不同线能量对高强钢SX780CF埋弧焊接头的影响

Influence of different heat input on submerged arc welded joints of high strength low alloy steel SX780CF

SX780CF是一种新型国产800 MPa级别低碳调质高强钢,首次应用于大型水电压力钢管制造工程。为了提高焊接效率,采用埋弧焊进行焊接。对SX780CF的埋弧焊接进行20~25 kJ/cm及35~40 kJ/cm不同线能量级别的试验,分析焊接接头的力学性能、接头不均匀性及微观金相。结果表明,采用两种线能量焊接的接头的力学性能均能满足标准GB 50766-2012要求;SX780CF淬硬倾向较小,厚度为60 mm时需预热80℃以上;为提高焊接生产效率,减少制造成本,可采用较大线能量焊接。

SX780CF is a new type domestic800MPa high strength low alloy(HSLA)steel,which was used firstly for pressure pipes in the hydropower unit.In order to improve the efficiency,SX780CF is generally welded by SAW.In this paper,two different levels of heat-input are used to weld B780CF.The two joints'weldability is analyzed,the mechanical properties of the joints are measured,and the hardness distribution of the joints is tested.Meanwhile,the microstructure is observed.The results show that the properties of these joints welded by two different level's of heat-input could satisfy the demand of the GB50766-2012standard.SX780CF's hardened tendency is small.The thickness of60mm needs to be preheated at more than80℃.To improve welding efficiency and reduce cost,the larger heat input could be used.