Stainless steel is a material where the advantages of laser welding are most visible. Not because it is easy, but because its typical problems in arc welding — discoloration, distortion of thin sheets, long grinding of the face — result from excess heat, and laser introduces it sparingly and in a focused manner.
Laser welding of stainless steel has its own rules, however. Grade and wire must be selected as carefully as in TIG, gas shielding must be complete, often on both sides of the joint, and parameters fit within a narrow window. This text organizes the process step by step: from material, through preparation and gas, to post-weld treatment. One of the domestic machinery distributors indicates stainless steel as one of the most common applications of laser welding in its guide.
We present parameters qualitatively, as direction of changes, not as a table of numbers. Specific values depend on the machine, thickness and grade, and are established by testing on your own material. How laser melts metal in general and how conduction mode differs from keyhole mode, we described in the text on how laser welding works.
Why laser welding of stainless steel gives good results
Austenitic stainless steel conducts heat poorly and expands noticeably when heated. In arc welding, energy spreads widely around the weld: the sheet ripples, the face and its surroundings are covered with colored oxide deposits, and grinding and straightening remain for the entire piece.
Laser delivers heat in a narrow band. The heat-affected zone is small, the element next to the weld remains cool, so distortions are smaller, and deposits, with proper shielding, are limited to a narrow band or do not form at all. The weld is narrow and even, often requiring no grinding, which for visible surfaces is the main economic argument.
Low heat input also has a metallurgical effect. Long exposure of austenite to elevated temperatures promotes chromium carbide precipitation at grain boundaries. This is called sensitization, which leads to intergranular corrosion: the joint looks good, but after months of work in an aggressive environment it corrodes along grain boundaries.
The shorter the material is hot, the lower the risk. Laser shortens this time, which is a technological advantage, not just convenience.
1. Grade and wire: steel 304 or 316, wire 308L or 316L
The two most commonly welded grades are 304 (1.4301) and 316L (1.4404). Both are austenitic and both are welded by laser without special measures; they differ in corrosion resistance — 316 with molybdenum addition is used where the environment is more aggressive, for example with chlorides.
Wire is selected to match the grade: ER308L for steel 304, ER316L for steel 316. The letter L denotes reduced carbon content, which reduces the risk of sensitization in the weld itself. With laser, the selection principle is the same as with TIG; there is no reason to use a different composition on stainless steel just because the heat source is a beam rather than an arc.
Whether wire is needed at all depends on the joint. A butt weld on thin, well-fitted sheets is made by remelting alone. A fillet and any weld with a gap is built with wire; the feeder must have rollers matched to its diameter, because poorly fed wire gives an uneven bead and lack of fusion. Keep wire in a dry place and in original packaging — a dirty spool means pores in the weld.
2. Preparation: degreasing, gap, fit-up
Laser is more sensitive to preparation than MIG or TIG. A beam focused in a small spot will not reach through a gap that no one would notice in arc welding; instead of a weld there will be a groove or a burned edge. Fitting elements is therefore a requirement, not a recommendation. If gaps cannot be avoided, the bead is widened with wobble and wire is added.
Edges and the area around them must be clean and degreased. Oil, protective film, polishing paste or marker traces evaporate in the pool and leave pores. Stainless steel brushed with a carbon steel brush becomes contaminated with iron, which later rusts on the surface, so stainless steel brushes and tools that have not worked on carbon steel are used for cleaning.
Before a series, it is worth performing a short test on scrap from the same sheet. A batch of sheet with different surface finish (ground, brushed, film) can require different power at identical thickness, because it absorbs and reflects the beam differently.
3. Shielding gas and root protection
The most common shielding gas for stainless steel is argon. Its task is to cut off the liquid metal and the hot zone behind the pool from oxygen in the air. The gun nozzle must direct gas to the pool and to the weld just behind it.
Too low a flow rate leaves deposits; too high a flow rate draws in air through turbulence and gives the same effect. Draft in the hall can blow away the shield regardless of settings, so a workstation with a laser is placed away from gates and fans.
The other side of the joint is the root. With full penetration, the metal on the other side of the sheet is also liquid and also oxidizes if it has access to air. When the back side is to remain corrosion-resistant — tanks, pipelines, food contact elements — the root is formed with argon: gas is supplied from the back through a plug, chamber or purged channel. Without root formation it darkens and loses resistance, even if the face looks perfect.
For fillet welds without full penetration and for elements that will be etched or ground from below anyway, root formation is sometimes omitted. This is a technologist’s decision, not a default machine setting.
4. Parameters: how adjustments affect the process, rather than a settings table
Four settings make a difference: power, travel speed, wobble width and focus position; with wire, feed speed is added. They work like connected vessels — changing one requires correction of another.
Too much power at a given speed causes burn-through: the beam passes through the sheet, the face sinks, the root flows out. Too little power causes lack of penetration: nice face, under which the joint is not connected. Too slow travel gives the same effect as excess power, and additionally heats the material more widely and increases deposits; too fast gives a narrow, incoherent bead and lack of penetration.
Wider wobble distributes heat over a larger area: the face is wider and smoother, the gap is better tolerated, but penetration is shallower at the same power. Focus set on the surface or just below gives the highest power density and deepest penetration; slight defocusing smooths the face at the cost of depth.
Practical method: start with settings recommended by the manufacturer for the given thickness, perform a test, examine the face and root, then change one parameter at a time. According to materials from one laser welder seller, the window of correct parameters is narrow, and outside it cracks and porosity appear. On stainless steel this is confirmed especially with thin sheets, where there is little room between lack of penetration and burn-through.
5. Operating mode and beam oscillation (wobble) for weld appearance
For visible surfaces on stainless steel, the standard is conduction mode with wobble: a shallow, wide pool gives a smooth, even face without pronounced scaling. This is how corners of housings, countertops, fronts and everything that is to remain without grinding are welded.
Pulsed mode limits average heat input, which helps on the thinnest sheets and when welding near edges, where burn-through is easy. It gives characteristic, regular scales; some customers find them aesthetic, others do not, so it is worth establishing this before a series, not after.
Deep penetration mode (keyhole) is used where strength and full penetration of a thicker section matter, not appearance. The face is narrower and less smooth, but the weld is deep with little heating of the surroundings. In RBW 1500, the settings that determine this — continuous or pulsed mode, power, arc width (wobble) and frequency — are set from a single controller.
6. Typical defects and their causes
- Burn-through — too much power, too slow travel or stopping the gun in one place, especially at the beginning and end of the bead. On thin sheet, pulsed mode and faster, even travel help.
- Colored deposits and dark root — lack of or too weak gas shielding, draft, poorly directed nozzle, no root formation. The solution lies in the gas, not in beam parameters.
- Porosity — contaminated edge (oil, film, paste), moisture, unstable keyhole at too high power. Clean first, then adjust.
- Lack of penetration — too little power, too fast travel, too wide wobble or defocused beam. Face looks good, joint does not hold; this is checked on a sample fracture, not by eye.
- Lack of fusion and uneven bead with wire — wrong feeder rollers, wrong feed speed, wire fed outside the pool. Match rollers to diameter and correct feed angle.
- Rust spots after weeks — iron contamination (steel brush, disc after carbon steel) or omitted passivation. The fault is in the treatment, not the weld.
- Distortion despite laser — long continuous beads on thin sheet without tacking and breaks; welding in alternating sections and denser tacks help.
7. Post-weld treatment: passivation, pickling, brushes
Even a properly shielded weld has a thin layer on the surface in which the steel composition is disturbed and the natural passive layer is damaged. For the joint to be corrosion-resistant like the base material, this layer must be removed and rebuilt.
Pickling with paste or in a bath removes deposits and the chromium-depleted layer; passivation rebuilds the protective layer of chromium oxides. Both procedures are performed with agents intended for stainless steel, according to the manufacturer’s sheet and with full safety for acids. With laser, the scope of treatment is usually smaller than after TIG, because deposits are narrower, but it does not disappear — especially for food contact elements or work in a chloride environment.
Deposits are mechanically removed with stainless steel brushes, abrasive fleece or electrochemically; never with tools that have worked on carbon steel. Face grinding, if needed at all, is an exception with laser, not a rule. This saving, along with less straightening, is the main economic argument for laser in stainless steel production.
Thicknesses and machine selection for stainless steel
The thickness range is determined by source power. RBW 1500 laser welder with a Raycus 1500 W source welds stainless steel up to 5 mm, and is powered from a single-phase 230 V outlet, has liquid cooling and automatic wire feeder in the set. For comparison, one domestic laser welder manufacturer declares full penetration up to 6 mm for its 2 kW power welder.
For typical stainless steel production — housings, furniture, railings, tanks from thin sheets — the range up to 5 mm covers typical parts. Thicker sections require edge preparation and multiple passes, and for purely structural welds classical methods are often more reasonable. You will find the full offer among Roboteus laser welders; the price of RBW 1500 is a quote for the process, because the workstation configuration (gas, shields, feeder, root protection) depends on what and in what quantity you weld.
Before you decide, also read about limitations, which occur rarely on stainless steel but do not disappear — sensitivity to gaps, narrow parameter window and Class 4 laser safety — in the article on disadvantages of laser welding.
Most frequently asked questions
Can stainless steel be welded by laser without wire?
Yes, a butt weld on thin, well-fitted sheets is made by remelting alone. Wire (ER308L or ER316L) is needed for fillets, gaps and when the weld composition is to be controlled. Joint geometry decides, not the method alone.
What gas for laser welding of stainless steel?
Argon. It shields the pool and weld from oxygen, which limits oxide deposits and pores. When the back side is to retain corrosion resistance, the root is also formed with argon.
Why does a weld on stainless steel have colored deposits?
Because hot metal had contact with oxygen: shielding was too weak, nozzle poorly directed, there was draft in the hall or the root was not formed. Laser limits deposits due to low heat input, but does not eliminate them without proper shielding. Deposits are removed by pickling or mechanically, and resistance is restored by passivation.
Do you need to passivate stainless steel after laser welding?
If the joint is to be corrosion-resistant like the base material, then yes. Pickling removes deposits and the chromium-depleted layer, passivation rebuilds the protective layer. The scope of treatment after laser is usually smaller than after TIG, but for food contact elements or chloride environment the procedure is necessary.
What thickness of stainless steel does a handheld laser welder weld?
RBW 1500 with a 1500 W source welds stainless steel up to 5 mm; a 2 kW welder from one domestic manufacturer according to its declaration gives full penetration up to 6 mm. Thicker sections require beveling and multiple passes or another method.
Does laser welding of stainless steel require different safety than carbon steel?
Class 4 laser rules are the same: eyewear matched to wavelength around one micrometer, workstation shields, fume extraction. Polished stainless steel reflects the beam like a mirror, not scattered like matte carbon steel, so surrounding shields are more important. In addition, there is safety for acids during pickling and passivation.
Sources
- https://roboteus.com/pl/maszyny/spawarki-laserowe/spawarka-laserowa-rbw-1500/
- https://roboteus.com/pl/maszyny/spawarki-laserowe/
Editorial note
Manufacturer declarations and catalog prices change; check them at the source before deciding. Process parameters depend on the specific machine, grade, thickness and part preparation — the directions of changes described here do not replace testing on your own material. This text does not replace the manufacturer’s instructions, safety data sheets for pickling and passivation agents, or safety regulations for working with Class 4 lasers.