Study Of Inclusions In EAF-LF/VD-HCC

The EAF-LF/VD-HCC process system in Hengyang Pipe Factory is a pipe production line that has the special characteristics. It places strict requirement on the molten steel quality. This process affects the formation of the micro-inclusions in the molten and the size, mechanical behavior, and the dispersion of the inclusions closely affect the product quality. Therefore, a systematic study is conducted on the process micro-inclusions behavior in order to guide the production to optimize the control of the inclusions to obtain high-quality tube bloom.This paper researched the inclusion of EAF-LF/VD-HCC process in Hengyang Pipe Factory .steel were sampled separately in before and after ladle refining treatment tundish, HCC billet and steel pipe. Tracer method was applied in this study to identify the source of the inclusions in the steel. Chemical analysis, metallographic microscope observation, SEM, and EDX spectrum analysis were used to acquire the inclusions'composition, size distribution and the mechanical behavior during rolling process.The conclusions showed:(1)The purity level of 20G, 36Mn2V, 37Mn5, X42, 12Cr2MoWVTiB and SA-210C steel in each process was studied. The T[O] was 39.7×10-6,[N] was 59.9×10-6,the Micro-inclusion was 16.05 piece/mm2(<10μm Micro-inclusion was 83.34%),the Macro-inclusion was 21.46 mg/10kg.(2)In tube bloom, the source of the micro-inclusions are:desulfrization and deoxidation product>refractory material>tundish powder entrapment>tundish flux.(3)In tube bloom, the source of the macro-inclusions are:tundish flux> tundish powder entrapment>desulfrization and deoxidation product>tundish lining.(4)because the amount of macro-inclusion was high, It costs some surface defect of steel pipe easyly during rolling process.