焊接热输入与焊材成分对管道环焊缝抗氢脆性能影响研究OA

To investigate the effects of filler metal and welding process on hydrogen embrittlement resistance of girth welds.Solid welding wires with different contents of Cu and Ti microalloying elements were adopted,and fully automatic girth welds were fabricated under different welding heat inputs.Microstructure observation,EBSD analysis and slow strain rate tensile(SSRT)tests were carried out to explore the synergistic influence of welding heat input and filler metal composition on the microstructure,grain boundary characteristics and hydrogen embrittlement susceptibility of pipeline girth welds.The results show that under similar heat input,the girth welds using No.2 filler metal present higher hydrogen embrittlement susceptibility than those using No.1 filler metal.With the reduction of heat input,the hydrogen embrittlement susceptibility of girth welds with No.1 filler metal decreases remarkably.This is mainly because No.1 filler metal rich in Mn,Cu and Ti promotes the formation of acicular ferrite(AF)in weld metal.Acicular ferrite is dominated by high-angle grain boundaries with fine grains,which can effectively deflect and hinder the propagation of hydrogen-induced cracks.For girth welds of No.2 filler metal welded with relatively high heat input,the content of polygonal ferrite(PF)and Widmanstätten ferrite(WF)in microstructure increases obviously.Polygonal ferrite and Widmanstätten ferrite have coarse grains and are mainly composed of low-angle grain boundaries,leading to poor crack resistance.In conclusion,selecting filler metals containing abundant Mn,Mo,Cu,Ti and other elements,together with lower welding heat input and faster welding cooling rate,is beneficial to obtaining girth weld microstructure with excellent hydrogen embrittlement resistance.