Copper and brass are harder to laser weld than steel because copper reflects a meaningful portion of the beam at the roughly 1,070nm wavelength most fiber lasers run, and both metals conduct heat away from the weld pool far faster than steel does. The fix is not a different machine, it is more power concentrated in a smaller area, tighter focus control, and in most cases a pulsed or modulated setting rather than continuous wave.
Why Copper Fights the Laser
Pure copper reflects a large share of infrared laser light at room temperature, which is why early attempts at laser welding copper with lower-power systems often failed to get a stable keyhole going at all. Two things change that once you understand them: reflectivity drops sharply once the copper surface starts to melt, so the challenge is really about getting through that initial reflective window, and higher power density (rather than just higher average power) is what punches through it reliably.
Brass, being a copper-zinc alloy, behaves somewhat better than pure copper because the zinc content lowers the melting point and changes the surface absorption slightly, but it introduces its own issue: zinc volatilizes at a much lower temperature than copper melts, so brass welding shares some of the same fume and porosity concerns as galvanized steel, just from an alloy constituent rather than a coating.
Copper vs. Brass vs. Steel: Key Differences for Laser Welding
| Copper | Brass | Mild Steel (for comparison) | |
|---|---|---|---|
| Melting point | 1,984°F | ~1,700°F (varies by alloy) | ~2,500°F |
| Thermal conductivity | Very high, pulls heat away from the weld pool fast | High, moderated by zinc content | Moderate |
| Reflectivity at 1,070nm | High until surface melts | Moderate to high | Low |
| Typical power needed vs. equivalent steel thickness | 1.5x to 2x higher | 1.2x to 1.5x higher | Baseline |
| Main defect risk | Lack of fusion from reflected energy | Zinc porosity, similar to galvanized | Standard porosity/undercut |
Settings and Technique That Work
A few adjustments consistently improve copper and brass results on a handheld fiber laser:
- Run higher power density, not just higher average power. A tighter spot size concentrates energy enough to break through the initial reflective window faster, which reduces the chance of an unstable start to the weld.
- Consider pulsed or modulated mode over continuous wave for thinner copper sections. The pulsing lets the surface begin absorbing more efficiently once melting starts, without dumping continuous heat that just conducts away.
- Slow travel speed relative to an equivalent steel joint. Because heat conducts away from the pool so quickly in copper, a speed that works fine on steel often will not hold a stable pool on copper of the same thickness.
- Use a shielding gas suited to the alloy. Argon is the standard choice for both copper and brass; nitrogen is occasionally used on copper for cost reasons but changes weld appearance and should be tested on scrap first.
- On brass, treat fume control the same as galvanized steel. Extraction positioned close to the weld point matters just as much here as it does on zinc-coated steel, for the same reason: zinc oxide fume.
What Copper and Brass Laser Welding Is Actually Used For
The two most common applications fabrication and manufacturing shops bring to us are electrical and battery connections (busbars, terminals, battery tabs) where copper’s conductivity is the entire point of the part, and decorative or repair work on brass fixtures, musical instruments, and architectural hardware where a clean, low-distortion joint matters more than raw throughput. Both applications benefit from the same core advantage a handheld fiber laser has over TIG on these metals: a much smaller heat-affected zone, which matters enormously on thin copper busbar stock or brass parts where warping ruins the piece. Our team has set up machines for both applications and the power density adjustment above is the one change that fixes the vast majority of failed copper welds we get support calls about.
Frequently Asked Questions
Can a handheld fiber laser welder weld copper?
Yes, but it needs more power density than the same joint would on steel, because copper reflects a significant portion of the beam until the surface begins to melt. Once welders understand that initial reflective window, copper welds reliably.
Why is copper harder to weld with a laser than steel?
Two reasons: copper reflects more of the laser’s infrared wavelength than steel does, and it conducts heat away from the weld pool much faster, which makes it harder to sustain a stable melt pool.
Does brass weld easier than pure copper?
In some respects, yes, because the zinc content lowers the melting point and changes surface absorption. But brass introduces zinc fume and porosity concerns similar to galvanized steel, so it trades one challenge for another rather than being simply easier.
What settings should I start with for copper on a fiber laser welder?
Start with higher power density than you would use on steel of the same thickness, slower travel speed to compensate for copper’s fast heat conduction, and consider pulsed mode on thinner sections. Test on scrap of the exact alloy and gauge before running production parts.
Copper and brass work is one of the more technical applications our customers run, and we walk through settings on your specific alloy during setup on any machine you buy from us. See the lineup on our products page, review specs on our fiber laser welding page, or request a free quote for the machine best suited to reflective or high-conductivity metals. Call (615) 333-7284 with questions before you buy.
