.

The photographs of FIGS. 2 (A-2) to (D-2) show the microstructures of the steel sheets shown in FIGS. 2 (A-1) to (D-1) after the final annealing. Further, FIG. 3 shows the texture of the final annealing. (I) is the one-pass vertical roll rolling (unlubricated, lubricated), then the flattening rolling, (I
I) is a 4-pass vertical grooved roll rolling (no lubrication, lubrication),
It has been flattened and rolled. For comparison, the texture obtained by rolling with only smooth rolls (conventional method)
I). Further, FIG. 4 shows the effects of the number of passes, rolling temperature, and lubrication of the fluted roll rolling on the magnetic flux density of the steel sheet subjected to fluted roll rolling-flattening rolling-annealing.

According to these, first, FIG. 2 (A-2) to (D-
As shown in 2), no significant difference in the ferrite structure is observed after annealing. However, as shown in FIG. 3, on the recrystallized structure, the addition of fluted roll rolling shifts the accumulation in the vicinity of (111) <112> to the accumulation of the {100} <uvw> system. And regarding the magnetic characteristics after annealing,
As shown in FIG. 4, a significant improvement in magnetic flux density is recognized by adding roll rolling with flutes. The degree is more remarkable in warm rolling than in cold rolling and lubrication rather than non-lubrication. Further, although it depends on the rolling conditions, the effect of the fluted roll rolling is greatest when the rolling is performed in 2 to 4 passes.

As shown in FIG. 4, the number of passes of roll rolling with flutes has a preferable range for obtaining a good magnetic flux density, and the effect of the present invention can be more concretely achieved together with the rolling temperature and the lubricating condition. Is an important process factor for The number of passes essentially regulates the total reduction amount by roll rolling with longitudinal grooves. From the results shown in FIG. 6, when the groove pitch is l and the original thickness of the material to be rolled is t, The total cross-sectional area Ai of the material to be rolled evaluated by the unit groove pitch l in the strip width direction after each longitudinal grooved roll rolling (each pass) and the cross-sectional area A'i of the material (convex portion) flowing into the roll groove at that time Stipulated by And elongation rate εi with respect to the length of the original plate in each longitudinal groove rolling process. Derived from and Sum of, When is within the following range, the effect of the present invention is remarkably exhibited.

Further, as described above, it is most preferable to perform the longitudinal groove rolling with lubrication and to perform the warm rolling (usually 400 ° C. or less) in order to improve the magnetic flux density.

 Next, the reasons for limiting the steel components of the present invention will be described.

C: The present invention maximizes the advantages of performing steelmaking decarburization, and on top of solving the problem of structure formation of cold rolled magnetism, C is the 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 present invention is a technology that should be applied to high Si electrical steel sheets in which reduction in magnetic flux density is a problem. Therefore, it is more effective for the steel type in the ferrite single phase region in the composition of (Si + Al) content of about 1.6% or more. However, the technology of the present invention is
Practically effective regardless of the Si content, and therefore 0.1%
Is its lower limit. Regarding the upper limit, it is a technology that can be applied to all in the range of practical Si amount, but S exceeding 7.0%
In addition to the difficulty of the manufacturing method, the i-amount steel has no merit regarding the utilization technology, and therefore 7.0% is set as the upper limit of Si in the present invention.

Al: Al, like Si, is a ferrite stabilizing element, and when added alone, it becomes an α single phase composition at about 2.0%. The present invention is a technology that is substantially effective for (Si + Al) 1.6% steel, and its upper limit is defined as 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, in a non-oriented electrical steel sheet, when a trace amount of Al is added, finely precipitated AlN hinders grain growth during final annealing and causes 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%, and it is essential that the present invention does not include the amount of Al in this range. For the above reasons, Al is 0.001% or less or 0.05 ~
Specified as 1.0%.

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 0.1%, S0.01%, N0.005%.

In the present invention, the groove shape of the roll used in the longitudinal grooved roll rolling is not particularly specified. As will be apparent from the examples described below, the action and effect thereof vary depending on the cross-sectional shape of the groove, the interval, and the groove depth, but compared to the conventional flat rolled material, the effect of improving the magnetic flux density is recognized under any condition. Because it will be done.

However, if the preferable conditions are limited in relation to the effect, the longitudinal groove of the roll has a groove pitch of 15 mm and a groove depth.
0.3 mm is preferable.

If the groove pitch exceeds 5 mm, the pitch will be more than double the hot-rolled plate thickness (1.6 to 2.5 mm) of general electromagnetic steel plates, and the waviness of the metal flow will be uniform and periodic in the plate width direction. It becomes difficult to introduce by fluting roll rolling. If the groove depth is less than 0.3 mm, it becomes difficult to generate significant metal flow waviness as compared with rolling with smooth rolls. As a result, in any case, the effect of the present invention cannot be sufficiently exhibited.

The cross-sectional shape of the groove can be a V-shaped, U-shaped, trapezoidal, sinusoidal waveform, or any other suitable effect.

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

As described above, in the conventionally proposed structure technology of the electrical steel sheet having the (100) plane three-dimensional texture, there are rolls having longitudinal grooves and transverse grooves, or two intersecting directions angled 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.

The cold rolling in the method of the present invention is not limited to tandem rolling, but can also be carried out by reverse rolling. Even when performing cold pressing twice or more with intermediate annealing, it is sufficient to perform flattening rolling in one or more passes including the final pass, that is, the final pass of the final cold pressure. Is not particularly limited.

〔Example〕

In order to confirm the action and effect of the present invention, an actual machine test was conducted under the following conditions. Table 3 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. For the steel slab, the steel slab-1 was heated to 1200 ° C and steel slab-2.
For ~ 4, after heating to 1140 ℃, through rough rolling and finish rolling process, hot rolled 2.0 mm ^t sheet, steel No.-1 700
For steel Nos. 2 to 4, winding was performed 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. No. 4 of the annealed material was subjected to scale removal by pickling, and then subjected to cold rolling (0.5 mm ^t ) specified by the present invention to measure the magnetic properties after the final annealing. Note that the above hot-rolled sheet annealing is 75 for Steel-Z.
0 ° C, Steel-3, 4 were carried out at 850 ° C using box annealing (BA). This annealing can be performed by continuous annealing such as AP line, and for steel-3 and 4, continuous annealing at 950 ° C (AP)
Was also conducted. For comparison, cold rolling was performed on the same test material using only a conventional smoothing roll, and the magnetic properties of these steel sheets were also measured.

 The results are shown in Tables 4 and 5.

Of these, in Example- (I) shown as Table 4, a 5-stand continuous rolling mill is used for cold rolling or warm rolling, and in the present invention example, No. 1 to No. 3 stands are provided with vertical grooves. Row rolling was performed, and flattening rolling was performed using smooth rolls on No. 4 and No. 5 stands.

Further, in Example- (II) shown as Table 5, the same 5-stand continuous rolling mill was used, but in this Example, the groove shape of the fluted roll and the number of passes of the fluted roll were changed. Rolling was carried out.

In addition, in the present example, cold pressing was performed twice using steel No. -3, and the effect thereof was also confirmed. The results are shown in Table 6.

In addition, 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 present invention was performed after hot-rolling annealing and scale removal by pickling. The magnetic properties after the final annealing were measured by performing cold pressure twice with intermediate annealing under the specified conditions.

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 6, the same effect as in the once cold pressure method was observed in the twice cold pressure method.

Example- (I) Example- (II) Example- (III)

[Brief description of drawings]

FIGS. 1 (A) to (D) show a steel plate C after roll rolling with vertical grooves.
It is a microscope enlarged photograph which shows the metal structure of a directional cross section. Second
The figure is a microscopic enlarged photograph showing the metal structure of the steel plate cross-sectional view after longitudinal rolling and flattening rolling, and the metal structure of the steel plate cross-section after final annealing, respectively. Fig. 3 (I)-(II
(I) is a pole figure showing the texture of the steel sheet after the final annealing, of which (I) and (II) are the steel sheets according to the method of the present invention,
(III) shows each texture of the steel sheet by the conventional method. FIG. 4 is a graph showing the influence of the number of passes, rolling temperature and lubrication of the fluted roll rolling on the magnetic flux density of the steel sheet which has been subjected to fluted roll rolling-flattening rolling-annealing. FIG. 5 is an explanatory view showing the groove cross-sectional shape of the vertical grooved roll used in the experiment. Fig. 6 shows rolling conditions in roll rolling with vertical grooves 6 is a graph showing the relationship between the magnetic flux density increase amount (usually the increase amount relative to B _{50 of} a smooth roll material).

Claims (2)

[Claims] 1. By weight%, C: 0.01% or less, Si: 0.1 to 7.0
%, Mn: 0.1 to 1.5%, P: 0.1% or less, S: less than 0.01%, Al:
0.001% or less or 0.05 to 1.0%, N: 0.005% or less, balance F
The hot-rolled steel strip having a composition of e and unavoidable impurities is not annealed or annealed, but is subjected to one or more cold rolling or warm rolling with intermediate annealing, and then annealing. When manufacturing a non-oriented electrical steel sheet by performing, in the cold rolling or warm rolling,
Rolling in one or more rolling passes not including the final pass is performed by a roll having longitudinal grooves in the roll circumferential direction, and rolling in one or more rolling passes including the final pass is performed in a smooth roll having no longitudinal groove. A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, which is characterized in that 2. The production of a non-oriented electrical steel sheet having excellent magnetic properties according to claim 1, wherein rolling with a roll having longitudinal grooves in the circumferential direction of the roll is carried out under conditions satisfying the following formula. Method. However, Ai: cross-sectional area of rolled material per vertical groove pitch l after the i-th vertical grooved roll rolling (mm ² ) A′i: flow into the roll groove after the i-th vertical grooved roll rolling Cross-sectional area per groove pitch 1 of the rolled member (mm ² ) l: Pitch of vertical groove (mm) t: Initial plate thickness of rolled material (mm)