F. T. Hoffmann, T. Lübben, F. Frerichs, J. Rath, H. W. Zoch, Stiftung Institut für Werkstofftechnik (IWT), Bremen, Germany
Dimensionless numbers are widely used in engineering for generalized considerations. so, for example the Reynolds Number for characterizing flow conditions. In heat treatment using such numbers is not common. However, recent investigations in IWT Bremen showed, that dimensionless numbers can also be used to characterize heat treatment steps, especially quenching. E.g., it has been found, that the interdependence between quenching rate, dimensions of the parts and resulting residual stresses can be correlated with the Biot Number in a certain range. For the bearing steel SAE 52100 (100Cr6), it could be verified, that the BIOT–Number characterizes the resulting surface residual stresses and the distortion after a through hardening process. This dimensionless number is defined as Bi = α·L/λ. with the heat transfer coefficient α, the thermal conductivity λ and the volume to surface ratio L as the characteristic length. So it summarizes parameters from process, material and geometry.
The paper discusses the use of dimensionless numbers in heat treatment and gives examples found in the research work.
Summary: Dimensionless numbers are widely used in engineering for generalized considerations.In heat treatment using such numbers is not common. However, recent investigations in IWT Bremen showed, that dimensionless numbers can also be used to characterize heat treatment steps, especially quenching.The paper discusses the use of dimensionless numbers in heat treatment and gives examples found in the research work.
