基于加工图的新型钛合金斜轧穿孔温度预测

A new marine titanium alloy Ti80 was isothermally compressed on a Gleeble-3500 thermal simulator. The variation of flow stress under different processing parameters was studied and the elevated temperature constitutive equation and processing map were established. Based on the analysis of high power dissipation efficiency in safe region, the initial temperature of the bar stock was preliminarily determined as Ti80 alloy seamless tube was prepared through rotary piercing process. Finally, the estimation was verified by 3D thermo-mechanical coupled simulation as well as physical experiment. Results show that the sensitivity of flow stress of Ti80 alloy to the temperature varies under different strain rates. The flow stress increases sharply with the decreasing of temperature in α+β phase field; while there is slight difference in single β phase field. Taking strain compensation into consideration, the modified hyperbolic-sine Arrhenius type equation could give an accurate estimation of flow stress for hot deformation of Ti80 titanium alloy. The developed processing map shows two high power dissipation efficiency domains: one is in α+β phase field with low strain rate, i.e. 925~975℃/0.01~0.1 s^-1; the other is in the β phase field with intermediate strain rate, i.e. 1050~1100℃/0.1~1 s^-1. Finite element simulation for rotary piercing process was further conducted at initial temperature of 950, 1050 and 1100℃ for bar stocks. It is found that the plug force at temperature of 950℃ increases significantly to about 5~6 times higher than that in single β phase field, and what is worse, piercing in α+β phase field leads to rolled stock jamming in Diescher's mill. However, the piercing process in β phase field can be conducted well. For reducing energy consumption, the temperature of 1050℃ is considered as the optimal choice. In the end, Ti80 alloy seamless tube was produced successfully in Diescher's mill.