Hardness Testing on Welded Joints
Hardness testing measures the resistance of a material to the penetration of a test body across the weld seam. It identifies unacceptable hardness increases that indicate a tendency for hardening.
Physical-Chemical Working Principle
The hardness test measures a material's resistance to the penetration of a standardized indenter. This is done by pressing the indenter onto the weld seam and measuring how deep it penetrates the metal.
Metallurgical Relevance & Welding Risks
Excessive hardness increases in the structure can lead to cracks and breakage. A weld seam that is too hard can also impair the material's mechanical properties, which can be dangerous especially in high-stress applications.
Workshop Practice & Instructions
The hardness test is carried out with a Brinell or Rockwell hardness tester. The indenter is pressed onto the weld seam and the depth of penetration is measured. For steel welds, the hardness of the seam should not exceed 1.2 to 1.5 times that of the base metal. If results are unacceptable, re-welding is necessary.