Study On Technology And Mechanism Of Laser-plasma Arc Hybrid Welding

Laser and plasma arc hybrid welding with two high energy beam heat sources is a new technology with good industrial development prospects.Compared with single heat source welding,this hybrid welding technology can achieve higher welding speed and penetration,and higher welding quality.Using 304 stainless steel widely used in industrial production as the test object,the influence of key jointing parameters(laser power PL,welding current I,heat source spacing DLA and arrangement position,welding speed Vw,defocusing amount ?f,etc.)on weld formation were studied by means of plate surfacing welding.Research on welding mechanism of hybrid welding plasma and molten pool flow image by high speed camera and laser coaxial CCD camera,to further verify the regular relationship between weld forming and the process parameters,provide a theoretical basis for the optimization of the process parameters,and determine the best hybrid welding parameters.The experimental results show that laser power and defocusing mainly determine the penetration depth of weld,the laser plasma of about 1500W power is the most stable and the energy utilization rate is the highest;the optimum heat source spacing is between 4mm and 5mm,the fluidity and spreading of weld pool is the best when laser is used in the welding direction;when welding current is less than 150A,the weld width is mainly determined when welding current is greater than 150A;When the current increases,the penetration increases obviously;when the current is between 150A and 250A,the plasma state is the most stable and the energy utilization rate is the highest;laser-plasma arc hybrid welding has clear superiority in high-speed jointing above 1000mm/min,and it is easier to produce undercut and porosity defects if the welding speed is too low.In order to verify the practicability of the hybrid welding technology,relevant process tests were carried out.The experiment of plate self-fusion welding process was carried out on stainless steel sheet with 2 mm thickness.The experimental show that under the premise of guaranteeing a minimum welding speed of 1000mm/min,the smaller the laser power,the smaller the matching current range,and the smaller the welding speed that can be achieved.The butt welding experiment of stainless steel sheet with 4 mm thickness without groove was carried out.The arc hybrid welding technology can realize the double-sided forming of 4 mm thick plate butt welding,and has good adaptability to the gap and staggered edge.The maximum adaptive gap is 0.5 mm and the maximum adaptive staggered edge is 1.5 mm.The plate self-fusion welding process test of 12 mm thick stainless steel plate is carried out and compared with laser-deep penetration TIG.The experimental results show that the laser-plasma welding process under the same parameters.The energy utilization rate of arc hybrid welding technology is higher,and the process parameters under thick plate are very narrow.Under the parameters of welding electricity I=300A,laser power PL=3000W and jointing speed Vw=350mm/min,the single-side welding and double-side forming of 12mm thick plate can be realized.The later welding period is unstable,the later welding quality is poor,and the tungsten pole loss is aggravated.Macroscopic morphology and microstructures of laser-plasma arc hybrid welding joints were analyzed,and mechanical properties were tested.The experimental results show that the heat-affected zone of the hybrid welding joints is narrow,and the hybrid welding seams are mainly divided into laser arc hybrid zone and laser zone.Compared with the base metal,the grain size of the weld zone is more refined,and the laser arc hybrid zone is mainly composed of austenite and skeleton iron,The number of lamellar ferrite in the weld of the laser region increases,and the grain size becomes larger,The hardness of base metal is the lowest and that of HAZ is the highest in the hybrid welded joint.The tensile strength of the weld joint is about 600 MPa,which can reach 94%of the strength of the base metal.When the bending angle and the bending angle are 180 degrees,the hardness of the hybrid weld joint is the highest.No cracks were found in the welds.The impact toughness at the weld is greater than the impact toughness at the heat affected zone.The maximum impact toughness was 477.84KJ/m2,and the impact toughness was good.