Oxygen-Assist for 2 mm Mild Steel: Safety, Pressure & Speed Window

CO₂ lasers are not the primary choice for steel, but with oxygen-assist, they can cut 2 mm mild steel effectively when needed. This guide gives the real cutting window for 150 W CO₂ — including ~1 MPa oxygen pressure, focal position, speed ranges, and post-cut expectations — while emphasizing the safety controls required for oxygen handling.

⚠️ Oxygen-assist cutting must be treated as a flame-supported process. Correct regulators, hoses, and fire-back protection are mandatory.
GWEIKE M-Series 6-in-1 CO₂ Lasers Cut Stainless Steel CO₂ Laser Cutting Machines

Why oxygen-assist is needed for CO₂ cutting of steel

CO₂ lasers alone do not melt mild steel efficiently. Instead, oxygen supports an exothermic oxidation reaction that provides additional heat to drive the cut. This is different from fiber or nitrogen-based melt cutting.

In short: CO₂ + O₂ = reactive flame cutting (not pure melting).

O₂ safety — mandatory controls

Because O₂ accelerates combustion, proper delivery equipment is critical.

✅ Required system components

What is flashback?

Reverse flame traveling into hoses → potentially into bottle → explosion risk.

Prevent flashback

⚠️ Never use oil/grease on oxygen fittings. Hydrocarbons + O₂ under pressure → explosive.

Recommended oxygen pressure (~1 MPa)

CO₂ + O₂ cutting of 2 mm mild steel typically uses ~1 MPa (≈ 10 bar) at the nozzle.

For 2 mm steel, 0.8–1.0 MPa is the practical window.

Nozzle & focal position

Nozzle

Focal position

Place focus ~20–30% into material thickness → ~0.4–0.6 mm into steel.

Bottom dark + heavy slag → lower focus slightly.

Speed window (150 W CO₂)

From GWEIKE application data:

Material Thickness Power O₂ Pressure High speed Best speed
Mild Steel 2 mm 150 W ~1 MPa ~3 mm/s ~1 mm/s

CO₂ cuts will show dark/oxidized edges (normal for O₂ flame cutting).

Faster → less HAZ, but risk of incomplete penetration Slower → more HAZ + rough edges → Always start at ~1 mm/s → tune upward

What happens during O₂ cutting

Compared with fiber melt cutting, O₂ CO₂ cutting has:

→ Good for emergency steel cutting, prototypes, small jobs. → Not ideal for continuous metal production.

CO₂ vs fiber for 2 mm steel

CO₂ + O₂ Fiber
Can it cut? ✅ Yes ✅ Yes
Speed Slow Fast
HAZ High Low
Edge Color Black/oxidized Cleaner
Per-piece cost Higher Lower
Best Use Emergency Production

If steel is routine → upgrade to GH Series (fiber) For occasional work → M-Series CO₂ is sufficient.

Standard operating procedure (SOP)

  1. Verify O₂ source + regulator + check valve
  2. Clean optics; align nozzle
  3. Place focus ~0.4–0.6 mm into steel
  4. Set O₂ = 0.8–1.0 MPa
  5. Start at ~1 mm/s
  6. Inspect bottom → adjust focus / speed
  7. Record: pressure / speed / focal offset / nozzle

Troubleshooting

Symptom Cause Fix
Not cutting through Speed too fast; focus too high Slow down; lower focus 0.2–0.4 mm
Heavy dross O₂ too low; nozzle large Increase O₂; use smaller nozzle
Top bright; bottom dark Focus too high Lower focus
Excessive blackening Speed too slow → overreaction Increase speed slightly
Spray sparks Unstable gas flow Check regulator + hose
Cut unstable Dirty optics Clean lens/mirrors

Example — 150 W CO₂ cutting 2 mm mild steel

Result: ✅ Fully penetrated ✅ Stable kerf ⚠️ Dark edge + HAZ (normal)

Safety cautions

Pick the right tool

GH Series (Fiber — Metal Production) GA Series (Fiber) M-Series (CO₂ — Occasional Steel)

FAQ: Oxygen-assist for 2 mm mild steel

Can CO₂ cut 2 mm mild steel?

Yes — with oxygen at ~1 MPa and proper focus.

Why is the edge black?

Because O₂ supports oxidation — flame cutting, not melt cutting.

Best speed?

~1 mm/s (150 W CO₂). Start here → increase if penetration stable.

Do I need special hoses?

Yes — oxygen-rated hoses only; no oil or grease.

What prevents backfire?

Check valves / flashback arrestors + stable regulation.

Is fiber better?

Yes — faster, cleaner, cheaper per part. CO₂ is fine for emergencies.