What is the purpose of controlling interpass temperature?

• A. Increase deposition rate
• B. Prevent cracking and ensure proper microstructure
• C. Prevent moisture absorption
• D. Change weld color

Answer: (B)

Controlling interpass temperature sets the heat the joint experiences between weld passes, which shapes the cooling rate of each pass and the resulting metallurgical structure. By keeping this temperature within the specified range, you prevent the formation of undesirable microstructures in the weld metal and heat-affected zone, such as coarse grains or brittle phases, which can make the weld more prone to cracking. It also allows hydrogen to diffuse out between passes, reducing the risk of hydrogen-assisted cracking in restrained joints. So, the main purpose is to prevent cracking and ensure the weld develops the proper microstructure, rather than affecting deposition rate, moisture absorption, or cosmetic color.