Welder Qualifications

Yes, the code is clear. It allows use of F6 filler metal (based essentially on its usability characteristics i.e., determines the ability of welder to make a satisfactory welds with a given filler metal) on a base metal. Here the interpretation is ability to use it - i.e., two types of bare filler metals for GTAW (QW-433) process.

At the same time,it has to be compatible to the base metal from the standpoint of metallurgical properties, post-weld heat treatment, design and service requirements and mechanical properties.

QW-431 states that, base materials or filler materials within a group should not be indiscriminately substituted for a metal that was used in the qualification test. I.e., ER 70 S-2 though falls under F6 should not be used for welding SS base metal, since no compatibility between both.

For welding SS base, we use a SFA 5.9 bare wire (again a GTAW process), falling under F6 (like ER 70 S-2) but has compatibility to the base metal in all respects. Here we depend upon 'A' nos also for a PQR.

That is why we write a WPS and qualify it with a PQR. The base metal, filler metal (F nos & A nos), parameters, procedure are clearly stipulated and it is tested for its approval through a PQR. If it is successful, the WPS & PQR are accepted and we go ahead with WPQs.

If it is not so, we change the filler metal even though both falls under same F no. (to get the said compatibility) with regard to base metal and attempt for a successful PQR. Sometimes, we may land up in failures due to wrong procedure (in alloy steels) , even though base and filler metals (F nos) are compatible.

To conclude QW 433 & QW 431 , are clear in its interpretation/application and do not allow a indiscriminate use of F nos, but allow a selection of F no for a given base metal.

Sridhar.

As usual you 100% correct in your statement Sridhar my friend. It boils down to the difference in the requirements for qualifying a procedure and qualifying a welder on a process. While I agree on the principle of both welding processes being similar and this is what is stated in the ASME code I do not agree with it being even close to the same. I might see it closer on say carbon steel and 1-1/4 or 2-1/4 chrome moly processes but not on S/S that would require a purge.

On the welder level the welding carbon steel GTAW process with no purge is not even close to the same as using the GTAW process on stainless where a purge is required. I would never accept or allow this on a job I was QC manager on and would require a separate welder test on each material. In the USA every company I have welded/Qualified for or inspected with in the last 30 years have required the same separate welder qualifications for carbon steel and Stainless steel.

Pipe welder,

Thanks for your comments and I appreciate it. You had mentioned,

" I do not agree with it being even close to the same. I might see it closer on say carbon steel and 1-1/4 or 2-1/4 chrome moly processes but not on S/S that would require a purge."

From my end, I never indicated that a welder using ER 70 S-6 (F-6) and qualified with GTAW without purging on CS can directly weld using a similar F-6 graded filler metal and GTAW process on SS base without purging . I clearly said,

" That is why we write a WPS and qualify it with a PQR. The base metal, filler metal (F nos & A nos), parameters, procedure are clearly stipulated and it is tested for its approval through a PQR. If it is successful, the WPS & PQR are accepted and we go ahead with WPQs."

It is obvious that P, F, A nos being part of essential variables requires re-qualification for any change in between them. Not only SS but even a Cr-Moly steel requires purging and it is also a essential variable under QW 408 - 9 & 10. So CS welding done without purging (backing) for CS will not qualify welders for AS & SS automatically. We require a separate WPS & PQR for each 'P' no also, before qualifying the welders accordingly. You said,

In the USA every company I have welded/Qualified for or inspected with in the last 30 years have required the same separate welder qualifications for carbon steel and Stainless steel.

Yes. I agree. No dispute about it. Not only in USA, but throughout the fabrication world, we do not allow it. Here QW-431 comes to our rescue, It says clearly:

The 'F' grouping does not imply that base materials or filler materials within a group may be indiscriminately substituted for a metal that was used in the qualification test without consideration of the compatibility of the base and filler metals from the standpoint of metallurgical properties, post-weld heat treatment, design and service requirements, and mechanical properties.

Hence, I feel QW-433 allows any F-6 qualified welder to use a similar F-6 filler metal provided: it meets QW-431 requirements without doubt.

To conclude, SFA - 5.18 (ER 70 S-2, CS filler metals used in TIG & MIG), SFA-5.9 (ER 308L, SS filler metals used in TIG & MIG) SFA-5.28 (ER 80S-B2, Low AS filler metals used in TIG & MIG) though falling under same 'F-6' requires a separate WPS & PQR due to variable 'P & A' (QW-431) nos.

I gave my view points on QW- 431(ability to weld satisfactorily with a given filler metal and to reduce the no. of PQR & WPQs where it can be done logically) and 433 (alternative filler metals for WPQs – but, use of F-no 6 alone depends upon again on 'A' no. – see foot note) where Mr. Richard Peel had doubts towards its interpretation. I feel both have its value, but should not be used indiscriminately.

Sridhar.

I think you are missing the fact that by changing to a different base metal and P number is an essential variable also and even if the F-number is ok the different base metal would require you to qualify a new WPS and PQR and then Qualify the welders to this new procedure. Without digging to deep into your situation to know all the details I am only speaking from my experiences and ASME requirements I can say that I am 100% sure that I have never qualified a welder on a carbon steel WPS and it cover him for any type of Stainless steel welding.

This being said you can by using S/S electrodes such as E-309 on carbon steel coupons qualify welders to weld stainless to carbon. This can save money by eliminating the need to have one side of the test coupon be made from stainless for each separate welder qualification test only and this doesn't work on the original WPS/PQR process qualification and you have to be careful to note that it will qualify the welder to weld with a backing only.(backing being in the form of inert gas in this case) Because of the 309 electrode being an alloy that would require an inert gas purge It would not qualify the process or welder to make a carbon steel root pass with out backing which is the normal way to weld a carbon steel root pass. It would however qualify the welder to make all other passes and after the root pass, welds utilizing a backing strap, and fillet welds on other carbon or stainless materials in the same P group as long as they are in the thickness range.

I qualified a 3 process tri-metal WPS and did the weld in 45 degree position so that it also qualified the welder that welded the WPS/PQR coupons on the 3 different P-number metals at the same time. This can be done fairly easy on weld metal overlay and corrosion resistant cladding processes but as far as I know it willl not work on a butt weld procedure although I have never tried it .

I did this to qualify a WPS and welders to weld on several ASME vessels at the mill I work at that are overlayed with S/S and also have inconel thermo-well-nozzles that have a an area where the stainless electrode could possibly be interfacing or fusing with both the inconel nozzle, the S/S cladding material, and the carbon steel base metal at the same time. This process also worked for welidng with inconel elecrodes on S/S but because of lower tensile strength of the carbon steel electrode it would not qualify one to weld on either stainless steel or inconel with a carbon steel electrode and I far as I know there would be no benifit or reason in doing this on what I consider any above the board "legal" circumstance.

Thanks,

That's how I interpreted QW-431. Although several colleagues had different opinions.

R. Peel

Thanks for the time and comment.

R. Peel

Unfortunately, you and everyone else in this thread are incorrect--along with a majority of Managers out there, and this is causing excessive weld testing.

If you look at essential variables required for Welder Performance Qualification testing you will see that each variable has a sub-section in the remarks. Look at QW-356 and where it notes a change in P is an essential variable it also has Paragraph QW-403.18 cited.

QW-403.18 states: A change from one P-number to any other P-number or to a base metal NOT listed in QW/QB-422, EXCEPT as permitted in QW-423, and in QW-420.2.

So now if you go to QW-423 it lists the base material qualified on and what it qualifies you for. So if you qualify for P1, you are qualified for P1-P11, P34, and P4X.

So basically a person that does a Carbon GTAW test with OR without backing gas, can essentially weld ALL F6. Anyone testing further has been overtesting their welders--according to code.

Further, QW-431 is used to denote PROCEDURE variables--this is not the same as Welder Variables in regards to qualifying a welder.

Variables for qualifying a welder are found in QW-356 for GTAW.