Investigation of plastic properties of Hotvar steel during martensitic transformation

Abstract

This articlepresents the investigation of transformation plasticity (especially highpermanent plasticity) of Uddeholm Hotvar steel (C = 0.55 %, Cr = 2.60 %,Mo = 2.30 %, V = 0.90 %, Si = 1.0 %,Mn = 0.80 %) that has high wear resistance and resistance tothermal fatigue. The steel investigated is used for hot working tools, i. e.,dies, punches and other parts for deforming. The tests were exercised duringmartensitic transformation of steel. For theinvestigation of steel transformation plasticity the specimens were austenizedat 1050 °C, 1070 °C and 1090 °C for air quenching. The loadgenerated 100 MPa stresses (≤ 10 %×(RP0.2) of material at the temperature of thetest) was applied on the specimens cooled at bending device at 550-530 °C temperature.Plastic deflection was observed through all cooling process till roomtemperature and was measured in 0.01 mm accuracy. It was obtained for 5-7times greater after cooling from ~220 °C to ~30 °C than elasticdeflection attained at 550-530 °C temperature. That is a phenomenon oftransformation plasticity.

DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5717