Material-Pair Difficulty Matrix
Rated easy / moderate / hard / expert / specialty across 8 common metals. Tap a cell for filler, gas, IMC concerns, and the operator stage required.
| Mild Steel | Stainless | Aluminum | Copper | Brass | Titanium | Nickel | Galvanized | |
|---|---|---|---|---|---|---|---|---|
| Mild Steel | easy | moderate | hard | expert | hard | specialty | moderate | moderate |
| Stainless | easy | hard | expert | hard | moderate | easy | hard | |
| Aluminum | moderate | expert | hard | specialty | hard | hard | ||
| Copper | hard | moderate | specialty | hard | specialty | |||
| Brass | moderate | specialty | hard | specialty | ||||
| Titanium | specialty | specialty | — | |||||
| Nickel | moderate | hard | ||||||
| Galvanized | hard |
Notable specifics
Aluminum. 5xxx and 6xxx series weld differently. 6xxx (heat-treatable, magnesium-silicon) hot-cracks on autogenous welds — needs 4043 or 5356 wire as filler. 5xxx (work-hardenable, magnesium) welds autogenously fine. Most operators learn this the hard way on a 6061 boat repair.
Copper. Reflectivity at 1064 nm is 95%+. Fiber laser welding copper requires either green (515 nm) or blue (450 nm) lasers, or pulsed fiber with very high peak power to break through reflectivity. Standard CW fiber lasers don't weld copper reliably.
Galvanized. Zinc boils at 907°C, well below steel's melting point. The zinc gas blows the puddle apart. Solutions: pre-clean with laser cleaner, use deliberate vent gap, accept porosity and post-weld inspect.
Titanium. Atmospheric contamination during welding causes embrittlement. Requires trailing shield gas, sometimes argon-flooded enclosure. Color-coded by post-weld appearance: silver (good), straw (acceptable), blue (marginal), gray (rejected), white (severely contaminated, scrap).