R&D Park at Uzbekistan Technological Metals Complex JSC (Chirchik, Uzbekistan)

A. A. Zhumaev, PhD, Associate Prof., Head of Laboratory for Hard Alloys Research, ahmadjon_jumaev@mail.ru

Navoi State Mining and Technological University (Navoi, Uzbekistan)
Kh. A. Rakhmatov, Doctoral Candidate, Dept. of Railway Cars and Rolling Stock Facilities, x.raxmatov90@gmail.com

Tashkent State Transport University (Tashkent, Uzbekistan)
N. N. Khamroev, PhD, Acting Associate Prof., nurbekk_khamroev@mail.ru
Kh. Kh. Ashurov, PhD, Acting Associate Prof., k.khisrav1994@mail.ru

The article presents the results of a comprehensive analysis of methods for modifying the microstructure of steels based on their rare-earth metal (REM) content. The study is motivated by the need for a scientifically grounded approach to incorporating the Republic of Uzbekistan’s REM reserves into industrial production, thereby increasing the value-added potential of the metallurgical sector. The thermodynamic and kinetic aspects of the interaction between REMs and oxygen, sulfur, and nitrogen within a molten metal are examined, as is the role of REMs in deoxidation, desulfurization, and the modification of non-metallic inclusions. It is demonstrated that alloying steels with REMs significantly alters the mechanisms of crystallization and phase transformation within the Fe–C system (at carbon concentrations of up to 2.14 wt. %). This process facilitates the refinement of austenite grains, the formation of dispersed, complex-composition inclusions, and the stabilization of fine-grained structural constituents. It has been established that optimizing the concentration of REMs, including cerium, promotes the formation of a more uniform ferritic-pearlitic, bainitic, or martensitic structure, reduces structural heterogeneity, and enhances resistance to crack initiation and propagation. The integration and systematization of disparate literature data have made it possible to identify patterns in the structural evolution of iron-carbon alloys alloyed with REMs, as well as to highlight promising areas for their application. These findings provide a scientific foundation for the development of a new generation of steels with an improved combination of strength and toughness, aimed at enhancing the technological and economic efficiency of metallurgical production.
The authors express their gratitude to their colleagues at the Navoi Machine-Building Plant (part of JSC “NMMC”) for providing access to equipment used during the research.

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