Dissimilar metal welding guide: filler selection for unlike metals, dilution control, buttering techniques, transition joints, and common dissimilar joint combinations.
Dissimilar metal joints come up constantly in fabrication: stainless handrails welded to carbon steel posts, nickel alloy overlay on carbon steel vessels, or copper-nickel pipe joined to steel flanges. Each combination creates a unique metallurgical situation where dilution, differential thermal expansion, and intermetallic compound formation can ruin the joint.
Filler metal selection is the critical decision. The filler must be compatible with both base metals and produce a weld deposit that resists cracking, corrosion, and mechanical failure. ER309L handles stainless-to-carbon-steel joints. ERNiCr-3 (Inconel 82) works for nickel alloy-to-stainless and nickel-to-carbon-steel joints. ERCuSi-A (silicon bronze) joins copper alloys to steel with low heat input.
Dilution is the percentage of base metal that melts into the weld deposit. High dilution shifts the weld chemistry toward the base metal, which can create brittle phases, hard zones, or corrosion-susceptible microstructures. Reducing dilution means using lower amperage, faster travel speed, and techniques that spread the arc across the joint rather than digging into one side.
Buttering is a two-step technique for difficult combinations. First, deposit one or more layers of compatible filler onto one base metal (the butter layer). Then join the buttered surface to the other base metal. This buffers the weld chemistry and reduces dilution effects. Common on high-alloy-to-low-alloy joints in pressure vessel and power plant work.
Not every dissimilar combination is weldable by fusion. Aluminum to steel, aluminum to copper, and titanium to steel all form brittle intermetallic compounds when melted together. These joints require mechanical fastening, explosion-bonded transition inserts, or specialized solid-state processes like friction welding.
How to butter a weld joint for dissimilar metals. ERNiCr-3 butter layer on carbon steel, dilution control, PWHT sequencing, and when buttering is required vs optional.
Why dissimilar metal welds fail from thermal expansion mismatch, brittle intermetallics, and galvanic corrosion. Filler selection strategy for joining unlike metals.
How bimetallic transition inserts connect unweldable metal combinations. Explosion bonding, roll bonding, and friction welding for shipbuilding, cryogenic, and heat exchangers.