Nosov Magnitogorsk State Technical University, Magnitogorsk, Russia

A. B. Sychkov, Dr. Eng., Prof., Dept. of Foundry Processes and Materials Science, e-mail: absychkov@mail.ru
O. N. Tulupov, Dr. Eng., Prof., Dept. of Materials Processing Technologies, e-mail: o.tulupov@mail.ru
A. N. Zavalishchin, Dr. Eng., Prof., Dept. of Foundry Processes and Materials Science, e-mail: zaval1313@mail.ru
N. A. Baranov, Postgraduate Student, Dept. of Materials Processing Technologies, e-mail: nikita_ram96@mail.ru

A review of modern technologies for carrying out heat treatment (HT) of reinforcing bars in the flow of modern long-section continuous hot rolling mills using the heat of pre-rolling heating according to interrupted or intermittent (thermal cycling technology) quenching with self-tempering schemes is given. In this case, the microstructure of the metal varies over a wide range – from pearlite of various dispersion to tempered martensite. The main technological factors determining the achievement of a given level of structure and properties are the self-tempering temperature and the cooling rate of rolled products. The conditions for obtaining such technological properties of reinforcement as weldability, seismic, cold and hydrogen resistance, as well as corrosion resistance, fatigue endurance using in-line HT modes. Weldability is ensured by the chemical composition of steel, compliance with the technology of metal preparation, welding process, and post-processing of the seam and heat-affected zone. Seismic resistance of reinforcement is achieved by the ratio of temporary tensile strength to yield strength – at least 1.25, this ratio is achieved either by microalloying steel with elements such as vanadium, or by selecting thermal cycling modes of the metal. Corrosion resistance is formed by selecting the chemical composition of steel and special thermal cycling modes. The elimination or minimization of reversible hydrogen embrittlement is ensured by the technology of steel smelting and casting, which limits the saturation of steel with hydrogen, and by aging the reinforcement after HT for diffusion release of hydrogen into the environment. Fatigue endurance is increased by limiting the reinforcement strength and using a profile that minimizes mechanical stress concentrators. Cold resistance is formed by thermal cycling modes by obtaining a quasi-composite, multilayer structure. The specified technologies and equipment have been successfully implemented at metallurgical enterprises of the Russian Federation and neighboring countries (Magnitogorsk Iron and Steel Works, Moldavian and Belarusian Metallurgical Plants, etc.).

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