KR100384452B1 - Composition for forming non-grain oriented magnetic strip insulating coating film and method for forming insulating coating film using the same - Google Patents

Abstract

PURPOSE: A treatment solution for an insulating coating film is provided to improve coating stability and corrosion resistance by properly controlling constituent and content of treatment solution for forming the film and properly controlling manufacturing conditions of the film, and a method for forming the film using the same is provided. CONSTITUTION: The composition for forming a non-grain oriented magnetic strip insulating coating film is characterized in that the composition is an organic and inorganic material mixed solution obtained by dissolving principal constituents of 30 to 92 g/L of sodium phosphate, 2.2 to 6.1 g/L of cobalt blue, 3.8 to 15.3 g/L of mica powder, silica powder or a mixture thereof, and 104 to 138 g/L of acid soluble type silicone resin solid into water. The method for forming a non-grain oriented magnetic strip insulating coating film comprises the steps of coating an organic and inorganic material mixed solution obtained by dissolving principal constituents of 30 to 92 g/L of sodium phosphate, 2.2 to 6.1 g/L of cobalt blue, 3.8 to 15.3 g/L of mica powder, silica powder or a mixture thereof, and 104 to 138 g/L of acid soluble type silicone resin solid into water on the surface of a non-grain oriented magnetic strip so that dried coating film has thickness of 1.0 to 4.5 μm per one side of the strip; and annealing the solution coated non-grain oriented magnetic strip in an electric furnace at 400 to 750 deg.C for 12 to 65 seconds.

Description

Coating composition for forming non-oriented electrical steel sheet insulation film and method for forming insulation film using same

The present invention relates to a treatment liquid used for forming an insulating coating of a non-oriented electrical steel sheet, that is, a coating composition and a method for forming an insulating coating using the same. In particular, the components and contents of inorganic and organic insulating coating forming treatment liquids are appropriately adjusted. By appropriately controlling the manufacturing conditions of the insulating film according to this purpose is to form an insulating coating treatment solution excellent in coating stability and corrosion resistance and the insulating film using the same.

In general, non-oriented electrical steel sheets used as iron cores for electric appliances such as small electric motors and transformers form an insulating film on their surfaces to suppress eddy currents and reduce power loss. These insulating coatings are classified into three types of organic, inorganic and organic inorganic mixtures according to the demands of various usage characteristics, and the coating is completed by supplying the treatment liquid to the surface of the electrical steel sheet and applying and drying.

However, in the production line of the actual production line, the inorganic insulating film that meets the demand of A demand is formed in a continuous coil, and then organic and inorganic mixtures that meet the demand of B again. Insulation coating should be formed, etc. During the formation of insulation coating, it should be used at any time according to the demand of the insulation coating treatment solution. Therefore, when the treatment solutions are mixed with each other, the film forming operation can be easily performed without losing its characteristics. In order to be achieved, a property that the mixing solution compatibility and continuous coating workability (hereinafter, referred to as "coating stability") must be excellent between each other.

In other words, pure inorganic and organic / inorganic mixed systems are mainly used for the insulation coating of non-oriented electrical steel sheet products produced on-site, and it is difficult to perform long-term stable coating work on the surface of electrical steel due to poor mixing stability between them. It is true.

Therefore, when the coating liquid is used in replacement, a separate operation of artificially removing the pre-coating agent is required, which causes a decrease in the product yield, and thus an urgent improvement is required.

In addition, the coil condition and the product is continuously punched out to a predetermined shape by a mold at a demand price, and then stress relief annealing is usually performed. The corrosion resistance is excellent because it is exposed to the atmosphere from the shipment of the product to the stress relief heat treatment. It is essential to do

However, in order to impart the required characteristics of the coating such as corrosion resistance, chromic acid is usually contained as a medicament of the insulation coating treatment agent. It is required to exclude the use of the insulation coating liquid from the beginning of the production of the insulating coating because it may cause environmental problems when the wastewater is discharged, and shorten the life due to abnormal wear of the mold during punching due to residual chromium hexavalent.

As a technology for forming an insulating film of a conventional non-oriented electrical steel sheet, the present invention is Korean Patent No. 25106 (notification 87-2105), 31208 (notation 89-3582), 31219 ( It has been proposed a method for forming an electrical insulating film of non-oriented electrical steel sheet of the Nos. 89-3583) and 43342 (Notifications 91-2724).

However, Korean Patent No. 43342 (Notification No. 91-2724), which is a method of forming inorganic insulating coating, and Korean Patent Nos. 25106 (No. 87-2105), No. 31208, which is a method of forming an organic / inorganic mixed insulating coating. 89-3582) and 31219 (Notice No. 89-3583) both satisfy certain general characteristics such as insulation, heat resistance, etc., but the application of coating stability, that is, after stopping the coating equipment, When the coating treatment liquid is used immediately afterwards, the first treatment liquid and the next treatment liquid are mixed with each other. In this case, the problem that the characteristics of the treatment solution are lost due to the rapid chemical reaction between the inorganic and the inorganic / organic mixed treatment solution is improved. There is no mention of the content, and they all use chromium, and there is no description of any restrictions on use.

The present invention has been made to solve the above problems in consideration of the above problems, and because it properly adjusts the components and contents of the silicone resin and inorganic treatment liquid of the newly soluble type and appropriately controls the manufacturing conditions of the insulating film accordingly, An object of the present invention is to provide an insulating film forming solution having excellent use characteristics such as coating stability and corrosion resistance at the demand side, and a method of manufacturing the insulating film using the same, which can be stably operated by a steel sheet manufacturing company.

A feature of the present invention having such a purpose is that acid (phosphate, chromic acid) solubility is used instead of acrylic resin which is an insoluble type of organic resin-based insulating coating liquid which has been conventionally used as an insulating coating liquid for non-oriented electrical steel sheet. By using a silicone resin of the type, it is possible to provide a new method of forming an insulating film, which exhibits a noticeable effect of coating stability and corrosion resistance between inorganic, inorganic and organic insulating films than the conventional method of forming an insulating film.

The present invention is a silicone resin (in solid content) of sodium phosphate 30 to 92 gr / L, cobalt blue 2.2 to 6.1 gT / L mica powder or silica powder of 3.8 to 15.3 gr / L and acid-soluble type leaves. Insulating coating liquid dissolved / suspended in water with / L as the main component was applied to the surface of non-oriented electrical steel sheet, and then heated for 12 to 65 seconds in an electric furnace maintained at a temperature range of 400 ° C to 750 ° C to a thickness of 1.0 to The film was formed so as to be in the range of 4.5 µm / single side.

Hereinafter, the role of each component and the reason for limitation of the added value are demonstrated.

If it is 30 gr / L or less of sodium phosphate added in order to provide corrosion resistance in a film, it is inadequate and it is effective to set it as 9.2 gr / L.

Cobalt blue (particle size: 0.5㎛) added to give a beautiful color with blue color appears to be grayish white like the small support plate at 2.2gr / L or less, thus avoiding the user from demand. If it is a factor, the addition effect is insufficient, and if it is 6.1 gr / L or more, it is difficult to make a uniform treatment for the layer separation phenomenon, and the appearance of the film becomes poor, so the appropriate range is preferably 2.2 to 6.1 gr / L. Do.

In case of adding one or two kinds of ultra fine metal oxide silica powder and mica powder added to the film to improve the electrical insulation property, the effect of improving the insulation is insufficient. 15.3 When more than gr / L is added, 3.8 to 15.3 gr / L is appropriately added, since the insulation stability becomes uneven after the coating treatment due to poor solution stability due to precipitation of silica added within 1 day after blending.

In the present invention, the powdery silica and mica may use ultra-fine mica that is used as a general electrical steel sheet insulation coating agent, and the particle size thereof is not particularly limited.

When the acid-soluble type silicone resin which improves the adhesiveness to the material and gives flexibility to the film is added to 104gr / L or less as a resin solid content, the appearance of uneven appearance and insufficient film adhesion, and when added more than 138gr / L It is preferable to limit to 104 to 138 gr / L because the problem that the formation rate of the film is slowed down causes no practical use.

In the present invention, after applying the treatment liquid for forming an insulating film configured as described above with a synthetic rubber roll on the surface of the non-oriented electrical steel sheet so that the dry film thickness is in the range of 1.0 to 4.5㎛ per one side, it is a temperature range of 400 ℃ to 850 ℃ It is preferable to anneal for 12 to 65 seconds at the following reasons.

If the furnace temperature is maintained below 400 ℃, annealing is insufficient, and the hygroscopicity or film formation is required for a long time, and in fact, in industrial use, low productivity disturbance problem occurs, when the furnace temperature is above 750 ℃ annealing temperature It is preferable to limit the temperature range of the annealing temperature of 400 ° C. to 750 ° C. because the control becomes difficult and the surface quality defects tend to occur.

On the other hand, when the annealing time is shorter than 12 seconds, the water resistance and hygroscopicity are low due to undrying. When the annealing time is 65 seconds or more, the annealing time is preferably limited to 12 to 65 seconds because there is a problem of deterioration of product productivity. .

Even if the film is formed by satisfying the annealing condition after roll application, the required insulation and corrosion resistance cannot be obtained when the thickness of the dry film by the method of the present invention is 1.0 μm or less, and when the thickness is 4.6 μm or more, the stress is removed. Problems such as deterioration of powder powder and welding characteristics after annealing have arisen, so that the dry film thickness is preferably limited to a range of 1.0 to 4.5 µm per side.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

After 7 days of blending the insulating coating liquid having the composition as shown in Table 1, using a synthetic rubber roll, the coating was applied to the surface of the non-oriented electrical steel sheet (containing S: 0.4%, the thickness of the plate 0.5mm), and then subjected to heating annealing. The insulating film was formed, respectively.

Among the coating compositions, Comparative Example 6 was not included in the coating property test due to poor coating condition due to undrying (floating on the hand), and Comparative Example 7 due to loss of coating workability due to gelation phenomenon immediately.

Table 1.

The film properties of the electrical insulating film formed as described above were measured, and the measurement results are shown in Table 2 below.

Table 2.

In Table 2, the stress relief annealing was heat-treated at 750 ° C. × 2 hours in a dry 100% N ₂ gas atmosphere, but the insulation (Amps.) Was stored at a current of 0.5 V and 1.0 A (amps) at 300PSI input. It is expressed as a current value and the adhesion (mm ) Annealing the specimen 10, 20, 30-100mm It shows the minimum arc diameter without film peeling when bent 180 ° in contact with phosphorus arc. The appearance of the film before stress relief annealing is shown by visually confirming the color and appearance, and the surface color is due to the presence of cobalt blue component in the forming film. When it appears blue and beautiful, it is good, and the surface color is almost grayed out like the small support plate, and when the color that becomes a user's evasion factor appears in demand, it is considered bad.

The appearance is glossy and satisfactory when no stripe shape is seen. Corrosion resistance was visually observed for rust on the surface after 8 hours of salt spray test (5% NaCl, 35 ℃).

The appearance of the film after the stress relief annealing was also visually confirmed, and it is preferable that there is no peeling phenomenon without losing gloss even if the color is changed by the stress relief annealing treatment.

The results of the present invention are summarized based on Table 1 and Table 2 as follows. Inventive examples a and b obtained by annealing an inorganic steel composition composed of at least one of sodium phosphate, cobalt blue, powdered mica, or silica powder with an acid-soluble silicone resin as a main component under appropriate treatment conditions It can be seen that the use properties required for coating such as corrosion resistance, insulation and appearance are superior to those in the case where the coating composition is inadequately added (Comparative Examples 1, 2, 3) or improperly treated (Comparative Example 4). have.

As shown in Comparative Example 7 of Table 1, the gelation phenomenon occurs immediately when the conventional inorganic insulating coating liquid and the conventional organic and inorganic mixed coating liquid are mixed, and the characteristics of the coating treatment liquid are lost. Is described above. However, using the silicone resin of the present invention, which is soluble in acid in Comparative Example 5, the inorganic components and the gelling phenomenon in the conventional inorganic coating solution do not appear at all, and when the work of changing the type of treatment agent is performed, the operation such as washing of the cotalol is performed. It can be seen that it is advantageous in terms of productivity improvement since the continuous coating operation can be omitted.

In this way, the coating agent by the new composition shows good usability with the conventional inorganic coating liquid, so that the compatibility of the line can be maintained without congestion of the line, so that the productivity can be maximized as a quick work place in the field, and the uniqueness of the coating is also practical. Although it was found that a new type of organic and inorganic mixed coating that can achieve the effect of the conventional inorganic insulating coating will contain chromium, the composition system containing the chromium-containing component is excluded from the scope of the present invention.

In the present invention as described above, by using a mixed coating liquid having a main component of adding an acid-soluble type silicone resin to an inorganic composition consisting of one or two kinds of sodium phosphate, cobalt blue and powdered mica and silica powder, When the conventional pure inorganic insulating coating liquid and the conventional organic and inorganic mixed coating liquid are used interchangeably, the coating stability improvement effect and the corrosion resistance effect due to the omission of the washing operation of the coating apparatus required before replacement are beneficial. It is effective to form an insulating film on the surface of the non-oriented electrical steel sheet that can also satisfy general requirements such as heat resistance.

Claims (2)

Sodium phosphate 30 to 92 gr / L, cobalt blue 2.2 to 6.1 gr / L, mica powder or silica powder 3.8 to 15.3 gr / L and acid soluble type silicone resin (in solid) 104 to 138 gr / L A coating composition for forming a non-oriented electrical steel sheet insulation coating, characterized by a mixed organic and inorganic coating liquid dissolved and suspended in water as the main component. Sodium phosphate 30-92gr / L, cobalt blue 2.2-6.1gr / L, mica powder or silica powder 3.8-15.3gr / L and acid-soluble silicone resin (solid content) on the surface of non-oriented electrical steel sheet An organic and inorganic mixed coating solution dissolved and suspended in water using 104 to 138 gr / L as a main ingredient is applied so that the dry film thickness is 1.0 to 4.5 µm per side, and is maintained at a temperature of 400 to 750 ° C. A non-oriented electrical steel sheet insulating film forming method characterized in that the annealing for 12 to 65 seconds.