Table of Contents
Carbon steel and stainless steel share the same welding process on a fiber laser, but they are not interchangeable in their parameter windows. The same power level, same thickness — carbon steel consistently requires 15% to 46% more peak power than stainless. At 1KW welding 2 mm sheet, carbon steel runs at 95% peak power; there is almost no adjustment margin left.
This guide gives you the complete validated parameter tables for carbon steel across four power levels and every standard thickness increment from 0.5 mm to 6.0 mm — along with the logic behind the numbers so you can make confident adjustments when your specific joint or surface condition doesn't match a row exactly.
Choose the Right Power Level
Before setting any individual parameter, confirm your machine's output covers the material thickness you're welding. Carbon steel requires significantly higher peak power than stainless at the same thickness, which compresses the available adjustment window on lower-power systems.
0.5 – 2.0 mm
Brackets, thin enclosures, light sheet. At 2 mm, peak power reaches 95% — almost no headroom remains.
0.5 – 3.0 mm
Most common workshop range. Good adjustment margin on 1–2 mm. Can reach 3 mm with 1.6 mm wire at 85% peak power.
0.5 – 4.0 mm
Structural parts and thicker frames. Comfortable parameter windows across the full range through 4 mm.
0.5 – 6.0 mm
The only level that reaches 5–6 mm plate. Wide operating window on all thicknesses below 4 mm.
Why Carbon Steel Needs Different Settings Than Stainless
Carbon steel and stainless share the same basic laser welding process, but four material differences force meaningful changes across every parameter group.
Higher thermal conductivity means higher peak power
Carbon steel dissipates heat faster than stainless steel. To build and maintain a stable melt pool, you need to deliver more energy into the joint. The gap is largest at lower power levels and smaller thicknesses, and narrows as power increases.
| Power | Thickness | Carbon steel — peak power | Stainless steel — peak power | Difference |
|---|---|---|---|---|
| 1KW | 1.0 mm | 56% | 56% | — |
| 1KW | 2.0 mm | 95% | 65% | +46% |
| 1.5KW | 2.0 mm | 67% | 45% | +49% |
| 2KW | 2.0 mm | 50% | 35% | +43% |
| 2KW | 4.0 mm | 75% | 65% | +15% |
| 3KW | 3.0 mm | 40% | 33% | +21% |
Oxidation tendency affects gas shielding
Carbon steel oxidizes readily at welding temperatures. Use nitrogen at ≥ 20 L/min as shielding gas — the same requirement as stainless steel. Unlike stainless, carbon steel can tolerate small amounts of CO₂ in a mixed shielding gas (Ar + CO₂ blends are common in MIG welding), but for fiber laser welding nitrogen remains the cleaner, lower-risk choice that produces consistent surface appearance across batches.
Focus position
Set focus position to 0 mm (on surface) for carbon steel — identical to stainless steel. This is different from aluminum, which requires +3 to +5 mm above the surface due to its higher reflectivity and the way the melt pool forms on that material.
Wire selection
ER70S-6 is the standard wire choice for carbon steel laser welding. It contains higher levels of silicon and manganese as deoxidizers, which counteract contamination common on hot-rolled carbon steel. On very clean, pickled, or machined surfaces ER70S-2 also works well and gives a slightly cleaner bead appearance. Both are cold-wire, solid-wire feeds — the same general type used for stainless, just a different alloy specification.
Complete Parameter Tables
All values below are from validated tests on GWEIKE M-Series fiber welding systems. Use these as starting points and fine-tune ±5% based on your specific joint fit-up, surface condition, and wire angle. PWM duty cycle is 100% and PWM frequency is 1000 Hz for all entries — these do not change.
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 0.5 | — | — | 35% | 150 | 1.5 |
| 0.8 | 0.8 | 18 | 50% | 100 | 2.5 |
| 1.0 | 0.8 | 18 | 56% | 100 | 2.5 |
| 1.2 | 1.0 | 15 | 56% | 100 | 3.0 |
| 1.5 | 1.2 | 12 | 60% | 50 | 3.5 |
| 2.0 ⚠ limit | 1.2 | 12 | 95% | 30 | 3.5 |
At 2.0 mm, the 1KW system operates at 95% peak power with no meaningful adjustment margin. For regular production at 2 mm carbon steel, a 1.5KW system provides a more stable operating window.
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 0.5 | — | — | 23% | 150 | 1.5 |
| 0.8 | 0.8 | 18 | 33% | 100 | 2.5 |
| 1.0 | 0.8 | 18 | 38% | 100 | 2.5 |
| 1.2 | 1.0 – 1.2 | 15 | 38% | 100 | 3.0 |
| 1.5 | 1.2 | 12 | 40% | 100 | 3.0 |
| 2.0 ⚠ shift | 1.2 | 12 | 67% | 30 | 3.5 |
| 2.5 | 1.2 | 10 | 70% | 30 | 4.0 |
| 3.0 | 1.6 | 8 | 85% | 30 | 4.5 |
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 0.5 | — | — | 17% | 150 | 1.5 |
| 0.8 | 0.8 | 18 | 22% | 100 | 2.0 |
| 1.0 | 0.8 | 18 | 25% | 100 | 2.0 |
| 1.2 | 1.0 | 15 | 25% | 100 | 2.5 |
| 1.5 | 1.2 | 12 | 30% | 100 | 3.0 |
| 2.0 ⚠ shift | 1.2 | 12 | 50% | 30 | 3.0 |
| 2.5 | 1.2 | 10 | 50% | 40 | 3.5 |
| 3.0 | 1.2 – 1.6 | 8 | 60% | 30 | 4.5 |
| 3.5 | 1.6 | 8 | 65% | 30 | 4.5 |
| 4.0 | 1.6 | 6 | 75% | 30 | 4.5 |
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 0.5 | — | — | 12% | 150 | 1.5 |
| 0.8 | 0.8 | 18 | 15% | 100 | 2.0 |
| 1.0 | 0.8 | 18 | 17% | 100 | 2.0 |
| 1.2 | 1.0 | 15 | 17% | 100 | 2.5 |
| 1.5 | 1.2 | 12 | 20% | 100 | 3.0 |
| 2.0 ⚠ shift | 1.2 | 12 | 33% | 30 | 3.0 |
| 2.5 | 1.2 | 10 | 33% | 40 | 3.5 |
| 3.0 | 1.2 – 1.6 | 8 | 40% | 30 | 4.5 |
| 3.5 | 1.6 | 8 | 44% | 30 | 4.5 |
| 4.0 | 1.6 | 6 | 50% | 30 | 4.5 |
| 4.5 | 1.6 | 6 | 54% | 25 | 4.5 |
| 5.0 | 1.6 | 6 | 60% | 20 | 4.5 |
| 5.5 | 1.6 | 6 | 67% | 20 | 5.0 |
| 6.0 | 1.6 | 6 | 75% | 20 | 5.0 |
Three Rules That Explain the Data
The four tables above aren't arbitrary numbers. They follow consistent engineering logic across all power levels. Understanding these three rules lets you make confident adjustments when your specific joint or surface condition doesn't match a row exactly.
Rule 1 — Wire diameter steps with thickness
Wire diameter is not a free variable — there is a predictable step pattern that holds across all four power levels. Choosing a wire that is too thin for the thickness gives a narrow, peaked bead with poor gap tolerance. Too thick, and wire delivery stalls or the bead gets irregular.
Thin sheet (≤ 1.0 mm)
- Wire diameter: 0.8 mm
- Wire speed: 18 mm/s
- The small wire diameter matches the narrow melt pool on thin sheet and avoids overloading the pool with filler material.
Mid sheet (1.2 – 2.5 mm)
- Wire diameter: 1.0 – 1.2 mm
- Wire speed: 10 – 15 mm/s
- Steps up to match increasing pool volume. At 1.2 mm thickness, either 1.0 or 1.2 mm wire works — let joint geometry decide.
Transition zone (3.0 mm)
- Wire diameter: 1.2 – 1.6 mm
- Wire speed: 8 mm/s
- Both wire sizes appear in the data at 3 mm. Start with 1.2 mm and step up to 1.6 mm if bead fill is insufficient.
Thick plate (≥ 4.0 mm)
- Wire diameter: 1.6 mm
- Wire speed: 6 mm/s
- Larger wire is needed to fill the wider melt pool and maintain bead height. Speed drops further as thickness increases toward 6 mm.
Rule 2 — Scan width tracks thickness
Scan width controls how broadly the laser energy is distributed across the joint. A narrower scan concentrates heat for penetration; a wider scan covers more surface area for gap bridging and bead appearance.
0.5 mm
Scan width: 1.5 mm. Minimum width — at this thickness the melt zone is tiny and widening further risks burn-through on the edges.
0.8 – 1.0 mm
Scan width: 2.0 – 2.5 mm. Widens slightly with the growing melt pool. This range allows bridging of small fit-up gaps up to ~0.5 mm.
1.2 – 2.0 mm
Scan width: 2.5 – 3.5 mm. The range where most structural fabrication work sits. Width increases with thickness to keep energy density manageable.
2.5 – 6.0 mm
Scan width: 3.5 – 5.0 mm. Wide beam distribution needed to drive penetration through thick section without creating an excessively narrow keyhole.
Rule 3 — The 2 mm scan frequency threshold
This is the most important pattern in the data, and the one most operators get wrong when moving from thin-sheet to thicker carbon steel for the first time. Scan frequency is not a continuous dial — it makes a step change at 2 mm, and carrying the wrong setting across that line produces predictable failure modes.
≤ 2 mm — Use 100 Hz (150 Hz for 0.5 mm)
- Priority Prevent burn-through
- Mechanism Fast oscillation distributes heat broadly
- Typical scan width 1.5 – 3.5 mm
- Scan frequency 100 – 150 Hz
> 2 mm — Drop to 20 – 40 Hz
- Priority Ensure full penetration
- Mechanism Slow oscillation concentrates heat downward
- Typical scan width 3.5 – 5.0 mm
- Scan frequency 20 – 40 Hz
Troubleshooting Carbon Steel Welds
Most problems with carbon steel laser welds fall into four categories. Each has a predictable cause that maps directly back to a parameter adjustment.
🔴 Black or brown surface oxidation
Cause: Insufficient nitrogen shielding. Nozzle too far from the surface, flow rate below 20 L/min, or crosswind in the workspace disrupting the gas coverage.
Fix: Verify N₂ flow is ≥ 20 L/min at the nozzle exit. Reduce nozzle standoff to 8–12 mm. If oxidation persists on 2 mm+ plate, reduce peak power by 3–5% to lower total heat input — a cooler weld stays under the oxidation threshold longer during cooling.
⚡ Burn-through on thin plate (≤ 1.5 mm)
Cause: Peak power too high for the thickness, scan width too narrow concentrating energy, or focus position drifted from 0 mm.
Fix: Raise scan frequency to 150 Hz. Widen scan to 2.5 mm. Reduce peak power in 3% steps. Confirm focus is at exactly 0 mm — defocusing often makes thin-plate burn-through worse, not better, by reducing energy density unpredictably.
📉 Lack of fusion on plate thicker than 2 mm
Cause: Scan frequency too high (carried over from a thin-plate setup), scan width too narrow, or peak power insufficient for the actual measured thickness.
Fix: Drop scan frequency to 30 Hz. Widen scan to 4.0–4.5 mm. Increase peak power by 5%. Cut a cross-section on a scrap piece to verify penetration depth before continuing production. Full fusion should extend through the material thickness with no visible unbonded root.
💥 Excessive spatter
Cause: Peak power too high relative to thickness, or mill scale / rust on the weld area trapping gases and causing violent ejection from the melt pool. Mill scale is the most common spatter cause on hot-rolled carbon steel and is frequently overlooked.
Fix: Reduce peak power by 3–5%. Grind or laser-clean the weld zone — a cleaning pass at low power before welding removes mill scale without grinding, especially useful on the GWEIKE M-Series 6-in-1 systems where the cleaning function is built in. On galvanised or coated material, the coating must be removed from the weld zone before welding regardless of power level.
Test these parameters on your material
The values in this guide come from GWEIKE M-Series validation runs. If your production material, joint geometry, or surface condition differs from standard test conditions, the most reliable next step is a test weld before committing to a production run. Our applications team can arrange this.
FAQ
Why does carbon steel need more peak power than stainless at the same thickness?
Carbon steel has higher thermal conductivity than austenitic stainless steel — it conducts heat away from the weld zone faster. To maintain a stable melt pool that achieves full penetration, you need to input more energy per unit time. At lower power levels this difference is most pronounced: at 1KW welding 2 mm, stainless needs 65% peak power while carbon steel needs 95%. As total machine power increases, the gap shrinks in percentage terms because you have more headroom above the minimum required energy input.
Can I use the same nitrogen flow rate as stainless steel?
Yes — ≥ 20 L/min nitrogen applies to both materials. Carbon steel is actually more sensitive to gas coverage interruptions than stainless because it oxidizes faster and more visibly at elevated temperatures. If you see brown or black discoloration on the weld surface, inadequate gas coverage is the first thing to check before adjusting any other parameter.
What happens if I don't change scan frequency when going from 1.5 mm to 3 mm?
If you carry the 100 Hz scan frequency setting from 1.5 mm work to 3 mm plate, the beam moves too fast to build up enough thermal energy at the root of the joint. The top surface may look well-fused, but a cross-section will typically show incomplete penetration of 30–50% of the material thickness. The weld fails a bend test or shows a visible cold lap at the root. Drop scan frequency to 30 Hz and widen scan to 4.0–4.5 mm when crossing the 2 mm threshold.
Can a 1KW fiber laser weld 2 mm carbon steel reliably?
Technically yes — the parameter table shows it at 95% peak power — but it is not a comfortable operating condition for production. At 95% peak power there is almost no margin to compensate for surface variation, joint gap, or focus drift. Any contamination on the surface, any slight increase in joint gap, or any focus drift toward the surface will immediately cause incomplete fusion. For occasional 2 mm work a 1KW system can do it; for regular production at 2 mm, a 1.5KW system is the more reliable choice.
Does mill scale on hot-rolled steel affect welding parameters?
Yes, significantly. Mill scale — the oxide layer on hot-rolled carbon steel — has very different laser absorptivity, melting point, and gas-trapping behavior compared to bare steel. It is the most common source of excessive spatter and porosity on carbon steel laser welds. The tables in this guide are for clean steel surfaces. On hot-rolled material, either grind or laser-clean the weld zone before welding, or expect to reduce peak power by 5–10% and accept some additional spatter until the surface is fully consumed.
What is the maximum thickness achievable with a 3KW system on carbon steel?
The validated data in this guide covers 6.0 mm at 3KW with these settings: 1.6 mm wire at 6 mm/s, 75% peak power, 20 Hz scan frequency, 5.0 mm scan width. Beyond 6 mm, penetration becomes marginal and the process requires pre-heating or multi-pass technique. For consistent single-pass welding of 6+ mm carbon steel, a higher power system or a different process (MIG, TIG, SAW) is more appropriate.
