Interpass temperature and limit: what is the proper description and typical limit for carbon steel when performing multiple passes?

• A. The temperature at which a second pass is started is the interpass temperature.
• B. The interpass temperature is the maximum temperature between passes to prevent cracking; commonly around 200°C (392°F) or per procedure.
• C. Interpass temperature is unrelated to weld integrity.
• D. Interpass temperature should always be kept at room temperature.

Answer: (D)

Interpass temperature is the temperature the weld area is allowed to reach between passes; it’s a control point that helps protect weld integrity during multi-pass welding. For carbon steel, you don’t keep the work at room temperature between passes; instead you wait for the area to cool to a specified maximum, which is intended to prevent cracking and hydrogen-related defects. A common limit is about 200°C (392°F), though the exact value should come from the welding procedure and material specification. If the weld area is hotter than this limit, you’d continue cooling or apply measures to bring it down before adding the next pass. This makes the description that interpass temperature is the maximum temperature between passes to prevent cracking the correct concept.