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Anonymous Poster #1

Welding SA 335 Gr. P91 Pipe with Tunsten Containing Filler Metal Corresponding to Grade SA 335 P92.

12/22/2019 3:51 AM

Dear Sir,

Our welder inadvertently used tungsten containing filler metal corresponding to grade SA 335 Gr. P92 for welding of SA 335 Gr. P91 Pipes.

We are in a fix on what to do now ? Whether to cut the joint & re-weld using filler metal corresponding to Gr. P91 or to accept the joint with P92 filler as it is & proceed for PWHT & further processing. Different people are suggesting differently.

Our worry is that these being high temperature materials, how will this behave metallurgically during service at high temperatures ???

Kindly advice. Thanks in advance.

DDN VERMA.

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#1

Re: Welding SA 335 Gr. P91 Pipe with Tunsten containing filler metal corresponding to grade SA 335 P92.

12/22/2019 4:54 AM

P92 has less carbon and Molybdenum then P91

"When added to steel and cast irons, molybdenum enhances strength, hardenability, weldability, toughness, elevated temperature strength, and corrosion resistance. In nickel-base alloys, it improves resistance to both corrosion and high-temperature creep deformation."

So to meet spec I would cut the welds out and re-do...

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#2

Re: Welding SA 335 Gr. P91 Pipe with Tunsten Containing Filler Metal Corresponding to Grade SA 335 P92.

12/22/2019 12:31 PM

See #1 above.

Will you ask the customer to allow this deviation, or fix the problem yourselves?

See #1 above.

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#3

Re: Welding SA 335 Gr. P91 Pipe with Tunsten Containing Filler Metal Corresponding to Grade SA 335 P92.

12/22/2019 11:53 PM

When in doubt, cut it out.

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#4

Re: Welding SA 335 Gr. P91 Pipe with Tunsten Containing Filler Metal Corresponding to Grade SA 335 P92.

12/24/2019 2:24 PM

Why <...in a fix...>?

It’s wrong. Do it again. Properly this time.

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#5

Re: Welding SA 335 Gr. P91 Pipe with Tunsten Containing Filler Metal Corresponding to Grade SA 335 P92.

12/26/2019 4:07 AM

"Typically, the best low alloy flux-cored wire for welding P91 and P92 chrome-moly is an AWS E91T1-B9. This type of wire offers a fast-freezing slag for out-of-position welding, along with low diffusible hydrogen levels to control cracking. It also has a very high tensile strength: approximately 126,000 psi. Not surprisingly, because P91 and P92 chrome-moly pipe are used for higher temperature services than the other grades, E91T1-B9 flux-cored wire creates X-Ray quality welds, which are essential on such critical piping applications."

Prepare and qualify a new WPS and support it with its corresponding PQR using the parameters you mention. According to ASME IX.

I don't think you have a problem.

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#6
In reply to #5

Re: Welding SA 335 Gr. P91 Pipe with Tunsten Containing Filler Metal Corresponding to Grade SA 335 P92.

12/26/2019 5:23 AM

SMAW

"P91 (9% Cr – 1% Mo or P92 (9% Cr – 2%W – ½% Mo, V) pipe, choose a SMAW electrode formulated to improve creep resistance. Creep is any deformity (buckling, warping, etc) caused by stress and/or heat during the welding process, and higher strength chrome-moly is prone to this occurrence. AWS E8018-B8 H4R, E8018-B8L H4R or E9018-B9 SMAW electrodes can help provide that protection and are good choices for petrochemical or petroleum pipes or other surface applications exceeding service temperatures of 300 F (149 C). They yield tensile strengths between 100,000 and 110,000 psi."

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