基于双亚点阵模型对H13钢中初生碳氮化物的研究

实验证明H13钢中存在三类初生碳氮化物,包括富V和C的(Vx,Mo1x)(Cy,N1-y)、富Ti和N的(Tix,V1x)(Cy,N1-y)及富V和C的(Tix,V1-x)(Cy,N1-y),部分存在形核核心.基于双亚点阵模型和凝固偏析模型分析计算H13钢凝固过程中元素含量变化,考虑初生碳氮化物中元素间的相互作用,根据三类碳氮化物中合金元素含量和C/N比值不同,对各碳氮化物的生成自由能进行分析.理论研究指出富Ti和N的(Tix,V1-x)(Cy,N1-y)在固相率为0.90时即可生成,而富V和C的(Tix,V1-x)(Cx,N1-y)在固相率大于0.96才可生成,两类碳氮化物的临界生成固相率fP均随固溶Ti和N含量的增加而减小.(Vx,Mo1-x)(Cy,N1-y)的临界生成固相率与x值密切相关,x减小时fP降低,粒子尺寸增加,实验与理论分析吻合良好.根据错配度分析氧化物和碳氮化物对H13钢中初生碳氮化物异质形核的作用.

Study on primary carbonitrides in H13 steel based on the two-sublattice model

Three kinds of primary carbonitrides were classified in H13 hot work die steel through experiment,including (Vx,Mo1-x)(Cy,N1-y) rich inVandC,(Tix,V1-x)(Cy,N1-y) rich inTi and N,and (Tix,V1 x)(Cyy,N1-y) rich in V and C,some having a core in the center.The element variation and Gibbs energy of the carbonitrides during H13 solidification were analyzed based on the solidification segregation model and the two-sublattice model,taking the interaction between components into account as well as the alloying element content and C/N ratio of the three types of primary carbonitrides.It is found that Ti-and N-rich (Tix,V1-x) (Cy,N1-y) forms when the solid fraction reaches 0.9,while the other V-and C-rich (Tix,V1-x) (Cy,N1-y) generates when the solid fraction is greater than 0.96 during solidification.The critical solid fraction for the formation of these two (Tix,V1-x) (Cy,N1-y) decreases with increasing Ti and N contents soluted in the carbonitrides.The formation of (Vx,Mo1-x) (Cy,N1-y) during solidification can be affected by the x value.The critical solid fraction decreases as less vanadium is soluted in (Vx,Mo1-x) (Cy,N1-y),leading to larger size carbonitridcs demonstrated by the models,which fit well with experimental data.The influence of oxides and carbonitrides on heterogeneous nucleation for the carbonitrides was also researched through lattice misfitting analysis.