Achieving good stainless steel welding colours:
Welds exhibiting such colours as blue, violet or brown may suffer reduced strength, which could lead to a loss of corrosion resistance and could be rejected at worst and cause extra, expensive cleaning operations at best.
Welding stainless steel:
Stainless steel offers a much greater corrosion resistance than carbon steels for a whole range of gases and liquids.
Cleanliness of stainless steel allows it to be the material of choice for many industries, including nuclear power stations, refineries, liquid natural gas regasification systems, food manufacturing, beverage production notably, but not limited to beer, cider, wines, soft drinks, milk etc, building of semi conductors and related electronic components and many other applications.
When welding, stainless steel reacts with oxygen, nitrogen and water vapour when present and this will destroy the corrosion resistance of the material around the joint and also cause areas of weakness and potential joint failure.
To prevent these effects, the welding zone must be covered or shielded with an inert gas during welding and for some time afterwards while the weld metal is cooling to below its oxidation temperature.
Achieving good stainless steel welding colours:
Shielding gas:
For high quality and repeatable welding of stainless steels, there is a requirement for the purge gas to contain less than 200 ppm O2 for some applications, less than 100 ppm for other and less than 50 ppm for the most specialised of clean applications, for example the welding of semi conductor and nuclear tubes and pipes.
Products for shielding with stainless steel welding:
Stainless steel components can be manually or automatically welded with robots inside Flexible Welding Enclosures®. These inexpensive welding enclosures can be easily purged with argon for a fraction of the gas cost that would arise when welding such items individually in air, with local gas coverage. Furthermore, the total coverage can be down to less than 20 ppm O2.
The flexibility of such Enclosures makes it very comfortable for welders, verses the use of a rigid metal glove box or chamber. In addition, the Enclosures have a large viewing area and a panel below with multiple access points for items like purge gas, electricity for manipulators or robots plus leads for welding torches etc.
For the welding of pipes and tubes, Inflatable Tube and Pipe Purging Systems are available, including PurgElite® and QuickPurge® models, which restrict the volume of the pipe to be purged, making huge savings on time and inert gas costs while providing bright, shiny, non oxidised welds.
Argweld Weld Trailing Shields® are also common when welding stainless steels. Flat models for sheet metal and large tanks and radiused models for all sizes of pipe.
They simply attach onto any welding torch, providing an additional inert gas coverage while the weld is cooling below its oxidation temperature.
Weld Purging Monitors® are used by most stainless steel welders around the world to check for the correct level of oxygen prior to beginning the weld.
The most popular Model is the PurgEye® 100 which measures oxygen level down to 100 ppm and there is a choice between six other models that measure all the way down to 10 ppm.