Enhancement of mechanical properes of low carbon steel based on heat treatment and thermo-mechanical processing routes Mohsen Balavar, Hamed Mirzadeh* School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran. Recieved: 17 October 2018; Accepted: 30 November 2018 * Corresponding author email: [email protected] ABSTRACT Keywords: Low carbon steel, Grain refinement, Mechanical properes, Strain hardening rate. Journal of Ultrafine Grained and Nanostructured Materials https://jufgnsm.ut.ac.ir Vol. 51, No.2, December 2018, pp. 169-173 Print ISSN: 2423-6845 Online ISSN: 2423-6837 DOI: 10.22059/JUFGNSM.2018.02.09 Thermal treatments and thermo-mechanical processing routes were applied on a convenonal structural steel (st37 steel: 0.12C-1.11Mn-0.16Si) for improvement of tensile properes and enhancement of work- hardening behavior. Full annealing resulted in a sheet with coarse ferrite grains and pearlite colonies arranged alternavely in disnct bands, which showed high duclity, low strength, and the presence of the yield point elongaon at the beginning of the plasc flow. The cold-rolled sheet, however, showed poor duclity but much higher strength level. The dual phase (DP) sheet, resulted from intercrical annealing in the austenite plus ferrite region, showed a remarkable strength-duclity balance, which was related to the excellent work-hardening behavior. A bimodal-sized ferric structure with the appearance of a poor strain hardening regime aſter experiencing a high yield stress was obtained from the subcrically annealed cold- rolled DP microstructure. The ultrafine-grained sheet was processed by applying the abovemenoned route on a martensic microstructure, which resulted in low duclity but high strength at ambient temperature. These results demonstrated the ability to control the properes of convenonal steels by simple thermal and thermo-mechanical treatments. 1. Introduction Grain size effects on the tensile properties of metallic materials are well-known. erefore, large plastic straining [1,2], mechanical alloying [3], thermo-mechanical processing [4], and thermal treatments [5] are commonly used for grain refinement. Regarding low-carbon steels, remarkable grain refinement can be achieved by cold deformation and annealing (CRA) of martensite [6-8]. e effect of intercritical annealing on the enhancement of tensile properties of low carbon steels has been also taken into account, which results in the formation of ferritic-martensitic dual phase (DP) microstructure [9,10]. By consideration of a DP microstructure, the CRA process results in a bimodal sized ferrite structure, where large grains originate from ferrite and finer grains develop from martensite [11]. is can result in a good ductility-strength balance [12]. ese routes should be applied to different steel compositions, especially the low-cost commercial grades, for augmenting their potential applications. Accordingly, the present work is dedicated to the
Enhancement of mechanical properties of low carbon steel based on heat treatment and thermo-mechanical processing routes
Apr 25, 2023
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