JPS6326355A - Production of metallic material - Google Patents

Abstract

PURPOSE:To efficiently obtain a silicon steel sheet having a thin and uniform insulating oxide film without requiring baking by vapor-depositing an element capable of forming a stable oxide on a silicon steel sheet and by cooling the steel sheet in a weakly oxidizing atmosphere. CONSTITUTION:An element capable of forming a stable oxide, e.g., Si, Cr or Mg is vapor-deposited on the surface of a heated silicon steel sheet by a proper method such as CVD or PVD. In case of CVD, the steel sheet is treated in an atmospheric gas contg. a metal halide of the element to be vapor-deposited in a CVD furnace to vapor-deposit the element on the surface of the steel sheet. The steel sheet having the vapor-deposited element is cooled in a weakly oxidizing atmosphere having <=21vol% concn. of O2 to oxidize the element and to form a very thin and fine oxide film of SiO2, MgO, Al2O3 or the like having high insulation on the surface of the steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a metal material, and more particularly, to a method for manufacturing a silicon iron plate having an insulating film on its surface.

[Conventional technology]

Electrical steel sheets are usually used in a laminated state, and in this case, each of the laminated steel sheets needs to be insulated. For this reason, electrical steel sheets are coated with an insulating film. Conventionally, this insulating film coating has been performed by applying a liquid coating material, drying it, and baking it.

[Problem that the invention seeks to solve]

However, forming an insulating film by such coating has the following problems.

1) The coating thickness tends to be uneven due to uneven coating.

it) The copper strip needs to be reheated during the drying and baking process.

ii) If the coating material is inorganic, it is necessary to heat it to approximately 700-800°C during the drying and baking process, which may adversely affect the magnetic properties of the final product, such as crystal growth on the iron plate. There is a risk of giving.

iv) Because the coated film is thick, when using laminated iron plates, the thickness of the laminated material becomes large (the number of laminated layers per unit thickness is small).

V) The coating peels off easily.

The present invention was made in view of these problems, and it is an object of the present invention to provide a method for efficiently manufacturing a silicon iron plate having a thin and uniform insulating film without requiring baking treatment. be.

[Means to solve the problem]

Therefore, the basic feature of the present invention is that an element capable of forming a stable oxide is deposited on a silicon iron plate, and then an insulating film is formed by cooling the silicon iron plate in a weakly oxidizing atmosphere.

The present invention will be specifically explained below.

In the present invention, first, a silicon iron plate obtained by an appropriate method is heated, and an element capable of forming a stable oxide is vapor-deposited on its surface.

As this vapor deposition element, a metal element such as Si, Cr, Mg, etc. is used. As for the vapor deposition method.

An appropriate method can be used, such as a chemical vapor deposition (hereinafter referred to as CVD) method or a PVD method including an ion beam irradiation method.

In the CVD process, an iron plate is treated in a CVD processing furnace in an atmospheric gas containing a metal halide as a deposition element, thereby depositing a predetermined element (an element capable of forming a stable oxide) on the surface of the iron plate.

In addition, in the ion beam irradiation method, sSi, cr.

A metal ion beam of elements such as Mg is irradiated onto the iron plate surface to vapor-deposit these elements.

Ion beam irradiation is performed by ionizing atoms, accelerating them in a magnetic field, and causing them to collide with the surface of a steel plate, thereby depositing metal on the surface of the steel plate.

After the above vapor deposition treatment, the silicon iron plate is placed in a weakly oxidizing atmosphere (
For example, 02 concentration z1vo1% or less, preferably 5vo
1% or less). As a result, the above-mentioned vapor deposited elements are oxidized, and SiO snow, MgO, At2Q3 are formed on the steel plate surface.
A very thin, dense, and highly insulating film (oxide film) is formed.

Since this oxide film is formed extremely uniformly and thinly, it also has excellent adhesion to the base material.

As the silicon iron plate that is the raw material for the method of the present invention, general electrical steel plates (non-oriented grade) and grain-oriented electrical steel plates can be used, but these steel plates can also be treated with 8 silicon to add Sl. An appropriate silicon steel plate, such as a steel plate made of aluminum, can be used.

Note that general electrical steel sheets are usually continuously annealed at 1000 to 1100°C, and grain-oriented silicon steel sheets are continuously annealed at 1000 to 1200°C, and in the present invention, the heating state of such continuous annealing is utilized to perform the vapor deposition. Treatment - A cooling treatment can be performed.

Also, as a method of obtaining high-silicon iron plates by silica treatment,
CVD method, ion beam irradiation method, etc. can be used.

Among these, continuous treatment of steel plates by CVD method is 5iC4
A non-oxidizing gas containing 〇s i ct, which is carried out continuously at a temperature of 1023 to 1200°C in a non-oxidizing gas atmosphere containing a mob fraction of 5 to 35, is a neutral or reducing gas. As a carrier gas for 5iCt4, Ar, N2 + He + N2 + C)14, etc. can be used. Among these carrier gases,
When considering the processability of exhaust gas, H,,CH.

etc. have the disadvantage of generating HCl and the need for its treatment, whereas Ar does not cause such problems.

He and N2 are preferable, and from the viewpoint of preventing nitridation of the material, Ar is especially preferable.
, He are most preferred.

The main reaction on the steel plate surface during CVD treatment is S Fe +
5iCt4 →Fe3 S i + 2 Fe(J4↑
It is. One Si atom is deposited on the steel plate surface to form a Fe381 layer, two Fe atoms become FeC42, and FeCt
! It is emitted from the surface of the steel sheet in a gaseous state at temperatures above the boiling point of 1023°C. Therefore, the St atomic weight is 28.0
86,ii”eSince the atomic weight is 55.847,
The mass of the steel plate decreases, and the plate thickness also decreases accordingly. By the way, when a Si 6.5% steel plate is manufactured using a 3% Si steel plate as a base material and a CVD process is performed, the mass decreases by 8.7 centimeters and the plate thickness decreases by about 7.1 inches.

Conventionally, the reason why CVD processing takes too much time is because of the CVD process.
This is thought to be due to insufficient consideration being given to the processing conditions of D. The inventors of the present invention have investigated and found that the following factors are necessary for performing CVD processing quickly.

■Optimization of 5ic4 concentration in atmospheric gas.

■Optimization of processing temperature.

(2) Promotion of diffusion of 5ict to the steel plate surface and Fecz dissipation from the steel plate surface.

For this reason, it is preferable to specify the 81 concentration in the atmospheric gas and the processing temperature in the CVD processz)e First, the S81 concentration in the non-oxidizing gas atmosphere in the CVD process
The i Ct concentration is defined as 5 to 35% in terms of mot fraction, and the steel plate is continuously subjected to CVD treatment in such an atmosphere.

Si where 5iC24 in the atmosphere is expected to be less than 5
For example, if the si of the steel plate is 1.0, the enrichment effect cannot be obtained.
The treatment takes too much time, such as requiring 5 minutes or more to achieve % enrichment, making it difficult to implement a continuous process.

On the other hand, even if 5icz is contained in an amount exceeding 35%, the reaction at the interface becomes rate-determining, and no further 81-enriching effect can be expected.

Furthermore, in the CVD process, the higher the S i C4 concentration, the more likely large voids called Kirkendahl voids are generated. These voids are hardly seen when the 5icz4 concentration is around 15%, but begin to form when the 5icz4 concentration exceeds 15%. However, when the 5iC4 concentration is 35% or less, even if voids are generated, they can be almost completely eliminated by a diffusion process performed subsequent to the CVD process.

In other words, when the S i Ct concentration exceeds 35%, voids are significantly generated and remain even after the diffusion treatment.

The CVD treatment temperature is in the range of 1023 to 12 oo<0>C.

Since the CvD treatment reaction is a reaction on the surface of the steel sheet, the treatment temperature is strictly the steel sheet surface temperature.

The boiling point of FeCl1°, which is a reaction product from CVD processing, is 1023°C, and below this temperature, FeCl2 is not dissipated from the steel sheet surface in a gaseous state, but adheres to the steel sheet surface in a liquid state and inhibits the vapor deposition reaction. . According to the results of basic experiments conducted by the present inventors, the enrichment rate of 81 per unit time differs markedly at the boiling point of FeC42, and 1023
At temperatures below ℃, the deposition rate is low, making it difficult to apply to continuous processes. Therefore, the lower limit of the processing temperature is set to 1023°C.

On the other hand, the reason why the upper limit is specified as 1200°C is as follows. The melting point of Fe3Si is 1250°C, as is clear from the Fe-Si phase diagram shown in Fig. 2, but according to experiments by the inventors, even when treated at about 1230°C, which is lower than 1250°C, the steel plate surface remains is partially melted, and the edge portion of the steel plate is also melted due to overheating. The reason why the steel sheet melts even at 1250° C. or lower is presumed to be because St is vapor-deposited on the surface of the steel sheet at a St concentration of 14.5% or more equivalent to Fe3Si.

On the other hand, if the treatment temperature is 1200°C or lower, no melting will be observed on the surface of the steel plate, and overheating of the edges will be reduced by setting the average temperature at the center of the steel plate to 1200°C.
It was experimentally confirmed that the temperature could be kept at about 0°C and only a small amount of dissolution was required. For the above reasons, CVD
The processing temperature is specified as 1023°C to 200°C.

Further, plasma CVD or ion beam irradiation can be used for Sl vapor deposition, and in these cases, the steel plate can be treated at a relatively low temperature.

In the former method, the steel plate is heated to 200 to 800℃.
Processing is done to a certain degree. The latter method is performed by irradiating the surface of the steel plate with S1 ions, and the treatment in this case can be performed even at room temperature.

The steel plate on which Sl was deposited as described above continues to be coated with Si.
A diffusion process is performed. In other words, immediately after the Si vapor deposition process, the Sl concentration is high near the surface of the steel plate, and the base material S1 concentration remains in the central part, which is then soaked and diffused to produce a uniform S1 concentration.
t concentration or a predetermined concentration distribution.

Methods for diffusing Si into the steel strip include a soaking diffusion method and an ion beam irradiation diffusion method.

The soaking diffusion method diffuses Si by soaking the steel plate at a predetermined temperature.It must be carried out in a non-oxidizing atmosphere to prevent the surface of the steel plate from being oxidized, and the higher the temperature, the faster the treatment will be. It takes less time.

This diffusion treatment may be carried out at a constant temperature, but as can be seen from the Fe-3L phase diagram in Figure 2, as the diffusion progresses, the St concentration in the surface layer of the steel sheet decreases and its melting point increases. Diffusion can be promoted by gradually increasing the temperature (for example, increasing the temperature in multiple steps) to an extent that does not melt the steel plate as it progresses. For example, 6.5%SL
In the case of steel, it is possible to raise the temperature to 1400° C. even taking into account overheating of the edges.

In addition, in the latter ion beam irradiation method, ions with high kinetic energy collide with the solid surface, resulting in sputtering phenomenon (the effect of hitting the solid surface at high speed) and accelerated diffusion effects, as well as the effects of ion collision. Si is diffused by the effect of increasing solid temperature by converting kinetic energy into thermal energy.

Ion species to be collided in such a diffusion process include inert gas ions such as Ar+ and He+, Fe
Ions etc. can be used.

Among these, inert gas ions can be said to be suitable when the surface reaction of the steel sheet is an issue. However, when these ions are used, Ar, He, etc. remain in the surface layer of the steel sheet. In contrast, the following advantages can be obtained by using sFe ions.

(a) Since it is the same element as the base material, it does not cause any problems due to residue.

(The mass of the hot ions is large, and the collision effect is large.

(c) In the CVD process, Fe in the copper strip is consumed, but the amount of the consumption can be compensated for, albeit slightly.

) A gaseous substance is preferable for ionization, and C
FeC14 (boiling point 1023°C) generated during the VD process can be used.

The above diffusion treatment may be performed until SL is uniformly diffused into the steel sheet, but in some cases, the treatment may be terminated while the surface layer sig degree is higher than the Sj concentration at the center of the steel sheet in the thickness direction. , a steel plate having a non-uniform Sl concentration in the thickness direction may be obtained.

On the premise of the above-described Si vapor deposition treatment and diffusion treatment, typical embodiments of the continuous treatment process for steel plates according to the present invention will be illustrated below.

(1) A steel plate was processed to 1023
Continuous exfoliation treatment at a temperature of ~1200°C, then 5
A diffusion treatment is performed to diffuse 81 into a predetermined state inside the steel sheet in a non-oxidizing gas atmosphere that does not contain icz, and then an element that can form a stable oxide is vapor-deposited by the CVD method, and then in a weakly oxidizing atmosphere. to form an insulating film.

(2) A steel plate was heated to 1023
Continuous silicon leaching treatment is carried out at a temperature of ~1200°C, then Si is diffused into the steel plate by irradiating the steel plate with an ion beam, and then an element capable of forming a stable oxide is vapor-deposited by CVD method. Then, it is cooled in a weakly oxidizing atmosphere to form an insulating film.

(3) The steel plate is treated with an ion beam irradiation method using St+ ions to deposit SL on the surface, then the steel plate is irradiated with an ion beam to diffuse Sl into the steel material, and then stable oxidation is performed using the CVD method. Depositing elements that can form substances, followed by cooling in a weakly oxidizing atmosphere,
Forms an insulating film.

In the above embodiment (1), by selecting 8i as the vapor deposition element for the insulating film, the process itself can be made more efficient and can be operated economically.

In other words, in general, in CVD processing for the purpose of silicon extrusion treatment, it is necessary to avoid as much as possible the mixing of gas components such as 02 and Ct into the processing gas introduced into the furnace, whereas in CVD treatment for the purpose of forming an insulating film, In the CVD process, a rough processing gas mixed with Ox s CL can be used. Therefore,
Since the processing gas discharged from the CVD processing furnace for silicon extrusion processing (81 addition processing) still contains a considerable amount of 5IC44 gas (also contains Os, CL, etc.), it is necessary to insulate this exhaust gas. It can be introduced into a CVD processing furnace for film formation and subjected to CVD processing.

In addition, in order to increase the CVD processing speed to the extent that continuous processing of steel plates is possible in the above-mentioned CVD processing for the purpose of Si vapor deposition, as mentioned above, 81C in the atmospheric gas
It is necessary to optimize the t, concentration and processing temperature, but in addition to this, it is possible to further increase the CVD processing speed by promoting the diffusion of 5iCt to the steel plate surface and the dissipation of FeC4 from the steel plate surface. It becomes possible.

It is thought that the purity of the deposited layer will also decrease, and for this reason the idea of keeping the gas flow to the minimum necessary has been established. However, in the research conducted by the present inventors, due to the gas flow being suppressed in this way, the diffusion movement of the reaction gas to the base material interface and the separation of reaction by-products from the interface surface layer do not occur smoothly. It has been found that the treatment takes a long time, and furthermore, because the gas flow is suppressed, the concentration of the reactant gas in the CVD treatment zone is distributed, resulting in non-uniformity in the thickness of the deposited film.

Based on these facts, we conducted further studies and found that 5iC4 can be diffused onto the steel plate surface by blowing atmospheric gas onto the treated material using a blowing nozzle in the CVD treatment zone, or by forcing the atmosphere to circulate using a fan, etc. It was found that the diffusion of FeCLH, which is a reaction product, from the surface of the steel sheet is significantly promoted, and CVD processing can be performed at a high deposition rate while suppressing non-uniformity of the deposited film.

A method in which atmospheric gas is sprayed onto the surface of the steel plate using a spray nozzle is particularly effective for improving CVD processability.

Figure 3 shows the implementation situation using this nozzle spraying method, in which a spray nozzle (6) is placed in the CVD treatment zone (2) facing the copper strip (S), and an atmosphere containing 5iCt4 is placed on the steel plate surface. Gas is sprayed. Figure 4 A) and ((B) are
This shows the spraying situation by the spray nozzle (6), which can spray perpendicularly to the steel plate surface as shown in (), or obliquely as shown in ().

The 81 enrichment rate per unit time due to such nozzle spraying increases in proportion to the increase in the flow velocity of the gas colliding with the steel plate surface, but even if the flow velocity is increased excessively, the reaction at the interface) becomes rate-limiting. Therefore, no further Si enrichment effect can be expected. Generally, a sufficient effect can be obtained at a flow rate of 5 Nm/seQ or less.

FIGS. 5 and 6 show the effects of 5ic4 concentration and CVD processing temperature on CVD processability.

In the figure, A is the atmosphere method, that is, CVD treatment without nozzle spraying, and B is the nozzle spraying method, that is, as shown in Figure 3, atmospheric gas is applied to the steel plate surface at a rate of 0.57"/
The case where CVD treatment is performed while spraying at a flow rate of S is shown. Note that the Si enrichment ratio refers to the C
It shows the increase in St due to VD processing.

According to this, a large Si-enriching effect is obtained when the SiCt concentration is 5 or more and the CVD treatment temperature is 1023° C. or more. Even under the same conditions, the method of spraying atmospheric gas with a spray nozzle has a much superior Si enrichment effect (CV
It can be seen that D processability) was obtained.

Figure 7 shows the relationship between the deposition time of the atmosphere method A and the nozzle spraying method B and the St concentration in the steel sheet (base material Si amount + deposited Si amount).
i: 3%, 0.5m thick steel plate with 5ic4 concentration 21%,
The results were investigated using cVD treatment at a treatment temperature of 1150°C. In addition, in the nozzle spraying method, a slit nozzle is used to apply 0.2 Nm/se from the perpendicular direction to the steel plate.
Atmospheric gas was blown at a flow rate of e. As can be seen from the figure, it takes 7 minutes to obtain the same amount of Si vapor deposited on the 6.5%St steel phase using the atmospheric method, whereas it takes 1.5 minutes using the nozzle spraying method B.
I was able to process it in 5 minutes.

Figure 8 shows the collision gas flow velocity and steel plate in the nozzle spraying method.
1 enrichment ratio (same as in FIGS. 5 and 6), and the 81 enrichment ratio of the steel plate increases in proportion to the collision gas flow velocity up to a predetermined level.

〔Example〕

Fig. 1 shows an example of a thin plate manufacturing line in which Si vapor deposition processing and elemental vapor deposition processing for forming an insulating film are carried out by the CVD method, in which (1) is a heating zone, (2) is a CVD treatment zone, ( 3) is a diffusion treated zone, (4) is a CVD treated zone, (5
) is the cooling zone.

An example of a manufacturing process using such a line will be described. First, a steel strip (S) is non-oxidized heated to 1150° C. in a heating zone (1), and then guided to a CVD treatment zone (2). Here, a reactive gas containing 80% Ar and 20% 5iC4 is blown onto the surface of the steel strip from a nozzle at a flow rate of 0.3 Nm/S to carry out silicon exfoliation treatment. The copper strip is then treated with a diffusion treatment strip (
3), soaked and maintained at 1200° C. in a non-oxidizing atmosphere, and subjected to a diffusion treatment, thereby obtaining a 6.5% Sl iron plate. Next, the iron plate is led to a CVD treatment furnace (4) and subjected to 8Si treatment at 1200°C in an atmosphere of (SiC4 (s%) + Ar) for 1 minute, and then in a cooling furnace (5) with N containing 0.5%. , cool in atmosphere.

For example, by such treatment, a stable oxide layer of about 10 μm is formed on the surface of a high-silicon iron plate.

〔Effect of the invention〕

The present invention described above (according to this invention, there is no need for baking treatment,
Moreover, high-silicon steel sheets with a uniform and thin insulating film can be manufactured efficiently, and since baking is not required, the magnetic properties of high-silicon steel materials are not impaired, resulting in high-quality magnetic materials. be able to.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a continuous processing line for implementing the present invention. FIG. 2 is a phase diagram of the Fe-5t system. Figures 3 and 4 (a). ((b) shows the CVD processing situation using the nozzle spraying method, Fig. 3 is an overall explanatory diagram, and Fig. 4 b) and (b))
are explanatory diagrams each showing a nozzle spraying method. FIG. 5 shows the relationship between the 5iC4 concentration in the gas and the Sk enrichment ratio in the copper band in the CVD process, and FIG. 6 shows the relationship between the CVD process temperature and the Si enrichment ratio in the copper band. Figure 7 shows S
The relationship between the i-evaporation time and the 81 concentration in the copper strip is shown by comparing the atmosphere method and the nozzle spray method. FIG. 8 shows the relationship between the flow velocity of the atmospheric gas colliding with the copper strip and the Sl enrichment ratio of the steel strip in the CVD treatment using the nozzle spraying method. Patent applicant Nippon Kokan Co., Ltd. Inventor Tadashi Abe Hiroma
Oka 1) Kazu Iruma
Hiro Tsune Yamaji, Patent Attorney
Masaru Yoshihara Patent Attorney Toma
Masatoshi Kiji Lawyer Yoshihara
Hiroko No. 5 SiC in atmosphere gas, g41 fake 19 (mo1%) Fig. 6 7N opening aG3-26355 (8) Fig. 7 Fig. 8

Claims (1)

[Claims] A method for manufacturing a metal material, which comprises depositing an element capable of forming a stable oxide on a silicon iron plate, and then forming an insulating film by cooling the silicon iron plate in a weakly oxidizing atmosphere.