从厚壁铸钢件链轮的品质攻关看顺序凝固中温度梯度的重要性

The Important Function of Temperature Gradient in Designing Foundry Technology of Steel Casting with Heavy Wall Thickness

对精加工表面磁粉探伤后出现大量微细磁痕的铸钢大链轮的原铸造工艺进行了凝固数值模拟分析 ,认为缺陷是由于顺序凝固方向上温度梯度过于平缓所致的微小缩松 ,对缺陷部位进行纵横截面的切片金相分析印证了模拟分析是正确的。据此 ,本着增大凝固方向上的温度梯度的原则用数值模拟技术进行了 15种方案的工艺优化计算并结合现场生产确定了优化方案 ,实际浇注结果表明 ,方案是成功的。进一步讨论说明 ,要获得致密的铸钢基体 ,在铸造工艺设计中应注意使凝固方向上的温度梯度足够大 。

The numerical simulation result for a big steel casting chain wheel, which has been disclosed large number of MT thin lines on its teeth and groove, showed that its imperfection was micro-porosity. To our viewpoint, the low temperature gradient across solid/liquid interface give rise to this kind of imperfect, that was then verified by an metallographic analysis through getting slices in the tangential and cross section on the chain wheel's imperfection site. On this basis, to increase the temperature gradient to select better cast technology, 15 foundry plots had been simulated, and the corresponding pouring castings showed that the selected plan is excellent. The study enlightens that to get the sound steel casting, the temperature in the solidification direction should be big enough to make the solid/liquid interface solidifies near layer by layer mode.