According to UG-79 Heat Treatment is required for cold forming heads when:
A - Extreme Fiber Elongation is more than 40%
B- Fiber elongation is more than 5% and any of the following condition exist:
- Impact Test is not exempted according to UCS-66
- Heads for lethal service vessel as restricted in UW-2
- Head plate thickness before forming is 16 mm
- Thickness reduction at any location after forming is more than 10% of actual thickness where extreme fiber elongation is more than 5%
- Forming Temperature between 120-480 deg. C
You may calculate fiber elongation from formula given in Table UG-79.1 or better to consult with pressure vessel designer for this calculation.
(Heat Treatment when applicable will perform by following UCS-56 requirements)
Hot Formed heads in no case does not require heat treatment after forming.