XQHB CO2 BACKING WELD MACHINE This machine is made for the purpose of CO2 gas shield welding on the box-beam that has finished the assembling. The box-beam after assembling will be transported to the gas shield welding position, then adjust the welding gun unit to make sure the CO2 welding head is pointing to the welding seam. Then the machine is running straight line on the rails, then the machine can achieve the automatic CO2 gas shield welding on the flat welding seam of box-beam bevel edge.