Can 304 stainless be laser cut?
Yes. Fiber lasers cut 304 cleanly to about 20-25 mm (1"). Specify nitrogen assist for a bright, oxide-free edge that welds and passivates without cleanup.
304 sheet and plate is one of the most common laser-cut materials. A fiber laser cuts it with either oxygen or nitrogen assist gas, and the choice sets the edge quality. Nitrogen is the normal call: it is inert, the melt is blown out of the kerf without burning, and the edge comes out bright, oxide-free and ready for welding, powder coating or passivation. Oxygen assist cuts faster on thick plate but leaves a dark chromium-depleted oxide film that must be ground or pickled off before the part is welded or put into corrosive service.
Typical thickness range with nitrogen is 0.5-20 mm (0.02-0.8") on a 6-12 kW fiber; high-power machines reach 25-30 mm (1.0-1.2"), but edge quality and squareness fall off above about 12 mm (0.5"), and waterjet becomes the better choice for thick, tight-tolerance profiles. Kerf runs 0.1-0.3 mm (0.004-0.012") on thin gauge and about 0.4-0.6 mm on plate. Position tolerance of ±0.1 mm (±0.004") on sheet and ±0.2-0.3 mm on plate is standard from a job shop.
The heat-affected zone is small, a few tenths of a millimetre, and does not sensitize 304 in sheet gauges. The edge is slightly harder from rapid cooling, which shows up as tool wear on a subsequent tap or ream. Dross on the bottom edge is minimal with nitrogen at the right pressure; a small burr is normal and deburring should be specified if it matters. Protective film on brushed or polished sheet can be left on during cutting on most machines; say so if the cosmetic side must stay unmarked.
Laser Cutting for 304 parts: where to send them
What to specify
- Material and finish: 304 or 304L per ASTM A240, 2B (mill), #4 brushed or #8 polished, and which side is cosmetic
- Nitrogen assist (oxide-free edge) unless the part will be fully machined or coated afterwards
- Thickness, and a flatness note if the sheet must lay flat after cutting; cut parts release rolling stress
- Edge condition: as-cut, deburred, or dross-free; and a maximum burr height if the part is handled
- Hole size relative to thickness: keep holes at least equal to the thickness for a clean laser hole, or note that holes will be drilled
- Grain direction for brushed sheet if parts will be side by side in an assembly
- Protective film left on during cutting, and whether it must be removed before shipping
Pitfalls
- Oxygen-cut edges left unground under a weld or in wet service; the oxide rusts and the weld is contaminated
- Small holes in thick plate (under one thickness in diameter) come out tapered and rough; drill them instead
- Sharp inside corners on a nested part cannot be smaller than the kerf radius; model a small radius
- Cosmetic film scorched or peeled by the cutting head on the wrong side of the sheet
- Warped parts from long thin ribs; add tabs or cut in a different order, or use plate that has been stress-relieved
- Expecting a machined edge finish on 20 mm plate; striations and slight taper are normal there
Frequently asked questions
- How thick can a laser cut 304 stainless?
- Most job shops cut up to 20 mm (0.8") with nitrogen and up to about 25 mm (1") with oxygen or a very high-power fiber. Edge quality is best under 12 mm (0.5"); above that, waterjet competes on quality.
- Does laser cutting affect the corrosion resistance of 304?
- Not with nitrogen assist; the edge is bright and passive. An oxygen-cut edge carries a chromium-depleted oxide that will rust and should be ground or pickled off. The small heat-affected zone does not sensitize sheet gauges.
- Can laser-cut 304 edges be welded without preparation?
- Yes, if the part was cut with nitrogen. A clean, oxide-free edge welds directly. Oxygen-cut edges need to be ground back to bright metal first.
