JPH1036914A - Production of grain oriented electric steel sheet excellent in magnetic characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain an excellent magnetic characteristic by regulating an operational condition at the first time of cold-rolling after intermediate annealing. SOLUTION: The first time of cold-rolling after intermediate annealing is executed with a tandem rolling-mill. In such a case, a steel sheet temp. at outlet side of the last pass in the tandem rolling is made to 100-300 deg.C, and statical ageing is promoted by coiling and holding in this temp. range and, thereafter, the cold-rolling is executed to restrain the biting steel sheet temp. to <=300 deg.C while holding the excellent magnetic characteristic, and the attaching by burning of rolling oil to the steel sheet as a problem at the time of rolling in high temp. can be eliminated. As for the coiling and holding temp., though such an excellent product as to exceed 1.9T magnetic flux density is obtd. in a short time and enough magnetic characteristic can be obtained only by allowing to stand in the atmosphere after the coiling, it is desirable further to keep the product in the coiling temp. range of 100-300 deg.C for >=20min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention proposes a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties by devising a cold rolling process.

[0002]

2. Description of the Related Art In a cold rolling process for producing a grain-oriented electrical steel sheet, for example, Japanese Unexamined Patent Publication No. 50-16610 (Colding to obtain a high magnetic flux density unidirectional silicon steel sheet (band) having excellent characteristics) is disclosed. As disclosed in the “Rolling method”, the cold-rolled sheet is heat-treated at a low temperature during rolling (hereinafter, referred to as aging treatment),
It is known that magnetic properties are improved, such as reduction of iron loss and improvement of magnetic flux density.

This is a method in which dislocations generated by rolling are fixed by utilizing the diffusion phenomena of C and N, whereby further shear deformation is advanced to improve the rolling texture. However, in the case of tandem rolling, a sufficient heating holding time cannot be obtained between the stands during the rolling,
The diffusion of C and N was not sufficient, and it was difficult to sufficiently improve the magnetic properties.

[0004] As another means for improving the magnetic properties, it is known to perform warm rolling. This is different from the static aging in which the aging treatment is performed between the cold rolling passes as described above. By increasing the temperature of the steel sheet during rolling, dislocations generated by rolling deformation are immediately fixed by C and N. This method uses the dynamic aging effect.

[0005] As a warm rolling method by tandem rolling utilizing dynamic aging, Japanese Patent Application Laid-Open No. 1-215925 (a method of cold rolling a grain-oriented electrical steel sheet) and Japanese Patent Application Laid-Open No. 1-218705 are disclosed.
In the cold rolling process by a tandem rolling mill, these are set to at least 300 to 500 ° C. in the temperature of a rolled sheet that bites into a work roll pair in at least one pass. 100 to 500 ° C.

The optimum temperature for dynamic aging of a steel sheet depends on its strain rate, and the higher the rolling speed, the higher the optimum temperature. When rolling with a tandem rolling mill If the line speed is increased in consideration of productivity, the optimum temperature will inevitably increase, and if aging between passes cannot be expected as in a tandem rolling mill, a higher warm rolling will be required. Although a temperature is required, when the steel sheet temperature exceeds 300 ° C., the rolling oil is locally seized on the steel sheet surface, the friction coefficient at the time of rolling becomes unstable, and the finished sheet thickness varies. In the area where the rolling oil is burned on the surface of the steel sheet, the surface oxide film (subscale) becomes non-uniform in the subsequent decarburization and primary recrystallization annealing, resulting in poor film formation and patterns on the product sheet. There is a problem that the appearance is deteriorated and the magnetic properties are deteriorated due to poor adhesion of the coating.

For the above reasons, Japanese Patent Application Laid-Open No. 4-120215 (a method for producing a grain-oriented silicon steel sheet having excellent magnetic properties and surface properties) discloses that the steel sheet surface temperature at the side of the rolling stand is 30 ° C.
There is proposed a method in which the temperature is set to less than 0 ° C. and the deterioration of the magnetic properties due to the temperature is controlled by controlling the scale removal treatment before cold rolling. However, when pretreatment before cold rolling is performed by such a method and tandem rolling is performed at a temperature lower than 300 ° C., it is still not sufficient to obtain a product having excellent magnetic properties stably. Was.

[0008]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problem of rolling oil seizure in performing tandem warm rolling in order to improve productivity, and achieves a stable high magnetic flux density. It is an object of the present invention to propose a method for manufacturing a grain-oriented electrical steel sheet that can obtain the following.

[0009]

The gist of the present invention is as follows. Hot rolling is performed using a silicon steel slab for grain-oriented electrical steel sheets as a raw material, cold rolling is performed before and after the intermediate annealing, respectively, and cold rolling is performed twice in the subsequent stage to final cold rolling. In order to manufacture a grain-oriented electrical steel sheet through a series of steps of applying an annealing separator after decarburizing annealing and then applying a final finishing annealing after decarburizing annealing, one step after the intermediate annealing is performed.
The first cold rolling is performed in a tandem rolling mill, and at least 1
Set the temperature of the steel plate above the pass in the range of 100 ° C to 300 ° C and the temperature of the steel plate on the exit side of the final stand at 100 ° C to 300 ° C.
The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that it is wound around a coil in the range of ° C., left for 20 minutes or more, and then subjected to a second cold rolling to a final cold-rolled sheet thickness (first example) invention).

[0010] In the above-mentioned process, the temperature of the steel sheet on the exit side of the final stand is set in the range of 100 ° C to 300 ° C, and the coil is wound around the coil.
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties to make the final cold-rolled sheet thickness by the second cold rolling (second invention).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an experimental example which has achieved the present invention will be described below. As material, C: 0.06
5 wt% (hereinafter simply expressed as%), Si: 3.25%, sol.A
l: 0.025%, N: 0.0080%, Se: 0.024%, Sb: 0.029
%, After heating the steel ingot containing steel at a high temperature, the plate thickness: 2.3mm
Hot-rolled. Then, after performing hot-rolled sheet annealing, the sheet was cold-rolled to an intermediate sheet thickness of 1.6 mm and subjected to intermediate annealing at 1000 ° C. for 1 minute. When the first cold rolling after the intermediate annealing is performed to a sheet thickness of 0.8 mm by a tandem rolling mill, the temperature of the steel sheet on the incoming side of the final pass is set to room temperature (a temperature similar to the coolant) and 200 ° C. Steel plate temperature between 50 ℃ and 350 ℃
The cooling water amount was adjusted so as to fall within the range described above, and once cooled to room temperature as it was or immediately, the coils were wound.

[0012] Of these coils, the coil wound as it is is kept at the same temperature as the exit side steel sheet for 20 minutes and 2 hours, respectively, and the other cooled and wound coil is reheated to a temperature of 200 ° C. For 20 minutes and 2 hours, respectively.

Thereafter, these coils were further cold-rolled (the second cold-rolling after the intermediate annealing) and each had a thickness of 0.23.
mm to a final cold rolled sheet thickness.

Next, decarburization and primary recrystallization annealing were performed at 840 ° C. for 2 minutes in a wet hydrogen atmosphere, and an annealing separator containing MgO as a main component was applied, followed by secondary recrystallization annealing.

The magnetic flux density (B ₈ ) of each product sheet thus obtained was examined. Table 1 summarizes the processing conditions and the measurement results of the magnetic flux density.

[0016]

[Table 1]

As is clear from Table 1, the temperature of the steel sheet on the entrance side of the final stand was set at 200 ° C., and the temperature of the steel sheet on the exit side was set at 160 ° C.
And 250 ° C, the magnetic flux density (B ₈ ) shows a value of 1.92T or more, and the holding time after winding on the coil or the holding time after reheating to a temperature of 200 ° C is 20 minutes. The magnetic flux density is improved when the time is set to 2 hours.

However, as compared with the case where cooling is performed once on the exit side of the final stand and then reheating is performed, a particularly excellent magnetic flux density is obtained when the film is wound as it is without cooling. Hold time after taking 20
It can be seen that a sufficiently high magnetic flux density can be obtained even for minutes.

Next, the operation and effect of the present invention will be described based on the above experimental results. Cold rolling-When the steel sheet after the intermediate annealing is warm-rolled by a tandem rolling mill, at least 1
The texture after cold rolling and after decarburizing annealing can be improved by setting the bite steel sheet temperature in the range of 100 ° C. to 300 ° C. in the pass and above. The above experimental example
Although the result is a result of the steel sheet temperature only on the entry side of the last pass of the tandem rolling, the present invention is not limited to only the last pass.

Although the mechanism of the texture improvement is not necessarily clear, one of the possible reasons is that the shear deformation during rolling is promoted by the dynamic aging effect.
If the bite steel sheet temperature is less than 100 ° C., the dynamic aging effect is small, and it is presumed that this cannot be compensated for by combining the static aging effect after winding as in the present invention.

On the other hand, it is considered that the higher the bite steel sheet temperature, the more advantageous the magnetic properties. However, at temperatures exceeding 300 ° C., as described above, the rolling oil was locally seized on the steel sheet surface, and the coefficient of friction at the time of rolling was not constant, resulting in a variation in the finished plate thickness and also the rolling oil was seized. In the part, the surface oxide film (sub-scale) becomes non-uniform in the subsequent decarburization and primary recrystallization annealing, the appearance deteriorates due to the poor formation of the coating on the product plate and the occurrence of the pattern, and the poor adhesion of the coating There is a problem that the magnetic characteristics are deteriorated.

Therefore, in the present invention, the temperature of the steel sheet on the exit side of the final pass of the tandem rolling is set in the range of 100 ° C. to 300 ° C., and the aging is promoted by winding and holding in this temperature range. By doing so, it is possible to suppress the bite steel sheet temperature to a temperature of 300 ° C. or less while maintaining excellent magnetic properties, and to eliminate seizure of rolling oil on the steel sheet, which is a problem during high-temperature rolling.

If the temperature of the exit side steel sheet in the final pass of the tandem rolling is less than 100 ° C., it is necessary to maintain the temperature for a long time, which is disadvantageous in terms of improving productivity. Also, 30
Even when the temperature exceeds 0 ° C., deterioration of the magnetic properties is observed. The reason for this is that if the exit temperature is too high, exceeding 300 ° C., the diffusion of C and N in the steel will proceed too much, and the precipitation of carbides or nitrides will occur in a short time. It is considered that this has an adverse effect on the formation of a texture or decarburization during decarburization annealing and deteriorates magnetism.

Also, when the steel sheet is once cooled and then reheated to be aged, the product having a shorter time and superior magnetic properties is obtained when the steel sheet is wound and held at a high temperature and aged. Although it is not clear why the sheet is obtained, it is thought that the static aging time can be reduced by leaving the final stand in tandem rolling and winding and holding the coil at a high temperature, thus increasing productivity. Becomes possible. Here, in the present invention, an excellent product having a magnetic flux density exceeding 1.9 T can be obtained by holding for a short time, so that sufficient magnetic properties can be obtained only by leaving the coil and leaving it in the air, In order to obtain a product having a high magnetic flux density and a low iron loss, it is effective to maintain the winding temperature in a range of 100 ° C to 300 ° C for a predetermined time.

Next, the preferred composition range of the silicon steel material to which the present invention is applied and the preferred process for producing a grain-oriented electrical steel sheet will be described below.

Component Composition The component structure of a material for a normal oriented silicon steel sheet may be used, and the preferred ranges thereof are as follows.

C: 0.02 to 0.15% C is an important component that improves the crystal structure by utilizing the γ-α transformation during hot rolling and contributes to the improvement of the magnetic properties as intragranular fine carbide. However, if the content is less than 0.02%, the effect is poor, and if it exceeds 0.15%, subsequent decarburization becomes difficult. Therefore, its content is 0.02--0.
A range of 15% is preferred.

Si: 2.0 to 4.5% Si is a useful component for improving iron loss characteristics by increasing electric resistance. However, if the content is less than 2.0%, the electric resistance of the steel sheet becomes small, resulting in excessive current loss. As a result, good iron loss characteristics cannot be obtained, and if it exceeds 4.5%, cold rolling becomes difficult. Therefore, its content is preferably in the range of 2.0 to 4.5%.

In addition to these C and Si, the material for grain-oriented silicon steel sheets can selectively remove only goss grains by suppressing grain growth other than the goss orientation from the primary and secondary recrystallized structures. It is important to include an inhibitor-forming component having a function essential for secondary recrystallization, ie, growth to a certain extent.
There are two types of inhibitors known: those that function by being precipitated in grains, such as AlN and MnSe, MnS, and those that function by segregating at grain boundaries, such as Sb and Sn.

When an AlN-based inhibitor is used sol.Al: 0.01 to 0.05% When the content of sol.Al is less than 0.01%, the magnetic flux density decreases,
If it exceeds 0.05%, the secondary recrystallization becomes unstable. Therefore, the content is preferably in the range of 0.01 to 0.05%.

N: 0.004 to 0.012% If the content of N is less than 0.004%, the amount of AlN inhibitor becomes insufficient and the magnetic flux density decreases. If it exceeds 0.012%, surface defects called blisters occur frequently. Therefore, its content is preferably in the range of 0.004 to 0.012%.

When MnSe or MnS-based inhibitors are used: Mn: 0.03 to 0.30% When the content of Mn is less than 0.03%, the absolute amount is insufficient as an inhibitor component. The ability to suppress growth decreases. Therefore, its content is preferably in the range of 0.03 to 0.30%. Se + S: 0.01 to 0.05% Se and S are used alone or in a total content of 0.01.
%, The absolute amount is insufficient as an inhibitor component,
If it exceeds 0.05%, purification by finish annealing becomes difficult. Therefore, the content is preferably in the range of 0.01 to 0.05% in either case of a single use or a total use in combination.

Further, in the present invention, Cu, Sn, Sb, Mo, Te, Bi, P and the like can be used alone or in combination as a grain boundary segregation type inhibitor. In manufacturing a high-grade grain-oriented electrical steel sheet having particularly excellent magnetic properties, it is advantageous to use not only a precipitation type but also an auxiliary inhibitor of a grain boundary segregation type to maximize these inhibitory effects.

Manufacturing process The molten steel adjusted to the above-mentioned preferable composition by the conventional steelmaking method is converted into a slab having a predetermined thickness by a continuous casting method or an ingot-bulking method, and then the inhibitor components Al, Se, S Heat to a temperature range of 1350 to 1450 ° C to completely dissolve solids. After this heating, hot rolling is performed, and then, hot rolled sheet annealing for uniformizing the structure and stabilizing the secondary recrystallization is performed as necessary.

Thereafter, according to the present invention, as described above, cold rolling is performed in each of the first and second stages with the intermediate annealing therebetween, and cold rolling is performed twice in the second stage to obtain a final cold-rolled sheet thickness. .

Thereafter, after decarburizing annealing, MgO
After applying an annealing separating agent containing as a main component, final finishing annealing is performed to obtain a product plate. It is also advantageous to subsequently apply a phosphate-based overcoat.

[0037]

【Example】

Example 1 Steel ingots A to D having the component compositions shown in Table 2 were each hot-rolled to a sheet thickness of 2.2 mm, and then subjected to a hot-rolled sheet annealing of 1000 ° C. for 1 minute followed by rapid cooling.

[0038]

[Table 2]

Then, after cold rolling to a sheet thickness of 1.5 mm, intermediate annealing was performed after heating at 1100 ° C. for 2 minutes and then quenching. After the intermediate annealing, the first cold rolling was performed by tandem warm rolling. In rolling to a thickness of 0.8 mm, the temperature of the steel sheet on the entrance side of the fourth stand was adjusted to 252 ° C by adjusting the flow rate of the roll coolant on the exit side of the third stand of the tandem rolling mill with four stands. By controlling the flow rate of the roll coolant on the side, the exit side steel sheet temperature was set to 84 ° C., 238 ° C., and 351 ° C., respectively, immediately wound around a coil, and left in the atmosphere for 30 minutes. After that, the second cold rolling is performed after the intermediate annealing by tandem rolling,
Each final cold rolled sheet thickness: 0.22 mm.

Then, after decarburizing annealing at 840 ° C. for 2 minutes in wet hydrogen, MgO containing 5% TiO ₂ was applied as an annealing separating agent, and final finishing annealing at 1200 ° C. for 10 hours was performed. Each product plate was obtained.

The magnetic properties, coating appearance, coating adhesion and the like of each product plate thus obtained were investigated. Table 3 summarizes the results of these investigations.

[0042]

[Table 3]

As is apparent from Table 3, the applicable example of the present invention in which the temperature of the steel sheet exiting from the fourth stand in the first rolling after the intermediate annealing was 238 ° C. was a comparative example when any steel ingot was used. It shows excellent magnetic properties as compared with that of the above, and the film appearance and the adhesion of the film are also good.

Example 2 A steel ingot having the component composition of D in Table 2 was hot-rolled to a thickness of 3.0 mm, and then subjected to a hot-rolled sheet annealing at 1000 ° C. for 1 minute followed by rapid cooling.

Then, after cold rolling to a sheet thickness of 2.0 mm, intermediate annealing was performed by heating at 1100 ° C. for 2 minutes followed by rapid cooling, and then the first cold rolling after the intermediate annealing was performed by tandem warm rolling. Intermediate plate thickness: When rolling to 1.0 mm, the temperature of the steel plate on the entrance to the fourth stand is controlled to 90 ° C., 198 ° C. and 330 ° C. by controlling the flow rate of the roll coolant on the exit side of the third stand of the tandem rolling mill of all four stands. ° C and the fourth
By adjusting the flow rate of the roll coolant on the outlet side of the stand, the temperature of the steel sheet on the outlet side was set to 224 ° C.

Subsequently, the coil is immediately wound around a coil and is exposed to the air.
Left for 30 minutes, immediately wound on a coil, then 200
The coil manufactured under the following three conditions: one that was kept for 30 minutes in a heat retention device at a temperature of ℃, one that was once cooled to room temperature, wound around a coil, then reheated to a temperature of 200 ° C. and kept for 30 minutes. Furthermore, the final cold-rolled sheet thickness was each set to 0.30 mm by tandem rolling.

Then, after decarburizing annealing at 840 ° C. for 2 minutes in wet hydrogen, MgO containing 5% TiO ₂ was applied as an annealing separating agent, and then final finishing annealing at 1200 ° C. for 10 hours was performed. Each product plate was obtained.

With respect to each of the product sheets thus obtained, the magnetic properties, the appearance of the coating, the adhesion of the coating, and the like were examined. Table 4 summarizes the results of these investigations.

[0049]

[Table 4]

As is clear from Table 4, the temperature of the steel sheet on the exit side of the fourth stand in the first rolling after the intermediate annealing was set at 198 ° C., wound on a coil and left in the atmosphere for 30 minutes, and wound on the coil. When the sample is kept at a temperature of 200 ° C. for 30 minutes, the conforming example has excellent magnetic properties, and also has good coating appearance and coating adhesion.

[0051]

According to the present invention, in producing a grain-oriented electrical steel sheet as a final cold-rolled sheet thickness by performing cold rolling twice after the intermediate annealing, the first cold rolling after the intermediate annealing is performed by a tandem rolling mill. The rolling temperature conditions and the holding conditions after coil winding are specified. According to the present invention, a grain-oriented electrical steel sheet having excellent magnetic properties and coating appearance and adhesion is stabilized by a tandem rolling mill. It is possible to increase the productivity.

Claims (2)

[Claims] 1. A hot-rolling process using a silicon steel slab for grain-oriented electrical steel sheets as a raw material, performing cold rolling in each of a preceding stage and a subsequent stage with intermediate annealing therebetween, and performing cold rolling twice in a subsequent stage. Go to the final cold rolled sheet thickness, then, after decarburizing annealing
In producing a grain-oriented electrical steel sheet by a series of steps of applying an annealing separator and then performing a final finish annealing, the first cold rolling of the middle stage after the intermediate annealing is performed by a tandem rolling mill, and at least one pass is performed. 100 ℃
Up to 300 ° C and the temperature of the steel sheet on the exit side of the final stand in the range of 100 ° C to 300 ° C, wind it around a coil, leave it for 20 minutes or more, and then make the final cold-rolled sheet thickness by the second cold rolling. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties. 2. A hot-rolling process using a silicon steel slab for a grain-oriented electrical steel sheet as a raw material, performing cold rolling in each of a preceding stage and a subsequent stage with intermediate annealing therebetween, and performing cold rolling twice in a subsequent stage. Go to the final cold rolled sheet thickness, then, after decarburizing annealing,
In producing a grain-oriented electrical steel sheet by a series of steps of applying an annealing separator and then performing a final finish annealing, the first cold rolling of the middle stage after the intermediate annealing is performed by a tandem rolling mill, and at least one pass is performed. 100 ℃
The coil is wound around a coil with the temperature of the steel sheet on the exit side of the final stand in the range of 100 ° C to 300 ° C and maintained at the winding temperature range for at least 20 minutes. A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, comprising: