Impact test and hardness test in the same PQR?

[Hansac]

Hi all.

Last week I came across a PQR which has both impact test and hardness test conducted in one PQR. I find that rather odd. Impact tests are for cold service, and thus you'd think that the weldment or material itself will need to be ductile (thus no point in taking hardness test). Hardness tests are for brittle material, in that you want to control the hardness post-weld.

Was the PQR "odd" (read: WRONG), or do I need to tweak my understanding a little bit?

Knowledge-enhancing replies, tips, pointers, sarcastic information, are much appreciated,

 

[metengr]

No, this is not odd at all. Hardness testing can be performed as part of the PQR to verify adequacy of PWHT, if applicable, OR if a temper bead procedure qualification was performed OR as part of an engineering specification to ensure a maximum hardness is met for corrosive service.

 

[stanweld]

Hardness tests for procedure qualification are often specified in Engineering and Owners' specifications, especially in the petrochemical industry primarily, to (hopefully) ensure freedom from in-service stress corrosion cracking.

 

[Guest102023]

No conflict whatsoever.

Your first misconception is confusing 'ductility' with 'low-temperature toughness'. They are related but not the same.

The second is thinking 'Hardness tests are for brittle material'. Most often with ferritic steels hardness tests are used to measure the weld and heat-affected zone hardness. There are various reasons to limit hardness, although it is a rather crude indicator of some other properties.

 

[DVWE]

Not at all uncommon in the pressure vessel world. As stated, hardness tests verify effectiveness of PWHT when required, and impact testing is usually a requirement of ASME to verify the ductility of the material at it's minimum allowed pressurizing temperature.