Case-hardening steel
Application Area
Bolts, shafts, gears, etc., with a hard surface and a tough core.
Description
Case-hardening steels have a carbon content of less than 0.25% and a small amount of alloying elements, which promote through-hardening (Cr, Mn, Ni, Mo) and form hard carbides (Cr, Mo) with the introduced carbon in the surface layer, increasing wear resistance.
Properties
Excellent combination of toughness, high wear resistance, and resistance to bending and impact loads. Very good fatigue strength due to compressive stresses in the hardened surface. Very good fatigue strength due to compressive stresses in the hardened surface.
Welding:Not weldable (C15 is very well weldable before case-hardening).
Distortion:Particularly in unalloyed steels (water hardening) and/or complex-shaped parts.
Post-processing: Grinding of certain functional areas reduces negative effects (e.g., radial runout), improves tolerances, and refines surface roughness.
Case Hardening
Tough components are achieved by using low-carbon steels, which attain only low hardness when quenched. Therefore, carbon is introduced into the surface layer through diffusion, creating a hardenable steel layer with approximately 0.8% carbon.
During quenching, the core is tempered, and the surface layer is hardened. The case-hardening process consists of two main steps, Carburizing (introducing carbon into the surface) and Hardening (quenching and tempering).