JPH11131141A - Production of grain oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain good magnetic properties in a steel sheet by allowing it to contain specified amounts of one or more kinds of S and Se and B, regulating the draft in final cold rolling to specified value or above to finish its sheet thickness into the final one and executing short time final finish annealing under specified conditions. SOLUTION: A base steel slab has a compsn. contg., by weight, 0.02 to 0.08% C, 2.0 to 4.0% Si and 0.03 to 0.2% Mn, furthermore, contg. one or more kinds among 0.01 to 0.20% Sb, 0.02 to 0.20% Sn and 0.02 to 0.05% Mo, and the balance substantial Fe, and, moreover, one or two kinds of S and Se by 0.005 to 0.020% and 0.5 to 20 ppm B are incorporated therein. This slab is subjected to hot rolling and is subjected to cold rolling for one time or two times including process annealing to finish its sheet thickness into the final one. The draft in the final cold rolling is regulated to >=80%. Next, after decarburizing annealing, it is subjected to final finish annealing to form into a grain oriented silicon steel sheet. The final finish annealing is executed in the temp. range of 900 to 1200 deg.C for 3 sec to 10 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented silicon steel sheet, and more particularly, to an easy axis <001> parallel to the rolling direction of the steel sheet by a final finishing annealing in a short time.
It is an object of the present invention to obtain a unidirectional silicon steel sheet having excellent magnetic properties and having a {110} plane parallel to the plate surface.

[0002]

2. Description of the Related Art Conventionally, in producing a grain-oriented electrical steel sheet, it is necessary to preferentially recrystallize crystal grains having the (110) <001> orientation, and an extremely long time is required for final finish annealing. Therefore, the box annealing method has been usually used. However, since this box annealing requires enormous heat energy, several short-time continuous annealing methods have been proposed so far in order to reduce the production cost.

[0003] For example, Japanese Patent Publication No. 48-3929 and
Japanese Patent Application Laid-Open No. -95816 proposes a method in which a secondary recrystallization can be performed in a short time by using a rapid heating process in the final annealing. In addition, JP-A-49-98721 proposes a method in which cooling during final annealing is gradually cooled in order to make fine precipitates causing iron loss deterioration coarse and detoxified. . Also, Japanese Patent Application Laid-Open Nos.
No. 4863, a method of devising decarburization annealing conditions, and further, in JP-A-55-58332, a method of omitting decarburization annealing and performing a continuous final annealing by rapid heating with a cold-rolled structure, Each has been proposed.

[0004] However, in these methods, (110) <00 as in any case obtained by the long-time box annealing method.
1> Sufficient iron loss characteristics could not be obtained because sufficient accumulation in the orientation could not be expected.

In addition, Japanese Patent Application Laid-Open No. 5-70833 proposes a method in which light rolling is performed before final continuous annealing. According to this method, magnetic properties in a direction perpendicular to the rolling direction are improved. However, there remains a problem in that the magnetic properties in the rolling direction are greatly inferior to ordinary grain-oriented silicon steel sheets.

[0006]

As described above, none of the conventional short-time continuous annealing methods can provide satisfactory magnetic properties. The present invention advantageously solves the above-mentioned problems. Even when the final finish annealing is performed by a short-time continuous annealing method, an advantageous effect of a unidirectional silicon steel sheet capable of stably obtaining good magnetic properties can be obtained. The purpose is to propose a manufacturing method.

[0007]

Means for Solving the Problems Now, the inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that material components,
It has been found that the intended purpose can be advantageously achieved if the final cold rolling reduction and annealing conditions are controlled in appropriate ranges. The present invention is based on the above findings.

That is, the present invention provides a method for producing C: 0.02 to 0.08 wt.
%, Si: 2.0-4.0 wt%, Mn: 0.03-0.2 wt%,
And Sb: 0.01 to 0.20 wt%, Sn: 0.02 to 0.20 wt% and M
o: At least one selected from 0.02 to 0.05 wt% is contained, and the rest is a silicon steel slab having a substantially Fe composition, which is hot-rolled, and if necessary, hot-rolled sheet annealing is performed. After that, the steel sheet is subjected to cold rolling once or twice with intermediate annealing to finish to a final sheet thickness, then, after decarburizing annealing, a series of steps of final annealing to produce a unidirectional silicon steel sheet. (1) In the silicon-containing steel slab, one or two kinds selected from S and Se are 0.005 to 0.020.
wt% and 0.5 to 20 ppm of boron, (2)
The final cold-rolling reduction rate is 80% or more and the final thickness is finished. (3) The final finish annealing is performed in a temperature range of 900 ° C or more and 1200 ° C or less for 3 seconds or more and 10 minutes or less. This is a method for producing a unidirectional silicon steel sheet.

According to the present invention, at least one selected from Al and Ti is further added to the silicon-containing steel slab.
It is preferable to contain 50 ppm. In the present invention, it is advantageous that the final cold rolling is a warm rolling at 100 ° C. or higher.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention details the effects of the amounts of B, Al, Ti and cold rolling conditions on secondary recrystallization during short-time finish annealing, which have not been studied before. It was developed as a result of careful examination. Hereinafter, an experiment and a result thereof which are the basis of the present invention will be described.

Two types of silicon steel slabs having the component compositions shown in Table 1 were heated at 1420 ° C. for 15 minutes, and then hot-rolled to form rolled coils having a thickness of 2.5 mm. This hot rolled coil is
After annealing at 00 ° C. for 1 minute, the sheet was finished to a sheet thickness of 0.34 mm by cold rolling in a rolling distribution shown in Table 2. At this time, the intermediate annealing conditions were all 950 ° C. for 1 minute. Then 840 ℃, 2
After decarburizing annealing for 10 minutes, short-time continuous finishing annealing was performed at 1050 ° C. for 3 minutes. The results of measurement for the magnetic flux density B ₈ of the obtained product plate are shown in Table 2. Table 3 shows the result of investigation on the secondary recrystallization fraction at this time.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

As is clear from Table 3, in the case of boron-containing steel A, the secondary recrystallization fraction was close to 100% under high pressure, and a high magnetic flux density could be obtained. On the other hand, in steel B containing no boron, the secondary recrystallization completion rate tends to be higher under light pressure, but a higher magnetic flux density than steel A is not obtained.

FIG. 1 shows the results of an investigation into the effects of the amount of boron and the final cold rolling reduction on the magnetic flux density. As is clear from the figure, the boron content is 0.5 p.
Particularly excellent magnetic flux density is obtained in the range of pm to 20 ppm and the rolling reduction of 80% or more.

As described above, the reason why the secondary recrystallization can be performed in a short time by adding a small amount of boron and adjusting the final cold condition has not been clearly elucidated yet. It is considered as follows. That is, in order to complete the secondary recrystallization of the grain-oriented silicon steel sheet in a short time, it is necessary to moderately reduce the so-called inhibitor strength of the primary recrystallization and reduce the incubation period of the secondary recrystallization. is important. In order to obtain a high magnetic flux density,
Generally, the final cold rolling is performed under a high pressure of 80% or more, as is performed in a component system in which AlN is the main inhibitor.

[0018] However, even when such a material containing AlN as a main inhibitor is subjected to short-time finish annealing at 1050 ° C for 5 minutes, secondary recrystallization cannot often be completed. Also, MnS without AlN or
Secondary recrystallization is likely to occur in a component material using MnSe as an inhibitor, but there is an upper limit on the rolling reduction of final cold rolling, and the magnetic flux density of the finish-annealed sheet obtained by short-time annealing is generally low. Was. In this regard, as in the present invention, while weakening the primary grain growth suppressing power of MnS or MnSe and adding a small amount of boron and also Al and Ti, it is possible to obtain a high magnetic flux density easily under a high pressure of 80% or more. It is considered that finish annealing at the same time becomes possible at the same time.

Hereinafter, the reason why the composition of the raw material slab is limited to the above range in the present invention will be described. C: 0.02 to 0.08 wt% C is an element useful for improving the crystal structure by utilizing the α-γ transformation during hot rolling, but if less than 0.02 wt%, a good primary recrystallized structure can be obtained. On the other hand, if the content exceeds 0.08 wt%, the decarburization is poor and the magnetic properties are deteriorated, so the content is 0.
It was limited to the range of 02 to 0.08 wt%.

Si: 2.0 to 4.0 wt% Si is a component useful for increasing the electric resistance of the product and reducing the eddy current loss. However, if it is less than 2.0 wt%, the crystal is formed by α-γ transformation during the final finish annealing. Orientation lost, while 4.0
If the content exceeds wt%, there will be a problem with cold rolling.
It was limited to the range of 2.0 to 4.0 wt%.

Mn: 0.03 to 0.2 wt%, S and / or S
e: 0.005 to 0.020 wt% Mn and S and Se combine to form MnS and MnSe useful as inhibitors. However, the amount of Mn is 0.
If the content is less than 03 wt% or the content of S and Se is less than 0.005 wt%, the inhibitor function becomes insufficient, while the content of Mn decreases.
If the content exceeds 0.20 wt% or the S and Se contents exceed 0.020 wt%, the temperature required for slab heating becomes too high, and magnetic deterioration due to poor purification due to short-time annealing becomes remarkable, making it practical. Mn is 0.03 ~ 0.20wt%,
S and / or Se: 0.005 to 0.020 wt%.

Sb: 0.01 to 0.20 wt%, Sn: 0.02 to 0.20 wt%
%, Mo: 0.02-0.05wt% Sb is an element useful for improving the magnetic flux density.
If it is less than 0.01 wt%, its effect is poor, while 0.20 wt%
If the ratio exceeds the limit, the decarburization property deteriorates, so the content was limited to the range of 0.01 to 0.20 wt%. Similarly, Sn effectively contributes to the improvement of the magnetic flux density, but when the content is less than 0.02 wt%, the effect of its addition is poor. On the other hand, when the content exceeds 0.20 wt%, the decarburizing property also deteriorates. Limited to the wt% range. Mo is an element useful for improving surface properties and magnetic properties. If the content is less than 0.02 wt%, the effect of the addition is poor.
If the content exceeds 0.05 wt%, the decarburization property is deteriorated.
Limited to the range of 05 wt%.

Boron: 0.5 to 20 ppm The addition of boron is a characteristic feature of the present invention. By adding a small amount of boron, a good secondary recrystallization can be performed even when the rolling reduction in the final cold rolling is increased. Can be caused. However, if the boron content is less than 0.5 ppm, the completion rate of the secondary recrystallization under a high pressure of 80% or more will be low. On the other hand, the addition of a large amount exceeding 20 ppm will impair the rolling workability. ~ 20 ppm (preferably 2 ~
10 ppm).

Although the essential components have been described above, the present invention may further contain Al and / or Ti. Here, Al and Ti are added to produce good secondary recrystallization even when the rolling reduction in the final cold rolling is strongly reduced as in the case of B. However, if the content is less than 5 ppm, the addition of Al and Ti is made. The effect is poor, while if it exceeds 50 ppm, the incubation period of secondary recrystallization becomes too long and the completion rate of secondary recrystallization in short-time finish annealing becomes low. It is necessary to

In the method for producing a grain-oriented silicon steel sheet according to the present invention, a molten steel containing the above-described components is prepared by a commonly used steelmaking method, and the molten steel is prepared by a continuous casting method or an ingot-bulking method. Slab. After the slab is heated, the slab is hot-rolled to obtain a hot-rolled sheet, and if necessary, hot-rolled sheet annealing is performed. Here, the slab heating temperature is
The temperature of 1100 to 1450 ° C. and the annealing temperature of the hot-rolled sheet are preferably about 900 to 1150 ° C.

Next, a cold rolled sheet having a final thickness is formed by cold rolling once or twice or more with intermediate annealing. During this cold rolling, particularly in the final cold rolling, as shown in FIG. 1, it is necessary to reduce the pressure by 80% or more in order to achieve a high magnetic flux density of the product. It is advantageous to carry out such final cold rolling at a temperature of 100 ° C. or higher. This is because such warm rolling stabilizes the secondary recrystallization and thus improves the magnetic flux density of the product.

Then, after decarburizing annealing, 900 ° C. or more
Short-time final annealing for 3 seconds to 10 minutes in a temperature range of 1200 ° C. or less. The reason why the final finish annealing conditions are limited to the above range is that sufficient secondary recrystallization cannot be expected if the annealing conditions are less than 900 ° C or less than 3 seconds, whereas if the annealing temperature exceeds 1200 ° C or more than 10 minutes, industrial This is because it is difficult to be established.
After the final annealing, a tension coating is applied and baked as required to obtain a product.

[0028]

EXAMPLE A silicon-containing steel slab having the composition shown in Table 4 was heated at 1400 ° C. for 20 minutes and then hot-rolled to a thickness of 2.3 mm.
Hot rolled sheet. The hot-rolled sheet was subjected to hot-rolled sheet annealing at 1000 ° C. for 1 minute, and then finished to a final sheet thickness: 0.34 mm at various final cold rolling reductions and rolling temperatures. At this time, for the steels E to H, intermediate annealing after the first cold rolling was performed at 950 ° C. for 1 minute. On the other hand, the steels C and D were cold rolled once without performing intermediate annealing. Then, after decarburizing annealing at 840 ° C. for 2 minutes, final finishing annealing was performed at 1080 ° C. for 3 minutes for a short time. Table 5 shows the results of examining the secondary recrystallization completion rate and magnetic properties of the product thus obtained.

[0029]

[Table 4]

[0030]

[Table 5]

As is clear from Table 5, all of the grain-oriented silicon steel sheets obtained according to the present invention have excellent magnetic flux densities and iron loss values under a high secondary recrystallization completion rate. I have.

[0032]

As described above, according to the present invention, it is possible to stably obtain a unidirectional silicon steel sheet having excellent magnetic properties by final finishing annealing in a short time, and not only to shorten the manufacturing time, It is very effective in reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the amount of boron and the final cold rolling reduction on magnetic flux density.

Claims (3)

[Claims] C: 0.02 to 0.08 wt%, Si: 2.0 to 4.0 wt%, Mn: 0.03 to 0.2 wt%, Sb: 0.01 to 0.20 wt%, Sn: 0.02 to 0.20 wt% and Mo: A steel slab containing at least one selected from 0.02 to 0.05 wt%, and the remainder substantially having a Fe composition, is hot-rolled,
Next, a series of steps of performing a hot-rolled sheet annealing as necessary, performing cold rolling once or twice with an intermediate annealing therebetween to finish to a final sheet thickness, and then performing decarburizing annealing and final finishing annealing. In producing unidirectional silicon steel sheet by
(1) The silicon-containing steel slab contains 0.005 to 0.020 wt% of one or two selected from S and Se and 0.5 to 20 ppm of boron. (2) Final cold rolling (3) 90
A method for producing a unidirectional silicon steel sheet, wherein a final finish annealing is performed in a temperature range of 0 ° C. or more and 1200 ° C. or less for 3 seconds to 10 minutes for a short time. 2. The production of a grain-oriented silicon steel sheet according to claim 1, wherein the silicon-containing steel slab further contains 5 to 50 ppm of at least one selected from Al and Ti. Method. 3. The method for producing a unidirectional silicon steel sheet according to claim 1, wherein the final cold rolling is performed by warm rolling at 100 ° C. or more.