asme ix

[joshsandith]

dear all.

can u help me.

I can't understand what is the definition of upper and lower transformation from asme ix, which code can I get this to verify if my PWHT is on upper transformation or lower, how can I determine.

thanks

 

[metengr]

It depends on the chemical composition of the material. For carbon and low alloy steel as you heat the steel the microstructure changes at the lower transformation temperature to mixed phases. The lower transformation temperature is different for different steels. As you continue to heat the steel, when the upper transformation temperature is reached, just one phase appears and this is called austenite.

ASME Section IX does not define what the temperatures should be it only gives guidance on when you exceed the lower and upper transformation temperatures what is required for procedure qualification because you altered the original mechanical properties of the steel.
You can find lower transformation temperatures in literature or using ASME B31.1 piping code. For upper transformation temperatures you need to either use literature or there are equations that can be used.

 

[stanweld]

ASME B31.1, Table 129.3.1 provides approximate lower critical temperatures for common alloys subject to PWHT.