Columnar grains are typically observed in which region of a welded joint?

Columnar grains are typically observed in which region of a welded joint?

• A. In the weld metal
• B. In the base metal
• C. In the heat affected zone
• D. In the filler material

Answer: (A)

Columnar grains form during the solidification of the molten weld pool. As the weld metal cools, crystals nucleate at the fusion boundary and grow directionally toward the cooler surroundings, creating elongated grains that align with the heat flow. This directional solidification pattern is characteristic of the weld metal, since it is the region that melts and then re-solidifies. The base metal remains solid (except for any heat-affected-zone changes) and the filler material, when used, becomes part of the weld metal upon solidification, so the columnar structure is most typically observed there.

Columnar grains form during the solidification of the molten weld pool. As the weld metal cools, crystals nucleate at the fusion boundary and grow directionally toward the cooler surroundings, creating elongated grains that align with the heat flow. This directional solidification pattern is characteristic of the weld metal, since it is the region that melts and then re-solidifies. The base metal remains solid (except for any heat-affected-zone changes) and the filler material, when used, becomes part of the weld metal upon solidification, so the columnar structure is most typically observed there.