Q235B钢管的断裂失效分析

Fracturing failure analysis of Q235B steel tube

Q235B碳素钢通信塔用钢管在矫直过程中出现焊接处断裂。用扫描电镜、光学显微镜、力学性能测试等方法,对断裂构件化学成分和力学性能进行检测。选择加热温度为920、940、950℃和保温时间2、3、4 h对试样进行正火处理,并对热处理后的试样进行显微组织观察、力学性能测试和冲击试验,比较并确定最佳的正火工艺。结果表明,Q235B钢原始组织呈带状分布。在钢管矫直过程中,焊接处出现应力集中,导致其发生脆性开裂。采用920℃×3 h、920℃×4 h或950℃×2 h的正火工艺可以消除此类问题。

Fracture of Q235B carbon steel tube for communication tower appeared in welding place during straightening process.Chemical composition and mechanical properties of the fracturing workpiece were tested by scanning electron microscope（SEM）,optical microscope,and mechanical properties test.Normalizing treatment on the specimen heated at 920,940,950 ℃ and holding for 2,3,4 h were selected,respectively.Microstructure observation,mechanical properties and impact energy test of specimens after heat treatment were conducted.The best optimal normalizing treatment process was compared and determined.The results show that there is banded structure in the original microstructure of the Q235B steel.In the straightening process,the stress in the welding place is concentrated and leads to brittle fracture.The normalizing process of 920 ℃×3 h,920 ℃×4 h or 950 ℃×2 h can eliminate such failures.