What is the role of back-step technique in MIG welding to minimize heat buildup in a repair seam?

• A. Weld a small section opposite to previous weld to balance heat and reduce distortion
• B. Weld forward along the seam to increase speed
• C. Use a larger filler wire to dissipate heat
• D. Move the torch in a circular pattern around the weld

Answer: (A)

The main idea is balancing heat input along the repair seam. In MIG welding, heat builds where you weld, and if you keep pushing in the same direction, the metal on one side can overheat, causing distortion and a larger heat-affected zone. Using the back-step approach means welding a small section in the direction opposite to the last weld, then continuing forward again. This back-and-forth pattern distributes heat more evenly around the seam, giving the metal time to cool between passes and reducing residual stresses that cause warping.

This technique helps you control distortion while still progressing along the seam, especially on thin or shaped panels where excessive heat can be a problem. The other options don’t achieve that balanced heat distribution: welding forward keeps concentrating heat in one direction, using a larger filler wire increases total heat input rather than distributing it, and moving the torch in a circular pattern doesn’t create the even, alternating heat flow needed for a straight repair seam.