I don't believe welding the root pass with a carbon steel filler metal (just because it is a F6 filler metal) would be the best idea when joining carbon steel to heat and corrosion resistant steel whether it is "just a welder performance test" or otherwise.
The welder has to weld in accordance with a WPS that is either prequalified (as in the case of AWS D1.X) or qualified by testing (as in the case of AWSD1.X or ASME Section IX). It is dubious that a dissimilar joint made with carbon steel filler metal would provide the required soundness or the proper mechanical properties. There are things like the ferrite number and the A number that must be considered. A change to either the P number, F number, or A number are essential variables that would require the WPS to be requalified. If the original WPS was qualified using ER309 and then you attempt to qualify the welder using ER70S-X for the root pass the A number is affected, thus the procedure is no longer qualified. If and when the root pass cracks due to insufficient ferrite (low ferrite number), do you blame the welder or the use of an unqualified WPS?
The manner or the technique used by the welder when qualifying is often (right or wrong) carried over to production welding. The technique used for the welder qualification test is perceived as being the correct way to weld on the particular project. It is conceivable that the welder, taking the test using ER70S-X on the welder qualification, would then attempt to use the same filler metal when making the production welds. The next thing you know there would be many people chasing each other around with hatchets in hand. It would be an ugly sight.
While ASME Section IX allows the use of either CS or SS for the qualification of the welder, I believe the WPS used must be qualified with the appropriate base metals and filler metals to be used for the welder qualification. That is, if the WPS was qualified using SS base metal with an austenitic filler metal, it isn't appropriate to substitute CS for the test coupons and then use an austenitic filler metal unless there is a qualified WPS to support the use austenitic filler metal with carbon steel base metal for the welder to follow. It would be one of the functions of the qualification process to demonstrate the combination of carbon steel welded with austenitic filler metal produces sufficient ductility, tensile strength, etc. Without following the qualified WPS, who is to blame when the welder breaks out?
I had a similar problem several years ago with aluminum. The client had tested 30 welders on aluminum and each of them failed several times. I was called in to teach the welders how to weld because "clearly, there is an issue with their skills." Upon reviewing the WPS they were using, it was apparent the filler metal was not compatible with the aluminum alloy used for the test coupons. The company never bothered to qualify the WPS, they simply assumed the filler metal and base metal were compatible and the welders lacked the skills needed to pass the required tests. Once we qualified a WPS using the correct filler metal for the alloy being joined, the welders passed the qualification tests relatively easily.
Best regards - Al
Something is most definately not correct here. One of the first things I'd do is find out if the "carbon steel" material is really carbon steel and not something of higher chrome content... just for sh*ts and giggles that would be my starting point. The specimens "should be" in my opinion, full wall thickness but only 0.375" thick in the side bend direction for side bends... thicker than that is asking for trouble. Also, Al is absolutely correct, if doing 6G tests, 4 bends are required, not 2. Looks like there's more than one issue playing out here that needs to be checked thoroughly.
What I was speaking of is a Performance qualification test using carbon pipe and carbon GTAW filler for the GTAW portion and SMAW SS for the remainder.. This is ASME ONLY I am referring to.
Also, The welder can use MULTIPLE WPS"S if required for the performance qualification test. In addition ASME allows the substitution of P1 base metals for other base metals for welder qualification. The WPS used does NOT have to have the P1 to P1 listed.
gerald
Not doubting that part, Gerald (what the Code permits re material substitutions) but what I would be looking into if I were the one investigating why the failures were occuring is what the *actual* base metal used in the qualification is / was. Is it an SA106 or is it something a bit more exotic? Since I read something about "highly qualified welder's" failing performance qualifications on boiler tube, who know's? Surely doesn't seem like 309 filler applied in a P1, Gr. 1 or Gr. 2 joint would be much of a problem... Start out looking at the basics; what's the starting materials?
I see. I think we were in two different contexts. Some more information IS needed about the original question. I thought you were commenting on one of my above statements.
I concede that ASME allows for the substitutions as per QW-423.1, but those substitutions have to be considered carefully. Just because ASME Section IX says you can do "it", doesn't mean it will work.
Good luck - Al
IMO
We all understand that. ASME does allow a welder using F-6 to be allowed to use F6 filler metals. That is pretty clear and defined. Therefore the welding of a root pass using carbon steel filler metal is qualified to use other F6 filler metals such as ER309. A Number is N/A for this situation. ASME also allows the P numbers to be substituted for P1 thru 11, 34 and 4X (Nickel Alloys).
In this case the considerations for welder performance qualification are very few in my opinion. The skills for depositing the root pass are VERY similar as are the skills for depositing additional passes with GTAW. Adding further restrictions to the code in my opinion should be considered carefully also. In some cases it may be necessary but those would be project specific. Qualifying using a purge because the weld is SS restricts the welder from welding without (Solar Flux). If you want to know if I guy can weld Stainless, get him qualified the most efficient way, set up a piece with purge, etc and let him run some and look at it visually. Let a person familar with welding watch.
It will work JUST fine to weld two pieces of Carbon steel together using ER70S-x without a purge then depositing filler metal such as E309-xx over that and bending or shooting it. The welder qualification test would have to have a qualified procedure however as mentioned in the code WPS's could be written to support various situations provided.
I have bent CS to CS using E309-xx filler metals more times than I can count. The coupons bend fine.
Most of the welders that can put in a "Code Acceptable" root pass using CS without purge have NO PROBLEM doing the same on Stainless. It may not have that "golden arm, come look at MY weld!" look to it when its done, but its acceptable.
Take qualifiying plate welders on NiCrMO-4. Would it be wise to use C-276 base material ? I think it would be a terrible waste of money.
The entire welder qualification/documentation/requalification etc.. seems to be OVER CONTROLLED. I am for code compliance but going above and beyond seems a little silly.
Topic Welding Industry / Inspection & Qualification / Bend Test on dissimilar metals 309 filler on Carbon?
If you give the guys in this forum the materials you are useing and the code you are useing they can tell you exactly how you need to be testing these welders and then you can go and double check this guy that is doing your testing. My bet is on the wrong diameter plunger. Anyone want in on this one?
