What is a practical interpass temperature guideline for plain carbon steel?

• A. 200–250°C
• B. 100–150°C
• C. 300–350°C
• D. 400–450°C

Answer: (A)

Controlling the temperature at which each new welding pass is added helps manage the cooling rate and the weld’s microstructure, reducing cracking tendencies and keeping the weld solid and dependable. For plain carbon steel, a practical interpass temperature of about 200–250°C gives a good balance: it stays warm enough to prevent too-rapid cooling between passes, which helps with bead fusion and reduces stress buildup, but it’s not so hot that it would overheat the heat-affected zone, promote excessive grain growth, or cause distortion. Cooler interpasses (around 100–150°C) can make welding harder and may increase the risk of cold cracking in some setups, while hotter interpasses (300–350°C or 400–450°C) push the material into excessive heat input, risking structural changes and greater distortion.