PWHT Calculator

ASME UCS-56 caps the heating rate at 400°F/hr divided by thickness in inches, but also says the rate never needs to exceed 400°F/hr -- so for material 1 inch thick or thinner, 400 divided by thickness is already at or above 400, and the code's own ceiling takes over. Once thickness passes 1 inch, 400 divided by thickness drops below 400, and that smaller number becomes the actual limit -- for example, 1.5 inches gives roughly 267°F/hr, not the full 400.

UCS-56 also sets a floor: the rate need not be reduced below 100°F/hr even when 400 divided by thickness would suggest something slower. That floor kicks in at 4 inches for heating (400/4 = 100) and 5 inches for cooling (500/5 = 100) -- beyond those thicknesses, both Max Heating Rate and Max Cooling Rate stay pinned at 100°F/hr rather than continuing to fall.

No -- Max Heating Rate and Max Cooling Rate depend only on Material Thickness, since UCS-56's rate formula is purely a function of the thickest joint member. Hold Time per Inch changes Total Hold Time, and Hold Temperature Override changes Hold Temperature, but neither one moves the maximum heating or cooling rate the code allows for a given thickness.

Treat that default cautiously -- many austenitic stainless steels are actually exempt from mandatory PWHT under ASME Section VIII, and stress-relieving some grades in the wrong temperature range can cause sensitization (chromium carbide precipitation that lowers corrosion resistance) rather than helping. This calculator's stainless default reflects a generic stress-relief temperature, not a universal requirement -- confirm the actual need for and parameters of any stainless PWHT against your specific alloy and welding procedure specification.

UCS-56 only requires controlled cooling down to 800°F, after which air cooling is permitted, but this calculator's Total Cycle Time estimate extends the controlled-cooling assumption down to 600°F -- a more conservative, longer estimate than the code's bare minimum. Treat Total Cycle Time as a planning estimate that errs toward more furnace time, not the shortest cycle the code would technically allow.