Numerical Simulation of Thermal-Structural State of the Railway Rail During Hardening

• Main Authors: A. M. Pokrovsky, D. N. Tretyakov
• Format: Article
• Language: Russian
• Published: MGTU im. N.È. Baumana 2015-01-01
• Series: Nauka i Obrazovanie
• Subjects: railway rails; quenching in oil; linear non-stationary problem of heat conduction; thermal coefficients; finite element method; the kinetics of structural transformations; austenite; ferritecarbide; martensite
• Online Access: http://technomag.edu.ru/jour/article/view/223

The production of high-strength rails is an extremely urgent problem, because every year increases the speed and weight of rolling stock. It is very important to choose a rational modes of heat treatment, which on the one hand contribute to the formation of the desired structure with a given hardness, and on the other hand do not lead to warping of the rails and destruction in the early stages of operation due to the high level of residual thermal stresses. Experimental methods for research of thermal-structural state rail during heat treatment with a view to rationalizing modes are ineffective because they do not allow to trace the kinetics of structure formation, especially in the internal areas of the rail. Therefore, at the forefront methods of mathematical modeling. In the present work, the developed methods and software for numerical simulation of temperature and structural condition of the railway rail when it is heat treated. The solution to the problem of linear unsteady heat conduction carried out in a bulk formulation using finite-element ANSYS environment using 8-node 3D element Solid278. Mathematical modeling of transformation of austenite to ferrite-carbide implemented using the C++ programming language theory isokinetic reactions, which is based on the additivity rule for the transition from isothermal kinetics of austenite to non-isothermal conditions. To describe the isothermal transformation kinetics of austenite to ferrite-carbide used the equation of Avrami. The results of mathematical modeling as applied to bulk quenching in oil rail type R65, made of steel 85. It is established that the cooling of the rail to oil temperature 40 ° C occurs in approximately 10 minutes. Through mathematical modeling shows that after quenching the structure near the end at the edge of the base of the rail contains up to 89 % of martensite. The maximum share of ferrite-carbide in inner areas is about 50 %. Developed software tools necessary for the subsequent modeling of the stress-strain state of the rail in the process of heat treatment.