Evolution and analysis of non-metallic inclusions during the refining process of Q355B steel
To further investigate the formation and evolution of non-metallic inclusions during the refining process of Q355B steel,two furnace samples were taken from the entire refining process of Q355B steel produced by the"BOF→LF→RH→Calcium treatment→CC"process at Chongqing Iron and Steel Works.The composition of the steel liq-uid and slag was analyzed and tested,revealing the morphology and compositional evolution characteristics of non-metallic inclusions at different stages.The research results indicate that the non-metallic inclusions in Q355B steel during the refining process are mainly SiO2-MnO-Al2O3-TiOx and CaO-MgO-Al2O3 types.The evolution of SiO2-MnO-Al2O3-TiOx type non-metallic inclusions is relatively complex.Adding aluminum slag balls during LF slag re-fining process will modify SiO2-MnO-Al2O3 type inclusions into SiO2-MnO-Al2O3-TiOx type,while RH titanium al-loying will modify them into high Ti content Al2O3-TiOx,CaO-Al2O3-TiOx,and MnO-Al2O3-TiOx type non-metal-lic inclusions.CaO-MgO-Al2O3 type non-metallic inclusions almost appear throughout the refining process.With LF slag refining,ladle argon blowing,RH vacuum refining,calcium treatment,and soft argon stirring during the refi-ning process,CaO-MgO-Al2O3 type non-metallic inclusions gradually transition from high melting point to low melt-ing point,enter the liquid phase zone,and their size and quantity gradually decrease.The use of aluminum slag ball slagging and RH titanium alloying process in LF refining is the main source of titanium composition in steel liquid and slag,which affects the evolution of non-metallic inclusions in Q355B steel refining process and requires process review.
Q355Baluminum slag balltitanium alloyingnonmetallic inclusionrefining process
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