JPH01116085A - Formation of insulating coat having superior suitability to blanking and welding on electrical steel sheet - Google Patents

Abstract

PURPOSE:To form an insulating coat having superior suitability to blanking and welding on the surface of an electrical steel sheet by applying a mixed treating soln. consisting of a phosphate-contg. treating soln. and org. resin and having a specified viscosity to the surface of the steel sheet by a natural reverse system and by baking the applied soln. to provide a specified roughness. CONSTITUTION:Org. resin is added to a treating soln. contg. one or more kinds of salts selected among the phosphates, chromates and dichromates of Zn, Al, Ca, etc., by >=about 5pts.wt. per 100pts.wt. of the salts and the viscosity of the soln. is regulated to 300-500cps with CMC, etc. Water soluble or emulsion type acrylic resin may be used as the org. resin. The resulting mixed treating soln. is applied to the surface of an electrical steel sheet by a natural reverse system wit a gravure roll as a pickup roll, dried and baked to form an insulating coat having 0.5-1.5mum surface roughness Ra on the surface of the steel sheet. The insulating coat has satisfactory suitability to blanking and welding.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for forming an insulating film with excellent punchability, weldability and electrical insulation properties on the surface of an electrical steel sheet.

<Prior Art> Iron cores for motors and transformers for home appliances are assembled by continuously punching electromagnetic steel plates into a predetermined shape, then stacking a large number of them and TIG welding the sides.

Therefore, electromagnetic control plates are required to have excellent punchability and weldability at the same time.

It is known that the punchability and weldability of electromagnetic steel sheets depend not only on the material of the steel sheet itself, but also on the composition and thickness of the insulating film treated on its surface.

The insulating films currently in practical use can be roughly classified based on their composition: (A) Inorganic (phosphate, chromate, dichromate, etc.) (B) Semi-organic (chromate, resin, etc.) etc.) and (C) organic type (resin, festival, etc.).

By the way, the electrical steel sheet coated with an inorganic (A) film is TI.
G welding There is no welding lobe hole formation, and the weldability is excellent, but the number of punches per polishing of the punching die is about 100,000, and the punching performance is poor.

On the other hand, in the case of semi-organic type (B) and organic type (C) coatings, excellent punching performance of about 1.5 million times can be obtained, but on the other hand, gas is generated due to decomposition of resin etc. during welding, and blowholes occur. This occurs easily and the weldability is poor.

In order to improve the weldability of such semi-organic and organic coatings, a technical concept for imparting roughness to the coating surface was proposed in Japanese Patent Publication No. 49-19078.

The roughness can be achieved by applying an organic film uniformly and treating the uncured film during baking with a roll that has roughness, or by forming a vertically grooved film on the surface of the steel plate with a grooved coating roll, and then baking. A method is disclosed in which horizontal grooves are formed in the uncured film inside using a grooved steel roll, and a method in which organic particles of approximately 2 μm or more are added to the treatment solution and applied and baked.

Among these methods, the most industrially effective method is to add the last organic particles to the treatment solution and apply and bake. ) had a problem.

If there is a problem with the dispersion of these organic particles in the processing solution, an insulating film that is stable for a long time and has a specified surface roughness will not be formed, and the organic particles will aggregate into secondary particles. The adhesion (adhesion) to the steel plate becomes poor and there is an insulating film! When slitting a magnetic steel sheet, it has the disadvantage that organic particles come off due to the tightening of the steel sheet with a mechanical batt or the like.

A technique for solving this drawback and improving the dispersibility of organic particles and their adhesion to steel sheets was proposed in Japanese Patent Publication No. 55-21111.

This is a method in which organic resin particles are added to the emulsion resin solution in advance, uniformly dispersed, and then mixed into the coating solution. However, since the organic resin particles are not yet completely dispersed in the processing solution, An improvement method is proposed in Japanese Patent Publication No. 183479/1983.

This method is characterized by surface treating the organic resin particles with a dispersibility improver before adding them to the emulsion resin solution, but the dispersibility of the organic resin in the treatment liquid is still insufficient.

If this dispersibility is poor, as mentioned above, the organic resin particles
Adhesion of organic particles to the steel plate (adhesion)
deteriorate. Furthermore, the organic resin particles and the treatment liquid are different, so even if they are sufficiently dispersed in the treatment liquid, constant stirring is required to prevent floating or sedimentation during application to a steel plate.

Furthermore, when a treatment liquid mixed with organic resin particles is transported through a pipe, the floating or settling of the organic resin particles causes the pipe to become clogged, which poses a major operational problem.

<Problems to be Solved by the Invention> The present invention provides a method for forming an insulating film on a semi-organic or organic electromagnetic steel sheet that improves the dispersibility of an organic resin and has excellent punchability and weldability. It is.

<Means for solving the problem> The present invention provides a method of applying a viscosity of 300 to 5 on the surface of an electrical steel sheet.
A treatment solution that is a mixture of one or more phosphate-based, chromate-based, and dichromate-based processing solutions and an organic resin adjusted to 0.000 cp, a water-soluble resin, or an emulsion resin. The film treatment solution was applied using a natural reverse method using a gravure roll as a pick-up roll, and then baking was performed to reduce the surface roughness to 0 in Ra.
．． This is a method for forming an insulating film on an electrical steel sheet with excellent punchability and weldability, characterized by having a thickness of 5 to 1.5 μm.

<Function> The coating treatment liquid used in the present invention is a treatment liquid that is a mixture of one or more phosphate-based, chromate-based, or dichromate-based treatment liquids and an organic resin, or a water-soluble resin, Alternatively, it is a treatment liquid for emulsion resin.

Phosphate, chromate, or dichromate salts include phosphates, chromates, and dichromates of zinc, aluminum, calcium, and magnesium; These include oxides, hydroxides, and carbonates dissolved in phosphoric acid and chromic anhydride, and may also be a mixture of two or more of these. One or more of aqueous or emulsion type acrylic resins and their copolymers, vinyl acetate resins and their copolymers, butadiene-styrene copolymers, alkyd resins, epoxy resins, or modified products thereof are used.

As a reducing agent, polyhydric alcohol such as ethylene glycol or glycerin is added, and colloidal silica,
Heat resistance improvers such as colloidal alumina and boric acid may be added.

The amount of these components to be added is preferably 5 parts by weight or more for the aliphatic resin component per 100,111 parts of inorganic components such as phosphates and chromates; sufficient punchability is obtained when it is less than 5 parts by weight. do not have.

Next, it is appropriate to use a reducing agent such as ethylene glycol in an amount of 0.5 to 30 parts by weight, and a heat resistance improver such as boric acid in an amount of 0.5 to 30 parts by weight.

The viscosity of the above-mentioned water-soluble mixture is 1.2 to 3 cp, and even if the natural reverse method using a gravure roll as a pick-up roll is adopted as the application method, no coating will be applied to the steel plate surface.
It is applied uniformly, and the surface roughness Ra is at most about 0.15 μm, and the improvement in weldability, which is the objective of the present invention, is not observed.

To improve weldability, the surface roughness Ra must be between 0.5 and 1.5 μm. If it is less than 0.5 Br, weldability will be poor, and if it is more than 1.5 μm, the film will peel off due to contact with the tension pad during slitting. In order to increase the zero surface roughness Ra to 0.5 μm or more, it is necessary to increase the viscosity of the treatment liquid.

To increase this viscosity, carboxymethyl cellulose or hydroxyethyl cellulose can be added.
This blending amount is 1 to 3 parts per 100 parts of the above inorganic component.
0 parts is good; less than 1 part will not thicken and harden, and more than 30 parts (this is because the adhesion of the film will deteriorate if it is added.) By adding this thickener, the viscosity of the processing liquid can be increased from 300 to 300 parts.
Adjust to 5000cp. If the viscosity is less than 300 cp, it is difficult to secure the desired surface roughness RaO, 5, gm. Further, when the pressure is 5000 cp or more, the natural reverse coating method has poor workability and is not economical.

On the other hand, as the water-soluble organic resin for which the dispersion film is used as a treatment liquid, one or more of epoxy ester, polyester, melamine, polyethylene, polyacrylic, alkyd, etc. can be suitably used, and as the emulsion resin,
One or more of acrylic resins and coelectric compounds thereof, vinyl acetate and coelectric compounds thereof, butadiene-styrene copolymer alkyds, epoxies, or modified products thereof can be suitably used. These water-soluble organic resins and emulditene resins have a viscosity of 300 to 500 using thickeners and surfactants.
Use one adjusted to 0 cp.

On the other hand, the coating method is a natural reverse roll method using a gravure roll as a pickup roll.

As for the gravure roll, the shape of the gravure may be pyramid-shaped, lattice-shaped, oblique line-shaped, etc., and the number of lines and depth of these are selected depending on the concentration and viscosity of the processing liquid.

Natural all is performed using a gravure roll and a rubber roll, and the amount of coating is limited by the shape and size of the gravure roll. Approximately half of the processing liquid contained in the gravure recesses is transferred onto the rubber roll in a dotted manner. In order to use the natural reverse cooling method, the rubber roll, that is, the applicator roll, may be rotated in the opposite direction to the advancing direction of the steel plate to transfer dots of the treatment liquid onto the surface of the steel plate.

By performing normal drying and baking in this state, an insulating film having an Ra of 0.5 to 1.5 μm can be obtained on the surface of the steel plate.

<Example> Example 1 The treatment liquid A (viscosity 320cρ) described below was picked up on the surface of an electromagnetic control plate (Sf j 0.35%, plate thickness 0.5mm, plate width 1G25am, surface roughness RaO, 18μm). Grid type gravure roll (I35 mesh, number of lines 3)
5, depth of 0.22 m-) using the natural reverse method and baked at 500°C for 60 seconds. The area weight of the obtained film was 6.5 g/rd, and the surface roughness Ra of the film was 0.62 mm.

When steel plates with this film were laminated and TIG welded,
Even at a current of 120 A and a welding speed of 100 cm/min, there were no blowholes and a beautiful bead was obtained. When the material was punched with a 20-l steel die (clearance 6%), the burr height was 50 μm. To date, he has hit the ball 1.8 million times.

Comparative Example 1 As a comparative material, treatment liquid A was applied to a steel plate of the same material type as in Example 1 using a natural reverse method using a flat roll as a pick-up roll, and baked at 500° C. for 60 seconds. The area weight of the obtained film was 6.2 g/ld, and the surface roughness Ra of the film was 0.211° C.m.

When the steel plate having this film was punched under the same conditions as above, it was punched 2.1 million times until the burr height was 50 μm. However, when TIG welding was performed under the same conditions as in Example 1, many blowholes were generated throughout the bead.

Comparative Example 2 Further, as a comparison material, processing liquid B (viscosity 1.8 cp) was used in the same manner as in Example 1 using a lattice type gravure roll (I35 mesh, number of lines 35, depth 0.22 ■) as a pick-up roll and a natural reverse method. 6 at 500℃.
Baked for 0 seconds. The area weight of the obtained film was 6.6g/M
The surface roughness Ra of the film was 0.24 μm.

When steel plates having this coating were laminated and TIG welded, no blowholes were observed at a welding speed of 20C11/min at a current of 120A, but at higher welding speeds, blowholes occurred.

[Processing liquid A]

・30% magnesium dichromate solution 130 parts (inorganic component 41 parts) ・Acrylic-vinyl acetate resin emulsion (resin solid content 50%) 30 parts ・Ethylene glycol 10 parts ・Carboxyl methyl cellulose 10 parts [Treatment liquid B] Treatment [A] Table 1 shows the properties of other films excluding the carboxymethylcellulose (conventional chromate-organic resin treatment solution).

Example 2 Electromagnetic steel plate (St: 3.1%, plate thickness 0.5m+e, plate width 9
401, surface roughness Ra O, 23 μm), treatment liquid C (viscosity 1800 cp) was applied to a pyramid-shaped gravure roll (#32 mesh, number of lines 32) using a pickup roll.
, depth 0.26m5+) using the natural reverse method and baked at 450°C for 60 seconds. The area weight of the obtained film was 7.2 g/n (and the surface roughness Ra of the film was 0.76 μm).

When steel plates with this film were laminated and TIG welded,
Even at a current of 12 OA and a welding speed of 120 CI/min, a beautiful bead was obtained with no blowholes.

The punching performance of this material (20 - Kasumi φ steel die, clearance 6%) is 7 in the number of punches up to a burr height of 50μ.
It was 2% of the time.

Comparative Example 3 As a comparative material, treatment liquid D (
When a film with a viscosity of 160 cp) was applied under the same conditions as in Example 2, the area weight of the obtained film was 6.8 g/I,
The surface roughness Ra was 0.38 μm.

When this material was welded at 710°C, the welding speed without blowholes was 30C11/min, and the punching performance with a 205mφ steel die (number of punches up to a burr height of 50m) was 650,000 times. there were.

Comparative Example 4 As a comparative material, treatment liquid E (
When a film with a viscosity of 8200 cp) was applied under the same conditions as in Example 2, the coating weight of the obtained film was 6.3 g/po, and the surface roughness Ra was 0.81 μm.

When this material is TIG welded, the welding speed without blowholes is 120 cm/min, and the punching performance (number of punches up to a burr height of 50 μm) with a 20 φ steel die is 70%. Good results were obtained.

However, during the coating operation, the processing liquid adhered to the periphery of the roll, and it took a long time to clean the roll, resulting in very poor workability.

[Processing liquid C]

Water-soluble alkyd/melamine resin (mixing ratio 70:30) (non-volatile content 50%)
Table 1 (ml) JIS Method 2 (Umbrella 2) Diameter of the film when bent (4) After 7 hours of salt spray test (shrine) TIG welding, pressure 100 kg/ca 120 A
Maximum welding speed at which no plow holes occur (Shinkako φ steel die, number of punches up to a burr height of μm with a clearance of 6% (s6)) Time required to clean the application roll [Treatment liquid D] Water-dispersed emulsion resin Acrylic-vinyl acetate type (mixing ratio 80 j 20) (non-volatile content 50%)
[Treatment liquid E] Water-soluble epoxy/melamine resin (mixing ratio 70:30) (non-volatile content 50%) Other film characteristics are shown in Table 1.

<Effects of the Invention> Thus, according to the present invention, when forming an insulating film on the surface of an electrical steel sheet, a pick-up roll using a gravure roll for the coating method is used after dispersion treatment with a viscosity of 300 to 5000 cp. By adopting the natural reverse method using
It was possible to obtain an insulating film that simultaneously satisfies punchability and weldability, which were conventionally considered to be contradictory properties.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] A treatment liquid containing an organic resin and one or more of phosphate-based, chromate-based, and dichromate-based treatment liquids, each with a viscosity adjusted to 300 to 5000 cp, or an aqueous solution is applied to the surface of the electrical steel sheet. A film treatment solution of either a synthetic resin or an emulsion resin is applied using a natural reverse method using a gravure roll as a pick-up roll, and then baked to achieve a surface roughness of Ra of 0.5 to 1.5.
A method for forming an insulating film on an electrical steel sheet with excellent punchability and weldability, characterized by having a thickness of .mu.m.