JPS59215421A - Method for forming film containing zirconia on surface of silicon steel sheet - Google Patents

Abstract

PURPOSE:To form an insulating film having an excellent magnetic characteristic on the surface of a silicon steel sheet by performing electrolysis with the silicon steel sheet as a cathode in an aq. soln. contg. a Zr complex compd. to deposit a Zr compd. and further coating MgO thereon and drying the same then annealing the steel sheet. CONSTITUTION:A silicon steel material contg. about 2-4% Si is made into an about 0.2-0.35mm. thick sheet by hot rolling-annealing of the hot rolled sheet- pickling-cold rolling and the sheet is subjected to decarburization annealing at about 200-300 deg.C then to drying. Such silicon steel sheet as a cathode is electrolyzed in an aq. soln. contg. a Zr complex compd. (for example, hexafluorozirconium ammonium) to deposit a Zr-contg. compd. on the surface of the silicon steel sheet. MgO is further coated thereon and is dried and thereafter the steel sheet is annealed to form an insulating film having an excellent magnetic characteristic thereon. Such silicon steel sheet is subjected to secondary recrystallization by high temp. annealing to about 1,200 deg.C in a gaseous mixture composed of H2 and H2 then the atmosphere is exchanged with 100% H2 atmosphere to remove impurities. The grain-oriented silicon steel sheet is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an insulating film with excellent magnetic properties on the surface of a silicon steel plate.

It is well known that applying tension to the surface of a magnetic steel sheet has favorable effects on magnetism, such as reducing iron loss and improving magnetic permeability. Conventionally, in order to prevent fusion during annealing of silicon steel sheets, powder or its suspension containing magnesia as a main component is applied to the surface of silicon steel sheets, and after drying, when annealing is performed by winding the sheets into coils, Concentrated silica (StO2) and magnesia (M
gO) and forsterei) (2Mg0.8
A stable ceramic film containing 10□) as the main component has been formed and has also been used as an insulating film.

The present invention uses zirconia (ZrO), which has a low expansion coefficient and a high melting point.
□), such as Z ro 2.810
A film containing □ etc. is formed by combining 5102 present on the surface of the silicon steel sheet with ZrO2 in the coating material during high temperature annealing, and when the temperature drops to room temperature or the operating temperature of the silicon steel sheet product. By applying tension to the surface of the silicon steel plate due to the difference in thermal expansion coefficient between the coating and the silicon steel plate,
This is intended to reduce the iron loss and improve the magnetic permeability of silicon steel sheets.

In order to combine zirconia with the silica component that is concentrated on the surface during the manufacturing process of silicon steel sheets and form an oxide layer containing zirconia with good adhesion, fine powder of highly reactive zirconia is added to the surface of the silicon steel sheet. It is necessary to apply it evenly and with good adhesion. Electrolytic deposition of an aqueous solution of a zirconium compound can be used as a method for forming active zirconia fine particles in close contact with the surface of a steel sheet, and fluoride can be used as a method of imparting activity to the reaction between zirconia and silica.

In order to efficiently form a film containing zirconia, we have applied a coating layer with a two-layer structure: a dense layer of zirconium compound as a lower layer close to the surface of the steel sheet, and an upper layer of magnesia, which is usually used to prevent steel sheets from adhesion. One way is to get more. In fact, when a complex compound of zirconium is dissolved in a suspension of magnesia and electrolyzed using a silicon steel plate as a cathode, a dense layer of zirconium hydroxide or oxide is formed at the bottom layer.
An adhesion layer having a two-layer structure with an adhesion layer of magnesia as an upper layer is obtained.

In the silicon steel sheet treated according to the present invention, the magnesia layer acts as a main role in preventing the copper strip from adhering during high-temperature annealing, making it possible to reduce the amount of expensive zirconium compounds used.

The zirconium compound used in the present invention is a complex compound of zirconium, such as zirconium ammonium hexafluoride, (
NH4)2zrF6, etc. When electrolysis is carried out in a solution containing a zirconium complex compound using a silicon steel plate as a cathode, a zirconium-containing compound is precipitated on the surface of the silicon steel plate, but this is mainly zirconium hydroxide with some oxides also present. When ZrF6 salt is used as a possible complex compound of zirconium, the effect of the trace amount of fluoride mixed in the precipitate in assisting the reaction between zirconia and silica is also observed.

Although magnesia (MgO) can be used alone, it is better to use a substance whose main component is magnesia and which contains a small amount of heat-resistant compounds such as conventionally known silica, alumina, boron oxide, calcium oxide, and titanium oxide. You can also do it.

The material used in the present invention is silicon steel having a size of 4 cm to 4 cm and other components. This steel ingot is hot-rolled, hot-rolled plate annealed, pickled, and cold-rolled according to the general manufacturing method to achieve a target thickness of 0.2~
Roll to 0.35 nm. Then, this silicon copper plate is decarburized and annealed using a mixed gas of N2 and N2 containing water vapor.

After decarburization annealing, the silicon steel plate treated according to the present invention has a
After drying at 300° C. to remove moisture, a coating layer containing a zirconium-containing compound is formed on the surface of the silicon steel sheet, and then wound into a coil. Next, the silicon steel plate is annealed at a high temperature of 1200'C in a mixed gas of N2 and N2 for secondary recrystallization.
The atmosphere is changed to 0.00 °C to remove impurities in the steel, resulting in a grain-oriented silicon steel sheet.

In practice, a ceramic film formed by high-temperature annealing of a silicon steel plate is often further subjected to phosphate treatment or chromate treatment to impart corrosion resistance.

Next, examples will be shown.

A silicon steel ingot containing 3.3% Si was cold-rolled to 0.29 tm by hot rolling, hot-rolled plate annealing, pickling, and cold rolling.
'I(2'''' 0-46, n2/+J2 = 3) Decarburization annealing was performed at 850°C x 150iec in an O decarburization atmosphere.

A zolconium compound is applied to the surface of this decarburized annealed plate using the following methods.

Example 1 In a (NH4)2Z rF 6101/11 aqueous solution, the above silicon steel plate was used as a cathode at a bath temperature of 30°C and 10 A/dm.
Electrolysis was carried out for 40 seconds under the conditions of ``.Then, while the surface was still wet, fine powder of Magnesia was further applied, and after drying, it was transferred to a high-temperature annealing process.

The amount of adhesion is zirconia 0.01 Vm2N magnesia approx. 5
It was fraud 2.

In addition, when some of the samples were dried after electrolysis and observed under an electron microscope, the presence of flat zirconia with a -side of about 5.about.10 .mu.m was observed.

Example 2 (NH4)2ZrF630 g/l N f Gunenya 1
o o Vll suspension at 40°C and 30 A/dm'' for 20 seconds to co-deposit the zirconium-containing compound and magnesia on the surface of the silicon steel plate, and remove the excess suspension with a roll squeeze. After drying, it was transferred to a high-temperature annealing process.The coating amount was 0.05 g/m2 of zirconia, -q Gnessa 39
Comparative Example As a comparative material, a Magnesia suspension containing no zirconium compound was applied to a silicon steel plate, and after drying, it was transferred to a high-temperature annealing process.The applied amount of Magnesia was 5Vm2.

The silicon steel plates coated with the annealing separators of each Example and Comparative Example were annealed at a high temperature of 1200° C. for 20 hours.

Thereafter, the silicon steel sheet that had been annealed at the high temperature described above was further subjected to chromate treatment, and its various properties are shown in the following table.

The film adhesion was 2oφ, iso', and did not peel off when folded, and the insulation resistance was more than 200 Qcm2/sheet, and there was no tendency for the Sisol Konya component to deteriorate the adhesion or insulation resistance.

Patent applicant Nippon Steel Corporation IC

Claims (3)

[Claims] (1) In an aqueous solution containing a zirconium complex,
The silicon steel plate contains zirconia on the surface, characterized by performing electrolysis using the silicon steel plate as a cathode to precipitate a zirconium-containing compound on the surface of the silicon steel plate, further applying magnesia thereon, and after drying, annealing the silicon steel plate. Method of forming a film. (2) Electrolysis is performed using a silicon steel plate as a cathode in a magnesia suspension containing a zirconium complex compound, and a zirconium-containing compound and magnesia are eutectoided on the surface of the silicon steel plate. After drying, the silicon steel plate is annealed. A method of forming a film containing zirconia on the surface of a silicon steel plate. (3) Z rF 6 as a zirconium complex compound
Claim (1) or (2) using salt
A method for forming a film containing zirconia on the surface of a silicon steel plate as described in 1.