"Silicon" summary
Classification and testing of silicon-containing metal products
Commodities such as metallic silicon, silicon carbide, ferrosilicon alloy, and silicon slag are similar in shape and composition, making it difficult to judge by sensory perception, which brings certain difficulties to on-site inspection. Familiar with the regulations on various testing indicators such as tariffs and standards, and accurately and quickly distinguishing these commodities is the key to the current classification and testing. As shown in the picture below, what should I do if I can’t tell the difference from the appearance? Don't worry, the editor will take you to reveal the secrets of silicon-containing metal products.
01 Elemental silicon (2804.6000)
At present, commodity silicon is generally divided into metal silicon and semiconductor silicon in the industry. Metal silicon refers to the provisions of the national standard "Industrial Silicon" (GB/T 2881-2014), and its silicon content should be above 98.7%.
02 Silicon carbide (2849.2000)
Silicon carbide is an inorganic substance with a chemical formula of SiC. It is a non-metallic mineral obtained by smelting petroleum coke (or coal coke), sawdust, quartz sand, etc. in a resistance furnace at high temperature. There is no significant difference between the tax code and the industry definition.
03 Ferrosilicon alloys (7202.2000)
Ferrosilicon is a ferrosilicon alloy composed of silicon and iron made by smelting quartz, coke, steel scrap and other raw materials in an electric furnace at high temperature. It is worth noting that, according to the regulations of the tariff, the iron element content must be 4% or more by weight and the silicon content exceeds 8% to be called ferrosilicon alloy, which is different from the industry product standard GB/T 2272. . When exporting ferrosilicon, it is necessary to provide an export license to the customs. This kind of commodity is restricted by the state and is a key commodity under the supervision of the customs.
04 Silicon slag (2621.9000)
Generally, the remaining slag after refining silicon ore is called silicon slag. Most people think of silicon slag as scrap ferroalloy slag that is useless. But in fact, the value of silicon slag itself is very large, because of its low price and a certain amount of silicon, it can be used in many fields such as recrystallization, product purification, and steelmaking. Silicon slag can be produced in the process of producing elemental silicon, silicon carbide, and ferrosilicon alloy. These products have similar appearance and similar element content, and there are often false reports and concealed reports. Accurate determination of silicon slag is the key to classification and testing.


01 X-ray fluorescence spectroscopic analysis
Metal silicon, silicon carbide, ferrosilicon, and silicon slag can be determined by X-ray fluorescence spectrometry. , the sample is more likely to be ferrosilicon and silicon slag. When the content of impurities such as aluminum and calcium in the sample is high, it can be considered as silicon slag.
02 X-ray diffraction analysis
The composition of metal silicon, silicon carbide, ferrosilicon and silicon slag can be accurately determined by phase analysis combined with X-ray elemental analysis. The main phases of metal silicon and silicon carbide are silicon and silicon carbide, the main phases of ferrosilicon are silicon and ferrosilicon, and the phases of silicon slag are generally composed of silicon, silicon carbide, silicon dioxide, ferrosilicon and aluminosilicate, etc. two or more phases of matter.
03 Scanning electron microscope energy spectrum analysis
Metallic silicon, silicon carbide and ferrosilicon elements occur in a single form, but silicon slag elements occur in a complex form, as shown in the figure below, from the electronic image of the sample, there is not much difference in the shape of the sample except that the particle size is different , but the silicon content of energy spectrum analysis point 1 is 100%, which is metallic silicon; point 2 energy spectrum analysis contains silicon, iron, carbon elements, including ferrosilicon and silicon carbide; point 3 energy spectrum analysis contains silicon, iron, aluminum, calcium Elements such as silicon slag. Electron microscope energy spectrum analysis The sample contains silicon, ferrosilicon, silicon carbide, silicon slag and other forms, which is a typical silicon slag sample.


3. Classification
Product name, usage, processing method, appearance, and component content are common elements of silicon-containing metal products. The classification and testing of such commodities uses X-ray fluorescence spectroscopy and X-ray diffraction as the main methods to detect the composition content of commodities, supplemented by other elemental analysis methods, combined with the merchant's processing technology and usage, etc., to accurately classify.