Where are columnar grains found?

Where are columnar grains found?

• 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 molten weld metal as it cools under a strong temperature gradient from the fusion boundary into the weld pool. This directional solidification produces elongated, column-like crystals that characterize the weld metal region. The base metal isn’t melted, so its grain structure doesn’t undergo this solidification process, and the heat-affected zone, while heated, doesn’t experience melting-driven solidification, so it doesn’t develop columnar grains either. The filler material, when used, becomes part of the weld metal after fusion, so the columnar grain structure is found in the weld metal.

Columnar grains form during the solidification of molten weld metal as it cools under a strong temperature gradient from the fusion boundary into the weld pool. This directional solidification produces elongated, column-like crystals that characterize the weld metal region. The base metal isn’t melted, so its grain structure doesn’t undergo this solidification process, and the heat-affected zone, while heated, doesn’t experience melting-driven solidification, so it doesn’t develop columnar grains either. The filler material, when used, becomes part of the weld metal after fusion, so the columnar grain structure is found in the weld metal.