大型水轮机主轴锻造过程裂纹缺陷的预防

Prevention of forging cracks in heavy hydro-generator shafts

针对大型水轮机主轴内法兰锻件锻造过程的裂纹缺陷,采用热力学实验方法,研究了其主要用钢20SiMn的高温力学性能。结果表明,提高变形温度和降低变形速率有利于避免该材料内部裂纹萌生。根据Cockcroft&Latham延性断裂准则,计算得到了20SiMn钢的延性断裂破坏因子为30.0。利用Deform 3D软件,对大型水轮机主轴内法兰锻造过程进行了数值模拟,预测了该类锻件在空心镦粗过程中裂纹产生的趋势和区域,并提出将单砧压下量控制在8%以内和将镦粗变形量控制在45%的局部空心镦粗优化锻造工艺方案。

The high-temperature mechanical properties of the 20SiMn steel used in heavy hydro-generator shafts where forging cracks often occur were measured experimentally. The results show that higher temperatures and lower strain rates help prevent the initiation of forging cracks. The experimental data was analyzed based on the Cockcroft ~ Latham ductile fracture criterion to give a calculational damage parameter of 30.0. The flange forging process for a heavy hydro-generator shaft was simulated using Deform 3D to predict the crack initiation trends and zones in a hollow upsetting process. The optimum forging design is recommended to use a press distance variation rate of less than 8% in a single step and less than 45% in the local hollow upsetting process.