BWELDY700QL4低合金高强钢焊接接头组织与力学性能

摘要

Microstructure and properties of BWELDY700QL4 welding joint were investigated by tensile,bending,impact and hardness tests and metallographic analysis. The results show that tensile,bending and impact properties of the BWELDY700QL4 welding joint welded with YM80-A welding wire are excellent. The micro-structure in the weld metal contains vast proeutectoid ferrites that locate at grain boundaries, and carbon-free bainites in parallel arrangement which stretch from grain boundary into the grains, which present acicular ferrites and pearlites. Some granular bainites distribute at exceptional locations. The microstruclure in the fusion zone of welds contains lalh martensite and martensite-austensite group, and the normalized zone of the welds contains granular bainite and a little amount of ferrite. The hardness of the BWELDY700QL4 wels is between 264 and 380 HV,which is 48 -76 HV higher than parent metal.%通过拉伸、弯曲、冲击、硬度试验以及金相分析等对BWELDY700QL4低合金高强钢焊接接头的显微组织和力学性能进行了研究.结果表明:采用YM80-A焊丝焊接BWELDY700QL4低合金高强钢可以获得拉伸、弯曲和冲击性能均良好的焊接接头；其焊缝组织晶界为先共析铁素体、平行排列的无碳贝氏体从晶界伸向晶内,晶内为针状铁素体与珠光体,个别部位有粒状贝氏体.熔合区及粗晶区组织为板条马氏体和少量M-A组元.正火区组织为粒状贝氏体和少量铁素体.BWELDY700QL4焊接接头的硬度值在264～380 HV之间,焊缝处硬度最高,比母材高48 ～76 HV,热影响区虽有软化现象,但不明显.