低合金高强度钢药芯焊丝焊缝中夹杂物诱导针状铁素体形核的作用

测量了HSLA钢药芯焊丝焊缝中夹杂物尺寸大小 ,分布状况 ,用透射电镜和能谱仪观测了焊缝中夹杂物的形态和化学成分 ,系统研究了焊缝中AF的形核机理。在药芯焊丝焊缝中 ,适量的Ni、Mn和Mo有利于提高焊缝显微组织中的AF质量分数 ,Ni、Mn和Mo的质量分数和焊接线能量对夹杂物的尺寸大小、化学成分影响不大 ,诱导AF形核、长大的夹杂物是Ti、Mn、Si、Al、Cu形成的氧硫复合物。夹杂物有高能惰性界面 ,以及夹杂物附近存在很高的应变能 ,两者共同作用诱导药芯焊丝焊缝中AF的形核

ROLE OF INCLUSIONS IN FORMATION ACICULAR FERRITE IN HSLA STEEL WELD METALS FOR FLUX CORED WIRES

The rule of non-metallic inclusions distrib utio n and the their sizes in HSLA steel weld metals for flux cored wires are measure d,and the chemical composition and the figures of non-metallic inclusions in HS LA steel weld metals are analyzed with transmission electron microscopy and X-r ay Microanalysis.The mechanisms of acicular ferrite nucleation in weld metal are systematically studied.The suitable percent of Ni,Mn and Mo in the weld metals ca n increase the percent of acicular ferrite in the weld metals microstructure.The percentage of Ni,Mn and Mo in the weld metals and welding energy input have lit tle affect on the chemical composition,sizes and figures of non-metallic inclus ions in the weld metals.The non-metallic inclusions beneficial to nucleation an d growth of acicular ferrite in weld metals are oxidation products of Ti,Mn,Si,A l and the sulphides of Mn and Cu.As nucleation sites,the non-metallic inclusion s can reduce the nucleation energy remarkably.Besides they have different therma l expansion coefficients than that of the substrate metals,which will introduce a high stress-stain field around the inclusions during the cooling process.Thes e two factors are the main driving forces to the nucleation and growth of acicul ar ferrite.