Consumables not tested in the PWHT condition

[Jdebeer]

When qualifying a WPS to ASME IX, for example using E7018-1 on P1 and giving the weld a PWHT for a cold service application. My understanding is that the classification E7018-1 will then be qualified to do this weld as per WPS with a PWHT. My problem is when purchasing new consumables to ASME II C (AWS 5.1-91), consumables is tested in the as welded condition by the manufacturer. We know that there will be a loss of mechanical properties during PWHT, thus consumables close to the minimum values might dip below during PWHT. What need to be done to prevent this? Extreme measures like asking the manufacture to test the electrodes in the PWHT’ed condition for both the minimum and maximum times and temperatures possible, for every lot produced, have been proposed. Is this necessary? How does the codes allow for this possibility?

Thank you

 

[deanc]

Don't make it more difficult. Per SecIX---
see QW-100.1,QW200.2(c),QW-404,QW-430

Did you qualify P-1,7018 with PWHT? If so,all 7018 qualifies. Check your varibles in SecIX. Check the construction code. There may be other eng. concerns-but not code reqs.

 

[Jdebeer]

Yes we have used E7018-1 on P1 base metal with a PWHT, thus all other E7018-1 qualifies. However I would like to know how the concern is addressed that if E7018-1 is very close to the minimum mechanical properties it might fall below during PWHT, because of the scatter of properties obtained within a classification. We work in a maintenance environment and cannot realistically use production test plates for heat treatment and impacts. Up to now we thought the PQR was sufficient.

 

[metengr]

deanc is correct - don't make it more complicated. We have qualified many welding procedures with PWHT on carbon steel base material, and I have never dealt with a question or problem related to mechanical properties of an E7018 weldment falling below the mechanical properties of the plate, if I understand your question. The weld metal properties must be equal to or exceed the properties of the base material, as verified with the PQR.

The PWHT affects the base metal mechanical properties more so than the weld deposit mechanical properties for E7018. As such, the real concern regarding PWHT is a loss in base metal strength or toughness as a result of PWHT. The weld metal will have higher strength than the base metal after PWHT. Toughness of the weld metal is a separate issue.

 

[GRoberts]

Try ESAB 7018-SR, or another manufacturers 7018 that is designed to maintain strength after stress relief. We have used ESAB 7018-SR with good results before, and even though thier catalog does not mention it, they did classify it as 7018-1 for us. (as opposed to just 7018)