B含量对不同强度级别焊缝组织及冲击韧性的影响

Effect of boron on microstructure and impact toughness of weld joint with different strength grade

通过实验室埋弧焊焊接试验,制备了3种不同强度级别有无B的焊缝金属,研究分析了B元素对不同强度级别焊缝金属组织及冲击韧性的影响。结果表明:600 MPa级X80焊缝金属中通过适量添加B元素,可抑制粒状贝氏体铁素体(GBF)组织相变,提高焊缝金属的冲击韧性;随着强度的增加,700 MPa级X100焊缝金属中B原子分布于奥氏体晶内,抑制了夹杂物周围针状铁素体(AF)组织的相变,形成了板条贝氏体组织,导致了冲击韧性大幅度的降低;当焊缝金属的强度进一步增加后,添加B对X120级别焊缝金属相变点毫无影响,不能引起组织及冲击韧性的改变。

Three types of weld joint metals with or without B were fabricated by submerged-arc welding process in laboratory. The effects of B on microstructure and impact toughness of the weld joint metals with different strength grades were investigated and analyzed. The results show that the phase transition of granular bainitic ferrite ( GBF) can be suppressed and the impact toughness of the weld joint metals can be improved by adding proper amount of B element to 600 MPa grade X80 weld joint metal. With the increase of strength,the B atom in 700 MPa grade X100 weld joint metal is distributed in austenite grain,which suppresses the phase transformation of acicular ferrite ( AF) structure around inclusions and forms lath bainite structure,which leads to the decrease of impact toughness. When the strength of weld metal increases further,the addition of B has no effect on the phase transition point of X120 grade weld joint metal,and cannot cause the change of microstructure and impact toughness.