What is stimulated PWHT & step cooling tests? Can anybody provide information reg this? 1.25 Cr & 2.25 Cr requires this test. What is their importance?

Hi,

The step cooling test simulate the temper embrittlement of 2¼Cr-1Mo or 3Cr-1Mo Steels.

Temper embrittlement typically occurs at service temperatures between 450-600 °C. The rate and degree of development of temper embrittlement depend on the temperature and time of holding steel within this dangerous temperature interval. In this temperature range Segregation of P, As, Sb and Sn occurs in the grain boundary region. This leads to an upward shift of the ductile-to-brittle transition temperature after long time exposure.

In order to reduce the temper embrittlement the composition of the base metal has to control by the J-factor (Watanabe) and the weld metal by the X-Factor (Bruscato).

For more details concerning the step cooling test, J-factor and X-factor please see SA-387, SA-542 or SA-832, supplementary requirements S62 and S63 and in addition API 934.

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Kind regards,
Juergen Fleischfresser

Another good guide is EN 1101-1, EN 1101-2, and AWD D10.10