JPS60195015A - Production of high-purity metallic silicon - Google Patents

Abstract

PURPOSE:Metallic silicon for industrial purposes is melted and recrystallized or further, acid-treated to reduce Ca as one of impurities less than a specific value, simultaneously other contaminants are reduced. CONSTITUTION:Metallic silicon of industry grade containing less than 1wt% of Ca as an impurity is melted by heating it over 1,500 deg.C under normal pressure, and the temperature is kept under stirring for more than 1hr, then the melt is cooled down to room temperature to effect recrystallization and the edge parts of the resultant ingot are lathed off to give high-purity metallic silicon. Or, additionally, the purified product is crushed and treated with an acid such as a hydrochloric acid-hydrofluoric acid mixture to effect purification. The content of Ca can be decreased less than 100ppm and other elements such as Mg, Al, Fe and so on also are reduced whereby the product is used as a starting material for high-quality ceramics.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing high-purity silicon metal suitable as a raw material for high-quality ceramics, which mainly removes impurity Ca contained in silicon metal.

(Prior art) Various methods for producing high-purity metals have been proposed. For example, (1) those for use in silicon wafers have been obtained by vapor phase synthesis; (no change)) Reprocessed materials are used using methods such as the strike method, Czochralski method, and ribbon crystallization method, but these are expensive as raw materials for Reramix because they are made into one layer of high-purity metal through a complicated process. (2) Industrial metals (for example, product No. 5181) contain impurities such as Ca, Mg, etc.
DDljl is contained in a large amount, and a large amount of glass phase is generated in the product, or the glass phase is high when formed into a molded product. , or by further acid treatment, mainly Qa
The purpose is to avoid reducing the size of the proboscis to 1100 pp or less.

(Structure of the Invention) The present invention is for removing impurities in metal silicon.
Metallic silicon having an impurity Ca content ω of 1% by weight or less is heated to a temperature of 1500°C or higher under normal pressure to form a melt, and is stirred for at least 1 hour or more while being maintained at that temperature or higher, or Alternatively, there is provided a method for producing high-purity metallic silicon, which further comprises subjecting the solidified lζ crushed product to acid treatment.

The present invention will be further explained in detail below. First, as the raw material metal silicon used in the present invention, one whose content of impurity Ca is 1% or less is used.

The reason for this is that when the Ca content exceeds 1% by weight, these components cannot be sufficiently evaporated from the melt obtained by heating and melting the metal silicon powder, and in order to remove it, the temperature must be adjusted. It is rated C because it requires operations such as raising the price and reprocessing.

This raw material silicon metal is crushed to a size of 10 mm or less, and then placed in a graphite crucible or the like and heated and melted preferably at 1500 to 1800 DEG C., preferably under 11 tons of heat.

When a high-frequency electric furnace is used as the heating furnace, a magnetic field is generated in the °C melt through the graphite crucible, and the stirring action of the electromagnetic force can be utilized.

Impurities such as Ca are evaporated from the melt under heating at a temperature at which impurity components in the melt are easily vaporized and at a viscosity at which they are easily evaporated, thereby reducing the impurity content in the melt.

In the present invention, the metal silicon melt is stirred at the above temperature for at least 1 hour, but if it is less than 1 hour, sufficient evaporation of Ca will not occur.

If the metal silicon melt thus obtained is poured into a mold and cooled in the air or recrystallized as it is, and then crushed to a predetermined size, for example 1n or less, the product contains Ca.
can have a content of 1 ooppm or less.

Above, we mainly explained about the removal of impurity Ca.
Not only Ca but also other impurities can be removed, although there are some differences in the amount removed.

When the crushed product obtained by the above method is further treated with acid, separated and dried, the Ca Ming A1 old 11 and
r'l''; 9 right W of 'f' (no change in content) is 11
00pp or less, Fe 50ppm or less Δku1
001) A high purity metal element with pH below 1 is obtained.

In the case of acid treatment, the grain size L is as fine as possible, ra: L <, for example, 11IIIll or more, more preferably 100 μm or less.

There are no particular restrictions on the mineral acid used in the acid treatment, but a mixed acid of hydrofluoric acid and hydrochloric acid is preferred.

(Example) Example 1 The commercially available metal No. 3i industrial grade 5i JIS No. 1 product with a purity of 98% by weight shown in Table 1 was adjusted to a particle size of 101IIl or less.
10kO scale J & L/T direct f ¥130111
111 fX 8300mm (7) Place in a lead crucible (manufactured by Tokai Carbon Co., Ltd.) and conduct high frequency induction electricity (
f'! (manufactured by Fuji Denpa Co., Ltd.). 2 Magnetic stirring! While heating at normal pressure at 1600° C. for 2 hours.

Thereafter, the lithium metal melt was cooled to room temperature and recrystallized.

Next, the above-mentioned recrystallized metal ingot (no change in content) was taken out from the graphite crucible, the lower part and surrounding area of the ingot was scraped off, and a refined metal silicon block (A>9) was removed. I got a 9.

Next, this purified metal silicon lump (A) is
Coarsely crushed with sea, particle size 0.7i+nl! Adjusted to the size of ij degree Shitamono 9kg vs. shi, 35% m fiII30
．． i 47% fu 115, M and '7) 111rm
4 si wo, 80°C) W+u ("11111 acid treated.

After that, it is filtered with a filter, and the cake is placed in a vacuum dryer (manufactured by Toyo Seisakusho Co., Ltd., trade name: VAcUM DRYINGOVEN).
1 (lam Hg, dried for 1 day and night at a temperature of 100°C, v1
￥4J metal [)Iron (B) 8k (I obtained.

The measurement results of impurities in the fi gold metal element (B) are summarized in Table 1 together with the measurement results for the purified metal element ingot (A).

For comparison, Table 1 also shows the results of comparative silicon metal (C) obtained by acid-treating the commercially available silicon metal () used in the examples in the same manner as in the examples.

The impurity analysis values in Table 1 were determined by atomic absorption spectrometry.

Table 1 Example 2 JIS No. 1 and No. 2 products in Table 1 as raw materials
A refined metal silicon ingot was obtained in the same manner as in Example 1 except that the commercial product shown in iA was used and the melt temperature and holding time were changed, and the impurity measurement results for this are shown in Table 3. ! J.

Table 2 Specification S (no change in content) Table 3 (Effect of the invention) The effects of the present invention are as follows.

1) Ca, an impurity in silicon metal, is reduced from 1% by weight to 1% by weight.
001) Removal can be reduced to below pm.

2) Impurities other than Ca such as MCI, Al1, and Fe can also be reduced.

3) It can be used as a raw material for high-grade ceramics.

Patent applicant Director of Industrial Technology Director's procedure amendment circle c method) % formula % [ 2. Name of the invention Method for manufacturing high purity metal silicon 3. Relationship with the person making the amendment f1 Patent 6' [Applicant Showa 1959, 6 Jl 26th (Shipping [1) 5, Column 6 for detailed description of the invention that is subject to amendment, page 2 for details of amendment, pages 5 to 8).

(No change in content)

Claims (1)

[Claims] 1. Metal (In order to remove impurities in silicon, metal silicon containing impurity Ca of 1% by weight or less is heated to a temperature of 1500°C or higher under normal pressure to form a C melt, and A method for producing high-purity metallic silicon, characterized by stirring for at least one hour while maintaining the temperature above the temperature, or further subjecting the solidified crushed material to acid treatment.