| Aluminum alloy was used widely in automobiles,high speed rail,ships,and aviation because of its advantages of light weight,high strength,perfect corrosion resistance and recycling.However,compared to traditional steel material,aluminum alloy had high heat of dissolution,thermal conductivity,and high solidification shrinkage,making it less weldable,which restricted its large-scale application in the industrial field.Since the high productivity and easy automation,metal inert-gas welding MIG became one of the main process methods for the welding of aluminum alloy.However,the traditional MIG welding heat input was large.The poor arc stability of aluminum alloy welding could easily cause deformation,burning through,weld pool sag and other defects,and welding efficiency was low.Based on the characteristics of aluminum alloy welding,combined with the advantages of double wire high efficiency welding and double-pulse low frequency modulation grain refinement,the double wire double-pulsed MIG welding process method for aluminum alloy was proposed for the first time,and the double wire double-pulsed MIG welding control system for aluminum alloy was designed in the paper.Based on the characteristics of double wire double-pulsed MIG welding for aluminum alloy,the overall architecture of the human-machine interaction host computer system and the hardware system of double wire double-pulsed MIG welding for aluminum alloy were determined.The sub-module hardware circuit was well designed and optimized.The human-machine interaction host computer system took STM32F429 as the core and adopted LCD screen as display interface.Full-bridge inverter topology was chosen as the main circuit of the slave machine welding power source.The principle of double-pulse low-frequency modulation and its relationship with waveform output were analyzed.A pulse phase optimization control scheme was also proposed.According to the control requirements of double wire double-pulsed MIG welding system for aluminum alloy,a human-machine interaction host computer system software based on STM32F429 and LCD screen was designed to provide welding system parameters input,command transmission,and current and voltage display window of welding process.Meanwhile,power system antiwindup PI control algorithm program,single and double-pulsed current waveform generation program and master-slave cooperative control program based on DSP were designed for the slave computer power system.Using CAN field bus to build the control system communication network,the special CAN application layer protocol of double wire double-pulsed MIG welding for aluminum alloy was defined to transmit the welding parameters and the phase cooperating control signal between the human-machine interaction host computer system and the master and slave power sources,and its correctness and feasibility was verified.A double wire double-pulsed MIG welding process test platform for aluminum alloy was established.Based on theoretical analysis and welding process tests,double wire single pulse and double pulse welding process tests for aluminum alloy in the synchronous and alternating phase modes were carried out to achieve optimal matching of multiple parameters of double wire pulsed MIG welding,in order to obtain desired weld bead and relatively stable welding process matching parameters.The weld bead and fish scale shape of aluminum alloy in the double wire single-pulse and double-pulse synchronous and alternating phases were compared and analyzed.The effect of double-pulse optimized control on weld bead quality was verified,which provides theoretical basis and practical application basis for the application of double wire double-pulsed MIG welding for aluminum alloy,so as to apply it to actual production as soon as possible. |
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