LASER-GMA HYBRID WELDING OF 960 MPA STEELS

摘要

Steel manufacturers are focusing more and more onrndeveloping high strength steels. This means thatrnlower heat input welding processes are needed tornachieve matching joints. The effect of the base materialrnand the alloying of the filler materials on the mechanicalrnproperties of laser-GMA hybrid weldingrnhave been investigated. The welding trials were carriedrnout for two ultra high strength steels, Optim 960rnQC and S960QL, with different manufacturingrnroutes. In the welding tests a butt joint was weldedrnfor both steels and the thicknesses of the base materialsrnwas 6 mm. According to the results of the weldingrntests, it was possible to achieve strength of the jointrncorresponding to the nominal strength of the basernmaterials for both steels, regardless of the strength ofrnthe welding wire used. Matching and ductile jointsrnwere achieved for both steels with one pass and withrna non-alloyed ferrite welding wire. Typically, if comparedrnto conventional quenched and tempered steels,rnOptim 960 QC steel is superior with respect to thernimpact toughness of the fusion line and heat affectedrnzone (HAZ) due to its low carbon and alloying contentsrnfollowed by a lower hardened bainitic and martensiticrnmicrostructure. However, in this study, therntoughness differences of the HAZ between the lowrncarbon (C ≈ 0.10%) quenched and tempered referencernsteel S960QL and Optim 960 QC steel was notrnsignificant, but the toughness of the HAZ of Optimrn960 QC was still better.