Economically alloyed high-strength steel for use in mine equipment

The development of low-temperature, high-strength weldable steels for very heavy-duty mine vehicles and pit props is considered. Steels of strength classes S70/60 (σy ≥ 590 N/mm2) and S80/70 (σy ≥ 690 N/mm2) are based on alloying with Cr, Mn, and Si, without added Ni and Mo; wear-resistant steels of strength class S100 (σy ≥ 950 N/mm2) are based on alloying with Cr, Mn, and B, with a small content of Ni and Mo. The bainitic–martensitic or martensitic structure with small lath size obtained after quenching and tempering ensures strength, plasticity, and low-temperature strength of the steels. Microalloying reduces the austenite grain size in recrystallizing rolling (microalloying with V) and in heating of the steel before quenching (microalloying with V and Nb) and also ensures precipitation hardening on account of the precipitation of vanadium- and niobium-carbonitride nanoparticles. The new steels may be used to replace imports of high-strength weldable steels of the same strength classes.