Research On Welding Methods And Process Optimization For Automobile Cradle By Casting Aluminum Alloy

As the development of automobile lightweight demand,the design of cast aluminum alloy frame becomes imperative.But it's very difficult to realize one piece casting for automobile cradle.Normally,the automobile cradle will be welded after subsection cast.It brings challenges for welding method selection,welding joint design and welding parameters selection to obtain ideal joint which has good weld forming and favorable mechanical properties.To study A356 cast aluminum alloy welding,first of all,we designed a robot arc welding system,set up an electrical signal acquisition system based on Labview,set up a molten drop high-speed photography system and a synchronization system between electrical signal acquisition and high-speed photography.This provides an analysis platform for droplet transition and energy distribution in the welding process.Then,we analyzed the droplet transition process and energy distribution characteristic of difficult current modes,including GMAW-P,CMT and CMT Advanced.And we studied the influence of current mode on weld formation and joint mechanical properties.The results show that: 1)GMAW-P can form a stable drop transition within a pulse.During CMT current mode,the mechanical withdrawing of wire can help realize short circuiting transfer with no splash.As for CMT Advanced,stable drop transition happens both in positive and negative half cycle.The welding energy percentage of drop transition stage decreases from GMAW-P,CMT to CMT Advanced.2)Reinforcement increases from GMAW-P,CMT to CMT Advanced,and the penetration,fusion width and melting-mixing ratio behaves in the opposite direction.It indicates that GMAW-P is suitable for thick-plate welding,CMT is suitable for medium plate welding which has request for penetration and CMT Advanced is suitable for thin plate welding.3)During three current modes,CMT Advanced has the lowest porosity percentage of about 0.3%.Moreover,taguchi method was use to design a series of experiments with five factors(welding current,welding speed,gap,welding torch angle and wire extension)and three levels to study the influence of welding parameters on weld forming and mechanical properties.The result reveals that gap,welding current and welding speed are key factors.And an effective mathematical mode has been established to show the rule.Finally,we designed a joint of simulated cast aluminum alloy frame and set up a technological procedure for the welding of cast aluminum alloy frame.The performance of simulation welding joint can meet design requirements.The study provides manufacturing process guidance and theoretical support for casting aluminum alloy frame production.