Thesis for the degree of Doctor of Engineering in specialty 05.16.04 "Foundry".- National Metallurgical Academy of Ukraine Ministry of Education of Ukraine, Dnieper, 2020.
The dissertation is devoted to solving the scientific and technical problem of directional solidification of massive castings from Fe-C alloys, determining the effect of the combined mold-sand mold on the kinetics of volume shrinkage, and establishing the duration of electric arc-electroslag heating arrived at different stages of the formation of the solid phase in rolling rolls and ingots. It is proposed to heat the rolling rolls in a stepwise mode with a high power consumption in the first stage, which corresponds to the hardening of the liquid-solid phase of the roll barrel and is accompanied by the maximum melt shrinkage from profit, and less during the neck hardening stage. The influence of the combined mold-and-sand casting mold on the conditions for the formation of shrinkage defects in the barrel and the necks of the rolling rolls is established, and measures have been developed for directional solidification of castings.
The duration of reaching the pouring fronts, liquids and solidus of the center of castings with a carbon content of 0.04 ... 4.83%, having the form of a plate, cylinder and ball, was established. Graphoanalytical dependences are derived for calculating the duration of solidification of liquid-solid and solid-liquid zones in castings from Fe-C alloys. The zones with the minimum and maximum duration of the alloy in the solid-liquid state during the solidification of the central (axial) part of the casting were established, which allows predicting the zones with the minimum and maximum shrinkage porosity.
For complex complex alloyed and modified alloys with non-standard temperature-time casting modes, in which there is no data on volume shrinkage and solidification duration, profit heating modes are established according to the kinetics of melt transfer to casting: in the absence of electrode movement, heating is stopped.
A hypothesis is proposed for the process of accelerated hardening of the central zones of castings of flat, cylindrical and spherical shape by a heterogeneous mechanism, in which the branches of dendrites are additional centers of crystallization. In order to reduce the amount of cementite and the transcrystallinity of the structure in the axial zone of cast iron rolls, the time and amount of a graphitizing modifier are established, which are introduced into the liquid core after the working layer has hardened to a predetermined thickness.
The results of experimental and theoretical studies were introduced in the valtsivarny workshop of SC "DZPV" and in the educational process NMetAU.
Key words: mill roll, ingot, profit, solidification, shrinkage, electric-electroslag burned, shrinkage defects
