Using cold stretching deformation to increase the strength of rebars in coiled product manufacturing technologies

Abstract

Purpose. To analyze the current state-of-the-art reinforcing bar (rebar) production for the construction industry, review existing data on the effects of strain hardening through cold stretching of steel rods, and apply these findings to the development of an effective technology for producing high-strength coiled rebar. Methodology. The research is based on an analytical study of using cold stretching deformation to increase the strength of steel rods. A comparative analysis of known patented technologies for producing 500 N/mm² strength class rebar in coils, particularly those developed in post-Soviet countries, was also conducted. Findings. The study analyzed three primary methods for strengthening rebar: alloying, heat treatment, and cold deformation. Alloying has become less cost-effective due to the high price of ferroalloys. Heat treatment is currently the most widespread method for producing high-strength rebar (grades A500C, A600C, etc.) according to DSTU 3760:2019. Cold deformation, while used globally for over 60 years and historically in the USSR to produce grade A-III_в rebar (equivalent to modern A500), is underutilized in Ukraine. The paper examines the principles of strengthening via cold stretching and reviews patented solutions for its application in coiled rebar production, presenting both positive and negative real-world examples. The necessity of applying stretch deformation to reliably achieve the 500 N/mm² strength class is established. Originality. The originality lies in the proposed technology and equipment for manufacturing cold-deformed coiled rebar. This process uniquely combines cold stretching deformation, which strengthens 100% of the product, with a final mechano-cyclical treatment. This combination not only increases strength but also ensures a high level of ductility in the finished product. Practical value. The implementation of the proposed technology will enable the domestic production of a new product: 500 N/mm² strength class coiled rebar for reinforced concrete. This product is poised to be in high demand and will play a significant role in the post-war reconstruction of Ukraine.