Influence of Transformation Plasticity and Bending Stress on the Structure Evolution of Tempered Tool Steel

Abstract

The object of examination was tool steel with 1.42 % carbon content alloyed with chromium (about 12 %) and with
small amount of vanadium (0.70 %). This work deals with the investigation of tool steel structure evolution under affect
of changes of phase chemical composition, stresses, tempering temperature and transformation plasticity. The structure
of steel hardened from 1150 °C temperature tool was found consisting from retained austenite, martensite and carbide
phase. The specimens from hardened tool steel were bent at 520 °C tempering temperature. Bending stresses were
90 MPa, duration of tempering during bending varied – from 10 minutes to one hour to obtain different degree of steel
structure evolution. After tempering and bending for different duration, the specimens were analyzed with X-ray
diffraction method. The type of carbides, lattice parameters of the solid solution and carbide phase were determined.
XRD examination was performed in the compressed and stretched surfaces of the bent specimen. Different effect of
compression and tensile stresses on transformation plasticity of specimens, lattice parameters of steel structure phases
(solid solution and carbides) was determined during bending at tempering temperature.