Soldering is a method of joining parts with molten auxiliary material, the so-called solder with the melting point lower than the components to be joined. It is customary to distinguish the so-called soft and hard soldering, depending on the melting point of the solder. Solders with the melting point of up to ca. 450°C are referred to as soft, above the temperature, as hard. Soldering methods may be distinguished mainly by the method of heating the soldered parts and solder. In the larger extent, we heat soldered objects and solder with hot gas flow or flame. Hard soldering ensures greater weld strength; it is used, for instance, for soldering aluminium or copper pipes. For soft soldering, a natural gas flame with air is sufficient; the hard soldering requires warmer oxygen-acetylene or oxygen-hydrogen flame.