The results show that the fracture appearance of the bond is in the form of intergranular (IG) and quasicleavage (QC), and the proportion of QC increases with increasing preheating temperature.

• 结果表明：焊接熔合区断口为沿晶(IG)+准解理(QC)型，随着预热温度增加，QC比例增加；