斜轧穿孔法制备Ti80合金无缝管工艺分析  

Rotary Piercing Technique of Ti80 Titanium Alloy Seamless Tube

作　　者：周大地 曾卫东[1] 徐建伟[1] Zhou Dadi;Zeng Weidong;Xu Jianwei(State Key Laboratory of Solidification Processing,Northwest Polytechnical University,Xi'an 710072,China)

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《稀有金属材料与工程》2020年第3期1045-1050,共6页Rare Metal Materials and Engineering

基　　金：国家重点研发计划(2016YFB0301203)。

摘　　要：运用有限元技术模拟了两辊斜轧穿孔法制备Ti80合金无缝管坯的三维热力耦合过程。仿真结果能动态显示坯料从咬入到稳定穿孔再到穿出3个阶段复杂的塑性成形过程,并能辅助分析中心孔腔的形成机理以及坯料在穿孔阶段各物理场量的分布。结果表明:坯料刚接触顶头时,中心金属存在明显塑性变形,结合轧制中心线上不同方向的正应力状态为(+,-,+),判断中心孔腔的形成为拉应力作用下的塑性开裂。在穿孔过程中,坯料的应变分布沿轴向呈U1+W+2U2形态,沿径向为片层状,最终穿制毛管等效应变可达5~11;坯料的外表面与导盘接触区应变速率为0.71~3.6s-1,而与轧辊接触区高达4.6~26s-1,大的应变速率有助于毛管的塑性成形过程;顶头前坯料的温度最高,与穿孔工具接触的区域温度略有降低,但绝大部分变形区温度都处于单相区。模拟所得全流程顶头轴向力与轧制力的变化呈现典型的3阶段分布,其中稳定穿孔阶段力能参数的均值接近试验所得,从而验证了模型的准确性。基于有限元模拟的工艺条件,在实验轧机上一火次顺利穿制出Ti80合金无缝管坯,其显微组织展现为单一的魏氏组织形态,且由于变形剧烈,从外表面到中间层再到内表面均为等轴细小的β动态再结晶晶粒;力学性能测试表明该组织状态下的毛管的强度和塑性均满足指标要求。This paper deals with the simulation of rotary piercing process of Ti80 alloy seamless tube via a 3 D thermal-mechanical coupling finite element model(FEM). The model can visualize the complex continuous piercing process from biting to steady piercing and to final drilling. Concurrently, the simulated results help to understand the mechanism of central fracturing as well as the distribution of physical fields. Combining normal stress state of(+,-, +) along the rolling centerline with non-negligible plastic deformation at the centre of the billet, the cavity formation was determined to be caused by plastic cracking under tensile stress. During the piercing process, the strain distribution was U1+W+2 U2 along the axial direction and lamellar along the radial direction. The final equivalent strain of the hollow billet could reach 5~11. The strain rate in contact area between the blank surface and the discs was 0.71~3.6 s-1, while that between the surface and the rolls was up to 4.6~26 s-1. The relatively high strain rate was beneficial to the plastic deformation of raw material. The billet temperature in front of the plug was the highest, and the area in contact with the piercing tools decreased slightly. However, the vast majority of the billet in deformation zone was still in the single β phase field. Additionally, the loads on the plug and roll in the whole piercing process presented a typical three-stage distribution. The mean values in the stable phase were close to the experimental researches, which demonstrated the accuracy of the model. Based on the simulation of finite element method, the Ti80 alloy seamless tube has been successfully pierced through the experimental Diescher’s mill. The microstructure of the tube was illustrated as a single Widmanstatten microstructure. Due to the severe deformation, the finer and equiaxed dynamic recrystallization β grains were formed from outer surface to the middle layer and to inner surface. The mechanical property test show that the strength and plasticity of the

关 键 词：Ti80合金 狄舍尔穿孔机 三维热力耦合有限元模型 实验验证 力学性能 

分 类 号：TG146.23[一般工业技术—材料科学与工程]