Studies On Preparation And Welding Process Of Coated 316L Stainless Steel Welding Wire

Stainless steel is widely used in engineering fields for its excellent corrosion resistance.As one of the main welding methods of austenitic stainless steel,GMAW has the advantages of high production efficiency,low welding cost,small deformation of workpiece and good quality of welding joint,but the quality of the stainless steel solid wire for GMAW is difficult to meet the requirements of the increasing market demand because of its large welding spatter,narrow range of process parameters and high performance requirements for welding power equipment.In this paper,the coated 316L stainless steel wire was developed to improve the welding process of 316L stainless steel wire with the surface modification of 316L stainless steel wire by the coating technology.Drawing coating,a surface coating technology for wire,was developed according to the characteristics of the coating on wire.An indentation device was designed and manufactured for roughening the surface of the welding wire to improve the bonding strength and uniformity of the coating.The device performs indentation pretreatment on 316L stainless steel wire by two pairs of pressure wheels in the horizontal and vertical directions,forming uniformly distributed dents on the surface of the wire,and combining the drawing coating to prepare a coated 316L stainless steel wire.A GMAW droplet transfer model was established based on fluid dynamics and electromagnetics.The VOF model was used to track the surface of the droplet,and various forces were applied to simulate the droplet transfer.The simulation results show that the short-circuit time is very short and the droplet growth process takes up the remaining time during a short-circuit transition;During free transition,the size of the droplet gradually decreases and the transition frequency continuously increases with the increase of welding current,which is basically consistent with the actual welding process.The essence of the droplet transfer is a comprehensive reflection of the force applied to the droplet based on hydrodynamics.Regulating the force applied to the droplet is an important way to improve the welding stability.The stability of the GMAW welding process was analyzed in terms of the force applied to the droplet to guide the coating composition design of the stainless steel welding wire.According to the different functions of the coating composition,three kinds of composition formulas were designed.The 316L stainless steel wire was indented on both sides and on the four sides respectively by the indentation device.Six types of coated 316L stainless steel welding wires were prepared by drawing coating.The welding process of the coated 316L stainless steel welding wire was studied by the welding electrical signal acquisition system and high-speed photography.The results show that the coating composition is the main influencing factor of the welding process of the coating 316L stainless steel wire.Irrational coating composition will deteriorate the welding process of the coating wire.The adding amount need be controlled even the coating composition is appropriate.The uniformity of the coating will also affect the stability of the welding process.Compared with the coated wire with two-side indentation,the coating wire prepared by four-side indentation has better uniformity.The coated 316L stainless steel wire with good welding process was prepared by the drawing coating process with four-sided indentation,and its coating composition includes Ca CO₃,Na F,Ti O₂,Si O₂,Ni-Fe,Mn-Fe and Mo S₂.The 316 stainless steel was welded with the wire,and the comprehensive mechanical properties of the welded joint are good.