What factor is indicated by cracking adjacent to a weld?

Cracking adjacent to a weld can be primarily attributed to rapid cooling rates, making "too fast cooling after welding" the correct response. When welds cool too quickly, particularly in metals with high carbon content or those prone to hardening, they can develop residual stresses. These stresses arise from the rapid contraction of the metal as it cools, leading to thermal shock and, subsequently, cracking in the heat-affected zone. This phenomenon is often referred to as hydrogen-induced cracking or cracking due to stress, particularly in high-strength materials.

The factors related to overheating during welding, inadequate filler material, and improper welding technique can certainly contribute to issues in welding, but they are less directly linked to cracking adjacent to the weld. Overheating can lead to distortion or excessive grain growth, inadequate filler material can affect the strength and integrity of the weld, and improper welding technique might cause problems like incomplete fusion or penetration. However, the specific issue of cracking adjacent to a weld is most closely associated with the cooling rate, highlighting the importance of controlling the cooling process following welding operations.