JP2654861B2 - Method of forming insulation film on grain-oriented electrical steel sheet with excellent workability and heat resistance of iron core - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet, and in particular, has a good slip property and heat resistance of a steel sheet surface film, and is used for processing an iron core in transformer manufacturing. The present invention relates to a method for forming an insulating film on a grain-oriented electrical steel sheet, which has excellent heat resistance and improves the magnetic properties of a transformer product.

(Prior Art) A grain-oriented electrical steel sheet is formed by hot rolling a silicon steel slab containing, for example, 2 to 4% of Si, annealing, and then performing cold rolling once or twice or more with intermediate annealing. After the final sheet thickness, and then decarburizing annealing, apply an annealing separator mainly composed of MgO, apply finish annealing to develop secondary recrystallized grains having Goss orientation, and further impurities such as S, N Is removed and a glass film is formed, then a coating liquid for an insulating film is applied, and a baking treatment is performed to form an insulating film to produce a final product.

Grain-oriented electrical steel sheets are mainly used as iron core materials for electrical equipment, transformers, and the like, and are required to have high magnetic flux density and low iron loss.

On the other hand, when the grain-oriented electrical steel sheet is used as a transformer core, the hoop of the grain-oriented electrical steel sheet is cut to a predetermined length by a shearing machine while being continuously unwound, and then sequentially wound by a core processing machine. It is assumed to be a wound iron core or a stacked iron core. In the case of a wound core, it is formed into a transformer by performing winding work called racing through compression molding and strain relief annealing.

In the iron core manufacturing process, if the core is cold, winding and forming work can be performed smoothly, and irregularities will be created on the end face and lap of the formed steel sheet. It needs to be good.

In addition, it is important that the lacing work can be performed smoothly without seizure between the surface coatings of the steel sheet during the strain relief annealing, from the viewpoint of improving the core processing efficiency or preventing the induction of distortion due to seizure and the deterioration of the coating performance. is there. Since the nature of the insulating film on the surface of the grain-oriented electrical steel sheet has a significant effect on these problems, we have developed an insulating film that does not seize between the surface films of the steel sheet during strain relief annealing and enables smooth lacing work. Is strongly desired from the viewpoint of workability and from the viewpoint of improving the magnetic characteristics of the transformer.

As means for improving the workability of the iron core of the transformer, a coating agent for forming an insulating film has been improved. When cooled, JP-A-61-4773 discloses that as a coating agent, a first phosphate is mixed with one or two or more of ultrafine colloidal silica having a particle diameter of 8 nm or less, chromate, and chromate. A technique for improving the slip property of an insulating film formed on the surface of a steel sheet by applying it to a steel sheet after finish annealing and performing baking treatment is disclosed.

In recent years, these lubrication properties have been improved along with iron loss, magnetostriction, and insulating properties of grain-oriented electrical steel sheets by improving these insulating films, and a certain effect has been obtained.

However, manufacturers that manufacture transformers and the like using grain-oriented electrical steel sheets, etc., have advanced the automation and speeding of processing and molding machines when processing into iron cores. There is a need to eliminate the above troubles and to provide an insulating film with further improved magnetic properties.

(Problems to be Solved by the Invention) The present invention forms an insulating film of a grain-oriented electrical steel sheet which has good slip properties and heat resistance during strain relief annealing of the grain-oriented electrical steel sheet and has excellent core workability. The purpose is to do.

(Means for Solving the Problems) The gist of the present invention is that a silicon steel slab is hot-rolled and annealed, and then cold-rolled once or twice or more with intermediate annealing to obtain a final sheet thickness. In the method for producing a grain-oriented electrical steel sheet, the material is decarburized and annealed and then subjected to a final finish annealing after being applied with an annealing separator, followed by applying an insulating film forming coating agent and performing a baking treatment followed by heat flattening.
Colloidal solution consisting of colloidal silica with a particle size of 50 nm or less
100 parts by weight (as SiO _2), Al, Mg, Ca, and one or more of 130 to 250 parts by weight of the phosphate of Zn, chromic acid anhydride, chromates, dichromate 1 Seeds or two or more
10 to 40 parts by weight, Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, M
oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates of elements selected from the group consisting of n, Mo, Si, Ti, W, Bi, Sr, V; A coating material for forming an insulating film formed by adding 0.5 to 25 parts by weight of one or more of non-colloidal solids having a particle size of more than 100 to 2000 nm as sulfates, nitrates or chlorides And a method of forming an insulating film on a grain-oriented electrical steel sheet having excellent workability and heat resistance of an iron core, which is characterized by performing a baking treatment.

 Hereinafter, the present invention will be described in detail.

The present inventors have conducted various studies on the formation of an insulating film on a grain-oriented electrical steel sheet in order to solve the above problems. As a result, during the application of the coating agent for the insulating film, in the baking process, the particle diameter is more than 100 to 2000 nm as a part of the composition in the coating agent for the insulating film composed of a mixture of colloidal deer, phosphate and chromium processed product. By adding and blending a non-colloidal substance, the lubricating property (slipperiness) of the insulating film formed by the baking treatment is remarkably improved, and the baking phenomenon of the film generally called sticking in strain relief annealing is greatly improved. And improved iron loss.

Hereinafter, the present invention will be described in more detail based on experimental data.

A sample was cut out from the strip coil after the finish annealing of the grain-oriented electrical steel sheet manufactured by a known method, and the strain relief annealing was performed at 850 ° C. for 4 hours, and after removing the coil set, 80% with 2% H ₂ SO ₄ . A sample that had been subjected to light pickling at 10 ° C. × 10 seconds was used as a sample. As shown in Table 1,
Was added blended powder of SiH ₂ having a particle size of 5～2000Nm, well stirred insulating film-forming coating agent after baking 4.5g
/ m ² and baked at 850 ° C. for 30 seconds in an N ₂ atmosphere. However, the specific gravity of 20% colloidal silica is 1.10 g / cc, and the specific gravity of 50% Al phosphate is 1.45 g / cc.

A sample was cut out from the obtained product plate, and the coefficient of sliding friction (FF value) of the insulating film was measured by the method (method A) shown in FIG. The measuring method is as follows. The sample 2 is placed between the sandwiching plates 1-1 and 1-2, a load N is applied by the weight 3 and the pulling-out force of the sample 2 is measured by a spring meter 4, and the sliding friction coefficient μ is calculated as μ (FF) =
It was determined from A / N.

In addition, the steel ball to which a constant load is applied is slid agitated on the insulating film, and the resistance value received by the steel ball from the insulating film is continuously taken out from the strain gauge (Method B) to lubricate the film surface. The properties were measured and evaluated. Separately, a 3 cm x 4 cm plate was cut out, laminated, tied under a clamping pressure of 80 kg / cm ² , and subjected to a strain relief annealing at 850 ° C for 4 hours in a N ₂ atmosphere. The peeling load of the steel sheet was measured by the separation method shown in FIG. The results are shown in Table 1.

As shown in Table 1, as compared with the conventional insulating coating agent composed of only colloidal silica having a particle size of 6 nm,
A coating material for forming an insulating film of the present invention containing 2 parts by weight of a non-colloidal solid powdery oxide having a particle size of more than 0 to 2000 nm is applied and baked. The remarkable improvement was observed in any of the sticking resistances.

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

The coating material for forming an insulating film according to the present invention comprises one or two types of phosphates of Al, Mg, Ca, Zn per 100 parts by weight (as SiO ₂ ) of a colloidal solution composed of colloidal silica having a particle size of 50 nm or less. 130 to 250 parts by weight of the above, 10 to 40 parts by weight of one or more of chromic anhydride, chromate and dichromate, Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si,
Ti, W, Bi, Sr, V oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, sulfates, nitrates or chlorides with a particle size of 100 One to two or more non-colloidal solids of ultra-2000 nm is added in an amount of 0.5 to 25 parts by weight. The coating material for forming an insulating film is applied to a grain-oriented electrical steel sheet and baked. To process.

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

In the present invention, as a coating agent for forming an insulating film,
With respect to 100 parts by weight of a fine-particle colloidal silica solution having a particle size of 50 nm or less, a non-colloidal solid having a particle diameter of more than 100 to 2000 nm is added and blended in an amount of 0.5 to 25 parts by weight in terms of solid content, and Al, Mg, One or more of the phosphates of Ca, Zn
250 parts by weight, 10 to 40 parts by weight of one or more of chromic anhydride, chromate and dichromate are used. At that time, it is important that the non-colloidal solid be added in an amount determined by the particle diameter and dispersed, or if the particle diameter is small, be appropriately aggregated.

A non-colloidal solid having a particle diameter of more than 100 to 2000 nm is added to and mixed with 100 parts by weight of a colloidal silica solution of fine particles of 50 nm or less in a range of 0.5 to 25 parts by weight of solid content. And has the effect of significantly improving the slip properties of the insulating film. It is important that the colloidal silica as the base fine particle has a particle size of 50 nm or less.If the particle size exceeds 50 nm, the effect of improving the iron loss and magnetostriction by the insulating film is reduced, or the film becomes opaque and the appearance becomes poor. In addition to inducing problems such as damage, the slipperiness of the coating also deteriorates due to the coarse particle diameter.

The particle size of the coarse non-colloidal solid compounded with the fine particle colloidal silica is more than 100 to 2000 nm. 1
By uniformly dispersing in the range of more than 00 to 2000 nm,
Improves slipperiness by providing irregularities on the surface after baking. If the particle diameter is not more than 100 nm, the effect of improving the slip property is small. On the other hand, if the particle diameter is more than 2,000 nm, although the slip property and heat resistance are present, the space factor is lowered when the products are laminated, which is not preferable.

Next, the blending of the colloidal silica and the phosphate is carried out by adding one or more of the phosphates of Al, Mg, Ca and Zn to 100 parts by weight (as SiO ₂ ) of the colloidal solution composed of the colloidal silica. ~ 250 parts by weight are used. When the content of these phosphates is less than 130 parts by weight, the binder effect is weak, cracks are generated in the insulating film, and the film tension is reduced. On the other hand, if it exceeds 250 parts by weight, the appearance of the film deteriorates and the heat resistance also deteriorates.
As the phosphate, a commercially available 50% solution may be used.

Since calcium phosphate has low solubility and a 50% solution cannot be obtained,
It is calculated to be balanced to a 50% solution.

From the viewpoint of improving the slip property of the base film, the most preferred combination of phosphates is Al-Mg-Ca, Al-Ca, Mg-Ca.
It is.

One or more of chromic anhydride, chromate and dichromate are blended according to the amount of phosphate. Phosphate
If the amount is less than 10 parts by weight with respect to 130 to 250 parts by weight, the amount required for stabilizing the free phosphoric acid in the film component by a reaction such as generation of CrPO ₄ is not sufficient, which causes stickiness.
On the other hand, if it exceeds 40 parts by weight, the amount of free chromic acid becomes excessive, and in this case, stickiness also occurs.

Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti, W, B
i, Sr, V oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, sulfates, nitrates or chlorides having a particle size of more than 100 to 2000 nm A colloidal solid is added. The solid is to form fine irregularities on the film surface, to enhance the slipperiness,
To obtain this effect, the particle diameter needs to be more than 100 nm. On the other hand, if the particle diameter increases, the space factor of the film decreases.

Further, if the amount of the non-colloidal solid is small, the effect of improving the sliding property cannot be obtained, so that the colloidal silica
0.5 parts by weight is added to 100 parts by weight. On the other hand, if the amount increases, the space factor of the film decreases, so the content is set to 25 parts by weight or less.

The reason why the insulating film produced according to the present invention is excellent in slipperiness and heat resistance is considered to be that unevenness is formed on the surface of the steel sheet by using a non-colloidal solid aggregate or a single substance.

Fig. 3 shows the composition of the coating agent for forming the insulating film (see Table 1).
And the slip property of the steel sheet surface. Sample No. 1 which did not satisfy the composition conditions of the present invention, to which the coating material for forming an insulating film was applied, failed in the slip test after several tests as shown in FIG. 3 (a). In the coating for forming an insulating film of Sample No. 3 using non-colloidal silica powder of 50 nm as an additive, the resistance gradually increased as shown in FIG. Was. 50 as coarse particles
As shown in FIG. 3 (c), the resistance value of the coating material for forming an insulating film of sample No. 5 using non-colloidal silica powder of 0 nm showed a low value without a change over time as shown in FIG. Has sliding properties.

 Next, examples will be described.

(Example) C: 0.081%, Si: 3.24%, Mn: 0.072%, S: 0.025% by weight
%, Sol. Al: 0.027%, the balance being silicon steel slab consisting of iron and unavoidable impurities was hot-rolled by a known method, cooled after annealing, and finished to a final sheet thickness of 0.220 mm. Then, decarburized annealing and MgO
Was applied, and finish annealing was performed at 1200 ° C. for 20 hours to form a glass film. Next, the excess annealing separating agent was removed by washing with water, and after washing with light acid, an applying agent for forming an insulating film having a composition shown in Table 2 was applied.
However, the specific gravity of 20% colloidal silica is 1.10 g / cc, and the specific gravity of phosphate (50%) is 1.45 g / cc. When applying this,
The coating agent was applied to a steel sheet so that the weight after baking became 4.5 g / m ² , and then baking treatment was performed at 850 ° C. × 25 seconds in an N ₂ atmosphere.

A sample was cut out from the obtained steel sheet, and the FF value, the slip value, the presence or absence of flaws, and the sticking resistance were examined. The results are shown in Table 3.

(Effects of the Invention) According to the present invention, a rectangular magnetic steel sheet having good slipperiness and heat resistance of a steel sheet, excellent workability of an iron core in transformer production, and good magnetic properties of a transformer product Can be obtained.

[Brief description of the drawings]

FIG. 1 shows a means (A) for measuring the sliding friction coefficient of an insulating film.
FIGS. 2 (a) and 2 (b) are diagrams showing a method of investigating the sticking property when performing strain relief annealing after processing an electromagnetic steel sheet into an iron core, and FIG. FIG. 3B is a diagram showing the state of lamination of the sample in the strain relief annealing when investigating the sticking property, FIG. 3B is a diagram showing a state when the seizure state between the layers is measured after the strain relief annealing is completed, and FIGS.
(C) is a diagram showing the composition of a coating agent for forming an insulating film and the lubricity of the product.

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Claims (1)

(57) [Claims] (1) After hot rolling and annealing a silicon steel slab,
Cold rolling is performed twice or more with intermediate or intermediate annealing to obtain the final sheet thickness. This material is decarburized and annealed, coated with an annealing separator, subjected to final finish annealing, and then coated with an insulating film forming coating agent. In the method for producing grain-oriented electrical steel sheet subjected to heat blanching after baking treatment, 100 parts by weight (as SiO ₂ ) of a colloidal solution composed of colloidal silica having a particle size of 50 nm or less, Al, Mg, Ca, Zn 130 to 250 parts by weight of one or more of phosphates and chromic anhydride, chromate,
10 to 40 parts by weight of one or more dichromates,
Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti, W, Bi,
Oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, sulfates, nitrates or chlorides of the elements selected from the group consisting of Sr, V
One or two of non-colloidal solids of more than 100 to 2000 nm
A coating material for forming an insulating film formed by adding 0.5 to 25 parts by weight of a seed or more, and applying a baking treatment, forming an insulating film on a grain-oriented electrical steel sheet having excellent workability and heat resistance of an iron core. Method.