What is the area on each side of the weld that does not melt but is affected by heat called?

• A. Weld Zone
• B. Fusion Zone
• C. Heat affected zone (HAZ)
• D. Heat sink

Answer: (C)

The area heated by the welding process that does not melt is the Heat Affected Zone. This region lies on both sides of the weld, between the melted fusion zone and the untouched base metal. It experiences temperatures high enough to change the metal’s microstructure and properties, but not enough to melt. The changes depend on the material and cooling rate and can affect hardness, strength, and toughness. In contrast, the fusion zone is the molten weld metal, and a heat sink refers to material or a feature that absorbs heat.