What is interpass temperature and why is it important in multi-pass welding?

• A. The minimum temperature between passes.
• B. Ambient temperature.
• C. The maximum temperature allowed between passes; controls microstructure, reduces cracking, and minimizes distortion.
• D. Preheat temperature.

Answer: (C)

Interpass temperature is the maximum temperature allowed between weld passes in a multi-pass weld. This limit is set to keep the material within a temperature range that preserves a good microstructure, reducing the likelihood of cracking and controlling distortion. If the weld area stays too hot between passes, grains can grow and the weld metal may become more brittle, increasing the risk of cracks and making distortion worse. By enforcing a maximum interpass temperature, you help ensure the next weld pass fuses properly and the overall joint retains toughness and dimensional stability. Ambient temperature and the preheat temperature are separate concepts, and the interpass limit is defined as a maximum, not a minimum.