Welding is a process in which the sheet is bonded to the sheet by heating or pressurizing or without filling the material. Welding can be divided into three major categories: fusion welding, pressure welding and brazing depending on the state of the metal. Fusion welding: A welding method in which the sheet is heated but not pressurized. Brazing: Using a material lower than the melting point of the sheet as a brazing material, the sheet and the brazing material are heated to a temperature higher than the melting point of the brazing material and lower than the melting point of the sheet, and the sheet is wetted by the liquid brazing material to spread the materials to achieve the purpose of welding.