JPH0649900B2 - Method for manufacturing unidirectional silicon steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) With regard to a method for producing a unidirectional silicon steel sheet, the technical content described in this specification is that hot rolling can be performed by devising a hot rolling process. Increasing the Goss orientation integration of the plate surface layer,
The purpose is to improve the magnetic properties of the product plate.

As is well known, a unidirectional silicon steel sheet imparts excellent magnetic properties to the rolling direction by bringing the orientation of secondary grains close to the ideal Goss orientation by secondary recrystallization annealing. . To this end, a strong accumulation of primary recrystallized grains in the Goss orientation, that is, the (110) [001] orientation, which should be the nucleus of secondary recrystallization, is allowed to exist in the steel sheet surface layer before the secondary recrystallization treatment, and at the same time It is important to form in the center layer of the steel sheet a crystallographic texture that promotes the growth of secondary grains in the orientation.

Needless to say, the quality of the primary recrystallization texture depends on the rolling and annealing conditions in the cold rolling process, but its origin is hot rolling, and the Goss orientation in the surface layer of the steel sheet after hot rolling is Increasing the degree of integration leads to an increase in the number of secondary recrystallization nuclei in the Goss orientation, which in turn enables the production of grain-oriented silicon steel sheets with a fine secondary grain size and good magnetic properties. .

(Prior Art) There have been many reports on hot rolling methods for improving the hot rolled texture, but most of them report the coarse elongated grains caused by high temperature slab heating peculiar to grain-oriented silicon steel sheets. It is intended to form a matrix texture which is reduced and the Goss orientation is easy to grow. For example, JP-A-54-120214
Japanese Patent Publication No. 59-93828 and Japanese Unexamined Patent Publication No. 59-93828 restrict the reduction ratio and strain rate in a specific temperature range during hot rolling, and Japanese Patent Publication No. 58-5970 discloses asymmetrical vertical rolling during hot rolling. There has been proposed a method for achieving the above-mentioned object by carrying out different speed rolling which gives a plastic flow.

On the other hand, there are few reports on the hot rolling method for improving the Goss orientation integration degree of the surface layer of the hot rolled sheet.
In JP-A-32526, there is only one in which the upper limit of the hot rolling finish temperature according to the amounts of Si and C is regulated as it is necessary to carry out hot rolling at a rolling reduction of at least 50% in the state where γ phase is not precipitated. Absent.

(Problems to be solved by the invention) By improving the hot rolling process, it is possible to improve the integration degree of the Goss orientation in the surface layer of the hot-rolled sheet and to obtain a unidirectional silicon steel sheet excellent in magnetic properties. It is an object of this invention to provide a novel method of manufacture that is obtained.

(Means for Solving Problems) In order to achieve the above object, the inventors have many relations between the hot rolling conditions and the strength of the Goss orientation in the surface layer of the hot rolled sheet (hereinafter simply referred to as Goss strength). As a result of the experiments and studies, it was found that increasing the frictional force between the steel slab and the rolling roll during hot rolling is extremely effective in improving the Goss strength.

The present invention is based on the above findings.

That is, the present invention is C: 0.02 to 0.08 wt% (hereinafter simply referred to as%
, Si: 2.0 to 4.5%, Mn: 0.01 to 0.10% and at least one of S and Se: 0.005 to 0.1
A slab for silicon steel with a composition containing 0% is hot-rolled and then cold-rolled once or twice with intermediate annealing to obtain a final plate thickness, and then decarburized in wet hydrogen. When manufacturing a unidirectional silicon steel sheet by a series of steps in which primary recrystallization annealing is performed, then an annealing separator containing MgO as a main component is applied, and then secondary recrystallization annealing and then purification annealing are performed. In the above hot rolling, the billet temperature during rolling is within a range of 1000 ° C or less, and the friction coefficient between the rolling roll and the billet is 0.27.
This is a method for producing a unidirectional silicon steel sheet, which is performed under the above conditions and a reduction ratio of 30% or more.

In the present invention, when hot rolling is performed by tandem rolling, the coefficient of friction between the rolling roll and the billet is
In addition to 0.27 or more and a reduction rate of 30% or more,
It is desirable to finish at a temperature of 900 ° C or lower.

The billet temperature in the present invention means a billet surface temperature.

The present invention will be specifically described below.

First, the experimental results, which are the basis of the present invention, will be described.

Fig. 1 shows the friction coefficient between the rolling roll and the steel slab and the surface of the hot-rolled sheet when a slab for silicon steel containing C: 0.035% and Si: 3.30% was hot-rolled at a rolling reduction of 60%. Layer of (110)
The relationship with the surface strength is shown. Here, the (110) plane strength is an index of Goss strength, and it can be said that the larger the (110) plane strength, the higher the Goss strength.

The coefficient of friction μ between the rolling roll and the steel slab is obtained by the following equation.

Where α is the biting angle γ is the rolling reduction rate: the advanced rate [= (V ₂ −V _r ) / V _r ] V _{r is the} roll peripheral velocity V _{2 is the} delivery speed of the billet. The (110) surface strength increases as the friction coefficient between the rolling roll and the steel slab increases, and especially when the friction coefficient is 0.27 or more, the (110) surface strength is 2.
A high value of 0 or more was exhibited.

Next, each of the above hot-rolled sheets was subjected to double cold rolling at a primary cold rolling reduction of 75% and a secondary cold rolling reduction of 70% with intermediate annealing in H ₂ at 1000 ° C. for 3 minutes. To the final plate thickness, then wet
In H ₂ 800 ° C., decarburization and primary recrystallization annealing of the 5 minutes, then in dry H ₂ 1200 ° C., in a product obtained by applying the final finish annealing of 10 hours, the magnetic flux density B ₁₀ and the hot rolled sheet surface layer Of (1
10) The relationship with the surface strength is shown in FIG.

As is clear from the figure, B ₁₀ ≧ 1.90T is stably obtained in the range where the (110) plane strength is 2.0 or more.

Next, FIG. 3 shows the results of examining the effect of the reduction ratio in hot rolling on the (110) surface strength of the surface layer of the hot rolled sheet, using the billet temperature during hot rolling as a parameter.
The coefficient of friction between the rolling roll and the steel slab at this time was controlled to around 0.29.

Further, this hot rolling was performed in one pass with each temperature shown in the same table as the rolling stand entrance side temperature.

As is clear from the figure, the (110) surface strength was found to be particularly advantageous when the hot rolling reduction was 30% or more and the billet temperature during hot rolling was 1000 ° C or less.

The reason why the component composition of the raw material is limited to the above range in the present invention is as follows.

C: 0.02 to 0.08% C effectively contributes to subdivide coarse elongated grains harmful to the growth of Goss orientation often found in hot rolled textures, but if the content is less than 0.02%, The effect of addition is poor, while if it exceeds 0.08, satisfactory decarburization becomes difficult even with the subsequent decarburization treatment, so the range was limited to 0.02 to 0.08%.

Si: 2.0 to 4.5% Si is an element useful for increasing the specific resistance and reducing the eddy current loss, but if it is less than 2.0%, γ-transformation occurs during high temperature final finish annealing to reduce the Goss strength. On the other hand, if it exceeds 4.5%, the workability deteriorates, so the Si content is 2.0-4.5.
It was limited to the range of%.

Mn: 0.01 to 0.10% Mn binds to S and Se described later and inhibits MnS and MnSe.
However, if less than 0.01%, the effect of addition is poor, while if more than 0.10%, fine dispersion of the inhibitor in the steel is hindered, so the content was limited to 0.01 to 0.10%.

S and / or Se: 0.005 to 0.10% S and Se both effectively contribute as an inhibitor-forming element as described above, and the addition amount is set within the above range as a range in which the effect can be sufficiently exhibited. .

Although the essential components have been described above, other additives such as grain boundary segregation type elements such as Sb, Bi, Sn, Pb, As and Mo and nitrides such as AlN, BN and VN are not hindered as inhibitors.

Next, the manufacturing method according to the present invention will be specifically described in the order of steps.

Both the continuous casting method and the agglomeration-agglomeration method can be used for producing the slab.

The heating of the slab is necessary to fully dissolve MnS and MnSe.
It is preferable to raise the temperature to 250 ° C. or higher.

Then, hot rolling is performed to form a hot rolled steel strip having a thickness of 1.5 to 3.5 mm. The hot rolling here is usually carried out in a temperature range of about 1200 to 900 ° C., but in the present invention, at the time of such hot rolling, at least a billet temperature of 1000 ° C. or less is a rolling roll. It is important to regulate the coefficient of friction with the billet to 0.27 or more and the rolling reduction to 30% or more.

This is because, as shown in Figures 1, 2 and 3 above, the coefficient of friction between the rolling roll and the billet was 0.27 or more and the hot rolling reduction rate was 30% in the range where the billet temperature was 1000 ° C or less.
By the above, the improvement of the (110) strength of the surface layer of the hot-rolled sheet and thus the B ₁₀ value of the product sheet is achieved.

Here, in order to increase the friction coefficient between the rolling roll and the steel billet, the surface roughness of the rolling roll is roughened, or the roll diameter of the rolling roll is reduced to increase the biting angle of the roll and the billet. Is effective.

Note that such hot rolling is usually performed by rough rolling and finish rolling with a tandem mill, and the texture of the Goss orientation formed in the surface layer of the hot-rolled sheet is mainly after the rough rolling or in the finish rolling step. However, when hot finish rolling is carried out using a tandem mill, the friction coefficient is increased and the Goss orientation once formed is increased by recrystallization during or after hot rolling. 90 to prevent weakening
It is desirable to finish at 0 ° C or lower.

Next, cold rolling is performed to finish the final product sheet thickness of 0.15 to 0.35 mm. For this cold rolling, either of the conventionally known one-time method or two-time method can be applied.

Decarburization / primary recrystallization annealing is 800 ~ 85 in wet H ₂ atmosphere.
Treatment at 0 ° C. for about 1 to 5 minutes is preferable.

After that, 800 ~ 900 ℃, 2 for about 10 to 100 hours
Next recrystallization annealing, then 1100 to 1200 ° C, 5 to 20
Purification annealing is performed for about a time to make a product plate.

(Operation) According to the present invention, the hot rolling is performed under the conditions that the billet temperature is 1000 ° C. or less and the rolling reduction is 30% or more and the friction coefficient between the rolling roll and the billet is 0.27 or more. The reason why the magnetic properties of the product sheet are remarkably improved is thought to be that the slip rotation of the crystal progresses due to hot rolling under the above conditions, and the Goss strength of the surface layer of the hot rolled sheet increases. .

(Example) C: 0.050%, Si: 3.30%, Mn: 0.080%, Se: 0.025%
And a composition containing Sb: 0.035% Thickness: 230 m
The m continuous cast slab was heated at 1330 ° C. for 3 hours and then hot-rolled to form a hot-rolled steel sheet having a thickness of 2.3 mm. In this hot rolling, finish rolling conditions after rough rolling to a thickness of 30 mm are as shown in Table 1.

After the first cold rolling to 0.60 mm thickness, 10 in H ₂
After intermediate annealing at 00 ° C. for 3 minutes, a second cold rolling was performed to obtain a final plate thickness of 0.23 mm.

Then, after decarburization annealing at 830 ° C. for 3 minutes in wet H ₂ , an annealing separator containing MgO as a main component is applied, and then 120 times in H _2.
Final finishing annealing was performed at 0 ° C. for 10 hours.

The results of examining the magnetic properties of the product sheet thus obtained are also shown in Table 1.

As is clear from the table, particularly excellent magnetic properties are obtained when the hot rolling according to the present invention is performed.

According to (Effect of Invention) Thus the present invention, Yotsute to enhance the Goss intensity of the hot rolled sheet surface layer effectively, excellent grain-oriented silicon steel sheet with the magnetic flux density B ₁₀ and core loss characteristic W17 / 50 Can be easily obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relationship between the friction coefficient between a rolling roll and a steel slab in hot rolling and the Goss strength of the surface layer of a hot rolled sheet, and FIG. Fig. 3 is a graph showing the relationship between the (110) surface strength of the plate surface layer and the magnetic flux density B ₁₀ of the product plate. Fig. 3 shows the reduction ratio in hot rolling and the (110) surface strength of the hot rolled plate surface layer. It is a graph which showed the relation using the billet temperature as a parameter.

Claims (2)

[Claims] 1. C: 0.02 to 0.08 wt% Si: 2.0 to 4.5 wt% Mn: 0.01 to 0.10 wt% and at least one of S and Se: 0.005 to 0.10 wt% Silicon having a composition The steel slab is hot-rolled and then cold-rolled once or twice with intermediate annealing to obtain the final plate thickness, and then decarburized and primary recrystallization annealing in wet hydrogen, and then In producing a unidirectional silicon steel sheet by a series of steps of applying an annealing separator having MgO as a main component, and then performing secondary recrystallization annealing and then purification annealing, the above hot rolling is performed during rolling. Friction coefficient between rolling roll and billet: 0.27 for billet temperature below 1000 ℃
A method for manufacturing a unidirectional silicon steel sheet, which is performed under the above conditions and a reduction ratio of 30% or more. 2. The method according to claim 1, wherein the hot rolling is tandem rolling and the finishing temperature is 900 ° C. or lower.