ASME QW-423.1 unassigned metals

[weldgal]

ASME QW-423.1 permits welder qualifications to extend to unassigned base metals of similar chemical composition to base metals that have P-numbers. Does anyone have any experience in how "similar" a base metal's chemical composition has to be?

 

[metengr]

weldgal;
The easy answer to this question is obtain the following publication from AWS

AWS B2.1 2009 Specification for Welding Procedure and Performance Qualification. There is a list of M-No's for a wide range of material specifications. Very useful for non-ASME materials.

 

[weldgal]

Good suggestion, but this particular material is a NiCr (ASTM B670) and is not listed in B2.1. Do you have any personal experience in how to "similar" the chemical composition has to be in order for me to be able to consider it "similar" to an assigned metal?

 

[metengr]

Go to the web site below and download the spec sheet on Inconel 718 for background information;

http://www.specialmetals.com/products/inconelalloy718.php

Also, why do you need to have a P-No designation for this material? It is not code approved for pressure boundary application (it is for bolting), so you can qualify a WPS using the trade name for base material designation or qualify as ASTM B 670 UNS N07718.

 

[weldgal]

I qualified a WPS for it, but would like to be able to use existing welders if I can define "similar" to know if welders who are qualified to P-4x materials can work on the job (within all required essential variables of course), since QW-423.1 permits that.

 

[metengr]

What filler metal did you use to qualify the procedure? Whatever process and filler metal the welder used to qualify the procedure would qualify them, as well. For other welders, if it were me, I would have them qualify on this material using the filler metal and WPS and RT the coupons. This is not your typical metal and I would be sure the welders can handle it.

 

[weldgal]

Like you, metengr, I was leaning towards qualifying additional welders, and may still opt to do so if necessary, but my primary goal with this post is to learn how ASME defines "similar" as it is used in QW-423.1 because I have been unable to locate any interpretations or personal experience with that particular issue.

 

[metengr]

weldgal;
The AWS document I described above captures the essence of assigning material group numbers, see below

Table D.2 groups base metals for welding procedure and performance qualification on the basis of mechanical
properties, chemical composition, and metallurgical
compatibility to minimize the number of welding qualificationnwhere this can logically be done.

I can't think of a better explanation. If you do not understand the above, you need to consult with a welding or materials engineer.

 

[weldgal]

Thank you metengr for your time, and I'm sorry that I have been unable to present my question in a clearer way, but in this unique situation was hoping to learn of someone's personal experience with sucess (or failure) in presenting an unassigned material as "similar" to an assigned material; specifically regarding how similar properties need to be (or how far they can vary) and still be considered similar as QW-423.1 uses the term. I'll consider this post closed.

 

[metengr]

weldgal;
No problem. I actually did understand your question. I was trying to find an explanation from reference material. I have treated unassigned material similar to a P-No material based on what I felt were composition and mechanical properties being as close to the material with an actual P-No. The problem is you need to know the material properties and how it responds to welding it decide if it should be treated similar to a P-No. This is a subjective call and should be done by a materials or welding engineer. Bye.