Step Cooling Test of heavy thickness Cr/Mo Steels

R.Eng · Dec 8, 2020

Hi,
Consider the fabrication code as ASME SEC. VIII Div. 1 & 2 and API RP 934
and Material as SA387 Gr.11 & 22

Is there any references to consider the step cooling test necessary, for the acceptance of thick plates(such as 60 mm and higher) regardless of J-Factor or X-Bar?

According to the fact that in thick plates for reactors the critical crack length is less than thickness and in low toughness values the leak before failure is unlikely to occur.

Dec 9, 2020

I have a small library of references on this but it inaccessible at the moment (too much data on too many PCs and drives).
Try googling; Arcelor Mittal may have something on the subject. TWI has something here. One of the factors you mention is for base metal and the other is for weld metal; the tramp elements included in the formulae differ also.
Whether step cooling, part of an accelerated heat treatment scheme for revealing susceptibility to TE, is required will be specified by the owner.
In reactor PVs made of Cr-Mo steels where there is potential for temper embrittlement, my personal preference for critical crack length would be zero. But that's just my preference.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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Step Cooling Test of heavy thickness Cr/Mo Steels

R.Eng

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