The article presents the results of scientific research and industrial experiments aimed at the development of technology to reduce the production cycle of high-strength hull steel. The technology includes an improved reduced heat treatment of ingots made using rare-earth metals and uphill teeming of large sheet ingots. The proposed technology for the preliminary heat treatment of ingots eliminates the high-temperature phase re- crystallization operation, which is unnecessary, according to the authors, since it does not allow partial crushing (grinding) of the metal dendritic structure and homogenization. When using the proposed technology of reduced pre- treatment, phase and structural stresses are sharply reduced. Experiments have shown that the modification of steel with rare-earth metals has a positive effect on the crystallization of ingots, changing the macro- and microstructure of alloy steel. The developed manufacturing technology of high-strength hull steel provides a high level of sheet quality and a reduction in the production cycle time by 10-12 %.
The paper investigated the bainitic steel of 10KHN3MFA grade, which is characterized by the increased tendency to display structural heredity in the forgings with large cross-sections. The samples have been studied for kinetics of diffusional transformation process both under continuous cooling and isothermal conditions, as well as its microstructure. It is determined that in the range of subcritical temperatures with cooling from 900 °C in the studied steel, the initial stage of separation of the ferrite phase takes place. It is shown for the first time that the diffusional ferrite-pearlite transformation fades. Previously it was believed that the beginning of transformation under isothermal conditions proceeds to the end. It was found out that the transformation begins immediately after the beginning of isothermal holding, without the generally accepted incubation period.
