While Austenitic S/Steels are essentially quite easily welded, there are a number of issues when welding these materials.

One of these issues is that one tends to get grain growth. The more you tend to keep the temperature up, the bigger the grains become. This reduces both the strength and impact properties.

Another problem is sensitization. Typically this is not a problem with the new L grades, but COULD become a problem if you consistently re-weld.

Another possibility is the formation of Sigma phase if the temperature is kept high enough for long enough. With repeated re-welding, this could also become a problem. Sigma phase formation leads to embrittlement of the material.

So how many times can you re-weld before any problems start? This is a difficult question to answer, because it not only depends on the number of times you re-weld, but also on other welding (and back-gouging) parameters, as well as the precise composition of the material.

Another issue is obviously distortion. With each time that you re-weld, you will typically experience more distortion. Depending on your weldment geometry, you can end up with an unacceptable situation after the second re-weld.

My rule of thumb would be that re-welding an L grade three times SHOULD not lead to any serious metallurgical problems. If you need to re-weld more than this, get metallurgical advice for your particular situation.

Certainly, when welding a non-L grade, you will pick up sensitization problems quite quickly. Depending on your welding parameters, this can happen even during the first time round.

Hope this helps

Niekie Jooste