| Aluminum alloy is widely used in automobile,ship,aviation and other fields because of its light weight,high strength,good corrosion resistance and recyclability.However,compared with the traditional steel materials,aluminum alloy has higher melting heat,thermal conductivity and solidification shrinkage,which makes its weldability poor,and restricts its large-scale application in the industrial field.According to the characteristics of aluminum alloy welding,combined with the advantages of double-wire high-efficiency welding and double pulse low-frequency modulation to improve the mechanical properties of the weld.The high and low-frequency pulse phase aluminum alloy double-wire double pulse MIG(Melt Inert-Gas Welding)welding process,and designs the aluminum alloy double-wire double pulse MIG welding control system are put forward in the paper.Based on the analysis of the characteristics of double-wire pulse MIG welding,the hardware system and software system of the integrated aluminum alloy double-wire double pulse MIG welding are established,and the principle of double pulse low-frequency modulation is briefly described.On this basis,the high and low-frequency pulse phase cooperative control system is proposed,and the welding characteristics of low-frequency phase and high-frequency phase are analyzed.The welding process of high and low-frequency aluminum alloy double-wire double pulse MIG welding is built.In order to analyze the dynamic behavior of metal transfer,the metal transfer photography platform for double-wire pulse MIG welding was built,and the test operation specification was given.The load characteristics of the system with high-frequency phase angle of 0°,60°,120° and 180° and the influence of U-I characteristics on the stability of welding process are analyzed under the two phase modes of low-frequency synchronous phase and low-frequency alternating phase,and the calculation methods of the average values of output current and voltage are given.The influence of phase mode on the output characteristics of welding is analyzed,and it is found that the output of low-frequency alternating phase is higher than that of low-frequency synchronous phase and the higher the phase angle of high-frequency is,the more stable the output characteristic is.Based on the experimental results of droplet transfer platform,the arc shape and droplet transfer of high and low-frequency phase mode are analyzed,and the influence of high and low-frequency phase mode on droplet transfer is summarized.The metal transfer modes of highfrequency phase angle 0° and high-frequency phase angle 180° are mainly two droplet per pulse and one droplet per pulse.The high-frequency phase angle 180° is the alternating metal transfer,the high-frequency phase angle 0° is the synchronous metal transfer,and will collide and form a larger droplet into the weld pool.The phase angle 60° and 120° metal transfer modes are a mixture of two droplets per pulse and one droplet per pulse.Combined with the pinch instability theory(PIT)mathematical model,the influence of the high and low-frequency phase mode on the droplet size is analyzed.It is found that the droplet size is inversely proportional to the high-frequency phase angle.The influence of phase mode on heat input is explored.The heat input of low-frequency alternating phase high-frequency alternating 180° is the most stable in the whole welding process.The influence of phase mode on weld formation is analyzed,which provides theoretical basis and practical application basis for the application of aluminum alloy double-wire double pulse MIG welding,in order to apply it to the actual production as soon as possible. |
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