JP3370261B2 - Electrical steel sheet with insulating coating that can be manufactured by high-speed coating and low-temperature baking and has excellent TIG weldability and post-annealing performance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric steel sheet with an electric insulation coating, which can be manufactured by high-speed coating and low-temperature baking, has excellent TIG weldability, resists strain relief annealing, and has excellent performance after annealing.

[0002]

2. Description of the Related Art Insulating coatings of electromagnetic steel sheets are required to have various properties such as performance as a final product and performance required in a product manufacturing process, as well as being excellent in electrical insulation. For example, punchability, TIG weldability, coating adhesion, corrosion resistance, etc. may be mentioned. Therefore, depending on the application,
Various insulating coatings are used properly. Of these, punchability and TIG weldability are items that are difficult to achieve as conflicting performances. That is, the organic coating is effective for improving the punchability, but the organic matter is thermally decomposed during TIG welding and causes gas generation. In order to meet such demands, the semi-organic insulation coating containing an organic resin and an inorganic material is most widely used because it shows punchability far superior to that of an inorganic coating in the production of one coat and one bake. Various methods of improving weldability have been devised. In order to improve the TIG weldability, it is effective to add roughness to the surface of the steel sheet in order to secure the escape route of the generated gas, but there is a problem that the space factor decreases. Also,
Although there is a method of controlling the steel plate composition, it is substantially difficult to change the steel composition for the purpose of improving TIG weldability because the steel composition of the electromagnetic steel sheet needs to be changed according to the required magnetic properties. . On the other hand, as a method for suppressing the amount of gas itself generated from the coating film, Japanese Patent Laid-Open No. 6-235070.
The publication discloses a method of improving the TIG weldability by setting the peak temperature at which the amount of change in weight when the sample is heated at a constant rate of temperature rise in the differential thermogravimetric measurement of the resin to be mixed is 400 ° C. or higher. ing. According to this method, the effect of improving the TIG weldability is certainly seen, but it does not reach the inorganic coating and further improvement of the TIG welding is desired.

[0003] Magnetic steel sheets are often subjected to strain relief annealing in order to remove strain during shearing and improve magnetic properties. The stress relief annealing is usually performed at a high temperature of 700 ° C. or higher, and in an organic coating, the resin thermally decomposes and becomes a gas, and the coating disappears, so that the steel sheets fuse together (sticking) and the eddy current loss increases. Problem arises. Therefore, when strain relief annealing is performed, the inclusion of an inorganic component is essential. Various insulating coatings have been developed as coatings that resist strain relief annealing, and insulating coatings that become insoluble by heating, such as chromic acid-based or phosphoric acid-based, are the mainstream. Most of the conventional chromate-based coats contain a divalent metal and an organic reducing agent. For example, Japanese Patent Laid-Open No. 6-235070 also contains at least one divalent metal and an organic reducing agent for lowering the baking temperature. However,
Even if an organic reducing agent is added, the chromate-based semi-organic coat containing divalent metals such as Ca and Mg needs to be baked at high temperature in order to reduce water-soluble hexavalent Cr to water-insoluble trivalent Cr. It was

Further, insolubilization of the phosphate coating requires a dehydration reaction, and even if a reaction accelerator is added, it is necessary to bake at a higher temperature than the chromium coating. In order to improve the performance of such chromic acid-based and phosphoric acid-based coatings after stress relief annealing, a method of adding boric acid has been conventionally used. For example, in Japanese Examined Patent Publication No. 6-104905, rust resistance is secured by containing a predetermined amount of boric acid in a chromic acid-based treatment liquid. Boric acid is often added to improve not only corrosion resistance after annealing but also adhesion after annealing, sticking property, and the like. However, since boric acid has a low solubility at room temperature, it is necessary to reduce the liquid concentration in order to mix a large amount of boric acid in order to improve the performance after annealing.
On the other hand, in a normal coating method such as a roll coater, when the coating speed is increased for the purpose of improving productivity, the liquid film is stretched, and as a result, the basis weight is reduced and it becomes difficult to secure the wet film thickness. In such a case, in order to increase the basis weight, there is a method of increasing the concentration of the solution, but as described above, it is difficult to increase the concentration of the solution containing boric acid. There are cases where you cannot do it.

[0005]

As described above, there is a demand for a coating film which has both punchability and TIG weldability without lowering the space factor, and at present, the space factor and the performance after annealing are deteriorated. At present, there is no coating that retains the excellent punchability level of the organic coating and the excellent TIG weldability level of the inorganic coating.

Further, when boric acid is added for the purpose of improving the performance after stress relief annealing, it is necessary to make the solution thin in order to dissolve boric acid, and there is a problem that the film thickness cannot be secured and the coating speed cannot be increased. It was Further, in the conventional technology that requires high temperature baking, the fuel cost is uneconomical, and when operating near the limit of the capacity of the furnace,
If the line speed is increased, the desired baking temperature cannot be obtained, and there is a problem that the workability of mass production is significantly impaired. The present invention has been made to solve the above-mentioned problems, and has excellent TIG weldability without impairing the space factor and punchability, can be manufactured by high-speed coating and low-temperature baking, and has excellent performance after annealing. An excellent electromagnetic steel sheet with an insulating coating is provided.

[0007]

Means for Solving the Problems As a result of investigations aimed at solving the above problems, the inventors have found that in order to reduce the reduction temperature of a chromic acid-based coating to enable low-temperature baking, It has been found that it is necessary to keep the amount of high alkali metal or alkaline earth metal below a specified amount. It was also found at the same time that the use of chromic anhydride or aluminum dichromate as the main component is the most effective in reducing the reduction temperature. It was also found that the TIG weldability can be greatly improved without impairing the space factor and punchability by blending the aluminum compound in a prescribed amount or more. Although this method alone can provide excellent TIG weldability, it was also found that by setting the thermal decomposition temperature of the resin to be blended to a specified value or higher, extremely excellent TIG weldability comparable to that of an inorganic insulating coating can be obtained. It was

[0008] A coating formed only by combining chromic acid, an Al compound, and a resin has a performance (adhesion, corrosion resistance, etc.) after strain relief annealing when the basis weight is increased to obtain a high interlayer resistance.
Turned out to be inferior. Attempts have been made to apply the conventionally known method of adding boric acid. However, when boric acid having a low solubility is added, the concentration of the coating solution becomes low, which causes a problem that a predetermined basis weight cannot be secured.

Therefore, as a result of intensive studies by the inventors,
Including a certain amount of phosphoric acid or phosphate in the membrane
Therefore, after stress relief annealing without reducing the concentration of the coating liquid,
We have found that we can improve performance. Phosphoric acid used
The drug is not particularly limited, but is not limited to phosphoric acid and
And the first phosphate can be preferably applied from the viewpoint of solubility. Was
However, when using phosphate, alkali metal or
Prevents the alkaline earth metal from exceeding a certain amount.
For this purpose, aluminum phosphate monobasic and phosphoric acid are the most
It can be suitably applied. That is, for chromic acid type electromagnetic steel sheets
Regarding the insulating coating, the composition in the coating is chromic acid is CrO.₃
Conversion of Al compound to Al metal based on 100 parts by weight
Including 2.5 to 30 parts by weight, the resin solid content is 0 to 100.
Parts by weight, H or phosphoric acid or phosphate ₃PO_Four5 in conversion
100 parts by weight of alkali metal or alkali in the treatment liquid
Potassium earth metal content is CrO₃Converted to 100 parts by weight
On the other hand, if the amount is 1 part by weight or less, high-speed coating and low
Can be manufactured by hot baking, and has excellent TIG weldability and performance after annealing.
A magnetic steel sheet with an insulating coating is provided. In the insulating film
The resin to be mixed heats the resin solids at a constant heating rate.
The peak temperature at which the amount of weight change is maximum when the temperature is 400 ° C or higher
The above is preferable. The adhesion amount of the insulating film is 0.
05-7g / m²Is preferred.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. A magnetic steel sheet is used as the starting material of the present invention.
The electromagnetic steel sheet adjusts the components in the steel in order to change the specific resistance and obtain desired magnetic characteristics. Therefore, various electrical steel components are used as the electrical steel sheet, but the present invention is not limited to the electrical steel components and is applicable to electrical steel sheets of any composition.

The treatment liquid used in the present invention is such that the amount of Al in the coating film after drying is 100 parts by weight in terms of CrO ₃ relative to Al.
It is an aqueous solution containing at least one of chromic anhydride, aluminum chromate and aluminum (di) chromate as a main component, which is contained in an amount of 2.5 to 30 parts by weight in terms of metal. In the case of the chromic anhydride base agent, the aluminum compound is dissolved. As the soluble aluminum compound, for example, oxides, hydroxides, carbonates, phosphates and the like can be used. When the amount of Al is less than 2.5 parts by weight, the TI when the resin is contained
G weldability is insufficient, and if it is 30 parts by weight or more, the Cr ratio decreases, so that the performance such as corrosion resistance deteriorates. The Al amount is preferably 8 to 20 (Al equivalent amount based on 100 parts by weight of CrO ₃ equivalent).

The resin solid content is CrO.₃100 in conversion
It is 0 to 100 parts by weight with respect to parts by weight. Resin punching
It is not necessary to add it if the materiality is not important, but
When placing importance on it, it is effective to add a large amount of resin.
However, if the resin content exceeds 100 parts by weight, the TIG weldability will be poor.
The resin solid content is 0 because the corrosion resistance after strain relief annealing is also reduced.
Up to 100 parts by weight. If the resin does not contain TIG
Although excellent in weldability but inferior in punchability, it is preferably 5
Up to 100 parts by weight. For purposes such as high-speed coating and thick coating
To improve performance after stress relief annealing without lowering the liquid concentration
And phosphoric acid or phosphate as CrO₃100 weight converted
H to the department ₃PO_Four5-100 in terms of conversion, preferably
Add 10 to 60 parts by weight. Distortion when less than 5 parts by weight
After annealing, the performance (adhesion, corrosion resistance, etc.) is insufficient and 100 weight
If the temperature exceeds 200 parts, phosphorus elution may occur during low temperature baking at about 200 ° C.
Problem occurs. When using phosphate as aluminum phosphate
If the total amount of aluminum in the coating is the above amount,
To do.

In order to perform low temperature baking, the amount of alkali metal or alkaline earth metal ions contained in these aqueous solutions is 1 part by weight or less based on 100 parts by weight of CrO ₃ . This is because if it exceeds 1 part by weight, the reduction reaction temperature of chromium becomes high and high-speed low-temperature production becomes difficult. Examples of the alkali metal or alkaline earth metal ions contained in the treatment liquid include Na, K, Mg, Ca and the like.

A reducing agent may be added to reduce Cr ⁶⁺ of the dichromate to Cr ³⁺ . Although various reducing agents can be used, organic reducing agents can be suitably applied. If it is an organic reducing agent, it is 5 to 10 with respect to 100 parts by weight of CrO _3.
An amount of 0 parts by weight is used. If the amount of the organic reducing agent is less than 5 parts by weight, reduction is insufficient during low temperature production and the coating becomes sticky or chromium elutes to destroy the environment. On the other hand, if it exceeds 100 parts by weight, further reduction of the reduction temperature cannot be expected, and
The reducing agent remaining in the coating during baking at low temperature increases TI
G Reduces weldability. The type of reducing agent is not particularly limited, but polyhydric organic alcohols such as ethylene glycol, sucrose, and glycerin, and carboxylic acids such as formic acid and acetic acid are preferably applied. However, as described above, the reducing agent is not limited to the organic reducing agent, and an inorganic reducing agent can be applied as long as the similar reduction reaction can be expected.

Although any resin to be added to the treatment liquid has a TIG weldability superior to that of the conventional semi-organic insulating coating, the change in weight when the resin solid content is heated at a constant heating rate. The peak temperature at which the amount reaches its maximum is 400 ℃
By setting it as the above, the performance which is remarkably excellent as an inorganic insulating film coat can be obtained. The resin described in Japanese Patent Application Laid-Open No. 6-235070 previously invented by the authors can be applied very suitably. Even if the thermal decomposition peak temperature is less than 400 ° C, the weldability is superior to that of the chromate-based semi-organic insulating film coat containing no Al compound, but at 400 ° C or higher, the weldability is remarkably excellent. However, even when the thermal decomposition peak temperature is 400 ° C. or lower, by setting the amount of Al to 100 parts by weight of CrO ₃ to 8 to 20 parts by weight, the thermal decomposition peak temperature in the chromic acid-based coating containing no divalent metal and not containing Al can be increased. Containing a resin having a temperature of 400 ° C. or higher, the TI which is superior to the invention described in JP-A-6-235070 previously invented by the present inventors.
It has been confirmed that it exhibits G weldability. Therefore, a resin having a thermal decomposition peak temperature of 400 ° C. or lower is also applicable when extremely excellent TIG weldability comparable to that of the inorganic insulating coating is not required.

Further, when coating at a high line speed, it is effective to add a surfactant from the viewpoint of ensuring the stability of the liquid. These surfactants are not particularly specified, but the inventors previously invented JP-A-7-2
The method described in Japanese Patent No. 86284, which satisfies the performances of both mechanical stability and foam breakage, can be suitably applied. However, if the line speed is not increased extremely, such a measure is not necessary.

A film is formed by mixing the above chemicals, applying the chemicals on an electromagnetic steel plate, and baking it. As a method for forming an insulating film, a method generally used in industry can be applied, and various methods such as a roll coater method, an air knife method, and a bar coater are used. Regarding the baking method, it is possible to perform baking at a low temperature for a short time, and reach a plate temperature of 120 to 25
The reduction reaction of chromium proceeds sufficiently at 0 ° C. If it is desired to print at a lower temperature, it is advisable to add a reducing agent near the upper limit. Of course, if the temperature is lower than 400 ° C, where the thermal decomposition of the resin begins, baking at 250 ° C or higher is possible. Therefore, even when various coatings are manufactured in a line, the temperature control range is wide, so there is no time loss when changing the furnace temperature. It is possible to
Further, since the amount of deposition of the insulating film is lowered and punching property is less than 0.05 g / m ^2, the adhesion is reduced to be 7 g / m ^2, greater than the unit weight 0.05 to 7, Preferably 0.
It is preferably ³ to 3 g / m ² . Other additives may be added to further improve the performance of the coating.

[0018]

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 1) 0.5 mm thick, Si 0.
35 wt%, Al 0.003 wt% (the balance Fe) in the electrical steel sheet, the component is 100 parts by weight of CrO ₃ ,
Al 0-30 parts by weight (Al metal equivalent), H ₃ PO ₄
30 parts by weight, ethylene glycol 35 parts by weight, acrylic / styrene / epoxy resin (thermal decomposition peak temperature 410
° C.) or vinyl acetate / acrylic resin (thermal decomposition peak temperature 360 ° C.) a treating solution containing 100 parts by weight of the resin amount upper limit, basis weight 1 g / m ^2, was formed by baking the insulating coating at an ultimate temperature of 200 ° C.. FIG. 1 shows the effect of the Al content on the TIG weldability (the limit welding speed at which blowholes do not occur). The TIG welding condition is electrode: Th-W 2.6.
mmφ, pressing force: 100 kg / cm ² , current: 120 A, shielding gas: Ar 61 / min, and welding speed was evaluated in the range of 200 to 1000 mm / min where an appropriate bead thickness can be obtained. In the examples, the thermal decomposition peak temperature was measured at a temperature rising rate of 20 ° C./min using a differential type differential thermal balance manufactured by He Chugaku Rigaku Co., Ltd.

(Example 2) 0.5 mm thick, Si 0.3
A magnetic steel sheet of 5 wt% and Al of 0.003 wt% (the balance is Fe), the composition of which is A with respect to 100 parts by weight of CrO _3.
l 8 parts by weight (converted to Al metal), 30 parts by weight of H ₃ PO ₄ , 40 parts by weight of ethylene glycol, 30 parts by weight of acrylic / epoxy resin (thermal decomposition peak temperature 423 ° C.), a coating weight of 2 g / m ² Then, it was baked at an ultimate plate temperature of 180 ° C. to form an insulating film. FIG. 2 shows the influence of the alkaline earth metal (Mg) content on the chromium elution amount. The acceptance criterion for the chromium elution amount was 20 μg / 100 cm ² or less. Other alkali metals and alkaline earth metals other than Mg also showed the same tendency as in FIG.

(Example 3) Table 1 shows the results of investigation of the coating performance with the composition shown in Table 1. Coating baking plate temperature is 200 ℃
And TIG Weldability Welding was carried out under the following conditions, and the maximum welding speed at which blowholes did not occur was evaluated. Electrode: Th-W 2.6 mmφ Pressurizing force: 100 kg / cm ² Current: 120 A Shielding gas: Ar 6 L / min * ◎: over 1000 mm / min ◎: 800-1000 mm / min ○: 600-less than 800 mm / min △: 400 to less than 600 mm / min ×: less than 400 mm / min

Chromium Elution Amount The Cr elution amount after 10 minutes immersion in boiling water was investigated. ⊚: less than 10 μg / 100 cm ² ◯: 10 to 20 μg / 100 cm ² Δ: less than 20 to 50 μg / 100 cm ² ×: more than 50 μg / 100 cm ²

Corrosion resistance (product plate) Salt blast (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

Corrosion resistance (after annealing) After annealing at 750 ° C. for 2 hours in nitrogen, a constant temperature and humidity test (50 ° C.,
Relative humidity 80%) The red rust area ratio after 14 days was evaluated. A: 0 to less than 20% O: 20 to less than 40% B: 40 to less than 60% X: 60 to 100%

Adhesion was evaluated by the film peeling rate after a 180 ° bending back test at 20 mmφ. ◎: No peeling ○: ～ Peeling less than 20% △: Peeling 20 to less than 40 %% ×: Peeling 40% to full peeling

Interlayer Resistance The interlayer resistance value was measured according to JIS C 2550. ◎: 40Ωcm ² / sheet than ○: 5~40Ωcm ² / sheet △: less than 0~5 Ωcm ² / sheet ×: No resistance

Space factor The space factor was measured according to JIS C 2550. A: 99% or more O: 98 to less than 99% B: 97 to less than 98% X: less than 97%

Punchability 15mmφ steel die, burr height is 50μ
Evaluated by the number of punches until reaching m. ◎: Over 1.5 million times ○: 1 to 1.5 million times △: 700,000 to less than 1 million times ×: Less than 700,000 times

The coating weight loss after solvent resistance boiling xylene in 6 hour immersion ◎: less than 0.05g / m ² ○: less than ^{0.05~0.1 g / m 2 △: 0.1~0.2g} / m ² ×: over 0.2 g / m ²

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

Since the present invention is constructed as described above, it can be manufactured by high-speed coating and low-temperature baking, and has excellent TIG weldability, post-annealing performance, and excellent insulation film performance.
It can be widely used for applications such as motors and transformers.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of Al content on TIG weldability.

FIG. 2 is a graph showing the effect of the amount of divalent metal on the elution property of chromium.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23C 22/00-22/86 B05D 7/14 C22C 38/00 303

Claims (3)

(57) [Claims] 1. The composition in the coating film contains chromic acid in an amount of 2.5 to 30 parts by weight in terms of Al metal and 2.5 to 30 parts by weight of resin compound based on 100 parts by weight of CrO _{3 in} terms of CrO _3. , Phosphoric acid or phosphate in the range of 5 to 10 in terms of H ₃ PO ₄
It contains 0 parts by weight, and the content of alkali metal or alkaline earth metal in the treatment liquid is 1 part by weight or less based on 100 parts by weight of CrO ₃ , which can be produced by high-speed coating and low temperature baking, and has TIG weldability. And an electrical steel sheet with an insulating coating that has excellent performance after annealing. 2. The peak temperature at which the resin mixed in the insulating coating shows a maximum weight change amount when the resin solid content is heated at a constant heating rate is 400 ° C. or higher. A magnetic steel sheet with an insulating coating that can be manufactured by high-speed coating and low-temperature baking, and has excellent TIG weldability and performance after annealing. 3. The adhesion amount of the insulating coating is 0.05 to 7 g /
m ² is an electromagnetic steel sheet with an insulating coating, which can be produced by high-speed coating and low-temperature baking according to claim 1 or 2, and has excellent TIG weldability and post-annealing performance.