Duplex Casting with unassigned P-number

[Erick21]

Hi,

We're using a PQR qualified with seamless pipe in duplex (S31803) : P10h-P10H. Our customer doesn't agree that we use this PQR to weld a pipe of duplex to a casting of the same grade (ASTM A890 gr 4A). The reason is that duplex casting has no P-number, so it should be separately qualified according asme IX.

If we follow strictely the code it is right. But, duplex casting has the same composition to forge or pipe duplex. Is there really a technical justification to have not assigne a P-number to duplex casting or is it just because AMSE is not an exhaustiv list and some judgment need to be taken.

thanks

Erick21

 

[metengr]

Your customer is correct. If you intend to qualify a procedure for an unlisted P-No base material, it must be the unlisted P-No base material. Simply qualify a new WPS using the unlisted P-No base material by grade. ASME Section IX provides rules for procedure qualification. Acceptance of base materials is based on the code book section that is applicable, and it is not an exhaustive list of materials.

 

[Erick21]

Thanks for your reply.

I agree with your statement, but is there a specific technical reason to have the duplex casting gr 4A unassigned whereas : pipe, fitting and forge are all P10H?

 

[metengr]

Yes, there is a technical reason. Product form can have an effect on weldability.

 

[jwhit]

Grade 4A is a legitimate P10H material, ASTM A890 lists grade CD3MN and 4A for this material. In the case of Duplex Stainless ASTM has changed the identifying means from the standard naming for stainless (C=Corrosion, D=Microstructure, 3=Carbon content etc.)to a number plus letter system. CD3MN is listed as P10H Gr. 1. Note that in this case ASME accepts the ASTM specification rather than shifting you to an SA890 spec. You're out of the woods on this one, if I recall correctly Gr. 5A is usually the biggest concern due to lack of P No. Hope this helps you out.

 

[weldtek]

Agreed. See QW 422.

 

[moseley]

The Duplex casting you are referencing is also identified by a UNS # (J92205). In accordance with ASME IX QW-420 (bottom left paragraph starts: "If an unlisted base metal...."). When this is used, and the UNS# is found within another "listed" material then this is and can be shown and welded as an P10H Grp. 1 material. I have over the years seen many Welding professionals overlook this out; I for one have been using this for years and when this paragraph is shown to the client they do not have a leg to stand on to reject a WPS/ PQR for not meeting ASME IX (Latest Edition). Hope this helps.

 

[metengr]

I agree with the above. However, casting specifications can be tweaked by vendors and this is where problems can develop from welding.

 

[moseley]

metengr,
I agree as well, Castings can be tricky beasts to overcome at times. Take for example CA6NM; this material has a mind of it's own! Only due to experience and many, many, trials and errors; I do now as a Company's Senior Welding Engineer actually qualify castings as their own entity due to the issues that can arise. Casting specifications are definately not friendly to Welding Procedures, nor is any casting exactly the same as the next.