JPS60145204A - Hot rolling method of anisotropic silicon steel plate - Google Patents

Abstract

PURPOSE:To eliminate the flaws of earing parts of a hot coil by subjecting a prescribed anisotropic silicon steel plate to the prescribed rolling reduction in its width direction, by edging rolls, at the initial stage of a finishing mill. CONSTITUTION:An anisotropic silicon steel slab containing 2.5-4.1wt% Si is heated to bae rought rolled. Next, its finish rolling is started at a temperature of >=1,100 deg.C. The slab is subjected to the width rolling reduction of 5-40mm. by edging rolls at the position of inlet and/or outlet side of the 1st stand of a finishing mill. In this way, the flaws generating at the earing parts of a hot coil are prevented.

Description

[Detailed Description of the Invention] (Technical Field) The present invention belongs to the field of hot rolling technology used in the production of grain-oriented silicon steel sheets, and relates to the field of hot rolling technology used in the production of grain-oriented silicon steel sheets. This is a proposal for a hot rolling method that can effectively prevent ear flaws such as otoscope i and re-splitting during inter-rolling and improve product yield.

(Prior art and its problems) Grain-oriented silicon steel sheets are widely used as iron core materials for transformers and the like due to their excellent magnetic properties, including high magnetic flux density and low iron loss. In recent years, even in this type of technical field, there has been a desire to supply grain-oriented silicon steel sheets with excellent magnetic properties at a lower cost, and the manufacturing cost has increased. How to reduce this is a common problem that must be solved by the engineers concerned.

Generally, in order to obtain grain-oriented silicon steel sheets with excellent magnetic properties, the (]10)<001) orientation (
It is necessary to control the secondary recrystallization phenomenon in which the Goss orientation selectively grows, and to obtain a uniform secondary recrystallization structure in which the Goss orientation is highly concentrated.

In order to obtain a recrystallized texture with Goss orientation, it is effective to utilize an appropriate precipitated dispersed phase, and for this reason, NiMnS,
Impurities called inhibitors such as MnSe and IN are used. This technology GF first uses Mn during slab heating.
It is important to obtain a dispersed phase preferable as an inhibitor by sufficiently dissociating S, MnSe, etc. into a solid solution and then subjecting the material to appropriate hot rolling.

The slab heating temperature required for this dissociation and solid solution (solution treatment) of the inhibitor is usually in the high temperature range of 1800-1420°C for a long time.

However, long-term heating in a high temperature range of 1800°C or higher induces abnormal growth of slab crystal grains, and the coarse crystal grains do not recrystallize sufficiently even during hot rolling, leaving coarse crystal grains. This was often the cause of ear scratches, as typified by cracks in the ears of hot coils. These hot coil edge flaws can cause breakage in the next process of cold rolling, and the rough edges must be removed by cutting off the edges before cold rolling, which greatly reduces yield and reduces production. This was the main cause of cost increases.

In short, the above-mentioned phenomenon, which is particularly observed in continuous cast slabs, is that columnar crystal structures are easily formed in continuous cast slabs due to rapid solidification, and these columnar crystal structures are more prone to abnormal growth than normal agglomerated materials. Therefore, they tend to remain as unrecrystallized grains after rough rolling. These coarse grains have extremely poor toughness and become ear flaws in the hot coil in the latter stages of hot finish rolling.

Conventionally, such prevention of ear scratches has already been published in
There is a technique disclosed in No. 4F190, which is a method of promoting recrystallization of coarse grains by changing the rolling reduction schedule during rough rolling, but this method is difficult to achieve in a rolling mill with only a normal horizontal rail. Sufficient stress is applied to the sides, but no great effect can be expected. Others, Tokukai Showa Rfi-
Method for limiting temperature difference between start and end during finish rolling disclosed as f1.2124, JP-A-57-]f151
(Methods based on temperature control have been proposed, such as the method disclosed in No. 11, which limits the temperature difference between the longitudinal and width directions of the rolling machine during finish rolling. All of these methods eliminate temperature non-uniformity. Although this method is intended to prevent ear scratches, it is a rather passive method for the phenomenon of the edges (ears) on both sides of the strip, and has not yet provided a fundamental solution.

(Introduction to the Invention) The present inventors conducted a follow-up investigation of phenomena during rolling, such as when edge cracking occurs and how it develops, and as a result, the following findings were obtained. That is, at the both side edges (edges) in the width direction of the sheet bar in one stage after rough rolling, the coarse crystal grains are not sufficiently recrystallized and the coarse drawn grains and fine recrystallized grains are mixed together. This is because the thickness of the coarse grains after heating is large during rough rolling, so the effect is small, and the resistance from both end faces of the plate is small, so slippage occurs at the grain boundaries and sufficient stress is not transmitted. This is thought to be because they remain as unrecrystallized grains. In this case, the shape of both side edges of the sheet bar is such that coarse grains jump out discontinuously and create complex undulations.

Normally, when a rolled plate is rolled, 8-axis stress acts on both side edges of the plate, and the strip becomes wider. At this time, if the shape of both side edges of the strip, that is, the edges, is irregularly undulating, local stress concentration occurs, causing internal cracks and eventually causing edge splitting. In fact, the higher the flatness of both edges in the width direction at the first stage of the sheet bar, the more the degree of ear scratches will be alleviated, and the shape of the side edges of the rolled material before finish rolling has a large effect on ear scratches (particularly ear cracks). It turns out that it does.

(Objective and Summary Structure of the Invention) The present invention is based on the above-mentioned knowledge that the shape of the edges of the rolled material at the initial stage of finish rolling affects the condition of the edges of the hot coil. The purpose is to effectively prevent the above ear scratches without causing damage.
By adopting the method described in the claims, the main feature of which is to mechanically straighten both end surfaces of the sheet bar and strip using edger rolls at the initial stage of finish rolling, the above-mentioned conventional method can be improved. Sorry for exceeding the limits of technology.

(Structure of the Invention) The main manufacturing process of grain-oriented violet steel sheet to which the present invention is applied is as follows: Si: 2. Steel containing r1 to 4.1% is made into a slab by an ingot-forming method or a continuous casting method, and then hot rolled into a hot coil. Next, after achieving the final thickness by cold rolling once or twice with intermediate annealing in between,
It consists of performing decarburization annealing and finish annealing, and the features of the present invention in the above steps include reheating the slab,
It is in the finish rolling process after rough rolling. That is, by applying edging using an edger reel (vertical roll) at either or both of the entry and exit sides of the finishing mill and the first stand, width reduction is applied to both side end faces of the sheet bar and strip, and both side edges are The point is to correct the shape of the . The reasons for limiting each condition in the above manufacturing process will be described below.

The composition of the steel used in the present invention is 1% by weight, Si:
L5 to 4.1% is an essential component, and other C:, 0. (1
1-0.08%, In: 0.08-0.1%, S
and/or 88 + 0.005-0.1% of sasse, remaining iron and some unavoidable components.

If 5iii is less than 2.151, sufficient magnetic properties cannot be obtained, and if it is more than 4.1%, cold rolling becomes difficult; therefore, Si: 2.5 to 4. ]%. Cil is
If it is less than 0.0%, a sufficient amount of γ phase will not be generated during hot rolling, and if it is more than 0.08%, it will take a long time to decarburize in the subsequent process, so it is limited to 0.01 to 0.08%. did.

In, S and Ss form the inhibitor P used as the precipitated dispersed phase, so the content of each is Mn:
0.08%, S and/or 86 j 0.005%
Less than 0.0% respectively results in a quantitative deficiency of the precipitated dispersed phase. ]%, there will be insufficient solutionization during slab heating and an appropriate dispersed phase will not be obtained, so In: 0.08 to 0.
．． 1%, S and/or 88: 0. Of ~0.1
%. Others ar, Ni + Ou,
No. 8b.

Although solute atoms such as P and Sn may be intentionally added, the effects of the present invention are not lost in this case as well.

, the slab containing the above components is heated to 1800~1 in a pusher or walking beam type slab heating furnace.
The slab is heated to a temperature of 420°C, but this is because if the heating temperature of the slab is lower than 1800°C, solid solution of impurities used as a precipitated dispersed phase will be insufficient, and if it is too high, a huge amount of scale will be generated. 1.1 as it will reduce the life of the furnace.
The temperature range is preferably from 100 to 1420°C. Thereafter, it is rolled in multiple passes in a rough rolling mill to form a sheet bar having a thickness of about 20 to flom/m.

Etching, which is a feature of the present invention, is carried out at at least one or both of the entrance side and exit side of the first stand of the finishing rolling mill, with a straightening reduction of 5 to 40 m/m. The range of this width reduction is as shown in Figure 1.
If it is less than 5 m/m, the effect of shape correction will be small;
On the other hand, if it exceeds 40 m/m, shape defects will occur due to the formation of dog bones, so the range f-5 to 40 m/m is
m. Note that this reduction is performed to prevent stress concentration by correcting the shape of the side edges, and to reduce the S# of the internal cracks. After the second stand, the thickness of the strip becomes thinner and shape defects due to width reduction are more likely to occur.
We decided to do it before and after the stand.

Next, the temperature before the start of finish rolling is set to 1100° C. or lower because if this temperature is exceeded, the size of the precipitated dispersed phase often becomes non-uniform and the magnetic properties deteriorate.

Then, after performing cold rolling once or twice or more including intermediate annealing to obtain a finished product thickness, decarburization annealing that also serves as primary recrystallization is performed for about 8 to 15 minutes in a wet hydrogen atmosphere at 780 to 800°C. Final annealing is performed at 1200°C or higher.

In addition, FIG. 2 shows a preferred embodiment of the present invention, in which 1 is a rough edger, 12 is a rough rolling mill, 8 is a crop shear, 4 is an entry edger, and 55 is the first stand of a finishing mill. 6 is the second stand, between which the outlet edger 7 is arranged, and 8 is the final stand.

(Example) Q: 0.04%, s, t: 2.9rs%, Mn
: 0.07% s : o, o 2% Molten steel in which the balance mainly consisted of 7e was continuously cast to obtain a slab with a thickness of 280 m/m. This was heated to 850℃, and the following (a) ~
Hot rolled under 8 conditions of (0), thickness 2.4 m/m
manufactured hot coils.

As a condition for the manufacturing process, the condition (a) is that no 9-width cutting is performed at both the stand man and the exit edger,
Condition (b) is that a width reduction of 10 m/m was applied at the entrance edger of the first stand, and a width reduction of 10 m/m (26 m/m in total) was applied at both the entry and exit edgers respectively. Let that be the condition (0).

The obtained hot carp/l/l was 950 % of the hot carp obtained by homogenizing annealing at 900°C for 8 minutes, about 70% of the primary cold rolling.
After intermediate annealing for 8 minutes at ℃, secondary cold rolling of approximately 60% is performed to
．． The product thickness was 8 m/m. Thereafter, decarburization annealing was performed for 4 minutes in a wet leaf at 820°C. Then, MgO
An annealing separator mainly composed of was applied, and final annealing was performed at 200°C.

The results are shown in the table below.

Table 1 (Effects of the Invention) As explained above, according to the hot rolling method of the present invention, in which a grain-oriented silicon steel sheet is subjected to appropriate width reduction by an edger at the initial stage of the finishing mill, hot coil It is possible to eliminate ear scratches on both sides of the widthwise edges (ears).

[Brief explanation of the drawing]

Figure 1 shows the relationship sf between the edge width reduction amount and the degree of edge cracking.
- Graph 1 and Figure 2 are route maps of hot rolling equipment used to carry out the method of the present invention. 1...Rough edger 2...Rough rolling mill 8...Crop shear 4...No. of finishing mill] Stand entry side edger 5
...First stand 6 of the finishing rolling mill...Second stand 7 of the finishing rolling mill...First stand exit edger 8 of the finishing rolling mill
...The final stand of the finishing rolling mill. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] A silicon steel slab containing LSi: 2.5 to 4.1% by weight is heated to a temperature of 1800 to 420°C and subjected to rough rolling and finish rolling. In the method for obtaining a hot-rolled steel strip, during the above-mentioned hot finish rolling, (a) finish rolling start temperature) IR should be 1100°C or higher; (b) on the entry and exit sides of the first stand of the finishing mill; 5~ by Ezjar four in either or both positions
A method for hot rolling a grain-oriented silicon steel sheet, characterized by applying a width reduction of 40 mm, and rolling to satisfy the following conditions.