Wheel Steel Research Articles

Evaluation of polygonization resistance of two wheel steels from full-scale railway wheels and small test discs

Polygonization of railway wheels poses a significant challenge for the wheel-rail system. Despite the evidence from engineering practices highlighting the substantial impact of material factors on the polygonization resistance of railway wheels, research in this field remains limited. This study investigates two types of railway wheels, namely non-alloyed and alloyed wheels, which demonstrate different polygonization resistance under identical operating conditions. It involves microstructural analysis and hardness testing for the matrix materials and plastic deformation layer (PDL) of full-scale wheel, twin-disc testing for wheel steels, followed by analyzing the PDL of test wheel discs. The findings demonstrate that the full-scale wheel and test wheel disc exhibit consistency in terms of polygonization resistance, PDL microstructure, and microhardness, suggesting that the twin-disc test can be employed for material comparison regarding polygonization resistance. In addition, the alloyed wheel was found to exhibit better polygonization resistance at the external region of the wheel rim due to its higher resistance to plastic deformation and wear, while it demonstrates poorer polygonization resistance at the internal region of the wheel rim due to its lower wear resistance. Furthermore, the wave troughs display significant plastic deformation, dynamic recrystallization, and strain hardening near the contact surface, indicating a higher slip ratio at these locations. In contrast, the wave crests predominantly exhibit these characteristics in the subsurface region, indicating that the wave crests experience impact loading.

Experimental study of wear and rolling contact fatigue in railway wheel steels coupled with various brake block materials: Insights from innovative small-scale testing

This study presents a comprehensive analysis using an innovative testing method of two wheel steels paired with cast iron and organic composite brake block materials. By conducting tests under consistent conditions and varying in duration, the study examines temperature profiles, friction coefficients, surface characteristics, weight loss, and microstructural changes in wheel samples, emphasizing the distinct behaviour of these materials in braking applications and the damage evolution over time. The results demonstrate that organic composite brake samples outperform those in cast iron, showcasing smoother wheel sample surfaces and stable friction coefficients. Weight loss analysis reveals the environmental benefits of organic composite brakes, emitting fewer particulates than cast iron counterparts. Microstructural examinations uncover the formation of a Thermal White Etching Layer (T-WEL) on wheel samples tested with cast iron samples, leading to cracks and material detachment. Conversely, extended use of organic composite samples led to a "thermal fuse effect", impacting their efficiency and suggesting the need of careful temperature management in sustained braking scenarios. Despite significant differences in wheel steels, the study underscores the critical role of brake material in braking improvements. The findings not only enhance the scientific understanding of brake material behaviour but also introduce an innovative, cost-effective, and fast 4-contact machine testing method.

Characteristics, Formation Mechanism, and Removal of Large‐Sized CaO–Al2O3–SiO2 Inclusions in D2 High‐Speed Railway Wheel Steel

Characteristics, Formation Mechanism, and Removal of Large‐Sized CaO–Al₂O₃–SiO₂ Inclusions in D2 High‐Speed Railway Wheel Steel

Finite Element Simulation and Microstructural Analysis of Roll Forming for DP590 High-Strength Dual-Phase Steel Wheel Rims.

In this study, finite element (FE) simulation by the software Abaqus was relied on to investigate the roll forming process of a wheel rim made of an innovative dual-phase steel, i.e., DP590, after flash butt welding (FBW). In the simulation, an FE model was generated, including the design of the dies for flaring, three-roll forming, and expansion, and detailed key processing parameters based on practical production of the selected DP590. Combined with the microstructures and properties of the weld zone (WZ) and heat-affected zones (HAZs) after FBW, the distribution of stress/strain and the change in thickness of the base metal (BM), WZ and HAZs were analyzed, and compared in the important stages of roll forming. Theoretically, the variation in the microstructure and the corresponding stress-strain behaviors of the BM, WZ, and HAZs after FBW have led to the thickness reduction of DP590 that originated from softening behaviors occurring at the region of subcritical HAZs (SCHAZs), and a small amount of tempered martensite has evidently reduced the hardness and strength of the SCHAZ. Meanwhile, the distribution of stress/strain has been influenced to some extent. Further, the study includes the influence of the friction coefficient on the forming quality of the wheel rim to guarantee the simulation accuracy in practical applications. In sum, the dual-phase steel has to be carefully applied to the wheel rim, which needs to experience the processes of FBW and roll forming, focusing on the performance of SCHAZs.

An Alternative Method of Investigating the Thermal Stability of Shoe-Braked Railway Wheel Steels Based on Strain Hardening Analysis

During service, shoe-braked railway wheel steels are often subjected to a severe thermal cycle. Therefore, understanding the evolution of the microstructure and the resulting changes in mechanical properties during service is fundamental in the choice of steel. In previous research, the effects of the thermal loading on the microstructure and mechanical properties of five different steels for railway wheels (ER7, HYPERLOS®, Class B, SANDLOS® and Class C) were investigated by hardness, tensile and toughness tests, in the as-supplied condition and after different heat treatments designed to replicate the modification of the microstructure due to braking. In this paper, the tensile work hardening behavior was studied by interpolating the tensile flow curves with the constitutive equation related to the dislocation density proposed by Voce, which correlates the Voce equation parameters with the microstructural features of metallic materials. The work hardening analysis revealed that there is a good correlation between the Voce parameters and the microstructure of the five steels in as-supplied condition and after heat treatments. An interesting correlation was found between Voce parameters and apparent fracture toughness. After heat treatments at 700 °C and 750 °C the properties of the steels decreased, which was consistent with the evolution of the microstructure. However, after exposure at 970 °C with subsequent cooling in air, Class C steel appears to have a microstructure similar to the original microstructure, with tensile and toughness properties very similar to the as-supplied condition, demonstrating better microstructural stability compared to steels ER7, HYPERLOS®, Class B and SANDLOS®.

Structural computational analysis of conventional and self-designed rover wheel architectures for extraterrestrial roving application

The technical advancements in robotics have closely been followed by developments in aerospace excavation robots. This research elucidates self-designed shape memory alloy wheels for their use in Lunar Excavations, which attributes to the new era of space exploration robots. The wheel design proves to be of paramount importance as crucial operations such as mobility, steering, and traction control build upon wheel design. A comparison has been made between Aluminium alloy, Structural Steel, and Shape Memory alloy (Nitinol) wheels for both conventional and self-designed wheel architectures. Wheel architecture tests and their results are articulated with the aid of simulation. The significant performance parameters, primarily Total Deformation, Equivalent Stress, and Shear stress-induced, were analyzed, which articulates the performance of the wheel at the time of landing. It was observed that for both wheel designs: self-designed and conventional, the maximum total deformation was 0.011154 mm and 1.3573 mm, respectively, when Aluminium alloy was chosen as the base material. For Steel and Nitinol, the self-designed wheel structure proved to perform better than the conventional wheel design with lower values of total deformation (0.0041129 mm and 0.010968 mm, respectively).

Design of Quenching and Tempering Process and Elucidation of the Relationship between Microstructure and Properties of 20Mn2SiNiMo Bainitic Wheel Steel

The rapid development of train transportation toward higher speed and heavier load requires superior wheel materials with high strength and toughness. Herein, a 20Mn2SiNiMo bainitic wheel steel is developed and bainitic wheels are produced. The quenching and tempering process of bainitic wheels is studied considering the bainitic ferrite content and stability of retained austenite (RA). The quenching process includes water spraying and air cooling. Proeutectoid ferrite can be suppressed during the water‐spraying process. During air cooling, the bainitic ferrite transformation is promoted and the stability of RA is improved with the extension of cooling time. Corresponding microstructure of as‐quenched steel at wheel rim is bainite with different morphologies, martensite, and RA. The evolution of RA at lower and higher tempering temperatures is dominated by carbon enrichment and carbon consumption, respectively. Yield strength of bainitic wheel steel mainly comes from body‐centered cubic phase (containing martensite and bainitic ferrite). The increase of dislocation density and the decrease of effective grain size are beneficial for yield strength improvement. Bainitic packets with various direction, deformation‐induced martensite transformation of RA, and plastic deformation all play an important role in enhancing the toughness of bainitic wheel steel.

Optimal Process Parameters for FDM‐Based 3D Printing of Metal‐Polymer Mixtures with Low‐Temperature Powder Feeding

In this study, a proprietary powder‐fed 3D printer is employed to fabricate impellers from metal‐polymer mixtures via low‐temperature extrusion, simplifying the traditional complex metal molding process. By adjusting the extrusion speed and temperature, various quality impeller blanks are produced, identifying optimal printing conditions. The best results are achieved with a feed temperature of 170 °C, extrusion speed of 6 r min−1, printing platform temperature of 50 °C, and nozzle temperature of 175 °C, achieving a surface roughness of Ra = 9.973 μm. Post‐processing densification of the stainless steel wheels reach 97.23%, with a tensile strength of 255 MPa, elongation at break of 49%, and hardness of 60 HRB. These parameters meet the physical and mechanical standards required for general metal parts, demonstrating potential for precision metal processing in sectors such as aircraft engines, gas turbines, and high‐performance pumps.

Study of strength and toughness in pearlitic wheel steel via microstructural alteration

The present study investigates a thorough effect of composition, processing, and microstructure on the mechanical property counterpart of pearlitic wheel steel. Optical and scanning electron microscopes along with the ImageJ software are used to capture and quantify the microstructures. Mechanical properties such as hardness, tensile properties, and fracture toughness (K1 C) were measured for all the studied steel. The chemical composition along with the heat treatment parameters are varied in the plant scale processing schedule. It was observed that the volume fraction of ferrite, prior austenite grain (PAG) size and distribution, and pearlite hardness are the most important factors, affecting the strength-toughness combination in the wheel steel. The carbon equivalent and cooling rate are two important factors for the enhancement of tensile strength. The fracture surface investigated under the electron microscope represents the ductile ridges along with the cleavage facets owing to the presence of ferrite allotriomorphs along the PAG and pearlite matrix, respectively. The crack study in the secondary fracture plane shows that the deflection and arrest of cracks were taking place preferentially in the ferrite grain boundaries as well as non-lamellar pearlitic domains.

The role of microstructure on the wear and rolling contact fatigue of railway steels: The performance of bainite

This study aims to describe the wear and rolling contact fatigue (RCF) behavior of microalloyed forged railway wheel steel Class D (7NbMo), with microstructures of upper bainite (UB - 350 HV0.5), lower bainite (LB - 450 HV0.5), and pearlite (PE - 350 HV0.5), against 7C steel with a tempered martensite microstructure (660 HV0.5) in a twin-disc tribometer. The results showed that bainite (LB and UB) exhibited greater wear resistance compared to pearlite (PE). The primary wear mechanism for all three microstructures was the fatigue wear. An analysis of the PE disc revealed continuous (single-layer) RCF cracks, which were relatively large and deep. In contrast, UB and LB cracks were discontinuous (multiple layers), thin, and smaller but more numerous (higher crack density). These characteristics indicated that bainitic microstructures also had greater resistance to RCF than pearlite did. Therefore, the combination of mechanical properties and the morphological arrangement of the microstructure led bainite to develop a shallower depth of deformed layer with a higher capacity for plastic deformation per unit volume. The greater wear and RCF performance of bainite compared to those of pearlite may be associated with how they release the accumulated deformation energy after reaching saturation in relation to volume deformation absorption: regarding bainite, the material releases energy by opening crack surfaces; conversely, regarding pearlite, it is through the detachment of large and wide cracks.

Impact of sand feed rate on the damage of railway wheel steels

The global railway industry plays a pivotal role in economic development, offering efficient transportation solutions. However, railways operating in desert environments face unique challenges due to windblown sand. This study investigates the influence of sand feed rates on wheel-rail wear in desert conditions. Experimental tests were conducted using a bidisc apparatus to simulate sand feed rates. Results indicate that low feed rates lead to spalling and pitting, while high rates increase abrasive and fatigue wear. A critical transition point at 0.4 g/min suggests sand-induced abrasion of wheel surfaces. Moreover, the research highlights the crucial role of sand feed rates not only in wear but also in surface roughness, further emphasizing the complex interplay between sand transport rates, adhesion, and wear mechanisms. These insights provide valuable guidance for mitigating wear-related challenges in desert railway operations and optimizing maintenance strategies.

Rapid evaluation of trade-offs between strength and impact toughness of wheel steels by instrumented spherical indentation test

In this paper, an improved size-independent instrumented spherical indentation test (ISIT) method was proposed to determine tensile strength and fracture toughness on wheel rims of two different types of wheel steels. Additionally, Charpy impact specimens were taken from three specific positions on the wheel rims and subjected to standard Charpy impact testing. The resulting Charpy impact energy (CVN) were matched with the fracture toughness measured by ISIT (KIc,IT) at the same positions. There was a clear linear correlation between CVN and the square of KIc,IT, which was consistent with the established relationship between both properties as determined by conventional Charpy impact and compact tension tests. Therefore, we expanded the ISIT method to study the impact of cooling rates on the variation of yield strength and Charpy impact energy across the wheel rim. To accomplish this, we designated additional testing points on the wheel rim using the ISIT method. The investigation found trade-offs between strength and impact toughness of wheel steels under different cooling rates. The above findings demonstrated the effectiveness of using the ISIT method, which facilitated high-resolution fracture toughness measurement, to establish accurate correlation between CVN and fracture toughness of wheel steels. Moreover, this ISIT method can be employed to regulate heat treatment of material properties to meet specific application requirements.

Characteristics and Formation Mechanism of Oxide–Sulfide Complex Inclusions in High-Speed Railway Wheel Steel

Characteristics and Formation Mechanism of Oxide–Sulfide Complex Inclusions in High-Speed Railway Wheel Steel

Effect of Rare Earth on the Occurrence Characteristics of Inclusions in High-strength Wheel Steel

Effect of Rare Earth on the Occurrence Characteristics of Inclusions in High-strength Wheel Steel

Examining Wear Mechanisms in Railway Wheel Steels: Experimental Insights and Predictive Mapping

Railway systems play a pivotal role in modern transportation networks, contributing to both efficiency and environmental sustainability. This study investigated the multifaceted aspects of wear phenomena in railway engineering, focusing on their significant implications for environmental costs and operational efficiency. Experimental trials were conducted using a high-performance bi-disc apparatus, evaluating a range of materials, contact pressures, and lubrication conditions. Shakedown maps were employed to assess ratcheting behaviour, while the wear rate was analysed as a function of the fatigue index (FI). The results reveal the intricate interplay of contact pressure, slip ratio, material properties, and lubrication in determining wear and ratcheting behaviour. Oxidative and mild wear mechanisms were identified, and wear debris composition and morphology were characterised. The outcomes from this research clarify the pivotal role that wear processes play within railway systems and the far-reaching environmental repercussions they entail. This exploration contributes to the ongoing optimisation of railway operations, offering valuable insights aimed at mitigating unavoidable pollution sources and strengthening sustainability efforts. By delving into the intricate dynamics of wear phenomena within wheel–rail material, this research paves the way for innovative solutions that not only enhance operational efficiency but also minimise the ecological footprint of railway transportation.

ТЕХНОЛОГИЧЕСКИЕ МЕТОДЫ УВЕЛИЧЕНИЯ ДОЛГОВЕЧНОСТИ КОЛЕС ПАССАЖИРСКОГО ЖЕЛЕЗНОДОРОЖНОГО ВАГОНА

The cut of passenger cars due to wear damage to the rolling surface of the wheelset in 2022 is considered. It is found out that the most typical damage is a shelled tread. An analysis of the methods for restoring the rolling profile of wheels showed that the wheel milling with an end mill can be used as a promising one. To assess the effectiveness of the method, metallographic and tribological studies of wheel samples subjected to turning and milling are compared. According to the study results, it is found that when machining samples of wheel steel by end milling, their wear resistance is 22% higher, compared with samples machined by turning, the wear rate of samples of rail steel is lower in a friction pair with milled samples than with turned samples due to a decrease in the friction factor of milling samples.

Enhancing Steel Wheel Ventilation Efficiency Through Multi-Objective Optimization

This study focuses on the optimization of ventilation hole design in steel wheels used for heavy commercial vehicles. The primary objective is to reduce the weight of the wheel while ensuring compliance with radial fatigue and cornering fatigue test requirements. Four distinct ventilation types were parametrized using ANSYS Mechanical, with the von Mises stress on the disk, number of ventilations, and wheel weight serving as design parameters. Stress analysis and weight comparisons were performed between wheels featuring different ventilation types and an ellipse ventilation wheel. Incorporating the design of experiment (DoE) and response surface optimization (RSO) module in ANSYS Workbench 2022 R1 was employed to compare and evaluate the obtained values. Subsequently, the multi-objective genetic algorithm (MOGA-II) method was employed for optimization, aiming to identify the optimal design. The optimization process, utilizing a maximum of 20 iterations, a convergence stability percentage of 2%, and a maximum allowable Pareto percentage of 70%, yielded 1, 3, 3, and 3 candidate design points for round, slot, trapezoid, and halfmoon-type ventilation holes, respectively. Among the various ventilation types considered, the halfmoon-type ventilation hole exhibited the most promising results. Compared to the current design, the optimized wheel achieved a weight reduction of 0.9 kg (2.05%). This outcome demonstrates the effectiveness of the proposed methodology. Although lighter designs were not attainable while maintaining the same stress values for the other three ventilation types, the halfmoon-type ventilation hole was ultimately selected as the preferred design.

Effect of screw piercing on the structure and mechanical properties of a continuously cast blank made of wheel steel

Effect of screw piercing on the structure and mechanical properties of a continuously cast blank made of wheel steel

Rolling contact fatigue and wear behavior of a vanadium microalloyed railway wheel steel under dry rolling/sliding condition

This study aims to evaluate the effect of vanadium microalloying on rolling contact fatigue (RCF) and wear behavior of railway wheel steels. It involves microstructural analysis and mechanical testing, including hardness, tensile, and rolling/sliding tests on the test steels, followed by electron backscatter diffraction, residual stress, and microhardness analyses after rolling/sliding tests. The findings demonstrate that vanadium microalloying leads to the alleviation of dynamic recrystallization, strain hardening, and compressive residual stress within the outermost layer beneath the worn surface, indicating a reduction in the plastic deformation capacity during dry rolling/sliding conditions. RCF resistance of railway steel can be enhanced through vanadium microalloying, as it simultaneously delays crack initiation by increasing yield strength and restricts crack growth by reducing plastic deformation capacity. While vanadium microalloying enhances the matrix hardness of wheel steel, it concurrently diminishes its strain hardening ability, potentially compromising its wear resistance. In addition, this study found that the yield ratio, being indicative of plastic deformation capacity and strain hardening ability, can serve as a suitable parameter for characterizing the RCF and wear resistances of tested steels. It exhibits a positive correlation with RCF resistance and a negative correlation with wear resistance.

Influence of thermal loading parameters and microstructure on the formation of stratified surface layers on railway wheels

Due to an increasing trend towards environmentally friendly public transport, rail networks face higher speeds and wheel loads affecting the material degradation of the railway components. Within this study, influencing parameters on the formation of stratified surface layers, forming on railway wheels during service due to thermal loadings in the wheel-rail contact, are studied. These layers consist of white etching layer and underlying brown etching layer and are susceptible to fatigue crack initiation. By using laser surface treatments, its formation based on two consecutive thermal loadings is systematically demonstrated on ER7 wheel steel. Further, a decrease in layer thickness with decreasing laser power, and an increase in brown etching layer thickness with increasing laser power difference is shown. Moreover, the effect of finer grain size leading to an increased layer thickness, and the influence of the chemical composition by comparing the standard ER7 wheel steel to a micro-alloyed wheel steel are demonstrated.