Experimental and Numerical Investigation on the Effect of the Tempcore Process Parameters on Microstructural Evolution a
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Experimental and Numerical Investigation on the Effect of the Tempcore Process Parameters on Microstructural Evolution and Mechanical Properties of Dual‑Phase Steel Reinforcing Rebars Mohammad Reza Akbarpour1 · Amirhossein Mashhuriazar2 · Mohammad Daryani3 Received: 26 April 2020 / Accepted: 30 July 2020 © The Korean Institute of Metals and Materials 2020
Abstract One of the most efficient and cheapest ways to improve steel reinforcement bars is the Tempcore process. In this study, the effects of water pressure, water temperature, bar diameter, and its initial temperature, as Tempcore process parameters on microstructural and mechanical properties of reinforcing rebars were numerical and experimental investigated by using the Taguchi experimental design method. Results showed that these Tempcore process parameters influence the cooling intensity, which causes the formation of martensite at the surface layer and fine-grained ferrite–pearlite at the core and improvement of tensile strength. All of the considered parameters strongly affect the volume fraction of ferrite and pearlite in the rebar center and thickness of the martensite layer, but among them, water pressure with a 59% impact has a more substantial effect. Ultimately, to figure out the mechanical characteristics of hot rolled and optimal sample’ rebar, tensile tests were conducted. Outcomes displayed that the Tempcore process increases the yield and ultimate tensile strengths as much as 1.5 and 1.3 times, respectively, but slightly decreases the elongation. Keywords Tempcore process · Dual-phase steel · Cooling rate · Mechanical properties · Simulation
1 Introduction Favourable mechanical properties and cost-effective price are among the main priorities of consumers of steel bars. However, it is possible to use micro-alloy elements like vanadium, nickel, molybdenum, and chromium to produce bars with desirable mechanical properties [1–4]. Yet, this is expensive and therefore not cost-effective. In recent decades, to improve mechanical properties and reduce production costs, the use and development of different cooling control methods have attracted the attention of many researchers * Mohammad Reza Akbarpour [email protected] 1
Department of Materials Engineering, Faculty of Engineering, University of Maragheh, P.O. Box 83111‑55181, Maragheh, Iran
2
Faculty of Material and Metallurgical Engineering, Amirkabir University of Technology, P.O. Box 15916‑34311 Tehran, Iran
3
Faculty of Chemical Engineering, Sahand University of Technology, P.O. Box 53318‑11111 Sahand New Town, Tabriz, Iran
in this field. Production of steel bars under rapid cooling systems was first introduced in 1974 [5]. In this method, the rebar enters the cooling system after leaving the last contact shelf with a temperature of about 1100 °C. During this process, the surface temperature of the rebar reduces sharply due to intense heat transfer and the austenite phase is converted to martensite [6]. The thickness of this phase varies depending on the conditions of
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