Water heater equipment can do butt weld for metals including stainless steel, carbonsteel, copper titanium, and aluminium. Tt has featrres of butt-weld of straight seam, no work-piece deformation, no corrosion between crystals and one side weld, side forming excedllint qrality, high level automation and simple operation. The thickness of work-piece is between 0.3mm-2.0mm1.2mm-2.0mm2.5mm-8mm, welding speed can be adjusted continuosly steplessly.