Effect of flash processing on recrystallization behavior and mechanical performance of cold-rolled IF steel
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Effect of flash processing on recrystallization behavior and mechanical performance of cold-rolled IF steel Peng-yu Wen 1,2), Jian-sheng Han 1), Hai-wen Luo 1,2), and Xin-ping Mao 1) 1) State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China 2) Department of Ferrous Metallurgy, University of Science and Technology Beijing, Beijing 100083, China (Received: 1 December 2019; revised: 13 February 2020; accepted: 17 February 2020)
Abstract: Flash processing (FP) has attracted considerable attention due to its high efficiency, economic advantages, and the extraordinary opportunity if offers to improve the mechanical properties of steel. In this study, we investigated the influences of FP on the recrystallization (REX) behavior and mechanical performance of cold-rolled IF steel. Using a thermomechanical simulator, we performed both single-stage FPs, at heating rates of 200°C/s and 500°C/s, and two-stage FP, with an initial preheating to 400°C at a rate of 5°C/s and then to peak temperatures at a rate of 200°C/s. In comparison to continuous annealing (CA), single-stage FP can effectively refine the recrystallized grain sizes and produce a similar or even sharper γ (ND (normal direction)//{111}) texture component. In particular, the heating rate of 500°C/s led to an increase in the yield strength of about 23.2% and a similar ductility. In contrast, the two-stage FP resulted in a higher REX temperature as well as a certain grain refinement due to the stored strain energy, i.e., the driving force of REX, which was largely consumed during preheating. Furthermore, both stronger {110} and weaker γ texture components appeared in the two-stage FP and were believed to be responsible for the early necking and deterioration in ductility. Keywords: flash processing; interstitial-free steel; recrystallization; mechanical properties; texture
1. Introduction Interstitial-free (IF) steel is an irreplaceable advancedhigh-strength steel (AHSS) used in the automotive industry, in which atoms of the interstitial elements C and N are scavenged upon the addition of elements Ti or Nb [1]. It is well known that this steel possesses excellent formability and superior deep drawability due to the existence of strong γ (ND (normal direction)//{111}) fiber recrystallization (REX) texture [2–4], so it has been extensively used in the outer shells of cars [5]. In the past decade, considerable efforts have been made to achieve extremely low C and N contents by optimized metallurgical processing [6–7] to further improve drawability, as a stronger and more ductile IF steel is now in demand due to the requirement for lightweight automobiles. For example, using extra mechanical deformation processes, heterogeneous microstructures have been formed [8–10] that could be used to manufacture stronger IF steel due to the mechanical incompatibility of the gradient layers. However, the commercialization of these advances has met with great difficulty.
Flash processing (FP) has
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