(1) The welding current in order to improve the rate of melting is necessary to increase the welding current, welding current increases, the melting rate of the welding material will significantly improve. But for a certain diameter of the wire in terms of its current capacity there is a certain limit. When the welding current increases to a certain extent, the welding arc shape and droplet transfer forms will change significantly. When using the filaments, the welding current increases to a certain extent, will be unstable rotating jet transition, this time droplet often is the horizontal throw to become splash, welding process is very unstable. Thick filament current welding, such as SAW, with the increase of the welding current, wire melting rate increased, but at the same heat input of the workpiece increase as welding heat input to improve for high strength steel and special-use materials welding is very inappropriate. In this case, in order to ensure welding quality improve welding productivity, process measures must be assisted to improve the welding current.

(2) wire stem elongation under the same welding current, the stem elongation increases wire can also increase the melting rate of the wire. C2 in Figure 1 represents the ohmic heat generated in the wire current is proportional to the square of this wire melting rate is very important. Wire resistivity will wire temperature increase with the increase of welding current, the wire resistivity will increase. Figure 2 apply for three different dry stretch the length of the wire melting curve of the relationship between efficiency and current. It can be seen from Figure 2 in the same welding current circumstances, with the increase of stem elongation, wire deposition efficiency improved significantly. Therefore, in the high-current welding, the ohmic heat generated in the wire on the wire melting rate plays a vital role.

(3) the polarity of the deposition efficiency of different polarity Welding Wire and base metal deposition efficiency is different. Under normal circumstances, MIG welding using DCEP (DCRP), DCEP can achieve a greater penetration depth and can prevent the penetration depth less than the defect. Figure 3 and Figure 4 shows the relationship between the polar and penetration as well as wire deposition efficiency. It can be seen that the DCRP can get a larger penetration depth, but the smaller the wire deposition efficiency; DCEN is (DCSP) wire can obtain a higher deposition efficiency, but the base metal penetration small.It can be seen from Figure 3 and Figure 4, can be adjusted by changing the polarity of the deposition efficiency of the melting rate of the base metal and wire, to meet the requirements of the different welding processes. If the requirement to increase the penetration of the base metal, you can use DCEP; welding sheet can be used DCEN is to reduce the penetration of the base metal, and increased the melting efficiency of the wire, and ultimately high-speed and efficient welding.

(4) wire diameter Figure 5 illustrates the different diameter of wire deposition efficiency under different welding parameters. It can be seen, in the same welding current circumstances, as the wire diameter decreases, the welding current density increased, wire deposition efficiency increased; the contrary, to maintain the efficiency of the deposited certain, with the reduction of wire diameter small welding current decreases, the corresponding heat input to the workpiece is also reduced, that is the same under the premise of the deposition efficiency can reduce the heat input to the parent metal, the Welding Flux of high strength steel and special purpose steel is very beneficial the. Therefore, the welding workers in efficient MIG / MAG welding process, most of the filaments, large current welding is the use of the above advantages. 1.2mm wire, such as TIME welding process and the maximum wire feed speed up to 50m/min. LINFAST and double-wire TANDEM welding processes are used filaments of 1.2mm. Filaments welding An additional advantage is the stability of the arc in the welding of the small current increase, the impact of the weld pool decreases, thereby maintaining uniform penetration.

(5) the impact of shielding gas for MIG / MAG shielding gas research has been carried out for many years, the role of the protective gas in the welding process is mainly manifested in the following aspects: (1) to improve the arc stability. ② improving droplet transfer. ③ improve the mechanical properties of the weld metal. (4) improve the welding productivity. ⑤ to reduce the possibility of welding defects, such as porosity, lack of fusion. In addition, due to the different gases of different physical and chemical properties, the role played by it in the welding process is not the same, the choice of shielding gas for different process conditions, different applications and different.