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Heat-Affected Zone (HAZ)

The region of base metal adjacent to a weld bead that has been heated to a temperature high enough to change its microstructure and properties but not melted. The HAZ is susceptible to hardening, brittleness, and cracking, particularly in carbon steels. NDT inspection of the HAZ is critical to detect heat-affected zone cracks and assess weld quality. The HAZ width varies with material composition, heat input, and cooling rate.

Detailed Explanation

The region of base metal adjacent to a weld bead that has been heated to a temperature high enough to change its microstructure and properties but not melted. The HAZ is susceptible to hardening, brittleness, and cracking, particularly in carbon steels. NDT inspection of the HAZ is critical to detect heat-affected zone cracks and assess weld quality. The HAZ width varies with material composition, heat input, and cooling rate.

Best Practices

  • Always follow applicable NDT standards and procedures
  • Use properly calibrated and maintained equipment
  • Ensure personnel are properly trained and certified
  • Document inspection procedures and results completely
  • Keep current with industry standards and best practices
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