P91 to P22 Tensile Test Question

[74tiger]

We recently welded a specimen for procedure qualification for a SA-335 P91 to SA-335 P22 procedure. The procedure was performed on 6" Sch. 160 pipe with ER90S-B3 root and E9018-B3. Sample was PWHT at 1350F for 2 hr. Ramps were between 500F and 600F above 600F. The Tensile specimens came back as breaking at 96KSI and 98KSI, ductile in base metal. The P22 was confirmed by composition. MTR showed that the original P22 pipe had 74ksi as Tensile. Bend test passed.

Any ideas as to how the P22 became a 96KSI material?

 

[davefitz]

I am not certain, but there is a variation in properties, and the nominal 74 ksi is likely the minimum accepted properties based on statistical testing ( at max values of trace elements) while the 96 ksi is the actual as-tested for your particular pipe. If the pipe was obtained from an exception mill (eg, Sumitomo ) the trace elements may be nil, and the process of extruding a pipe may strengthen / work harden the pipe in the axial direction.

"Whom the gods would destroy, they first make mad "

 

[metengr]

The P22 probably broke in the base metal HAZ region. Secondary hardening affects can result in increased strength properties.

 

[74tiger]

Thanks Metenger. This was a reduced section turned specimen. I did not see the specimen but after looking at the diagram and figuring the minimum size (A=~2.2" with a 1.1" weld) I can see this potentially being the case.

 

[weldstan]

I have often seen this with P22 after PWHT. See metengr's comments.

 

[Guest102023]

Physical constraint by thicker adjacent material is the major factor.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[metengr]

brimstoner
Point of gentle clarification, physical constraint will effect yield strength as you are well aware based on plane stress versus plane strain behavior of metals. Tensile strength is unaffected.