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Double wire indirect arc welding arc characteristics and droplet research

Author: ZhangShunShan
Tutor: ZouZengDa
School: Shandong University
Course: Materials Processing Engineering
Keywords: Double wire indirect arc Arc shape GMAW Droplet
CLC: TG444
Type: PhD thesis
Year: 2010
Downloads: 353
Quote: 0
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Abstract

With the development of welding technology, how to improve the productivity of electric arc welding, weld quality, and expand its field of application to become the focus of researchers. Conventional arc welding process the deposited low coefficient to improve welding productivity has been limited, a reasonable allocation arc heat in the base metal and wire arc thermal energy than in recent years become an important research direction. Double wire indirect arc GMAW welding process is a new, belonging to MIG welding, arc welding process between the workpiece and wire burning, dual-wire indirect arc welding arc is formed in two wire ends; unlike its wiring traditional arc welding, double wire and power respectively positive and negative phase, double wire are melting polar arc energy is melted wire, only a small part of the arc heat for melting the base material, so its high deposition rate, energy use high; Since almost no current flows through the base material, the method also has the fusion ratio is small, welding stress and deformation characteristics, is a good prospect and efficient welding process. Double wire indirect arc welding equipment is different from traditional electric arc welding equipment. This article first twin-wire indirect arc welding equipment, key components of the torch has been optimized. Double wire indirect arc welding, arc shape directly affect the penetration and quality of welded joints. Indirect nature of the arc with the same conventional arc welding, its shape is affected by many factors. This paper focuses on the main process parameters and magnetic field on the indirect impact of the law to carry out research on arc shape, and arc shape under different variation of weld penetration were studied. With major research equipment and instruments including FASTCAMSuper-10KC speed camera system, Agilent54624A digital oscilloscope, LZ-630 digital tesla meter, self-designed external excitation equipment and NBC-350-type inverter type CO2 gas shielded arc welding power supply, etc.; adopted The test material is H08Mn2SiA Φ1.2mm wire, 3mm thick test plate Q235, and the protective gas is Ar and CO2 mixed gas, the test plate welding method. On the design of the torch, the main parts of the structure on the torch, linking methods and shield gas chamber structure to optimize the design and numerical simulation. Torch design considering two of the neutral wire with insulation between the conductive tip, shape and size flexibility, process reachability, wire resistance and gas and other aspects of the protective effect, in order to ensure the welding process is stable; finite element analysis method different shapes shield and hood area at the outlet of the gas flow conditions were simulated. The results show that the cylindrical inner chamber shield protective gas at the outlet of the flow field can be reduced turbulence level, but at the outlet of the gas flow rate and flow pressure are very low, the protective effect is limited; shrink-shaped air chamber inside the protective cover protective gas flow at the exit of the protective cover is easy to form turbulence, and reduce the air mixed with the protective effect; variable cross-sectional shape of the protective shield of the gas chamber to effectively improve both the outlet turbulence phenomena, but also increase the gas flow rate and air pressure, is an ideal protective hood air chamber design. Protective cover decision variable section structure of the main parameters of the gas chamber is cylindrical and cylindrical contraction at the height h and the slope θ, research shows that h, θ were designed at 45 °, preferably of 20mm. Twin wire arc characteristics for indirect research trials found that double wire indirect arc welding wire melting much faster than the anode cathode, both wire feed speed is equal to its stable arc burning indirect premise wire feed speed in the case of small change , the self-regulation by the arc, the arc can restore and maintain stable combustion, but the wire feed speed and the melting speed is large, the arc will be unstable or even broken arc. Twin-wire arc gases indirectly affect welding wire melting and penetration main process parameters including wire extension length L, two wire angle α, the intersection of two wire to the workpiece distance d, the welding current I, the arc voltage U, and the welding speed v protective gas composition used. In other welding parameters under the same conditions, the greater length of wire out, the greater the wire melting rate, mainly due to the heat resistance of the reasons, this study used the wire extension length is 10mm; with two wire angle becomes small, electromagnetic contraction force increases, indirect arc shape tapering longer, weld penetration increases, while the angle changes will have an impact on the arc static characteristic. Experimental studies have shown that 20 ° -40 ° angle chosen is appropriate; two wire intersection distance to the workpiece size of weld penetration has a decisive influence decreases with distance arc mechanical compression effect of indirect increase penetration increases. Tests showed that the intersection of two wire distance to the workpiece is selected in 6-8mm, easy to get a larger weld penetration; with the increase of the welding current, weld penetration increased, but to a certain value, the arcing phenomenon resulting melt dispersion deep arc voltage decreases with increasing penetration changed little, weld width increase was more pronounced; welding speed 10mm/s-11mm/s get greater benefit when the weld penetration; adding CO2 shielding gas arc can change shrinkage, the arc heat becomes concentrated, weld penetration increases but the proportion of more than 50% CO2, the spatter increases, the welding process is unstable, 75% Ar 25% CO2 as the preferred protective gas components. Double wire indirect arc trajectory of charged ions determines the arc shape, this pair of double-wire indirect arc welding current generated by its own magnetic field distribution was studied, and the plane xoz each point were calculated from the magnetic field strength and measurements. Changes in the use of an external magnetic field inside the arc ion trajectory to change the arc shape and then change the penetration depth. Research indicates indirect arc transverse magnetic field is applied, the transverse magnetic field with the magnetic flux density is increased, the arc becomes elongated, weld penetration increased; longitudinal magnetic field is applied, the arc deflected arc around the axis of rotation, rotation radius and the magnetic field size. With the external longitudinal magnetic field strength is increased, the weld penetration decreases slightly; with external longitudinal magnetic field strength increases negative, weld penetration is also slightly reduced. Double wire indirect arc welding droplet forms include large droplet transfer, short transition, transition and jet drop shot transition. Different forms of transition from the oscilloscope records under the arc voltage and welding current change shows that the jet transition welding process more stable, get a good weld. Double wire indirect arc jet transition its critical current value depends on the process parameters, in certain parameters, the two wire angle decreases and shielding gas composition makes the C02 content increased jet transition critical current values ??decrease, while the wire length to increase the critical current value is increased. In certain welding parameters is applied transverse magnetic field, the magnetic field strength increases with positive droplet diameter smaller droplet frequency increases; while with the reverse magnetic field strength increases, the droplet becomes large, the transition frequency is reduced. Applying a longitudinal positive and negative magnetic field, the droplet trajectory from the wire is extremely wire side of the anode and cathode, respectively, to deflect, and the magnetic field strength increases, the degree of deflection increases, a larger diameter droplet.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Arc welding
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