Characterization on strength and toughness of welded joint for Q550 steel |
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Authors: | JIANG QINGLEI LI YAJIANG WANG JUAN and ZHANG LEI |
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Affiliation: | (1) Department of Manufacturing Engineering, Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalai Nagar, 608002, Tamil Nadu, India |
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Abstract: | Q550 high strength steel was welded using gas shielded arc welding and three different welding wires without pre- or post-heat
treatments. The paper investigates the influence of welding wire on the microstructure, tensile strength and impact toughness
of Q550 steel weld joints. Results showed that the microstructure of the weld metal of joints produced using ER50-6 wire was
a mixture of acicular ferrite and grain boundary ferrite including pro-eutectoid ferrite and ferrite side plate. Acicular
ferrite was mainly obtained in the weld metal of the joints produced using MK·G60-1 wire. Pro-eutectoid ferrite was present
along the boundary of prior austenite. Crack initiation occurred easily at pro-eutectoid ferrite when the joint was subjected
to tensile. Tensile strength and impact toughness were promoted with increasing acicular ferrite. Tensile strength of the
joint fabricated using MK·G60-1 wire was close to that of base metal. And tensile samples fractured at location of the fusion
zone, which had lower toughness and thus became the weak region in the joint. Impact absorbing energy was the highest in the
heat affected zone. Fibrous region in fracture surfaces of impact specimens was characterized as transgranular fracture with
the mechanism of micro-void coalescence. Acicular ferrite microstructure region corresponded to relatively large dimples while
boundary ferrite microstructure corresponded to small dimples. |
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