Study On GMAW Protective Gas Reduction And Nozzle Structure Optimization

GMAW is one of the most widely used welding methods in industrial production.In order to reduce the consumption of protective gas resources,improve the welding quality and the welding environment,this paper adopts the methods of theoretical analysis,numerical calculation and experimental verification to carry out a systematic study on reducing the amount of protective gas from the perspective of optimizing the nozzle structure.The main research contents are as follows:（1）Based on the gas diffusion theory,the shielding gas injection is equivalent to the gas diffusion behavior of the continuous leakage source in the atmosphere.The mathematical model of shielding gas diffusion with and without crosswind is established.The effective protection range is calculated from the morphology of weld and weld pool.At the same time,the minimum protective gas flow is deduced.（2）The Workbench-Fluent platform was used for simulation calculation of the protection airflow field.The evaluation index of protecting airflow field quality is determined by using CFD cloud chart.Through the comprehensive analysis of various nozzle structures,the advantages of spiral and diffusion structures in reducing the amount of shielding gas and improving the quality of welding seams are obvious.Three kinds of spiral diffuser nozzles with different structures are designed and the key parameters affecting the evaluation index of protective airflow field are determined.（3）Based on Isight software,AGMA multi-objective parameter optimization was carried out for the three nozzle structures.The optimal Latin hypercube test method was adopted to take sample point data.The response surface method was applied to establish an approximate model and conduct precision verification and error analysis to obtain the optimal structural parameters of each nozzle.Through CFD simulation verification and comparison with ordinary diameter nozzles,the optimized improvement value of each nozzle and the percentage of gas reduction and other parameters are obtained.At the same time,the CFD simulation results show that the double helix nozzle is better.（4）Three nozzles wiht double spiral diffusion were printed by 3D printing.Thewelding test of 80%Ar+20%CO2 mixed shielding gas was carried out on Q235 and A36 steels.Standard samples were made according to the national standard.Tensile test,impact test,hardness test and microstructure analysis of welded joints were carried out.The experimental results were consistent with the simulation results.This research is supported by the practical innovation plan of jiangsu province,"research on the minimum amount of GMAW protective gas and optimization of nozzle structure parameters"（SJCX18₀736）.The optimization of the nozzle structure of the welding gun and the amount of welding shielding gas in this paper have certain guiding significance and reference value for the mechanism research and engineering application in the field of welding.