JP2942074B2 - Manufacturing method of low iron loss grain-oriented electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an advantageous method for producing a low iron loss oriented magnetic steel sheet suitable for use in an iron core of a transformer or other electric equipment. Grain-oriented electrical steel sheets are mainly used as core materials for transformers, and are required to have good magnetic properties. In particular, it is important that energy loss, that is, iron loss, when used as an iron core is low.

[0002]

Therefore, in order to reduce iron loss, the crystal orientation must be highly aligned with the (110) [001] orientation, the Si content must be increased, thereby increasing the electrical resistance of the steel sheet, and impurities must be reduced. Various attempts have been made to reduce the thickness and to reduce the thickness. As a result, for steel sheets with a thickness of _{0.23 mm} or less, iron loss W _17/50 (magnetic flux density
1.7 T, 50 Hz) of 0.9 W / Kg or less has been produced. However, no further significant improvement in iron loss can be expected with metallurgical methods.

In recent years, various attempts have been made to artificially subdivide magnetic domains as a means for achieving a significant reduction in iron loss. Among them, a method currently being industrialized includes a method of irradiating a surface of a finish-annealed steel sheet with a laser as proposed and disclosed in a method for improving iron loss characteristics of grain-oriented electrical steel sheets of Japanese Patent Publication No. 57-2252. There is. However, although this method is effective in reducing iron loss,
There is a drawback that iron loss is deteriorated by strain relief annealing, and it is not used for wound iron cores that require strain relief annealing.

On the other hand, as a technology capable of performing strain relief annealing, a method of manufacturing a low iron loss unidirectional electrical steel sheet disclosed in Japanese Patent Publication No. Sho 62-54873 involves locally applying a finish-annealed steel sheet by laser or mechanical means. After removing the insulating coating, a linear groove is formed locally by a method such as pickling the part where the coating has been removed or mechanically directly marking the ground iron with a knife or the like, and then filling the groove. The method of applying a phosphoric acid-based tension-imparting coating to a steel sheet, and the method of producing a low iron loss unidirectional magnetic steel sheet disclosed in Japanese Patent Publication No.
A method has been proposed in which a groove having a depth of more than 5 μm is formed in a ground iron portion with a load of 90 to 220 Kg / mm ² and then heated at a temperature of 750 ° C. or more.

[0005] In each of these methods, a linear groove is introduced into the surface of a steel sheet which has been subjected to finish annealing. However, in the former method, the coating is always stably formed due to the difference in the thickness of the coating and the light absorption. Since it is difficult to remove, a stable groove cannot be formed, and in particular, in the case of direct mechanical scribing, there is a problem that burrs are generated around the groove, thereby lowering the space factor.
On the other hand, the latter method has a problem that it is difficult to adjust a load for obtaining a groove having a constant depth. In addition, when grooves are introduced into a steel sheet that has been subjected to finish annealing as in these methods, since the grooves are damaged by the introduction of the grooves, it is often necessary to re-apply the insulating film, thereby lowering the space factor and This leads to an unnecessary increase in cost.

[0006]

SUMMARY OF THE INVENTION The present inventor has studied various methods for providing a low iron loss material easily and stably without the above-mentioned drawbacks and with other one person. After the final cold rolling in the method for producing a low iron loss electromagnetic steel sheet disclosed in JP-A-4-88121, an etching resist was applied and baked while leaving a continuous or discontinuous linear non-applied area on the steel sheet surface. Thereafter, a method for reducing iron loss by forming a linear groove on the surface of the steel sheet by performing an etching process was proposed and disclosed. This method has made it possible to industrially produce low iron loss materials easily. However,
After that, a problem has arisen that the product characteristics obtained during the course of the production have variations.

Therefore, the cause of this variation has been investigated diligently.
As a result of the analysis, it was found that the groove shape was varied in the width direction of the plate, and that the variation was caused by a defective etching resist coating state due to a defective shape of the steel plate. As is well known, the final cold-rolled sheet is not necessarily flat in shape due to remaining distortion due to rolling. For this reason, when applying the etching resist to leave the linear non-applied area, the width is 100 to 200 μm.
In some cases, the area of the line-shaped non-applied portion of m was narrowed or completely filled in some places.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problem of the application of the etching resist, and to propose a method for producing a low iron loss grain-oriented electrical steel sheet having uniform product characteristics without variation. .

[0009]

In order to solve the above-mentioned problems, a tension was first applied to the steel sheet, and an attempt was made to improve the shape of the steel sheet by increasing the tension, but no great effect was obtained.
However, through subsequent experiments and studies, the present inventors have newly found that a method of applying an etching resist by winding a steel sheet around a roll surface has been achieved, and achieved the present invention.

That is, the gist of the present invention resides in that an etching resist is applied to the surface of a cold-rolled sheet for directional electromagnetic steel that has been cold-rolled to the final product sheet thickness, and then subjected to an etching treatment to apply the etching resist to the surface of the cold-rolled sheet. In a method for producing a grain-oriented electrical steel sheet in which a linear groove is formed, and thereafter the resist is removed, and then decarburizing annealing and then final finishing annealing, the cold-rolled sheet is wound around a roll surface. A method for producing a low iron loss grain-oriented electrical steel sheet, wherein an etching resist is applied while correcting the shape of a cold-rolled sheet (first invention),

In the first invention, the shape of the cold rolled sheet is corrected by
This is performed at a winding angle of 5 ° or more (second invention). In the first or second invention, an etching resist is applied while applying tension to the cold-rolled sheet (third invention).

[0012]

The present invention will be described in more detail below. First, the results of an experiment on which the present invention is based will be described.
A grain-oriented electrical steel sheet is generally manufactured by the steps described below. That is, the slab for grain-oriented electrical steel sheets is hot-rolled, and then, if necessary, hot-rolled sheet annealing is performed, and then the final product sheet thickness is obtained by one or two or more cold rolling steps including intermediate annealing. After charcoal annealing, final finish annealing is performed, and then a top coat is usually applied to obtain a product.

During the above-mentioned manufacturing process, an etching resist ink containing an alkyd resin as a main component is applied by gravure offset printing to the surface of the entire surface of the coil of the final cold-rolled sheet rolled to a sheet thickness of 0.23 mm by gravure offset printing. The width is 0.2 mm in the direction perpendicular to the rolling direction, and the distance between the rolling directions is 3
The coating was applied so as to remain in a continuous linear shape in mm, and then baked at a temperature of 200 ° C. for a time of 30 seconds.

In applying the etching resist, the cold rolled sheet was wound around the roll surface, and the winding angle θ around the roll surface shown in FIG. 1 was changed from 0 ° to 200 °. At this time, a tension of 1.5 kgf / mm ² was applied to the cold rolled sheet.

FIG. 1 is an explanatory view showing an example of winding a cold rolled sheet around a roll surface and applying an etching resist by a gravure offset printing machine, wherein 1 is a cold rolled sheet, 2 is a backup roll, and 3 is a gravure roll. 4 is a rubber transfer roll, 5 is a shimeshi roll, and 6 and 7 are doctor knives.

Observing the etching resist applied in this manner in detail, when the wrapping angle θ is 10 ° or more, the etching resist is applied almost uniformly over the entire width direction of the plate and the non-applied area is correctly formed. In contrast, when θ is smaller than 10 °, the application of the etching resist is uneven in the width direction of the plate, or the applied etching resist is crushed, and the width of the non-applied area is reduced. It was observed that the non-applied area was blacked out.

The steel sheet coated with the etching resist is electrolytically etched to form a linear groove having a width of 0.2 mm and a depth of 20 μm, and then immersed in an organic solvent to form the etching resist. Was removed. Here, the electrolytic etching uses a NaCl electrolytic bath and the current density is 1
The treatment was performed at 0 A / dm ² for 20 seconds. After the completion of the electrolytic etching, the width and depth of the formed groove were measured using a roughness meter at 10 places in the plate width direction and 20 places in the longitudinal direction of each coil.

The cold-rolled sheet subjected to such a groove forming treatment was subjected to decarburizing annealing followed by final finish annealing, and these finished annealed sheets were subjected to overcoating to obtain products.

From the product plate thus obtained, an Epstein test piece was cut out, subjected to strain relief annealing, and then measured for magnetic properties. As a result of these measurements, FIG. 2 shows the relationship between the winding angle θ of the cold rolled sheet around the roll surface at the time of applying the etching resist, the iron loss W _17/50, and the variation in the groove shape. Here, the iron loss W _17/50 is a measured value at a magnetic flux density of 1.7 T and a frequency of 50 Hz, and the variation in groove width and depth was calculated from 200 measurement points. FIG. 2 also shows the characteristics of the steel sheet in the portion not subjected to the groove forming process, which was obtained from the same coil.

FIG. 2 shows that the iron loss of the steel sheet subjected to the groove forming treatment is significantly reduced as compared with the steel sheet not subjected to the groove forming treatment. When the cold rolled sheet is wound around the roll surface at the time of applying the etching resist, the iron loss is further reduced as compared with the case where the cold rolled sheet is not wound around the roll surface (when the winding angle is 0 °). When the _temperature is not less than 0 °, a reduction of 0.03 W / Kg or more is obtained in the iron loss W _17/50 .

The groove shape of the steel plate obtained at this time is, as described above, when the etching resist is uniformly applied over the entire width direction of the plate and the uncoated portion is correctly left when the winding angle is 10 ° or more. , Grooves are formed almost uniformly over the entire width direction of the plate, and the groove width and depth vary little.If the winding angle is less than 10 °, the groove width becomes uneven or In some cases, it was confirmed that there were portions where the grooves had disappeared, and the frequency of occurrence thereof increased as the winding angle became smaller.

As described above, by applying the etching resist in a state where the cold rolled sheet is wound around the roll surface, it becomes possible to perform even coating on the final cold rolled sheet surface having a poor shape. It became clear that magnetic steel sheets with low iron loss can be manufactured more stably.

It is not clear why the iron loss is reduced by the groove forming process on the final cold-rolled sheet. However, it is not clear that the local groove has a favorable effect in the finish annealing atmosphere, and the magnetic domain refinement in the product. It is estimated that the effect was brought about.

Next, the limiting conditions and preferred conditions of the present invention will be specifically described. In the present invention, it is necessary to apply an etching resist to the surface of the cold rolled sheet while the final cold rolled sheet is wound around the roll surface.
It should be noted that the etching resist is applied while leaving a continuous or discontinuous linear non-applied portion region. By doing so, the shape of the steel plate at the time of applying the etching resist is corrected, so that the etching resist can be applied correctly and stably, and a good linear groove can be obtained after etching. It is important that the winding angle at the time of winding is 5 ° or more, preferably 10 ° or more, but it is more effective to apply tension to the cold rolled sheet at the same time. However, simply applying tension cannot sufficiently correct the shape of the cold rolled sheet, and cannot apply a stable etching resist.

There are various methods of applying the etching resist, such as gravure offset printing, gravure printing without using an offset roll, lithographic offset printing, and screen printing. However, continuous printing on the coil is easy, and roll wear is reduced. Gravure offset printing is most suitable because a small and stable printing surface can always be obtained.

The ink used as the etching resist is preferably an ink containing a resin of an alkyd type, an epoxy type, a polyethylene type or the like as a main component.

After the etching resist is applied, baking is performed to cure the resin. The baking is performed at a temperature sufficient to evaporate the solvent, water and the like contained in the ink, and is usually performed at a temperature of 100 ° C. or more. Will be

The etching performed after the application and baking of the etching resist may be either electrolytic etching or chemical etching. In the case of electrolytic etching, the current density is 1 to 100 A / in an electrolytic bath such as a NaCl aqueous solution or a KCl aqueous solution.
It is preferably carried out in the range of dm ^2. This is because if the current density is too low, a sufficient etching effect cannot be obtained, and if the current density is too high, the resist may be damaged during etching. FeCl ₃ , HNO ₃ ,
H ₂ SO ₄ , H ₃ PO _{4 and the like, and} a mixture thereof are suitably used.

In these etching methods,
In order to obtain an industrially stable effect, electrolytic etching in which the current density can be easily controlled is more suitable than chemical etching in which the etching resist is easily damaged.

As a method for removing the etching resist after the etching, an alkali or organic solvent is suitable.

The shape of the groove thus formed may be a discontinuous linear shape, but is preferably a continuous linear shape. This linear groove has a width of 5 to 300 μm, a depth of 100 μm or less,
Preferably, the thickness is 5 to 50 μm, and the groove interval is 3 to 30 mm. The direction of the linear groove is best in a direction perpendicular to the rolling direction, but substantially the same effect can be obtained as long as it is within 30 ° of the perpendicular direction.

Although the linear grooves are usually formed on only one side of the steel sheet, it goes without saying that the effect can be obtained even if they are formed on both sides.

Next, the production of a grain-oriented electrical steel sheet to which the present invention is applied will be described. In the present invention, the component composition of the material for grain-oriented electrical steel sheets is not particularly limited. For example, C: 0.01 to 0.08 wt%, Si: 2.0 to 4.0
wt%, and MnSe, MnS,
Compositions containing a small amount of one or more of AlN, BN and the like are advantageously suitable. In addition, in addition to the above, those containing Sb, Sn, Bi, etc. as the inhibitor component are also applicable to the present invention.

Usually, the steel slab prepared to the above-mentioned preferred composition is hot-rolled, and then, if necessary, hot-rolled sheet annealing, and then cold-rolled once or twice or more with intermediate annealing. To the final product thickness.

An etching resist is applied and baked on the surface of the cold-rolled sheet having the final product thickness by the method described above.
After the etching is sequentially performed, the etching resist is removed, decarburization annealing is performed, and an annealing separator is further applied to perform final finish annealing.

After the finish annealing, the annealing separating agent is removed, and a top coat is applied as required to obtain a product. The effect of the present invention is exerted regardless of the presence or absence of the top coat.

The steel sheet produced as described above exhibits a very low iron loss value stably, and the value is maintained even after strain relief annealing, so that it can be used stably as a material for a wound core. In addition, it goes without saying that it may be generally used for an iron core that does not require strain relief annealing.

[0038]

【Example】

Example 1 A hot-rolled plate of 3.2% silicon steel containing AlN and MnSe as inhibitors was subjected to two cold rollings with intermediate annealing.
After rolling to a thickness of 0.23 mm, an etching resist was applied to the surface of the cold-rolled sheet by gravure offset printing, and then subjected to electrolytic etching to form linear grooves. When applying the etching resist, apply a steel sheet by wrapping it around the roll surface, and apply a wrapping angle of 5 °, 10 °, 30 °, 90 °, 180 °.
°, and compared with the case of not winding around the roll surface. The etching resist ink used was an ink containing an epoxy resin as a main component, and the electrolytic etching was performed in a Nacl electrolytic bath at a current density of 10 A / dm ² and a time of 30 seconds. Groove formation by the above processing is made in a direction perpendicular to the rolling direction, groove width: about 0.2 mm, depth: about 20 μm, groove interval: 3
mm to form a continuous line.

After the etching treatment, the steel sheet was immersed in an alkaline solution to remove the etching resist, then decarburized and finally finished-annealed, and further overcoated.

An Epstein coupon was sampled from the product obtained in this manner, and after the strain relief annealing, the magnetic properties were measured. The results are shown in Table 1 together with the test pieces taken from the same coil and not subjected to the groove forming treatment.

[0041]

[Table 1]

Here, W _17/50 indicates an iron loss at _1.7 T and 50 Hz, and B ₈ indicates a magnetic flux density at a magnetizing force of 800 A / m.

From Table 1, it can be seen that, as compared with the comparative example having no linear groove,
The iron loss of the comparative example, which was not wound around the roll surface upon application of the etching resist, was significantly reduced, but the conforming example wound around the roll surface according to the present invention showed even lower iron loss.

Example 2 A hot-rolled plate of 3.3% silicon steel containing AlN, MnSe, and Sb as an inhibitor was rolled to a thickness of 0.18 mm by twice cold rolling with intermediate annealing, and the surface of the cold-rolled plate was After applying an etching resist by gravure offset printing, a linear groove was formed by performing electrolytic etching. When applying the etching resist, the cold rolled sheet is wound around the roll surface and applied, and the winding angle is 5 °, 10 °, 30 °,
Five conditions of 90 ° and 180 ° were set, and compared with the case where the roll was not wound around the roll surface. Also, at this time, 10K
A g / mm ² tension was applied. Application of etching resist,
Electrolytic etching, groove formation, processing after groove formation, and the like were performed in the same manner as in Example 1. Table 2 shows the magnetic properties of the product thus obtained.

[0045]

[Table 2] From Table 2, the iron loss of the comparative example which was not wound around the roll surface during the application of the etching resist was significantly reduced as compared with the comparative example having no linear groove, but was wound around the roll surface according to the present invention. Adapted examples show even lower iron losses.

[0046]

The present invention includes a step of applying an etching resist to the surface of a cold-rolled sheet for directional electromagnetic steel cold-rolled to a final product sheet thickness and then performing an etching treatment to form a linear groove. In the method for producing a low iron loss oriented magnetic steel sheet, a cold-rolled sheet is wound around a roll surface, and an etching resist is applied while correcting the shape of the cold-rolled sheet. It is possible to obtain industrially stable grain-oriented electrical steel sheets with lower iron loss than conventional steel sheets, and since such steel sheets have no deterioration in iron loss due to strain relief annealing, they can be used for both stacked iron cores and wound iron cores. It greatly contributes to efficiency improvement.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of winding a cold rolled sheet around a roll surface and printing an etching resist by a gravure offset printing machine.

2 is a graph showing the relationship between wrapping angle θ and iron loss W _17/50 on the roll surface of the cold-rolled sheet in the etching resist coating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cold rolled sheet 2 Backup roll 3 Gravure roll 4 Rubber transfer roll 5 Shimesi roll 6,7 Doctor knife

Claims (3)

(57) [Claims] 1. An etching resist is applied to the surface of a cold-rolled sheet for directional electromagnetic steel that has been cold-rolled to a final product sheet thickness, and then subjected to an etching treatment to form a linear groove on the surface of the cold-rolled sheet. Thereafter, the resist is removed, and thereafter, the method for producing a grain-oriented electrical steel sheet to be subjected to decarburization annealing and then final finish annealing, wherein the cold-rolled sheet is wound around a roll surface to correct the shape of the cold-rolled sheet A method for producing a low iron loss grain-oriented electrical steel sheet, comprising applying an etching resist underneath. 2. The method for producing a low iron loss electromagnetic steel sheet according to claim 1, wherein the shape of the cold-rolled sheet is corrected at a winding angle of 5 degrees or more. 3. The method according to claim 1, wherein the etching resist is applied while applying tension to the cold-rolled sheet.