The Relationship Between Microstructural Evolution and Mechanical Properties of Heavy Plate of Low-Mn Steel During Ultra Fast Cooling

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 46; no. 7; pp. 2834 - 2843
• Main Authors: Wang, Bin, Wang, Zhao-dong, Wang, Bing-xing, Wang, Guo-dong, Misra, R. D. K.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.07.2015; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Communication; Electron microscopes; Materials Science; Metallic Materials; Microstructure; Nanotechnology; Steel; Structural Materials; Surfaces and Interfaces; Temperature; Thin Films; Fast Cool Rate; Bainite; Cementite Particle; Pearlite; Cementite
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-015-2933-1

We describe here the electron microscopy and mechanical property studies that were conducted in an industrially processed 20- and 40-mm C-Mn thick plates that involved a new approach of ultrafast cooling (UFC) together with significant reduction in Mn-content of the steel by ~0.3 to 0.5 pct, in relation to the conventional C-Mn steels, with the aim of cost-effectiveness. The study demonstrated that nanoscale cementite precipitation occurred during austenite transformation in the matrix of heavy plate during UFC, providing significant precipitation strengthening. With decrease in UFC stop temperature and consequent increase in the degree of undercooling, there was a transition in the morphology of cementite from lamellar to irregular-shaped nanoscale particles in the 20 mm heavy plate. With the increase in plate thickness, nanoscale cementite precipitated in bainitic lath at the surface of 40 mm heavy plate, which significantly increased the strength and decreased the elongation. Simultaneously, microstructural evolution in hot-rolled sheets was studied via simulation experiments using laboratory rolling mill to define the limits of microstructural evolution that can obtained in the UFC process and develop an understanding of the evolved microstructure in terms of process parameters.