Q. What are Preheat and interpass temperature?

Preheat and interpass temperatures shall be in accordance with the applicable codes. Materials that require preheat for welding shall receive a comparable preheat for thermal gouging and cutting, and tack welding.

The minimum metal temperature for welding shall be 10°C (50°F).

The maximum interpass temperature for austenitic stainless steel shall be 177°C (350°F).

The metal temperature shall be maintained at preheat temperature until weld is completed. An insulation wrap shall be placed around the joint to facilitate slow cooling.

Temperature melting crayons (Tempil-stick or equal) or contact pyrometers shall be used to determine preheat and interpass temperature. Temperature determination will be taken on the opposite side of the heating source.