大口径厚壁管热挤压过程中晶粒组织均匀性数值模拟

Numerical simulation on homogeneity of grain structure for large diameter and thick wall pipes during hot extrusion process

通过对Deform-3D软件二次开发,模拟研究了新型节镍奥氏体耐热钢21Cr-11Ni-N-RE大口径厚壁管热挤压过程中晶粒演变规律,并引入晶粒组织不均匀因子Z,评估了不同坯料预热温度、挤压速度、挤压比下晶粒组织均匀性。结果表明:增加坯料预热温度、提高挤压速度、增大挤压比均使得晶粒组织不均匀因子Z降低,即有利于提高晶粒组织均匀性。通过正交优化合理选择了热挤压参数,并实际获得了具有均匀晶粒组织的大口径厚壁管。晶粒组织的有限元模拟结果与实际测量值吻合较好,验证了有限元模型的正确性与可靠性。

The evolution of the grain size of large diameter and thick wall pipe of 21Cr-11Ni-N-RE lean austenitic heat-resistant steel was simulated during hot extrusion process by using the secondary developed software Deform-3D. In order to evaluate the microstructure homogeneity at different conditions,such as initial billet temperature,extrusion speed and extrusion ratio,non-uniform factor Z was introduced. The results show that non-uniform factor Z decreases with the increasing initial billet temperature,the extrusion speed and the extrusion ratio,namely,the grain structure becomes uniform in this way. Hot extrusion parameters were selected with the orthogonal experiment methods and the large diameter and thick wall pipe with homogeneous microstructure was obtained. A good agreement between the finite element results and the experimental results is achieved,which verifies the accuracy and reliability of the finite element model.