Solid Solution Hardening
Solid solution hardening increases the strength of steels by dissolving foreign atoms that create local stress fields and hinder dislocation movement. This prevents cracks and improves toughness.
Physical-chemical mechanism of action
Solid solution strengthening is a process in which foreign atoms are dissolved into the metal lattice. These atoms can be either substitutional (similar atomic size) or interstitial (different atomic size). They create local stress fields in the crystal lattice and hinder the movement of dislocations of the metal atoms, leading to increased strength.
Metallurgical relevance & risks during welding
With insufficient solid solution strengthening, the steel can be prone to cracking and hot cracking. This happens when dislocation movements are not sufficiently hindered and pore formation or stress buildup occurs. Excessive strengthening leads to steel that is too hard, impairing its toughness and formability.
Workshop practice & instructions
To ensure effective solid solution strengthening, it is important to keep the weld in a critical temperature range. This range varies by steel type and can be determined from the material data sheet. For example, for a steel with a martensitic structure, cooling should be done so that the t8/5 value is between 10 and 20 seconds. This ensures sufficient hardening without excessive hardness formation.