Laser beam welding is a welding process that forms a bond between 2 or more materials using a laser beam. The term laser stands for Light Amplification by Stimulated Emission of Radiation. Laser Beam Welding is a non-contact process that requires the welder to have access to the weld zone from a single side of the weld. Laser beams have enough energy to melt the metal pieces on impact as soon as they touch them. Once the metal pieces cool a solid weld is formed.
Video credits to Solutions With Innovation. It explains what Laser Beam Welding is.
What principle does Laser Beam welding work on?
Laser beam welding works on the principle that electrons tends to get excited once they absorb energy. After some time electrons return to their ground state, at which point they’ll emit photon of light. The concentration of emitted photon, once increased by the stimulated emission of radiation forms a concentrated laser beam. In other words, light that’s amplified by stimulated emission of radiation is considered a laser.
What types of lasers are used for Laser Beam welds?
Laser beam welding uses both solid state and gas lasers.
What are solid state lasers?
These lasers uses a gain medium that’s solid rather than liquid. Solid state lasers operate at wavelengths at around 1 micrometer, which is much shorter than that used by gas lasers. As a result these lasers require operators to either wear special eye-wear or use special screens so they damage their retinas. Nd:YAG lasers can operate using both continuous and pulsed mode, while other lasers operate only in pulsed mode. The typical solid-state design is a single crystal shaped as a rod around 200 mm long and 20 mm in diameter (both ends are flat). A flash tube containing krypton or xenon surrounds this rod.
Once flashed, a pulse of light that lasts around two ms is emitted by the laser.
The typical medium for solid state lasers is glass or crystalline “host” that has a dopant, namely neodymium, chromium, erbium, thulium, ytterbium. Most dopants are rare-earth elements because the excited states of ions aren’t strongly coupled with the thermal vibration of phonons.
What are gas lasers?
Gas lasers use low-current, high voltage power sources to supply energy required to excite the gas mixture which is used as a lasing medium. Gas lasers operate in both pulsed and continuous mode – the wavelength of the CO2 gas laser beam is 10.6 μm. Fiber optic cable absorbs and is destroyed by this wavelength, which is why a mirror delivery system and rigid lens are used. The power output of gas lasers is higher than that of solid-state lasers.
What are fiber lasers?
The main medium used in fiber lasers is the optical fiber. Fiber lasers are capable of power of up to 50 kW and are increasingly used for robotic industrial welding.
What modes are there in Laser Beam Welding?
There are a few types of lasers used in laser welding. There’s: Conduction mode welding, Conduction / Penetration mode, and Penetration / Keyhole Mode.
What is Conduction Mode Welding?
Conduction Mode Welding is performed at lower energy levels and forms a wide, shallow weld nugget. In conduction welding there is both direct heating and energy transmission.
What is Conduction Welding?
In direct heating the heat flow is governed by classical thermal conduction from a surface heat source.
Welds are made by melting portions of the base material and can be made using CO2 and pulsed ruby lasers using a variety metals and alloys. You can also use Nd:YAD and diode lasers.
Energy transmission, on the the other hand, absorbs through novel inter facial absorption methods. Absorbing ink is then placed at the interface of the lap joint. The absorbing ink then absorbs the laser beam energy which then conducts this energy into a surrounding metal (of limited thickness) which forms a molten inter-facial film that then hardens to form a welded joint.
What is Conduction / Penetration Welding?
Conduction / penetration welding occurs at a medium energy density which results in more penetration for the weld.
What is Penetration / Keyhole welding?
Penetration laser welding is performed when the laser forms a hole that is then sealed by the molten material behind the laser.
Where is Laser Beam Welding used?
Laser Beam Welding is typically used for applications done in high volume. These processes are done using automation. The metals typically used with Laser Beam Welding are:
- Carbon Steels
- High Strength Low Alloy Steels
- Aluminum
- Stainless Steel
- Titanium
What are the advantages of Laser Beam Welding?
Laser Beam Welding yields quite a few advantages, including:
- No filler metals necessary
- It’s incredibly accurate
- There is no secondary finishing necessary
- Laser Beam Welding can be used in open air
- It works well with high alloy metals without difficulty
- It can be transmitted over long distances while maintaining most of it’s power
- It doesn’t generate x-rays
- There’s a narrow heat affected zone
- There’s very little distortion in it’s welds
- Can weld small, thin components
What are the limitations of Laser Beam Welding?
Laser Beam Welding, like most other welding processes also has it’s own limitations, including:
- It has high maintenance costs
- The equipment is expensive
- The cooling speed of the process causes cracking in materials
- The surfaces of the metal can easily be damaged
