JPH02209466A - Production of grain-oriented silicon sheet reduced in iron loss - Google Patents

Abstract

PURPOSE:To obtain, extremely effectively, a grain-oriented silicon steel sheet of low iron loss excellent in adhesive strength of film and shape of steel sheet by dividing the process for forming a ceramic film on a finish-annealed grain- oriented silicon steel sheet by means of ion plating treatment into multistages and controlling treating conditions in respective stages. CONSTITUTION:After oxides are removed from the surface of the above grain- oriented silicon steel sheet by means of acid pickling, the surface of this steel sheet is finished to <=0.4mum center line average height Ra. subsequently, a ceramic film is formed on the above steel sheet surface after the above finishing by means of continuous ion plating by dividing the process of this ion plating treatment into multiple stages, and in the initial stages, coating temp. and bias voltage are set at high values, respectively, and vapor deposition rate is reduced to form a film firmly adhering to the steel sheet, and on the other hand, coating is carried out in large quantities in the latter stages, by setting coating temp. and bias voltage at low values, respectively, and increasing vapor deposition rate. As a result, the ceramic film excellent in adhesive strength and film quality can be effectively formed in a relatively short time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a low core loss unidirectional silicon steel sheet, and in particular, the present invention relates to a method for producing a low iron loss unidirectional silicon steel sheet, and in particular, a method for producing a unidirectional silicon steel sheet with a dense structure on the surface of the steel sheet without the disadvantage of deteriorating the shape of the steel sheet. The aim is to form a ceramic coating with a high quality.

(Prior Art) Recently, the inventors have removed surface oxides from a finish-annealed unidirectional silicon steel sheet, and then subjected it to a polishing treatment.
We developed an iron loss reduction technology that consists of forming a thin tension film of nitride or carbide on this polished surface by PVD or CVD treatment (for example, Japanese Patent Publication No. 63-3284
No. 9, No. 63-32850, No. 63-35684,
Publications No. 63-35685, No. 63-35686, and No. 63-3285).

Among the above-mentioned film forming methods, the PVD method is particularly suitable for manufacturing a unidirectional silicon steel sheet with low core loss because it can form a film at a higher speed and at a lower temperature than the CVD method. Among them, HCD (I(ollow cathod)
The eDischarge method is said to be most suitable for manufacturing such silicon steel sheets because it produces a dense and smooth ceramic and can form a film at a relatively high speed.

However, when a ceramic coating is applied to a silicon steel plate, especially a thin silicon steel plate, which is the material to be treated, by the above method, there is a disadvantage that the shape of the steel plate deteriorates due to local distortion due to local expansion or contraction. Ta.

(Problems to be Solved by the Invention) However, to date, there has been no ion plating method that has excellent magnetic properties and film adhesion and does not damage the shape of the steel sheet, and its development has been desired.

An object of the present invention is to propose an advantageous method for producing a low core loss unidirectional silicon steel sheet using a novel ion plating method that can advantageously meet the above requirements.

(Means for Solving the Problems) The inventors have conducted extensive research to solve the above problems and have found that a ceramic coating is applied to the surface of a unidirectional silicon steel sheet by finish annealing by ion plating. Needless to say, by dividing the ion plating process into multiple stages and controlling the processing conditions at each stage, especially the coating temperature, bias voltage, and vapor deposition rate, excellent film adhesion can be achieved extremely effectively. We have obtained the knowledge that a unidirectional silicon steel sheet with excellent steel sheet shape and therefore excellent magnetic properties can be obtained.

This invention is based on the above knowledge.

That is, this invention involves removing surface oxides from a unidirectional silicon steel plate that has undergone finish annealing, and then polishing the steel plate surface to a mirror finish with a centerline average roughness Ra of 0.4 μm or less, and then applying HCD. In the method for producing unidirectional raw steel sheets coated with a ceramic coating by continuous air-to-air ion plating, the above ion plating treatment is carried out in multiple stages. The coating temperature and bias voltage are set high and the evaporation rate is low to ensure adhesion to the steel plate, while in the latter stage the coating temperature and bias voltage are set low and the deposition rate is set low to achieve coating using the above method. This is a method for manufacturing a low core loss unidirectional silicon steel sheet.

Below, the experimental results that led to this invention will be explained.

C: 0.043wtχ (hereinafter simply expressed as %), Si
:3.44%Mn:0.072%, Se:0.021
A silicon steel slab having a composition containing 0.025% and 0.012% Sb was heated at 1350 °C to 4
After heating for a period of time, hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.2 mm. Then, cold rolling was performed twice with intermediate annealing at 950° C. to obtain a final cold rolled sheet having a thickness of 0.20 mm. then 8
After primary recrystallization annealing that also serves as decarburization in wet hydrogen at 20°C, 65% A1zOs and 30% -M were deposited on the surface of the steel plate.
After applying an annealing separator having a gO+ 5%-ZrOz composition, secondary recrystallization annealing was performed at 850°C for 150 hours, and then 1200°C in soft hydrogen. Purification annealing was performed for 8 hours.

Next, oxides on the surface of the silicon steel sheet were removed by pickling, and then electrolytically polished to a center line average roughness Ra of 0.2μ.
Finished with a mirror finish of m.

Next, Ti was applied to the mirror-finished surface using the air-to-air continuous ion plating device shown in Figure 1.
A ceramic coating of N was formed to a thickness of 1 μm. In the figure, number 1 is the coil, 1' is the coil after coating, 2 is the shear, and 3 is the differential pressure chamber.
are the inlet differential pressure chambers 3-1 to 3-8 and the outlet differential pressure chambers 3-9 to 3-.
It consists of 16.

4-1 and 4-2 are preheating devices for the front and back surfaces of the steel plate, respectively;
5-1 to 5-8 are all hot rollers. 6 is a first vapor deposition chamber, 6-1 is a vapor deposition source, 6-2 is a crucible,
6-3 is a raw material supply device, 6-4 is a reaction gas, and 6-5 is a guide roller. The same <7.8.9 are the second. Third. This is the fourth vapor deposition chamber, where 7-1.8-L9-1 is a vapor deposition source, 7-2.8-2.9-2 is a crucible, and 7-3°8
-3.9-3 is rod feeder, 7-4.8-4.9-4
is a reaction gas, and 7-5.8-5.9-5 is a guide roller.

Note that 10-1 and 10-2 are roller valves, respectively.

Now, in the above-mentioned continuous ion plating apparatus, the silicon steel strip knob, which is the material to be treated, is introduced into the interior from the entrance differential pressure chamber, and this entrance differential pressure chamber is divided into multiple chambers. The degree of vacuum gradually increases toward the inside, and in the differential pressure chamber 3-8, IXl0-
It is about ' Torr.

The strip is then further vacuumed (5X 10-6To
The steel sheet is introduced into the preheating device 4, which is maintained at a temperature of about 100 mm (approx. Next, Part 1.2
．． While sequentially passing through deposition chambers 3 and 4, ceramic coatings are formed on the front and back surfaces of the strip in the order of the first layer on the front, the first layer on the back, the second layer on the front, and the second layer on the back. .

The results of investigating the shape and magnetic properties of the steel sheet when TiN was coated to a thickness of 1 μm (line speed 10 m/min) using the above continuous ion plating equipment under the various coating conditions shown in Table 1 are as follows. , are also listed in Table 1.

As is clear from the table, the steel plate temperature and bias voltage are high and the evaporation rate is low for the first layer on both the front and back surfaces, while for the second layer, on the contrary, the steel plate temperature and bias voltage are low and the evaporation rate is high. By doing so, a silicon steel plate with excellent magnetic properties and a good plate shape has been obtained.

(Function) According to the present invention, the ion plating process is divided into multiple stages, and in the initial stage, the coating temperature is set high and the bias voltage is set high, and the deposition rate is low, so that a film that firmly adheres to the steel plate is formed. On the other hand, in the later stages, the coating temperature is set low, the bias voltage is set low, and the deposition rate is increased to apply a large amount of coating, thereby creating a ceramic coating with excellent adhesion and film quality in a relatively short period of time. This means that it can be effectively deposited without the disadvantage of deterioration of the plate shape.

In this invention, it is preferable that the coating temperature and bias voltage in the initial stage of ion plating treatment are approximately 300-500°C and 50-150V, respectively, and the deposition rate is approximately 0.5-2.5 μm/min. . On the other hand, the coating temperature and bias voltage in the subsequent ion plating treatment are preferably about 200 to 400°C and about 10 to 50 V, respectively, and the deposition rate is preferably about 2.0 to 8.0 μm/min. Note that the ion plating film thickness at the initial stage is preferably about 30% or less of the total film thickness.

Furthermore, it goes without saying that the ion plating method according to the present invention can be applied not only to metal strips but also to cut plates.

(Example) C: 0.043%, Si: 3.39%, Mn: 0.
072%, Se: 0.021%, Mo: 0.013
% and Sb: A hot-rolled silicon steel sheet having a composition containing 0.025% was made into a final cold-rolled sheet with a thickness of 0.20 mm by a two-step cold rolling method, and then decarburized and primary recrystallization annealed. Then, after performing secondary recrystallization annealing and purification annealing, surface oxides were removed by pickling, and the surface of the steel plate was Rized by electrolytic polishing.
It was finished in a mirror-like state with a thickness of 0.8 μm or less.

After that, the HCD type air-to-air system shown in Figure 1 above was installed.
Using an air continuous ion plating device, the TjN film was deposited at a thickness of 0.8 μm at a threading speed of 12 m/min.
It was coated to a thickness of m. The coating conditions at this time were as follows.

j) First layer hot roller temperature: 420°C Bias voltage: 60v HCD conditions: 1000 A, 70 Vii) Second
Layer hot roller temperature: 300°C Bias voltage = 15V HCD conditions: 1500 A, 80 V The magnetic properties of the product board thus obtained are B+o: 1.92 T, WIT/S: 0
．． 75 W/kg, and the plate shape was also very good.

(Effects of the Invention) Thus, according to the present invention, a ceramic coating with excellent adhesion and film quality can be formed on the surface of a silicon steel plate without damaging the plate shape, and therefore has excellent magnetic properties and shape quality. A unidirectional silicon steel sheet can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an HCD type air-to-air continuous ion plating apparatus suitable for use in carrying out the present invention. 1... Coil 1'... Coil after coating 2... Shear 3... Differential pressure chamber 4... Preheating device 5... Hot rollers 6.7, 8.9... Vapor deposition Chamber 10...Roller valve

Claims (1)

[Claims] 1. Surface oxides are removed from a unidirectional silicon steel plate that has undergone finish annealing, and the steel plate surface is then polished to a mirror finish with a centerline average roughness Ra of 0.4 μm or less. Later, in a method for manufacturing grain-oriented silicon steel sheets coated with a ceramic coating by air-to-air continuous ion plating using the HCD method, the above ion plating treatment was performed in multiple stages. In the initial stage, the coating temperature and bias voltage are set high and the evaporation rate is low to ensure adhesion to the steel plate, while in the latter stage the coating temperature and bias voltage are set low and the deposition rate is set low to achieve the above-mentioned properties. A method for producing a low iron loss unidirectional silicon steel sheet, which is characterized by coating according to a method.