氧化铈对FAB法埋弧焊缝组织与性能的影响

Effect of CeO_2 on properties of weld metal by FAB submerged arc welding

实验研究了CeO_2对FAB(焊剂石棉衬垫单面焊)法埋弧焊D32船用高强钢焊缝金属组织及性能的影响.结果表明:在焊接电弧作用下,CeO_2使焊缝金属增氧,Mn和Si含量降低;CeO_2能细化FAB埋弧焊焊缝金属中夹杂物,促进直径小于2.0μm铈的氧硫复合物形成,并诱导大量针状铁素体形成;合金粉中加入CeO_2后,焊缝金属显微组织主要为针状铁素体、少量先共析铁素体与侧板条铁素体;合金粉中CeO_2质量分数不超过3%时,焊缝金属的屈服强度、抗拉强度、V型缺口冲击值随CeO_2质量分数增加而增加,当达到5%时,焊缝金属的屈服强度、抗拉强度和V型缺口冲击值有所下降.焊缝金属中CeS,Ce_2S_3和Ce_2O_2S复合夹杂物诱导针状铁素体的形核机理是它们与针状铁素体的错配小,符合最小错配度形核机理.

The effect of CeO2 on microstructure and mechanical properties of weld metal was systematically studied by flux aided backing（FAB）submerged arc welding technology to join D32 high strength low alloy steel for shipbuilding.Results show that the cerium and oxygen contents increase while the manganese and silicon content decreases in weld metals under the effect of electric arc.When CeO2 alloy powders are added,inclusions in weld metals are refined and the number of inclusions containing ceriumoxy-sulfidecompound with 2.0μm in diameter increase,and the microstructure of weld metals are composed mainly of acicular ferrite as well as a few proeutectoid ferrite and ferrite side-plate.When the CeO2 content in alloy powder is less than 3%,the yield strength,ultimate strength and V-type impact toughness become higher with the increasing of CeO2 content in alloy powder.But once the CeO2 content in alloy powder is over 5%,mechanical properties of weld metal would decrease conversely.The nucleation mechanism is that promoted acicular ferrite nucleated by CeS,Ce2S3 and Ce2O2S is the similar misfit between CeS,Ce2S3,Ce2O2 S and acicular ferrite,which agrees with the minimum misfit mechanism.