铁路货车用TCS345不锈钢焊接热影响区韧性分析

Analysis on heat-affected zone toughness of railroad freight TCS345 stainless steel weld joints

利用Thermol-cal软件获得一定成分体系下铁路货车用12%Cr铁素体不锈钢的相图,结合相图对12%Cr铁素体不锈钢的焊接过程进行分析.利用光学显微镜、扫描电镜分析12%Cr铁素体不锈钢的焊接热影响区为铁素体和马氏体以及碳、氮化物组成的粗晶区和细晶区两部分.结果表明,铁素体晶粒的尺寸与马氏体的含量是影响热影响粗晶区韧性的主要因素.当母材中的碳、氮化物颗粒尺寸在2-5μm时,具有最优的冲击性能; 当母材中碳＋氮含量为0.02%左右时,在文中试验条件下粗晶区的马氏体含量为40%,焊接接头粗晶区具有-22℃的最低韧脆转变温度.

The transformation temperature phase diagram of 12% chromium steel is obtained by using Thermal-cal software.Process of welding 12% chromium stainless steel is analysed with the phase transformation temperature scope.The heat-affected zone(HAZ) of the weld joints is observed with optic microscope and scanning electronic microscope,which the microstructure consists of ferrite,martensite,coarse grain heat-affected zone(CGHAZ),fine grain heat-affected zone(FGHAZ) and Ti(C/N).The key elements that affect toughness of CGHAZ are ferritic grain size and martensitic content.The base material has the best impact toughness when grain size of Ti(C/N) reaches 2-5 μm.The lowest ductility-brittle transition temperature in CGHAZ is-22 ℃ when content of carbon plus nitrogen in base material is about 0.02% and martensitic content in CGHAZ is 40% under some certain welding procedure.