对硅锰铸钢在相变温度（A1）附近进行等温处理的研究表明,经磁场处理后的试样组织中存在更多的粒状珠光体组织。此粒状珠光体由两部分构成：一部分来自块状铁素体中直接析出粒状的不连续渗碳体;一部分来自等温过程中片状渗碳体的熔断。磁场通过促进铁素体的形核与长大,使较多的碳原子＂陷落＂在铁素体内以沉淀析出方式形成粒状渗碳体,处理温度越低,此作用越明显。此外,磁场下珠光体组成相磁致伸缩率存在差异,引起珠光体两组成相之间的应变能变化,有利于渗碳体以球状析出于奥氏体或铁素体中,也对粒状珠光体分数的增加作出贡献。
Microstructure of Fe-Si-Mn casting steel isothermally treated at temperatures around A1 point under 12 T magnetic field was studied.The results show that there are more granular pearlite colonies in the microstructure of the samples by magnetic field treatment.The granular cementite in granular pearlite consists of two parts：granular cementite precipitated directly from ferrite matrix and discontinuous granular and short-rod cementite which is from the ＂fusing break＂ of the lamellar cementite during isothermal treatment.Magnetic field promotes the nucleation and growth of ferromagnetic phase-ferrite,so that more carbon atoms are ＂trapped＂ within the growing ferrite and form granular cementite later in the form of precipitation in ferrite matrix.The lower isothermal temperature is,the more obvious the effect is.In addition,magnetostriction between two constituent phases of pearlite is quite different under magnetic field,which causes the strain energy of both phases in pearlite to change in such a way that it benefits the cementite precipitation from austenite or ferrite in the shape of sphere and makes a contribution to the volume fraction of granular pearlite.
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