Laser Welding
Also: laser beam welding, LBW, fiber laser welding, handheld laser welding, keyhole welding, conduction laser welding, laser seam welding, remote laser welding
Laser welding fuses a joint with a focused beam: deep narrow welds, very little heat and distortion, and high speed, at the price of tight fit-up and fixturing.
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A fiber laser of 1-6 kW (up to 20 kW in industrial lines) is focused to a spot of 0.2-0.6 mm on the joint and moved along it by a CNC table, a robot or, in handheld systems, a welder with a wobble head. At low power density the beam melts a shallow, wide pool (conduction mode) for cosmetic seams and hermetic lids; at high power density it drills a vapor-filled keyhole that carries the energy deep into the joint, giving welds ten times deeper than they are wide at 1-10 m/min (40-400 in/min). Roughly, a 3 kW fiber laser penetrates 3-4 mm (1/8-5/32") of steel in one pass and 6 kW about 6-8 mm.
Because the heat goes into a narrow line and the weld is over in a fraction of a second, the heat-affected zone is small, distortion is a fraction of arc welding, hardened and heat-sensitive parts can be welded close to critical features, and thin material can be joined to thick. Most laser welds are autogenous (no filler), so the parts must touch: gaps of more than about 0.1 mm (0.004") or 10% of the thickness leave an underfilled or missed seam. Wire feed and wobble heads open that up somewhat.
Handheld fiber laser welders have made the process a job-shop tool for stainless and aluminum sheet, cabinets, kitchen and architectural work: faster and cleaner than TIG, with almost no post-finishing. The trade-offs are fit-up, fixturing, line-of-sight access to the joint, reflective materials (copper needs high power or a green laser) and the safety enclosure the beam requires.
At a glance
| Typical tolerances | Fixtured assemblies ±0.25 mm (±0.010") standard, ±0.1 mm (±0.004") with care, because distortion is so low. Seam position must be held to ±0.1 mm (±0.004") against the beam. Fit-up gap 0.1 mm (0.004") or 10% of the thickness maximum for autogenous welds; 0.3 mm with wire feed or a wobble head. Penetration depth ±10%; weld width 0.5-2 mm. |
|---|---|
| Size limits | Thickness from 0.05 mm (0.002") foil to 10-15 mm (3/8-1/2") in a single pass with high-power systems; job shops work mostly in 0.3-6 mm (0.012-0.250"). CNC and robot workstations cover about 1 m (40") envelopes; handheld systems weld any size that fits in the enclosure. The beam needs line of sight to the joint and 10-20 mm (3/8-3/4") of nozzle clearance. |
| Surface finish | A narrow, smooth seam with little reinforcement, often usable as welded with no grinding; keyhole welds may show slight undercut. Discoloration is minimal with good shielding, so stainless enclosures and food-service equipment are laser welded and lightly blended or left alone. Seams can be ground flush and polished where needed. |
| Lead time | Prototypes in 2-7 business days on handheld or CNC systems; production with dedicated fixtures in 2-4 weeks. |
Typical of U.S. job shops; confirm with the shop for your part.
Materials
Stainless 304, 316, 17-4 PH and 410 weld cleanly, and carbon and low-alloy steel (1018, 4130) as well, with medium-carbon grades hardening in the narrow heat-affected zone unless tempered. Aluminum 5052 and 5083 weld autogenously; 6061 hot-cracks without 4047 or 4043 filler wire. Titanium Grade 2 and Ti-6Al-4V, Inconel 625 and 718 and copper C110 (with high power or a green or blue laser) are laser welded in electronics, medical and aerospace work. Zinc-coated steel needs a vent gap for the zinc vapor. Free-machining grades, 7075 and 2024 are not welded.
What drives the cost
- Fixturing and the fit-up quality of the incoming parts, which must be laser cut or machined to tight tolerance
- Weld length: per inch it is cheaper than TIG once set up, because the travel speed is high
- Material: copper and aluminum need more power or filler; titanium needs shielding
- Joint access and line of sight, which may need custom nozzles or a robot
- Laser power required for the thickness
- Qualification and inspection: hermetic leak tests, metallographic sections, penetration checks
- Volume, which pays for automation and fixtures
When to use it
- Thin stainless and aluminum sheet assemblies that must stay flat and look finished
- Hermetic lids, sensor housings, battery tabs, medical devices and electronics packages
- Welds next to hardened, ground or heat-sensitive features
- Thin-to-thick joints and dissimilar thicknesses
- High-volume automated seams where the parts fit consistently
When not to
- Poor fit-up, flame-cut or hot-rolled edges, or gaps over 0.1 mm without filler
- Thick plate groove welds that need filler to bridge
- Field welding, or joints without line-of-sight access
- Copper without a high-power or green laser
- One-off mild steel weldments where MIG is cheaper and good enough
Design tips
- Design butt joints with laser-cut or machined edges that touch: 0.1 mm (0.004") gap or less; lap and edge joints tolerate more.
- Prefer edge, flange and lap joints in sheet, which self-locate and forgive gap better than square butts.
- Leave line of sight and 10-20 mm (3/8-3/4") of nozzle clearance to every seam.
- Avoid 6061 autogenous welds: use 5052, or specify 4047 filler wire.
- Leave a 0.1 mm vent gap or strip the zinc at the joint on galvanized steel.
- Specify the weld by penetration depth and width rather than as a fillet, and say whether it must be hermetic and to what leak rate.
- Add self-fixturing features (tabs, steps, press fits) so the parts hold their own fit-up.
- Keep features that cannot tolerate a 0.5 mm heat-affected zone at least 1-2 mm from the seam.
Laser Welding by material
Frequently asked questions
- Laser welding vs TIG welding?
- Laser is faster, puts far less heat into the part and leaves a narrower, cleaner seam, but it needs tight fit-up, fixturing and line of sight. TIG tolerates gaps, adds filler freely and works anywhere, at a slower pace with more distortion. On stainless and aluminum sheet with good fit-up, laser wins; on hand-fit assemblies and tube, TIG.
- How thick can laser welding weld?
- Roughly 1 mm per kilowatt in steel: a 3 kW handheld or CNC system reaches 3-4 mm (1/8-5/32") in one pass, 6 kW about 6-8 mm, and 15-20 kW industrial systems 12-15 mm (1/2-5/8"). Most job-shop laser welding is in 0.3-6 mm material.
- Can aluminum be laser welded?
- Yes. 5052 and 5083 weld well without filler; 6061 and 6063 crack unless 4047 or 4043 wire is fed; 7075 and 2024 are not welded. Aluminum needs somewhat more power than steel and clean, oxide-free edges, and porosity control matters on thicker sections.
- Is handheld laser welding as strong as TIG?
- A sound laser weld with full penetration is as strong as the base metal, the same as TIG. The risk is a shallow weld that looks finished but has not penetrated, because the bead is narrow and there is no filler to judge by; specify the penetration depth and check it with a section or a test coupon.
- Does laser welding warp parts?
- Much less than arc welding: the heat goes into a narrow line for a fraction of a second, so the heat-affected zone is a few tenths of a millimeter and thin panels stay flat. Long seams still shrink a little along their length; fixturing and a balanced sequence handle it.
