JP3430810B2 - Manufacturing method of electrical steel sheet with excellent magnetic properties in the longitudinal direction of coil - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electromagnetic steel sheet which can stably obtain excellent magnetic properties in the longitudinal direction of a coil, and in particular, after rough rolling, a preceding material and a succeeding material are joined to perform finish rolling. It relates to improvement of joining technology in continuous hot rolling.

[0002]

2. Description of the Related Art During hot rolling, continuous hot rolling, in which the trailing edge of the preceding material and the leading edge of the trailing material are joined to finish rolling after rough rolling, mainly improves the efficiency in hot rolling. It is carried out on ordinary steel for the purpose. Recently, also in the field of manufacturing magnetic steel sheets, there is an increasing demand for reducing the manufacturing cost while maintaining the magnetic properties, and it is desired to apply such continuous hot rolling also to the manufacturing of magnetic steel sheets. There is.

However, when the continuous hot rolling technique is applied to the magnetic steel sheet, the magnetic properties are remarkably deteriorated in the vicinity of the joint portion of the following material, and the magnetic properties become nonuniform in the longitudinal direction of the coil, resulting in a yield. Forced to drop significantly.

As a technique relating to continuous hot rolling for joining sheet bars to each other, for example, Japanese Patent Publication No. 54-39194, Japanese Patent Publication No. 56-122, Japanese Patent Publication No. 58-55844 and Japanese Patent Publication No. 4-6441 are disclosed. However, all of these are related to the joining method of the sheet bar, and no consideration is given to the deterioration of the magnetic characteristics that occurs in the vicinity of the joining portion of the following material.

As a technique for continuous hot rolling of electromagnetic steel sheets, Japanese Patent Laid-Open No. 6-299245 discloses a sheet bar after rough rolling, which is rewound at 1090 ° C. or higher, and the rear end of the preceding material is rolled. There is disclosed a technique for joining the leading end portion of the trailing member to the portion. According to the above-mentioned publication, the temperature is made uniform over the entire length of the coil by this technique, and the precipitation form of AlN can be made uniform in the longitudinal direction of the coil. However, the total coil length here refers to the total coil length within the same slab, and does not indicate the total coil length after joining. That is, in the above technique, no consideration is given to the deterioration of the magnetic characteristics in the vicinity of the joint between the preceding material and the trailing material. Deterioration of characteristics cannot be avoided.

[0006]

SUMMARY OF THE INVENTION The present invention was developed in view of the above-mentioned current situation, and has an effect of remarkably deteriorating the magnetic properties in the vicinity of the joint portion of the following material during the continuous hot rolling of electromagnetic steel sheets. It is an object of the present invention to propose an advantageous method for manufacturing an electrical steel sheet in which excellent magnetic properties are stably obtained over the entire length of the coil by suppressing the magnetic field.

[0007]

That is, the present invention is
C: 0.1 wt% or less, Si: 4.5 wt% or less and Mn: 2.5 wt%
% Of slabs for electrical steel sheets, after rough rolling, continuous hot rolling step of joining the trailing end of the preceding material and the leading end of the following material for continuous finish rolling, once or in the middle It consists of a cold rolling process to obtain the final plate thickness by two or more cold rolling processes with annealing between them, and a magnetic treatment process for producing final magnetic properties in the product by primary recrystallization annealing and further secondary recrystallization annealing. In producing a magnetic steel sheet by a series of steps, in the continuous hot rolling step, in joining the sheet bars after the rough rolling and continuously performing finish rolling, the sheet bar surface temperature ratio of the preceding material and the following material R _T , the plate thickness ratio R _{H, the} plate width ratio R _W , and the rolling reduction A _F1 in the first pass of the finish rolling are performed under conditions satisfying the following formula. Of excellent electrical steel sheet It is a production method. Note that R _T R _H R _W / A _F1 ≤ 0.2, where R _T = Max (T ₁ , T ₂ ) / Min (T ₁ , T ₂ ), R _H = Max (H ₁ , H ₂ ) / Min (H ₁ , H ₂ ), R _W = Max (W ₁ , W ₂ ) / Min (W ₁ , W ₂ ), A _F1 : Finish rolling of trailing material First pass reduction (%) _Ti : Finish rolling Entry-side seat bar surface temperature (° C) H _i : seat bar thickness (mm) W _i : seat bar width (mm) i = 1: leading material i = 2: trailing material

Further, in the present invention, at the time of hot finish rolling, pair cross rolling is performed in at least one stand, which is more advantageous in preventing significant magnetic deterioration in the vicinity of the joint of the following material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below based on the experimental results that led to the invention. Now, the inventors have conducted a detailed investigation on the deterioration of the magnetic properties in the vicinity of the joint portion of the following material that occurs when the continuous hot rolling is carried out. As a result, it was newly found that the deterioration of the magnetic properties near the joint of the following material has a deep correlation with the sheet bar surface temperature ratio, the plate thickness ratio and the plate width ratio of the preceding material and the following material. It was also found that such magnetic deterioration tends to be alleviated when the reduction ratio of the finish rolling first stand is large.

Therefore, based on the above-mentioned findings, as a result of earnest studies to achieve the intended purpose, the surface temperature ratio R _T , the plate thickness ratio R _H and the plate width ratio R _{W of} these sheet bars,
And reduction ratio A _F1 (%) in the 1st pass of finish rolling
However, it has been clarified that, when a certain specific relationship is satisfied, it is possible to effectively suppress the remarkable deterioration of the magnetic properties in the vicinity of the joint portion of the following material.

A large number of continuously cast slabs having the four types of composition (steel types A to D) shown in Table 1 were prepared, and a continuous hot rolling experiment was conducted with slabs having the same composition. These continuous casting slabs were reheated and then roughly rolled into sheet bars.
At that time, the surface temperature, the plate thickness and the plate width of the two sheet bars to be joined were variously changed. Then, these two sheet bars were joined and subjected to finish rolling with a 7-stand tandem mill with a target plate thickness of 2.2 mm. Further, some materials were subjected to pair cross rolling at the 6th and 7th stands.

[0012]

[Table 1]

Next, the steel types A and B were immediately cold-rolled into cold-rolled sheets with a thickness of 0.5 mm, and then 800
Finish annealing was performed at ℃ for 10 seconds. Further, with respect to steel type C, after hot-rolled sheet annealing at 1000 ° C. for 1 minute, cold rolling was performed to form a cold-rolled sheet having a thickness of 0.5 mm, and then finish annealing was performed at 820 ° C. for 10 seconds. Furthermore, for steel type D, 1100 ° C,
After hot-rolled sheet annealing for 5 minutes, pickling, primary cold rolling thickness:
After making 0.60mm, after intermediate annealing at 975 ℃ for 60 seconds, finish the final thickness of 0.22mm by secondary cold rolling, then 8
After carrying out decarburization and primary recrystallization annealing at 20 ° C for 2 minutes, MgO was applied to the surface of the steel sheet, and then final annealing including secondary recrystallization annealing at 1200 ° C for 5 hours was performed.

The final product thus obtained was measured for iron loss in the longitudinal direction with a continuous iron meter. FIG. 1 shows the definition of the steady part and the unsteady part in the final product together with the profile example (steel type A) of the continuous iron meter chart. In addition, in FIG. 2, steel types A, B, and C, and in FIG. 3 steel type D, R _T R _H R _W
/ A _F1 and the unsteady part of the trailing material at position X (the position where the deviation of the iron loss from the average value of the iron loss of the steady part is the maximum) and the iron loss of the steady part (average value) The results of examining the relationship with the deviation are shown below.

As is apparent from FIGS. 2 and 3, R _T R _H
In the range where R _W / A _F1 is 0.2 or less, the deviation of the iron loss between the unsteady part and the steady part is small. That is, R _T R _H
By controlling R _W / A _F1 within the range of 0.2 or less, it is possible to effectively reduce the remarkable deterioration of the magnetic properties in the vicinity of the joint portion of the following material. Particularly, such an effect can be obtained by combining pair cross rolling. It turned out to increase.

The reason for this is not necessarily clarified, but it is considered as follows. If there is a significant difference in plate temperature, plate thickness, and plate width between the preceding material and the following material, shape defects occur near the joint during continuous hot rolling,
This causes deterioration of the magnetic properties, but when the plate temperature ratio, plate thickness ratio, and plate width ratio are made small and control is performed within the range that satisfies the above formula, shape defects occur. Therefore, it is considered that the magnetic deterioration does not occur.

[0017]

The composition range of the slab for electromagnetic steel sheets to which the present invention is applied will be described below. C: 0.1 wt% or less In a grain-oriented electrical steel sheet, C is required to be 0.01 wt% or more because it fine-grains the hot rolled crystal structure, but 0.1 wt% or less.
If it exceeds 0.1%, it will not be sufficiently removed even by decarburization annealing, resulting in poor magnetic properties. On the other hand, in the non-oriented electrical steel sheet, 0.01 wt% or less is desirable to prevent aging deterioration of the product, and the lower limit is preferably 0.0001 wt% for economic reasons.

Si: 4.5 wt% or less Si is an additive element useful for increasing electric resistance and improving iron loss, but if it exceeds 4.5 wt%, cold rolling property is deteriorated, so that it is 4.5 wt% or less. To do. However, with respect to the production of grain-oriented electrical steel, if the amount is too small, the texture is randomized by austenite transformation, which hinders secondary recrystallization, so the lower limit is preferably about 2 wt%.
In this respect, in the case of a non-oriented electrical steel sheet, there is no need to set a lower limit because secondary recrystallization is not performed, but it is preferably 0.05 wt% or more in order to improve iron loss.

Mn: 2.5 wt% or less Mn is an element useful for improving hot workability, but if it exceeds 2.5 wt%, the amount of transformation increases and magnetic properties deteriorate, so 2.5 wt% or less. And

In addition to the above-mentioned essential components, various well-known elements can be added to the magnetic steel sheet of the present invention. For example, in grain-oriented electrical steel sheets, Al, P, Cr, B, Se, S, Te, N are used as inhibitor components.
b, Bi, Sn, Sb, N, Mo, etc. can be added. Further, in the non-oriented electrical steel sheet, Al, B, Ni, Cu, Sn, Sb, Bi, Ca, Ge, REM and the like can be added as a magnetic property improving component.

The slab whose components have been adjusted to the above-mentioned preferable composition is subjected to slab heating if necessary and subjected to slab heating or is subjected to rough rolling immediately after casting. Prior to finish rolling, the sheet bar produced by rough rolling joins the trailing end of the preceding sheet bar and the leading end of the following sheet bar. For this joining, a known joining method can be applied. At that time, the sheet bar surface temperature ratio R _T , the plate thickness ratio R _H and the plate width ratio R _{W of} the preceding material and the following material, and the finishing of the following material. Ratio of reduction ratio A _F1 in the first pass of rolling R _T R _H R
It is important to keep the _W / A _F1 value below 0.2.
Because, if R _T R _H R _W / A _F1 value exceeds 0.2,
This is because, as shown in FIGS. 2 and 3, the magnetic properties are significantly deteriorated near the joint. In the present invention, the lower limit of R _T R _H R _W / A _F1 is not particularly set, but the minimum value of R _T R _H R _W is 1 and A _F1 is 100.
Since there can be no more than this, R _T R _H R _W / A _F1
The value of is always greater than 0.01.

In order to set the value of R _T R _H R _W / A _F1 to 0.2 or less, the method of continuously rolling the sheets having the same or similar sheet bar surface temperature, strip thickness and strip width is most suitable. .
In this respect, when the surface temperatures of the two sheet bars are different, a method of making the trailing end temperature of the preceding material and the leading end temperature of the following material equal or similar to each other by a cooling facility or a heating facility such as induction heating is used. When the widths of both seat bars are different, the width of the trailing edge of the preceding material and the width of the leading edge of the following material are reduced to the same or similar width by pressing down with a pusher or a vertical roll only near the joint. If the thickness of both sheet bars is different, the thickness of the trailing edge of the preceding material and the thickness of the leading edge of the following material can be made the same or similar by changing the reduction during rough rolling halfway. A width method or the like is advantageously adapted.

[0023]

[Examples] Thirteen kinds of continuously cast slabs having the composition shown in Table 2 were reheated to various temperatures and then rough-rolled into sheet bars having various thicknesses. Then, the sheet bars were joined together, and finish rolling was continuously performed with a 7-stand tandem mill to obtain a hot-rolled sheet. At this time, a part of them was subjected to pair cross rolling at the 6th and 7th stands. More specifically, regarding No. 1 to 5 steel types, a slab for non-oriented electrical steel sheets with a thickness of 220 mm is heated to 1200 ° C. in a normal gas combustion type heating furnace and then roughly rolled into a sheet. The bar was joined, and these were joined and subjected to continuous finish rolling to obtain a hot rolled coil having a thickness of 2.5 mm. Then, the hot rolled coil was finished by cold rolling into a cold rolled sheet having a thickness of 0.50 mm, and then continuously annealed at 800 ° C. for 30 seconds to obtain a final product.

Regarding No. 6 to 8 steel types, thickness:
A 220 mm slab for non-oriented electrical steel sheets is heated to 1170 ° C in a normal gas combustion type heating furnace, then roughly rolled into a sheet bar, which are joined and subjected to continuous finish rolling. Thickness: 2.
A 3 mm hot rolled coil was used. Then, after annealing the hot-rolled sheet at 1050 ° C for 1 minute, it was finished by cold rolling into a cold-rolled sheet having a thickness of 0.50 mm, and then continuously annealed at 820 ° C for 30 seconds to obtain a final product. Furthermore, for No. 9 to 13 steel types, thickness: 22
A 0 mm grain-oriented electrical steel sheet slab is heated to 1170 ° C in a normal gas combustion type heating furnace, then heated to 1400 ° C for 30 minutes in an induction heating furnace, and then roughly rolled into a sheet bar. They were joined and subjected to continuous finish rolling to obtain a hot rolled coil having a thickness of 2.2 mm. Then, after annealing the hot-rolled sheet at 1100 ° C for 5 minutes,
After pickling and thickness reduction to 0.70 mm by primary cold rolling, 975
After intermediate annealing at 60 ℃ for 60 seconds, thickness of 0.22mm by secondary cold rolling
To the final plate thickness, then decarburization at 820 ℃ for 2 minutes.
After the next recrystallization annealing, apply MgO on the steel plate surface, then
Final annealing was carried out at ℃ for 5 hours to obtain the final product.

The iron loss in the longitudinal direction of the product sheet thus obtained was measured, and the deviation between the iron loss at the position X of the non-steady portion and the iron loss (average value) of the steady portion was obtained, and this was used as the evaluation index. .
The obtained evaluation results are summarized in Tables 3 to 6 together with the surface temperature, the plate thickness and the plate width at the time of joining the sheet bars. In addition,
The iron loss of No. 1 to 8 steel types is W _15/50 (W / kg), while that of No. 9 to
The iron loss of 13 steel _grades is shown by W _17/50 (W / kg). Further, the iron loss value is the average value of the steady part of the trailing material. Further, those subjected to pair cross rolling are indicated by asterisks.

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

As shown in the table, R _T R _H R _W / A _F1
Inventive examples in which the range of 0.2 or less is R _T R _H R _W / A _F1
It was possible to stably obtain excellent iron loss in the longitudinal direction as compared with the comparative example in which the value exceeds 0.2.

[0032]

As described above, according to the present invention, excellent iron loss can be stably obtained in the longitudinal direction of the coil even when continuous hot rolling is applied to the hot rolling process.

[Brief description of drawings]

FIG. 1 is a graph showing changes in iron loss value in the vicinity of a joint.

FIG. 2 shows the difference between R _T R _H R _W / A _{F1 of} steel types A, B and C and the iron loss at the position X of the unsteady part of the following material and the iron loss (average value) of the steady part. It is a graph showing a relationship.

FIG. 3 shows the relationship between R _T R _H R _W / A _{F1 of} steel type D and the deviation of the iron loss at the position X of the unsteady part of the following material and the iron loss (average value) of the steady part. It is a graph.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI C22C 38/00 303 C22C 38/00 303U 38/04 38/04 H01F 1/16 H01F 1/16 A (72) Inventor Michio Komatsubara Kurashiki, Okayama Prefecture Mizushimakawasakidori 1-chome in the (address teeth) Kawasaki Steel Corporation Mizushima Works (56) reference Patent flat 6-299245 (JP, a) (58 ) investigated the field (Int.Cl. ^7, DB name) C21D 8/12 C21D 9/46 501 B21B 1/26 B21B 3/02 B21B 15/00 C22C 38/00-38/60 H01F 1/16-1/18

Claims (2)

(57) [Claims] 1. A slab for electrical steel sheets containing C: 0.1 wt% or less, Si: 4.5 wt% or less, and Mn: 2.5 wt% or less,
After rough rolling, a continuous hot rolling process in which the trailing edge of the preceding material and the leading edge of the trailing material are joined together for continuous finish rolling, by one or two or more cold rollings with intermediate annealing. In producing a magnetic steel sheet by a series of steps including a cold rolling step for obtaining a final plate thickness, a primary recrystallization annealing, and further a magnetic treatment step for producing final magnetic properties in a product by secondary recrystallization annealing, In the above continuous hot rolling step, in joining the sheet bars after the rough rolling and continuously performing finish rolling, the sheet bar surface temperature ratio _{RT of} the preceding material and the following material, the plate thickness ratio _RH and the plate width. A method for producing an electromagnetic steel sheet excellent in magnetic properties in the longitudinal direction of a coil, characterized in that the ratio R _W and the rolling reduction A _F1 in the first pass of finish rolling are carried out under the condition that the following formula is satisfied. Note that R _T R _H R _W / A _F1 ≤ 0.2, where R _T = Max (T ₁ , T ₂ ) / Min (T ₁ , T ₂ ), R _H = Max (H ₁ , H ₂ ) / Min (H _{1, H 2), R W} = Max (W 1, W 2) / Min (W 1, W 2), a F1: rolling reduction of finish rolling the first pass of the following material (%) T _i: finish rolling Entry-side seat bar surface temperature (° C) H _i : seat bar thickness (mm) W _i : seat bar width (mm) i = 1: leading material i = 2: trailing material 2. The method of manufacturing an electrical steel sheet according to claim 1, wherein at the time of hot finish rolling, pair cross rolling is performed by at least one stand.