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Up Topic Welding Industry / Technical Discussions / effects of welding on stainless steel
- - By Chen Date 01-14-2002 11:52
What bad effects will be brought for austenitic stainless steel (316 or 316L), if welding several times (4~5times) on the same position.
Are there any limits to the times of welding on the same position for austenitic stainless steel in criteria ? why? thanks
Parent - - By - Date 01-14-2002 17:59
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
Parent - - By Chen Date 01-16-2002 12:48
thank you for your response .
As you said, re-weld several times (more than 3 times)on the same place may resulted in grain growth, sensitization or Sigma phase formation of austenitic S/steel(316L), this will reduce both the strength and impect properties. Besides, whether it make corrosion resistance bad? This is my intresting point. So, I want to do some experiments, one is intergranular corrosion test, the other is SCC in boiling 45% MgCl2. Could you give me some suggestions.
1.should I choose Huey test or Strauss test or both to test for resistance to intergranular corrosion.
2.Is it appropriate to adopt U-bend stress corrosion test specimen to assess the effect of multiple re-weld on stress corrosion resistance in terms of the cracking time.

thanks again
Parent - By - Date 01-17-2002 18:22
If you get sensitization, the corrosion properties will definately be affected. You can expect to experience intergranular corrosion.

Regarding the exact test to use, I am not qualified to advise you on. You must just make sure that you have control samples from the same heat of material to compare the multiple welded samples to.

Niekie Jooste
Up Topic Welding Industry / Technical Discussions / effects of welding on stainless steel

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