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The aim of the work was to determine the effect of Ti micro-addition on the hot tensile behaviour, microstructure and fractography of two low-C high-manganese steels with additions of Si and Al. The hot tensile tests were performed using the Gleeble 3800 thermomechanical simulator. Samples were stretched at a temperature range from 1050 ℃ to 1200 ℃ at a strain rate of 2.5·10 3 s−1. The microstructure of the tested high-manganese steels under conditions of hot deformation was influenced by strain hardening and simultaneous dynamic recrystallization, as well as precipitation processes-depending on the chemical composition of the alloy and plastic deformation parameters. The analysis of the curves registered in the hot tensile tests indicated that a decrease of strain hardening was the result of the dynamic recrystallization. Hot tensile curves of the Ti-micro-alloyed steel were characterized by higher yield stress compared to the Ti-free steel. The Ti micro-addition with a concentration of 0.075 wt.% guaranteeing stable TiN-type nitrides eliminated the possibility of precipitating AlN-type nitrides and complex MnS-AlN type non-metallic inclusions, which are harmful to hot ductility. Fracture modes of the Ti-free steel showed a mixed nature from 1050 ℃ to 1150 °C, i.e. ductile fracture and numerous cavities and voids were identified. As the deformation temperature increased to 1200 °C, the fracture character was brittle with numerous inter-crystalline cracks along austenite grain boundaries. The addition of Ti improved significantly the hot ductility behaviour characterized by higher values of flow stress and reduction in area as well as ductile fracture modes in the entire high deformation temperature range. [ABSTRACT FROM AUTHOR]

The excellent strain hardening behavior of high-manganese steel (HMnS) makes it widely used under strong impact and heavy wear conditions. However, the rapid hardening ability of HMnS needs to be improved under low stress. In this paper, laser remelting technology (LRT) was proposed to improve the hardening ability of HMnS under low stress. Firstly, the surface of HMnS was treated by LRT, and its surface and internal microstructure were characterized by a 3D profiler, an x-ray diffractometer, a scanning electron microscope (SEM) and an energy-dispersive spectrometer. Then, the microhardness and wear test were carried out by using a Vickers hardness tester and a wear tester, and the sub-surface microstructure and surface wear scars were tested by SEM and 3D profiler to study the wear performance of HMnS before and after laser remelting. Finally, the hardening effects and wear mechanism of laser-remelted high-manganese steel (LR-HMnS) were revealed. It was found that heterogeneities of LR-HMnS were composed of columnar structures, equiaxed structures and segregation region. These heterogeneities were conducive to improving the hardening ability of HMnS under low stress conditions, which could improve its wear resistance. [ABSTRACT FROM AUTHOR]

Effects of reduced (– 40 °C), ambient (20 °C), and elevated (200 °C) deformation temperatures on the microstructure evolution and strain hardening behavior of two low-C thermomechanically processed high-manganese steels were studied. The microstructure was characterized by means of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) techniques. The temperature-dependent tendency of austenite to strain-induced ε/α′-martensitic transformation and mechanical twinning was qualitatively and quantitatively assessed using the EBSD technique. The steel containing 26 wt% of Mn showed the beneficial strength–ductility balance at reduced deformation temperature -40 °C due to the intense Transformation-Induced Plasticity (TRIP) effect which resulted in the formation of significant ε- and α′-martensite fractions during tensile deformation. The mechanical properties of steel containing 27 wt% of Mn were more beneficial at elevated deformation temperature 200 °C due to the occurrence of intense Twinning-Induced Plasticity (TWIP) effect expressed by the presence of significant fraction of mechanical twins. Moreover, at the highest deformation temperature 200 °C, the evidence of thermally activated processes affecting the mechanical behavior of the higher Mn steel was identified and described. [ABSTRACT FROM AUTHOR]

The authors investigated tribological characteristics, phase composition of worn surfaces and microhardness of subsurface regions of WC–(Fe–Mn–C) composites with a two-phase (γ + α′) matrix containing 4 wt % Mn (WC–80G4), and a single-phase matrix of γ-iron containing 20 wt % Mn (WC–80G20) after sliding against a disk of high-speed steel at a contact pressure of 5 MPa and sliding speeds in the range from 10 to 37 m/s. The wear intensity of WC–80G4 and WC–80G20 increased with increasing sliding speed, while the wear rate of WC–80G20 at fixed sliding speeds was approximately three times higher than that of WC–80G4. The values of the friction coefficient decrease with increasing sliding speed in such a way that at fixed sliding speeds the values of the friction coefficient of WC–80G4 were lower than those of WC–80G20. The amount of mixed oxide FeWO4 formed during tribo-oxidation of the composites' worn surface increased with the sliding speed and was directly proportional to the wear intensity and inversely proportional to the friction coefficient values. At fixed sliding speeds tribooxidation of WC–80G4 leads to the formation of a larger amount of FeWO4 on the friction surface compared to the WC–80G20 composite. Indentation of worn surfaces with a Vickers pyramid showed that the nature of indentation resistance of tribolayers formed at high sliding speeds (30 m/s and 37 m/s) differs from that for tribolayers obtained at relatively low sliding speeds (10 and 20 m/s), namely, the friction surfaces after high sliding speeds were characterized by a more tough behavior. Measurement of microhardness values of the WC–80G4 and WC–80G20 composites obtained after indentation below tha worn surfaces recorded the fact of hardening of the near-surface regions of the WC–80G4 composites and, on the contrary, softening in the case of WC–80G20. Thus, under conditions of intensive heating and severe plastic deformation of the surface, structural-phase state of the substrate of WC–(Fe–Mn–C) composites, on which this viscous protective tribolayer is formed, turns out to be a very important factor. It is the two-phase (γ + α′) steel matrix that, under conditions of intensive frictional heating, provides the conditions for effective formation of a heterophase composite layer that reduces the friction coefficient and has a high resistance to fracture upon indentation. [ABSTRACT FROM AUTHOR]

Elastoplastic properties of tribological layers generated on WC–(Fe–Mn–C) composites with matrices composed of γ-iron containing 20 wt % Mn (WC–80G20) and of γ + α' with 4 wt % Mn (WC–80G4) after sliding against a high-speed steel disk at contact pressure of 5 MPa and sliding speeds in the range from 10 to 37 m/s have been investigated. It was established that the main factor determining the morphology of the worn surface is the sliding speed. At sliding speeds of 10 and 20 m/s, fine-grained mechanically mixed tribolayers of 3–4 µm in thickness formed. As the sliding speed increased to 30–37 m/s, the thickness of the tribolayers reached 10–15 µm, and the structure consisted of oxidized fragments of WC–(Fe–Mn–C) composites and FeWO4 complex oxide without any sharp boundary observed. Both highest values of nanohardness (~33 GPa) and effective Young's modulus (~523 GPa) were achieved on the WC–80G4 tribolayer after friction at 10 m/s when the nanoindentor indented agglomerates of fragmented WC grains. This contrasted with the properties of the tribolayers formed at sliding velocities above 20 m/s. The results of nanoindentation showed an obvious effect of tribochemically induced softening in the generated tribolayer after high-speed sliding at 37 m/s. Such a layer had a composite microstructure consisting of fragmented composite components cemented in-situ by tribochemically formed FeWO4 and, in addition to antifriction properties, had an increased indentation fracture resistance. [ABSTRACT FROM AUTHOR]

Evolution of the microstructure of steel 110G13L under friction is studied using the method of synchrotron x-ray diffraction and subsequent profile analysis of the diffraction peaks. Friction of the high-manganese steel is accompanied by accumulation of crystal lattice defects, which finds reflection in changes in the full widths of half maximums. The experimentally determined structural defects are a result of growth of microdistortions of the austenite lattice and reduction of the sizes of coherent scattering domains. It is shown that the friction interaction produces anisotropic displacement of the diffraction maximums of the austenite, which indicates enhanced probability of formation of stacking faults and lowering of the stacking fault energy. Obvious features of mechanically induced phase transformations have not been detected. [ABSTRACT FROM AUTHOR]

Ladle treatment technology is expected to be a new approach for prevailing over the hot crack susceptibility of conventional high-manganese steel. The liquefaction and solidification mechanisms of the conventional and ladle-treated high-manganese steel were detected by DTA. Their solidification structures were observed by optical microscope and scanning electron microscope. Multistage deformation process of the two steels was carried out by using thermomechanical simulator (Bahr TTS-820) from 700 to 1200 °C. In addition, their thermoplastic character was detected by dilatometer (DIL-805/D) from 800 to 1200 °C. On the other hand, TEM was used for explaining the nucleation of cementite and austenite at magnesium sulfide nuclei in ladle-treated high-manganese steel. The results refer to the peculiar microstructure after ladle treatment of high-manganese steel causes a great enhancement in the hot forming character of high-manganese steel in terms of crack susceptibility and flow stress. In addition, the good formability of the ladle-treated high-manganese steel was confirmed by comparing with the low-carbon steel at hot working temperatures. [ABSTRACT FROM AUTHOR]

Modification of high-manganese steel castings in the mold by titanium carbonitride is investigated. First, the basic principles of alloying and modification of cast alloys are outlined, and the relevant literature is reviewed. That provides the basis for formulating the research goals. The practical significance of the research for casting enterprises is confirmed. Next, the materials employed are considered in detail: the batch components, the modifier, the materials used in the casting molds. Likewise, the experimental methods are described: in particular, the methods used in producing experimental castings and in determining the thermal conditions in the mold and the optimal heat treatment. In addition, the metallographic techniques employed are noted. The experimental results regarding the modification of the steel casting by fine titanium-carbonitride powder in the mold are presented. The influence of such modification on the performance of the high-manganese steel is considered, in terms of improved abrasive and impact–abrasive wear resistance. Metallographic data explain the basis for the improved performance of the high-manganese steel. The influence of the thermal conditions in the mold is considered: in particular, the influence of the rate of alloy cooling in the mold on the performance of the modified high-manganese steel. Finally, on the basis of the research findings, recommendations are made for improving the performance of cast high-manganese steel products. In addition, recommendations are made regarding the optimal consumption of titanium-carbonitride powder so as to obtain the required microstructure and properties of the high-manganese steel. [ABSTRACT FROM AUTHOR]

The work hardening of a series of high-manganese steels with various chemical compositions (manganese contents of 18-30 wt.% and carbon contents of 0.06-1.2 wt.%) and deformation products (mechanical twins and/or ε-martensite) was modeled using a physics-based model. The model comprised the contributions of dislocation glide and phase transition (mechanical twinning and/or ε-martensite formation) kinetics to the overall work hardening rate. The model parameters included the physical characteristics of the steels such as the stacking fault energy as well as the microstructural features such as the volume fraction of the deformation products. A key point of the model was that it is globally applicable for all high-manganese steels—including twinning-induced plasticity and/or transformation-induced plasticity steels—instead of being limited to a specific category of these steels. A good agreement was found between the predicted and observed work hardening for all the experimental alloys in this study as well as several high-manganese steels in the literature. [ABSTRACT FROM AUTHOR]

The thermoplastic characteristics of high-manganese steels with different phosphorus and sulfur contents were investigated. The zero-ductility temperature and plasticity-temperature range of the high-manganese steels were reduced significantly with increase in phosphorus or sulfur content. The relationship between the initial forging temperature of the high-manganese steel and the content of phosphorus and sulfur can be expressed as Tift = 1200 - 1530wS - 1650wP. The final forging temperature is 900°C, and the heating rate during the forging of the high-manganese steel crossing must be slow. The lifetime of the forged high-manganese steel crossing was almost doubled compared with conventional cast high-manganese steel crossing. [ABSTRACT FROM AUTHOR]

The basic factors that affect the wear resistance of high-manganese steel are considered. The literature on this topic is reviewed. Conclusions are formulated regarding the materials used in existing studies. Research topics of interest to enterprises that manufacture and employ Hadfield steel are identified. Materials used in the machining of liquid steel are considered. Production technology for experimental high-manganese steel parts is discussed. The composition of the alloy employed as the base is analyzed. The procedure and equipment used to determine the cooling rate of alloys in the mold and to study the wear resistance in conditions of abrasive and impact-abrasive wear are outlined, as well as methods of thermal analysis. Results are presented for the alloying of Hadfield steel by nitrided ferroalloys and other alloys. The coefficients of abrasive and impact-abrasive wear resistance are plotted for different alloying conditions. In addition, the influence of the alloying elements on the wear resistance of high-manganese steel in different wear conditions is studied. The concentrations of the alloying elements corresponding to maximum abrasive and impact-abrasive wear resistance are established. In addition, the results of thermal analysis are presented. The heating of Hadfield steel castings prior to quenching is considered. The temperature ranges corresponding to processes such as excess-phase deposition, the solution of cementite in austenite, and complete solution of phosphide eutectic and metal carbides are established. The temperature limits of oxidation and decarburization of the steel are also determined. On the basis of the results, recommendations are made with a view to increasing the wear resistance of castings made from high-manganese steel for different operating conditions and also to selecting the heat-treatment temperature for such castings. [ABSTRACT FROM AUTHOR]

Shear deformation along the longitudinal cross section of the high-manganese steel strip has been analyzed in hot asymmetrical rolling process using rigid-plastic finite element model. The friction coefficient between the rolls and the strip surfaces, the diameter of the work rolls, the speed ratio for the lower/upper rolls, the reduction rate and the initial temperature of the billet were all taken into account. Influence of these process parameters on the shear stress, the shear strain and the related shear strain energy in the center layer of the hot-rolled strip was analyzed. It is indicated that increasing the speed ratio, the reduction rate and the work roll diameter is an effective way to accumulate more shear strain energy in the strip center. A mathematical model reflecting the relationship between the shear strain energy and the process parameters has been established. [ABSTRACT FROM AUTHOR]

The formation of the excess phase in high-manganese steel is considered over a wide range of cooling rates. This phase, which consists of a phosphide eutectic and secondary carbides, may be deposited both along the grain boundaries and within the grains. At low cooling rates, the phosphide eutectic is mainly formed, with a small quantity of secondary carbides. In addition, excess phase with mixed morphology is encountered. It consists of the eutectic and secondary carbide, with a coherent boundary between them. With increase in the cooling rate, the excess phase consists primarily of secondary carbides; its size is reduced. The influence of the cooling rate on the chemical composition of the excess phase is also of interest. Increase in cooling rate is found to reduce the manganese content in the secondary carbides deposited. The ratio between iron and manganese in the phosphide eutectic does not depend on the cooling rate and is practically constant. [ABSTRACT FROM AUTHOR]

The article discusses the peculiarities of the formation of the plate structure made from high-manganese steel and ways to increase its service life under the conditions of shock-abrasive wear on crushing stations of the ferroalloy industry. The failure of existing technological processes for manufacturing crushing stations was revealed and new process, characterized by resource-saving factors, was proposed. Based on the method of the planned experiment, the regression equations of the technological process were made and their parameters were optimized. The duplication of the technological process efficiency upon a 20% increase in the product wear resistance was achieved as a result of experimental investigations. [ABSTRACT FROM AUTHOR]