高强钢金属芯焊丝E120C-K4熔敷金属粗晶区显微组织对冲击韧性的影响

Microstructure to properties of coarse grained heat affected zone in deposited weld metal of metal cored wire E120C-K4

采用焊接热模拟通过改变冷却时间(t8/5),研究了金属芯焊丝E120C-K4多道焊熔敷金属模拟粗晶区(CGHAZ)显微组织对冲击韧性的影响规律.结果表明,当t8/5为6~12 s时,CGHAZ显微组织由蜕化上贝氏体、粒状贝氏体和针状铁素体组成,奥氏体晶粒内部形成复相分割结构,冲击韧性最好.而当t8/5为30~120 s时CGHAZ显微组织主要由粒状贝氏体和针状铁素体组成,冲击韧性下降.t8/5为120 s时,冲击韧性最差,–40℃冲击吸收能量仅为24 J.t8/5为6~12 s时韧性改善的关键是形成复相分割微观结构;晶粒细小;单位距离上大角度晶界数量多.

The effect of microstructure as a function of welding cooling time(t8/5)from 800°C to 500°C on the impact toughness of coarse grained heat affected zone(CGHAZ)of deposited metal of metal cored wire E120C-K4 was investigated by welding thermal simulation.The results showed that the microstructure of CGHAZ was mainly composed of degenerate upper bainite(DUB)granular bainite(GB)and Acicular ferrite(AF)at t8/5 from 6 s to 12 s,forming the interlace multiphase microstructure,then the optimal impact toughness was obtained.The microstructure of CGHAZ formed with granular bainite(GB)and Acicular ferrite(AF)and the impact toughness decreased when t8/5 from 30 s to 120 s.The absorbed energy of CGHAZ was only 24 J at−40°C at t8/5 of 120 s,the worst impact toughness.The key of improving impact toughness at t8/5 from 6 s to 12 s was:①forming the interlace multiphase microstructure;②refining grains;③more high-angle grain boundaries per unit distance.