Selection of the Heating Temperature of Microalloyed Steel for Hardening Heat Treatment of Railway Wheels
O. I. Babachenko, G. A. Kononenko, R. V. Podolskyi, O. A. Safronova, O. A. Shpak
Z. I. Nekrasov Iron and Steel Institute, NAS of Ukraine, 1 Academician Starodubov Sqr., UA-49050 Dnipro, Ukraine
Received: 06.09.2023; final version - 24.10.2023. Download: PDF
Analytical studies of both the influence of chemical elements on the mechanical properties of steels and their influence on the stability of austenite are carried out. The experience of creating low-alloyed and microalloyed steels is analysed that made it possible to determine the influence of individual alloying elements (Mn, Si, Cr, Ni, Mo, V, etc.) on the structural condition and set of operational properties of wheels. Smelting of steel ingots of experimental composition is carried out in laboratory conditions. As shown, the use of steel with alloying carbide-forming elements for the production of railway wheels leads to the need to adjust the modes of thermal strengthening in order to obtain the best set of mechanical properties. To increase the wear resistance of solid-rolled wheels, it is necessary to carry out their heat treatment in such a way that, in all layers of the rim, dispersed lamellar products of austenite decomposition and fine-grained structure of steel are obtained. When heating the wheels for hardening, it is necessary to achieve a uniform austenitic state of steel, which ensures the given amount of rim strengthening, satisfactory values of impact viscosity in the wheel disc. At the same time, the size of the austenite grain depends on the heating temperature for hardening, which significantly affects the value of the viscosity of the rim metal. The goal of the work is to determine the rational heating temperature before strengthening heat treatment of experimental steel for railway wheels microalloyed with vanadium (up to 0.11 wt.%) and molybdenum (up to 0.15 wt.%), with an increased content of silicon (up to 0.57 wt.%), chromium (up to 0.9 wt.%) and nickel (up to 0.7 wt.%). An experiment is performed to determine the heating temperature for strengthening heat treatment of railway wheels made of experimental steels by the method of hardening at different temperatures. According to the results of metallographic studies, it is established that, for steel samples No. 1 (comparative carbon steel) and No. 2 (0.9% Cr and 0.41% Ni) at a heating temperature of 900°C, some changes in the morphology of the microstructure are already observed. For samples made of steel No. 4 containing 0.89% Cr and 0.11% Ni, when heated to 900°C and subsequently quenched, the structural heterogeneity is strongly pronounced. For samples made of steel No. 3 containing 0.21% Cr and 0.70% Ni, the formation of a homogeneous dispersed structure is observed during quenching from 900°C. As established, the rational heating temperature for strengthening heat treatment for steel compositions No. 1, No. 2 and No. 4 is of 850°C; for steel composition No. 3, the heating temperature is of 900°C. The optimal heating temperatures for experimental steels are established.
Key words: railway wheels, steel, pearlite, microstructure, smelting, heat treatment.
URL: https://mfint.imp.kiev.ua/en/abstract/v45/i12/1413.html
DOI: https://doi.org/10.15407/mfint.45.12.1413
PACS: 61.66.Dk, 61.72.Ff, 61.72.Mm, 64.70.kd, 81.05.Bx, 81.30.Hd, 81.40.-z
Citation: O. I. Babachenko, G. A. Kononenko, R. V. Podolskyi, O. A. Safronova, and O. A. Shpak, Selection of the Heating Temperature of Microalloyed Steel for Hardening Heat Treatment of Railway Wheels, Metallofiz. Noveishie Tekhnol., 45, No. 12: 1413—1429 (2023) (in Ukrainian)