Development and Modeling of the Technological Welding Process of Differentially Heat-Strengthened Rails: Industrial Test
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lopment and Modeling of the Technological Welding Process of Differentially Heat-Strengthened Rails: Industrial Testing N. A. Kozyreva, *, R. A. Shevchenkoa, **, A. A. Usol’tseva, ***, A. N. Prudnikova, ****, and L. P. Bashchenkoa, ***** aSiberian
State Industrial University, Novokuznetsk, Kemerovo Oblast, 654007 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected] *****e-mail: [email protected]
Received December 24, 2019; revised January 24, 2020; accepted January 31, 2020
Abstract—The article describes the welding process study with the subsequent control of cooling for full-profile rail joints, produced by passing alternating electric current pulses after welding. The welding mode influence on the welded joint quality was investigated. Welding was carried out on a resistance butt welding machine MCP-6301 in conditions of the rail welding company OOO RSP-M (RSP-29). For research, the samples of P65 type full-profile rails of DT350 category 600 mm long were cut out. The isothermal holding conditions after welding were controlled using a personal computer with a change in the program of the SIMATIC S7-300 industrial controller and the software SIMATIC STEP 7, which allows modes of controlled cooling to be set. The control program was written in the LAD graphic language. To search for optimal modes of controlled cooling, a complete factor experiment N = 2k was carried out. Non-heat-treated joints were tested for three-point static bending according to the state standard STO RZD 1.08.002 – 2009 “Railway rails, welded by electric contact method”. Static bending tests were carried out on the press of PMS-320 type. Values of the force arising during bending Pbend and the bending deflection fdef at which the control sample is destroyed, were determined. The maximum values of these indicators were also determined if the sample was not destroyed during the tests. During the experiments, regression models were obtained for output parameters of the bending force and bending deflection. Sample macrostructure and metal hardness distribution on rolling surface of the rails welded joint were studied. A new method of resistance butt welding was developed, which makes it possible to obtain a welded connection of P65 type rails of DT350 category with properties that exceed the technical requirements of the mentioned state standard. Keywords: rails, resistance welding, heat treatment, current, impulse, welding mode, hardness, heat affected zone DOI: 10.3103/S096709122005006X
INTRODUCTION Technologies providing high quality continuous welded rail track are widely used in the world [1–9]. In this case, depending on steel chemical composition, the welding process is chosen, which determines the linear and temperature fields in the heat affected zone (HAZ) of the welded joint [10–14]. The thermal mode choice is based on the formation elimination of hardening structures (martensite and bainite), which cause additional cracks leading to rail destruction
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