Guide to Welding Different Metals

Every metal has unique welding characteristics determined by its chemistry, thermal conductivity, melting point, and susceptibility to cracking. Welding carbon steel is fundamentally different from welding aluminum, which is fundamentally different from welding titanium. Use the wrong filler, skip preheat on a high-carbon alloy, or run too much heat into stainless, and you’ll get cracks, warping, or a joint that fails in service.

Mild steel is where most welders start. Low carbon content makes it forgiving across every process, and it’s the cheapest base metal to practice on. Stainless steel demands tighter heat control, proper gas coverage, and matched filler to maintain corrosion resistance. Aluminum requires completely different technique: AC TIG or spray-transfer MIG, pure argon shielding, and scrupulous cleaning to remove the oxide layer.

Beyond the big three, specialty metals present their own challenges. Cast iron repair requires careful preheat and nickel-based electrodes to prevent cracking. Chromoly (4130) needs controlled heat input and often post-weld heat treatment. Galvanized steel generates toxic zinc fumes that demand proper ventilation and technique adjustments to manage porosity.

High-performance alloys push the limits of welding skill. Titanium requires 100% inert gas coverage on both sides of the joint, plus trailing shields and purge chambers. Nickel alloys like Inconel are hot-crack sensitive and demand tight heat input control. Tool steel repair follows strict preheat and PWHT (post-weld heat treatment) protocols to prevent brittle failures.

Then there are the joints that involve two different metals. Dissimilar metal welding covers filler selection, dilution control, and buttering techniques for joining unlike materials. Copper and brass welding fights high thermal conductivity. Wear plate like AR400 and Hardox requires low-hydrogen processes and careful HAZ management.

This section covers the welding metallurgy you actually need: process selection, filler metal compatibility, preheat and interpass temperature requirements, shielding gas choices, and the common defects specific to each material. Each material guide includes starting parameters you can take straight to the shop.