JPS5833296B2 - Manufacturing method of low iron loss, grain-oriented silicon steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a grain-oriented silicon steel sheet with low core loss.

Unidirectional silicon steel sheets, whose crystals have a (110)<001> orientation and are easily magnetized in the rolling direction, are mainly used as iron cores for transformers and other electrical equipment, and the required magnetic properties are as follows: It is necessary that the excitation characteristics and iron loss characteristics are particularly good.

In particular, in recent years, social demands for energy and resource conservation have become stronger and stronger, and there is a strong desire for low iron loss materials that place particular emphasis on power loss when using electrical equipment.

As is well known, iron loss consists of eddy current loss and hysteresis loss, and since the former accounts for more than % of the total, it is efficient to mainly aim at reducing eddy current loss.

Therefore, it is particularly advantageous to have a method of making the secondary grain size of the product finer without impairing the directionality, and in order to achieve this, the inventor conducted various studies and found that the roll surface roughness during final cold rolling was This invention was completed based on the new finding that it is particularly effective to control the rolling temperature.

That is, in this invention, when cold-rolling a unidirectional silicon steel sheet material (hereinafter simply referred to as material) containing S or Se as an inhibitor at a final cold rolling reduction of 50% or more to obtain the final product thickness, Roll surface roughness during rolling is 0
．． At least 30% rolling is carried out using dull rolls having a diameter of 2 to 2μ, and in addition to this, the steel sheet is rolled at least once at this temperature so that the temperature at the final cold rolling is in the range of 50 to 400℃. It is more desirable to preheat or add intermediate heating.

The method of this invention is particularly effective when applied to materials that generally tend to have large secondary grain sizes, such as unidirectional silicon steel sheets with AlN as an inhibitor, and in particular, the product sheet thickness is 0.15 mm. The effect is even more remarkable when applied to unidirectional silicon steel thin plates in the range of ~0.25 mm.

The development results of this invention will be explained in detail below based on experimental data.

First, FIG. 1 is a diagram showing the relationship between the roll surface roughness during final cold rolling, the average grain size of the product, and the iron loss.

Materials are C: 0.042%, Si: 3.15%, Mn: 0
．． 070%, Se: 0.020%, Sb: 0
．． 3. Omrrtq hot rolled sheet containing 0.030%.

After first cold rolling this material to an intermediate thickness of 0.70 mm,
Intermediate annealing was performed at 50°C for 5 hours, and then secondary cold rolling was performed to reduce the temperature to 0.3
When finishing a product with a roll surface roughness of 0 mm,
Comparisons were made between rolls rolled using six types of dull rolls of 1 to 5μ.

However, the final pass was finished using a smooth roll with a surface roughness of 0.1μ.

After this, decarburization annealing at 800°C x 5ml and 1200°C x
As shown in Figure 1, the average secondary particle size and iron loss of the product obtained by finish annealing in hydrogen for 10 hours were finished with a roll having a surface roughness of 0.2 to 2μ, which meets the conditions of this invention. The secondary grain size was finer and the iron loss was lower.

Next, FIG. 2 shows two types of products with a thickness of 0.2 mm, especially when AlN is also included as an inhibitor.

It shows the influence of the roll surface roughness during final cold rolling for 0.30 mm, that is, C: 0.045%, Si: 3
．． 08%, Mn: 0.080%, S: 0.026%, acid soluble AIj: 0.028%, N: 0.0075%
Contains.

When finishing a 2.0 mm thick hot-rolled sheet into 0.30 mm and 0.20 mm products by one cold rolling after heating to 1100'C5m1n, the surface roughness of the roll was set to 6 types as in the case of Fig. 1. Comparisons were made across the board.

As shown in Figure 2, the influence of roll roughness is more pronounced than in Figure 1, and when the roll surface roughness is between 0.2 and 2μ, the secondary grain size becomes fine and low iron loss is achieved. is being given.

In particular, the effect of the present invention is clear in the case of the solid line where the product board thickness is thin, and it can be seen that a product with W1□10<0.90 W/kg can be easily obtained.

By the way, regarding the manufacturing method of low core loss grain-oriented silicon steel sheets with a product thickness of 0.15 to 0.25 mm, the inventors have already developed a method for reducing the secondary grain size of the product and reducing the amount of forsterite in the surface film. W1715o by controlling
However, even in that case, the secondary particle size tends to become coarse, especially when klN is included as an inhibitor, and it is not necessarily stable. There was no way to overcome the drawback of not being able to replace low iron loss materials.

The method of the present invention advantageously solves the above-mentioned problems, and its major feature is that the grain size can be made finer without impairing the directionality, and a low core loss material can be stably obtained.

It was shown here that by rolling with dull rolls with a roll roughness of 0.2 to 2μ, the secondary grain size becomes fine and a material with low iron loss can be obtained. It is not necessary to roll with rolls, and if the final cold rolling reduction ratio is set to 50% or more and at least 30% of the reduction is rolled with dull rolls having the above-mentioned surface roughness, grain size refinement and low core loss can be achieved. The effect can be changed.

Naturally, when rolling with rolls having a large roughness, the smoothness of the surface of the cold-rolled sheet deteriorates.

On the other hand, regarding the relationship between the surface smoothness and properties of the final product, it was found in the 5th year of the Tokuko Showa era that it was possible to use materials with lower core loss by increasing the smoothness.
2-24499.

Therefore, even when rolling with rolls having a rough surface roughness, the surface roughness is 0.2μ at least for the final pass.
It is necessary to finish with the following smooth rolls.

Next, the relationship between the steel sheet temperature and the average grain size or iron loss value of the product when final cold rolling is performed using rolls having the above-mentioned surface roughness will be described.

Figure 3 shows that when finishing a steel plate with the same components and the same process as in Figure 2 to a final cold rolling of 0.20 mm, either preheating or intermediate heating is performed before or during cold rolling. Or by adding both at least once, the temperature of the steel plate during cold rolling can be varied in the range of 20 to 600°C to increase the maximum temperature of the steel plate during rolling (measured with a surface thermometer for each pass) and the secondary grain size of the product. This shows the relationship between iron loss and iron loss.

The roll roughness was compared between two conditions, 0.16μ and 0.32μ, and the steel plate temperature during rolling was 50 to 400μ.
If the roll roughness is in the range of 0.2 to 2μ, according to this invention, the secondary particle size will be smaller and the core loss will be lower than that outside the range. It is clear that especially low iron loss can be obtained.

By the way, by rolling using dull rolls with a surface roughness of 0.2 to 2μ, the secondary particle size of the product becomes finer.
The reason why the iron loss of the product decreases has not yet been completely elucidated at this point, but the inventor's idea is that increasing the frictional force between the material and the rolls during rolling will reduce the iron loss near the surface. We believe that this is because the number of secondary crystal nuclei in the orientation increases.

The reason why iron loss is reduced by making the secondary grain size finer is that the magnetic domain becomes finer and the moving distance of the domain wall during the magnetization process is shortened. It is effective to make it fine, and for this purpose it is necessary that the roll roughness in the direction parallel to the rolling direction satisfies the conditions of the present invention.

However, when the roll roughness exceeds 2μ, the surface crystal orientation becomes more random, and although the secondary grain size becomes finer, it grows to an unfavorable orientation, resulting in deterioration of the magnetic properties.

The effect of increasing the rolling temperature is to similarly increase the number of secondary recrystallization nuclei, but at the same time, coarse elongated grains with unfavorable orientations in the center layer are subdivided, making it easier for Goss nuclei formed near the surface to grow. It is also effective in forming a matrix consisting of a homogeneous primary grain structure.

On the other hand, when the temperature exceeds 400° C., the number of Goss nuclei decreases significantly due to the randomization of crystal orientation, so that the properties deteriorate on the contrary.

Next, this invention will be explained step by step.

First, the unidirectional silicon steel sheet material to which this invention is particularly suitable can be produced by any known method, but the material components include Si: 2.0 to 4.0%, C
:0.02-0.08% It is necessary to contain one or two of S or Se in a total amount of 0.010-0.040%.

In addition to these, in order to obtain products with high magnetic flux density, acid-soluble AA O,010-0.040%, NO,00
4 to 0.020%, and SbO, 1% or less.

Si is a necessary element to increase the electrical resistance of the product and reduce eddy current loss. If the amount is less than the lower limit of 2.0%, the crystal orientation will be damaged due to α-γ transformation during the final high-temperature finish annealing. Exceeding the limit of 40% will cause problems in terms of cold rollability.

C is used in the hot rolling process to make the hot rolling texture appropriate by utilizing an appropriate amount of α-γ transformation, and for this reason, 0.02
A range of 0-0.080% is essential.

S and Se function as inhibitors, and the amount of either one or the sum of both is 0.01.
0 to 0.040% is essential; if it is more or less than this, secondary recrystallization will be incomplete and sufficient characteristics will not be obtained.

Acid-soluble M and N amounts are required to obtain the necessary amount of AAN as an inhibitor and its desired dispersion.
For that purpose acid soluble kl is 0.010-0.040
%, N needs to be contained in the material in the range of 0.004 to 0.020%, and furthermore, it coexists with AlN and s
If sb is contained in an amount of 0.1% or less, it is effective in further increasing the stability of properties, and if the amount of sb exceeds 0.1%, not only will iron loss be slightly impaired, but the product's This is set as the upper limit because of the presence of wrinkles that deteriorate the adhesion of the forsterite film formed on the surface.

The material containing these components is made into a slab according to a conventional method, heated at a temperature of 1300°C or higher for 1 to 3 hours to dissolve MnS, MnSe, and A7N, and then hot rolled to a slab of 1.5 to A hot-rolled sheet with a thickness of 3.0 mm is used in the process of the present invention.

This hot-rolled sheet, that is, the unidirectional silicon steel material, is finished to the final product thickness by cold rolling once or twice, including intermediate annealing if necessary. 850-11 for tissue adjustment
．． It is preferable to apply a heat treatment of 0.5 to 10 ml at 50'C, and the subsequent cooling rate should be rapidly cooled to 300°C within 300 seconds to stabilize the electromagnetic properties. is preferred.

The final cold rolling requires a cold rolling reduction of 50% or more,
The roll surface roughness at this time is the most important point for achieving the purpose of the present invention, and the roll surface roughness is 0.2 to 0.2 for the cold rolling stage which accounts for at least 30% of the final cold rolling reduction. It is essential to roll with 2μ dull rolls.

In order to further ensure the effects of the present invention, when rolling with dull rolls having a surface roughness of 0.2 to 2μ, at least preheating or intermediate heating is performed in a temperature range of 50 to 400°C before or during cold rolling. It is effective to carry out the cold rolling once so that the temperature of the steel sheet during the cold rolling is in the range of 50 to 400°C.

The cold-rolled plate is then rolled for 1-10m at a temperature of 750-8800C.
After decarburizing annealing in 1N wet hydrogen and applying a separating agent such as MgO, annealing is performed in hydrogen or a mixed gas of hydrogen and nitrogen at a temperature range of 1100 to 1250°C for 1 hour for the purpose of secondary recrystallization and purification. Add the above high-temperature finishing annealing treatment.

After this, an insulating coating is applied to the surface to produce a product, and the secondary particle size of the product thus obtained is fine and the iron loss is extremely low.

Next, the present invention will be explained with reference to Examples.

Example IC: 0.045%, Si: 3.15%, Mn: 0
．． 079%, Se: 0.022% and Sb: 0
．． A continuously cast slab of silicon steel containing 0.030% was heated at 1330° C. for 3 hours** and then hot rolled to obtain a hot rolled plate with a thickness of 3.0 mm.

Next, after normalizing treatment at 950°C for 5 ml, the intermediate thickness was made to 0.70 mw by first cold rolling, and intermediate annealing was performed at 950°C.
After rolling at 50°C in 5ml of hydrogen, secondary cold rolling was performed to reduce the
．． Two product thicknesses were produced: 20 mm and 0.30 mm.

For these, during final cold rolling, the surface roughness of the roll is 0.
．． A comparison was made between one in which all passes were finished with 12μ smooth rolls and one in which 0.35μ dull rolls were rolled for the remaining passes except the final pass.

In addition, some samples were preheated at 300° C. for 3 hours before final cold rolling.

The cold-rolled sheet was decarburized at 8000C for 25 min in a hydrogen and nitrogen mixed gas atmosphere with a dew point of 60°C, coated with MgO, and then heated to 1200C.
Finish annealing was performed in hydrogen at 10°C for 10 hours.

The magnetic properties and average secondary particle size of the final product obtained are shown in Table 1.
2 of the products rolled by the method of this invention.
The secondary grain size was particularly fine and the iron loss was low.

Example 2 C: 0.048%, Si: 3.10%, Mn: 0.0
75%, S: 0.020%, acid soluble Affl: 0.0
A continuously cast silicon steel slab containing 28% N and 0.0080% N was heated at 1360°C for 3 hours and then hot rolled to form 1
．． A hot-rolled sheet with a thickness of 6 mm was obtained.

Next, continuous furnace annealing was performed at 1100'C in a 5ml nitrogen atmosphere, and a rapid cooling process was added in which the time required for the annealed corrugated steel plate to reach 400°C was approximately 60 seconds.

Next, this steel plate was cold-rolled to obtain a product with a thickness of 0.20 mm. Products were produced by rolling with dull rolls having a surface roughness of 0.35μ and 0.60μ.

In addition, some samples may be preheated to 300°C for 3 hours or heated to 300°C for 3 hours.
A steel plate with intermediate heating of °CIHr was made, and the surface temperature of the steel plate was measured for each pass.

The cold-rolled sheet was decarburized at 800°C in a 5m1n hydrogen and nitrogen mixed gas atmosphere with a dew point of 60°C, coated with MgO, and then heated to 1200°C.
High temperature finish annealing for secondary recrystallization and purification was performed in hydrogen for 10 hours.

The magnetic properties and average secondary particle size of the final product obtained are shown in Table 2.
2 of the products rolled by the method of this invention.
The secondary grain size was particularly fine and the iron loss was low.

[Brief explanation of the drawing]

Figure 1 shows the roll surface roughness (μ) during final cold rolling and the iron loss W1□/ of the product when Se-Sb is used as an inhibitor.
Figure 2 shows the relationship between roll roughness (μ) and product iron loss W during final cold rolling when klN and S are used as inhibitors.
A chart showing the relationship between 1715a (w/kg) and average grain size (distance) for both product plate thicknesses of 0.20 mm and 0.30 mm. Figure 3 shows the maximum temperature of the steel plate during final cold rolling. (℃) and product iron loss W1715o (w
2 is a chart showing the relationship between the average grain size (/kg) and the average crystal grain size (g) when rolled with rolls having two types of surface roughness (μ).

Claims (1)

[Claims] 1 By weight, Si: 2.0 to 4.0%, C: 0.0
2 to 0.08%, and at least one of S and Se alone or in total 0.010 to 0.040%
and optionally acid-soluble AIt: 0.01
A unidirectional silicon steel sheet material having a composition containing 0 to 0.040% N, 0.004 to 0.020% N, and further Sb: 0.10% or less is subjected to cold rolling processing one or more times. In a method for producing grain-oriented silicon steel sheets, which is performed in conjunction with necessary intermediate annealing treatment, and further decarburized annealing and high-temperature finish annealing treatment, the final cold rolling reduction ratio of the above cold rolling process is set to 50% or more, and then Rolling with dull rolls with a roll surface roughness of 0.2 to 2μ is performed during the rolling process, excluding at least the final pass, to make the secondary grain size of the product steel plate fine. A manufacturing method for grain-oriented silicon steel sheets featuring low core loss. 2. Claim 1, wherein rolling with dull rolls is warm working in a temperature range of 50 to 400°C by at least one preheating or intermediate heating applied to the material to be rolled before or during the final cold rolling. Method described. 3. The method according to claim 1 or 2, wherein the product steel sheet has a thickness of 0.15 to 0.25 m and an average grain size of 1 to 6.