Research On Key Technologies Of NGW Power Supply For Thick Members Of Offshore Platform

The thick components of the offshore platform have a large welding workload,the welding process has large splashes and smoke,and the construction environment is poor.At present,welding methods such as narrow gap manual welding or narrow gap submerged arc welding are mainly used.The welding tool requires a large groove size,consumes large materials,and has low work efficiency;there is also a large heat input,and the workpiece is easily deformed;it is easy to produce splashes,poor weld quality and many other problems.When the above welding problems occur,the repair of the thick components of the offshore platform is extremely difficult,and the manufacturing cost is increased.The narrow gap CO₂welding has lower welding line energy,smaller narrow gap groove,can save welding material and energy,can be used for all-position welding,and is easy to realize automatic welding,especially suitable for welding of large components of offshore platforms.However,the existing narrow-gap CO₂ welding power source has large welding spatter,welding energy is difficult to accurately control,and the degree of automation is low.The special welding power supply for narrow-gauge CO₂ welding of thick and large components of the offshore platform is rarely developed,so how to reduce welding spatter and fine control welding Energy and improving welding efficiency are the key to studying the welding power supply of thick-walled components NGW（narrow gap welding）for offshore platforms.Based on the research progress in the field of narrow gap welding and welding power supply,this paper summarizes the advantages of the narrow gap CO₂ welding method,the limitations of the existing narrow gap CO₂ welding power supply and the development of its special welding power source,and according to the thick The characteristics of component NGW arc and droplet transfer are based on SOC high-speed DSC full digital control technology and high-power high-frequency inverter technology.The high-precision all-digital high-power inverter low-splash NGW welding power supply is designed and developed.The main work is as follows:（1）Firstly,the background and significance of this research are expounded.The research progress of narrow gap field at home and abroad is described from the aspects of narrow gap welding method and narrow gap welding power source.The research focus and key points are analyzed and summarized.（2）Design the main circuit and digital realization scheme of the NGW welding power source for the thick component of the offshore platform.Mainly include:main circuit design,control hardware circuit design and control software design.The main circuit design includes full-bridge inverter circuit design,intermediate frequency transformer design,rectifier filter circuit design and related parameter calculation device selection.The control hardware circuit design is based on the ARM Cortex-M4 processor,and the related peripheral circuits are designed,including the isolation amplifier circuit of the drive signal,the sampling and filtering circuit of the voltage and current,the fault detection protection circuit and the communication circuit.The control software design mainly includes the design of each welding task,the welding process design,the ADC sampling program design,the digital PID algorithm design,the CAN-based communication program design,the human-computer interaction touch screen program design,and the low-splash welding waveform program design.Digital control,welding work modules work together to improve welding efficiency.（3）To study the problem that the thick and large components of the offshore platform are prone to spatter,and carry out the design of the all-digital low-splash welding waveform.According to the characteristic state of detecting the droplet transition,the corresponding current waveform is adjusted in real time to realize low-splash welding.Each parameter of the low-splash welding waveform can be independently set,and the welding heat input amount can be accurately controlled,and the deformation of the weldment can be reduced.The design of arc voltage feedback double closed-loop variable speed wire feeding control system compensates for the lack of self-adjusting ability of arc length caused by current waveform control.（4）Conduct performance test,welding process test and analysis of NGW welding power source.Adjust different low-splash current waveform parameters for welding test,analyze the influence of different current waveform parameters on welding quality,change different wire feeding control methods,and analyze arc voltage feedback double closed-loop variable speed wire feeding control method for arc stability and weld quality Impact.The results showed that:The NGW welding power supply with the thick and large components of the marine platform is better than the ordinary power supply,and the low spatter waveform control can reduce the welding spatter.The arcing peak current can provide arc energy,the arcing base value can maintain and accumulate welding energy,and the peak base current of the arcing stage can be adjusted to accurately control the welding energy.In the short-circuit medium-term,the rise slope of current can control the magnitude of electromagnetic contraction force.Appropriate current slope can promote the contraction of liquid bridge and smooth transition of liquid bridge.Arc-pressure feedback variable speed wire is stable in low-splash waveform control welding,and the weld width is even and moderate.