母材熔合作用对EQ51海工钢焊缝组织及韧性的影响

Fusion effect on weld joint microstructure and toughness of EQ51 ocean engineering steel

文中采用示波冲击,EBSD,SEM研究了母材元素含量、坡口形式、焊接热输入对海洋工程用钢EQ51焊缝组织转变、低温冲击韧性及焊接接头软化程度的影响规律.结果表明,C,Mn元素含量对焊缝组织类型、取向趋势起关键作用,含量由0.1%,1.5%分别调整为0.06%,1.3%,可保证焊缝组织由板条贝氏体转化为针状铁素体,组织止裂能力显著提高,冲击吸收功大于100 J;适当提高焊接热输入一定程度上可降低淬硬元素对韧性的不利影响;Ni,Mo元素含量对焊缝组织、韧性影响不大,主要决定焊接接头软化程度,Ni,Mo元素总添加量由0.7%下降到0.4%,软化区宽度由1 mm提高到2 mm,焊接接头抗拉强度由789 MPa降低到650 MPa.

The effects of elements content,groove shape and welding heat input on the welded joint microstructure transformation,impact toughness,heat affected zone softening degree of EQ51 ocean engineering steel plate were studied by instrumented charpy impact test,EBSD and SEM.The results indicated that C and Mn contents in base metal play a key role on weld joint microstructure type and orientation.When C and Mn contents reduce respectively from 0.1%,1.5% to 0.06%,1.3%,welded joint microstructures transfer from lath bainite to acicular ferrite,crack arrest ability obviously increases and its impact absorption energy exceeds 100 J.Appropriately increasing heat input would improve the harmful effect of quench hardening elements on welded joint toughness.Ni and Mo don't affect microstructure transformation of welded joint obviously,but play a critical role on heat affected zone softening degree.Total content of Ni and Mo reduces from 0.7% to 0.4%,softening zone width increases from 1 mm to 2 mm and tensile strength decreases from789 MPa to 650 MPa.