ULCB钢焊接熔池CET转变数值模拟研究

Numerical simulation on CET transformation of ULCB steel in welding molten pool

基于元胞自动机法和有限差分法(CA-FD)建立ULCB钢熔池凝固枝晶生长的数值模型,应用该模型模拟ULCB钢埋弧焊对接接头熔池凝固时,初生柱状晶结晶转变为次生等轴晶结晶过程中的枝晶生长与溶质浓度的变化。结果表明:焊接熔池凝固开始时,初生柱状晶间竞争生长激烈,主干枝晶长大方向同于温度梯度较大的方向,且生长速度较快;其他方向受抑制较严重,但在竞争中慢速持续生长;同时,在初生枝晶与初生枝晶臂之间、初生柱状晶与次生等轴晶之间的残余液相中,溶质积累,凝固过程结束后形成严重的枝晶偏析。

Based on cellular automata method and finite difference method(CA-FD),a numerical model for the microstructure of ultra low carbon(ULCB)steel in welding molten pool during solidification process was developed.During the columnar-toequiaxed transition in the solidification of weld pool of submerged arc welding butt joint of ULCB steel,the model was used to simulate the dendritic growth morphology and the distribution of the solute concentration.The simulation results show that:At the beginning of weld pool solidification,the primary columnar crystals grow in fierce competition,the main dendritic growth direction is the same as the direction of higher temperature gradient,and the growth rate is faster;At other directions,the dendritic growth are severely inhibited,but the dendrites grow slowly and continuously in competition;At the same time,between primary dendrite and primary dendritic arm,primary columnar crystal and secondary equiaxed crystal,solute accumulation occurrs in the residual liquid phase,and serious dendritic segregation is formed after solidification.