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      https://www.ias.ac.in/article/fulltext/sadh/046/0088

    • Keywords

       

      Gleeble; CCT; CGHAZ; dilation; impact; toughness; API X70.

    • Abstract

       

      In the present work, continuous cooling transformation (CCT) of coarse-grained heat-affected zone (CGHAZ) and simulation of Charpy-sized impact specimens were performed using a Gleeble 3800 thermomechanical simulator. Results obtained from the dilation studies show significant effect of cooling rates onmicrostructure and low-temperature (–20 ΟC) Charpy impact toughness. Phase transformation temperatures (Ar3 and Ar1) and impact toughness decreased while hardness and amount of bainite increased with increasing coolingrates. At slow cooling condition (\ 5 ΟCs-1) quasi-polygonal ferrite and pearlite phases were observed in the microstructure. At medium cooling rate (5–25 ΟCs-1), bainite and quasi-polygonal ferrite were obtained in the microstructure. For still faster cooling rates, microstructure was completely bainitic in nature. Themicrostructures were confirmed by hardness measurement where the hardness value for lower, medium and high cooling rates were 191–196, 213–214 and 234–253 HV, respectively. Charpy impact toughness increased with decrease in cooling rate due to the presence of softer ferrite phase.

    • Author Affiliations

       

      AJIT KUMAR NAIK1 RAKESH ROSHAN1 KANWER SINGH ARORA2 NIKHIL SHAJAN2 SUBASH CHANDRA MISHRA1

      1. Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela 769 008, India
      2. R&D, Tata Steel Limited, Jamshedpur 831 001, India
    • Dates

       
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