微镁处理对车轮钢组织与性能的调控作用

Effect of magnesium addition on microstructure and mechanical properties in wheel steel

为揭示Mg在低碳微合金钢中的作用,以HR60车轮钢为研究对象,分别进行实验室感应炉试验和工业试验。采用OM、SEM-EDS和INCA定量统计等方法对比不同处理钢中典型夹杂物特征和微观组织形貌,并对试验钢的力学性能进行测定。结果表明：Mg处理后,钢中Al2O3夹杂变质为细小的MgO·Al2O3夹杂物,且含Mg夹杂物粒子可有效诱导针状铁素体形核,组织由＂多边形铁素体（PF）＋珠光体（P）＂向＂多边形铁素体（PF）＋针状铁素体（AF）＋退化珠光体（DP）＂演变,组织得到细化;Mg处理后,车轮钢强度提高,工业试验钢中,Mg处理钢疲劳极限均大于460MPa,Ca处理钢疲劳极限在450MPa左右,Mg处理钢的疲劳寿命普遍优于Ca处理钢;实验室试验中,降低Nb、Ti含量,当钢中Mg的质量分数为18×10-6时,车轮钢的强度接近基准钢,认为利用Mg的微合金化作用来降低生产成本的方案具有可行性。

In order to reveal the effect of Mg in low carbon microalloy steel,low carbon microalloy steel of HR60 wheel steel was smelted in vacuum induction furnace and industrial field respectively.The characteristics of typical non-metallic inclusions and microstructure of experimental steels were both compared by OM,SEM-EDS and INCA Feature with automatically scanning inclusions function.The mechanical properties of the experimental steels were also measured.The results show that alumina inclusions are modified to spinel inclusions with small size after Mg addition.Furthermore,acicular ferrite can be induced effectively by inclusions containing magnesium.The microstructures of experimental steels are changed from ‘polygonal ferrite（PF）＋ pearlite（P）＇to‘polygonal ferrite（PF）＋ degenerate pearlite（DP）＋acicular ferrite（AF）＇and refined by Mg treatment.The strength of experimental steels is improved with Mg addition.In industrial experiments,the fatigue limit of Mg-treated steels is greater than 460 MPa,while the fatigue limit of Ca-treated steels is about 450 MPa.In addition,the fatigue life of Mg-treated steels is generally higher than that of Ca-treated steels under the condition that the stress is greater than the fatigue limit.In laboratory experiments,the contents of Nb and Ti are reduced while Mg content in steel is 18×10-6,the strength of the wheel steel is close to the reference steel.Therefore,the project to reducing production cost by taking advantage of the microalloy role of Mg is feasible.