Microstructural Refinement and Mechanical Properties of High‐Speed Niobium‐Microalloyed Railway Wheel Steel

Abstract

The relationship between microstructure and mechanical properties was studied in a Nb‐bearing high‐speed railway wheel steel and compared with a traditional low‐alloyed medium carbon steel. The microstructure of medium carbon steel comprised of ferrite and pearlite and the percentage of ferrite was increased from 4 to 24% on the addition of 0.06 wt% Nb and the grain size was refined. The addition of Nb inhibited mixed microstructure and delayed the coarsening temperature of austenite grains from 880 to 960 °C. The yield strength of Nb‐bearing steel was increased from 385 to 455 MPa and the Charpy v‐notch energy at −20 °C was increased from 7.0 to 19.0 J with no apparent reduction in tensile strength. Niobium formulates grain refinement and transformation of austenite to ferrite and pearlite over a wide region of cooling rate (<10 °C s−1) and temperature range (530–690 °C) in the medium carbon steel. With the calculation of Thermal‐Calc software and solid solubility formula, Nb exists in the form of precipitates. The grain refining and precipitation strengthening are roles of niobium in promoting ferrite–pearlite transformation and improve toughness in the medium carbon steel.

Microstructure and Properties’ Evaluation of W18Cr4V Modified by Fe–Zr–Nb–N–B Nano‐Powder Inoculants

“…As shown in Figure a, the eutectic M6C distributed in the grain boundaries was formed in a continuous web with a wide area. As we know, M6C is not easy to break in the forging process, which seriously affects the macroscopic properties of HSS . After inoculation, as shown in Figure b, the size of the M6C Ledeburite was significantly reduced, and fishbone carbide was transformed from a coarse mesh into a long and slender strip, which was more conducive to be broken in the forging process.…”

Mechanism and Effect Factor of Toughening of High-Speed Train Wheels

“…The microstructure of the rim of the railway vehicle wheel is lamellar pearlite and a small amount of ferrite, and the heat treatment method is to force cooling by water to form fine pearlite on the rim [28]. The distance of the pearlite layer directly affects the mechanical properties of the wheel rim.…”

Thermomechanical Control of Microstructure and Precipitation in Vanadium Microalloyed Steel: Influence of Finish Rolling and Coiling Temperatures

“…In other words, the addition of vanadium, as a substitute to Nb, to HSLA steels can further reduce the cost of production. Although there are studies on the process parameters of TMCP on V-Nb, V-Ti, Nb-Ti, and V-Nb-Ti microalloyed steels and the effect of vanadium addition on microstructure and mechanical properties of the same, [2,7,14,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] there are still a lack of the effects of the FRT and coiling temperature (CT) on the evolution of the microstructures and precipitation behavior of especially V (C, N) in only V microalloyed steel during TMCP. The aim is to understand the relationship between TMCP process, microstructure, and V (C, N) precipitates in V-microalloyed steel and to illustrate the influence of TMCP parameters on nucleation sites of precipitated phase in V-microalloyed steel.…”