JPH0499130A - Production of low-iron loss grain oriented electrical steel sheet - Google Patents

Abstract

PURPOSE:To produce the low-iron loss grain oriented electrical steel sheet having stable magnetic characteristics locally forming linear grooves of the depth satisfying specific equation on the surface of the blank material of the grain oriented electrical steel sheet, subjected to cold rolling down to a specific sheet thickness, then subjecting this blank material to decarburization annealing, etc. CONSTITUTION:The linear grooves of the depth satisfying the following equation are locally introduced to the surface of the grain oriented electrical steel sheet after the cold rolling down to the final product thickness to produce the low-iron loss grain oriented electrical steel sheet, at the time of producing the grain oriented electrical steel sheet by subjecting the blank material of the grain oriented electrical steel sheet cold rolled down to the final product thickness of <=0.27mm to the decarburization annealing, then to the final finish annealing: logd>=0.6Ra+04, d: groove depth (mum), Ra: the surface average roughness (mum) of the final cold rolled sheet. The depth of the groove is preferably about <=70mu, the width of the grooves preferably about <=300mu, and the interval in the rolling direction preferably about >=1mm.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a method for manufacturing a low core loss grain-oriented electrical steel sheet,
This is particularly aimed at stabilizing the properties of thin electrical steel sheets.

(Prior Art) Grain-oriented electrical steel sheets are mainly used as core materials for transformers and other electrical equipment, or in order to increase efficiency in such applications, they are used to reduce the iron loss of the steel sheets used. is considered important.

Grain-oriented electrical steel sheets have a so-called Goss orientation texture with a +1101 plane parallel to the rolling surface and a <001> axis along the rolling direction, and by increasing the degree of accumulation of such Goss orientations, the steel sheet becomes It is possible to reduce hysteresis loss.

However, as the degree of integration increases, the crystal grains become larger, which in turn increases the magnetic domain width, and as a result, the eddy current loss conversely increases. Therefore, the iron loss, which is the sum of the hysteresis loss and the eddy current loss, cannot be expected to be significantly improved simply by increasing the degree of integration of the Goss orientation.

As a means to solve this problem, for example,
Japanese Patent No. 2252 proposes a method of irradiating the surface of a steel plate with a racer to subdivide magnetic domains, thereby reducing iron loss. With this method, iron loss is significantly reduced, and the plate thickness is 0.
．． 23mm steel plate has iron loss W! 7150 (magnetic flux density 1.
7T, 50Hz) of 0.85W/kg or less can now be manufactured.

However, the above method still has a problem in that the laser irradiation effect is lost when heat treatment at about 600° C. or higher, such as strain relief annealing, is performed after laser irradiation. Therefore, it cannot be used as a winding type transformer that requires strain relief annealing as described above.

On the other hand, as a method for producing a low core loss grain-oriented electrical steel sheet that can also be used in winding type transformers, Japanese Patent Application Laid-Open No. 61117218 proposes a method of forming grooves by applying a load to a finish annealed electrical steel sheet. 61-186420 discloses a method in which the coating of a finish-annealed electrical steel sheet is locally removed with a racer or the like, and then plated with sb or the like, and furthermore, JP-A-61-1864
Japanese Patent No. 117284 proposes a method in which the film of a finish-annealed electrical steel sheet is locally removed using a laser or the like, and then a part of the base iron is removed by pickling or the like.

However, with these methods, the space factor of the steel plate decreases due to burrs caused by loading and the recoating that is inevitably required due to the processing of finish annealed steel plates, and the actual iron loss characteristics are not as good as the material characteristics. Also, there were drawbacks such as increased costs due to re-coating.

In this regard, the inventors have previously published Japanese Patent Application Laid-Open Nos. 59-197520 and 63
In Japanese Patent No. 42332, a method of introducing grooves into the final cold-rolled sheet was proposed.

(Problems to be Solved by the Invention) However, even with the above method, in the case of a thin plate having a thickness of 0.27 mm or less, the variation in characteristic values is large and stable characteristics cannot necessarily be obtained.

The present invention aims to advantageously solve the above-mentioned problems, and to propose an advantageous manufacturing method for grain-oriented electrical steel sheets that can stabilize the properties even if they are thin.

(Means for Solving the Problems) That is, the present invention provides a grain-oriented electrical steel sheet material that has been cold-rolled to a final product thickness of 0.27 mm or less, is subjected to decarburization annealing, and then final annealing to produce a grain-oriented electrical steel sheet material. In manufacturing a steel plate, after cold rolling to the final product thickness, linear grooves with a depth that satisfies the following formula are locally introduced into the steel plate surface to produce a low iron loss grain-oriented electrical steel plate. It's a method.

Logd≧0.6 Ra-1-0,4 d: Groove depth (μm) Ra: Average surface roughness of final cold-rolled sheet (μm) Below, the elucidation process of this invention will be explained.

Now, the inventors have reconsidered a method for reducing iron loss by locally introducing grooves into a grain-oriented electrical steel sheet that has been cold-rolled to its final thickness, and as a result has found the following. In other words, for thin products with a final plate thickness of 0.27 mm or less, even if grooves with the same depth are locally introduced in many steel plates with different cold rolling conditions, the improvement in iron loss will vary depending on the steel plate, and It was discovered that even if the desired iron loss value was obtained with a steel plate, the improvement in iron loss was small with other steel plates, and the desired iron loss value could not be obtained when averaged over all steel plates.

As a result of investigating these causes, we came to the conclusion that the surface roughness of steel plates differs depending on the steel plate, and that this may have an effect on the iron loss improvement equation. Normally, the surface roughness of the final cold-rolled steel sheet varies depending on the roughness of the rolling rolls, the type and degree of deterioration of the rolling oil, the rolling speed, the diameter of the rolling rolls, etc., and the average surface roughness is smooth. In some cases, it is less than 0.1 μm, and in rough cases, it reaches several μm.

Therefore, the inventors next prepared five types of steel plates with various average surface roughnesses that had been cold rolled to a thickness of 0.23 mm.
The following experiment was conducted. The average surface roughness of the prepared steel plates was 0.07 μm, 0.18 μm, and
At 0.35 μm, 0.72 μm and 0.94 μm, linear grooves with a depth of 2 μm to about 40 μm were locally introduced into these steel plates. The grooves were formed by printing etching resist ink on the non-etched areas, performing electrolytic etching, and then removing the etching resist. The width of the linear grooves was approximately 150 μm, the direction thereof was perpendicular to the rolling direction, and the interval in the rolling direction was 4 mm.

Thereafter, these steel plates were subjected to decarburization annealing and then final finish annealing, and the resulting product plates were measured for iron loss W1□750 after strain relief annealing using an Epstein tester.

In addition, as a comparative material, a steel plate without grooves was also subjected to the above annealing and the iron loss was measured.

FIG. 1 shows the experimental results in terms of the relationship between the average surface roughness of the steel plate and the groove depth. In the figure, the ○ mark indicates that the iron loss W+715° has improved by 0.03 W/kg or more compared to the comparative material without grooves, while the × mark indicates that the iron loss has improved by 0.03 W/kg.
This is a case where it is less than g or a case where no improvement in characteristics is observed.

As is clear from the figure, the rougher the surface average roughness of the steel sheet, the deeper the grooves need to be formed, and the groove depth is d (μm),
-If the average surface roughness of the blade steel plate is Ra (μm), it has been newly discovered that in order to achieve stable iron loss improvement, it is necessary to satisfy the following relationship: be.

As mentioned above, the surface roughness of a cold rolled steel sheet inevitably varies depending on the rolling conditions, etc., but if grooves corresponding to the surface roughness are introduced according to the present invention, the effect of introducing the grooves will be stabilized. An excellent iron loss reduction effect can be obtained.

(Function) Now, in this invention, a steel plate cold-rolled to the final thickness by a known method is used. Although grooves are locally introduced into this steel plate, a process to change the surface roughness of the steel plate may be performed before or after introducing the grooves. For example, the surface of a steel plate with a rough average roughness may be made smooth by polishing or the like, or conversely may be made rough by pickling or the like. The point is that local grooves are introduced into the steel plate when decarburization annealing is performed, and the relationship between the depth of the grooves and the surface roughness of the steel plate satisfies the range of the lifting type.

However, if the groove is too deep, although the iron loss will be reduced, the excitation current will tend to increase, so the groove depth should be 70 μm.
It is preferable to set it to about the following.

Regarding the method of introducing grooves, methods that produce burrs such as markings cannot be adopted because the space factor will decrease. There are no particular restrictions on the method as long as it does not reduce the floor space ratio.
Electrolytic etching and chemical etching are suitable. It is desirable that the width of the groove is 300 μm or less, and the interval in the rolling direction is 1 square or more.

This is because if the thickness is less than 1 mm, it is difficult to obtain the desired effect of reducing iron loss. Further, the shape of the linear grooves may be not only straight, but also dotted or curved, but it is particularly advantageous that the direction thereof is perpendicular to the rolling direction. However, the same effect can be obtained within a range of 30° to the perpendicular direction. Note that by introducing grooves, the same iron loss reduction effect can be obtained on either one or both sides of the steel plate.

After the grooves are introduced, decarburization annealing is performed by a known method, followed by finish annealing. After this final annealing, a top coat is usually applied to produce the product.

Example 1 C: 0.07%, Si: 3.25%, Mn: 0.07%
, Se: 0.02° Al: 0.025 and N: 0.008%, with the remainder being substantially Fe, by hot rolling and annealing, and then cold rolling. The cold-rolled sheets had final thicknesses of 0.20 mm and 0.23 mm.

Next, linear grooves having a width of 150 .mu.m were introduced into this cold-rolled sheet in a direction perpendicular to the rolling direction at intervals of 4.5 mm in the rolling direction by electrolytic etching. Etching was performed by printing resist ink on the non-etched areas. The surface average roughness Ra of this cold-rolled sheet is 0.25 μm, and the groove depth is 3 μm.
There were two depths: 1 and 20 μm.

After removing the resist ink, decarburization annealing was performed in a wet hydrogen atmosphere, and then final finish annealing was performed at 1200°C.

An Epstein test piece was cut out from the product sheet thus obtained, and the iron loss after strain relief annealing at 800°C for 3 hours was measured.

The results are shown in Table 1 in comparison with those in which no grooves were introduced, and it can be seen that in any plate thickness, the iron loss characteristics obtained according to the present invention have been significantly improved.

Table Example 2 C: 0.04%, Si: 3.35%, Mn: 0.07%
, Se: 0.02% and Sb: 0.026%, with the remainder being essentially Fe. After hot rolling, a silicon steel slab was subjected to two intermediate annealing sessions at 975°C for 2 min. The material was cold rolled to a final thickness of 0.18-.

After polishing the steel plate to an average roughness of 0.08 μm, grooves were introduced in the same manner as in Example 1 except that the etching method was changed to chemical etching using nitric acid. However, the depths are 2 μm, 5 μm, and 15 μm.

Table 2 shows the results of investigating the magnetic properties of a product board obtained by performing the same treatment as in Example 1 after introducing the grooves.

In this case as well, the material obtained according to the present invention achieves a significant reduction in iron loss.

Condolence Table Figure 1 (Effects of the Invention) Thus, according to the present invention, it is possible to stably obtain excellent magnetic properties even for a thin grain-oriented electrical steel sheet with a thickness of 0.27 mm or less; The properties of grain-oriented electrical steel sheets do not deteriorate even when subjected to high-temperature heat treatment such as strain relief annealing, and therefore they are effective even when used as the core of either type or winding type transformers. It is possible to reduce iron loss and improve efficiency.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the average surface roughness of a steel plate and the groove depth on the iron loss improvement equation. Silver life average: Ra 1m

Claims (1)

[Claims] 1. In producing a grain-oriented electrical steel sheet by subjecting a grain-oriented electrical steel sheet material that has been cold rolled to a final product thickness of 0.27 mm or less, decarburizing annealing, and then final finish annealing. , A method for producing a low iron loss grain-oriented electrical steel sheet, which comprises locally introducing linear grooves with a depth satisfying the following formula into the surface of the steel sheet after cold rolling to the final product thickness. Logd≧0.6Ra+0.4 d: Groove depth (μm) Ra: Average surface roughness of final cold rolled sheet (μm)