Variable current & voltage cold metal welding technology and equipment is a new technology about cold arc welding, and greatly improving the traditional melting polar gas shielded arc welding technology.This technology is mainly adopted advanced electronic technology to actively control welding current waveform and voltage, to achieve the heat inputting controlling with the cooperation of droplet short transfer. Variable current & voltage cold metal welding technology can reduce significantly welding heat input and cladding layers dilution rate, and provide the quality of the cladding layers. Our company research and develop the technology of variable current & voltage cold metal stainless steel or copper alloy independently using for the inner wall of oil cylinder, and produce a series of variable current & voltage cold metal welding equipment using for the inner wall . Equipment composition Pulse welding power supply, high precision servo motor and cnc system. The mechanical oscillation, special water-cooling welding gun, water circulating cooling system, welding video tracking syst 1.Strengthening and repairing the inner wall of outside cylinder and middle cylinder of the hydraulic support column. 2.Strengthening and repairing the inner wall of roadheader retracting cylinder, petroleum pipeline and the cylinder, pipe, etc.