Soldering is a joining process whereby a non-ferrous filler metal, alloy is heated to melting temperature (below 800°F) and distributed between two or more close-fitting parts by capillary attraction. At its liquidus temperature, the molten filler metal interacts with a thin layer of the base metal, cooling to form a strong, sealed joint due to grain structure interaction. The soldered joint becomes a sandwich of different layers, each metallurgically linked to each other.
The process of soldering can employ various heat sources such as torch, flame, acetylene, gas/air, induction, resistance, infrared, oven, and furnace. The soldering process employs filler metals and alloys such as tin, lead, silver, antimony, indium, bismuth etc. Flux is necessary for soldering to remove and prevent reformulation of surface oxides on the base metals.
Soldering produces strong, sealed, leak-proof joints. The soldering process uses filler metals in solid form (such as rings and wire, slugs, washers, powder) as well as soldering paste. Proper soldering begins with a good joint design.
The soldering process produces joints that meet specifications that meet mechanical performance, electrical conductivity, pressure tightness, corrosion resistance, and service temperature. High production, metal joining operations often employ soldering.