Abstract: In this paper, the main reason of cracking of an acid resistant sample of a large steel company in China is the inclusion of type B and Ds in the steel, which is modified by the operation of the LF furnace, calcification treatment, inhibiting the formation of the CaS, MnS inclusion ,the vacuum treatment of the RH, the vacuum treatment of the steel, and the protection measures to control the secondary oxidation of the steel, controlling the size of inclusions in molten steel less than10 μm, ensuring that the acidity of steel plate can meet the requirements.

Key words: acid-resistant steel, calcification treatment, inclusion