Abstract
The results of dilatometry, metallography and hardness testing of the decomposition process of supercooled austenite of R350LHT steel are presented. During continuous cooling and in isothermal conditions, continuous cooling transformation diagrams of supercooled austenite decomposition of steel R350LHT are constructed.
Highlights
Welding of railway rails is based on detailed understanding of the main characteristics of rail steels
Information on the kinetics of supercooled austenite transformation is of great importance since it serves as a basis for obtaining the hardened layer with required thickness, for selecting modes of heat treatment and ensuring the required indicators of the obtained physical and mechanical properties [1,2,3,4,5,6,7]
It should be noted that most types of heat treatment of structural steels are carried out with the heating of the processed material above the critical temperatures As1 or As3, that is, to the temperatures of existence of the high-temperature phase – austenite, and the formation of the final structural steel state in this case occurs during the decomposition of austenite, which was supercooled below the critical points [8]
Summary
Welding of railway rails is based on detailed understanding of the main characteristics of rail steels. The temperature range and the kinetics of the intermediate transformation depend mainly on the chemical composition of the austenite This interval shifts towards lower temperatures with an increase in the content of carbon and alloying elements. In carbon and some low-alloy steels containing non-carbide-forming elements, diffusion and intermediate transformations occur in close temperature ranges. On the other hand, does not affect the temperature range of the martensitic transformation [11] These prerequisites formed the basis for the development of a new rail welding technology. To describe the possible structural states that can be obtained at continuous cooling, as well as in isothermal conditions, CCT and isothermal diagrams of the supercooled austenite decomposition of steel under study were constructed and, on the basis of these materials, a new technology for welding differentially heat-strengthened rails was developed
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