Research On The New Technology Of Ternary Mixture MAG Welding On Q345E Steel And Its Micro-structure And Properties

GMAW has fast cladding speed,high production efficiency,easy to realize automation,in welding production have been more and more widely used.At present,the gas shielded arc welding in our country usually adopts a single gas(such as Ar,CO2,etc.)or two mixed gas(Ar + CO2),Welding equipment is also more traditional DC MAG welding machine.But with the continuous improvement of China's high-speed railway industry development and the level of welding,people on the welding quality have higher requirements,the traditional welding technology and can not fully meet the requirements,so it is urgent to seek a kind of new technology can not only improve the welding quality,but also has the best economy.Ternary mixed protective gas MAG welding because of its wide adaptability,high welding efficiency and good weld forming has been increasingly widespread attention,in foreign countries has been widely used,and our country is still in initial stage.In this experiment,the application of three mixed gas(Ar+CO2+O2)MAG welding on Q345E steel of locomotive car body is deeply studied.Selection of Q345E low-alloy steel welding process test of base metal,welding method using DC MAG welding,the docking,multi pass welding(backing and filling,cover),welding gas shielded by two different proportions of ternary mixture 3A 80%Ar+15%CO2+5%O2/3B 85%Ar+10%CO2+5%O2/3B 90%Ar+7%CO2+3%O2 with current production widely used binary mixed protective gas 802 80%Ar+15%CO2 consists of four kinds of welding gas protection welding.After welding,the welding process is observed and analyzed to determine the optimal welding parameters,Then in accordance with the international standard welding cutting,preparation of continued testing of specimens;weld shaping law test,from the appearance of weld° seam forming and weld cross-section of four kinds of gas welding were analyzed;then on four kinds of welding gas protection in splash rate test,to analyze the experimental data,obtained four gas shielded welding spatter rate size;metallographic test,hardness test,tensile test,bending test and low temperature impact test,from the microstructure properties to mechanical properties of ternary mixed gas welding joints were analysis.Through a series of performance test showed that compared with the binary gas mixture,the tri mixed gas advantage is more obvious in the MAG welding,good weld appearance molding,the mechanical properties have reached the international standard requirements,also has tiny splash rate,high welding efficiency,both to ensure the welding quality,and greatly saves working hours,reduce the cost of welding,if the new welding technology are widely applied to actual production,it will be of great significance.