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Up Topic Welding Industry / ASME Codes / metal substitution for welder qualification
- By dlmann (**) Date 04-18-2012 14:51
I’m at a new job and I’m trying to change my way of thinking but can't quite get there.
I’ve always qualified welders following a qualified WPS.  At the old job I used P1 coupons with F44 filler metal because I had had a P1 to P44 base metal WPS. 
Here at the new job there is a P44 to P44 WPS.  P1 coupons are suggested for welder qualification citing the first sentence of QW-423.1.  “Base metal used for welder qualification may be substituted for metal specified in the WPS…”
How is this reconciled with QW-301.2 “The performance qualification test shall be welded in accordance with qualified Welding Procedure Specifications”? 
Is QW-423.1 just what it  says or is there more I missed?   
Regards, Donnie Mann
- - By 803056 (*****) Date 04-18-2012 19:25
No problem. You qualify the WPS to demonstrate the proposed procedure will produce the mechanical properties required by the code. Poof, all the mechanical tests pass and the WPS is now qualified.

Now you need to qualify welders. The welders have to demonstrate they are capable of depositing sound weld. Welder qualification is a different task with different objectives than qualifying the WPS. Section IX permits the employer to substitute inexpensive base metals in place of the more expensive base metal listed by the qualified WPS. The goal is to save the employer money. In the case of substituting a P-1 (carbon steel) in place of a nickel alloy (P-4X) the savings is substantial. The welder still has to demonstrate the ability to deposited sound weld using a filler metal with the same F-number as that listed in the qualified WPS. In the code committee’s view, there is no difference in welding carbon steel with a nickel alloy filler metal or welding nickel alloy with a nickel alloy filler metal. They see no difference in welding carbon steel with an austenitic stainless filler metal or welding austenitic stainless steel with austenitic stainless steel filler metal. Whether you or I agree with the code committee’s position isn’t an issue, it is what they decided was acceptable. If you have any qualms, do it the “right” way and follow the qualified WPS to the letter. There’s no problem with the latter.

If you haven't figured out how our economy works, it is simple; it is all about the money. In this case, the code is making concessions to the contractors that are trying to qualify welders and yet spend as few dollars as possible doing so.

Best regards – Al
Parent - - By TimGary (****) Date 04-18-2012 19:42
Good reply Al.
Parent - By jon20013 (*****) Date 04-18-2012 20:50
Keep in mind there are plenty of "traps" to be wary of... many people do as mentioned above and then list that the welder is qualified for P1 - P11, P3X, P4X but don't consider ALL of the variables.  For example if you use an austentitic or nickel filler you may use a purge but you wouldn't for P1 materials obviously.  Deletion of purge is an essential variable so you'd be stuffed for welding on P1's.  Thats just one very simple example; be cautious and aware of the variables when setting qualified ranges.
Parent - - By dlmann (**) Date 04-18-2012 21:39
Thanks Al, this is eye opening to me.
Parent - By 803056 (*****) Date 04-18-2012 21:49
John makes a very good point. While the base metal substitution is permitted, the other essential variables must be considered.

I hesitate to say most contractors simply use the base metal listed by the WPS because there are a few that try to economize by taking advantage of the liberties permitted by ASME Section IX. They use the less expensive base metal and get into trouble when they fail to consider the factor John mentioned, root purge as an example, but you must also use a filler metal with the proper F number, etc. Just because the code says it is permitted doesn't make it a good idea unless you consider everything. One must never, never forget what the letters ASME really stand for!

Best regards - Al
Parent - - By rcwelding (***) Date 04-19-2012 09:27
Al...  There are some people on this forum that I hope to never see another post from.  You are NOT one of those people.  Thank you so much for being on this forum And Sharing what you know with the rest of us....!
Parent - By 803056 (*****) Date 04-19-2012 12:57
You almost had me with that post. I started reading and began to wonder if I should read the entire post. I'm glad I did. Thanks for the compliment.

There was a similar question posted in another forum. One of the posts in the thread was from an individual that seemed to confuse the difference between requirements for production welds and the requirements applicable to qualifying a welder. The poster asked why would someone disregard the WPS and substitute a different base metal for the one that was listed. Wasn't it the purpose of qualifying the WPS to verify it would produce acceptable welds? It didn't make sense to the poster to use the proven WPS for a different base metal. Maybe it was a case where the poster didn't read the entire thread or maybe there was real confusion on his part. I can see the former being true, I've done that myself.

This forum has many contributors that are true experts in the field of welding. There isn’t a day that goes by that I don’t learn something new from people willing to give their time and opinions on a wide range of subjects relating to welding and inspection. It is easy to recognize who they are, harder yet to list each one individually.

Just to update everyone on the exploits of Stephan, our good friend from Germany. As most of you know, he recently completed his Masters program in welding engineering. What I appreciate about Stephan is that like many of us he was a welder that earned his paycheck burning electrodes for an international company. Stephan has an insatiable curiosity to learn more about the science of welding. He studied about welding on his own and decided he would like to earn a degree in welding engineering. He applied for admission to a Masters program in England without first earning a Bachelor Degree or completing any college courses relating to welding. They balked; they told him he didn’t have the prerequisites to be accepted into the program. He was unrelenting and told them he studied about welding and science on his own. They told him his application would be considered if he could pass an examination on subjects relating to the science of welding technology. He passed the examination, completed his studies, and graduated at the top of his class. Now he is contemplating pursuing a PhD in Welding.

Welding is one of the few endeavors that provide each of us with challenges, a sense of satisfaction and a job well done, and opportunity to advance to any level we want to pursue. We are the limiting factor in our pursuit of knowledge and opportunity. The technology is there, the resources are there, it is entirely our decision to maintain the status quo or to take advantage of the opportunities that present themselves. We are the limiting determinant to what we can achieve. 

Best regards - Al
Parent - - By MBSims (****) Date 04-19-2012 17:12
I really don't agree with your assessment that the code is more concerned with dollars. The purpose of most codes is standardization and safety, and to be practical to the extent possible. In the case of using a carbon steel test coupon to qualify a welder to use high alloy fillers, this is actually a more difficult test for the welder than a similar metal weld and there most certainly is a difference in weldability.  Using a carbon steel coupon is a very good method of determining the welder's ability to make both similar and dissimilar metal welds using the high alloy fillers. I would suppose that the cost of test coupons or the desires of a contractor were certainly not the only factors that influenced the code committees to permit this practice.

As you suggest, any code is a "minimum" set of requirements and the designer/engineer is free to specify more restrictive requirements should it be necessary. To me, doing it the "right" way means to meet the code and provide a safe product that performs well in the intended service conditions. If the code permits the material substitution, and it results in a welder that has the ability to make sound welds, and it is not detrimental to the end product, then why is that not the "right" way?
Parent - By 803056 (*****) Date 04-19-2012 17:30
Point taken.

Al
Parent - - By js55 (*****) Date 04-20-2012 11:58
I was going to make a similar point to Marty's but since he did a far better job than I could I'll let it go. But I will add, that the majority of people sitting on ASME Section IX are not people representing contractor economics. Those that I can call friends I would not hesitate to say are people of high intergrity. And I will emphasize that safety is foremost in every discussion. If someone has data to the contrary that proves there is an issue, bring it. I can garantee economics will not be the rebuttal.
Parent - - By Shane Feder (****) Date 04-20-2012 13:47
Marty,
Agree totally that welding a s/s or nickel alloy wire on a c/s coupon is definitely harder than welding onto similar base metal.
However, I agree totally with Als post regarding economics - IMHO there is no other reason for allowing base metal substitution.

Had an O & G  client that air freighted a pallet full of 321 s/s x 40 mm thick plate coupons for welder qualification (approx AU$40,000).
16 mm c/s plate readily available on site would have been a perfectly suitable substitute,
Regards,
Shane
Parent - - By jon20013 (*****) Date 04-20-2012 23:19
Gents; I may have a slightly different (while supportive) comment on the matter.

Of course economics plays in to the allowable substitution and in this case I'd respectfully disagree that safety plays a primary role for PERFORMANCE qualifications.  The proposal to permit base metal substitution would not have stemmed from Committee, but rather from Industry (hence the economics side of things). 

Committee would then discuss the merits of "weldability" differences and similarities between the carbon family and the various alloys.  Not having researched the actually history of discussions at subcommitee level, I can only imagine both pro and con discussions going on for some time.  Ultimately, a consensus would have been reached that the allowed substitutions have similar weldability characteristics (with regard to the base metals involved).  I can also imagine some Committee Members mentioning that perhaps the filler metals may have more significant affect on the ability of a welder to deposit sound weld metal than that of the base metal on the weld properties.

I may be wrong in saying I don't believe Safety would be a primary consideration for PERFORMANCE qualification in discussing substitutes, albeit safety is always the primary concern for actual work there are other rules in place to cover the safety aspects such as requiring each manufacturer to qualify its own procedures even though literally millions of WPS' have been qualified on the various alloys throughout the years.
Parent - By 803056 (*****) Date 04-22-2012 15:27
After sitting on several committees over the years I recognize anything coming from a committee is not the work of a single individual. It is at best a compromise and sometimes resembles a whisper of what was initially proposed. And that boys and girls is how we got the camel.

Al
Up Topic Welding Industry / ASME Codes / metal substitution for welder qualification

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