What is hardness testing in welds, and when is it typically performed?

What is hardness testing in welds, and when is it typically performed?

• A. It measures electrical conductivity; during finishing.
• B. Hardness testing assesses local mechanical properties; performed for high-strength steels and PWHT.
• C. It measures chemical composition; never in welds.
• D. Hardness testing checks weld color consistency.

Answer: (B)

Hardness testing checks the resistance of a small area of the weld and surrounding heat-affected zone to indentation, which reflects local mechanical properties such as strength and toughness in that spot. This is important because the weld and HAZ can behave differently from the base metal, and service performance depends on those local properties. It’s especially common for high-strength steels and after post-weld heat treatment, since PWHT alters hardness and helps relieve stresses; codes often require hardness limits to ensure the weld remains tough enough and not overly brittle. This test isn’t about electrical conductivity, chemical makeup, or weld color—those are different checks, while hardness focuses on how the material locally resists deformation.

Hardness testing checks the resistance of a small area of the weld and surrounding heat-affected zone to indentation, which reflects local mechanical properties such as strength and toughness in that spot. This is important because the weld and HAZ can behave differently from the base metal, and service performance depends on those local properties. It’s especially common for high-strength steels and after post-weld heat treatment, since PWHT alters hardness and helps relieve stresses; codes often require hardness limits to ensure the weld remains tough enough and not overly brittle. This test isn’t about electrical conductivity, chemical makeup, or weld color—those are different checks, while hardness focuses on how the material locally resists deformation.