Q345/316L异种钢K-TIG焊接接头的组织及性能

Microstructure and properties of K-TIG welded joint of Q345/316L dissimilar steel

采用K-TIG焊接方法对Q345/316L异种钢进行焊接试验,并利用光学显微镜、扫描电镜、万能试验机、冲击试验机、显微硬度仪等观察和分析焊接接头的显微组织及力学性能。结果表明:靠近316L侧焊缝组织为奥氏体及骨骼状铁素体,呈柱状晶分布,靠近Q345侧焊缝组织为板条马氏体。316L侧形成宽约45~50μm的熔合区,由细小的蠕虫状铁素体呈无方向且不连续的分布在奥氏体基体上。Q345侧熔合区产生魏氏组织,过热区晶粒粗大且有索氏体生成,相变重结晶区晶粒细小。拉伸断裂位置均发生在Q345侧母材。焊接接头冲击韧性良好,断裂位置均在Q345热影响区,断口为韧脆混合准解理断裂,有韧窝、河流花样、解理台阶。焊缝显微硬度明显高于两侧热影响区及母材。

K-TIG welding method was used to carry out welding test on Q345/316L dissimilar steel,and optical micr-oscope,scanning electron microscope,universal testing machine,impact testing machine,microhardness tester,were used to study the microstructure and mechanical properties of welded joints.The results show that the weld microstructure close to 316L is austenite and skeletal ferrite with columnar crystal distribution,and the weld microstructure close to Q345 is lath martensite.On the 316L side,a fusion zone about 45~50 m wide is formed,and the tiny vermicular ferrite is distributed on the austenite matrix without direction and discontinuously.The fusion zone on the Q345 side produces the Widmanstatten structure,the superheated zone has the formation of sorbite and the phase change recrystallization zone has the fine grain.The tensile fracture occurred at the base material of Q345 side.The joint welds have good impact toughness,and the fracture locations are all in the heat-affected zone of Q345.The fracture surface is ductile and brittle mixed quasi-cleavage fracture with dimples,river pattern and cleavage steps.The microhardness of weld is obviously higher than that of the heat-affected zone and base material on both sides.