CAJ | 학술논문

7050铝合金在半连铸生产过程中发生热裂和冷裂的倾向很高，不但影响了产品的质量和生产效率，还可能导致生产事故。工厂常采用试错法以找到最优的工艺参数，但这种方法成本高且效率低。运用数值模拟的方法再现铸造过程中各物理场的变化情况，已成为优化铝合金熔铸工艺非常重要的研究手段。本文通过将温度场、流场和应力场进行直接耦合，对7050铝合金的半连铸过程进行了数值模拟研究。结果显示，在糊状区沿铸锭宽度方向的应力和应变分量最大，特别是在起始铸造阶段，因而最容易在起始阶段产生垂直于宽度方向的热裂纹。冷裂与铸锭内应力集中有关，根据计算可知铸锭在冷却至200℃时冷裂倾向最大。由实际裂纹所处的部位及所需的临界尺寸可以推测，该冷裂纹极有可能是糊状区产生的热裂纹在低温时失稳扩展而形成的。
7050려합금재반련주생산과정중발생열렬화랭렬적경향흔고，불단영향료산품적질량화생산효솔，환가능도치생산사고。공엄상채용시착법이조도최우적공예삼수，단저충방법성본고차효솔저。운용수치모의적방법재현주조과정중각물리장적변화정황，이성위우화려합금용주공예비상중요적연구수단。본문통과장온도장、류장화응력장진행직접우합，대7050려합금적반련주과정진행료수치모의연구。결과현시，재호상구연주정관도방향적응력화응변분량최대，특별시재기시주조계단，인이최용역재기시계단산생수직우관도방향적열렬문。랭렬여주정내응력집중유관，근거계산가지주정재냉각지200℃시랭렬경향최대。유실제렬문소처적부위급소수적림계척촌가이추측，해랭렬문겁유가능시호상구산생적열렬문재저온시실은확전이형성적。
AA7050 alloy has a very high hot tearing and cold cracking tendency during direct-chill casting, which can affect its product quality and productivity, even cause industrial accidents. The trial and error method is often used in a foundry factory to find the optimum process parameters. However, this kind of approach is very costly and inefficient. Numerical modeling can reproduce the evolution of multi-physical fields in direct-chill casting, and it has been proved to be an indispensable tool in improving the casting process of aluminum alloys. In this paper, a direct-chill casting process of AA7050 alloy was simulated through direct coupling of ther-mal, fluid flow and stress fields. Simulation results showed that in the mushy zone the largest stress and strain components could be observed in the width direction, especially at the start-up phase. As a result, hot tearing perpendicular to the width direction was most likely to occur at this stage. The formation of cold cracking was closely related to stress concentration in the ingot, and the highest cold cracking tendency can be seen when the ingot was cooled to 200 ℃ . According to the position of the cold crack in the ingot and the critical crack size needed, a speculation could be made that the cold crack was possibly caused by the further propagation of hot tearing at lower temperatures.