12Mn管线钢夹杂物钙处理的热力学分析和试验研究OA

This study focuses on 12Mn pipeline steel with high manganese content(1.15%～1.35%)serving in deep-sea high-pressure environments,which suffers from an 8%～12%scrap rate due to inclusion-induced cracking.By adopting a combined technical approachcomprising microscale characterization(SEM/ASPEX),submicroscale analysis(TEM),and thermodynamic calculation,systematic calcium treatment process experiments were conducted to investigate the inclusion control mechanism and its correlation with microcracks.The results show that the primary inducement of microcracks in 12Mn pipeline steel is irregular Al₂O₃ inclusions(covering both microscale and submicroscale).Specifically,the proportion of Al₂O₃ in the crack region(68%)is three times that in the normal region(23%);the density of inclusions larger than 5 µm in the crack region(45.2 particles/mm²)is 3.6 timesthat in the normal region(12.5 particles/mm²);and the probability of stress concentration induced by irregular Al₂O₃ reaches 92%.The optimized exclusive calcium treatment parameters for 12Mn steel can increase the calcium recovery rate to 28%and promote the transformation of Al ₂ O ₃ into low-melting calcium aluminate.After treatment with this process,the inclusion circularity increases from 0.32 to 0.78,the stress concentration probability decreases to less than 5%,and the crack scrap rate of 12Mn finished pipes drops from 12%to 3%,without excessive formation of CaS(CaS proportion<8%).This calcium-based treatment technology for 12Mn steel provides key theoretical support and actionable industrial guidance for the engineering design of inclusions and the optimization of mass production processes for high-Mn pipeline steels.