Hardness profile

The distribution of hardness values across a defined cross-section, such as from the weld metal through the heat-affected zone to the base material. It reveals microstructural changes and local softening or hardening.

If you grind the weld crosswise and etch it, you can see the heat-affected zone. There you can use a hardness tester to take a point-by-point profile – from the base material through the HAZ into the weld. If the zone is too hard, the cooling was too fast and brittle structure can form that tends to crack. If it is softer than the base material, you have 'annealed' the joint by too much heat and it loses strength. The profile shows you immediately whether you are right with preheating, interpass temperature, or heat input.

MetallurgieSchweißtechnik