基于有限元模拟的大口径钛合金无缝管材压扁开裂研究

Cracking Analysis of Large-diameter Titanium Alloy Seamless Pipes during Flattening Based on Finite Element Simulation

大口径Ti-4Al-3Mo-1V钛合金无缝管材在进行压扁工艺试验时,压扁环内壁出现开裂现象。采用有限元模拟和显微硬度检测等方法,研究影响大口径钛合金管材压扁性能的因素。结果表明:压扁环6点钟和12点钟位置内表面由于承受较大的拉应力而优先出现裂纹;大口径钛合金管材压扁开裂的主要原因是钛合金管材表面在热处理过程中形成一层氧化膜,导致管材表面硬度增加,进而引发局部应力集中。通过酸洗去除管材表面硬化层可避免压扁开裂。

During the flattening test of large-diameter Ti-4Al-3Mo-1V titanium alloy seamless pipes,cracking occurred in the inner wall of the flattened rings.The factors affecting the flattening performance of large-diameter titanium alloy pipes were studied by finite element simulation and microhardness testing.The results show that cracks are inclined to form at the positions of 6 oʼclock and 12 oʼclock of the inner surface of the flattened rings due to higher tensile stress.The main reason for the flattening cracking of the pipes is that the oxide film formed on the surface of the pipes during heat treatment,leading to the increase of surface hardness,which in turn resulted in local stress concentration.Removing the hardened layer on the pipes’surface through acid washing can avoid cracking during flattening.