Two basic facts about laser cutting 316L: you must use nitrogen (not oxygen), otherwise the cut edge oxidizes and requires secondary processing; but nitrogen cutting has no exothermic oxidation, relying entirely on molten blow-off, so it is more sensitive to parameter matching — that is where dross comes from.
Quick diagnosis
Soft dross at the bottom (can be knocked off, sticky) is mostly caused by too slow a speed or too high power; hard dross at the bottom (cannot be knocked off, shiny) is mostly caused by too fast a speed or insufficient gas pressure. First determine which type it is, then adjust parameters — the adjustment directions for the two are completely opposite.
Why use nitrogen for 316L
- Oxygen cutting forms an oxide layer (blackening) on the cut edge, directly damaging the corrosion resistance of the stainless steel cut edge, requiring subsequent pickling or grinding;
- Nitrogen is an inert shield, leaving the cut edge silver-bright and essentially oxide-free, ready for welding or use immediately after cutting;
- The cost: no exothermic oxidation, so at the same power the cutting speed is slower than carbon steel, especially noticeable on thick plate.
Three forms of dross and adjustment directions
- Soft dross at the bottom (hanging but not falling, can be knocked off): too much molten material. Reduce power, increase speed, or lower gas pressure (excessively high pressure blows the melt pool too wide);
- Hard dross at the bottom (firmly adhered, shiny): molten material solidified before being blown away. Speed too fast or gas pressure insufficient — increase pressure, reduce speed;
- Rough side face, deep striations: incorrect focus position or dirty lens/nozzle. Check focus first, then nozzle.
Parameter ranges (reference, must be trial-cut per machine)
Different power levels and different machine brands vary greatly; the following is only directional reference:
- Gas pressure: nitrogen cutting of 316L commonly uses 10–14 bar (thinner plate can be lower, thicker plate needs higher); insufficient gas pressure is the most common cause of hard dross;
- Focus: 316L commonly uses negative focus (focus below the plate surface, about -1 to -3 mm depending on plate thickness); positive focus causes bottom dross;
- Speed: 30–50% slower than carbon steel of the same thickness; too fast causes hard dross, too slow causes soft dross and burning;
- Nozzle: diameter must match plate thickness; a dirty nozzle or poor concentricity directly causes one-sided dross.
An on-site diagnostic sequence
- First check the cut edge color: blackening indicates impure gas or oxygen contamination (check gas source purity and lines);
- Then check the dross form: soft dross — adjust speed/power; hard dross — adjust gas pressure/speed;
- Then check focus and nozzle: try a new nozzle on a test piece, which can eliminate half the problems;
- Only then touch program parameters: change only one variable at a time, otherwise you will never dial it in.
Common pitfalls
- Switching to oxygen to cut faster: the cut edge oxidizes and must be fully ground before welding, making it slower overall;
- The pressure gauge reading is a 'set value'; the actual pressure at the nozzle is affected by piping and the regulator, so verify it;
- Using thick-plate parameters on thin plate (excessively high pressure deforms thin plate);
- Relying on manual grinding to fix dross without investigating the root cause — in mass production the grinding cost will exceed the cutting cost;
- Ignoring the material surface condition: 2B and BA, cold-rolled hard and annealed states do not use exactly the same cutting parameters.
Tell us your plate thickness, machine power, gas type, and target cut-face quality, and we will give recommendations on material surface condition (2B/BA) and leveling precision for your process — dross is sometimes not a parameter issue but a matter of plate flatness and internal stress.
