API 577 Welding Inspection and Metallurgy 2025 – 400 Free Practice Questions to Pass the Exam

In carbon steels, the Heat Affected Zone (HAZ) consists of areas that experience thermal effects due to welding and other heat sources. This zone is characterized by temperature changes that can alter the microstructure and properties of the material. The HAZ typically includes regions that have been heated to temperatures exceeding approximately 1350°F.

At this temperature threshold, significant transformations can occur in the microstructure of carbon steels, such as the formation of pearlite and the potential onset of austenitization. These changes can impact the mechanical properties, hardness, and overall performance of the welded component. Understanding the parameters defining the HAZ, including temperature limits, is critical for welding engineers and inspectors, as they inform decisions related to pre-weld preparations, filler material selection, and post-weld heat treatment to mitigate potential issues such as brittleness or reduced ductility.

The other temperature options, while related to heat treatment processes, do not encompass the critical threshold defined for the HAZ in carbon steels.