Microstructure and Properties of Nanoduplex Bainite-Austenite Steel for Ultra-High-Strength Plates

• Published in: Steel research international Vol. 85; no. 12; pp. 1620 - 1628
• Main Authors: Garbarz, Bogdan, Burian, Wojciech
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.12.2014; Wiley Subscription Services, Inc
• Subjects: Austenitic stainless steel; Cooling; Mechanical properties; Microstructure; Nanostructure; nanostructured bainite; phase transformations; Plates; Scanning electron microscopy; Steels; Tensile strength; Transformations
• ISSN: 1611-3683; 1869-344X
• DOI: 10.1002/srin.201300453

Basing on experimentally determined continuous cooling transformation (CCT) and time–temperature–transformation (TTT) diagrams, examination of microstructure by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD) techniques and measurements of mechanical properties an optimized chemical composition of a nanostructured bainite–austenite steel intended for production of plates is proposed. The optimized composition enables to manufacture ultra‐high‐strength plates up to 15 mm in thickness at relatively low cost of alloying elements and with characteristics facilitating industrial production. Experimental flat bars manufactured in semi‐industrial conditions of the developed steel containing 0.56% C, 2.00% Mn, 1.76% Si, 1.29% Cr, and 0.76% Mo after transformation at 225°C for 60–72 h show good combination of mechanical properties: ultimate tensile strength over 1.9 GPa, yield strength in the range of 1.3–1.4 GPa, total elongation about 15% and hardness at the level of 600 HV. Basing on experimentally determined continuous cooling transformation (CCT) and time–temperature–transformation (TTT) diagrams, measurements of mechanical properties and examination of microstructure an optimized chemical composition of a nanostructured bainite–austenite steel intended for production of plates is proposed. The optimized composition enables to manufacture ultra‐high‐strength plates up to 15 mm in thickness.