微量镁改善H13钢中碳化物的机理研究

H13热作模具钢属于中碳钢,钢中的Cr、Mo、V含量较高,因此钢在凝固过程中这些碳化物形成元素会偏聚析出大量的网状碳化物,经过热处理也很难完全消除,从而降低了钢的性能。实验室条件下研究了向H13钢中加入不同含量的镁对钢中碳化物的影响。结果表明:微量的镁能够改善H13钢中碳化物的形状和分布,使碳化物由粗大的网状转变成细小的短条状,经过镁处理后,碳化物呈细小均匀地分布在钢中。当加入0.004%的镁时,对碳化物的改质效果最好。镁在晶界处的偏聚是改善碳化物分布的主要原因,通过理论分析发现,在钢凝固冷却的过程中镁元素在晶界处的偏聚程度较高,从而阻碍了碳化物的生长,达到细化碳化物的目的。

Study on the Mechanism of Improving the Carbides in H13 Steel by Trace Magnesium

H13 hot working die steel belongs to medium carbon steel,which have high contents of Cr,Mo and V.Therefore,during solidification these carbide forming elements will be separated into a large number of network carbide,which is difficult to be completely eliminated by subsequent heat treatment.Thusthe performance of steel will be reduced.In this paper the effects of different contents of magnesium on the carbides in H13 steel had been studied.Metallurgical observations show that the shape and distribution of carbides in H13 steel can be improved by trace magnesium.The bulky reticulate carbide in steel is interrupted into tiny carbide.And the carbides distributed in H13 steel become fine and uniform after magnesium treatment.0.004％ magnesium additions can achieve the best result.The main reason for the improvement of carbide is magnesium segregation at grain boundaries.Through theoretical analysis,it is found out that the high degree of magnesium segregation at the grain boundaryduring solidification and cooling hinders the growth of carbides and then achieves the purpose of refining carbides.