As part of our top tips series, we will be undertaking a Q&A with Paul Flynn – an experienced Supervisor at John Tracey Specialist Welding, each month, focusing on the range of exotic metals the team work with. This week, it is stainless steel.

1. Three top tips when welding stainless steel are:

There are many top tips for welding both martensitic and austenitic stainless steels; There are also many welding processes that can be utilised to weld stainless but for this piece we will be looking at austenitic stainless pipe work in a workshop environment using 141 (TIG) process.

• When performing single sided full penetration butt welds of stainless steel, the top priority is ensuring a sufficient purge and with this in mind it would be recommended to use bungs and dams as this can help purge a specific area of pipework.
• Post weld pickling and passivation is highly recommended – this removes any carbon contamination, discolouration from welding, scale etc. and passivation helps to reintroduce a chromium rich layer to the stainless steel.
• Segregation of not only your work area but also your tools and consumables should be the norm when welding stainless steels to high quality finishes, as this massively reduces the chance of cross contamination with carbon particles.

2. What equipment is required?

• Air/water cooled tig inverter, purge meter, bungs and dams, purge hoses/tape, project specific tools and consumables.

3. What preparation is key?

• The preparation for welding stainless steel pipe would be segregation of material and tools. Another key initial step involves achieving the correct purge in line with the welding procedure /WPS as this allows a more mechanically sound weld to be carried out.

4. Key challenges and how to overcome them:

• Two key challenges would be reducing the chance of cross contamination and controlling the distortion caused by stainless steels low thermal conductivity and high coefficient of thermal expansion. These issues, although highly undesirable, are quite easily reduced by using tried and tested methods and procedures. Reducing cross contamination of stainless steel can be achieved by segregation of either work area or even better a dedicated workshop and tooling. Reducing distortion can be achieved by many means. As it is pipework with full penetration butt welds, pre-setting the joint is not an option but adding extra bullets, keep welding runs to a minimum, weld sequences and many more methods can help effectively reduce distortion when welding stainless steel pipework.

5. Safety considerations

• As with any and all welding, respiratory health problems are a major issue and as such extraction, ventilation, air-fed systems are required. In addition, you should have a general awareness and respect for the dangers that welding as a whole can pose.