Table of Contents
- 1. Why Aluminum Is Harder to Weld Than Steel
- 2. Focus Position: The +3 to +5 mm Rule
- 3. Minimum Power: Why 1KW Is Not Enough
- 4. Complete Parameter Tables
- 5. Three Aluminum-Specific Rules
- 6. Wire Selection: ER4043 vs ER5356
- 7. Surface Preparation: The Step You Cannot Skip
- 8. Troubleshooting Aluminum Welds
- FAQ
If you are running a 1200W M-Series system on 1–2 mm aluminum, the Industrial Aluminum Laser Welding Guide covers your range. This guide picks up from there: 2KW and 3KW systems, plate up to 4.0 mm, and the deeper process knowledge — wire alloy selection, surface preparation, and defect diagnosis — that higher-power production jobs require.
The 1.5KW reference table is included for continuity, but the primary scope here is operators who have stepped up in power and need validated parameters for the thicker aluminum range that 800W/1200W systems cannot reach.
Why Aluminum Is Harder to Weld Than Steel
Three material properties make aluminum fundamentally more challenging to laser weld than carbon steel or stainless steel. Understanding them shapes every parameter decision in this guide.
High reflectivity
Polished aluminum reflects over 90% of near-infrared laser energy at room temperature. Until the surface begins to melt and absorptivity increases, very little energy actually enters the material. This makes melt pool initiation unstable and risks sudden reflection events that can damage the laser head — which is why focus position is set above the surface, not on it.
Tenacious oxide layer
Aluminum forms Al₂O₃ immediately on any exposed surface. This oxide melts at 2,072°C — more than three times the melting point of the aluminum beneath it (660°C). If the oxide layer is not removed before welding, the laser melts the base metal while the oxide film remains intact, producing cold-lap defects and the porosity that makes aluminum welds fail inspection.
High thermal conductivity
Aluminum conducts heat away from the weld zone roughly four times faster than stainless steel. Combined with low melting point, this creates a narrow window between "not melted" and "burned through" — especially at 1.5KW, which is why 2KW is the recommended baseline for regular production. It also explains why scan width jumps to 4.0 mm at 2 mm thickness and stays there, rather than gradually increasing as it does for steel.
Focus Position: The +3 to +5 mm Rule
This is the single most important difference between aluminum and steel laser welding parameters. Every other setting assumes this one is correct.
position
Why defocusing works for aluminum
Setting the focus 3–5 mm above the surface increases the beam spot diameter at the workpiece. The same total laser power is now spread over a larger area, which does two things simultaneously: it lowers the peak energy density enough to prevent the sudden high-reflectivity bounce that can damage optics, and it creates a broader initial heating zone that brings more surface area to melting temperature at once. Once the surface begins to melt, aluminum's absorptivity rises sharply from below 10% toward 70%+, and the weld pool self-sustains normally.
Choosing between +3 mm and +5 mm
Start at +3 mm for thicknesses of 1.0–2.0 mm. Move to +5 mm for 2.5 mm and above, or if the surface is mirror-polished rather than mill-finish. The wider defocus on thick plate also helps distribute energy across the larger melt pool needed for full penetration. Fine-tune in 0.5 mm steps — small adjustments at this level have a measurable effect on bead width and spatter level.
Minimum Power: Why 1KW Is Not Enough
There is no validated parameter set for 1KW aluminum laser welding in GWEIKE M-Series testing records — not a single data point across any thickness. This is not a gap in the data; it is the result of systematic testing showing that 1KW cannot reliably establish a stable aluminum weld pool even at 1.0 mm. The combination of high reflectivity and high thermal conductivity means that at 1KW, by the time enough energy has entered the material to form a melt pool, the surrounding area has already conducted the heat away and the pool collapses.
1.5 KW
Covers 1.0–2.0 mm. Same data as the 800W/1200W guide. Included here for continuity — if this is your power level, use that guide as your primary resource.
2 KW
Covers 1.0–3.0 mm with comfortable parameter margins at every thickness. The baseline power level for reliable aluminum production welding on plate up to 3 mm.
3 KW
Covers 1.0–4.0 mm. The only level in this guide with data for 3.5–4.0 mm plate. Generous operating window at all thicknesses.
Complete Parameter Tables
All values are from validated tests on GWEIKE M-Series fiber welding systems. The 2KW and 3KW tables are the primary content of this guide. The 1.5KW table is included for reference and overlap with the existing 800W/1200W guide — if 1.5KW is your system, cross-check with the Industrial Aluminum Laser Welding Guide as your primary source. Use these as starting points and adjust ±5% based on your alloy, joint geometry, and surface condition. PWM duty cycle is 100% and PWM frequency is 1000 Hz throughout.
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 1.0 | 1.0 | 15 | 50% | 100 | 2.5 |
| 1.2 | 1.0 – 1.2 | 13 | 55% | 80 | 2.5 |
| 1.5 | 1.2 | 12 | 70% | 40 | 3.0 |
| 2.0 | 1.6 | 10 | 85% | 40 | 4.0 |
These values match the 1200W data in the Industrial Aluminum Laser Welding Guide — the same underlying test data. If 1.5KW is your production system, that guide is your primary reference. The 2KW table below is where this guide's primary scope begins.
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 1.0 | 1.0 | 15 | 36% | 50 | 2.0 |
| 1.2 | 1.0 – 1.2 | 13 | 36% | 50 | 2.0 |
| 1.5 | 1.2 | 12 | 40% | 50 | 3.0 |
| 2.0 | 1.6 | 12 | 45% | 50 | 4.0 |
| 2.5 | 1.6 | 12 | 55% | 40 | 4.0 |
| 3.0 | 1.6 | 10 | 65% | 40 | 4.0 |
2KW provides comfortable operating margins across the full 1.0–3.0 mm range. This is the recommended baseline for production aluminum welding.
| Thickness (mm) | Wire dia. (mm) | Wire speed (mm/s) | Peak power (%) | Scan freq. (Hz) | Scan width (mm) |
|---|---|---|---|---|---|
| 1.0 | 1.0 | 15 | 25% | 50 | 2.0 |
| 1.2 | 1.0 – 1.2 | 13 | 25% | 50 | 2.0 |
| 1.5 | 1.2 | 12 | 27% | 50 | 3.0 |
| 2.0 | 1.6 | 12 | 30% | 50 | 4.0 |
| 2.5 | 1.6 | 12 | 37% | 40 | 4.0 |
| 3.0 | 1.6 | 10 | 45% | 40 | 4.0 |
| 3.5 | 1.6 | 10 | 55% | 30 | 4.0 |
| 4.0 | 1.6 | 10 | 65% | 25 | 4.0 |
3KW is the only power level with data for 3.5–4.0 mm aluminum. At these thicknesses scan frequency drops to 25–30 Hz — similar to thick carbon steel, but for a different reason: slow oscillation is needed to keep energy dwell time long enough to push through aluminum's high thermal conductivity.
Three Aluminum-Specific Parameter Rules
Compared to carbon steel, aluminum's parameter behavior looks different in three systematic ways. These are not quirks — they each follow directly from the material properties covered in Section 1.
Rule 1 — Wire diameter steps to 1.6 mm earlier than steel
Carbon steel and stainless steel don't require 1.6 mm wire until 3.0 mm plate thickness. Aluminum makes the step at 2.0 mm — a full millimeter earlier. The reason is aluminum's faster heat conduction: the melt pool volume grows more rapidly with thickness in aluminum than in steel, requiring a larger-diameter wire to fill it adequately and maintain a consistent bead profile.
1.0 – 1.2 mm sheet
- Wire diameter: 1.0 mm
- Wire speed: 13 – 15 mm/s
- Either 1.0 or 1.2 mm wire works at 1.2 mm thickness — let joint gap guide the choice.
1.5 mm sheet
- Wire diameter: 1.2 mm
- Wire speed: 12 mm/s
- Transition thickness between thin and mid-range. 1.2 mm wire is the right step here for all three power levels.
≥ 2.0 mm sheet
- Wire diameter: 1.6 mm
- Wire speed: 10 – 12 mm/s
- Stays at 1.6 mm all the way to 4.0 mm. No further wire step for aluminum in this range.
Steel comparison
- CS/SS stay at 1.2 mm wire through 2.5 mm plate.
- CS/SS don't reach 1.6 mm until 3.0 mm.
- Do not use steel wire diameter tables for aluminum — they will underfill the joint.
Rule 2 — Scan frequency is lower across the board, with no high-frequency thin-sheet phase
Carbon steel and stainless steel use 100–150 Hz for thin sheet (≤ 2 mm) and drop to 30 Hz for thick plate — a clear threshold. Aluminum never uses 100 Hz or above except at 1.5KW on 1.0 mm sheet. The 2KW and 3KW tables show 50 Hz from the very first data point, dropping to 40 Hz at 2.5–3.0 mm and to 25–30 Hz for 3.5–4.0 mm. The steel logic of "fast oscillation to prevent burn-through on thin sheet" does not apply the same way to aluminum because the material's high thermal conductivity already limits overheating — the greater risk is insufficient energy dwell time, not excess.
| Thickness | Aluminum — scan freq. | Carbon steel — scan freq. | Difference |
|---|---|---|---|
| 1.0 mm | 50 Hz (2KW/3KW) | 100 Hz | Al uses half the freq. on thin sheet |
| 1.5 mm | 50 Hz | 50–100 Hz | Converge at this thickness |
| 2.0 mm | 50 Hz | 30 Hz | Al stays higher at the CS threshold |
| 3.0 mm | 40 Hz | 30 Hz | Closer but Al still higher |
| 4.0 mm | 25 Hz (3KW only) | 30 Hz | Converge at thick plate |
Rule 3 — Scan width locks at 4.0 mm from 2.0 mm thickness onward
Carbon steel and stainless scan width increases gradually from 3.0 mm through 4.5 mm as thickness grows. Aluminum jumps directly to 4.0 mm at 2.0 mm plate thickness and stays at 4.0 mm all the way to 4.0 mm plate. This flat scan width behavior reflects the balance point between needing a wide beam to distribute energy across aluminum's fast-conducting heat zone, and avoiding excessive width that would spread energy too thin to achieve penetration. For aluminum, that balance is always 4.0 mm in the 2–4 mm range.
Wire Selection: ER4043 vs ER5356
Aluminum laser welding uses a completely different wire alloy family from steel. Do not use ER70S-6 or any steel filler wire on aluminum — the metallurgy is incompatible and the weld will fail. The two standard aluminum filler wires for laser welding are ER4043 and ER5356, and the choice between them depends on the base alloy and the finish requirements of the part.
ER4043
- ✓ Excellent resistance to hot cracking — the primary failure mode in aluminum welding
- ✓ Good fluidity — flows into joint gaps without bridging
- ✓ Works well on 6061, 6063, and most 6xxx-series alloys
- ✓ Lower sensitivity to porosity from surface contamination
- ✗ After anodizing, weld bead appears darker than base material
- ✗ Lower tensile strength than ER5356
ER5356
- ✓ Higher tensile strength than ER4043 — better for structural joints
- ✓ Color match after anodizing is closer to 5xxx and 6xxx base alloys
- ✓ Better suited for welding 5xxx-series alloys (5052, 5083)
- ✗ More prone to hot cracking than ER4043
- ✗ Higher sensitivity to contamination — surface prep is more critical
- ✗ Not recommended for elevated-temperature service (sensitisation risk)
Surface Preparation: The Step You Cannot Skip
Aluminum is uniquely sensitive to surface contamination before laser welding. Carbon steel can tolerate moderate surface oil or mill scale — the laser burns through it and the weld proceeds. Aluminum cannot. The oxide layer on aluminum melts at 2,072°C while the aluminum beneath melts at 660°C. Any oil or moisture on the surface releases hydrogen into the molten pool. The result in both cases is porosity — and unlike steel, aluminum porosity is not self-healing. A porous aluminum weld cannot be saved by adjusting parameters. The contamination must be removed before the arc starts.
Pre-weld surface preparation sequence
Troubleshooting Aluminum Welds
Aluminum welding has a distinct set of failure modes compared to steel. The three problems below account for the majority of defects on aluminum laser welds and each has a specific diagnosis pathway.
🔵 Porosity (small round voids inside the weld)
Cause: Hydrogen trapped during solidification. Aluminum in liquid state dissolves up to 20× more hydrogen than solid aluminum — when the pool solidifies rapidly, dissolved hydrogen cannot escape and forms gas pores. Sources: surface oil/moisture on the workpiece, moisture in the wire, atmospheric humidity entering the gas shield, or oxide layer not fully removed.
Diagnosis order: (1) Was the surface cleaned with acetone and wire-brushed within 30 minutes? If not, clean and retry before adjusting any parameter. (2) Is the filler wire dry? Open a fresh sealed spool if the current one has been exposed for more than a day. (3) Verify N₂ flow is ≥ 20 L/min with no leaks at the nozzle fitting. (4) If porosity persists after the above: reduce welding speed by 10% to allow more time for gas to escape the pool before solidification. Do not increase peak power — this makes porosity worse by increasing pool turbulence.
🔴 Hot cracking (longitudinal crack along the weld centreline)
Cause: Aluminium alloys with wide solidification temperature ranges (particularly 6xxx series) are susceptible to hot cracking when the partially-solidified weld is still under thermal contraction stress. Using ER5356 wire increases this risk. Insufficient filler wire volume also increases crack susceptibility by reducing the ductile Si content in the solidifying bead.
Fix: Switch to ER4043 wire — its higher silicon content lowers the solidification temperature range and reduces hot cracking tendency significantly. Increase wire feed speed by 10% to ensure adequate filler volume. If cracking persists with ER4043, check that the joint has no high restraint (clamping arrangement that prevents normal thermal contraction) and that fit-up gap is not larger than 0.3 mm.
⚡ Erratic melt pool / spatter at weld start
Cause: Almost always focus position error. When focus is set at 0 mm on aluminum (steel setting), the initial high-reflectivity surface scatters energy unpredictably before the surface melts. This produces spatter bursts in the first 5–15 mm of each weld run, after which the now-molten surface absorbs more efficiently and the weld settles.
Fix: Set focus to +3 mm and re-test. If the problem persists but is reduced, increment to +4 mm, then +5 mm. Also inspect the workpiece surface: a heavily oxidised or anodised surface has even higher initial reflectivity and may require +5 mm focus even for thin sheet. For anodized aluminum, the anodising must be removed from the weld zone before laser welding — it does not burn away cleanly and will cause persistent spatter throughout the weld, not just at the start.
📉 Incomplete penetration on plate ≥ 2.5 mm
Cause: Scan frequency too high (carried over from 2 mm settings), peak power insufficient for the actual alloy or surface condition, or wire diameter still at 1.2 mm instead of the required 1.6 mm for this thickness range.
Fix: Confirm wire is 1.6 mm for any thickness ≥ 2.0 mm. Drop scan frequency to 40 Hz for 2.5–3.0 mm, or 25–30 Hz for 3.5–4.0 mm. Increase peak power in 3% steps and cut a cross-section test piece to verify fusion depth. Ensure surface was cleaned — oxide layer residue creates a barrier to full penetration even when energy levels appear sufficient.
Verify parameters on your specific alloy and thickness
The 2KW and 3KW parameter tables in this guide come from GWEIKE M-Series validation runs on standard alloys under controlled surface conditions. If your production material, alloy spec, or joint design differs — particularly on 3.5–4.0 mm plate where the operating window is narrower — a test run before committing to production is the most reliable validation step. Our applications team can arrange this on M-Series equipment.
FAQ
Why is the focus position different for aluminum laser welding?
Aluminum reflects over 90% of near-infrared laser energy at room temperature. Focusing directly on the surface risks a sudden reflective event that can damage the laser head optics. Setting focus +3 to +5 mm above the surface increases the beam spot size at the workpiece, reduces peak energy density, and allows the melt pool to form more gradually — stabilising coupling and protecting the optics. Once the surface begins to melt, aluminum's absorptivity rises sharply and the weld pool self-sustains normally.
Can a 1KW fiber laser weld aluminum?
No. There is no validated parameter set for 1KW aluminum laser welding in GWEIKE M-Series testing. Aluminum's combination of high reflectivity and high thermal conductivity means a 1KW system cannot reliably establish or maintain a stable melt pool. The minimum practical power is 1.5KW; 2KW is recommended for regular production.
What wire should I use for aluminum laser welding?
ER4043 (Al-Si alloy) is the standard choice for most applications. It has excellent crack resistance and works well on 6061, 6063, and most 6xxx-series alloys. ER5356 (Al-Mg alloy) gives higher joint strength and better color match after anodizing, but is more prone to hot cracking. Do not use ER70S-6 or any steel wire — these are metallurgically incompatible with aluminum.
What causes porosity in aluminum laser welds?
Porosity is caused by hydrogen trapped during solidification. Aluminum in liquid state absorbs up to 20 times more hydrogen than solid aluminum. When the weld pool solidifies, hydrogen cannot escape fast enough and forms pores. The most common sources are surface oil or moisture, moisture absorbed by the filler wire, and the Al₂O₃ oxide layer not being fully removed before welding. Surface cleaning with acetone and a stainless steel wire brush immediately before welding eliminates most porosity issues. Adjust parameters only after confirming the surface preparation is correct.
Do I need to remove the oxide layer before every weld?
Yes. The Al₂O₃ layer that forms on aluminum surfaces has a melting point of 2,072°C — more than three times the melting point of the aluminum beneath it. If it is not removed, it creates an inclusion in the weld zone. Even on freshly machined or extruded aluminum, the oxide layer re-forms within minutes of exposure to air. Wire-brush the weld zone with a dedicated stainless steel brush and wipe with acetone within 30 minutes before each weld run.
Why does aluminum need higher power than stainless steel at the same thickness?
Aluminum conducts heat away from the weld zone approximately four times faster than stainless steel. This high thermal conductivity means energy dissipates rapidly, requiring higher power delivery to maintain the melt pool. At 1.0 mm on a 1.5KW system, aluminum requires 50% peak power while stainless requires 38% — about 32% more. The gap narrows at higher power levels and greater thickness, but aluminum consistently requires more energy delivery than stainless at comparable conditions.
Can I weld 6061 aluminum with a laser?
Yes. 6061 is one of the most commonly laser-welded aluminum alloys. Use ER4043 filler wire — 6061's alloy composition makes it susceptible to hot cracking, and ER4043's higher silicon content significantly reduces this risk. Thorough surface preparation is essential. The parameters in this guide were validated on standard 6xxx-series alloys and apply directly to 6061 production welding. If parts will be anodized after welding and appearance matters, test with both ER4043 and ER5356 on a sample piece first — the bead appearance after anodizing differs meaningfully between the two.
