The properties of industrial silicon are similar to those of germanium, lead, and tin, and its conductivity is between metals and non-metals. Therefore, industrial silicon is also called silicon metal. Industrial silicon is usually dark gray with metallic color and is in the form of lumps or granules. The main component of industrial silicon is silicon element, with a content of more than 98.7%. In addition, it contains a small amount of iron, aluminum, calcium and other impurities. Industrial silicon with different compositions in the market has different uses. Therefore, there are two main classification methods for industrial silicon, one is by composition and the other is by use.
According to the silicon content and main impurity content in industrial silicon, industrial silicon can be divided into different grades. According to national standards, industrial silicon can be divided into 8 grades. Among them, the more common ones on the market are Si553, Si441, Si421, Si411, etc. Si553 can be written as 553# in daily life. The last four digits of the grade represent the main products in the product. The maximum content requirements of impurity elements iron, aluminum, and calcium. For example, "4" in Si421 means that the iron content in industrial silicon is less than 0.4%, "2" means that the aluminum content is less than 0.2%, and "10" means that the calcium content is less than 0.10%. Taking the price of industrial silicon in East China as an example, the price of 553# is lower than that of 441# and 421#, and the latter is relatively close to the price of 3303#. As of May 2022, 2202# has the highest price, 12,400 yuan/ton higher than 3303#. Impurities can be seen The lower the content of industrial silicon, the higher the price, and the price difference between industrial silicon of different qualities is larger. In addition, out-of-grade silicon outside the scope of national standards has appeared on the market, such as 97 silicon and recycled silicon. The silicon content of 97 silicon is about 98%, and its uses are similar to Si553: recycled silicon is about 99%, which can replace Si441, Si3303 and other specifications, both of which only account for 9.35% of my country's total industrial silicon production.
Various grades of industrial silicon flow to different fields, and can be divided into metallurgical grade and chemical grade. Metallurgical grade industrial silicon is mainly used to make aluminum alloys as an additive to increase the strength and toughness of the alloy. The main grades are 553#, 551#, 441# and 3303#. Among them, the demand for industrial silicon in cast aluminum alloys is significantly higher than that of deformed aluminum alloys. Aluminum alloy. Chemical grade industrial silicon can be used to produce organic silicon and polycrystalline silicon. The grades used for the former are 421#, 411#, 521# and 2202#, while the latter mainly use 421# and 521#. At present, some polysilicon raw materials can also use 553# and 441#. This is due to the advancement of crystalline silicon purification technology and the consideration of enterprises to reduce costs and increase efficiency. In addition, different uses have requirements for the trace element content of industrial silicon.
