Study On Welding Technology Of Welded Carbon Steel By Cold Welding Technology

CMT Technology?Cold Metal Transfer?is a kind of low heat input welding process developed in Fronius Austria.The weld forming and properties of CMT welding are different from the traditional MIG/MAG welding's weld formation and properties,it is necessary to redesign the welding process.Both the emerging CMT technology and traditional arc welding have their own shortcomings.According to the application situation of CMT welding technology in some enterprises,the problems of fracture and even falling off of some welding joints are existed.Accordingly,the technical problems of CMT welding of low carbon steel are put forward,and it is expected to achieve good weld formation and good weld mechanical properties.In this paper,CO₂ and 97.5%Ar+2.5%CO₂ were selected as protective gas,and 6mm thick Q235 steel plate as the research object,use CMT welding machine TPS 2700 and robot OTC A II-V6 for horizontal position butt welding.The effects of CMT welding parameters such as welding current,welding speed,weld assembly clearance,swing and its mode,welding torch inclination and arc length on the formation and quality of welded carbon steel were studied.Find out the best welding technology to improve the quality of CMT welding seam,and provide some technical reference for industrial production.Weld the steel plate which has been clamped;observe,measure and record the weld formation;test the mechanical properties of the weld joints with good shape;observe and compare the microstructure of the weld seam with good mechanical properties.Through a series of plate butt welding test,mechanical properties test and microstructure analysis,the best CMT welding parameters of single side welding and double sides formation of flat-plate butt welding at the horizontal position of CO₂ protection were determined: I-shaped groove,welding current is 225 A,the welding speed is 0.6m/min,the wire feeding speed is 6.8m/min,the welding voltage is 22.9V,the arc length correction is 0,wire stem elongation is 15 mm,weld gap is 1.5mm,welding torch inclination is 90°.In the tensile test,the fracture at the base material,Weld strength is higher than base metal strength,and the weld hardness is 229 HV.When the protective gas is 97.5%Ar+2.5%CO₂,determine the best CMT welding parameters of single side welding and double sides formation of flat-plate butt welding at the horizontal position: I-shaped groove,welding current is 255 A,the welding speed is 0.6-0.7m/min,the wire feeding speed is 7.8m/min,the welding voltage is 25.5V,the arc length correction is 0,wire stem elongation is 15 mm,weld gap is 2.0mm,welding torch inclination is 90°,can have the proper circular arc swing.In the tensile test,the fracture at the base material,Weld strength is higher than base metal strength,and the weld hardness is 275 HV.The weld quality of protective gas 97.5%Ar+2.5%CO₂ is higher than that of CO₂,When the welding quality requirement is not high,taking into account the economic problems,select CO₂ gas shielded welding process;When the welding quality requirement is high,choose 97.5%Ar+2.5%CO₂ as protective gas welding process.