JP3299459B2 - Non-oriented electrical steel sheet excellent in punching property and seizure resistance after annealing and method for forming insulating film thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention does not include harmful compounds such as hexavalent chromium, and is a non-directional electromagnetic member having high productivity and high punching performance and low seizure resistance after annealing. The present invention relates to a steel sheet and a method for forming an insulating film thereof.

[0002]

2. Description of the Related Art Insulating coatings on magnetic steel sheets have not only interlayer resistance but also punching properties, TIG weldability, coating adhesion, corrosion resistance, solvent resistance, heat resistance, blocking resistance, tension pad resistance, after strain relief annealing. Various performances such as corrosion resistance and seizure resistance are required, and various insulating coatings are being developed according to the application. Further, in order to improve magnetic properties after punching, the steel sheet is often subjected to strain relief annealing at about 700 to 800 ° C. There are three types of insulating coatings: (1) inorganic coatings with emphasis on weldability and heat resistance, (2) semi-organic coatings containing organic resin for both punchability and weldability, and (3) organic coatings for special applications. (1) and (2) are coatings containing inorganic materials that can withstand strain relief annealing.
The chromate-based insulating coating containing an organic resin can be manufactured in one coat and one bake, and is widely used because it has a much better punching property than an inorganic insulating coating.

[0003] For example, Japanese Patent Publication No. 60-36476 discloses a treatment solution prepared by mixing a dichromate aqueous solution containing at least one divalent metal with a vinyl acetate / veova resin emulsion and an organic reducing agent. On the surface of
There is disclosed a method for forming an insulating film on an electromagnetic steel sheet obtained through a baking step by a conventional method. This electrical steel sheet with an insulating coating satisfies various performances such as corrosion resistance and solvent resistance. 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. Therefore, baking at high temperature,
In view of an increase in energy consumption during production and a reduction in the processing speed of the insulating film, the cost is increased. In the case of a semi-organic film, the resin is thermally deteriorated at the time of baking, and the original performance of the resin may be impaired. In addition, hexavalent chromium has a problem of environmental pollution, and there is a problem that costs are required for exhaust treatment and waste liquid treatment.

As a technique using an inorganic substance other than chromic acid, a semi-organic insulating coating containing a phosphate has been studied. However, the phosphate needs to be baked at a higher temperature after painting in order to make the phosphate dehydrated and insolubilize. A semi-organic insulating film which can be baked at a relatively low temperature and does not contain chromic acid is disclosed in JP-A-54-315.
No. 98, a treatment liquid comprising a silica hydrosol and an organic substance is applied to the surface of a steel sheet, and heated at a temperature of 100 to 350 ° C., whereby heat resistance and seizure resistance containing silica gel containing an organic substance as a main component are applied. An electromagnetic steel sheet having a conductive film and a surface treatment method thereof are disclosed. As a method of forming a film before temper rolling by using heat during continuous annealing and applying an anti-seizure film during strain relief annealing, for example, Japanese Patent Publication No. Sho 59
No. 21927 discloses a method of applying an aqueous solution containing an inorganic colloidal material as a main component, a water-soluble or emulsion-type resin, and subjecting the steel to temper rolling as it is, so as to apply a strain relief annealing seizure prevention coating to an electromagnetic steel sheet. It has been disclosed.

[0005]

[Problems to be Solved by the Invention]
No. 8 and Japanese Patent Publication No. 59-21927 mainly aim at preventing seizure after annealing. The silica hydrosol described in JP-A-54-31598 and the inorganic colloidal material described in JP-B-59-21927 are certainly baked at a lower temperature than chromate-based and phosphate-based coatings. Is possible. That is, in order to prevent stickiness, the chromate-based and the phosphate-based require that the film-forming reaction from water-soluble to water-insoluble be advanced by high-temperature heating, but the inorganic colloidal substance is not required. However, these techniques are merely based on a combination of a silica hydrosol or an inorganic colloidal substance and a resin, and although the effect of preventing seizure after annealing is recognized, other performances are inferior and their applications are limited. Specifically, in JP-A-54-31598, as is clear from the examples, the comparative examples containing chromate salt did not produce rust in the wet test, whereas the comparative examples containing chromate did not show any rust. Has rusted. Tokiko Sho 59
In JP-A-21927, there is no description about corrosion resistance and the like, and as a result of examining the performance of an electromagnetic steel sheet provided with an insulating coating composed of a vinyl acetate-acrylic copolymer resin and various inorganic colloidal substances, which is used only in the examples, Film performance such as resistance and solvent resistance did not satisfy the performance of chromate-based general-purpose coatings required by manufacturers of electrical steel sheets. The present invention is a non-oriented electrical steel sheet coated with a chromium-free resin-silica-based organic-inorganic mixed composition,
It was made to solve the above-mentioned film defects such as corrosion resistance and solvent resistance, and it is possible to perform strain relief annealing on the surface of non-oriented electrical steel sheet that performs final finish annealing and temper rolling as necessary on a high-speed line. The present invention provides a method for producing a non-oriented electrical steel sheet having excellent punching properties and excellent seizure resistance after annealing having a resin-silica-based insulating film that exhibits excellent corrosion resistance without using chromic acid. .

[0006]

As described in the prior art, inorganic colloidal silica is a substance having excellent heat resistance and extremely effective in preventing seizure of a steel sheet, but silica alone has poor adhesion to a steel sheet. And poor lubricity, poor punching properties, and poor coverage, causing rust easily. On the other hand, an organic resin has properties completely opposite to those of inorganic colloidal silica, such as excellent punching properties and adhesion properties, but poor heat resistance. Therefore, an insulating coating of an organic-inorganic mixed composition aimed at the advantages of both has been developed,
As described above, this method is not sufficient in corrosion resistance, and has a problem that rust easily occurs in a high-temperature and high-humidity environment.

In order to solve the above-mentioned problems, the present invention has examined in detail the factors that affect the corrosion resistance of a resin-silica mixed coating, and as a result, the corrosion resistance greatly changes depending on the coating structure, and the coating structure is dispersed in a processing solution. The present inventors have newly found that there is a relationship between the surface area occupied by the organic resin composed of the fine particles and the colloidal silica particles, and have completed the present invention.

That is, the present invention comprises a ratio of 30 to 300 parts by weight of solid colloidal silica with respect to 100 parts by weight of resin solid, and the surface area [specific surface area m ² / g x solid content weight]
Is the surface area occupied by the aqueous dispersion resin particles [specific surface area m ² / g
× solid weight] of a treatment liquid of the organic-inorganic mixed composition in a range of 0.2 to 10 times the unit weight of 1 m ²
The present invention provides a non-oriented electrical steel sheet excellent in punching properties and seizure resistance after annealing, characterized by being coated at 0.1 to 2.0 g / m ² per coating.

Further, in a method for forming an insulating film on an electromagnetic steel sheet, in which an organic-inorganic mixed composition mainly composed of an aqueous dispersion resin and colloidal silica is applied to the surface of a non-oriented electrical steel sheet, On the other hand, the surface area occupied by the aqueous dispersion resin particles is 30 to 300 parts by weight of the solid content of the colloidal silica, and the surface area [specific surface area m ² / g × weight of the solid content] occupied by the colloidal silica particles in the treatment liquid is occupied by the aqueous dispersion resin particles. [Specific surface area m ² / g x solid content weight] 0.2 to
The treatment liquid of the organic-inorganic mixed composition in a range of 10 times was applied in an amount of 0.1 to 2.0 g / m ² per unit area 1 m ^{2 by} weight after drying.
An object of the present invention is to provide a method for forming an insulating film on a non-oriented electrical steel sheet which is excellent in punching property and seizure resistance after annealing characterized by being applied.

[0010]

Hereinafter, the present invention will be described in detail. As a starting material of the present invention, a non-oriented electrical steel sheet obtained by continuously annealing or temper-rolling a cold-rolled sheet in a final finish annealing step is used. The shape of the steel sheet is not limited, and may be sheet-like or coil-like.

In the aqueous dispersion resin used in the present invention, there is no practical problem even if the dispersion medium is basically water and a surfactant or other dispersant for preventing coagulation of the resin is added. As the form of the aqueous resin, three types of a water-soluble type, a dispersion type, and an emulsion type are widely classified, and the aqueous dispersion resin used in the present invention is obtained by dispersing high-molecular polymer fine particles in water. It is a dispersion type and an emulsion type which are uniformly dispersed.
In most cases, the water-soluble form is a form in which the synthesized resin is once dissolved in a hydrophilic solvent. Therefore, they are classified as dangerous substances because they contain a considerable amount of solvent, are difficult to handle, and have higher viscosities than those of the dispersion type and emulsion type, and have problems in dispersibility with silica and coating workability described later. Further, depending on the water dilution ratio, the low-temperature and short-time baking aimed at by the present invention becomes difficult due to a decrease in the non-volatile content. Therefore, the aqueous dispersion resin of the present invention is a dispersion type or an emulsion type, and the resin solid content is 10 to 10. 50
It is a water-dispersed resin having a concentration of% by weight.

The specific surface area of the resin particles dispersed in water is preferably in the range of about 40, taking into account the change in the coating structure due to the mixing of colloidal silica described later.
６００600 m ² / g. The resin composition is not particularly limited, and one or more resins of vinyl acetate resin, epoxy resin, polyolefin resin, styrene resin, acrylic resin, urethane resin, and acrylic resin can be applied.

Another essential component of the insulating coating of the present invention is silica. The shape of the silica is colloidal silica that disperses water, and the specific surface area is 20 to 500 m.
² / g, preferably in the range of 30 to 100 m ² / g. Although the amount of water is not particularly limited, the colloidal silica usually contains 20 to 40% by weight of silica as a solid content. As long as the colloidal silica is compatible with the aqueous dispersion resin having the above-mentioned composition, either an alkaline type or an acidic type can be used. For example, even an acidic type can be used by adjusting the pH with ammonia or the like. It is appropriate to use colloidal silica in an amount of 30 to 300 parts by weight, preferably 50 to 200 parts by weight, as silica solids, based on 100 parts by weight of resin solids. If the amount of the colloidal silica is less than 30 parts by weight, the seizure resistance of the strain relief annealing cannot be said to be sufficient. If the amount of the colloidal silica exceeds 300 parts by weight, the film-forming property is inevitably deteriorated, and the adhesion and corrosion resistance of the coating film tend to deteriorate. Therefore, the excellent punching characteristics characteristic of the present invention are not exhibited.

In order to obtain a film having excellent corrosion resistance in low-temperature and short-time baking using the aqueous dispersion resin of the present invention and colloidal silica as main components, the surface area occupied by the colloidal silica in the treatment solution [specific surface area m ² / g] X solid weight] and the ratio of the surface area occupied by the aqueous dispersed resin particles [specific surface area m ² / g x solid weight] are important requirements.

FIG. 1 shows a treatment liquid obtained by using colloidal silica having the same surface area as the epoxy / acrylic emulsion resin having a different surface area and blending 100 parts by weight of colloidal silica as a solid with respect to 100 parts by weight of the resin solids. 0.5 g / m ² per unit area 1 m ^{2 by} weight after drying
It is a graph of the measurement result of the corrosion resistance and solvent resistance of the product board of the coating film coated to the target. The corrosion resistance and the solvent resistance of the product plate were evaluated by the method described in Example 1. The specific surface area of the emulsion resin and the colloidal silica was determined from the measured value of the average particle diameter by observation with an electron microscope by the Stokes' calculation formula. As is clear from these results, even when the ratio of the solid content of the resin and silica is used within the above-described preferred range, the ratio of the surface area occupied by the resin and silica particles in the treatment liquid falls within the range of the present invention. If the conditions are not satisfied, a film having poor corrosion resistance and solvent resistance is formed.

The inventor paid attention to the structure of the coating film and investigated the cause of the change in the corrosion resistance and solvent resistance depending on the surface area of the resin and silica in the processing solution, and investigated the cross-sectional structure of the coating film. FIG. 2 (a),
(B) is based on 100 parts by weight of the solid content of the emulsion resin.
It is an observation result of an electron microscope at a magnification of 30,000 times in a cross-sectional structure of a coating film obtained by baking a processing liquid composed of a colloidal silica solid content of 150 parts by weight at an ultimate plate temperature of 150 ° C. The coating was thicker than the claims of the present invention so that the film could be easily observed by electron microscope.

FIG. 2A shows the condition that the surface area of the colloidal silica particles occupied in the processing solution is about 13 times the surface area occupied by the emulsion resin particles, and the ratio of the surface area of silica is larger than the claims of the present invention. It is. The portion observed in a plate shape in FIG. 2A is an emulsion resin, and the periphery thereof is silica. As described above, when the ratio of the surface area of the silica to the surface area of the resin is increased, a structure in which resin particles are scattered in the silica layer is obtained. In the case of baking at a low temperature of 100 to 300 ° C., the film forming property of silica itself is weak and the bonding force between particles is small, so that protection against an external atmosphere cannot be expected. Therefore, it is considered that rust easily occurs in a humid environment.

On the other hand, FIG. 2B shows that the solid content of the emulsion resin and the colloidal silica is within the range of the present invention.
100: 150 parts by weight as in (a), but the ratio of the surface area of silica is 1.8 times the surface area of the resin particles. Under these conditions, it is considered that the resin and silica are finely dispersed, and the resin particles are bonded to each other during the baking process to form a protective and good corrosion-resistant coating. Such a change in the coating structure results in a structure in which silica particles are scattered in the resin layer when the proportion of the surface area of the resin in the treatment liquid is further increased, so that the corrosion resistance is not bad. As is clear from the experimental examples of the present invention, the ratio of the surface area of the silica particles that satisfies the corrosion resistance and the solvent resistance is 0.2 to 10 times, and the preferable range is 0.2 to 10 times or less, since the solvent resistance deteriorates when it is less than 2 times. It is 0.5 to 5 times.

In coating such a treatment liquid, the aqueous dispersion resin and the colloidal silica can be mixed by using a simple device such as a stirrer for a propeller blade. The mixed treatment liquid is applied to the surface of the magnetic steel sheet and baked to form a film.

The method for forming the insulating film is a roll coater, a flow coater, a spray coating,
Various methods such as a knife coater can be applied. The baking method is not particularly limited, such as a hot air method, an infrared method, and an induction heating method, which are usually performed. The baking temperature is slightly different depending on the resin composition.
It is preferable that the temperature be in the range of 250 ° C. If the temperature is lower than 100 ° C., the moisture in the coating may not be sufficiently dried. 250
C. or higher is not preferable because the resin is thermally degraded, and the color tone unevenness of the coating and the coating performance may be impaired. The adhesion amount of the insulating coating after drying is 0.1 to 2.
Set to 0 g / m ² . When the adhesion amount is less than 0.1 g / m ² , the seizure resistance and the punching property are not sufficient, and the adhesion is 2.0 g / m ^2.
Above is poor in weldability. The treatment liquid of the present invention may contain a rust preventive, a lubricant, a surfactant and the like in order to further improve the film performance.

[0021]

EXAMPLES The effects of the present invention will be specifically described with reference to examples and comparative examples. (Example 1) Sheet thickness 0.5 mm containing 0.2% Si
Ratio indicating the final finish alkaline type colloidal silica dispersion type water soluble epoxy resin and a specific surface area of 110m ² / g on the surface of the electrical steel sheet after annealing forced emulsion polymerization with specific surface area 330 m ² / g in Table 1 And then applied with a grooved roll. After that, reach plate temperature 200
Bake at ℃. The rolling reduction of the rubber roll was adjusted so that the coating weight per unit area was 0.5 g / m ² . Table 1 shows the quality test results. The various quality test conditions are as follows.

Adhesive product sheet (before annealing) and strain relief annealed sheet (at 750 ° C. in nitrogen)
× 2h annealing). An adhesive cellophane tape was stuck on the surface of the steel sheet, and after 180 ° bending-back test at 20 mmφ, the cellophane tape was peeled off and evaluated by a film peeling rate. ：: No peeling ：: ~ Peeling less than 20% 剥離: Peeling 20% ~ Peeling less than 40% ×: Peeling 40% ~ Peeling

The corrosion resistance (product plate) wet test (50 ° C., relative humidity 100%) was evaluated based on the red rust area ratio after 48 hours. ◎: 0 to less than 20% ：: less than 20 to 40% Δ: less than 40 to 60% ×: 60 to 100%

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

Baking strength by a tensile test: steel sheets after coating are overlapped with each other by 15 cm ² , and are subjected to 25 kg / cm ^2.
Then, after applying a load of 750 ° C. for 2 hours and drying with N ₂ , the film was evaluated for the fusion strength (kg / cm ² ) by a tensile test. If the strength is 1 kg / cm ² or less, there is no practical problem.

Solvent Resistance Various solvents (hexane, xylene, methanol, ethanol, acetone) were impregnated into absorbent cotton, and the appearance change of the steel sheet after 5 reciprocations was examined. ：: No change for all solvents ：: Change in appearance for any one solvent △: Change in appearance for multiple solvents ×: Large change Change in appearance for any solvent

A 15 mmφ steel die with a burr height of 50
Number of punches to reach μm. Weldability Welded under the following conditions and evaluated at the maximum welding speed at which blowholes did not occur. TIG welding method ◎: over 600 mm / min Electrode: Th-W 2.6 mmφ ○: 400 to 600 mm / min Pressing force: 100 kg / cm ² △: less than 300 to 400 mm / min Current: 120 A ×: less than 300 mm / min Shielding gas : Ar 6l / min

[0028]

[Table 1]

The content of the colloidal silica is 30 according to the present invention.
In the conditions of No. 1 and No. 2 which are less than parts by weight, the fusion strength between the coating films is high, and the seizure resistance after the strain relief annealing is not sufficient. In addition, since the resin was thermally decomposed after annealing, when the silica content was small, the corrosion resistance after annealing tended to deteriorate.
The ratio of the surface area of silica does not satisfy the range of the present invention.
Condition 3 is inferior in solvent resistance. If the silica content exceeds 400 parts by weight and 500 parts by weight, the adhesiveness and corrosion resistance of the coating are inferior.

Example 2 The same steel sheet as in Example 1 was treated with an aqueous dispersion resin and colloidal silica having different surface areas as shown in Table 2 and a silica solid content of 150 parts by weight with respect to a resin solid content of 100 parts by weight. The liquid has a dry adhesion of 0.3 g /
After coating with a grooved rubber roll so as to obtain m ² , baking was carried out in a hot-air stove so that the reached plate temperature became 100 ° C. Table 2 shows the quality test results.

[0031]

[Table 2]

The ratio of the surface area occupied by silica in the treatment liquid to the surface area of the aqueous dispersion resin (silica specific surface area × solid weight /
Sample No. 3 whose resin specific surface area × solid content weight does not satisfy the range of 0.2 to 10 of the present invention has poor solvent resistance,
o8 and No11 are inferior in adhesion and corrosion resistance. The examples of the present invention exhibited good solvent resistance despite the low baking temperature of 100 ° C.

Example 3 A 0.5 mm-thick SPCC material that had been subjected to final finish annealing and temper rolling in a continuous annealing line was compared with 100 parts by weight of an epoxy-acrylic copolymer emulsion resin having a specific surface area of 70 m ^2. A treatment liquid comprising 150 parts by weight of colloidal silica having a surface area of 90 m ² (silica / resin surface area ratio = 1.9) was used.
After coating with grooved rubber roll to be in the range of ^{g / m 2 ~3g / m 2} , was subjected to baking in a hot air oven to reach sheet temperature becomes 100 ° C.. Table 3 shows the quality test results.

[0034]

As compared with Sample No. 1, all of the inventive examples of Samples Nos. 2 to 6 show good seizure resistance and good adhesion and corrosion resistance. No. 7 applied with an excessive basis weight is corrosion resistance,
Although the seizure resistance was good, after annealing, a large amount of carbon due to the decomposition of the resin adhered to the surface of the coating film and adhered to the cellophane tape, resulting in poor adhesion. Also, when the amount of adhesion was large, the weldability was poor.

Example 4 The same steel sheet as in Example 3 was coated with the treatment liquid shown in Table 4 using a reverse roll. The dry basis weight is 0.3 g / m ² excluding 0.07 of line trouble.
０．６0.6 g / m ² . The baking was performed in a hot air drying furnace of a high-speed continuous furnace, and the reached plate temperature was controlled in the range of 130 to 150 ° C. The coils were tested for quality, including slitting punchability tests. Table 4 shows the results.

[0037]

[Table 3]

The punching properties of the coils No. 1 and No. 3 of the present invention are good punching properties of 1,000,000 times or more in the case of steel dies. However, coil No. 2 whose weight per unit area was extremely reduced due to line trouble and No. 4 where colloidal silica was excessively added were inferior in adhesion and corrosion resistance, and the punching property was greatly reduced. In addition, No. 2 having a small basis weight was firmly fused by strain relief annealing.

[0039]

As is apparent from the above description, a non-oriented electrical steel sheet having a coating applied with an organic-inorganic mixed treatment liquid composed of the aqueous dispersion resin and colloidal silica of the present invention can be manufactured by low-temperature baking. Further, the corrosion resistance, which has been a conventional defect, can be improved without impairing the conventional film performance.

[Brief description of the drawings]

FIG. 1 is a graph showing the corrosion resistance and solvent resistance of a product plate (before annealing) with respect to the ratio of the surface area of colloidal silica occupied in a treatment liquid to the surface area occupied by an aqueous dispersion resin.

FIG. 2 is a drawing substitute photograph showing the morphology of particles, in which a cross section of a coating film composed of an aqueous dispersion resin and colloidal silica is observed at a magnification of 30,000 times, and (a) shows a ratio of the surface area of silica. Non-conforming example with 13 times the surface area of resin particles,
(B) is a figure which shows the adaptation example whose ratio is 1.8 times.

Continuation of the front page (56) References JP-A-5-65663 (JP, A) JP-A-2-48941 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22 / 00-22/86 B05D 7/14

Claims (2)

(57) [Claims] 1. A surface area occupied by 30 to 300 parts by weight of colloidal silica solids per 100 parts by weight of resin solids and occupied by colloidal silica particles in a treatment solution [specific surface area m ² / g × Solid content] is 0.2 to 10 times the treating liquid of the organic-inorganic mixed composition with respect to the surface area [specific surface area m ² / g × solid content weight] occupied by the aqueous dispersion resin particles. 0.1 to ² per 1 m ^{2 of} unit area.
A non-oriented electrical steel sheet having an insulating coating excellent in punching properties and seizure resistance after annealing characterized by being coated at 0 g / m ² . 2. A method for forming an insulating coating on an electromagnetic steel sheet, comprising applying an organic-inorganic mixed composition containing an aqueous dispersion resin and colloidal silica as main components to the surface of a non-oriented electrical steel sheet. On the other hand, colloidal silica solid content 3
0 to 300 parts by weight, and the surface area occupied by the colloidal silica particles in the treatment liquid [specific surface area m ² / g
× solid weight] is 0.2 to 10 times the surface area [specific surface area m ² / g × solid weight] of the aqueous dispersion resin particles occupied by the treatment liquid of the organic-inorganic mixed composition. A method for forming an insulating film on a non-oriented electrical steel sheet having excellent punching properties and seizure resistance after annealing, characterized by applying 0.1 to 2.0 g / m ² per unit area of 1 m ² .