Title: The influence law of cooling rate on microstructure and properties of low-carbon high-grade AF pipeline steel

Authors: Yongli Chen; Xuejiao Zhou; Yueyue Jiang; Qingxia Wang

Addresses: School of Metallurgical and Materials Engineering, Chongqing University of Science and Technology, Shapingba District, University Town, Chongqing 401331, China; State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, He-Ping District, Shenyang, Liaoning Province, 110819, China ' School of Metallurgical and Materials Engineering, Chongqing University of Science and Technology, Shapingba District, University Town, Chongqing 401331, China ' School of Metallurgical and Materials Engineering, Chongqing University of Science and Technology, Shapingba District, University Town, Chongqing 401331, China ' School of Metallurgical and Materials Engineering, Chongqing University of Science and Technology, Shapingba District, University Town, Chongqing 401331, China

Abstract: To explore influence laws of cooling rate on microstructure and properties of low-carbon high-grade acicular ferrite (AF) pipeline steel. The microstructure and properties influence of alloy composition and super-cooled austenite continuous cooling transformation (CCT) has been investigated by thermodynamic analysis and calculation. Studies have shown that the optimised composition was C0.06, Si0.2, Mn1.85, Nb0.04, Ni0.33, Cr0.4, Mo0.15, P ≤ 0.01 and S ≤ 0.002, when the cooling rate was less than 1°C/s and pearlite (P) transition has been suppressed. When the cooling rate exceeds 20°C/s, structure mainly consists of AF and small amount of retained austenite (RA), and the mechanical properties partially met and exceed X90 performance levels of API SPEC 5L-45th. This paper offers a novel research method of low-carbon AF high-grade steel. The conclusion provides theoretical and practical guidance for production and study of such types of steel.

Keywords: high-grade pipeline steel; alloy composition design; microstructure; acicular ferrite; CCT; continuous cooling transformation; cooling rate; low-carbon steel; mechanical properties.

DOI: 10.1504/IJMMP.2016.080700

International Journal of Microstructure and Materials Properties, 2016 Vol.11 No.5, pp.373 - 382

Received: 09 Feb 2016
Accepted: 27 Jun 2016
Published online: 04 Dec 2016 *

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