Preheat & Interpass Temperature Log Sheet (Printable PDF)

Preheat temperature refers to the minimum base metal temperature immediately prior to welding initiation, applied to reduce thermal gradient, slow cooling rates, and minimize hydrogen diffusion—critical for high-strength or thick-section steels common in structural farm equipment such as loader booms, axle housings, and hitch assemblies. Interpass temperature is the maximum allowable temperature of the weldment between successive passes; exceeding it can cause grain coarsening, reduced toughness, or distortion, while falling below minimums risks embrittlement or cold cracking. The log sheet enforces traceability by capturing time-stamped measurements (typically via calibrated contact pyrometers or infrared thermometers), operator identification, joint location, WPS reference, and inspector verification. It integrates into broader quality management systems (e.g., ISO 9001) and is essential during Procedure Qualification Records (PQR) validation—where documented thermal history proves repeatability and conformance under real-world field conditions. In farm equipment repair contexts, environmental variability (e.g., outdoor ambient temperatures, rapid cooldown in wind/rain) makes rigorous logging especially vital for liability mitigation and warranty compliance.