Frequently Asked Questions
Expert answers to common laser welding questions plus 10 real-world case studies with detailed before/after analysis.
Real-World Case Studies
Actual problem-solving scenarios from production environments with detailed before/after analysis.
Battery Tab Welding - Porosity Issue Resolved
Problem
Severe porosity (>30% area) in battery tab to busbar welds causing 15% failure rate in electrical testing.
❌ Before (Initial Parameters)
Power: 3.5kW, Speed: 80mm/s, Shielding: Argon 15L/min
- Visible pores on surface
- Internal voids via X-ray
- High resistance (>0.5mΩ)
Solution Steps
- Implemented ultrasonic cleaning + acetone wipe
- Reduced speed to 50mm/s for stable keyhole
- Increased gas flow to 25L/min with wider nozzle
- Added 1mm focus offset for better gas coverage
After (Optimized Parameters)
Power: 3.5kW, Speed: 50mm/s, Shielding: Argon 25L/min, Focus: +1mm
- Porosity <2%
- Resistance 0.15-0.20mΩ
- Failure rate <0.5%
Business Impact: Reduced scrap by 14%, saved $180k annually
Stainless Steel 304 - Cracking in T-joints
Problem
Longitudinal cracks in 40% of T-joint welds during assembly. Cracks propagate under thermal cycling.
❌ Before (Initial Parameters)
Power: 2.8kW, Speed: 60mm/s, No preheat
- Cracks within 5mm of weld center
- High residual stress measured
- Failed bend testing
Solution Steps
- Reduced power to 2.2kW (lower thermal gradient)
- Decreased speed to 40mm/s (more heat time)
- Changed weld sequence: tack-weld, then continuous
- Added fixture with lower restraint
After (Optimized Parameters)
Power: 2.2kW, Speed: 40mm/s, Modified fixturing
- Zero cracks in 500+ parts
- Passed bend test 180°
- Residual stress reduced 60%
Business Impact: Achieved 100% quality target, eliminated rework
Aluminum 6061 - Insufficient Penetration
Problem
Only 2.5mm penetration in butt joints (target: full penetration). Joints failing tensile test at 80% of specification.
❌ Before (Initial Parameters)
Power: 3.0kW, Speed: 70mm/s, Focus: surface
- Shallow penetration
- Wide bead (6mm)
- Low tensile strength (180 MPa)
Solution Steps
- Increased power to 4.5kW (aluminum needs high power)
- Reduced speed to 45mm/s
- Defocused -1.5mm (concentrated energy deeper)
- Wire brushed immediately before welding
After (Optimized Parameters)
Power: 4.5kW, Speed: 45mm/s, Focus: -1.5mm
- Full penetration 4.2mm
- Narrower bead (4mm)
- Tensile strength 220 MPa (meets spec)
Business Impact: Parts passed qualification, production approved
Titanium Grade 2 - Discoloration & Embrittlement
Problem
Golden/blue discoloration on weld and HAZ. Hardness increased from 200HV to 450HV. Failed impact testing.
❌ Before (Initial Parameters)
Shielding: Argon 18L/min (top only)
- Visible oxidation colors
- Brittle HAZ
- Hardness >400HV
Solution Steps
- Added trailing shield (20L/min Argon, 50mm trailing)
- Implemented back purging (8L/min)
- Increased top gas to 25L/min
- Extended shielding 3 seconds post-weld
After (Optimized Parameters)
Top: 25L/min, Trailing: 20L/min, Back: 8L/min
- Silver/grey surface (no oxidation)
- Hardness 220-250HV
- Passed impact test
Business Impact: Met aerospace spec AS9100, zero rejections
Copper Busbar - Low Penetration & Reflectivity
Problem
Only 0.8mm penetration with 5kW laser. Welds failing shear test. 90%+ laser energy reflected.
❌ Before (Initial Parameters)
Laser: 1064nm Fiber, Power: 5kW, Speed: 30mm/s
- Minimal penetration
- Energy efficiency <10%
- Weak joints
Solution Steps
- Upgraded to 515nm (green) laser - better copper absorption
- Added preheating to 250°C (reduces reflectivity)
- Reduced speed to 20mm/s
- Applied surface roughening (sandblasting)
After (Optimized Parameters)
Laser: 515nm, Power: 3kW, Preheat: 250°C, Speed: 20mm/s
- Penetration 2.8mm
- Absorption efficiency 45%
- Shear strength 85% of base metal
Business Impact: Switched laser wavelength, reduced power needed by 40%
Dissimilar Weld - Steel to Aluminum Failure
Problem
Brittle intermetallic layer causing immediate fracture at weld interface. 100% failure rate.
❌ Before (Initial Parameters)
Power: 2.5kW, Direct fusion (no filler)
- Thick intermetallic >100μm
- Instant brittle fracture
- Zero ductility
Solution Steps
- Offset beam 0.8mm toward aluminum side
- Reduced power to 1.8kW (minimize mixing)
- Increased speed to 80mm/s (limit diffusion time)
- Considered transition layer (future: Ni interlayer)
After (Optimized Parameters)
Power: 1.8kW, Speed: 80mm/s, Beam offset: 0.8mm Al-side
- Intermetallic <20μm
- Tensile strength 120 MPa
- Limited ductility achieved
Business Impact: Functional joint achieved (80% now pass), considering design change
High-Speed Seam Welding - Spatter Control
Problem
Excessive spatter at production speed (150mm/s) contaminating product. Cleaning required on 60% of parts.
❌ Before (Initial Parameters)
Power: 1.8kW, Speed: 150mm/s, Focus: surface
- Heavy spatter deposits
- Irregular bead
- Post-weld cleaning needed
Solution Steps
- Defocused +1.5mm (broader beam, lower intensity)
- Reduced power to 1.5kW
- Tilted nozzle 15° forward (gas clears spatter)
- Added side gas knife
After (Optimized Parameters)
Power: 1.5kW, Speed: 150mm/s, Focus: +1.5mm, Side gas
- Spatter reduced 90%
- Clean parts 95%+
- Eliminated cleaning step
Business Impact: Saved 2 hours/shift labor, $85k annually
Thick Section Steel - Incomplete Fusion
Problem
Incomplete root fusion in single-pass butt weld. Ultrasonic testing showing 30-40% lack of fusion.
❌ Before (Initial Parameters)
Power: 4kW, Speed: 25mm/s, Single pass
- Penetration only 6mm
- Root gap unfused
- Failed UT inspection
Solution Steps
- Increased power to 6kW
- Reduced speed to 18mm/s (more energy per length)
- Defocused -2mm (concentrate energy at depth)
- Beveled joint (30° included angle) for accessibility
After (Optimized Parameters)
Power: 6kW, Speed: 18mm/s, Focus: -2mm, Joint prep: 30° bevel
- Full penetration 8.5mm
- Root fusion confirmed via UT
- 100% acceptance
Business Impact: Single-pass welding maintained, 30% faster than TIG alternative
Galvanized Steel - Zinc Contamination
Problem
Severe porosity from zinc vaporization. Zinc fumes causing health concerns.
❌ Before (Initial Parameters)
Power: 3kW, Speed: 60mm/s, Lap joint
- Porosity >20%
- Zinc splatter
- Fume exposure high
Solution Steps
- Created 0.3mm gap for zinc vapor escape
- Dual-pass strategy: 1st pass low power (evaporate Zn), 2nd pass full fusion
- Enhanced fume extraction (capture velocity 1.2m/s)
- Added aluminum-killed filler wire (future)
After (Optimized Parameters)
1st pass: 1.5kW, 2nd pass: 3kW, Gap: 0.3mm
- Porosity <3%
- Fume exposure within OSHA limits
- Corrosion protection maintained
Business Impact: Production quality acceptable, fume control compliant
Precision Welding - Distortion in Thin Sheets
Problem
Severe warping (>2mm) in 150mm x 200mm panels. Parts out of flatness tolerance.
❌ Before (Initial Parameters)
Power: 1.2kW, Speed: 80mm/s, Continuous weld
- Panel warping 2-3mm
- Residual stress pattern
- 40% scrap rate
Solution Steps
- Reduced power to 0.8kW (minimize heat input)
- Increased speed to 120mm/s
- Skip-welding pattern: 20mm weld, 20mm skip, backfill
- Clamped with heat-sink backing plate
After (Optimized Parameters)
Power: 0.8kW, Speed: 120mm/s, Skip-weld + clamping
- Distortion <0.2mm
- Flatness within spec
- Scrap <2%
Business Impact: Reduced scrap 95%, parts meet tight tolerance
General Q&A
Common questions organized by topic area.
Process Basics
What is the difference between keyhole and conduction mode welding?
Keyhole mode occurs at high power densities where a vapor cavity forms, allowing deep penetration with narrow beads. Conduction mode operates at lower power densities, producing wide, shallow welds through surface heat conduction.
How do I determine the right laser power for my application?
Power requirements depend on material type, thickness, and desired welding speed. Rule of thumb: 1 kW per 1-1.5mm thickness for steel, 1.5-2× more for aluminum. Use our Energy & Heat Calculator for precise recommendations.
What shielding gas should I use?
Argon (99.999% purity) is standard for most metals including stainless steel, aluminum, and titanium. Carbon steel can use Argon or Ar+2% CO₂. For titanium, use additional trailing shield. Gas flow rate typically 15-25 L/min.
Troubleshooting
Why is my weld full of porosity?
Common causes: (1) Contaminated surface - clean thoroughly; (2) Insufficient shielding gas - check flow rate; (3) Too high speed - reduce; (4) Moisture in material - preheat; (5) Air entrainment - improve gas coverage.
How do I fix spatter and excessive metal ejection?
Spatter indicates unstable keyhole or excessive power. Solutions: (1) Reduce power by 10-15%; (2) Increase speed slightly; (3) Defocus beam by +0.5mm; (4) Increase shielding gas flow; (5) Clean material surface.
What causes weld cracking?
Cracking results from thermal stress and material composition. Prevention: (1) Preheat high-carbon steels to 200-300°C; (2) Reduce restraint in fixtures; (3) Optimize weld sequence; (4) Control cooling rate. Use our Crack Risk Calculator.
Materials
Can I weld aluminum without preheating?
Yes, aluminum typically does not require preheating. However, preheating to 100-150°C can help remove moisture, improve penetration in thick sections, and reduce thermal shock. Focus on surface cleanliness.
Why is copper so difficult to weld with lasers?
Copper has very high reflectivity (~95%) at 1064nm and extremely high thermal conductivity. Solutions: (1) Use 3-4× higher power; (2) Blue/green lasers have better absorption; (3) Preheat to 200-300°C; (4) Use slower speeds.
What are the special requirements for welding titanium?
Titanium is highly reactive with oxygen. Requirements: (1) High-purity argon shielding (99.999%+); (2) Trailing shield; (3) Back purging for full-penetration welds; (4) Thorough surface cleaning.
Safety
What laser safety class are welding lasers?
Class 4 - the highest hazard class. They can cause immediate skin and eye damage. Requirements: (1) Fully enclosed workspace with interlocks; (2) OD 5+ laser safety glasses; (3) Trained operators only; (4) Laser Safety Officer.
What fume extraction is needed?
Local exhaust ventilation (LEV) is mandatory. Requirements: (1) Capture velocity 0.5-1.0 m/s at source; (2) HEPA filters for particulate; (3) Activated carbon for gases; (4) Air monitoring for metal-specific OELs.
How do I calculate safe viewing distance?
Use NOHD (Nominal Ocular Hazard Distance) calculation per ISO 11553. For a 3kW fiber laser, NOHD is approximately 5-8 meters. Our Protection Distance Calculator provides precise values.
Equipment
Fiber laser vs CO₂ laser - which is better?
Fiber lasers dominate modern welding: (1) Higher efficiency (30% vs 10%); (2) Better beam quality; (3) Lower maintenance; (4) Smaller footprint; (5) Better metal absorption. For metal welding, choose fiber.
What beam quality (M²) do I need?
Lower M² means better focusability. Requirements: (1) M² < 4: Excellent for deep keyhole welding; (2) M² 4-8: Good for general welding; (3) M² > 8: Conduction mode only. Modern fiber lasers achieve M² < 2.
How much maintenance does a fiber laser require?
Very low maintenance: (1) No consumable parts in laser head; (2) Check protective window weekly; (3) Replace window every 3-6 months; (4) Annual calibration check; (5) Keep cooling water clean. Typical uptime >95%.
Can't Find Your Answer?
If your question isn't answered here, try these resources:
- Browse our Knowledge Base for detailed technical articles
- Check the Glossary for term definitions
- Use our Calculators for specific parameter guidance
- Review Quick Reference Tables for material properties
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