Fe-5Mn-2Al-0.15C中锰钢连铸凝固偏析及粒子析出行为

Elemental segregation and precipitation behavior during solidification process of continuous casting for Fe-5Mn-2Al-0.15C medium manganese steel

为研究Fe-Mn-Al-C系中锰钢连铸凝固偏析及粒子析出特性,采用光学显微镜观察Fe-5Mn-2Al-0.15C中锰钢的显微组织,并通过Thermo-Calc热力学软件研究了其凝固模式、溶质元素偏析及粒子析出行为。结果表明,该中锰钢铸锭的显微组织主要为板条状马氏体,且含有少量铁素体;其凝固模式为L→L+δ→L+δ+γ→δ+γ→γ;Al元素的平衡分配系数大于1,发生负偏析,偏聚到δ-铁素体枝晶内部;而Mn、Nb、V、S等溶质元素发生正偏析,均偏聚到枝晶间。AlN主要在枝晶内析出,其析出温度为1 448℃;MnS、Nb和V的富集物主要在枝晶间析出,且MnS和Nb的富集物均在1 400℃以上开始析出,而V的富集物的析出温度为760℃。

In order to study elemental segregation and precipitation characteristics during solidification process of continuous casting for Fe-Mn-Al-C system medium manganese steel,the microstructure of Fe-5Mn-2Al-0.15C medium manganese steel was observed by optical microscope.Solidification mode,solute elemental segregation and precipitation behavior were investigated by Thermo-Calc thermodynamics software.The results show that the microstructure of medium manganese steel ingot is mainly lamellar martensite and contains a small amount of ferrite.Its solidification mode is liquid→liquid+δ-ferrite→liquid+δ-ferrite+γ-austenite→δ-ferrite+γ-austenite→γ-austenite.The equilibrium partition coefficient of element Al is greater than 1 and undergoes negative segregation by segregating into the dendrite interior of δ-ferrite.Mn,Nb,V,S and other solute elements undergo positive segregation and all of them are converged to interdendrite.AlN is mainly precipitated in dendrites and the precipitation temperature is 1 448 ℃,while MnS,enrichments of Nb and V are mainly precipitated in interdendrites.MnS and Nb-rich precipitates begin to precipitate above 1 400 ℃,while the precipitation temperature of enrichment of V is 760 ℃.