Study On Arc Shape And Droplet Transfer Behavior In Arc Based Addtive Forming

The arc based additive forming technology is based on the arc as a heat source.The two-dimensional model of the superimposed weld sawas final formed three-dimensional members of advanced manufacturing technology. Due to its high efficiency and low cost advantages, the filament material as the electrode of metal inert-gas welding(MIG) welding,which has recently become a hot topic.Therefore,We study on arc shape and the droplet transfer behavior in the process of the overlapping deposition by using three methods; metal inert-gas welding,pulsed metal inert-gas(P-MIG) welding and pulsed double-electrode MIG.First, we analysis the influence of single-layer weld bead and multi-layer weld bead by different droplet transfer behavior of three welding methods. Compared to the single-layerweld bead, the multi-layer weld bead caused by Free transition of droplet transfer behavior is best on the constant voltage source conditions, while work parts emerge severe heat accumulation, the welding bead collapsed down in the multi-layer welding.the arc length becomes longer,When emerging the arcadjustment, welding current smaller, droplet transfer frequency decreases and droplet size increases. By adopting the P-MIG of multi-layer welding on the constant current source, while work parts emerge severe heat accumulation phenonmens, the welding bead collapsed down in the multi-layer weldings. The arc length becomes longer, the multi-layer weld bead is best in the droplet transfer of one droplet per pulse. The welding voltage increases resulting in weld width in the same layer and between the layers occur variety cased by the heat accumulation efficiencies. When adopting the Pulse DE-GMAW welding, the heat input is low and heat accumulation efficiencies are not obvious so that the droplet transitional form will not changes.Therefore, it is the key point for forming a multi-layer weld bead that controlling the heat inputs.Secondly, in order to improve the multi-weld molding, we adopt the a metal cored wires then compare wiht the wire transition critical current, droplet transfer,and then weld to ordinary carbon steel and found that the metal-cored wire shot drops transitional critical current lower than carbon steel wires 30 A, droplet transfer frequency reduced droplet size increases, the bottom of the arc enveloped the area smaller, heat input low. The above-metion’ features make the metal cored wire more applicable to the arc shaped material gain. In Improving the arc end formabilitya spect, we adopt to reduce arcing wire feed speed and to increase the arcing current.Due to the differernt in heat inputs of the base material welding on the three kinds of method, we need to select the aspect ratio of the weld parameters: 3 and 4. To ensure the stabilitys of the material filling speed, the need to ensure a stable droplet transfer behavior. We analysis the inflence of weld on weld cooling time between different layers, and then the results indicate the impact on the front layer of the welds mall with longer the cooling time, but will seriously affect productivities.Finally, we analysis microstructure and hardness of the ten single-channel layerweld in the different interlayer cooling time. The reslut indicate that the cooling time short, the cycle heat input large.The microsturcure of grain is relatively laacicular martensiterge compared to the, while due to the cycle heat input small on the top weld, the on the top weld is martensite microstructure the organization single-channel of 10 layers of member, the cooling time is short, the cycle heat input large grain is since the top weld cycle heat fewer grains, mostly. Duing to the lower part of weld beam effect multiple cycles of heat on a similar weld annealing heat treatments, the down weld beam is the lower hardness, while the top martensite hardness is about 250 HV.