Wheel Steel Research Articles

Effect of Tempering Temperature on Microstructure and Mechanical Properties of Bainitic Railway Wheel Steel with Thermal Damage Resistance by Alloy Design

Thermal damage is one of the principle modes of wagon railway wheels. A new bainitic railway wheel steel with high thermal damage resistance and good combination of strength, plasticity, and toughness was developed. Microstructure and mechanical properties of the new steels in a tempered condition at different temperatures were examined. Microstructures were observed using scanning electron microscope and transmission electron microscope. Mechanical properties were evaluated by tensile, hardness, and Charpy impact tests with a simultaneous comparison to pearlitic railway wheel steel. The characteristic of retain austenite and V(C,N) were measured through X-ray diffractometry and energy disperse spectroscopy. The results indicate that this new bainitic wheel steel presents a submicron-sized carbide-free bainite morphology and preferable integrated mechanical properties when tempered at 280–360 °C. Precipitation strengthening plays an important role for the high strength, since a two-time-strengthening mechanism of the yield strength led by precipitation has been found at 280–360 and 480–560 °C, respectively. Compared with a pearlitic railway wheel steel, bainitic wheel steel tempered at 320 °C has a 10% higher yield strength, five times higher impact toughness, and much better thermal damage resistance, which is a promising railway wheel material for higher speed or heavier axle-load service conditions.

Investigation of Tribological Properties of Rail and Wheel Steels

The wear resistance characteristics of AISI 51B60H and 30MnB5 steels with different carbon and boron contents were investigated. The analysis of the microstructure and hardness of steels was carried out. The specific wear rates in the conditions of dry and wet friction were calculated, and the friction coefficients were determined. The worn surfaces of rail samples were studied by electron microscopy. The possibility of using boron steels instead of R260 steel, which is used for manufacturing high-speed railways, was considered.

Effect of pearlite interlamellar spacing on fatigue property of a wheel steel

AbstractDifferent pearlite interlamellar spacings of 0.54 % carbon (C) wheel steel were obtained by heat treatment, and the influence of interlamellar spacing on fatigue behavior of the steel was studied through conducting the staircase method fatigue testing and decreasing/increasing stress intensity factor range (ΔK) fatigue crack growth tests. The results indicate that the fatigue endurance limit and fatigue threshold with smaller interlamellar spacing are higher than those with larger one, which can be well explained by dislocation slipping theory. Furthermore, the fatigue crack growth rates in the near‐threshold and Paris regions were found to reduce with decreasing the interlamellar spacing. The decreased growth rate is attributed to the deflected crack path induced crack closure effect, as evidenced by fatigue steps on the fatigue fracture surface. The present results show how to enhance the fatigue property of wheel steel through refining the pearlite interlamellar spacing.

TİCARİ ARAÇ TEKERLEK JANTININ SONLU ELEMANLAR YÖNTEMİYLE ANALİZİ VE TEST EDİLMESİ

Wheels are safety component of vehicle because they are exposed to variable stresses under static and dynamic forces. Fatique tests are determined by wheel test standards applying to designed wheel models. Radial fatigue test is one of the fatigue tests in which crack failures are investigated after definite cycles under dynamic loads. Test procedures take long time and are applied to finished products. The modifications in wheel design depending on the test results, requires conduction of production process repeatedly. This repetitive process increases the cost and time of final production. Numerical modelling gives quick solutions during design stage. Thus, the number of cyclic tests is decreased because of numerical modelling. Therefore, numerical modelling indirectly decreases the cost. In this study, it is aimed to calculate the stress on the rim under the loading conditions by the analysis of stress and displacement in commercial vehicle steel wheels through the development of the finite element models using the Ansys Workbench finite element system.

A Small-Scale Experimental Study of the Damage Due to Intermittent Shoe Braking on the Tread of High-Speed Train Wheels

Recent interest in emergency shoe braking in high-speed trains stimulated research on the damage due to sliding contact between brake blocks and wheel treads. Bi-disc tests, with rolling–sliding contact between specimens extracted from wheels and brake blocks, were previously performed in constant working conditions to reproduce the temperature of the wheel during braking. However, braking is often a discontinuous operation, obtained by intermittent contact between brakes and tread, to prevent excessive heating. In this article, braking is simulated by discontinuous tests, periodically interrupted to cool down the specimens. Three wheel steels (HYPERLOS, SANDLOS, and CLASS B) were tested against the same cast iron brake material. Measurements of the friction coefficient, contact surface temperature, and weight variation were performed. Moreover, optical microscopy observations and hardness tests were done on the cross section of the wheel specimens. Material transfer from the brake to the wheel disc with the formation of a discontinuous third-body layer was observed. This layer, when worn away, likely contributes to surface crack nucleation. In addition, the debris of both materials enhances abrasive wear. If compared with the continuous tests, the intermittent tests showed higher friction coefficient fluctuations and in some cases significantly different weight variation. Among the steels, the weight loss and subsurface hardening of HYPERLOS was higher in the discontinuous tests than in the longest continuous tests. CLASS B showed similar behavior in both tests. An effect of the temperature cycles on the friction coefficient and the wear behavior was hypothesized.

Вплив вмісту легуючих елементів і термічної обробки на ресурсні характеристики високоміцних колісних сталей при виготовленні залізничних коліс та їх ремонтному наплавленні... 41

Вплив вмісту легуючих елементів і термічної обробки на ресурсні характеристики високоміцних колісних сталей при виготовленні залізничних коліс та їх ремонтному наплавленні... 41

Influence of content of alloying elements and heat treatment on life characteristics of high-strength wheel steels during manufacture of railroad wheels and their repair surfacing

Influence of content of alloying elements and heat treatment on life characteristics of high-strength wheel steels during manufacture of railroad wheels and their repair surfacing

Effect of nonuniform microstructure on wear property of ER8 wheel steel

Because nonuniform microstructures may accelerate the wear rate of wheels made from ER8 steel, a wear test was performed on a wheel sample with a nonuniform microstructure, and the wear properties were compared with that of a wheel composed of a uniform microstructure. In addition, the wear mechanism of the wheel with a nonuniform microstructure was analyzed. In addition to the uniform microstructure of pearlite and proeutectoid ferrite, upper bainite was observed in the wheel with a nonuniform microstructure. The upper bainite disrupted the continuity and uniformity of the microstructure. Moreover, owing to the different work hardening mechanisms of upper bainite and pearlite, the plastic deformations of upper bainite and pearlite were incompatible, which induced and promoted the formation of fatigue cracks in the nonuniform microstructure and further accelerated fatigue wear.

Study of effect of wheel steel microalloying by calcium and barium on nonmetallic inclusions modification

The increase in freight cars axis loads, dynamic loads and heat impact on the wheels, change of other factors, stipulated by railway transport traffic intensification lead to considerable decrease of service life of solid-rolled wheels. To increase the service life of them, provision of the transport metal purity in non-deformed oxide nonmetallic inclusions with high content of Al2O3, decrease of general steel pollution by nonmetallic inclusions by micro-alloying and modification is an actual task. The purpose of the study was elaboration of wheel steel ladle treatment technology, including the steel micro-alloying and modification by barium-containing alloys to create material, which could meet high operation requirements, made to the railway wheels of new generation, intended to operate under increased axis loads conditions at the modern high-speed rolling-stock. It was shown, that replacement of everywhere applied silicocalcium by barium-based alloys is one of perspective ways of modification mechanism perfection. Results of industrial tests of micro-alloying of wheel steel by barium during ladle treatment presented. It was shown, that application for modification of cored wire with silicobarium filler instead of cored wire with silicocalsium filler СК-30, enabled to transform the nonmetallic inclusions into globular form practically completely, to raise the steel purity for all kinds of inclusions in both middle and maximum points range and to refine to some extent the grain size by 1-2 points. In the pilot metal at the depth of 40 mm from the surface, the gain was somewhat finer and more uniform (number 7), comparing with the existing technology (number 5-6). The pollution of the pilot metal by nonmetallic inclusions meets requirements of GOST 10791—2011 for category A and those of the standard EN 13262: 2004+А2:2011 for category 1.

Correlation between fatigue response of preformed bend DP600 steel specimen and wheel disc

AbstractThe present aim of this paper is to predict the cornering fatigue life of a wheel disc through a preformed bend DP600 steel specimen. To accomplish this objective, a newly designed preformed specimen with a bend radius equivalent to the weakest section of the wheel disc is fabricated by stamping operation followed by load‐controlled high‐cycle fatigue tests. Finite element (FE) simulation of stamping operation shows that an equivalent strain of 13% is induced to the bend specimen. Preformed bend specimen exhibits less fatigue resistance than the prestrained straight specimen for the same equivalent prestrain. A combined state of loading induces multiaxial stress state, giving rise to asymmetry of stresses along the thickness at the bend root of the DP600 steel specimen. Distribution of equivalent plastic strain and stress triaxiality from FE simulation indicates that fatigue crack occurs at the centre of the inner fibre of the bend root.

Metal Plating of Friction Surfaces of the “Wheel–Rail” Pair

It is shown that in conditions of significant increase of railway transport speeds, requirements for the safety of the friction–mechanical “wheel–rail” subsystem are increased. In order to solve the above problem, a method is proposed for metal plating “wheel–rail” friction surfaces by applying thin films of soft metal, for example, aluminum, with different values of hardness, on surfaces of rolling wheels and wheel ridges of locomotives. On the basis of quantum-chemical calculations, it has been proved that metal plating of the friction surfaces of the “wheel–rail” system provides a chemical bond between wheel steel and aluminum and the formation of a strong protective film. The performed bench tests of the “wheel–rail” model friction subsystem by methods of tribospectration identification of friction processes and dynamic monitoring of changes in elastic-dissipative bonds confirmed the formation of stable dynamic bonds in friction contact. The results of the research formed the basis of the creation of the algorithm of axial control of “wheel–rail” interaction processes at realization of forces of longitudinal and transverse creep, as well as at optimization of modes of vibrodynamic metal plating working surfaces of other tribosystems, of vehicles operating in heavy load–speed conditions of operation.

Effect of electrolyte-plasma surface hardening on structure wheel steel 2

This paper examines the influence of electrolyte-plasma surface hardening on the structure and microhardness of wheel steel mark 2. In the work electrolyte-plasma surface hardening was carried out in an electrolyte made from an aqueous solution 10 % carbamide (NH2)2CO 20 % sodium carbonate Na2CO3. The processing time was 2 seconds, Tmax = 850–900 ºC; U= 320V; I=40A. According to the results of the scanning transmission electron microscopy, the electrolyte-plasma surface hardening caused a change in the morphological constituents of mark 2 steel. In the initial state, the matrix of steel is a α-phase, the morphological components of which are fragmented ferrite, unfragmented ferrite and pearlite. After electrolytic-plasma surface hardening, a batch, high-temperature plate and low-temperature plate martensit is formed on the surface of the sample. Investigations have been carried out on microhardness determination on cross-section of wheel steel samples after quenching in aqueous solution of electrolyte. It is found that after electrolytic-plasma surface hardening, the microhardening values of this hardened surface layer increased ~ 3 times compared to the steel matrix, and the thickness of the hardened layer is 1000–1500 microns.

The effect of thickness variation and pre-strain on the cornering fatigue life prediction of a DP600 steel wheel disc

Cornering fatigue test of an automotive wheel is one of the essential tests to ensure the structural integrity of a wheel disc. Forming operation of wheel disc introduces forming history such as thickness reduction, pre-strain, and mean residual stresses. In this work, a methodology is proposed to consider the factors affecting the cornering fatigue performance of DP600 automotive wheel disc. The cyclic elastic-plastic Finite Element (FE) simulations are performed using the Chaboche kinematic hardening model. Local stress-strain states of critical element evaluated from FE simulations and fatigue parameters obtained from symmetric strain and stress controlled tests are coupled to predict the cornering fatigue life. Maximum equivalent stress and stress triaxiality at the cup radius region indicates a possible site for fatigue crack initiation. The incorporation of thickness variation and pre-strain effect is found to be the two most significant parameters for the accurate estimation of cornering fatigue life and failure location of wheel disc.

Influence of electrolytic-plasma surface quenching on the structure and strength properties of ferritic-pearlite class wheel steel

Influence of electrolytic-plasma surface quenching on the structure and strength properties of ferritic-pearlite class wheel steel

Wear behavior of bainitic and pearlitic microstructures from microalloyed railway wheel steel

Wear and contact fatigue are the main problems that reduce the durability of the rail and wheels. Pearlitic and bainitic microstructures have been studied over the years to obtain steel with higher mechanical properties, minimizing the wear and fatigue defects. However, the studies have not yet consistently confirmed whether bainite is a better alternative than pearlite to reduce the wear and contact fatigue. Therefore, in this paper, the twin-disc test evaluated, under dry conditions, the wear resistance and rolling contact fatigue (RCF) of bainitic and pearlitic microstructures obtained from forged microalloyed railway wheel steel. The samples were isothermally treated in furnace at 350 and 600 °C, respectively, and the tests had controlled load and slip conditions. Thus, the bainitic microstructure presented lower mass loss than the pearlitic one, having higher hardness and greater capacity to absorb plastic deformation in volume. Also, it took the delamination process longer to develop in the bainitic microstructure, and the cracks were closer to the surface than in the pearlitic microstructure. After the wear test, the magnetic Barkhausen noise (MBN) analysis indicated higher levels of stress in the bainitic microstructure surface than in the pearlitic one. These findings suggest that the high concentration of plastic deformation closer to the surface prevented crack nucleation and propagation to greater depths. Thus, this study supports the suggestion that the bainitic microstructure may be a better alternative than pearlitic microstructure concerning railway wheel production.

Wear Behavior of Ductile Iron Wheel Material Used for Rail-Transit Vehicles under Dry Sliding Conditions.

A ductile iron wheel used for a rail-transit vehicle was treated with a recommended heat-treatment process. The ductile iron wheel after heat treatment was composed of graphite nodules and tempered sorbite with an area fraction of 98%. A friction test of the ductile iron and carbon steel wheel materials was systematically performed under different normal loads and sliding velocities. The results indicated that the wear mechanism of the ductile iron wheel changed from adhesion to abrasion with an increase in the normal load level. Adhesion was the main wear mechanism at different sliding velocities and normal load level. The impact of the normal load on the wear mechanism was greater than that of the sliding velocity. Since the ductile iron wheel material had excellent thermal property and higher carbon content, it exhibited a lower wear rate, a smaller difference value of the friction coefficient, and plastic deformation on the worn surface than those of the carbon steel wheel material. This indicates that ductile iron wheels may have a longer wear life, greater traction, and higher stability during operation than carbon steel wheels. The iron wheels have the potential for being applied in rail-transit vehicles.

Influence of original microstructure on rolling contact fatigue property of D2 wheel steel

In this work, the influence of different original microstructure on the rolling contact fatigue (RCF) property of D2 wheel steel under oil lubrication condition is thoroughly studied by the GPM-30 rolling fatigue tester. Before pre-wear, the RCF life of the tempered sorbite (TS) sample and the lamellar pearlite + proeutectoid ferrite (P + F) sample are 7.2 × 105cycles and 5.4 × 105 cycle, respectively. After pre-wear, the RCF life of the TS sample is 4 times higher than that of the original TS sample. However, the RCF life of the P + F sample is 4 times lower than that of the original P + F sample. After pre-wear, the formation of fatigue wear cracks at the P + F sample surface causes the flaking of hardening layer and acts as a crack initiation site to accelerate the RCF failure. While the hardening layer of the TS sample is not flaked. The formation of hardening layer and the decrease of surface roughness of the TS sample improve the RCF life. During the RCF crack propagation process, the ferrite grains are refined obviously at the edge of cracks due to huge internal stress on the inner wall of the RCF cracks. The thickness of refined ferrite grains of the TS sample at the edge of RCF cracks is higher than that of the P + F sample.

Получение композитных структур при упрочнении колесной стали линейным профилем излучения иттербиевого волоконного лазера

There are presented theoretical and experimental investigations of wheel steel laser thermal treatment with the use of ytterbium fiber laser. Thermal treatment modes are obtained on the basis of the mathematical modeling preliminarily carried out of the heat propagation processes by a finite element method.

HeliRail: A railway-tube transportation system concept

Helirail is an energy efficient mass transit transportation system concept, which combines developments in low-pressure tube transport with existing high-speed railway infrastructure. It addresses the problem that, currently at low speeds, steel wheel railways are an energy efficient transport mode, however at high speeds, >80% of energy is used overcoming drag. This means minimising these resistances presents a high-impact opportunity for reducing railway energy consumption. To reduce resistance, HeliRail consists of an airtight tube-track structure that allows existing steel-wheel trains to travel on existing railway corridors where slab-track is suitable, with minimal drag. The running environment is low-density heliox gas, held inside lightweight tubes, slightly below atmospheric pressure to minimise species transport. HeliRail captures this energy saving as an operational reduction, thus improving the energy efficiency of high speed rail by 60%. On a high capacity route, annually this could save enough energy to power 140,000 homes. Deploying Helirail on an existing line does not increase train cruising speeds, however a secondary benefit is journey time reduction, achieved using a small part of the energy saving for improved train acceleration. Unlike previous evacuated tube transportation embodiments, the system is interoperable with traditional rail lines/trains meaning vehicles can pass through HeliRail sections and onto traditional steel-rail networks. This also reduces land-purchase requirements. Further benefits include improved safety compared to vacuum transportation and fewer service disruptions compared to rail. Capital cost is low compared to a new rail or pressurised transportation line, and is recovered after a period competitive with renewable energy technologies.

Corrosion Behavior of Newly Developed High-Strength Bainitic Railway Wheel Steels

High-strength bainitic wheel steels based on a new steel composition, namely MS2 [0.47% C, 0.87% Mn, 0.51% Si, 0.02% Mo, 0.03%Cu, 0.031% S, 0.033% P and rest Fe (weight percent)], were prepared by austempering treatment at 400 °C for 10, 30, 60 and 120 min. Corrosion behavior of the bainitic MS2 steels and normalized ferritic–pearlitic MS2 steel was studied and compared with that of the conventional ferritic–pearlitic wheel steel. Immersion test, electrochemical polarization and salt fog tests were carried out in 3.5% NaCl. Bainitic steels prepared with higher holding duration during austempering exhibited improved corrosion resistance on salt fog exposure. In contrast, bainitic steels prepared with lower holding duration during austempering resulted in better corrosion resistance on electrochemical polarization test. Salt fog test revealed gradual improvement in corrosion resistance for the bainitic steels with the successive holding. Improved corrosion behavior for the bainitic steel was related to the tiny and uniform spreading of iron carbide in the ferritic matrix resulting in the uniform coverage of the protective oxide layer on the steel surface. The enrichment of Si on the corroded surface of bainitic steel favored the formation of supermagnetic α-FeOOH of smaller particle size, improving the protective character of the rust against corrosion. Corrosion mechanisms for the ferritic–pearlitic and bainitic wheel steels were put forward.