PWHT Calculator
Calculate post-weld heat treatment parameters per ASME and AWS requirements.
PWHT Temperature Ranges by P-Number
| P-No. | Material | Temp Range (C) |
|---|---|---|
| 1 | Carbon Steel | 593-649 |
| 4 | 1.25Cr-0.5Mo | 677-746 |
| 5A | 2.25Cr-1Mo | 677-746 |
| 5B | 5Cr-0.5Mo | 704-760 |
| 15E | 9Cr-1Mo-V | 732-788 |
Understanding PWHT
Soak Time Calculation
Per ASME Section VIII: Minimum 1 hour per 25mm (1 inch) of thickness, with a minimum of 15 minutes for any thickness.
Heating/Cooling Rate Formula
Max Rate (C/hr) = 5500 / thickness (mm), but not more than 220 C/hr and not less than 55 C/hr above 315 C.
Why PWHT is Required
- Residual Stress Relief: Reduces stresses from welding that can cause cracking
- Hydrogen Removal: Allows diffusible hydrogen to escape
- Hardness Reduction: Tempers hard HAZ microstructures
- Improved Toughness: Restores ductility in heat-affected zone
Critical Control Points
- Temperature Uniformity: Maximum variation of 83 C within heated band
- Thermocouple Placement: On thickest section of weld
- Insulation: Required to control gradients