JPH0953131A - Method for dissolving metallic silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently dissolve metallic silicon in molten aluminum, etc., by adding metallic silicon of specific grain size, washed with mineral acid, and a chloride-containing flux at the time of adding silicon to a molten metal such as aluminum. SOLUTION: At the time of, for example, adding silicon to a molten metal of aluminum ground metal of about 99.7% purity, metallic silicon of 2-30mm grain size, washed with hydrochloric acid, is added to the molten metal together with a flux containing at least one chloride (e.g. 50% NaCl, 50% KCl). By this method, metallic silicon can be efficiently dissolved in the molten aluminum and flowability can be improved, and an aluminum-base silicon alloy capable of thin-wall casting can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting metallic silicon for the purpose of producing a silicon alloy such as aluminum.

[0002]

2. Description of the Related Art Aluminum-based silicon alloys have improved fluidity and are capable of thin-wall casting, and have the property of being significantly improved in strength and the like by adding magnesium or copper and heat-treating them. Is the most widely used alloy. Metallic silicon is used as a raw material for adding silicon. As a method for adding metallic silicon, metallic silicon is put in an iron box, preheated and dried to remove water, and then added to the molten metal by a forklift or the like. Since metallic silicon has a high melting point of 1414 ° C.,
It is melted in an aluminum melt kept at a high temperature of about 50 ° C. for 45 minutes or more. After melting,
Impurities such as oxides generated from metallic silicon and other melting raw materials are removed using a flux or the like, and the temperature is lowered to around 700 ° C., which is a molten metal temperature suitable for casting, and casting is performed.

[0003]

Since the production of metallic silicon consumes a large amount of electric power, there is no manufacturing plant in Japan, and all production depends on imported products. The standard specification of metallic silicon for alloy addition is 90% by weight or more for a size of 10 to 100 mm, and the composition is 0.5% or less of iron, 0.5% or less of aluminum, and 0.3% or less of calcium. Quality varies greatly depending on the country of production and the manufacturer, such as size and segregation of calcium, and inspection is essential before use. The fine powder metal silicon contained in the metal silicon has a large specific surface area, and after being charged, it floats on the surface of the molten metal and is rapidly oxidized. Since oxidized metal silicon has a high melting point, it does not melt in the aluminum melt and remains in the melt as unmelted silicon. Further, the high-temperature molten metal at the time of melting metallic silicon produces oxides such as aluminum and magnesium. Undissolved silicon and oxides are extremely hard, and when mixed in a cast product, they cause a defective product as a hard spot. Therefore, after melting, a flux process must be provided to separate and remove from the molten metal. On the other hand, a trace amount of calcium contained in metallic silicon is a harmful impurity that impedes the castability such as the fluidity and riser property of the molten metal, and causes segregation hard spots. Casting foundry companies that demand quality maintain the internal standards of the PPM order. The high-temperature molten metal after melting is cast at about 700 ° C., which is about 100 ° C. lower by about 100 ° C., by cooling by forcing a cold material such as a metal or forcibly cooling it. As mentioned above, the production of aluminum silicon-based alloys requires melting equipment for holding at high temperature for a long time, molten metal management, and raw material management. Currently, most aluminum-based silicon alloys are manufactured by aluminum alloy ingot manufacturing companies. There are very few foundry casting companies that are professionally manufactured and in-house compounded.

[0004]

Means for Solving the Problems In adding silicon to a molten metal such as aluminum, a particle size of 2 mm washed with mineral acid
In a melting method characterized by adding metallic silicon having a size of 30 mm or less and a flux containing at least one kind of chloride, and in a method of adding silicon to a molten metal such as aluminum, a particle size of 2 mm or more and 30 mm washed with a mineral acid A dissolution method, characterized in that the following metallic silicon is coated with a flux containing at least one chloride. In the present invention, one chloride may be used alone, or a mixture of two or more chlorides or other compounds may be used. Other compounds include Na2CO3, K2
CO3, CaCO3, NaSO4, K2SO4, AlF
3, KBF and the like can also be used together.

[0005]

According to the present invention, by washing metallic silicon having a size of 2 mm or more and 30 mm or less with a mineral acid, calcium that is biased on the surface of metallic silicon is removed and wettability with molten aluminum is improved. As a result,
It melts in a short time in the aluminum melt temperature range of 50 ° C. or higher and 800 ° C. or lower. Further, since undissolved silicon is not generated by fine powder silicon, the amount of dross generated during melting is extremely small. Next, the addition or coating of chloride flux serves as an anti-oxidation film for metallic silicon in the furnace, which improves the melting yield of metallic silicon and also reacts with molten metal contaminants such as calcium introduced from within metallic silicon. Since it is separated from the molten metal, a clean molten alloy can be obtained. The heat absorption during melting of metallic silicon causes a decrease in the melt temperature around 100 ° C.,
The molten metal temperature range is suitable for casting.

[0006]

EXAMPLE Flux Constituent Metal Silicon Addition Yield Inclusion Removal Effect Regarding the amount of dross generated, Examples 1 to 4 and 1
It is shown by the comparative example of ~ 2.

Example 1 73 kg of an aluminum base metal having a purity of 99.7% was melted, and a first analysis sample and a sample (K mold) for measuring the amount of non-metallic inclusions from a molten metal held at 800 ° C. Called). After that, 5.
5 kg of metal silicon having a particle size of 2 mm or more and 30 mm or less, and 5 wt% flux (50% NaC
l, 50% KCl) and add 10 with a phosphorizer.
Stir twice. After 7 minutes, the melting of metallic silicon was visually confirmed, and therefore the second sampling was performed under the same conditions as the first sampling.

Example 2 70 kg of an aluminum ingot having a purity of 99.7% was melted, and the molten metal was kept at 800 ° C.
The analysis sample for the second time and the K mold were sampled. After that, flux (50% NaCl, 5
Particle size of 2 kg or more of 5.3 Kg coated with 0% KCl) 3
Charge metal silicon of 0 mm or less and use a phosphorizer to
Stirred 0 times. After 7 minutes, the melting of metallic silicon was visually confirmed, and therefore the second sampling was performed under the same conditions as the first sampling.

Example 3 78 kg of an aluminum ingot having a purity of 99.7% was melted, and the molten metal was maintained at 800 ° C.
The analysis sample for the second time and the K mold were sampled. After that, the molten metal surface is washed with hydrochloric acid and flux (50
% NaCl, 50% KCl), 5.9 Kg of metallic silicon having a particle size of 2 mm or more and 30 mm or less was added, and the mixture was stirred 10 times with a phosphorizer. After 7 minutes,
Since the melting of metallic silicon was confirmed, the second sampling was performed under the same conditions as the first sampling.

EXAMPLE 4 100 g of 90% aluminum for the purpose of adding 71 kg of aluminum ingot having a purity of 99.7% and inclusions,
As in Example 1, the first analysis sample and the K mold were sampled from the molten metal in which a 10% manganese master alloy was melted and held at 800 ° C. After that, 5.4 kg of metallic silicon having a particle size of 2 mm or more and 30 mm or less washed with hydrochloric acid on the surface of the molten metal, and 5 wt% flux (5
0% NaCl, 50% KCl) was added, and the mixture was stirred 10 times with a phosphorizer. After 7 minutes, it was confirmed by visual inspection that the metallic silicon had melted.
The second sampling was performed.

Comparative Example 1 72 kg of an aluminum ingot having a purity of 99.7% was melted and held at 800 ° C., and the first sampling was performed under the same conditions as in Example 1. Then, without adding flux, 5.5 kg of 0 mm or more and 30 mm or less of metallic silicon was charged, and after stirring 10 times with a phosphorizer, 7 minutes later, the second sampling was performed under the same conditions as the first sampling. It was

Comparative Example 2 74 kg of an aluminum ingot having a purity of 99.7% and 100
The first sampling was performed under the same conditions as in Example 1 from a molten metal in which 90 g of aluminum 90% and manganese 10% mother alloy was melted and held at 800 ° C. Then 5.6
After charging kg of standard size metallic silicon and stirring 10 times with a phosphorizer, 7 minutes later, a second sampling was performed under the same conditions as the first sampling. For the sampled test piece for analysis, the yield of metallic silicon was calculated by the following formulas (1) and (2) using an emission spectrophotometer. In the formula) A: Weight of molten metal before addition of metallic silicon a:% of silicon in molten metal before addition of metallic silicon ÷ 100 b:% of silicon in molten metal after addition of metallic silicon c: Weight of added silicon x: Weight of molten silicon Using the above formula, the results of the fractionation of silicon and calcium, the yield of silicon, and the amount of inclusions measured by K mold (K value represents the amount of inclusions, the higher the value, the more inclusions) and the visual dross. Occurrence is shown in Table 1. From Table 1, it can be seen that the molten metal washed with hydrochloric acid and the flux
The highest silicon yield was observed. The increase in calcium when the amount of metallic silicon added was 7% was 30 PPM or less in the combination of the hydrochloric acid-cleaned product and the flux, which was about one-third lower than around 100 PPM of the untreated product. It was found that the level of 40 to 70 PPM was obtained only with the flux that was not washed with hydrochloric acid, and was not suitable for some castings requiring high strength. The trend of inclusions is that in Example 4,
The effect of removing inclusions by the flux was confirmed, but undissolved silicon was confirmed in Comparative Example 1 and undissolved silicon and oxide were confirmed in Comparative Example 2, and the degree of contamination of the molten metal after the introduction of metallic silicon was high. In addition, the amount of visually generated dross is
Flux only> mineral acid treated product.

[0013]

According to the present invention, when the molten metal temperature is around 850 ° C., about 1
The time-consuming dissolution of metallic silicon is lower than 50 ° C., 70
It can be melted in a short time at the temperature of molten metal in the range of 0 ° C. Addition of chloride flux separates from the molten metal contaminants such as calcium introduced from metallic silicon and non-metallic inclusions such as oxides generated by dissolution of metallic silicon. Cleaning with mineral acid
It significantly reduces calcium contained in metallic silicon. As a result, a clean and high-quality molten aluminum-based silicon alloy melt can be obtained. Further, since melting can be easily carried out with existing equipment such as a crucible furnace and a ladle, it has been possible to facilitate the in-house blending of an aluminum-based silicon alloy that could not be popularized in the past, so that the industrial effect of the present invention is very large .

Claims (2)

[Claims] 1. When adding silicon to a molten metal such as aluminum, metallic silicon washed with a mineral acid and having a particle diameter of 2 mm or more and 30 mm or less and a flux containing at least one chloride are added. Dissolution method. 2. A method of adding silicon to a molten metal such as aluminum by coating a flux containing at least one chloride on metallic silicon washed with a mineral acid and having a particle size of 2 mm or more and 30 mm or less. Method.