What practice helps mitigate cracking risk when welding carbon-containing steels with GMAW?

• A. Preheating is recommended to reduce cracking risk.
• B. Preheating is never used.
• C. Preheating increases cracking risk.
• D. Preheating is only for aluminum.

Answer: (B)

Mitigating cracking in carbon steels welded with GMAW relies on controlling the cooling rate through preheating. Preheating slows down the cooling of the weld and surrounding metal, giving hydrogen more time to diffuse out of the weld zone and heat-affected zone before hardening occurs. This reduces hydrogen-induced cracking and lowers residual tensile stresses by softening the HAZ during solidification. The result is a much lower cracking risk, especially for thicker sections or higher-carbon steels, when used in combination with proper low-hydrogen filler metal and good moisture control. It’s not correct to say preheating is never used, nor that it increases cracking risk, and aluminum is a different case with its own welding considerations.