Registrieren | Einloggen Derzeit keine Preisbindung

The World of precious Metals

Description of the Method

When talking of soldering, we generally mean gap soldering. This means that the capillary effect of a narrow gap is used to fill the joining point. The driving force is the capillary filling pressure. The optimum gap width for gap soldering is between 0.05 and 0.2 mm. As a result of the influence of the capillary filling pressure, soldering gaps are also filled with liquid solder against the force of gravity. The capillary pressure is of decisive importance for brazing. This is formed after wetting the solder in narrow soldering gaps. Good wetting first requires metallically clean abutting surfaces. Flux, protective gas or vacuum are used to ensure such metallically clean surfaces for base material and solder. Thus, press fits should be avoided because when fluxes are used, small amounts of this are required to eliminate oxide skins on the surfaces to be joined. Minimum gap widths are thus considered necessary for copper and are also taken into account in the component tolerances. This has the result that the use of permissible pipes and fittings in terms of process safety is of decisive importance. However, the controls also prescribe the overlapping lengths or insertion depths of pipe-socket joints which are responsible for the adequate strength of the soldering point. The permissible fittings for installations now without exception have insertion depths suitable for soft soldering with its lower weight-carrying strength.

The solder ends to be joined (copper pipe and fitting) must be clean and free from grease. Metal-free cleaning cloths should be used for cleaning, with any grooves produced by the mechanical processing ideally running in the longitudinal direction of the pipe since this improves the soldering.

The heat sources to be used depend on the soldering temperature and the size of the components. Thus, propane-air and acetylene-air torches are completely adequate for soft soldering. Heating using electrical resistance equipment is used for Cu pipes up to 22 mm which specifically eliminates any risk of fire in old buildings, building renovations and repairs. Acetylene-oxygen mixtures such as those available in principle at any building site are generally used for higher working temperatures. When changing the soldering method from brazing to soft soldering, consideration should also be given to the heating sources in order to ensure correct heating.
Any overheating should be completely avoided.