Dear All,

I have one query regarding welding procedure qualification of cladded base metal. Our first base metal is Stainless steel 347 to weld with second base metal P5A cladded with Stainless steel 347. A layer of ENiCrMo-3 was buttered on bevel preparation of second base metal by other. I don't know why and for what reason. The problem is how to qualify the welding procedure on stainless steel 347 to P5A cladded with Stainless steel 347. Is it i need to qualify overlay procedure of P5A cladded with Stainless steel 347 or procedure of Stainless steel 347 to inconel ENiCrMo-3 or procedure of Stainless steel 347 to Stainless steel 347. I really need your advice and expertise. What is the best practice or code requirement on procedure qualification of cladded base metal. Advance thank for your kind cooperation and really appreciated
Regards
Tong2je

First let me clear what I have understood from your question.

First base metal is type -347 SS
Second base metal is type-347SS cladded over P5A and at joint i.e. on bowel cladded with inconel
.
You are joining the above two material. If I understood is correct following are the information to you.

The meaning of buttering is deposition of similar material over one base material. Purpose for buttering is to avoid repair works on base material after any welding or precisely to say not to introduce any discontinuities in base material because of welding. Even if any repair occurs due to welding, it is expected only within buttering and hence buttering thickness is designed so.

The meaning of cladding is deposition of different material over one base material. Purpose of cladding is mainly for corrosion resistance and to have a better welding compatability to another material.

So as per the above, deposition of type-347 over P5A and deposition of Inconel over P5A both are considered as cladding only.

For each cladding over P5A separate qualification procedure is required. Please refer QW214, QW250, Tables for special process essential variables with respect to welding process and QW453

From the above it is clear that when process, A-number changes, the procedure shall be qualified. For cladding procedure qualification and testing refer QW-453.

Also a separate procedure qualification shall be established for the joint of your above said first and second base metal. Refer QW217.

In my opinion one more separate procedure qualification shall be established for the junction cladding of SS Type 347 and Inconel over P5A.

I hope I have answered your question. I also request the experts to comment on this.

T.S.KANNAN
INDIA

First: Some technical aspects regardless to the code:
1) I assume the code of construction is ASME VIII/1 and therefore PWHT for P5A materials is required acc to UCS-56 at minimum holding temperature of 675 °C.
But stress relieving may only be carried out on austenitic or austenitic-ferritic welding consumables in austenite-ferrite joints at temperatures up to max. 300 °C. In consequence of higher temperatures a Cr-carbide zone arises in the transition zone of the weld deposit and leads to a dangerously reducing the strength of the joint. Naturally higher (service) temperatures should not occur during use. This is the reason that a layer of ENiCrMo-3 was buttered on bevel preparation of the P5A base metal by other.

2) I assume after cladding of the first layer with an overalloyed filler metal (e.g. AISI 307 or AISI 308) and buttering of the groove face as mentioned above a PWHT of the hole portion was performed. After this PWHT a cladding with AISI 347 was carry out. An additional PWHT is not required because of the austenitic filler metal of the first cladding layer ( P-No. 8 ). In addition if you joint this buttering bevel to the austenitic base metal a PWHT is not required and therefore the cladding of AISI 347 will be not affected (sensitized).

3) Please be aware welding of this Ni-base-buttering to the AISI 347 (austenitic steel) has to carry out with Ni-base filler metal only. The use of austenitic filler metal for this butt welding is not possible. If this the seam is filled up with an austenitic or austenitic-ferritic welding material, a ferrite-free, fully austenitic zone with a high hot cracking tendency would arise in the transition zone due to Ni-absorption from the Ni-based alloy of the buttering bevel.


Second: Code requirements from my point of view.
As mentioned above welding of the whole seam has to perform with Ni-base filler metal only. Therefore there is no cladding by your company.
For this reason QW-283 is applicable only. QW-283.4 reflects your situation: This paragraph is self-explanatory. The way of your Procedure Qualification depends on the buttering thickness.

I think my opinion is supported by the ASME IX definition (see QW-492) of "buttering" versus "corrosion-resistant weld metal overlay" (cladding):

_________________
Kind regards,
Juergen Fleischfresser

Thank you guys for your detail and valuable explanations.