Stainless steels are often the choice of alloy because of their corrosion resistance and strength. They are some of the most durable of metals.
Many industries, including the food, beverage, pharmaceutical, semiconductor, petrochemical and nuclear sectors rely on their corrosion resistance since even minimal product contamination of the product is unacceptable.
How to avoid loss of corrosion resistance during welding
Gas Tungsten Arc Welding (TIG) is the most commonly used stainless steel welding process. Any oxygen in the welding atmosphere can cause loss of chromium, essential in stainless steels to ensure resistance to corrosion.
To remove oxygen from the weld gas and thus prevent oxidation, a process known as Weld Purging is used. “Weld purging is the act of removing, from the vicinity of the joint, oxygen, water vapour and any other gases or vapours that might be harmful to a welding joint as it is being welded and immediately after welding” – Huntingdon Fusion Techniques HFT®.
Available Weld Purging Methods
A wide variety of purging techniques have been developed to meet the requirements for protection of the weld from oxidation.
Inflatable Tube and Pipe Purging Systems restrict the volume to be purged and they can pay for themselves in just one weld. These reusable systems are available to accommodate pipe diameters from 1” – 88” (25 to 2,235 mm).
Measuring instruments (Weld Purge Monitors®) are an essential piece of equipment to check that the oxygen content is minimised before and during welding to avoid oxidation. They can measure accurately 10 ppm.
Low cost Argweld Weld Trailing Shields® can also be added to a TIG torch to provide an additional inert gas coverage to the joint surface during welding.
The use of Flexible Welding Enclosures® allows any size and shape of component to be welded in a totally inert atmosphere.
Weld Purge Film® can be glued either side of a joint inside pipe to isolate the volume around the joint so that inert gas can be admitted for protection. The film can be removed simply by flushing with water after use.
There are more Weld Purging methods available. Please visit our website for more product information.
