Carbon Content Of Steel Research Articles

Influence of Process Liquids on the Formation of Strengthened Nanocrystalline Structures in Surface Layers of Steel Parts during Thermo-Deformation Treatment

The results of the influence of a range of process liquids on the formation of strengthened nanocrystalline structures in the surface layers of steel samples with different carbon content during thermo-deformation treatment are presented. The liquids were mineral oil; mineral oil with active additives containing polymers; water; and an aqueous solution of mineral salts based on magnesium and calcium chlorides. The thickness and hardness of the nanocrystalline layer increased with increasing steel carbon content. The thickness and microhardness of Steel C45 are 230–240 μm and 8.6 GPa, respectively, when using mineral oil with AAP, 110–120 μm and 7.2 GPa, respectively, when using mineral oil alone, and for steel CT80 when using mineral oil, they are 180–200 μm and 9.1 GPa, respectively (C45 and CT80 refers to engineering steels). The process liquid is decomposed into its component chemical elements by the high temperatures and pressures in the contact zone of the tool with the treated surface. It also gives off active hydrogen, which diffuses into the surface layer of the metal and significantly affects its formation. It was established that the greatest thickness and hardness of the layers were obtained after processing pre-hydrogenated samples. The choice of process fluid is critical during thermo-deformation treatment.

Experimental Study on the Ignition Behavior of Wildland Fuels Ignited by Heated Stainless-Steel Particles

ABSTRACT Hot metal particles from activities like machining, grinding, and welding are significant ignition sources for wildland fuels. Thus, this study examines the effects of stainless-steel particle geometries and wildland fuel beds on wildfire ignition behavior. To this purpose, experiments have been conducted to investigate the impact of particle type, composition, diameter, number, and wildland fuel bed species on ignition behavior. Three common California wildland grass fuel species were studied: Bromus (Bromus diandrus), Tall Wheatgrass (Thinopyrum ponticum), and Avena Wildoats (Avena fatua). Various stainless-steel grades were tested as ignition particles. The findings from this study support prior research and indicate that increasing the quantity and diameter of ignition particles reduces ignition temperature and affects the type of ignition (flaming, smoldering, or none). Moreover, results from this study showed that decreasing the carbon content in stainless steel may lower the temperature required to reach wildland fuel ignition. In addition, wildland fuel species influenced ignition type and temperature. For instance, Bromus fuels had the lowest flaming ignition temperature at 320°C whereas Tall Wheatgrass and Avena ignited at 400°C and 380°C, respectively. Flaming ignition was primarily observed in Bromus fuels, while Avena and Tall Wheatgrass primarily supported smoldering ignition. This work asserts that species-specific fuel morphology, chemical, and thermal properties affect the flammability of grassy fuels when these are ignited by metal particles and observes that in addition to particle geometry, the chemical properties of ignition particles, such as carbon content, may also lay a key role in shapping ignition behavior.

Development of a non-destructive depth-selective quantification method for sub-percent carbon contents in steel using negative muon lifetime analysis

The amount of C in steel, which is critical in determining its properties, is strongly influenced by steel production technology. We propose a novel method of quantifying the bulk C content in steel non-destructively using muons. This revolutionary method may be used not only in the quality control of steel in production, but also in analyzing precious steel archaeological artifacts. A negatively charged muon forms an atomic system owing to its negative charge, and is finally absorbed into the nucleus or decays to an electron. The lifetimes of muons differ significantly, depending on whether they are trapped by Fe or C atoms, and identifying the elemental content at the muon stoppage position is possible via muon lifetime measurements. The relationship between the muon capture probabilities of C/Fe and the elemental content of C exhibits a good linearity, and the C content in the steel may be quantitatively determined via muon lifetime measurements. Furthermore, by controlling the incident energies of the muons, they may be stopped in each layer of a stacked sample consisting of three types of steel plates with thicknesses of 0.5 mm, and we successfully determined the C contents in the range 0.20–1.03 wt% depth-selectively, without sample destruction.

The Fe-C diagram – History of its evolution

The evolution of concepts and methods of physical and chemical science that contributed to the formation of the Fe-C diagram during the previous centuries is considered. Despite the classical knowledge, there are still differences in the representation of the Fe-C diagram by scientists from different countries, in particular, the data of scientists from Germany, Poland, Ukraine, the USA, and Australia are somewhat mismatched. The authors tried to understand the reasons for this discrepancy. To conduct the research, general scientific methods of cognition were used: comparative analysis and synthesis, as well as a chronological one. It is claimed that the first studies of carbon content in steel were carried out in 1802. Further research development began in 1827–1829 when it was established that graphite is pure carbon. It is emphasized that further studies of carbon content in steel and cast iron are connected with attempts to create the first graphs of dependence on content and temperature. This, in turn, contributed to the development of the industrial revolution. It is believed that the first complete diagram was presented in 1897 by Roberts-Austen. Later, with the use of X-ray methods and microscopy, the Fe-C diagram gradually took on a new form. At the beginning of the 20th century, scientists actively proposed their phase diagrams. Studies conducted by scientists of different countries during 1909–1911 gained a consolidation, which was produced at the 6th Congress of the International Association for testing materials meeting into the unification of the names of phase transformations. Further research until the beginning of the Second World War was aimed at the creation of “pure” steel, that is, without harmful impurities, and clarifying the transformation temperatures. The period of the Great Depression in the USA and the war in Europe did not contribute to scientific research. At the same time, for the mass production of steel and cast iron, errors in critical points of a few degrees did not have a significant impact, that is, refining the temperatures of phase transformations were not considered appropriate. Today’s trend in scientific research is aimed at solving environmental problems caused by the industrial revolution.

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PREFACE

Quantitative hardness‐carbon content‐microstructure correlation in normalized plain carbon steel

AbstractComposition (carbon content) dependent critical structural evolution in correlation to hardness attained is judiciously investigated for plain carbon steel, the most widely used cost‐effective structural material, under normalizing treatment of industrial relevance involving non‐equilibrium still air cooling. The solid state phase transformation under non‐equilibrium still air cooling is conceived in terms of a logarithmic variation of eutectoid carbon content with the gross carbon content of steel in view of maintaining fixed maximum solubility of carbon in α‐iron with an assumption of the prevailing para‐equilibrium condition. Such a unique formulation for non‐equilibrium condition together with consideration of Hall–Petch type relationship and rule of mixture for two prime microconstituents (proeutectoid α‐ferrite and pearlite) finally results in a new mathematical relationship for chemical composition‐structure‐property correlation for the non‐equilibrium normalizing treatment readily practiced in industry. Indeed, a composition dependent structural refinement effect is established that is exemplified with the rise in hardness level in plain carbon steel under conventional normalizing treatment. Most importantly, the experimentally measured overall hardness values closely follow those obtained by the developed mathematical relationship, thereby meeting an ever‐needed requirement of direct determination of steel hardness of practical relevance from microstructural parameters.

Metallographic Evaluation of Increased Susceptibility to Intermediate Embrittlement of Engine Valve Forgings Made of NCF 3015 High Nickel and Chromium Steel.

This paper focused on determining the increased tendency of cracking after the die forging process of high nickel and chromium steel. The increase in carbon content in austenitic nickel-chromium steel promoted the tendency of valve forgings to forging intergranular crack on the valve head. Attention was paid to issues related to the chemical composition of the material to be considered when hot forming nickel-chromium steel components. Optical and scanning electron microscopies were used to examine the microstructure and fracture features of the samples removed from a fractured valve head. The embrittlement was due to microcavity formation at grain boundaries. Creep theory at grain boundaries was used to explain crack formation. The tensile behavior was interpreted from the evolution of the microstructure during deformation and referred to intermediate brittleness to explain the effect of carbon. It was found that the increased carbon content of the nickel-chromium steel and the strong undercooling observed at the edges of the valve head are factors that promote a reduction in grain boundary cohesion and enhance intermediate temperature embrittlement. Finally, it was found that the formation of a heterogeneous structure manifested by the presence of grain boundary M23C6-type carbides in the austenitic matrix was most likely related to the occurring brittleness.

Evolution of morphology, microstructure and hardness of bodies and debris during sliding wear of carbon steels in a closed tribosystem

Debris generated during sliding wear of steels have an important role on tribosystem's behavior. However, the evolution of morphology, microstructure and hardness of debris and solid bodies, and their role on friction and wear is not quite evident, especially for closed tribosystems. Interrupted pin-on-disk wear tests were carried out on low, medium, and high carbon steel tribopairs, while an adaptation of the test apparatus effectively prevented debris ejection from wear track, simulating a closed tribosystem. The experiment was designed according to a repeated measures ANOVA model for multiple dependent variables that includes running-in duration, wear rates, surface hardness and their ratios, and debris size and shape. Plasticity-dominated severe wear took place in all cases, generating two types of metallic debris: flake-type via adhesion and delamination processes and, after sufficient sliding distance, cutting-type due severe shear deformation caused by the abrasive action of hard asperities. Debris were, at least, 20% softer than worn pins and disks, and provided some lubricating effect when adhered, sheared and rolled between sliding surfaces. Low carbon steel wear generated more soft and adherent debris, resulting in prolonged running-in periods. Finally, steel carbon content did not affect wear mechanisms, debris morphology (size and shape), worn surface hardness and wear rates in closed tribosytems, when a debris-flow controlled process prevails.

Анализ причин образования дефектов заготовок из стали 12x18h10t и разработка рекомендаций по их устранению

Introdution. Austenitic steel (e.g., AISI 304, AISI 321, AISI 316, AISI 403, 12-Cr18-Ni10-Ti, etc.) is widespread, which is caused by high corrosion resistance and the corresponding possibility of use in aggressive media. The following most common types of 12-Cr18-Ni10-Ti steel defects can be distinguished: integranular corrosion, martensitic orientation of the α-phase and ferrite δ-phase. The purpose of work: to analyze the defects formation reasons of the 12-Cr18-Ni10-Ti steel grade billets and to develop recommendations for their elimination. The methods of investigation. Tests of 12-Cr18-Ni10-Ti steel samples for resistance to integranular corrosion, metallographic analysis of defects were carried out in this work. Hardness measurements were carried out for various degrees of billets reduction. Thermodynamic calculations of phase equilibrium in multicomponent steel for different temperatures were performed by the Thermo-Calc software. Results and Discussion. It is determined that in order to prevent integranular corrosion, it is necessary to reduce the nitrogen and carbon content in steel at the stage of ladle refining to 0.05%, and also to ensure the concentration of titanium in steel is not less than the permissible value — 0.3%. These measures contribute to the reduction of Cr23C6 chromium carbides responsible for integranular corrosion. It is necessary to reduce the degree of compression of the billets to a level of no more than 50% to prevent the appearance of a ferromagnetic martensitic α-phase, since the formation of this defect is associated with a high degree of compression during drawing. The high-temperature phase of δ-ferrite exists in the metal structure in a wide temperature range. Reducing this range to 100 degrees or less by optimizing the composition of the carbon and chromium alloy in accordance with GOST 5632-2014 leads to a significant reduction of the amount of ferrite. However, it is not possible to completely eliminate it from the structure of steel. For all cases, it is necessary to assign austenization of billets in the temperature range of 1,050…1,100 °C.

Novel method on homogenized La treatment of GCr15 steel by the self-reaction of La2O3 containing slag and steel for vacuum electroslag remelting

The interaction between slag and GCr15 steel under argon and vacuum were investigated by laboratory experiments. The results show that the maximum and average size of inclusions, and the proportion of large inclusions decrease after slag-steel interaction. Compared with the test under argon, inclusion size of the steel in the test under vacuum is smaller and more uniform, which is attributed to that vacuum promotes the reaction of C and O in molten steel to form CO. The La content increase from 0 to 0.0022 wt% in the steel processed by La2O3 containing slag after for 5 min holding at 1873 K under 0.5 kPa. Thermodynamic calculation reveals that the La2O3 in molten slag can be reduced by dissolved C in liquid steel to form dissolved La under vacuum due to the relatively higher carbon content of GCr15 steel and appropriate vacuum condition. The microstructure and primary carbides of the tested steel under vacuum are finer than that under argon. The present study provides a theoretical basis for the homogenized La treatment of GCr15 steel under vacuum, which shows a promising prospect in vacuum electroslag remelting of high-end bearing steel.

On ascertaining hardness‐microstructure relationship in annealed steel for varying carbon content

AbstractPlain carbon steels of five different carbon contents up to eutectoid composition have been provided with the conventional full annealing treatment. Qualitative and quantitative studies of the microstructure are carried out using optical microscopy and field emission scanning electron microscopy techniques. Even under similar cooling rate pertaining to the full annealing treatment (furnace cooling); microstructural modifications of individual microconstituents are feasible with varying chemistry (carbon content) of plain carbon steel. The refinement of microstructure for both proeutectoid α‐ferrite and pearlite is found to be accentuated with increasing carbon content of annealed steels till eutectoid composition. Hall‐Petch type relationship explains adequately the relationship between hardness and the size of the microconstituent both in terms of the grain size of proeutectoid α‐ferrite and the interlamellar spacing of pearlite. Henceforth an empirical relationship is developed for the first time taking into account the rule of mixture to correlate overall hardness, carbon content, grain size of proeutectoid α‐ferrite and interlamellar spacing of pearlite. The empirical relationship originated thereby is found to closely match the experimental results.

Multifunctional Induction Coil Sensor for Evaluation of Carbon Content in Carbon Steel

Carbon steel has proven to be an important structural and functional material that plays an irreplaceable role in the worldwide economy. The influence of carbon on the mechanical and magnetic properties of the steel is well understood. Thus, the precise knowledge of the amount of carbon content in steel is crucial. Magnetic Barkhausen noise (MBN), magnetic hysteresis loop (MHL), and impedance measurements are reliable tools to assess carbon content. In this work, a multifunctional induction coil sensor used for MBN, MHL, and impedance measurements is designed and optimized. A multifunctional measurement system using the optimized induction coil is employed to measure MBN, MHL, and impedance signals. The parabolic dependence of the maximum value of MBN envelope on carbon content in steel is theoretically analyzed and experimentally verified. Coercive field and remanence from MHL measurements as well as the maximum impedance value are found to be proportional to carbon content and their dependence is explained with analytical simulations.

Comparative Analysis of Wheelsets Tyres, Hardened Using a Laser or Plasma Heat Source

Lateral wear of the locomotive wheel flange is one of the main types of wear that occurs during rolling stock operation. An important characteristic of a rail wheel rim is its wear resistance, which directly depends on the carbon content in steel. The carbon content in wheel steel of group 2 in the amount of 0,55–0,65 is due to the fact that at its lower concentration, the proportion of grain boundary ferrite increases, which leads to a decrease in the contact strength of wheels, and a higher one leads to a tendency to brittle fracture.The increased carbon content makes it possible to harden the surface of steel. Plasma and laser hardening technologies can be used to reduce tyre flange wear and increase the service life of locomotive wheelsets.The objective of this work is to determine advantages and disadvantages of technologies for laser and plasma hardening of working surfaces of tyres of wheelsets of railway rolling stock.The comparative analysis related to microstructure and microhardness of wheelsets tyres of the 2TE25KM diesel locomotive which are made of wheel steel of group 2 according to GOST 398-2010 state standard and hardened respectively by plasma and laser hardening.The tasks set were solved using theoretical and experimental research methods. The preparation and study of hardened samples was carried out using the equipment of the testing laboratory of LLC Scientific and Technical Association «IRE-Polus».A study referred to hardened zones in various areas and sections of the tyre. Tribological tests concerned wear resistance of specimens hardened with a high-power fiber laser. The main advantages and disadvantages of laser and plasma hardening processes are revealed.The conducted studies allow making a conclusion that the use of laser hardening technology for hardening wheelsets tyres, as an alternative to the plasma hardening process, is highly promising.

Introduction of a constitutive material model considering variable carbon content for cutting simulation

Carbon steels show complex strain hardening and dynamic strain aging effects under high plastic strains, high strain rates, high temperatures and high heating rates, and thus a sufficiently complex constitutive model is needed to capture this behavior. Carbon content in such steels (e.g., AISI 1018, 1045, 1075) influences strength and hardening as well. A recently-developed material model for 1045 steels was therefore modified to capture the effect of carbon content on the material response. The model can also capture time-dependent plastic response associated with interrupted austenite transformation under short (sub-second) heating times, for the simulation of machining operations.

Mechanism and control of uneven cooling on the surface crack defects in multi-mode continuous casting-rolling line

When the thin slab caster produces low-carbon steel, the uneven cooling alarm can easily occur at both sides of the nozzle in the thermal image, and there are cracks at the corresponding positions where the uneven cooling occurs. The causes of uneven cooling are studied, and the mechanism of uneven cooling causing surface cracks is proposed. The results show that the generation of uneven cooling is greatly related to the carbon content of molten steel, the thickness of the copper plate, and the hydrogen content. The surface roughness method shows that the uneven cooling index increases with the increase of carbon content. The uneven cooling index gradually increases with the decrease of the copper plate thickness. When the copper plate thickness is less than 41 mm, the uneven cooling index of the mold increases from the 1.1 to about 14.7. With the increase of H content, the uneven cooling index increases. When H exceeds 7 ppm, the uneven cooling index can reach 14.5. By adopting reasonable and effective control measures, the uneven cooling index of the mold is significantly reduced from 3.85 to 0.73, and the surface crack defects in multi-mode continuous casting-rolling line are effectively alleviated.

STUDIES OF THE INFLUENCE OF TECHNOLOGICAL PARAMETERS OF THE PRODUCTION OF GRINDING BALLS FROM THE REJECTION OF RAIL STEEL ON THEIR IMPACT RESISTANCE

Based on the conducted research, a list of technological parameters of steelmaking and rolling processing that have a significant impact on the impact resistance of grinding balls from the rejection of K76F grade rail steel in the conditions of JSC "Guryev Metallurgical Plant" has been determined. Using standard methods of statistical and metallographic analyses, the degree and nature of the influence of these parameters on the rejection of grinding balls based on the results of copra tests has been established. It is determined that an increase in the content of carbon, hydrogen and sulfur in steel leads to an increase in the rejection of grinding balls according to the results of impact resistance tests. At the same time, the influenceof carbon is associated with the formation of cementite–type carbides when the carbon content increases to over-eutectoid values, the influence of hydrogen is associated with the formation of floccenes, and the influence of sulfur is associated with the formation of non-plastic sulfides. According to the rolling conversion, a significant effect of an increase in the temperature of rolling balls on an increase in their impact resistance was established, due to an increase in the plasticity of K76F steel in the actual rolling temperature range (an increase in the probability of defects brewing during deformation). It is determined that the total relative degree of influence of the parameters of steelmaking and rolling processing on the rejection of balls during impact resistance tests is 71%, the remaining 29% relate to the influence of the parameters of the heat treatment of balls, which is confirmed by the results of metallographic studies (quenching cracks were detected in the fracture of the balls).

Real-Time Prediction Model of Carbon Content in RH Process

In the Ruhrstahl–Heraeus (RH) vacuum degassing process, we propose a real-time prediction model for the carbon content in molten steel, and show that the decarburization endpoint can be accurately determined using this model. Firstly, we applied a novel off-gas analyzer that can measure the carbon oxide concentration produced in the decarburization reaction faster and more accurately. Next, we generate decarburization curves using the off-gas components measured by the new analyzer. The decarburization curve describes the carbon content profile well during operation, and shows good agreement with the actual carbon content. In order to predict the carbon content during operation in real time, we create an artificial neural network (ANN) using the decarburization curves and operation data. By comparing the endpoint carbon content measured at the end of the operation with the predicted values, we confirmed the excellent predictive performance of the ANN model. Finally, we show that it is possible to accurately determine the decarburization endpoint using the prediction model. We expect that the proposed real-time prediction model can increase the productivity of the RH process.

ДОСЛІДЖЕНЯ ПРОЦЕСІВ НАВОДНЮВАННЯ ВУГЛЕЦЕВИХ СТАЛЕЙ РІЗНОЇ СТРУКТУРИ У СІРКОВОДНЕВИХ СЕРЕДОВИЩАХ

The effect of applied static loads, structure, and carbon content in steels on their hydrogenation was investigated in the paper. The content of absorbed hydrogen was determined by the method of vacuum extraction at temperatures of 200, 400, 600 and 800 °С for 720 hours, after corrosion in the NACE solution. It was shown that the hydrogenation of 0.8% C steel in the number of structures: pearlite, sorbite, troostite and martensite increased. The ferrite-pearlite structure of 0.45% C steel was the most intensively hydrogenation (19.4 ppm), sorbitic, troostitic and martensitic - less by 30...50%. The main contribution to the absorbed hydrogen was made by diffusive-mobile hydrogen. Its share in the total amount of absorbed reached~65...74% for pearlitic, 50...54% sorbitic, 64...78% troostitic and ~67% martensitic U8 steel structure. For steel 45, it is ~61...72% for ferrite-pearlitic, ~74...79% sorbitic, ~61...75% troostitic, and ~52...85% martensitic. The absorbed hydrogen content of 0.8 % C steel with sorbitic, trostitic, and martensitic structures at temperatures of 400, 600, and 800 ºС increased, while that of steel 45, on the contrary, decreased. This indicated the greater strength of the hydrogen-metal bond in 0.8 % C steel. Therefore, the structure of steels affects the sorption of hydrogen more than the carbon content. Applied static loads  = 300 MPa increased the content of hydrogen absorbed by steels by ~9...15%. On 0.8% C steel, this manifests itself more significantly - СН/С0Н= 1.3...1.8. As the imbalance of the structure increased, the resistance of steels to corrosion cracking under static loads decreased. This was determined by the dispersity of the structure and the morphology of sulfide films, which are formed during the corrosion of steels in the NACE solution. Therefore, static loads most contributed to the hydrogenation of 0.8 % C steel with a troostite structure, and 0.45% C - troostite and martensitе.

Time-resolved in-situ dislocation density evolution during martensitic transformation by high-energy-XRD experiments: A study of C content and cooling rate effects

Recent studies on the mechanical behavior of martensitic steels show the importance of considering lath martensite as a “polycrystalline aggregate” with a large distribution of the local yield strength. The latter depends on local microstructural features, such as lath sizes, carbon distribution (in solid solution, segregated to defects, in carbides) and density of defects Internal stresses have to be considered as an additional contribution to the yield strength participating to enlarge the distribution of the local flow stresses at the microstructure scale.This study focuses on one of these microstructural features, the dislocation density. Its evolution is followed in situ upon martensitic transformation by High Energy X-Ray Diffraction experiments on a synchrotron beamline. A previously introduced method, based on modified Williamson-Hall (mWH) analysis, is improved in order to take account of the martensite lattice tetragonality when applying the mWH method.The influence of the steel carbon content (0.11, 0.21 and 0.31 wt.% C steels) and of the cooling rate (-10, -50, -100 °C/s and water-quench) on the dislocation density evolution in martensite during the martensitic transformation is established. The effect of the cooling rate on the dislocation density is low between -10 and -100 °C/s, but becomes visible after the water-quench. The higher the C content, the higher the dislocation densities at the end of the transformation. The steels with higher C content also show a wider distribution of the local dislocation density and, therefore, of the local yield strength.

Influence of carbon content on the microstructure and cryogenic tensile properties of N50 austenitic stainless steel after aging treatment

Nitrogen strengthened stainless steel named N50 fully meets the strength demand of developing novel alloys for more powerful fusion reactor applications in superconducting coil armor materials. The detailed evolution of microstructure and its resultant effect on tensile properties of N50 steel with two different C contents after aging at 650 °C were investigated. The results indicated that the cryogenic ductility of 0.04 wt % C steel decreased significantly with the extension of aging time, while the ductility of 0.01 wt % C steel remained stable. Bulk primary MX precipitates and Z phases are distributed in the matrix after solution annealing. After aging treatment, the flake M23C6 mostly occupies the grain boundaries of 0.04 wt % C steel, while the smaller cubical Z phases were the main intergranular precipitates in the 0.01 wt % C steel. The higher carbon content increases the nucleation driving force of M23C6 and contributes to its more precipitations after aging. The larger intergranular M23C6 in 0.04 wt % C steel leads to its brittle fracture features. While the stable intergranular Z phases in 0.01 wt % C steel obtained relatively excellent low-temperature plasticity. Serving as a superconducting coil armor material, the carbon content of N50 steel should be limited to acquire better cryogenic mechanical properties by eliminating the precipitation of intergranular M23C6.