核电用316奥氏体不锈钢钢丝扭转性能分析

Analysis on torsional properties of 316 austenitic stainless steel wire for nuclear power

针对核电用奥氏体不锈钢钢丝研制过程中存在的单向扭转性能不均匀及异常断裂问题,利用光学显微镜(OM)与扫描电镜(SEM)等手段,对该钢丝的金相组织、单向扭转断口及断口附近表面形貌进行了分析。研究发现,产生单向扭转性能不均匀与异常断裂的主要原因是钢丝表面质量较差及钢丝用钢棒焊接连接处局部过烧。通过将拉拔模具由钨钢模更换为聚晶模、润滑剂由润滑粉更换为水性油等措施,改善了钢丝表面质量;通过适当降低焊接接头处焊接时的热输入,消除了单向扭转时异常断裂的问题。改进后钢丝单向扭转圈数趋于均匀且最大扭转圈数可达169圈,远高于技术要求值。

Aiming at the problems of non-uniform unidirectional torsional properties and abnormal fracture in the development of austenitic stainless steel wire for nuclear power,the metallographic structure,unidirectional torsional fracture and surface morphology near the fracture were studied by means of optical microscope(OM)and scanning electron microscope(SEM).It is found that the main reasons for non-uniform of unidirectional torsional properties and abnormal fracture are the poor surface quality of steel wire and overburning at the welded joint of steel bar.By changing the drawing die material from tungsten steel to polycrystalline and the lubricant from lubricating powder to water-soluble grease,the surface quality of steel wire is improved.By reducing the heat input during welding at the welded joint properly,the problem of abnormal fracture in unidirectional torsion test is solved.After improvement,the unidirectional torsion turns tends to be uniform,and the maximum number of torsion turns can be up to 169,which is much higher than the technical requirements.