Chemical plant refers to the process piping for downstream processing plant of refining ethylene, including carbon steel pipe and stainless steel pipe (seamless and welded): the commonly used carbon steel pipe materials are 20 × 10 (GB / t8163) and 20g (gb5310). 20g and 20x (gb9948) are rarely used. If it is used for class a pipe, it must be 100% ut; the commonly used steel grades for stainless pipe are generally 304, 316L, 316Ti, etc. In a pure theoretical sense, CrMo steel and CrMoV steel are generally not used in chemical plant, and the whole process of the plant does not involve high temperature and high pressure hydrogen conditions, but focuses on the corrosion resistance of material transmission pipeline. Special steel grades include Monel, Mo2Cu, etc.