Carbon Steel Rail Research Articles

Microstructure gradients across the white etching and transition layers of a heavy haul pearlitic steel

This study delves into the frequent surface cracking observed in severely damaged pearlitic carbon steel rails, a phenomenon often attributed to the challenging characteristics of the white etching layer (WEL) formed during railway operations. To explore this issue, a severely damaged rail cross-section featuring a substantial WEL layer measuring 600 μm in depth was analyzed. The WEL's size was initially determined through optical microscopy and characterized via nano-hardness testing, which revealed an impressive hardness of up to 12 GPa. High-energy synchrotron X-ray diffraction (HESXRD) analysis was employed to uncover the crystalline structure diversity gradient that resulted from railway use. The results unveiled that cumulative high-temperature surface damage leads to the formation of both the WEL and a transitional layer. Within this transitional layer, a gradual reduction in retained austenite is observed, coupled with an increase in the presence of cementite and ferrite as one approaches the base metal. Remarkably, very shallow depths from the surface display tempered martensite characteristics, characterized by high nanohardness, lower dislocation density, and an initially smaller, then increasing austenite fraction. The use of site-resolved synchrotron radiation diffraction at different depths from the surface to the interior of the damaged rail cross-section allowed a unique insight into the phase transformations, microstrain developments, and compositional evolution.

Cause analysis of surface cracks in flash butt welding joint of high manganese steel frog

Surface cracking is one of the typical failures in butt welding joints of high manganese steel railway frogs. Understanding the formation mechanism of such cracks can effectively prevent similar failures from occurring. Herein, assisted with multiple macro and micro characterization tools, we discussed the causes of surface crack formation for a flash butt welding joint of a high manganese steel frog. The results show that the surface cracks are typical intergranular stress corrosion cracks (IGSCC) distributed near the fusion line between the carbon steel rail and the stainless steel medium in the stainless steel side. Acicular martensite exists near the fusion line between carbon steel rail and stainless steel medium, and the residual stress is large. At the same time, there are continuous network chromium carbide precipitates on the austenitic grain boundary of stainless steel. The above two points should be the main reasons for the initiation of cracks on the weld surface. Reduce the proportion of martensite structure by reasonably optimizing the welding cooling rate. Properly temper martensite to reduce the hardness and internal stress in the transition zone. These measures can prevent the occurrence of intergranular cracks on the weld surface.

Failure analysis of recurrent cases of fatigue fracture in flash butt welded rails

Medium carbon steel rails are commonly jointed by flash butt welding procedures. To ensure an adequate service life for the structural component, commonly subjected to fatigue loading, a rigorous quality control should be performed, both in welding parameters and in the surface quality of the welded joint. This work investigated the causes of recurrent failures in railroads, with cracking always initiated in the rail in the region of the welded joint. Two case studies are presented. Aiming to execute the failure analysis, all standard procedures were applied, with a careful assessment of the material characteristics and the fractured surface. It was concluded that, for both cases, fatigue cracks initiated near the weld bead and spread in a brittle mode, leading to premature fracture of the material. An in-depth analysis of the rails showed that the surface finishing of the weld bead was not appropriate, generating undesirable stress concentration. Some undesirable microstructural characteristics were also found in the weld region. A recommendation to control welding parameters and to change the procedure of surface finishing of welded joints was held, aiming to decrease the number of accidents on the railroads.

Fatigue Failure of a Flash Butt Welded Rail

Medium carbon steel rails are commonly jointed by means of a flash butt welding procedure. To ensure an adequate service life for the structural component commonly subjected to fatigue loading, a rigorous quality control should be performed, both in welding parameters and in the surface quality of the welded joint. This work investigated the cause of a recurrent failure in a railway, with cracking always initiated in the rail in the region of the welded joint. All standard procedures of failure analysis were applied, with a careful assessment of the material characteristics and the fractured surface. It was concluded that fatigue cracks initiated near the weld bead and spread in a brittle mode, leading to premature fracture of the material. An in-depth analysis of the early cracks showed that the surface finishing of the weld bead was not appropriate, generating undesirable stress concentration. A recommendation to change the procedure of surface finishing of welded joint was held, aiming to decrease the number of accidents on the railway line.

The turn structure metal of rail wheel after influence of impulse electric current

The observed questions of estimate degree decrease density dislocations in carbon steel rail wheel after electrical impulse treatment.

Numerical Simulation of Flash Butt Welding of High Manganese Steel Crossing with Carbon Steel Rail

A flash butt welding model of a high manganese steel crossing was established using the thermal coupled finite element method (FEM). The model considers comprehensively the physical parameters of materials, which change with temperature, as well as the burning material caused by the splutter during welding process. The temperature field of the flash butt welding joint and the cooling curves of the high manganese steel crossing at various locations near the welding seam were simulated. Comparisons with actual welding specimens of high manganese steel crossing indicated that flash butt welding model of the high manganese steel crossing is reasonable, and the temperature field distribution near the welding seam after flash butt welding can thus be appropriately evaluated by the simulation results.

Flash butt welding of high manganese steel crossing and carbon steel rail

This study sets out to introduce the flash butt welding of high manganese steel crossing and carbon steel rail by employing an austenite–ferrite two-phase stainless steel insert. There are two flash butt welded joints for the connection of the high manganese steel and the carbon steel rail, one is the welded joint of the carbon steel and the stainless steel, and the other is that of the high manganese steel and the stainless steel. The mechanical properties and the microstructures of the welded joint are studied by means of static bending, three bend-fatigue and metallographic for the practical rail. There is no carbide precipitation on the austenitic grain boundary in the HAZ of the high manganese steel crossing subjected to jetting water cooling after the flash butt welding, and there is no martensitic transformation in the HAZ of the carbon steel rail subjected to annealing treatment by a special induction heat treatment device, which will avoid the brittleness of the welded joint effectively. The welded joint of the carbon steel rail and the stainless steel insert is annealed at 900 °C for 10 min, which will release the residual stress of the welded joint and thus enhance the strength of the welded joint. It is indicated that the flash butt welding of the high manganese steel crossing and the carbon steel rail via the austenite–ferrite two-phase stainless steel insert is feasible.

A Laboratory Investigation of Threshold Stress in Wheel/Rail Interaction for Heavy Axle Loads

This study is a continuation of earlier investigations to determine acceptable upper bound of contact stresses (threshold stress) for new wheel and rail under heavy axle load conditions. Using sharply increased wear rate (as initial maximum contact stress increases) under free rolling conditions as an indicator of threshold stress, laboratory investigations of wheel-rail rolling contact wear, simulating the 125-ton car wheel load, were conducted. Tangent track conditions with clean and dry surfaces were tested on two facilities; one of one-quarter scale and the other of one-fifteenth scale wheel-rail simulation. The earlier experiments conducted in the IIT Railroad Engineering Laboratory to investigate threshold stress used a varying load with the same wheel-rail profiles, the present study used constant load with varying wheel-rail profiles to determine whether the above increase in wear rate phenomenon will still be observed. While the results of the small (1/15th) scale facility were not considered quantitatively conclusive because of small size, qualitatively they indicated the presence of threshold stress phenomenon. The results of the one-quarter scale test facility very clearly confirmed that there is indeed a threshold stress above which the rolling contact wear rates increased sharply. The value of this stress, found to be approximately the same as reported in the earlier study, was nearly 200 ksi (for standard carbon steel rail). From the earlier and the present investigations of threshold stress, it is clearly concluded that the increased wear rates are primarily due to the increased initial contact stresses and 200 ksi is the value of threshold stress for standard carbon steel rail. Initial wheel-rail contact stresses for new wheel-rail should not be allowed to exceed this value to reduce damage to rail for heavy axle loads. It is recommended that new wheel-rail profiles should be developed to achieve stresses at or below this threshold stress level. Benefits of improved rail life with this approach are also discussed.

The Increasing Demands on the Serviceability of Rail Steels

Increasing freight car weight, an unbroken upward trend for the past 20 years, has placed new and severe demands on railway rails. The recent performance and metallurgy of carbon steel rails are reviewed, and projections of its future behaviour are made using the Canadian Institute for Guided Ground Transport (CIGGT) wear and AAR fatigue models.The metallurgical development and performance of improved fine pearlitic heat-treated and alloy rail steels are discussed in respect to their comparative behavior on heavy-haul Canadian and Australian mining railroads with general North American Freight Service.The metallurgist engaged in the development of rail steels will therefore be presented with a set of goals and requirements for the direction of his work. Résumé Le poids augmente des wagons de marchandises a la hausse depuis 20 ans, fait les exigencies nouvelles et rigoureuses sur les rails du voies ferreés. Le comportement recente et la metallurgie des rails en acier au carbone sont passe en revue, et des previsions des possibilites de ce materiau sont faites, d'apres un modele de l'usure propose par le Canadian Institute for Guided Ground Transport (CIGGT) et un modele de la fatigue propose par l'AAR.Le developpement metallurgique et le comportement des aciers a rail traites thermiquement, ou d'alliage, a perlite fine, sont discutes afin de comparer leur comportement sous les poids lourds des routes ferroviaires des compagnies minieres Canadiennes et Australiennes, et dans le service normal de fret en Amerique du Nord.Nous presentons donc, au metallurgiste qui travaille dans le developpement des aciers a rail, des buts et des exigences pour diriger ses travaux.

高マンガン鋼クロッシングと炭素鋼レールとの自動溶接 溶接法の改善と溶接部の諸性質

A study was made about automatic welding method in order to join carbon steel rail to high Mn steel crossing.When a continuous welding under electro-gas welding method was made, there appeared transverse cracks at heat affected zone of high Mn steel.The main cause of these cracks was supposed to be micro-shrinkage and severer britteleness than expected. Further, there appeared slag inclusion in electro-gas weld. And so, an intermittent welding was tried next. Togther with everlasting water cooling welded part of high Mn steel is cooled per each 1 layer 3 pass welding cutting arc. Therefore, a curved type torch epuipped with automatic swinging device was manufactured.The toughness of heat affected zone of high Mn steel by 1 layer 3 pass procedure is equal to that of shielded metal arc weld which has already been employed as practical application.Concerning the special features the results of fatigue test are the same as those of the enclosed welding of carbon steel rail.About shock test, there proved to be sufficiently ductile at the weld.

Quality of carbon and chromium steel rails

Quality of carbon and chromium steel rails

高マンガン鋼と高炭素鋼との溶接(第2報)

In report 1, the manual arc welding of austenitic manganese steel to high carbon steel was studied, the main characteristic of which was to butter, before joining, the groove face of high carbon steel with austenitic covered electrode.This paper describes the results of some experiments on welding of the above two dissimilar metals by gas shielded arc welding process.To select appropriate welding wire and welding conditions for buttering, single bead weld test and FISCO cracking test were made using high carbon steel as base metal, five austenitic welding wire as electrode, and CO2, CO2-A, A or N2 as shielding gas.16 Mn-16 Cr and 25 Cr-20 Ni welding wire are available for buttering electrode and CO2-A for shielding gas from the viewpoints of weld metal hardness, microstructure, weld defects and crack susceptibility of weld metal.Carbon steel rail and austenitic manganese steel rail (50 PS type) were then welded together automatically by gas shielded arc welding process: The groove face of the former was buttered vertically with above-mentioned wires and shielding gas and rail welding apparatus, which could be used not only for rail joining by welding but also for buttering with some modifications. An austenitic manganese steel rail was welded to the buttered carbon steel rail with I-groove and almost the same welding conditions as in the case of gas shielded arc welding of austenitic manganese steel rails investigated previously by the authors. The values of maximum load and deflection in bending tests of welded rails were 75-85 t and 56-84 mm with head-up (span 1 m, load applied at mid span) and they are almost equal to the welds by manual arc welding with V-or I-groove joint.Welding takes about 11 minutes for buttering and 7.5 minutes for joining.

高マンガン鋼と高炭素鋼との溶接(第1報)

The welding of austenitic manganese steel to high carbon steel has been thought to be very difficult due to the difference of their metallurgical properties and others. The authors paid special attention to the procdeure to join them by manual arc welding after buttering the groove face of carbon steel. Various fundamental experiments were performed to select proper electrodes for buttering and joining, and welding conditions, though mention here is given mainly of the buttering electrode selection tests- 1) Hardness test and microscopic inspection of weld metal, 2) Angle-expanding type cracking test of weld metal and, 3) Impact test of weld zone.Based on the results obtained, austenitic manganese steel rail and carbon steel rail (high carbon steel) were welded together, and the welded rails were subjected to bending test, drop-weight test and so forth. The results show that considerably reliable welds are obtained if they are welded together by the following methods: 1) Austenitic manganese steel which has good weldability and no casting defects is used. 2) The welding groove is finished to V or X and arc welding process is executed in flat position. 3) The vicinity of the groove of carbon steel is preheated to 300-400°C, then two layers with 25Cr-2ONi or 25Cr-12Ni type electrodes or one more layer with 16Mn-16Cr type electrodes are buttered over the groove face. 4) The manganese steel rail and the buttered carbon steel rail are welded together with 16Mn-16Cr electrodes. Craters are peened after each pass followed by forcible cooling of the weld zone. 5) The impurities contained such as phosphorus should be as low as possible in the electrodes and the electrodes should give weld metals of very low crack susceptibility. 6) The postheating which is usually adopted for the welding of high carbon steel is not performed.The final object of this study is to establish the prodceure to weld austenitic manganes steel crossing to carbon steel rail and the welds are now under field test.

On the Abrasion Test of Carbon-Steel (Rail and Tyre) After Hardened by Means of High Frequency Induction : The 3rd Report, Contrast of indoor-test and octual of railroad

In the first and second reports, the author described a result of test on a method of prevension of wear on both rail and tyre. In this test, hardened rail was watched against unhardened tyre or hardened tyre against unhardened rail, under both dried and lubricated conditions, and an amsler testing machine was used. In the present report (3rd report) the author compared the test result mentioned above with the octual condition of wear of the rail and tyre and the following results have been made clear : 1. Under a dry condition, if both rail and tyre are not hardened, a very similar result was shown in both of them. 2. In other cases, the tendency can be concluded. 3. At present condition of railways, these preventitive methods against wear are not completely put in force.