连铸法Gasar工艺中抽拉速率对多孔金属结构影响的理论分析

THEORETICAL ANALYSIS ON EFFECT OF TRANSFERENCE VELOCITY ON STRUCTURE OF POROUS METALS FABRICATED BY CONTINUOUS CASTING GASAR PROCESS

通过求解凝固界面前沿熔体中的溶质浓度场方程,从理论上建立了一个用于描述连铸法Gasar工艺中的工艺参数对藕状多孔金属结构平均孔径、孔间距以及气孔率影响的理论模型,并将抽拉速率对多孔金属结构的影响的理论预测结果与文献中相应实验结果进行比较,结果表明,理论预测结果与实验结果吻合较好.预测结果显示,平均孔径r_g和孔间距L随抽拉速率v的升高不断降低,但气孔率变化较小,它们之间存在着简单关系为:r_g^(1.72)·v=A和L^(1.72)·v=B(其中,A和B都是取决于气体压力pH_2和pA_r以及熔体温度T的常数)。

Transference velocity is an important processing parameter to influence the final lotus type porous structure fabricated by continuous casting Gasar process.Via solving the solute diffusion equation,a theoretical model was developed to predict the effect of the transference velocity on the porosity,the pore diameter and the inter pore spacing.The predicted values at different transference velocities have a good agreement with the corresponding experimental results obtained by Japanese researcher.The average pore diameter and the inter pore spacing L both have a prominent decrease with the increase of transference velocity v,but the porosity only has a slight decrease.The theoretical relationships between the pore radius rg,the inter-pore spacing and the transference velocity can be described by the two simple equations as rg1.72·v=A and L1.72·v = B,where A and B are all constants depending on the used gas pressures and the melt temperature.