Steel R18 Research Articles

EBSD study of early-damaging phenomena in wheel–rail model test

In the early-damage regime of rails subjected to rolling contact fatigue, the material undergoes severe plastic deformation forming a modified sub-surface microstructure. This zone close to the surface determines subsequent fatigue properties of the whole component and can differ considerably from an initial microstructure of the same material. Therefore, a fundamental understanding of early damage phenomena (<4000 cycles) is the focus of this work by comparing exemplary as a rolled standard R260 steel with a surface finished R260 pearlitic steel regarding their response to the rolling stresses by plastic deformation. Thus, electron backscatter diffraction technique based results were used to describe the material modification and set up a model for early-damage response of a pearlitic rail steel. Thereby, increased plastic deformation was found in the decarburized zone already after 100 cycles while the surface finished R260 remains almost undeformed. After 4000 cycles, both specimens have undergone high plastic deformation with work hardening concentrated directly below the surface for the decarburized steel and up to higher depths in the surface finished one.

OPTIMIZATION OF MECHANICAL CHARACTERISTICS OF STEEL AND ALLOYS BY NANOSTRUCTURIZATION OF THEIR DEFECT STRUCTURE AT THE BORDER OF PHASE PRETRANSFORMATION WITH THE USE OF ACOUSTIC EMISSION METHOD

The influence of the duration of stay of the steels 30HGSA and R18 as well as titanium alloy VT 20 in the conditions of polymorphic pretransformation and transformation conditions on the mechanical properties is investigated. It is shown that the effect of phase pretransformation allows in wide range controlling the steel defect structure and mechanical properties. The “operation” at polymorphic transformation border promotes to regulate the defect structure density and to optimize mechanical properties of alloys. It is proposed to use the acoustic emission method for phase transformation stage detection and for the development of heat treatment technology with maximize use of the phase pretransformation effects.

Influence of Pearlite Morphology on Creeping Characteristic Curves of R260 Steel

The elements of railway turnouts made from rail sections of R260 high carbon steel must have a high resistance to abrasive and contact fatigue wear, as well as a good resistance to cracking under service loads. These mechanical properties largely determine the suitability of steel for use as railway track components. In this study, two groups of specimens were subjected to tests of mechanical properties and metallurgical analyses. The first group included material obtained from the hot-rolled block section, the rolling end temperature being Tkw = 950°C, while the second group was material after the rolling process with the subsequent 20-minute isothermal annealing at a temperature of 480°C. The microstructure of tested materials (Rm, Rp0.2, A5, Z, HB) was characterized, and their basic mechanical properties and fracture toughness in the KIc plane strain condition were determined. Also the effect of temperature, ranging from-80°C to 100°C, on the KCU impact toughness of R260 steel was established. Based on the SEM observation using the Hitachi S-3400N scanning microscope, it was found that pearlitic structure with a varied distance between cementite plates, equal to 0.29 μm and 0.09 μm, respectively, appears in the hot-rolled R260 steel and in the steel subjected to additional isothermal annealing treatment. The impact of pearlite morphology on the cracking characteristics and basic mechanical properties of materials was analyzed. It was found that at room temperature, the higher fracture toughness (KIc = 66.4 MPa·m1/2) is shown by the steel after isothermal annealing at 480°C, in which less distance between the plates of cementite has been observed in the perlite. The fracture toughness of R260 steel after hot rolling at 950°C was KIc = 48.3 MPa·m1/2. As in the case of fracture toughness, the impact strength of R260 steel after isothermal annealing was significantly greater than the impact strength of steel only after hot rolling. The determined cracking characteristics of R260 steel make it possible to determine the effect of heat treatment on the formation of microstructure and material properties, which determine the service life of rail sections.

The structure, properties and a resistance to abrasive wear of railway sections of steel with a different pearlite morphology

The article presents the characteristics of pearlite rail steels used in the construction of railways. The article discusses the influence of isothermal annealing process parameters on the pearlite morphology and properties of the R260 steel. The pearlite structure with a diverse pearlite morphology was obtained in the physical modeling of the isothermal annealing on the 3800 Gleeble Simulator. After the heat treatment, the existence of the pearlite microstructure with pearlite colonies was identified. They were smaller in relation to colonies after the hot rolling process. It was shown that the reduction of isothermal holding temperature influences the decrease of the interlamellar distance in the pearlite steel. On the basis of the received results, the dependences between the resistance to the abrasive wear and the pearlite morphology for operational conditions occurring in the switches were estimated. The resistance to the abrasive wear tests were conducted for steel with a different morphology of pearlite on the Amsler stand in conditions of rolling- sliding frictions. The resistance to the abrasive wear of R260 steel with a different pearlite morphology increases, when the interlamellar distance in cementite decreases and decreases as the load and slip increase.

Simulation of wheel–rail contact and damage in switches &amp; crossings

A methodology for the simulation of degradation of rail profiles in switches & crossings (S&C) is presented. The methodology includes: simulation of dynamic vehicle-track interaction considering stochastic variations in input data (such as wheel profile, train speed and wheel-rail friction coefficient), simulation of wheel-rail contacts accounting for non-linear material properties and plasticity, and simulation of wear and plastic deformation in the rail during the life of the S&C component. The methodology is demonstrated by predicting the damage of a switch rail profile, manufactured from R260 steel, when exposed to freight traffic in the diverging route (facing move). In particular, the consequences of increasing the axle load from 25 tonnes to 30 tonnes are studied.

High speed broaching of hard machining materials

Materials have been broaching on various speeds of cutting are presented. Comparative research of influence the traditional broaching on low speeds of cutting (V = 2 m/min) by the broaches from high speed steel R18 and the high-speed broaching (V = 26 m/min) by the hard-alloy broaches VK8 on the change of intensity of wear of the broaches and formation of key parameters of quality of a superficial layer – a roughness and fatigue durability. Introduction of the high-speed broaching promotes the receipt of higher and stable parameters of quality of a superficial layer, increase of fatigue durability, reliability and a resource of gas-turbine engine parts and the minimal values of the tool wear intensity.

Effect of Continuous and Isothermal Hardening on the Wear Resistance of Tools Produced from High-Speed Steels

The effect of isothermal hardening on the red-hardness (heat resistance) of steel R18 is studied. A complex dependence of the red hardness on the temperature of isothermal hardening and the hold time is shown. Tools from steel R18 are shown to have maximum heat resistance and wear resistance after bainitic hardening in the “pre-transformation” range.

Vacuum Heat Treatment of High-Speed and Corrosion-Resistant Martensitic Steels

Corrosion-resistant steels EI961-Sh (TU 14-1-1239–75), EP479-Sh (TU 14-1-1434–75) and high-speed steel R18 were quenched in vacuum furnaces with cooling in a medium of circulating inert gas (argon) at a pressure of 0.6 105, 105, 5.5 105 Pa. For comparison, the properties of steels EI961-Sh and EP479-Sh were studied after heat treatment in chamber furnaces with an oxidizing medium. The tested specimens of steels EI961-Sh and EP479-Sh were 10, 30, and 50 mm in diameter; the specimens of highspeed steel R18 were 6, 8, 10, and 14 mm in diameter. In order to simulate full charging, the specimens were charged into the furnace together with ballast pieces with the corresponding cross section. The heat treatment regimes are presented in Table 1. In order to estimate the cooling rate in quenching, the control thermocouple was calked in the center of the specimens with maximum cross section. The cooling rate was calculated from the diagram of the control thermocouple in the temperature range of carbide segregation (1000 – 500°C) for steels EI961-Sh, EP479-Sh and at 1000 – 550°C for steel R18. The quality of the treatment was estimated in terms of the mechanical properties r , 0.2 , , , KCU, the HRCe hardness, and the microstructure; fracture surfaces of impact specimens were examined visually.

Using a vertical vibration mill for refining and mixing components of a carbide steel

The Ukrainian Scientific Research Institute of Special Steels (Zaporozh'e) has developed a technology of production of carbide steel—a composite material for cutting tools. When using this material, the durability of tools increases 2–5 times, in comparison with steels R18, R6M5F3, R6M5K5, and R9K5. Industrial tests of punches in cutters for mining combines, hydraulic monitor attachments, drilling bits, and deforming dies of carbide steel have shown that their durability is close to the durability of hard alloys while their production costs are lower.

The influence of oxygen on the properties of a titanium nitride-base coating

In application of titanium nitride-base coatings entry of oxygen into them is possible with use of low purity nitrogen or with insufficient vacuum. In service during heating in air oxygen also reacts with the coating material. In this work the influence of oxygen on the structure and properties of a titanium nitride-base coating on an R18 steel base was investigated. A method of application of a titanium nitride-base coating with optimum service properties on a tool is proposed.

Study of the chemical composition of the surface of high-speed steel specimens with a coating based on titanium nitride after the action of heat

1. With long-term heating in a vacuum of specimens of high-speed steel R18 with a coating based on titanium nitride applied by means of ion plasma technology diffusion processes of mass transfer are realized in the coating-substrate system. 2. With short-term high-speed heating two regions are observed in the coating: an outer region enriched with oxygen and impoverished in nitrogen and carbon, and an inner region with the opposite ratio of elements. Oxygen enters from the surrounding atmosphere and carbon enters from the substrate material. 3. Additional short-term heating makes it possible to control processes of forming the compound TiNxOyCz of prescribed composition which makes it possible to improve the operating properties of tools and to optimize the technology for treating materials.

Combined bulk and laser heat treatment for optimizing the structure and phase composition of high-speed steels

The influence of laser radiation on the formation of an austenitic grain and on the alloying ability of a solid solution of high-speed cutting steels is investigated using as an example the steel R18 subjected beforehand to various bulk heat treatments. Notice is taken of the role of laser tempering during the initial stage of heating to the temperature at which an austenitic transformation with release of secondary carbides takes place, accompanied by laser action of plastic de formation with formation of a corresponding structurally stressed state. The content, in the solid solution, of the main alloying element tungsten in the R18 high-speed steel is determined from Mossbauer measurements and from x-ray phase analysis data on the degree of the dissolution of the carbide phase in laser-action zone. Determination of the carbon content in the solid solution of the zones of laser action, yields data on the degree of the carbide-phase solution and on the displacement of the diffraction α-lines; these data can be attributed to anomalous diffusion of the carbon as the laser heating is accelerated.

Use of powdered steel ROM2F3S-MP for high pressure fuel pump injector nozzle needles

1. The possibility has been established in principle of substituting high-tungsten steel R18 by tungstenless powder steel ROM2F3S-MP. 2. Steel ROM2F3S-MP provides an acceptable level of grindability in preparing atomizer needles by the grinding method, and in their service characteristics atomizers with needles made of steel ROM2F3S-MP are as good as series atomizers with needles made of steel R18.

From steel R18 to tungstenless low-alloy high-speed steels

From steel R18 to tungstenless low-alloy high-speed steels

Hypereutectoid high-speed steels

Half of the tungsten and molybdenum contained in R6M5 and R18 steels is concentrated in the undissolved eutectic carbides hindering austenitic grain gowth in hardening and providing the necessary strength and impact strength. This article describes the tungsten-free low-alloy high-speed steel 11M5F with a chemical composition of 1.03-1.10% C, 5.2-5.7% Mo, 3.8-4.2% Cr, 1.3-1.7% V, 0.3-0.6% Si, and 0.3% Ce. The properties of 11M5F and R6M5 steels are examined and compared. The results of production and laboratory tests of the cutting properties of tools of the steels developed showed their high effectiveness, especially of 11M5F steel with 1% A1. The life of tools of the tungsten-free steels is two or three times greater than the life of tools of R6M5 steel.

Wear resistance of complexly alloyed iron-carbon alloys

High-carbon chromium alloys alloyed with Ti, Mo, Al, and Cu in the hardened state have much greater wear resistance than the high-chromium alloys used at present in industry as wear-resistant materials for operation in an abrasive medium. The difference between these alloys is particularly great in abrasion against silicon cloth. For instance, the wear resistance ɛs of the alloy U33Kh11T3M2YuD is 4.5 times greater than of steel R18 and of vanadium pig iron. This is obviously due to that fact that the investigated alloys contained titanium carbides, chromium carbides type M7C3, intermetallic phases with Mo, Ti, and Cr, and it is also due to the higher alloying of the γ- and α-phases and the larger carbon content in the α-phase.

Mechanical properties of die steels after low-temperature mechanical treatment

1. After LTMT, medium-carbon die steels 4Kh4VMFS, 4Kh5MF1S, and 6KhV2S obtain a better set of mechanical properties, compared with the properties of high-chromium steels Kh12F1, Kh12M, and Kh6VF, and fast-cutting steels R18, R12, and R6M5. 2. In order to provide the optimum set of mechanical properties after LTMT, the hardness of steels 4Kh4VMFS and 4Kh5MF1S should be HRC 58–60, and for steels Kh6VF and 6KhV2S it should be HRC 60-62.

Change in carbide heterogeneity during hot extrusion of cutting tools for high-speed steels

1. The larger the deformation and the higher the grade of the carbide heterogeneity of the original blank, the larger the change in the carbide heterogeneity during hot extrusion of tools made of high-speed steels. 2. Along the length and section of extruded tools the carbide heterogeneity changes in relation to the local deformation, which in turn depends on the total deformation, the shape of the tool, and other factors. 3. The largest changes in carbide heterogeneity are observed after hot extrusion of cast blanks and also blanks with a high original CH (larger than 5). 4. During hot extrusion of steel R18 in the range of deformations tested the size of the carbides remains basically unchanged, although large carbides (">15–20 μ) are broken up in sections with high local deformation.

Transformations during high-temperature marquenching of high-speed steel R6M5K5

To obtain the highest secondary hardness and red hardness the holding time during high-temperature marquenching should be 5–20 min at 600°, 5–15 min at 625°, or 10 min at 650° (625° for 10 min was established for steel R18 by A. P. Gulyaev and P. I. Podberezskii in 1939).

Hot deformation and recrystallization of high-speed steel R18

Hot deformation and recrystallization of high-speed steel R18