大长径比超细WC-Co圆棒PIM充模过程的数值模拟

Numerical Simulation of PIM Filling Process of Ultra-fine WC-Co Round Bar with Large Aspect Ratio

摘要:

基于计算流体动力学的粉末-粘结剂双流体模型，采用CFX商业软件对大长径比超细WC/10Co粉末注射成形（PIM）充模过程进行数值模拟。结果表明：数值模拟结果与实际充模过程相一致，其假设条件和参数设置具有合理性，双流体模型具有可行性；粉末与粘结剂的温度分布一致，喂料熔体最低温度（≥330 K）高于粘结剂的玻璃化温度，不发生凝固现象；粉末的粘度为50.0~379.4 Pa·s，粘结剂的粘度为2.9~9.2 Pa·s，粘度差是造成偏析现象的主要原因；从浇口处到模壁处，粉末与粘结剂的相对速度差从0.2%增加到1.8%，从浇口处到远端，相对速度差从0.1%增大到1.6%，相对速度差是引起偏析现象的主要原因。

Abstract:

Based on the powder-binder two-fluid model, the filling process was simulated by CFX commercial software, especially for the ultra-fine WC/10Co round bar with large aspect ratio by powder injection molding (PIM). The results indicated that the numerical simulation results are almost consistent with the experimental filling process, which proves that the hypothesis and parameter settings are reasonable and the two-fluid model is feasible. Also there is no great difference in temperature distribution between powder and binder. There is no solidification for melting feedstock, which due to that the lowest temperature valued 330 K of melting feedstock is higher than the vitrification temperature of binder. In addition, there is great difference in the viscosity between powder and binder, valued 50.0 ~379.4 Pa·s, 2.9~9.2 Pa·s, respectively, which is one cause for segregation. Finally, it is also another main cause for segregation that the relative velocity difference between powder and binder increases up remarkably, such as 0.2% up 1.8% from gate to die wall, 0.1% up 1.6% from gate to far end.