Filler metals are alloys or unalloyed metals which, when heated, liquefy and melt to flow into the space between two close fitting parts, creating a brazed or soldered joint. A filler metal has suitable melting and flow properties to permit distribution by capillary attraction in properly prepared joints. Filler metals produce joints that meet service requirements, such as strength and corrosion resistance. They also meet the specifications of the American Welding Society (AWS), The American Society for Testing Materials (ASTM), and in nearly all cases, ISO standards as well.
Standard filler metals include tin, lead, silver, lead-free, cadmium-free, sil-phos, copper, aluminum, nickel, and jewelers gold. Filler metals are found in solid form (such as rings and wire, slugs, washers, powder), as well as paste. Fusion filler metals are atomized into powder form and mixed with flux into a paste composition.