Influence of the Speed of High-Carbon Steel Billet in the Patenting Unit on Its Final Structure and Mechanical Properties

Prestressed ferroconcrete structures are widely used at present. As a result, compressive stress is created in the concrete and tensile stress in the reinforcing rope. The stressed reinforcing rope is better able to withstand the external loads that it experiences throughout the life of the construction. Consequently, larger loads may be applied or, with unchanged load, the size of the construction may be decreased, with accompanying savings of concrete and steel. Today, it is important to develop a manufacturing technology for nanostructured reinforcing rope that may be used in prestressed concrete-steel constructions. This technology is based on patenting, in which the steel acquires the structure of a fine ferrite–carbide mixture characterized by high strength and improved deformability. In the present work, the influence of increased billet speed in the patenting unit on the final structure and mechanical properties of steel 80, 70, and 50 is investigated, with a view to increasing the productivity in patenting, without loss of strength or plasticity of the steel, in the production of blanks for nanostructured reinforcing rope that may be used in prestressed concrete-steel constructions. To determine the heat-treatment time and temperature, the Gleeble 3500 system is used to plot diagrams of the isothermal decomposition of undercooled austenite. In qualitative and quantitative analysis of the microstructure, the interlamellar spacing of the ferrite–carbide mixture is determined for different billet speeds in the patenting system. The mechanical properties are studied in tensile tests. It is found that, for all billet speeds, the interlamellar spacing of the ferrite–carbide mixture is practically the same and is optimal for subsequent drawing: 0.1–0.2 μm. Thanks to the fine structure of the ferrite–carbide mixture formed in patenting, the strength of the billet is increased. Hence, in subsequent drawing, the billet may withstand greater compression without fracture. In the production of patented billet for nanostructured reinforcing rope, its speed in the patenting unit may be increased to 5 m/min. Consequently, the productivity may be increased without loss of strength and plasticity of the billet.