Numerical and experimental investigation of the temperature field of a solidifying massive ductile-cast-iron roller

Abstract

The quality of the working rollers used for rolling rails of different profiles is determined by the chemical and structural composition of the material of the rollers and the production technology The requirements for the quality cannot be ensured without a perfect knowledge of the course of the solidification, the cooling and the heat treatment of the cast rollers as well as the kinetics of the temperature field of the casting and the mould. The solidification and cooling of the ductile-cast-iron roller in metal and non-metal moulds is a very complicated problem of heat and mass transfer with the phase and structural changes described by the Fourier equation. An original application of ANSYS simulated the forming of the temperature field of the entire system, comprising the casting, the mold and the ambient. The simulation of the release of the latent heats of the phase or structural changes is carried out by introducing the thermodynamic enthalpy function. In the experimental investigation of the temperature field, an original methodology for the measurement of the distribution of temperatures and heat flows in the roller-mould system had been developed and verified in operation. In the design of the original procedure, there were a number of problems connected with the large size of the roller and the mould, the uneven dimensional changes of the solidifying roller and the mould, the installation and the insulation of the thermocouples, the wiring of the thermocouple system, etc. The findings regarding the kinetics of the temperature field of the roller and the mould, obtained from experimental research, were used to determine the boundary conditions and for the verification of the numerical simulation program. The calculation of the temperature field focused on an analysis of the effect of the mould separator on the course of the solidification of the roller. The results of the mathematical modelling indicate that the distribution of the temperatures and the solidification in the vertical direction is significantly uneven – and this has an effect on the internal quality of the casting.