Laser beam welding (LBW) or more commonly laser welding (LW) is a thermal joining technique to bond metals (and plastics) by laser. Laser welding is usually a deep penetration, keyhole welding technique in engineering applications. The laser beam is focused and aligned to the surface or a position slightly below the material thickness. Due to the extremely high power density (> 106 W / cm2) of the focused beam, the metal is vaporized within the keyhole and as the beam passes along the joint, a surrounding liquefied melt pool flows into the rear of the keyhole, the melt pool solidifies and forms a weld. Laser welding differs from laser cutting as the melt pool is not blown away by a gas jet, but the molten material is protected by a low pressure shielding gas process.
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Method
In pure laser welding, a consumable filler material is not used. The key feature of pure laser welding in steel joining applications is the weld seam has close to the same material properties as the base metal. In certain cases, it is possible to add a filler wire to the laser weld, and this can be a cold feed wire or induction heated wire to reduce thermal effects in the melt pool. Another common method is hybrid welding where the laser and MAG welding process is combined. In hybrid welding the heat input is on a higher level than in pure laser welding but still much lower than traditional MAG-welding. Hybrid welding permits for higher welding speeds and allows for thicker materials.
The laser welding process is almost invariably used in large-scale applications with automation, allowing a welding speed of 1-5m/min. Traditional CO2 laser is still in use; mainly in larger panel welding lines, but fiber laser is becoming more common in newly installed laser welding lines, and is the only option on today’s advanced 3D robotic welding lines. Laser welding and laser hybrid welding are standard working methods in automotive industry, ship building and railway industry with a fast growing trend within agricultural equipment, tipper bodies and containers.
Laser welded tailor blanks feature in every car produced since many years with different thickness and different steel grades within the structural parts such as the sub frame, suspension bars, reinforcing and safety parts, etc. with hundreds of millions of LWTB produced annually by 3D robotic welding lines.
Laser welding is a low heat input welding method with narrow full penetration weld which makes an aesthetic final result possible. When thin large sheets are joined, laser welding is in many cases the only welding method to avoid thermal distortion of the end product. Laser welding is the best welding method to minimize loss of base material properties, such as hardness and strength.
Laser welding features
Benefits
- Excellent mechanical properties
- Very narrow HAZ
- Very high efficiency
- Very good wear properties
- Low thermal distortion, i.e. excellent flatness
- Long and wide sheets with large possibility to tailor thickness and properties
- Cost efficient compared to traditional methods
- Allows welding of sheets with different steel grades and dimensions
Drawbacks
- High investment costs compared to traditional methods
- Limited material thickness (today’s maximum 25mm by hybrid)
Recommendations
Laser welding is the best recommended welding method for thinner gauges, high strength and wear resistant steels.
Our offer
SSAB can offer laser welding services including welding wide and long sheets for XXL tailor blanks:
- Lengths up to 20,000mm
- Widths up to 5,000mm
- Thickness up to 6mm (8mm is possible in certain cases)
There is a possibility to combine laser welding with other metal processing methods, for example shape cutting (laser/plasma) and press brake bending, to fulfil your complete requirements for the processing of XXL components.
Laser welding quality meets requirements according to EN 13919-1 C (level B on request)
