Effects of Tempering on the Microstructure and Properties of a High-Strength Bainite Rail Steel with Good Toughness

Abstract

An advanced bainite rail with high strength-toughness combination was produced in a steel mill and the effects of tempering on the microstructure and properties of the bainite rail steel were investigated by optical microscopy, transmission electron microscopy, electron back-scattering diffraction and X-ray diffraction. Results indicate that the tensile strength, elongation and impact toughness were about 1470 MPa, 14.5% and 83 J/cm 2 , respectively, after tempering at 400 • C for 200 min. Therefore, a high-strength bainite rail steel with good toughness was developed. In addition, the amount of retained austenite (RA) decreased due to bainite transformation after low-temperature tempering (300 • C) and RA almost disappeared after high-temperature tempering (500 • C). Moreover, as the tempering temperature increased, the tensile strength of the rail head first decreased due to the decreased dislocation density and carbon content in bainite ferrite and the coarseness of bainite ferrite, and then increased because of carbide precipitation at high-temperature tempering. Furthermore, RA played a significant role in the toughness of bainite rail. The elongation and toughness of the rail obviously decreased after tempering at 500 • C for 200 min because of the disappearance of RA and appearance of carbides.

Effect of Isothermal Transformation Treatment and Tempering on the Microstructure and Hardness of a Medium C and High Si Steels

“…Mo as an alloying element is known to suppress the primary ferrite and pearlite and hence enhances bainite formation. [20][21][22][23] Based on the heat treatment procedure, Mo may exhibit secondary hardening in tempered steels. 20) Lately, studies on Q&P steels revealed that the Mo-containing alloy exhibited greater austenite fractions than the base alloy and in Mo-containing alloy, the stability of retained austenite is improved.…”

Processing–Structure–Property Relationships in Metals

“…The book gathers manuscripts from academic and industrial researchers with stimulating new ideas and original results. It consists of one review paper regarding state of art and perspectives of alloys for aeronautic applications [1] and fifteen research papers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] focused on different materials and processes.…”

“…Zhu et al [14] report about a 1500-MPa-grade bainite rail developed and produced in an industrial production line. Nowadays, pearlite rail is widely used in the construction of railways, although high-speed and heavy-loading railways require steels with higher strength, toughness, and wear resistance.…”

A Further Analysis on Ti6Al4V Lattice Structures Manufactured by Selective Laser Melting

“…With regard to metal manufacturing, the relationship among process parameters, microstructure, and mechanical properties is fundamental in different areas (i.e., sintering, welding, casting, and plastic forming) and generally involves innovative and traditional fabrication methods [1–3].…”