高氮钢复合焊接接头组织与力学性能研究

摘要

Heat input had a significant effect on microstructure and mechanics properties of wel-ded j oint.The j oint microstructure,weld nitrogen content,tensile and impacted properties and the micro hardness of j oint were studied by laser-arc hybrid welding while the arc and laser energy were different.The results show that the weld microstructure is made up of austenite and a small amount ofδferrite.The delta ferrite deposited from weld is increased by the increasing heat input.After the cur-rent reaches 200 A,the dissolution of nitrogen in liquid metal molten pool is close to saturation;and even if the welding current is added,the weld nitrogen content still tends to be constant.When the la-ser power is increased to 2.0 kW,keyhole remains at a stable state in the welding processes,and weld nitrogen content is approximate to constant.Tensile fracture location is in the weld zone.When the welding current is as 200 A,the highest average tensile strength reaches 967.58 MPa.When laser power is as 1.6 kW,the average tensile strength may reach 962.88 MPa.The weld impact energy shows a first decrease and then increase with increasing laser power,but the variation tendency is op-posite along with increasing current.The variation tendency of impact energy of the weld fusion line is the same as that of the weld zone and changes with the welding parameters.The highest average im-pact energy of the weld and the weld fusion line are as 47.60 J and 62.85 J separately.All tensile and impacted fracture mode is of ductile fracture.The micro hardness of weld area is lowest so that the fracture area of tensile test is located at the weld zone.%热输入对焊接接头组织与力学性能有重要影响.采用激光电弧复合焊接方法,研究了不同电弧能量和激光能量下的接头组织、焊缝氮含量、拉伸与冲击性能及接头显微硬度.研究表明：焊缝组织为奥氏体＋少量δ铁素体,焊缝中析出的δ铁素体随热输入加大而增多；当电流达到200 A后,熔池液态金属中氮的溶解近于饱和,即使焊接电流增大,焊缝氮含量依然趋于恒定；而当激光功率增至2．0 kW后,焊接过程中的匙孔维持在稳定状态,焊缝氮含量也近于恒定；拉伸断裂位置均在焊缝区,当焊接电流为200 A时,平均拉伸强度最高,达到967．58 MPa,当激光功率为1．6 kW时,平均拉伸强度可达962．88 MPa；焊缝冲击功随激光功率的增大呈先降低后升高的变化趋势,但随电流的增大其变化趋势相反；熔合线的冲击功随着焊接参数的变化呈现出相同的变化趋势,焊缝和熔合线的最大平均冲击功分别为47．60 J 和62．85 J；拉伸和冲击的断裂形式均为韧性断裂；焊缝区显微硬度最低,导致拉伸测试时均断裂于焊缝区.