Several Tips for Laser Welding

Laser welding is a branch of laser-based metalworking technology, widely applied across numerous industrial sectors including automotive, precision equipment, electrical appliances, aerospace and medical devices. Among its many applications, this article focuses on laser welding for sheet-metal processing and introduces its fundamentals.

What is Laser Welding? (Key Characteristics)

The term “laser” is an acronym derived from Light Amplification by Stimulated Emission of Radiation.

Though its definition may seem complex at first glance, you may simply understand a laser as “man-made light”. Compared with ordinary light such as sunlight and indoor lighting we encounter daily, laser light features constant wavelength, phase and direction. Collectively known as coherence, these three properties are adjusted and deployed to enable diverse material-processing applications.

Laser welding is a processing technique that focuses man-made laser light onto a target workpiece to locally melt and solidify metal for joining purposes. When adopted for sheet-metal fabrication, laser welding offers advantages over conventional arc welding: better control over thermal distortion, easier management of welding parameters, and less visible weld beads.

Principle of Laser Welding

In laser welding, a laser oscillator generates laser energy that serves as the heat source. The laser beam is amplified and transmitted via optical fiber to the vicinity of the workpiece. A laser processing head is required at this stage. Lenses fitted inside the laser processing head focus the incoming laser beam into a state suitable for welding. Lens focusing concentrates laser energy over a tiny spot, delivering sufficient power density to melt metal. Shielding gases such as argon or nitrogen are typically blown onto the weld zone during welding to prevent oxidation of molten metal.

Types of Laser Welding

Below are hand-held laser-welding variants suitable for sheet-metal work. Portable laser welding machines with YAG lasers first gained popularity in Japan starting in the 1990s. For a long time thereafter, the Japanese sheet-metal industry regarded “laser-welding machine” as synonymous with “YAG laser”. Following the commercial launch of fiber-laser welding systems in the mid-2010s, fiber lasers have become the mainstream for portable hand-held laser welding. Disk-laser-based portable welding equipment is another available option.

Hand-Held Welding with Fiber Laser Welding Machines

· YAG Laser Welding

YAG stands for Yttrium Aluminum Garnet, a type of crystal. A YAG laser generates laser output by irradiating high-intensity light onto the YAG crystal. With a wavelength of 1064 nm that metals readily absorb, YAG lasers can melt metal with relatively low input energy, which makes them well-suited for welding.

On the downside, flashlamps are required to produce laser emission. Substantial heat generation demands chillers for cooling from the oscillator all the way to the welding torch, leading to high power consumption. Only a portion of the input electricity is converted into usable processing energy, and incomplete penetration may occur. High maintenance costs for consumables such as cooling water components and flashlamps constitute another major practical drawback.

· Fiber Laser Welding

A fiber laser amplifies and delivers pump light through optical fiber, emitting at 1070 nm, a wavelength readily absorbed by metals. Among various laser sources, fiber lasers deliver exceptionally high energy density and superior beam focusing capability, enabling deep penetration welding of metals — a core advantage.

Compared with YAG lasers, fiber lasers offer deep penetration, low operating costs, and minimal adjustment and maintenance workload. They have seen rapid adoption in recent years. Despite high power and efficiency, hand-held sheet-metal welding systems normally cap output at approximately 1 kW for operator safety. For higher power and deeper penetration, mechanized or robot-based welding should be considered.

· Disk Laser Welding

A disk laser amplifies pump light using disc-shaped YAG crystals, then transmits the beam via optical fiber. A German manufacturer achieved high-power stable operation, which popularized disk lasers for industrial use. Their application potential is being revisited and new use cases are under active development.

Stand-alone hand-held disk-laser welding units are unavailable in Japan. Nevertheless, users owning disk-laser cutting machines from this manufacturer may optionally add a hand-held welding torch.

Advantages and Disadvantages of Laser Welding

Listed below are characteristics of laser welding for sheet-metal fabrication versus conventional widely-used TIG welding.

Advantages

· Low thermal distortion even for thin sheets 

TIG welding delivers relatively shallow penetration with a large heat-affected zone, introducing high heat input into metal and causing substantial thermal deformation. Correction of resulting distortion heavily depends on operator skill and represents one of TIG welding’s biggest challenges.

By contrast, laser welding focuses high-density laser energy onto a small focal spot to melt metal. It produces narrow weld beads and a reduced heat-affected zone, minimizing thermal distortion. Pulse oscillation — rapidly switching the laser on and off dozens of times per second to repeat melting-solidification cycles — suppresses deformation even further.

· Sufficient strength of welded joints 

Laser-welded beads are narrow, which may raise concerns over joint strength. However, deep penetration provides ample internal mechanical strength beyond what visual appearance suggests. The volume of remelted and resolidified alloy is limited, resisting fracture. Industrial strength tests have verified that laser-welded joints can outperform TIG-welded equivalents.

· Reduced processing cycle time 

Low heat input and minimal distortion greatly cut workload for distortion correction. Laser welding mostly produces autogenous welds, eliminating grinding of weld protrusions. Proper parameter settings can also largely prevent weld burn marks, potentially removing electrolytic polishing steps. Overall processing time drops, lifting productivity and lowering manufacturing costs.

· Easy parameter management and operability 

Some laser welders allow saving and recalling welding parameter sets. Good reproducibility and manageability of welding conditions represent a key benefit. Experienced operators can store proven recipes that less-skilled staff can reliably replicate. This frees skilled welders for higher-value tasks while less-experienced personnel handle thin-sheet work, improving overall welding-station productivity.

Disadvantages

· Limited gap-bridging capability 

Laser welding melts metal by concentrating energy onto an extremely small focal spot roughly φ0.1 – φ0.6 mm. Consequently, it cannot weld across gaps. On machines with a φ0.1 mm spot size, even a 0.1 mm gap lets laser light pass straight through without joining the material. Countermeasures include improving bending precision and implementing dedicated fixtures.

· Poor suitability for build-up welding 

Laser welding excels at autogenous welding yet performs poorly for build-up welding. Laser energy may fail to fully reach the base metal when melting filler material. Precise co-alignment of weld point, filler wire and focal point is difficult, making it hard to guarantee adequate joint strength. If drawings specify build-up welding, reconsider whether laser welding is appropriate. Conversely, when laser welding is preferred for strength and cosmetic quality, avoid specifying build-up welds on drawings.

· Mandatory safety precautions 

Misuse of lasers may cause serious accidents. All laser products are subject to safety standards defined under JIS standards for laser-product safety. Hand-held laser welding devices fall into Class 4, the highest-hazard category. Manufacturers implement multiple built-in safety features. Always follow specifications and operating-manual instructions: establish laser-controlled work zones, wear laser-rated welding helmets/goggles, use hand-held torches equipped with safety interlocks, and strictly manage equipment access keys.

Laser-Welding Application Examples

Practical laser-welding case studies are presented below.

First example: butt welding of SUS304 sheets with thicknesses of 0.5 mm and 1.0 mm. Laser welding performs excellently on thin material, achieving low-distortion joints. Clean finished surfaces are obtained without post-weld distortion correction or burn-mark removal.

Second example: tube-to-plate welding on 1.0 mm-thick SUS304 sheet. The weld bead is visible on the inner rear side of the tube. This is an autogenous weld without filler wire. The sample is tilted for clearer bead observation; almost no deformation occurs on the SUS plate side and no burn marks appear on the reverse side.

Final sample: cabinet welding on 1.2 mm-thick SUS304. Workpieces are secured with fixtures. Laser tack welding precedes full-penetration seam welding. Completed parts exhibit low distortion and require minimal finishing work.

Key Tips for Successful Laser Welding

Laser welding delivers both mechanical strength and cosmetic appearance, offering major merits for low-distortion thin-sheet joining and straightforward parameter control. It nonetheless suffers from poor gap tolerance and limited build-up-welding performance. Keep the following points in mind to get the best results:

1. Improve bending accuracy and apply fixtures to achieve zero-gap fit-up before welding.

2. Have experienced operators define and save parameter recipes so less-skilled personnel can reproduce results consistently.

3. Retaining drawings originally designed for TIG or other conventional processes while simply switching to laser welding frequently yields poor outcomes. Design revisions may be required.

4. To fully leverage laser welding’s advantages in strength and finish quality, perform product design with laser-welding requirements in mind from the initial design phase.

Summary

Laser welding’s primary strength lies in low-distortion joining of thin sheets. It can be operated by non-specialized personnel and therefore offers great potential for modernizing craft-dependent traditional welding workflows. Once its weaknesses are properly understood and mitigated, you can fully capitalize on its many advantages.