Thesis for the degree of Candidate of Technical Sciences (Ph.D.) in specialty 05.16.04 – Foundry. National Metallurgical Academy of Ukraine of the Ministry of Education and Science of Ukraine, Dnipro, 2020. The dissertation is devoted to theoretical and technological generalizations within the solution of scientific and technical problem of reduction of residual stresses in a barrel of rolling mill rolls with a diameter of 300 ... 500 mm to a level which can be compared with size of residual stresses in heat-treated rolls, by establishing regularities of complex influence of structural, dimensional parameters of the combined mold used to make these rolls, the amount of residual stresses in their barrel. As a result of theoretical and experimental research in the field of rolling mill casting technology, new scientific solutions have been found and new practical results have been obtained. The quantitative complex influence of the phase composition and thickness of the bleached working layer of cast iron in the barrels of rolling rolls on the value of residual stresses due to the decrease in temperature difference between the center and the surface of the roll barrel, which is achieved by controlled external heat dissipation. For cast iron rolling mills produced in combined and combined shielded molds, the patterns of influence of the diameter of the barrel in the range from 300 to 500 mm, the lower neck in the range from 100 to 300 mm and the diameter of the mold in the range from 500 to 700 mm, and the values of the coefficients of heat storage capacity of their materials on the nature of the sequence of hardening of cast iron in the form. Formalized ratios of the cooling duration of the elements of the cast iron roll with a barrel diameter in the range from 200 to 800 mm at a ratio of the wall thickness of the mold to the diameter of its barrel from 0.27 to 1.00 using external shielding of its combined form. An increase in the ability to remove residual stresses during annealing when modifying the melt of pre-eutectic cast iron in a ladle with a mechanical mixture of a complex modifier based on rare earth elements and gadolinium concentrate in a ratio of 10: 1 at a flow rate of 0.54 ... 0.77 wt. According to the results of research, the technology of shielding molds of cast iron rolls SPHN-60 was developed, which reduces the level of residual stresses in the cast roll to the level of heat-treated roll and prevents the formation of shrinkage shell in the lower neck of the roll and its barrel. The developed parametric criteria allow at the stage of designing the mold for rolling rolls with a barrel diameter of 300 to 500 mm to predict the probability of shrinkage in the lower neck of the roll. The developed modifiers allow to increase mechanical properties of rolled pig-iron and to reduce the size of residual stresses in 1,56 ... 1,76 times in relation to size of reduction of residual stresses which is provided by thermal processing of rolls. The theory of hardening of castings in the part of efficiency of management of hardening of pig-iron castings which are made in the combined foundry forms received the further development. Keywords: cast iron, roll, combined form, shielding, residual stresses, heat treatment, modifier, property, strength, microstructure, adaptation.
