How does interpass temperature influence distortion and weld quality?

• A. Controlling interpass temperature reduces thermal gradients and distortion; excessive interpass temperature can alter microstructure and reduce weld quality
• B. Interpass temperature has no effect on distortion
• C. Increasing interpass temp always improves weld quality
• D. Interpass temperature only affects color

Answer: (A)

Interpass temperature is the temperature of the weld area before adding the next pass. It affects how heat builds up and how the metal cools between passes. Keeping this temperature within a controlled range helps minimize differences in cooling rates between passes and the surrounding base metal, which reduces thermal gradients and lowers residual stresses. That reduction in thermal stress means less distortion and a more predictable weld geometry.

If interpass temperature gets too high, cooling is slower between passes, and the heat-affected zone and weld metal can undergo undesirable changes in microstructure, such as grain growth or phase changes. These changes can weaken the weld or make it more prone to cracking, lowering overall weld quality.

So, controlling interpass temperature lowers distortion and helps preserve a sound microstructure, while excessive interpass temperature can degrade weld quality. Interpass temperature does matter for distortion and quality, not just appearance or color.