A325 Bolts, Allowables at 600 F

[sweetal1]

Do the ASD allowables for A325 bolts need to be reduced for service at 600 F? What reference indicated the temperature dependent mechanical properties/allowables for A325?

 

[metengr]

This is an interesting question. From my background with ASME B&PV Code materials and determination of allowable stress values, there is a change in yield strength of materials as a function of service temperature. In simple terms, the allowable stress values used in boiler/pressure vessel design are established using tensile strength/3.5 (at service temperature) and yield strength * 2/3 (at service temperature)- whichever is the lesser of the two values is selected as the allowable stress for a given temperature, assuming NO time dependent effects on properties (which for most carbon steels is about 650 deg F).

Now, for bolting material the ASD (allowable stress design) values are probably based on yield strength/FS. For service temperatures where the yield strength decreases, I would expect that this has to be factored into the ASD value.