Analysis of Cleanliness of 12Cr1MoVG Steel During LF+RH Refining Process

摘要

Cleanliness of steels is one of the major factors influencing the final product quality, especially for the steels which need to be bended, punched and welded. Many defects in the steel product are generated by the unsuitable distribution of non-metallic inclusions[1,2,3]. Many researches are contributed to the study of the steel cleanliness and have summarized the sources of non-metallic inclusions, such as reoxidation and deoxidation products, slag entrapment, exogenous inclusions and chemical reaction product[4,5]. The 12CrlMoVG steel is the mainly used as pressure vessel steel to high-pressure boiler pipe that have persistent strength, high resistance to oxidation and superior stability of microstructure[6,7]. This paper introduced industrial practice of producing clean steel by EAF-LF-RH process. The cleanliness of pressure vessel steel 12Cr1MoVG during LF+RH refining process was analyzed by methods of sampling systematically and comprehensive analysis including total oxygen and nitrogen content analysis, optical microscope observation and SEM+EDS. The factors affecting the steel cleanliness were discussed. Some measures to improve the refining process were proposed in this paper for cleaner steel.