Quenched and Tempered Reinforcement bars Feb24

Quenched and Tempered Reinforcement bars...

        Quenched and Tempered Reinforcement bars  The Tempcore process for the manufacture of reinforcement bars has been developed in the seventies by Centre de Rechaerche Metallurgiques (CRM) Belgium in order to manufacture high yield strength weldable concrete reinforcement bars from mild steel billets. It is one of the most effective processes for the production of popularly known TMT (Thermo Mechanically Treated) reinforcement bars. Thermex from HSE Germany is the other process for the manufacture of Reinforcement bars.  Principle Both the processes are similar in nature and are based on heat treatment principle. These processes impart high strength to the bars using the technique of Thermo Mechanical Treatment as against Cold Twisting which is used for the manufacture of Torsteel reinforcement bars. Due to the heat treatment the micro structure of the bar consists of Tempered Martensite in the periphery and Ferrite Pearlite in the centre (Fig !). The strength to the bar is by Tempered Martensite layer while the ductility to the bar is incorporated by the Ferrite- Pearlite layer.   Fig. 1 Microstructure of Reinforcement Bars  The schematic diagram of the process on a Time-Temperature curve is given on Fig. 2.   Fig 2 Schematic Diagram on a Time – Temperature Curve  Process Heated steel billets are rolled in the rolling mill to the final size and shape of the reinforcement bar. At this stage the bar is processed by this process. The process is carried out in three successive stages as described below. The first stage begins as soon as the bar leaves the final mill stand. The bar is rapidly and energetically cooled (Quenched) with water through a short cooling installation, where it undergoes surface hardening (Martensite layer). At this stage the surface layer is converted into Martensite while the core remains Austenitic. The...