Characteristics of inclusion in low carbon martensitic stainless steel during solidification and cooling process
Low carbon martensitic stainless steels were widely used in various industries of economy and social devel-opment due to their excellent comprehensive properties.Non-metallic inclusions in steel have an obvious influence on the performance of low carbon martensitic stainless steel.Previous studies mainly focused on the formation,remov-al,modification,and other control methods of inclusions in the liquid steel.The characters of inclusions in low carbon martensitic stainless steel during the solidification and cooling process of the liquid steel was rarely studied.There-fore,it is necessary to study the inclusion characteristics in the solidification and cooling process of low carbon mar-tensitic stainless steel to lay a foundation for the control of inclusions in the final low carbon martensitic stainless steel products.Inclusions in S400 low carbon martensitic stainless steel were investigated in the current study.Steel samples were cooled at different cooling rates of 1,10,20 and 50 ℃/s by high temperature confocal microscopy.The effect of cooling rate on the composition transformation of inclusions in low carbon martensitic stainless steel.Dur-ing the solidification and cooling process of steel,the Al2O3 content in inclusions increased obviously,the CaO con-tent of increased slightly,and MgO and SiO2 content increased first and then decreased.The change of thermody-namic equilibrium between inclusions and the steel matrix caused by the change of temperature was the main driving force for the composition transformation of inclusions during in the solidification and cooling process.At a cooling rate of 50 ℃/s,the main composition of inclusions was 21％Al2O3-12％MgO-35％CaO-29％SiO2.With the decrease of the cooling rate,the content of SiO2 decreased and the content of Al2O3 increased gradually.With a higher cooling rate,the low carbon martensitic stainless steel was quickly cooled from the high temperature to the low temperature,the inclusion in the effective reaction time was shorter,which retarded the rapid diffusion of elements in the steel.Then,the composition of the inclusion changed little.
low carbon martensitic stainless steelnonmetallic inclusionthermodynamic calculationsolidification and coolinghigh temperature confocal microscopy
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