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<p>The present study aims to provide a simpler and more efficient production method by applying various heat treatment techniques to B420C reinforcing steel as an alternative to Tempcore model. In this context, B420C steel was subjected to partial austenitization at 800&#xa0;°C for 1&#xa0;h and then cooled separately in different environments such as water (WQ), oil (OQ), air (normalizing) and furnace (annealing). The microstructures of heat-treated steels were examined using Optical Microscopy and Scanning Electron Microscopy, and analyzed in conjunction with mechanical properties such as microhardness and tensile strength. The identified phases were supported by phase transformation diagrams derived from cooling curves. Water quenching resulted in the formation of a ferrite+martensite dual phase in the microstructure of the steel, which exhibited high strength but low energy absorption. In contrast, after annealing and normalizing, a ferrite+pearlite dual phase was formed, characterized by lower strength but higher energy absorption. Oil quenching led to the formation of ferrite+bainite dual phase and the mechanical properties of this steel were similar to B420C steel. In addition, to determine the usability of reinforcing steels whose mechanical properties were changed by heat treatment in reinforced concrete elements, 3-point bending tests were applied to reinforced concrete beams produced with these steels. In this framework, the experimental results were compared with the theoretical results in the building codes (ACI318, TS708). In this context, reinforcing steels with a tensile/yield strength ratio above 1.24, subjected to OQ, annealing, and normalization treatments, exhibited significantly higher energy absorption capacity and ductility performance in reinforced concrete beams compared to steels with a lower ratio subjected to WQ treatment. Therefore, it is crucial that the tensile/yield strength ratio of the reinforcing steel to be used is a minimum of 1.24, for the reinforced concrete elements to demonstrate ductile behavior under earthquake loads.</p>

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Evaluation of Alternative Heat Treatments for the Improvement of Tempcore Method in Reinforcing Steel Production

  • 期刊论文

  • 发表日期：

    2025年9月19日

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  • Ugur Avci,
  • Abdulkadir Gulec

摘要

The present study aims to provide a simpler and more efficient production method by applying various heat treatment techniques to B420C reinforcing steel as an alternative to Tempcore model. In this context, B420C steel was subjected to partial austenitization at 800 °C for 1 h and then cooled separately in different environments such as water (WQ), oil (OQ), air (normalizing) and furnace (annealing). The microstructures of heat-treated steels were examined using Optical Microscopy and Scanning Electron Microscopy, and analyzed in conjunction with mechanical properties such as microhardness and tensile strength. The identified phases were supported by phase transformation diagrams derived from cooling curves. Water quenching resulted in the formation of a ferrite+martensite dual phase in the microstructure of the steel, which exhibited high strength but low energy absorption. In contrast, after annealing and normalizing, a ferrite+pearlite dual phase was formed, characterized by lower strength but higher energy absorption. Oil quenching led to the formation of ferrite+bainite dual phase and the mechanical properties of this steel were similar to B420C steel. In addition, to determine the usability of reinforcing steels whose mechanical properties were changed by heat treatment in reinforced concrete elements, 3-point bending tests were applied to reinforced concrete beams produced with these steels. In this framework, the experimental results were compared with the theoretical results in the building codes (ACI318, TS708). In this context, reinforcing steels with a tensile/yield strength ratio above 1.24, subjected to OQ, annealing, and normalization treatments, exhibited significantly higher energy absorption capacity and ductility performance in reinforced concrete beams compared to steels with a lower ratio subjected to WQ treatment. Therefore, it is crucial that the tensile/yield strength ratio of the reinforcing steel to be used is a minimum of 1.24, for the reinforced concrete elements to demonstrate ductile behavior under earthquake loads.