Welding heating temperature lower than 450 ℃ is called soldering

 The welding heating temperature is lower than 450 ℃ called soft soldering, and soft soldering is mostly used for the welding of conductive, airtight and watertight devices in the electronics and food industries. Tin-lead alloy as the solder is most commonly used. The solder generally needs to use a flux to remove the oxide film and improve the wetting performance of the solder. There are many types of flux, and rosin alcohol solution is used for soft soldering in the electronics industry. The residue after soldering of this kind of flux has no corrosive effect on the workpiece and is called non-corrosive flux. The flux used when welding copper, iron and other materials is composed of zinc chloride, ammonium chloride and petroleum jelly. When welding aluminum, it is necessary to use fluoride and fluoroborate as the flux, and also use hydrochloric acid and zinc chloride as the flux. The residue after welding of these fluxes has a corrosive effect, which is called corrosive flux, which must be cleaned after welding.