Material selection for polysilicon process pipelines
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In polysilicon production, stainless steel pipes are primarily used for the process pipelines. Considering the issue of intergranular corrosion, which type is better to use: 304 or 316? In polysilicon production, what are the substances that may cause intergranular corrosion in stainless steel? Given the importance of material selection and the need for cost-effectiveness, we welcome extensive discussions from everyone! For example, there are certain differences in the materials used for the exhaust pipes of reduction furnaces and those used for low-temperature chlorosilane pipes. Everyone is welcome to share their opinions!
:Shutup: Process pipelines are mostly made of carbon steel. For high-purity water, hydrogen, and certain material lines, stainless steel is used.
I think it’s still necessary to choose the pipeline material based on prior considerations; it’s best to visit several polysilicon factories as well.
The main material is usually 316, while that used for hydrogen is 304
The main material is usually 316, while that used for hydrogen is 304
If it's 6N 304, that should be sufficient
The key is to control external impurities well; if that’s done, using carbon steel is no problem. Domestic technology is not sufficient at the moment, so stainless steel is used more often.
Intergranular corrosion of materials is part of the corrosion that occurs as a result of thermal effects. The sensitization of stainless steel occurs at temperatures between 450–850°C, and the underlying mechanism is the \"chromium deficiency theory.\" Stainless steel must contain more than 12% chromium in order to have better corrosion resistance compared to ordinary carbon steel. Based on the composition of stainless steel, 304 stainless steel has a chromium content of 17.00–19.00%; therefore, it is suitable for use in exhaust gases from reduction furnaces. Carbon steel can be used for other applications. However, considering that carbon steel tends to rust, requires difficult cleaning, and can contaminate the system, stainless steel (mainly 304) is also typically used in chlorosilane systems.
The main materials are generally carbon steel, but the pipes used in the reduction process and those for high-purity trichlorosilane are made of 316 stainless steel, while the hydrogen-related pipes are made of 304 stainless steel
To take cost into account, hydrogen, deionized water, and instrument air are made of stainless steel, while most of the process pipelines are made of carbon steel.