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Welding
As a joining method, welding has been around for centuries. Today around 100 welding methods are used in different industry sectors.
The use of individual or mixed industrial gases to optimise the welding process dates back to the 1940s and 50s. Since then the shielding-gas based welding processes have emerged to be the dominant group of welding methods.
Important gas-shielded welding methods include MIG, MAG, TIG and plasma.
The 1980s and 90s saw many welding innovations including laser, tandem and laser-hybrid welding.
MAG welding is the preferred method for normal unalloyed steels, but is used as well on stainless steels and other materials.
The gases used in welding perform an important function in that they shield the molten weld pool and molten filler material from the damaging effect of air.
High deposition MAG welding
With GMAW becoming more widely used in the industry worldwide and increasing demands towards higher productivity the demand for higher deposition rates arose. Generally speaking, the deposition rate depends on the wire feed speed and the wire diameter. A higher deposition rate can be used either to weld larger sections per weld run, thus reducing the amount of layers necessary to fill a weld, or to increase the travel speed.
By definition, the range of high-deposition welding begins at a wire feed speed of 15m/min or alternatively at 8 kg/h deposition rate, whichever is exceeded first. Otherwise the process is called conventional GMAW.
There are several variants of equipment setup, ranging from single-wire GMAW (one power source, one wire feeder, one torch) up to tandem GMAW (two coupled power sources, two wire feeders, one torch). The choice of equipment and setup type depends on the application, i.e. the torch guidance (manual, tractor or robot), plate thickness and possible weld preparation. In a single wire setup it is also possible to use a flat strip instead of round-shaped wire. In most cases it is advisable to use high-performance GMAW in an automated setup.
High-deposition GMAW can greatly benefit from proper welding gas selection. In comparison to standard GMAW gases the CO2-content is often reduced in order to obtain more stable metal transfer in the arc. The addition of helium to the welding gas compensates for the reduced penetration caused by lower CO2-content and also provides additional energy in the process, enabling higher travel speeds and better weld quality.
Laser welding
Within the last two decades, industrial lasers have advanced from exotic to state-of-the-art technology in many fi elds of manufacturing. While laser cutting is certainly the most popular application of highpower lasers, other processes such as laser welding and laser surface modification are also becoming the process of choice in their respective
industries.
Laser welding is increasingly being used in industrial production ranging from microelectronics to shipbuilding. Automotive manufacturing, however, is among the industrial sectors which have proven to be most outstanding at developing applications
that take advantage of the many benefits of this technology:
- low heat input
- small heat-affected zone (HAZ)
- Low distortion rate
- High welding speed
These characteristics have made laser welding the process of choice for many applications that used resistance welding in the past. By adding the benefits of single-sided access, laser welding is given another strategic advantage, allowing it to open the door for a multitude of new applications.
