Which condition indicates a part has cooled too quickly after being welded?

• A. Warping of the part
• B. Surface discoloration
• C. Increased ductility
• D. Cracking adjacent to the weld

Answer: (D)

Rapid cooling after welding can produce a brittle microstructure and leave high residual tensile stresses in the weld area. These conditions make cracks form and propagate near the weld, so cracking adjacent to the weld is a clear sign that the part cooled too quickly.

Warping results from heat input and restraint during cooling, not necessarily from excessive cooling speed. Surface discoloration reflects oxidation from heating, not the rate of cooling. Increased ductility would not be expected with overly rapid cooling; the metal tends to become harder and more brittle, not more ductile.