JPH0347957A - Production of grain-oriented silicon steel sheet reduced in iron loss - Google Patents

Abstract

PURPOSE:To remarkably reduce iron loss with high productivity by forming a silicide film on the smoothed surface of a silicon steel sheet after finish annealing by a low-temp. plasma spraying method. CONSTITUTION:A forsterite film is removed from a grain-oriented silicon steel sheet after finish annealing, by which the surface of a matrix is smoothed. Subsequently, a silicide powder is thermally sprayed on the above surface by a low-temp. plasma spraying method, by which a silicide film is formed. Further, if necessary, a tension-giving film is applied to the above, followed by baking. By this method, the grain-oriented silicon steel sheet having extremely low iron loss value can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a grain-oriented silicon steel sheet having an extremely low core loss value.

(Prior Art) Unidirectional silicon steel sheets are often used as magnetic cores, and are required to reduce iron loss in order to reduce energy loss. Therefore, as a means to reduce the iron loss of unidirectional silicon steel sheets, a laser beam is irradiated onto the material surface after final annealing to give local strain, thereby subdividing the magnetic domains and lowering the iron loss. For example, the method is disclosed in Japanese Patent Application Laid-Open No. 58-26405.
It is disclosed in the publication No. In addition, as a magnetic domain refining means in which the magnetic domain refining effect does not disappear even if strain relief annealing is applied after processing a unidirectional silicon steel plate into an iron core, for example, Japanese Patent Application Laid-Open No. 62-861.75 There is a method disclosed in the official gazette. These technical measures can reduce the iron loss value of unidirectional silicon steel sheets, but when attempting to further reduce the iron loss value, it is necessary to remove the glass film present on the material surface after final annealing. It is important to remove irregularities on the surface of the steel plate that inhibit the movement of magnetic domains near the surface of the steel plate. As a means for this purpose, there is a method of mirror-finishing the bare surface of the material after finish annealing, or applying metal plating to the mirror-finished material surface. Furthermore,
Japanese Patent Publication No. 5224499 proposes a method of obtaining a unidirectional silicon steel sheet with ultra-low core loss by coating and baking an insulating film on the surface of the mirror-finished and metal-plated material. Furthermore, for example, JP-A-61-2017
No. 32 discloses that a unidirectional silicon steel plate finished in a mirror-like state with an average surface roughness of 0.4 μm or less is heated at 500 to 1000° in an atmosphere consisting of a Ti-containing gas and a non-oxidizing gas.
Heat treated in the temperature range of C, with TiN, TiC, T on the surface.
A method is disclosed in which a unidirectional silicon steel sheet with a low core loss value is obtained by forming an ultra-thin tensile film made of i(C,N) and further covering it with an insulating film.

(Problem to be solved by the invention) The base surface of the unidirectional silicon steel plate is mirror-finished, CVD,
Recently, many proposals have been made to form a film by means such as PVD or ion blating. Although these methods have some effectiveness, 10-5T
It requires a vacuum of less than orr or more and takes a long time to form a thick film, resulting in extremely low productivity and high cost.

The present invention has been made with the object of solving these problems in the prior art and providing a manufacturing process that can industrially produce unidirectional silicon steel sheets with extremely low iron loss values at low cost.

(Means for solving problems) The gist of the present invention is as follows.

(1) A method for producing a low core loss unidirectional silicon steel sheet, which comprises forming a silicide film on the surface of the unidirectional silicon steel sheet after final annealing by low-pressure plasma spraying.

(2) A low iron loss unidirectional silicon steel plate characterized in that a silicide film is formed on the surface of the unidirectional silicon steel plate after finish annealing by low-pressure plasma spraying, and a tension imparting film is further applied and baked. manufacturing method.

The present invention will be explained in detail below.

In order to solve the problems in the prior art described above, the inventors considered forming a silicide film on the surface of a unidirectional silicon steel plate by a low-pressure plasma spraying method. In conventional low-pressure plasma spraying, the particle size of the sprayed silicide is as large as 50 to 100 .mu.m, so the silicide film formed is extremely thick, 100 .mu.m or more. The inventors reduced the particle size of the silicide to 12 μm or less and set the temperature of the substrate to 400°C.
It has been found that by doing the above, it is possible to form a film of 12 μm or less with extremely good adhesion in a short period of time. The particle size of the sprayed silicide used in the low-pressure plasma spraying of the present invention is 1 to 33 μm, preferably 1 to 22 μm. When coarse particles with a particle size exceeding 33 pm are used, it becomes difficult to form a dense film with excellent adhesion. On the other hand, the particle size is 1μ
If the particle size is less than m, the particle feeding becomes unstable and thermal spraying becomes difficult. The present invention is characterized in that the particle size of the thermally sprayed silicide is 1 to 33 mm, and the temperature of the substrate to be thermally sprayed is 400°C or higher.With these thermal spraying conditions, extremely high adhesion can be achieved in a short period of time. A film with a thickness of 12 μm or less with excellent properties can be formed.

A unidirectional silicon steel sheet having a film formed in this manner has extremely excellent magnetic properties.

The means for forming a silicide film using the low-pressure plasma spraying method according to the present invention is applied to remove the glass film on the surface of the material after final annealing, smooth the surface of the steel base, and form a silicide film on the surface. be able to. Moreover, this method can of course be applied to a process in which a unidirectional silicon steel plate is subjected to secondary recrystallization while a strip is running, and then a coating is applied. In addition, the special public service 63-448
It is used in combination with the magnetic domain control technology disclosed in Japanese Patent Publication No. 04 and Japanese Patent Publication No. 63-6611, in which the magnetic domain refining effect does not disappear even when a grain-oriented silicon steel plate is processed into an iron core and then subjected to strain relief annealing. You can also do that.

The present invention will be explained in more detail below.

A steel slab containing 4 wt% or less of Si is heated and hot-rolled into a hot-rolled plate, annealed at this stage if necessary, and then cooled once or twice with intermediate annealing. After rolling to achieve the final thickness, decarburization annealing is applied, and an annealing separator is applied to form a strip coil.Final annealing is then performed at high temperature for a long time to produce secondary recrystallized grains with <001> orientation. The developed forsterite film of the steel plate is removed chemically or mechanically, or the annealing separator is used with a material that does not form a forsterite film, such as alumina, to expose the base iron on the surface of the steel plate after finish annealing. After smoothing the surface of the base metal by immersion in a solution containing hydrofluoric acid and hydrogen peroxide or by electrolytic polishing, a silicide film is formed in a low-pressure plasma spraying device.

An example of low pressure plasma spraying conditions used in carrying out the present invention is shown below.

Working gas: Ar Human power: 87KW Thermal spraying atmosphere pressure 30Torr Spraying distance 1iiIG +480mm powder supply speed
: 46 g/min.

Note that the present invention is not limited to the above thermal spraying conditions.

Figure 1 shows the relationship between the average particle diameter of molybdenum disilicide and the spray thickness when molybdenum disilicide (MoSiz) is used as the spray powder and the substrate is passed through the plasma jet at a speed of 85 mm/sec under the above spray conditions. It is something that As can be seen from this figure, the smaller the particle size of the sprayed silicide (molten powder), the thinner the coating can be formed in the same thermal spraying time.

Next, FIG. 2 shows the results of investigating the temperature of the silicon steel plate (substrate) during thermal spraying and the adhesion of the thermal sprayed coating after thermal spraying. As is clear from FIG. 2, as the temperature of the substrate is gradually raised from room temperature, the adhesion of the sprayed coating improves. This is thought to be due to the fact that by keeping the temperature of the substrate high during thermal spraying, the wettability between the melted thermal spray material droplets and the substrate is improved and diffusion occurs.

The adhesion of the thermal sprayed coating was evaluated by the peeling rate of the thermal sprayed coating when the silicon steel plate after thermal spraying was wound around a 30 mmφ round bar. As is clear from FIG. 2, when the temperature of the substrate is 400° C. or higher, the adhesion of the sprayed coating becomes better (the peeling rate decreases). The powders used for thermal spraying are titanium (Ti) and zirconium (Z), which exhibit adhesion comparable to that of ordinary forsterite films at substrate temperatures of 400°C or higher.
r), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (
Disilicides such as W) or mixtures thereof, as well as compounds with different silicon bonding ratios (for example, Mo5Si
Either of s) may be used, but when considering improving the iron loss of the product, it is better to use a silicide that has a large difference in thermal expansion coefficient from the underlying silicon steel plate (base iron).

After forming the silicide film, it is better to heat the base to about 800°C to relax the strain between the base and the silicide film, which will improve iron loss. When a tension coating is applied to a steel plate and baked after the silicide coating is formed, the baking is done at a temperature of 800° C. or higher, so that the strain on the base and the silicide coating is relaxed. Even when strain relief annealing is performed in a temperature range of 800° C. or higher after processing the product into a wound iron core or the like, the strain on the base and the silicide film is also relaxed.

(Example) Example I A finish annealed high magnetic flux density unidirectional silicon steel plate containing 3.2% Si and having a thickness of 0.2 mm was immersed in a mixture of sulfuric acid and hydrofluoric acid to form a Forsterei I film. After removing the steel plate, the steel plate is introduced into a low-pressure plasma spraying device and the substrate temperature is increased to 500°.
As C, molybdenum disilicide having an average particle size of 6 to 12 μm was thermally sprayed to form a silicide film with a thickness of 10 μm. after that,
The strain was relaxed by heating to 800°C in an inert gas atmosphere. Table 1 shows the iron loss values of the products thus obtained.

Table 1 As can be seen, the iron loss value of the method of the present invention is significantly improved compared to the conventional technology.

Example 2 Forsterei 1-, a high magnetic flux density unidirectional silicon steel plate after finish annealing, containing 3.2% Si and having a thickness of 0.2 mm.
After the film was mechanically removed using a grindstone, the surface of the steel was smoothed and finished in a mirror-like finish in a solution containing hydrofluoric acid and hydrogen peroxide. After mirror finishing, this steel plate was introduced into a low-pressure plasma spraying apparatus, and the substrate temperature was set at 600°C, and pentamolybdenum trisilicide powder having an average particle size of 10 μm was sprayed to form a silicide film with a thickness of 10 μm. Thereafter, a phosphoric acid-based tension coating solution was applied and baked at 850'C for 60 seconds. The magnetic properties of the product thus obtained are shown in Table 2.

The iron loss can be greatly reduced based on the second surface properties, and its industrial effects are enormous.

[Brief explanation of drawings]

Figure 1 shows the relationship between the particle size of the silicide powder to be sprayed and the thickness of the silicide film formed, and Figure 2 shows the relationship between the temperature of the substrate during spraying and the adhesion of the sprayed film after spraying. FIG. It can be seen that the iron loss further improves (the iron loss value decreases) when a tension film formation treatment is performed after the silicide film is formed on the steel sheet surface by the low-pressure plasma spraying of the present invention. (Effects of the Invention) The present invention involves removing the forsterite film of a silicon steel plate after finish annealing, smoothing the surface of the base steel, and then thermally spraying silicide powder using a low-pressure plasma spraying method to form a silicide film. The present invention lowers the iron loss of the product, and the production according to the present invention is cheaper and higher than when using conventional film forming technology.゜3-1 4゜Procedural amendment (spontaneous) May 28, 1990, 1999 Patent Application No. 180464 Name of the invention Manufacturing method for low core loss unidirectional silicon steel plate Relationship to the case of a person who performs compensating pressure Patent applicant: 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Nippon Steel Corporation Representative Zensaku Yamamoto

Claims (2)

[Claims] (1) A method for producing a low core loss unidirectional silicon steel sheet, which comprises forming a silicide film on the surface of the unidirectional silicon steel sheet after final annealing by low-pressure plasma spraying. (2) A low iron loss unidirectional silicon steel plate characterized by forming a silicide film on the surface of the unidirectional silicon steel plate after final annealing by low-pressure plasma spraying, and further applying and baking a tension imparting film. manufacturing method.