Research On Hybrid Palsma-MAG Welding Progress Of Q345B Steel

The rapid development of domestic railway has put forward higher requirements for welding of the bogie material. In the process of production we usually use MAG welding in the bogie welding process when we use medium thickness or thick steel plate. But there exists the following problems in the traditional MAG welding process:high deformation, large heat input, low efficiency and so on. Not only that, its working environmenti is poor,so it will have a huge impact on workers’health. However, Plasma -MAG hybrid welding have series of advantages such as low heat input, small joint deformation, high working efficiency, which are good for solving the problem existed in the welding process of medium thickness or thick steel plate.Article takes the normal material Q235B in the high-speed train bogie as the object of study, research on the Plasma-MAG hybrid welding of 10mm Q345B steel. Also we have a comparative analysis between Plasma -MAG hybrid welding and traditional MAG welding on formation of weld, organizational characteristics, mechanical properties, micro hardness, residual stress.Metallographic analysis shows that both the Plasma-MAG hybrid and the MAG welded joint consists of weld zone, base metal, incomplete recrystallization zone, fine grain zone, fusion zone, coarse grain zone. Compared withMAGwelding,the Plasma-MAG hybrid welding have less narrow HAZ.Both the Plasma-MAG hybrid and the MAG Micro-hardness measurement shows that the hardness of the weld zone and HAZ was higher than that of base metal which has the minimum hardness level. The maximum hardness was found at the coarse grain zone. The joints fractured at base metal which shows that the weld and HAZ has a higher strength than base metal. No micro cracks were observed on the joint surface after face bend test and back bend test with 180 degree. The impact tests show that the impact energy of the HAZ and weld zone is higher than that of the base metal.By means of blind-hole drilling method, we measure the residual stress of the welded joints. The results show that the residual stress of joint by using two kinds of process are for less than the yield stress of the Q345B, so we need not to eliminate the residual stress after welding.