冷速对20MnCr5齿轮钢凝固偏析影响

Effect of cooling speed on solidification segregation in 20MnCr5 gear steel

齿轮钢作为航空航天、铁路运输和机械传动等领域的关键材料,其性能直接影响齿轮的使用寿命和可靠性。针对齿轮钢在较低冷却速率凝固时带状组织会使其性能恶化的问题,通过原位激光共聚焦扫描显微镜(CLSM)、电子探针X射线显微分析仪(EPMA)以及JMatPro软件等多种试验和理论计算相结合的方法,对20MnCr5齿轮钢在不同冷却速率下微观结构和溶质元素的微观偏析行为进行了探究。结果表明,随着冷却速率的加快,二次枝晶臂间距由318.63μm减小至138.08μm。20MnCr5齿轮钢凝固过程中,主要发生L→L+δ→γ的相变。随着温度的降低,铬和锰元素在晶界处有偏聚的倾向,同时,MnS、TiN和碳化物等相继析出。构建了一个溶质元素微观偏析模型,预测了齿轮钢凝固过程中元素的偏析行为,其结果与EPMA面扫元素分布一致,可为连铸工艺优化控制与铸坯质量控制提供依据。

Gear steel,as a key material in aerospace,railroad transportation and mechanical transmission,its performance directly affects the service life and reliability of gears.Aiming at the properties deterioration problem of gear steel due to banded organization during solidification at lower cooling rates,the microstructure and microsegregation behavior of solute elements of 20MnCr5 gear steel at different cooling rates were investigated by a combination of experimental and theoretical calculations using in-situ laser confocal scanning microscopy(CLSM),electron probe X-ray microanalysis(EPMA),and JMatPro software.The results show that the secondary dendrite arm spacing decreases from 318.63μm to 138.08μm with the acceleration of the cooling rate.During the solidification process of 20MnCr5 gear steel,the phase transformation of L→L+δ→γmainly occurs.With the decrease of temperature,chromium and manganese elements have a tendency to be polarized at the grain boundaries,while MnS,TiN and carbides are precipitated successively.A microscopic segregation model of solute elements is constructed to predict the segregation behavior of elements in the solidification process of gear steel,and the results are consistent with the distribution of elements in the EPMA surface sweep,which provides a basis for the optimal control of the continuous casting process and the quality control of billet casting.