Process description

The principle of inert gas brazing with localized heating can be explained as follows: The components to be brazed are brought to brazing temperature in an inert gas chamber by resistance or induction heating under argon 4.6, nitrogen 4.6 or forming gas with 5% hydrogen. If solder is deposited near a gap, it is melted and flows into the soldering gap by capillary action. This distinguishes soldering with localized heating from oven soldering. While furnace brazing requires an extremely dry and pure shielding gas to produce high-quality joints on Cr-Ni steels, a shielding gas with 100 vpm impurities can also be used for localized heating. With such a shielding gas, Cr-Ni steels with solders made of copper, copper-silver, copper-silver-zinc, copper-manganese-cobalt, copper-manganese-nickel, copper-nickel, silver-manganese, nickel-chromium and iron-nickel-chromium.
 

Avoid under-carburization and over-carburization

Two phenomena must be taken into account when brazing carbide-steel joints. If the joint experiences an increase in carbon content (carburization) at the joining temperature, graphite will form in the joining zone and the joint will fail prematurely. If the carbon content is reduced (under-carburization), the dreaded n-phase occurs, which also leads to premature fracture of the joint under load. The diagram shows the effect of under- or over-carburization on the flexural strength. It can be clearly seen that the effect of under-carburization is more severe than that of over-carburization. The bending strength decreases more with under-carburization than with over-carburization. Suitable technological measures prevent the formation of graphite and the undesirable n-phase in the joining zone.