Stainless steel marks with a fibre laser at a precision no other process matches: deep engraving, black marking or even colour marking, depending on the energy applied. This is strictly 1064 nm territory.
A fibre source is required
A blue diode or a CO2 will not mark bare steel: the metal reflects or dissipates the energy with no useful reaction. Only a 1064 nm fibre source is absorbed by steel.
There is a workaround: marking sprays and pastes (metal-oxide type) let a CO2 fix a black mark on steel. The result is decent but less fine than true fibre marking, and the consumable costs money.
Settings: what really matters
Three regimes depending on energy: annealing at low power and high frequency gives deep black without digging, ideal for instrumentation and medical parts; engraving at high power carves a grey groove; colour marking, in between, plays on oxide layers that are extremely sensitive to the slightest drift.
On stainless, pulse frequency and pass count matter as much as power: varying them at constant power is what takes you from grey to deep black.
Annealed marking does not survive sanding but resists corrosion very well, since it does not break the passive layer. Deep engraving opens the metal: on an exposed part it can start local rusting.
Risks and finishing
Reflections are the main risk: goggles for diode or CO2 do not protect against a 1064 nm beam. You must use goggles rated for that wavelength and work with the lid closed.
Fibre marking produces very fine metal fumes that need serious extraction and filtering — far more than wood engraving.
Degrease the part with alcohol before marking: a fingerprint is enough to leave a lighter patch. Afterwards, a dry cloth only, and nothing abrasive on an annealed mark.
Every figure on LaserSettings comes with the machine, the laser source, the material and the thickness it was tested on. A setting published for a 10 W diode says nothing about a 40 W CO2, and a setting for 3 mm says nothing about 6 mm: check those four things before you copy any number.
Settings are confirmed or disputed by the members who reproduce them, so reliability comes from cross-checking rather than popularity. Photos of the result — cut edges, engraving shades, scorching — tell you more than a single number found on a forum.
Whatever the material, treat a published setting as a starting point: run a small power/speed test grid on an offcut, clean the lens, redo the focus, work with fume extraction and air assist, wear glasses rated for your wavelength and never leave the machine unattended.