| High-strength steel and weathering steel are widely used in engineering and construction because of high strength,high toughness and good weather resistance.At the same time,dissimilar steels welding meet different application requirements.In this paper,MAG(Metal Active Gas Arc Welding)is used to weld Q960 E high-strength steel and Q690 q ENH weathering steel.Two kinds of welding wires,ER91T1-G and XYER80 QNH,the welding process parameters were explored,and the effects of different process parameters on microstructure,hardness,mechanical properties,and electrochemical corrosion properties of welded joints were studied.The temperature field analysis with better welding process parameter was carried out by numerical simulations.The main research content and results as follows:Adopting the single-sided V-shaped bevel with blunt edge,designing four process parameters for two welding wires of ER91T1-G and XY-ER80 QNH with MAG,and obtaining Q960E/Q690 q ENH dissimilar steel welding joints.Dissimilar steel joints were obtained by using the ER91T1-G welding wire and four processes,fusion zone microstructure is acicular ferrite,proeutectoid ferrite and side lath ferrite,the coarse-grained zones on the Q960 E side and the Q690 q ENH side are granular bainite and lath martensite,Q690 q ENH side contains more granular bainite.The hardness distribution is related to the microstructure distribution.The welds with various kinds of ferrite have the lowest hardness values,and different areas of the heataffected zone have different degrees of softening.Tensile test results show that the strength of the weld is the lowest,and the tensile strength with different parameters is different.The highest tensile strength is 770.2MPa,the fracture morphology shows a large number of dimples,and the fracture morphology shows that mode is plastic fracture.Electrochemical corrosion performance studies show that Q690 q ENH side has better corrosion resistance,the corrosion resistance of the welded joints with four process parameters is different,and the samples with better corrosion resistance have the lowest average self-corrosion potential of the welded joint about-0.53 V,between Q960E(-0.62V)and Q690 q ENH(-0.53V).In the welded joints obtained by using XY-ER80 QNH welding wire and four process parameters,the microstructure test shows that the fusion zones are lower bainite composed of acicular ferrite and cementite,the microstructure of the Q960 E coarsegrained zone mainly different.Q690 q ENH coarse-grained zone is mainly more granular bainite,and the content of granular bainite on both sides decreases with heat input.The hardness distribution is related to the microstructure,and the weld hardness is higher than Q690 q ENH(284.8(HV0.3)),heat affect zone also has different degrees of softening.The tensile test results show that the tensile properties of the four process parameters are different in the fracture position,the electrochemical corrosion test results show that the Q690 q ENH side has better corrosion resistance,the corrosion resistance of the welded joints is different,although the average value of corrosion potential is equivalent to the base material Q690 q ENH(-0.53V).The temperature field simulation of the XY-ER80 QNH welding wire was carried out in the condition of better process parameters,and it was found that the high-strength steel may be softened after many high-temperature thermal cycles.Comprehensive analysis shows that for Q960E/Q690 q NH dissimilar MAG steel welding,XY-ER80 QNH wire,multi-layer multi-pass welding is used,and the welding speed is 0.5 m/min,bottom welding,filling welding,capping welding current is respectively 160 A,220A,260 A,and the welding voltage is 19.6?22V(automatic matching),which can obtain good welding joints. |
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