Fracture Toughness
Resistance of a material against the rapid propagation of a pre-existing crack under mechanical loading. It is a fundamental material property used to prevent catastrophic brittle fractures.
Fracture toughness simply means: how well does the material stop a crack before it breaks. In welding, this is important because the heat-affected zone and the weld have a different structure than the base material. If the toughness there is too low, the component can suddenly break under load without warning – you don't want that. To avoid this, use filler materials that match the base material and give good toughness in the weld structure. Ensure clean joint preparation and protect the weld pool well from contamination. Control the cooling – too fast cooling makes the structure hard and brittle, too slow can lead to overheating. When in doubt, ask the welding engineer what suits the application.