JPH0328321A - Formation of insulating film of grain-oriented electrical steel sheet having excellent workability of rolled core - Google Patents

Abstract

PURPOSE:To obtain the subject steel sheet having good slipperiness by specifying the surface roughness of the steel sheet prior to application of an insulating film material in the process for producing the electrical steel sheet by subjecting a material made into a final sheet thickness to a decarburization annealing, applying of the annealing and separating agent and final finish annealing, then applying the insulating film material thereon. CONSTITUTION:After a silicon steel slab is hot rolled and annealed, the steel sheet is made into the final sheet thickness by one pass or >=2 passes including an intermediate annealing of cold rolling. This material is subjected to the decarburization annealing, then to the final finish annealing after the annealing and separating agent is applied thereon. The insulating film material is thereafter applied on this material and the material is subjected to a heat flattening, by which the product steel sheet is obtd. The steel sheet is subjected to a surface finishing after the rolling in the final pass of the cold rolling stage or before the annealing after the rolling or after the decarburization annealing. The surface roughness of the steel sheet is adjusted to 0.25 to 0.70mu Ra value and the ratio LRa/CRa of the surface roughness LRa in the rolling direction of the steel sheet end the surface roughness CRa in the direction orthogonal with the rolling direction is specified to >=0.7.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of forming an insulating film on a steel plate in the manufacturing process of grain-oriented electrical steel sheets, and in particular, the present invention relates to a method for forming an insulating film on a steel plate in the manufacturing process of grain-oriented electrical steel sheets. The present invention relates to an insulation coating form and method for grain-oriented electrical steel sheets that have excellent workability.

(Prior art) Grain-oriented electrical steel sheets are produced by hot rolling a silicon-like material containing, for example, 2 to 4% St, annealing it, and then cold rolling it once or twice or more with an intermediate annealing in between. Then, after decarburization annealing, an annealing separator containing MgO as the main component is applied, final annealing is performed to develop secondary recrystallized grains with Goss orientation, and S,N The final product is manufactured by removing impurities such as, shaping the glass film, applying a coating liquid for the insulation film, and performing a baking process to shape the insulation film.

The grain-oriented electrical steel sheets obtained in this way are mainly used as iron core materials for electrical equipment, transformers, etc., and are required to have high magnetic flux density and low iron loss values.

On the other hand, when a grain-oriented electrical steel sheet is used as the core of a transformer, the hoop of the grain-oriented electrical steel sheet is continuously unwound and cut into a predetermined length using a shearing machine, and then sequentially wound or folded using a core processing machine. They are stacked to make wound cores or stacked cores. In the case of a wound core, it is made into a transformer by undergoing compression, molding, strain relief annealing, and winding work called lacing.

In this core manufacturing process, for example, in the case of a wound core,
It is necessary that the winding and forming operations can be carried out smoothly, that the end face of the steel sheet and the lap portion after forming the steel sheet have an excellent shape without any unevenness, and that the surface of the steel sheet has good lubricity.

In addition, the fact that there is no seizure between the surface coatings of the steel sheets during strain relief annealing, and the lacing work can be performed smoothly, improves core processing efficiency and prevents the induction of distortion and deterioration of coating performance due to seizure. It is important because To solve these problems, since the properties of the insulation coating on the surface of grain-oriented electrical steel sheets have a large effect, we developed an insulation coating that does not cause seizure between the surface coatings of the steel sheet during strain relief annealing and allows smooth racing work. The development of such a material is strongly desired not only from the viewpoint of processability but also from the standpoint of improving the magnetic properties of transformers.

As a means to improve the workability of such transformer cores, improvements have been made to the coating agents used when forming the insulation film. JP-A No. 61-4773 discloses a coating agent in which a mixture of one or more of primary phosphate, ultrafine colloidal silica with a particle size of 81 or less, chromic acid, and chromate is used as a coating agent. A technique has been disclosed for improving the slipperiness of an insulating film formed on the surface of a steel plate by applying it to a steel plate (strip) after annealing and baking it.

In recent years, improvements in these insulating coatings have improved the core loss, magnetostriction, insulation properties, and skin III lubricity of grain-oriented electrical steel sheets, and some effects have been obtained.

However, manufacturers who use grain-oriented electrical steel sheets to manufacture transformers, etc., have automated and increased the speed of processing machines used to process iron cores, making it possible to process them even faster than using the improved insulation film coating agent mentioned above. There is a current demand for an insulating film that eliminates the above problems and has further improved magnetic properties.

(Problems to be Solved by the Invention) The present invention has been made for the purpose of providing a method for forming a temporary insulation film for a directional electromagnetic cavity, which has good slip properties and excellent workability of an iron core.

(Means for solving problems) The gist of the present invention is as follows.

(1) After hot rolling and annealing a silicon steel slab, the final plate thickness is obtained by cold rolling once or twice or more with intermediate annealing in between, and this material is decarburized annealed and coated with an annealing separator. rear,
In a method for producing grain-oriented electrical steel sheets in which final annealing is performed, then an insulating film agent is applied, and heat flattening is performed, the steel sheet (strip) is surface-treated to improve the surface roughness of the steel sheet before the insulating film agent is applied. The Ra value is 0.25
~0.1On, and the surface roughness Lla of the strip in the rolling direction and the surface roughness CIlm in the direction orthogonal to the rolling direction.
A method for forming an insulating film on a grain-oriented electrical steel sheet in which the surface film has good lubricity and the wound core has excellent workability, the ratio being Ll-/CR-≧0.7.

(2) Steel plate (strip) before application of insulation coating agent
Surface treatment is applied to improve the surface roughness of the steel plate from 0.25 to Ra value.
0.70tI1n, and the surface roughness LRm of the strip in the rolling direction and the surface roughness CI in the direction perpendicular to the rolling direction.
The ratio of lm is Ll+-/CR-≧0. The means to make it 7 is
The wound core has a surface film with good lubricity as described in item 1 above, which is applied by mechanical means such as rolling, shot peening, and polishing, chemical means such as pickling and plating, or optical means such as laser beam irradiation. A method for forming an insulating film on grain-oriented electrical steel sheets with excellent workability.

The present invention will be explained in detail below.

In order to achieve the above object, the present inventors have conducted various studies on methods of forming an insulating film on grain-oriented electrical steel sheets. the result,
The surface shape (surface roughness) of the steel plate after insulation coating or treatment is
It was found that this has a strong influence on the film lubricity of the product plate. Furthermore, the surface shape of this steel plate has an Ra value of 0.25 to 0.
R a in the range of 70 μm and in the rolling direction of the strip
{I! ! L M 11 and R in the direction perpendicular to the rolling direction
a {F! C,, the ratio of L, l. /C≧0.
It has been found that in the case of No. 70, there is a remarkable effect of improving lubricity, and the effect of improving the workability of the wound core is large.

Next, the present invention will be explained in more detail based on experimental data.

Directional electric wire ff with a plate thickness of 0.30 mm manufactured by a known method
A sample was cut out from the strip coil after final annealing of the FI plate, and strain relief annealing was performed at 850°C for 4 hours to remove the coil set. ° direction (4
5° direction) and in the direction perpendicular to the rolling direction (C direction).

This steel plate is lightly pickled to remove excess annealing separation agent on the surface, and after activation treatment, 50%
Aluminum phosphate 100 mI! ．． A solution consisting of 140 mff of 30% colloidal silica and 7 g of chromic acid anhydride was applied at a weight after baking of 3.5 g/bo, and baked at 830''C for 30 seconds.

Cut out samples from the final product board obtained in this way,
The sliding friction coefficient (F
F value) was measured. That is, the sample 2 is placed between the clamping plates i1, 1-2, a weight is applied with a weight 3, the force F' for pulling out the sample 2 is measured with a spring scale 4, and the sliding friction coefficient μ
was determined by μ(FF)=F'/F.

Furthermore, a steel ball with a constant load is slid on the insulation coating, and the resistance value that the steel ball receives is measured (Method B) to investigate the slipperiness of the steel plate surface and to check the state of flaws on the insulation coating surface. Examined. Further, the magnetic properties of the samples coated with the insulation coating treatment agent and baked in the same manner were measured after the baking process. The results are shown in Table 1.

As shown in Table 1, for those polished in the C direction and 45° direction, both the FF value by method A and the lubricity by method B were significantly improved. In contrast, those polished in the L direction have a large Ra value but a Lll-/C*- of 0.
69, and almost no improvement effect was observed. In addition, for Aim 4 (comparative example) in which no polishing was performed, Ra was small < L =
-/c m- was 0.89, but method A. B
The measurement results using the method were extremely poor.

Next, a method for forming an insulating film according to the present invention will be described.

In the invention described in claim 1 of the present invention, the surface treatment of the steel plate is performed at a stage before application of an insulating coating agent and baking, and R
a{i: 0. 2 5~0. 7 Qn, L*i
/CIlm≧0.70. In the invention set forth in claim 2, when shaping the insulating film by the method set forth in claim 1, the means for making the surface roughness of the steel sheet a predetermined value includes rolling with a roll having a predetermined roughness. Mechanical methods such as shot peening and polishing, chemical methods such as pickling and plating, and laser beam irradiation? At least one of these optical methods can be used.

Next, the reasons for limiting the conditions in the present invention will be explained.

In the present invention, the surface treatment of the steel plate is performed before applying the insulation coating agent and baking, and the Ra value is 20.25 to 0.
The first point is to satisfy 70/111, Lll-/CR-≧0.70. When the Ra value is less than 0.25n, Lll. Even if the condition of /C≧0.70 is satisfied, the FF value and lubricity are not improved, and the effect of improving the winding processability when an electrical steel sheet is used as a transformer core cannot be obtained. On the other hand, if the Ra value exceeds 0.70-, not only no further effect can be obtained, but also the space factor when the electromagnetic steel sheets are laminated is reduced, resulting in an adverse effect on magnetism.

FIG. 2 shows L■/Cc for each surface roughness of the final product.
The relationship between the value of and the FF value is shown.

Ra value is 0.25 or more and L*-/C+-≧0.70
The FF value stably improves in the region of , and the workability into iron cores is good.

The process of processing the surface of the steel plate to control the surface properties may be performed at any stage before the process of applying and baking the insulating film, and the surface of the steel plate may be controlled in one or more steps. Can be processed. The most stable way to control the surface properties of a steel sheet is through the process of processing the surface of the steel sheet between cold rolling and before insulation film formation. Therefore, it is best to process the surface of the steel plate between cold rolling and annealing before applying the separator. Means for processing the surface of the steel plate include mechanical methods such as rolling with rolls having a predetermined surface roughness, polishing, shot peening, etc., chemical methods such as pickling and plating, laser beam irradiation, etc. Any of the above optical methods may be used, and the pattern of the steel temporary surface treatment may be linear, dotted, broken line, etc., or may be a combination of these.

Next, the reason why the workability of the iron core is improved by the coating formed by the present invention will be described. One of the mechanisms for improving the lubricity of the surface of an electromagnetic steel sheet is that the surface of the steel sheet is smooth, and the other is that point contact slides more smoothly than surface contact.

Although the present inventors proposed the former method of improvement in the above-mentioned Japanese Unexamined Patent Publication No. 61-4773, it is believed that the effects of the present invention are due to the latter method.

L. ．． The effect is large in the region where /C≧0.70, and although the reason for this is not clear, the inventors assume that it is because the percentage of point contact increases.

FIG. 3 shows the surface roughness patterns of a product plate made of a cold-rolled plate surface-treated material (Whetstone Roll Ken Fj) according to the present invention and a comparative example (product made of a cold-rolled plate without surface treatment).

FIG. 4 shows a chart showing the lubricity according to method B corresponding to the product plates (one according to the present invention and a comparative example) in FIG. 3.

From FIGS. 3 and 4, it can be seen that the product according to the invention is L a
m = 0.411 μm, C*a = 0.394 pm,
L*-/C a- = 1.047'FF by A method
Value 0. 3 B, B method Nijoru lubricity is also extremely good. On the other hand, in the comparative example, L*a=O. I78 Jf
fi. ．． C*a=0.231/rffl, Lll
ll/C++a=0,77, and L++-/C*-
Although the values are within the range specified by the present invention, the Ra value is low, the FF value is as high as 0.81 compared to the one according to the present invention, and the lubricity is also significantly inferior.

(Example 1) C. in weight %. 0.075%, Si; 3.1
5%, Mn; 0.065%, S; 0.023%,
Acid soluble/IJ: 0.028%, the balance being Fe and unavoidable impurities, hot-rolled by a known method,
After annealing, it was cold rolled to a final plate thickness of 0.295 mm. Then, after decarburization annealing and application of annealing separator, 1200″CX20Hr
Final annealing was performed to form the glass film. Next, after removing excess annealing separator, 50% aluminum phosphate (
N(H!PO4) i) Apply a coating solution consisting of 50 Ill, 100 ml of 20% colloidal silica, and 5 g of chromic acid anhydride to a weight of 3.5 g/po after baking, and bake at 850"CX3 for 0 seconds. In this process, (A) the rolling roll in the final pass of the cold rolling process;
Surface processing was performed under the conditions shown in Table 2 (B) before decarburization annealing after rolling, and (C) after decarburization annealing. Samples were cut from the product coil thus obtained, and the lubricity of the film, workability of the wound core, etc. were adjusted. The results are shown in Table 2.

Table 2 As shown in Table 2, whether the surface treatment process is for cold-rolled plates or decarburized plates, the surface treatment conditions are Ra value of 0.25 or more, L
*-/C *-≧0. 7 improved the film lubricity, and as a result of this, the workability on the Tranco machine was greatly improved.

(Example 2) The same material as in Example 1 was used as a starting material and treated in the same manner as in Example 1 until final annealing. Next, this coil is processed on a continuous line (A) by a brush roll (B) by dot irradiation with a laser beam to give the surface shape as shown in Table 3, and then washed with water and lightly pickled. The MA edge coating was processed and baked in the same manner as in Example 1. The results are shown in Table 3.

(ω: Ra value; Ra value in the L direction 3: Support film? As shown in Table 3, the Ra value is Good results were obtained in terms of trancomachine winding processability in all cases with a diameter of 0.25 μm or more.

(Effects of the Invention) According to the present invention, it is possible to provide a grain-oriented electrical steel sheet that has good lubricity on the surface of the steel sheet and is excellent in workability of an iron core in manufacturing a transformer.

[Brief explanation of drawings]

Fig. 1 shows the method (A method) for measuring the lubricity (sliding coefficient FF value) of a film, and Fig. 2 shows L at each roughness (Ra) of the temporary surface of the product. Figures 3(a) and 3(b) are diagrams showing the relationship between /C■ and the FF value. Figures 3(a) and 3(b) are a product plate made of a surface-treated cold-rolled plate according to the present invention and a product plate of a comparative example made of a cold-rolled plate without surface treatment. FIGS. 4(a) and 4(b) are charts showing the lubricity according to method B corresponding to the product board in FIG. 3. cbC＞KatoU Risun~N \ 6 D also acjG included OsLL- Warm-111 always lmH guard 〒1 1 4th figure C (1”) (hoinvention) (b) −-→-〈riko L Shima two (comparative selection) Ri QiR Sagi ~ Ri C branch) [-Procedural amendment (voluntary) Heikai August 21, 1 year

Claims (2)

[Claims] (1) After hot rolling and annealing a silicon steel slab, the final plate thickness is obtained by cold rolling once or twice or more with intermediate annealing in between, and this material is decarburized annealed and coated with an annealing separator. rear,
In a method for producing grain-oriented electrical steel sheets in which final annealing is performed, then an insulating film agent is applied, and heat flattening is performed, the steel sheet (strip) is surface-treated to improve the surface roughness of the steel sheet before the insulating film agent is applied. The Ra value is 0.25
~0.70 μm, and the surface roughness L_R_a in the rolling direction of the strip and the surface roughness C in the direction perpendicular to the rolling direction.
A method for forming an insulating film on a grain-oriented electrical steel sheet in which the surface film has good lubricity and the workability of a wound core is excellent, characterized by setting the ratio of _R_a to L_R_a/C_R_a≧0.7. (2) Steel plate (strip) before application of insulation coating agent
Surface treatment is applied to improve the surface roughness of the steel plate from 0.25 to Ra value.
0.70 μm, and the surface roughness L_R_a in the rolling direction of the strip and the surface roughness C_ in the direction orthogonal to the rolling direction.
The means for adjusting the ratio of R_a to L_R_a/C_R_a≧0.7 is either mechanical means such as rolling, shot peening, or polishing, chemical means such as pickling or plating, or optical means such as laser beam irradiation. A method for forming an insulating film on a grain-oriented electrical steel sheet according to claim 1, wherein the surface film has good lubricity and excellent workability of the wound core.