What is interpass temperature and what is a typical limit for many carbon steels?

• A. Interpass temperature is the temperature of the weld area between passes; a common limit is around 300–350°C (570–660°F).
• B. Interpass temperature is the ambient temperature of the workshop.
• C. Interpass temperature is the temperature of the welding rod.
• D. Interpass temperature is the maximum allowable room temperature.

Answer: (A)

Interpass temperature is the temperature of the weld area between successive passes. For many carbon steels, a common limit is around 300–350°C (570–660°F). Sticking to this range helps control the metallurgical changes that occur between passes, keeping the heat-affected zone from growing too large and reducing the risk of unwanted hardness or cracking from the thermal cycle. In practice, you’d monitor with a pyrometer or infrared thermometer and wait until the weld area cools to the target range before adding the next pass. If the interpass temperature gets too high, you can encourage coarser grains and potential cracking; if it’s kept too low, you may hinder proper fusion or promote brittle microstructures, so following a typical carbon steel limit supports reliable, sound welds.