Study On Vertical Fillet Welding Technology Of T-joint Of Double Robots For Medium And Thick Plate

The production process of large-scale marine equipment,military industry,bridge and construction industry is inseparable from the use of T-joint structure.At present,the process of full penetration required for T-shaped structure of medium and thick plates is still manual welding.The joints are formed by single-side Y-type or K-type grooves,and manual welding is used for front welding,back carbon arc air gouging,repair and grinding,and flux cored wire gas shielded welding is used for filling and covering.The complex welding process and low production efficiency are not suitable for the development of industrial intelligent automation.Aiming at the above problems,this paper proposes an industrial welding robot based on the original CO2 gas shielded welding with flux cored wire,and use the industrial welding robot with the double-sided double arc welding technology to realize the welding process of full penetration and unclear root of T-joint of medium and thick plate.In the study,the influence of welding parameters and robot swing mode on the cross-section forming of robot FCAW weld was explored through the single side single arc vertical fillet welding test of T-joint.It is found that the robot triangle swing mode can enhance the penetration of vertical fillet weld without groove,so as to ensure that the formation plays a significant role.The penetration is increased by 25~50%,the weld leg size is increased by about 1/3,the weld surface is formed into a micro concave,which greatly enhances the stability of the weld joint.In order to further study the double-sided double arc welding process.The numerical simulation software MARC is used to simulate the double-sided welding of T-joint,and the welding test and hardness test are carried out for different arc distance.The results show that with the increase of arc distance,the stress decreases after welding.When the arc distance is0~10 mm,the deformation and hardness increase.When the arc distance is 20~40mm,the deformation and hardness are reduced.When the arc distance is 50 mm,the T-joint can not be fully penetrated.In the test,the T-joint of 8~12mm thick plate was welded by robot double side double arc welding with 30 mm arc distance and combined with the existing welding process.The test results show that the T-joint can achieve full penetration and unclean roots without groove opening,non-destructive flaw detection UT/MT inspection is qualified.There are no welding defects such as porosity,crack and slag inclusion in the weld.The weld surface is beautiful and reliable in quality.The width of vertical fillet weld is 15~18mm,and the convexity of convex fillet weld is less than 2mm,which meets the requirements of American Welding Code for fillet weld size width and convexity.No harmful widmanstatten was found through metallographic observation,the highest hardness of the welded joint was about230 HV,and the mechanical properties meet the requirements of《American Steel Structure Welding Code AWS D1.1》.