If a welder is qualified in Carbons Steel for GTAW process he is qualified to make Stainless Steel Weld as per SeC IX then why we qualify welder separate for Stainless Steel. What need to consider as per standard?
Yes @aggarwalmohit05. ASME IX 2019 - Table QW-356 - GTAW Welder - essential variables.
- Test coupon on carbon steel (eg. P-No. 1) may qualify for stainless steel (eg. P-No. 8), if all essential variables are unchanged, see range of alternate base material qualification for welder qualification in QW-423.1. QW-408.8 - backing gas may be added to support welding root.
- Other, your test coupon qualified on stainless steel may cover for carbon steel material if all essential variables are unchanged. QW-408.8 - backing gas do not omitted.
For SMAW: change F-Number not allowed to QW-404.15, your welder have to qualify different test coupon.
- AWS A5.1 E7016 - F-number 4.
- AWS A5.4 E316- F-number 5.
It is not mandatory to qualify for SS again with GTAW as per ASME SEC IX. However internally in order to asses the potential or to check the ability of the welder whether he can make sound weldment he can be ensured through a test on Stainless steel. This can add more value to your QMS.
The point is that as per the code the welder is qualified but in actual case a welder who is qualified only on CS materials will make terrible wleds on SS .
The properties of the two materials are entirely different.