JPH09136061A - Electromagnetic steel plate bearing insulating coating formable by burning at low temperature and able to be annealed for strain removal and having excellent weldability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic steel plate bearing an insulating coating which does not contain harmful compounds such as hexavalent chromium compounds, is able to be formed by burning at low temperature and annealed for strain removal, and has high weldability. SOLUTION: The claimed electromagnetic steel plate is one bearing an insulating coating which contains resin and silica at a ratio, 100 pts.wt. of a resin solid component in the resin and 20-500 pts.wt. of silica solid component, is able to be formed by burning at low temperature and annealed for strain removal, and has high weldability, and the resin has the lowest film-formable temperature within a range from -20 to 60 deg.C and the peak temperature not lower than 400 deg.C at which the alteration degree of weight becomes the maximum when being heated at 21 constant temperature raising speed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention does not contain harmful compounds such as hexavalent chromium, and can be produced by low temperature baking.
The present invention relates to a magnetic steel sheet with an insulating coating that can be annealed for strain removal and has good weldability.

[0002]

2. Description of the Related Art Insulating coatings for electrical steel sheets not only have interlayer resistance, but also punchability, TIG weldability, coating adhesion, corrosion resistance,
Various performances such as heat resistance, sticking resistance, tension pad resistance, and corrosion resistance after stress relief annealing are required, and various insulating coatings have been developed according to the application. In addition, the electromagnetic steel sheet has a thickness of 750 to 8 in order to improve magnetic properties after punching.
In many cases, strain relief annealing is performed at about 50 ° C. Insulating coatings are roughly classified into three types: inorganic coatings that emphasize weldability and heat resistance, organic resin-containing semi-organic coatings that aim to achieve both punchability and weldability, and organic coatings for special purposes.
It is a coating containing an inorganic substance that withstands strain relief annealing, and in particular, a chromate-based insulation coating containing an organic resin can be manufactured by one coat and one bake, and has significantly better punchability than an inorganic insulation coating. It is widely used because it can be improved.

For example, in Japanese Patent Publication No. 60-36476, a dichromate-based aqueous solution containing at least one divalent metal is used and 100 parts by weight of CrO ₃ in the aqueous solution is used as an organic resin of vinyl acetate / Beova ratio is 90 / 10-40
/ 60 resin emulsion in the ratio of resin solids
~ 120 parts by weight and 10 to 60 parts by weight of an organic reducing agent are applied to the surface of a dough iron plate, and a method of insulating film forming of an electrical steel sheet obtained through a baking process according to a conventional method is disclosed. There is. In addition, the authors of the present invention, Japanese Patent Laid-Open No. 6-2
No. 35070 is an electrical steel sheet having an electrically insulating coating on its surface, and the peak temperature at which the amount of weight change when the sample is heated at a constant heating rate in differential thermogravimetry is 400 ° C. or higher. And a resin fine particle emulsion having chromium acid resistance, a chromate-based aqueous solution containing at least one kind of divalent metal, and an organic reducing agent were applied to the surface of the electromagnetic steel sheet and baked. We have invented an electrical steel sheet with an electric insulating coating with good weldability, and have realized coexistence of both stability and weldability with chromate. However, the chromate-based coating needs to be baked at a relatively high temperature in order to reduce hexavalent chromium to trivalent and insolubilize it. Further, since hexavalent chromium is highly toxic, there is a concern of environmental pollution, and waste liquid treatment is costly.

[0004] As a technique using a material other than chromic acid as a main component, a semi-organic insulating coating using a phosphate as a main component has been studied. However, it is necessary to bake the phosphate at a high temperature after coating in order to promote the dehydration reaction and make it insoluble. As a semi-organic insulating coating that can be baked at a relatively low temperature, an aqueous solution containing a water-soluble or emulsion-type resin as a main component, which is subsequently composed of an inorganic colloidal substance by utilizing the heat of continuous annealing in Japanese Patent Publication No. 59-21927. Is disclosed and a method for applying a strain relief annealing seizure prevention coating to an electromagnetic steel sheet which is coated with and then temper-rolled as it is.

[0005]

[Problems to be Solved by the Invention] Japanese Patent Publication No. Sho 59-2192
According to the method described in Japanese Patent Publication No. 7, the inorganic colloidal substance can be baked at a lower temperature than the chromate-based and phosphate-based films. That is, chromate-based,
In order to prevent stickiness, the phosphate system needs to proceed with the film-forming reaction from water-soluble to water-insoluble, but the inorganic colloidal substance does not need to do so. However, in the invention of Japanese Examined Patent Publication No. 59-21927, in which the resin is not simply defined by the combination of the inorganic colloidal substance and the resin, the seizure prevention and the punchability at the time of strain relief annealing are satisfied, but the weldability and other factors are satisfied. There is a problem that performance is inferior and satisfactory performance cannot be obtained as a general-purpose coat. The present invention has been made to solve the above-mentioned problems, and provides a general-purpose coat which can be manufactured by low-temperature baking, is capable of strain relief annealing, and is excellent in various film performances.

[0006]

Means for Solving the Problems As a result of investigations aimed at solving the above-mentioned problems, the inventors have produced a resin by low-temperature baking by using a resin in which the minimum film-forming temperature and the thermal decomposition temperature are regulated and silica. The present invention has been achieved by finding that an insulating coating film that can be obtained, can be subjected to strain relief annealing, and has good weldability can be obtained.

According to the present invention, the minimum film forming temperature is -20 to
A resin having a peak temperature of 400 ° C. or higher at which the amount of change in weight at the time of heating at 60 ° C. and a constant heating rate is maximum,
It can be manufactured by low temperature baking characterized by containing silica and having a silica solid content of 20 to 500 parts by weight with respect to 100 parts by weight of the resin solid content in the resin, and strain relief annealing is possible and weldability is also good. An electromagnetic steel sheet with an insulating coating is provided. here,
The resin is preferably cross-linked with a thermosetting resin or a curing agent in advance. Insulation coating amount is 0.05 ~
It is preferably 4 g / m ² . The minimum film-forming temperature (MFT) is the lowest temperature at which the resin particles start to fuse.

[0008]

The present invention will be described below in more detail. An electric iron plate is used as the starting material of the present invention. A water-based resin (aqueous emulsion resin, dispersion resin or water-soluble resin) is used as the resin to be added to the treatment liquid. When the resin is an emulsion or dispersion, the minimum film forming temperature is required to be -20 to 60 ° C. Here, the minimum film-forming temperature (MFT) is the minimum temperature at which the resin particles start to fuse. The water-based resin drying process is
In the case of water-soluble resin, a film is formed when water evaporates, but in the case of emulsion or dispersion, evaporation of water and fusion of resin particles are required to form a film, so it must be dried above the minimum film formation temperature. Poor film formation. When the minimum film forming temperature of the resin is higher than 60 ° C, when the low temperature baking of about 100 ° C is performed, the film forming is incomplete and dusting occurs, and when the minimum film forming temperature is less than -20 ° C, the film is Since stickiness occurs, the minimum film forming temperature is set to -20 to 60 ° C.

Further, it is necessary that the peak temperature at which the amount of change in weight when the resin is heated at a constant temperature rising rate becomes maximum is 400 ° C. or higher. If it is less than 400 ° C, the area of the heat-affected zone during TIG welding becomes large, which causes a problem that blowholes easily occur.

In order to raise the thermal decomposition temperature of the resin, it is effective to crosslink the inside of the resin particles. The resin used for the insulating coating of the present invention has a minimum film forming temperature of −20 to 60 ° C., and a peak temperature at which the amount of weight change when heating at a constant temperature rising rate is maximum is 400, preferably 410 ° C. or more. Although the resin composition is not particularly limited, examples of resins that achieve this condition include acrylic resin, alkyd resin, polyolefin resin, styrene resin, epoxy resin, phenol resin, urethane resin, melamine resin, etc. One or two or more resins having a temperature of −20 to 60 ° C. can be suitably applied, and other than this, any resin having a minimum film forming temperature of 60 ° C. or less shown in each manufacturer's resin catalog or the like can be applied. . Even a water-based resin may contain a large amount of a water-soluble organic solvent, and even in that case, it is possible to achieve low-temperature short-time baking by paying attention to the minimum film forming temperature. Further, in order to set the peak temperature at which the amount of change in weight when heating at a constant temperature rising rate is maximum to 400 ° C. or higher, it is an effective means to pre-crosslink the resin. For example, even if a melamine resin, which is a typical curing agent, is simply blended, in the case of baking at a low temperature and a short time at a plate temperature of about 100 ° C., the crosslinking reaction hardly progresses. Therefore, it is preliminarily crosslinked with a thermosetting resin or a curing agent at the time of resin production. As such a thermosetting resin or curing agent, various curing methods such as various epoxy resins, urethane resins (isocyanates), melamine resins, amino resins and the like can be applied.

The silica compounded in the treatment liquid may have any shape as long as it can be dispersed in water, and various shapes such as colloidal silica, vapor phase silica and agglomerated silica are applicable. Further, when importance is attached to weldability, when the film thickness is near the upper limit, or when the resin content is large, it is effective to use silica surface-treated with Al. Although the cause is not obvious, the presence of Al improves the weldability. 20 to 500 parts by weight of silica solids are mixed with 100 parts by weight of resin solids. If it is less than 20 parts by weight, the sticking property during stress relief annealing and the film performance after stress relief annealing will deteriorate, and if it exceeds 500 parts by weight, punchability will deteriorate, so the amount of silica is from 20 to 500, preferably 50.
To 400 parts by weight.

A film is formed by mixing the above chemicals, applying the chemicals on an electromagnetic steel sheet, and baking. The insulating coating forming method is a roll coater method which is generally used industrially,
Various methods such as a flow coater, spray coating and knife coater can be applied. The baking method is not particularly limited such as hot air type, infrared type, induction heating type, etc. which are usually carried out. It is possible to bake for a short time.

The dry coating amount is preferably 0.05 to 4 and more preferably 0.2 to 1.5 g / m ² . 0.
If it is less than 05 g / m ^{2, the} sticking property deteriorates and 4
If it exceeds g / m ² , the weldability and adhesion will deteriorate. In addition,
In order to further improve the performance of the coating film, an additive such as a rust preventive agent may be added.

[0014]

EXAMPLES The effects of the present invention will be specifically described below based on examples, but the present invention is not limited to these examples. (Example) The coating film shown in Table 1 was formed on the surface of an electric iron plate having a plate thickness of 0.5 mm. Application is performed with a roll coater,
The plate was baked at an ultimate plate temperature of 100 ° C. and allowed to cool, and then subjected to the test. The adhesiveness and corrosion resistance were evaluated for the product plate after being left to cool and the annealed plate after strain relief annealing at 750 ° C. for 2 hours in N ₂ . The details of each performance evaluation method are as follows. As is clear from Table 1, all examples of the present invention are magnetic steel sheets with an insulating coating, which are excellent in corrosion resistance, punchability, electrical insulation, heat resistance, weldability, adhesion and the like.

Corrosion resistance Salt spray (5% NaCl solution) test showed a red rust area ratio of 10
It was evaluated by the time when it became more than%. ◎: 15 hours or more ○: 7 to less than 15 hours △: 4 to less than 7 hours ×: 0 to less than 4 hours

Adhesion was evaluated by a film peeling rate after a 180 ° bending back test at 20 mmφ. ：: No peeling ：: ~ Peeling less than 20% 剥離: Peeling 20% ~ Peeling less than 40% ×: Peeling 40% ~ Peeling

Chromium elution amount The amount of Cr elution after 10 minutes immersion in boiling water was investigated. ◎: less than ^{0.2mg / m 2 ○: 0.2~0.5mg /} m less than ^{2 △: 0.5~1.0mg ×: 1.0mg /} m 2 more than

TIG Weldability Welding was carried out under the following conditions and evaluated at the maximum welding speed at which blowholes were not generated. Electrode: Th-W 2.6 mmφ Pressurizing force: 100 kg / cm ² Current: 120 A Shielding gas: Ar6 L / min ◎: 600 mm / min Super ○: 400 to 600 mm / min △: 300 to less than 400 mm / min ×: 300 mm / min Less than

Interlayer resistance The interlaminar resistance value was measured according to JIS method 2. ◎: 10Ωcm ² / sheet than ○: 5~10Ωcm ² / sheet △: 3~5Ωcm ² / sheet less than ×: 3Ωcm less than ² / sheet

[0020] In the punching properties 15mmφ steel dice, back height is 50
The evaluation was performed by the number of punches until reaching μm. ◎: more than 500,000 times ○: 300,000 to 500,000 times △: 100,000 to less than 300,000 times ×: less than 100,000 times

Sticking property 10 sheets of 50 mm square steel sheets are stacked and loaded (200 g / cm
After annealing at 750 ° C. for 2 hours in a nitrogen atmosphere while applying ² ), a weight of 500 g was dropped on a steel plate, and the drop height at the time of dividing into five was investigated. ◎: 10 cm or less ○: 10 to less than 15 cm △: 15 to 30 cm ×: more than 30 cm

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it can be manufactured by low temperature baking, strain relief annealing is possible, and weldability is good. Since it has a coating that combines, the motor,
It can be widely used as a magnetic steel sheet for applications such as transformers.

Claims (4)

[Claims] 1. A resin containing silica, which has a minimum film forming temperature of -20 to 60 ° C. and a peak temperature of 400 ° C. or more, which shows a maximum weight change amount when heated at a constant temperature rising rate, and silica.
An electrical steel sheet with an insulating coating, which can be produced by low temperature baking, is capable of strain relief annealing, and has good weldability, characterized in that silica solid content is 20 to 500 parts by weight with respect to 100 parts by weight of resin solid content in the resin. . 2. The resin is preliminarily subjected to a crosslinking reaction with a thermosetting resin or a curing agent.
An electrical steel sheet with an insulating coating that can be manufactured by the low temperature bake described above, is capable of strain relief annealing and has good weldability. 3. The silica can be produced by low temperature baking according to claim 1 or 2, characterized in that the surface of the silica particles is surface-treated with Al, and strain relief annealing is possible and weldability is also achieved. Magnetic steel sheet with good insulation coating. 4. The amount of the insulating film deposited is 0.0 on a dry weight basis.
An electrical steel sheet with an insulating coating, which has an insulating film thickness of 5 to 4 g / m ² and can be manufactured by the low temperature baking according to any one of claims 1 to 3, is capable of strain relief annealing and has good weldability.