What is 97 metal silicon

97 metal silicon, also known as crystalline silicon or industrial silicon, metal silicon is made of quartz and coke in the electric furnace smelting products, 97 metal silicon has become the primary product of many emerging energy markets. In recent years, as the market has become more and more demanding for the quality and variety of metal silicon products, new requirements have been put forward for the smelting of 97 metal silicon. Its main use is as an additive for non-ferrous alloys. 97 silicon is made of silica and charcoal in the electric furnace smelting products, the content of the main component silicon element is about 98% (in recent years, containing 99.99% Si content is also included in 97 silicon), the remaining impurities are iron, aluminum, calcium and so on

In the traditional 97 metal silicon smelting process, there are mainly hydrometallurgy method (pickling, solution corrosion), slag treatment method, powder metallurgy method, gas blowing method, energy beam (electron beam, other ion beam) method, directional solidification method, silicon alloy method, high purity raw material method, sodium reduction method, thermite reduction method and electrolysis method. The smelting method of 97 metal silicon can not remove a variety of impurities at the same time, and often can only be effective for some of the impurities, which can not meet the requirements of metallurgical grade high purity silicon, and then affect the quality of 97 metal silicon products.

The steps of smelting 97 metal silicon are:

1. Connect the power supply of the ore furnace, heat up the furnace body, heat up the ore furnace to 500℃-700℃, and add the silicon ore raw materials to the ore furnace after grinding, screening, cleaning and drying;

2. Add the mixed material to the ore furnace, and heat the ore furnace to 1600℃-1900℃, calcination melting, and reduction reaction occurs;

3. After the reduction reaction is finished, the slag making agent is added to the feeding end, and the ore furnace is heated to 1200℃-1400℃, and chemical reaction is carried out for slagging refining. After the slagging refining is finished, the mixed liquid is left to stand, and the silicon liquid is floated and stratified with the slag phase;

4. The silicon liquid after slagging and refining flows out from the outlet of the ore furnace. In the process, the water cooling device is opened for directional solidification;

5. The use of impurities in the crystallization process of silicon liquid equilibrium segregation coefficient is far less than 1, the use of directional solidification method, so that impurities continue to segregate from the solid-liquid interface to the silicon liquid, when the silicon liquid is all crystallized, the use of mechanical removal of the high concentration of impurities, that is, 97 metal silicon.

97 metal silicon production process is simple and easy, through the use of charcoal, petroleum coke, bituminous coal mixed materials to reduce silicon ore, combined with slag refining, the use of directional solidification method, while removing a variety of impurities, to meet the requirements of metallurgical grade high purity silicon, and then improve the quality of 97 metal silicon products, suitable for industrial production.

What are the application scenarios of industrial silicon

According to the end use, industrial silicon can be divided into metallurgical grade and chemical grade two categories. The metallurgical grade is mainly cast aluminum alloy, deformed aluminum alloy and other metal alloys are also added in a small amount, the purpose of adding industrial silicon is to improve the flow and toughness of the metal. The chemical grade is mainly used in the direction of silicon-based new materials, namely organosilicon (silicon-based materials instead of carbon-based materials) and polysilicon (silicon-based materials produce energy).

Metallurgical grade silicon mainly considers the content of iron and calcium in industrial silicon, and calcium is the key. Among them, the typical recycled cast aluminum alloy of ADC12 grade mainly uses 553# industrial silicon and isosilicon. A356.2 grade primary cast aluminum alloy, mainly using 441#, 3303# industrial silicon. The deformed aluminum alloy has requirements for phosphorus and other elements in industrial silicon, and 2502# and 2202# industrial silicon with less impurity content are usually used.

Chemical grade silicon is used to produce organosilicon and polysilicon. Among them, silicone mainly uses 421#, 411#, 521# and other grades of industrial silicon, compared with aluminum alloy, the content of aluminum is higher, usually less than 0.2%. Silicone not only requires the content of iron, aluminum, calcium, but also requires the content of trace elements such as titanium, phosphorus, boron; The production of polysilicon is equivalent to the purification of silicon, and there are no strict requirements for the grade of industrial silicon, and there are requirements for some trace elements, such as boron and carbon, which affect the photoelectric conversion efficiency. The polysilicon that the market is more interested in is currently dominated by 421# industrial silicon, 521#, 441#, 553# and 99 silicon with a silicon content of about 99% are also widely used. With the progress of production process and the need for cost control, some metallurgical grade industrial silicon has gradually become the mainstream consumption specifications in the polysilicon industry.

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