Guide to Laser Beam Welding
Table of Contents
Laser welding is a type of welding process that uses a laser beam to join multiple pieces of metal. This method uses a laser beam directed at the welding zone. The laser welding device relies on a high-intensity laser beam to heat the material, which melts and forms the weld. This technique is used to weld small components and materials that are difficult to weld using other methods. Some of these techniques may include hot gas welding, infrared welding, hot gas welding, etc.
An automated process, online quality control, and high welding speeds are a few of the features that make laser welding the method of choice for various industrial applications.
The following are a few types of industrial laser welding processes.
- Spot and Seam Welding: These methods are employed for smallest welding spots to continuous seams several meters long.
- Deposition Welding: This process is used to modify and repair molds and tools.
- Scanner Welding: It is one of the most productive and fastest welding processes. This process is employed in exhaust gas coolers, housings, automotive engineering, and a throttle cable. It is used to weld complex 3-D automotive parts, very small spots, short seams, etc.
- Heat Conduction Welding: This welding is employed for visible edges and thin-walled parts.
- Soldering: In this method, mating parts are fused using solder, or filler material. Laser soldering is used to weld car trunk lids, or fuse automotive parts.
- Deep Penetration Welding: This method is used when multilayer welds or deep welds are required. In this process, a high-density laser beam is used, which melts the metal and welds it.
Laser Beam Welding Processes
Unique Laser Welding Techniques in Use
The following are some of the unique laser welding techniques in use:
- Twin Beam Laser Welding: In this method, twin beams are used simultaneously to control weld beads and its weld pool geometry. For instance, a CO2 laser beam and excimer are combined with welding metals with high reflectivities such as copper or aluminum.
- Laser Brazing and Soldering: In this method, a laser beam is used to melt a filler that welds joint edges. It was used for Surface Mounting of PCBs in 1980’s.
- Hybrid Welding: This refers to the process, where the laser welding is used with other welding processes for specialized applications in the steel industry. Some of the compatible processes include TIG (Tungsten Inert Gas), MIG (Metal Inert Gas), or plasma welding.
Laser Welding Techniques
The following are the popular modes of laser welding:
- Conduction Welding: This is performed at low energy levels, and produces shallow and wide nuggets. It is conducted in two ways:
- Direct Heating: The weld is created by melting certain portions of the base metal. It can be conducted through CO2, pulsed ruby, and diode lasers.
- Energy Transmission: The laser beam energy is absorbed through unique inter-facial absorption methods.
- Keyhole Mode: This mode creates narrow welds. The focused laser beam penetrates into the work piece surface and forms a “keyhole” cavity, which is filled with a metal vapor. Generally, high-density beam 106-107 W/cm2 is directed at the surface, which produces metal vapors that fill the keyhole cavity.
Metals for Laser Beam Welding
Laser welding can be used to weld components and parts made from the following types of metals:
- Carbon Steel
- Low alloy and stainless steel
The following advantages account for the popularity of a laser welding.
- Close tolerance (± .001 inch)
- Non-contact processing minimizes unwanted stress on materials
- Localized beam ensures low thermal and mechanical strain on parts
- Requires no tool changes
- High precision welding or cutting is achievable
- Reduces distortion in heat affected zones
- Burr-free edges help save on secondary finishing
- Produces welds with minimal distortion
- Comparatively cleaner than electric arc or gas welding
- Automated process allows excellent repeatability
- Minimizes setup and production time
- Low thermal input
- Can be used in open air
- Transmission over long distances for accessing hard to reach areas
- Can be used to weld wires with small diameters such as 100 microns
- Ideal for processing materials with difficult geometries
- Requires no consumables unless fillers are used for soldering
- High-density cutting is achievable
- Clean processing produces no dust, shavings, etc.
- Cost savings due to reduction of floor space, number of stations, scrap and component weight
The following are few parameters that control the quality of the laser welding machine
- Laser pulse energy: This is the unit of the maximum output energy from a single pulse of the laser. It is a parameter to decide the maximum energy used by the laser machine.
- Laser Pulse Frequency: This indicates the amount of pulse energy produced by a laser in a second.
- Laser Beam Flare Diameter: This is the key parameter to gauge the performance of a laser. It helps in determining the processing scope and power density of a laser.
- Choice of Power Waveform: A wide pulse width produces larger welding spots, and higher peak power produces deeper welding spots.
- Laser Pulse Waveform: This is one of the problems in the laser welding process. When a high strength laser beam hits the material surface, about 60 – 90% of the energy is lost by reflection. The reflectivity can be changed by altering the materials’ surface temperature.
If you are offering laser welding services, you need to ensure the following points.
• Understand the benefits of laser welding for a particular process.
• Ensure safety precautions are used such as shielding, safety-light paths, safety interlocking, beam termination, and key-operated switches.
• Train a professional and ensure that they are following all necessary precautions such as using right eyeglasses, keeping the machine and surrounding areas clean, using CO2 chemical fire extinguishers, filtration, and exhaustion systems, etc.
• Ensure that you set up a security management system in place. It will allow you to avail services of a specialized personnel or agency who will help you understand medical monitoring and safety training.
If the above points are kept in mind, you will enjoy the benefits of laser weld systems for a long time.
For Additional Reading
Presentation by Instructor Ramesh Singh on Laser Welding
Page Author: Jeff Grill