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The effect of Cr content on the microstructure and mechanical properties of CSS‐42L steel is investigated by X‐ray diffractometer, scanning electron microscopy, and transmission electron microscopy. The results show that increasing Cr from 8% to 13.5% significantly improves toughness and ductility while moderately decreasing the strength. The tensile strength, fracture toughness (KIC), and impact absorbing energy of 13.5% Cr steel are 1.8 GPa, 88.6 MPa√m, and 58.5 J, respectively. 13.5%Cr steel possesses larger grain size and fewer undissolved M6C carbides than 8%Cr and10%Cr steels, which is attributed to that Cr addition increases Cr content in the (Mo,Cr)6C, reducing the dissolution temperature and ability to inhibit grain growth. Cr significantly decreases the Martensite start (Ms) temperature from 263 to 53.1 °C and increases the retained austenite from 0.3 to 13.19 vol%. Cr increases the number density and diameter of nanoscale M2C, which is attributed to Cr promoting the dissolution of Mo and increasing the nucleation rate. Meanwhile, the higher Cr content also increases the growth rate of the carbides along the diameter direction. Cr addition reduces the contribution from coherency strengthening caused by decreased lattice misfit and increased the contribution of Orowan dislocation looping resulted from higher volume fraction and size of M2C. [ABSTRACT FROM AUTHOR]

Metallurgical quality of bearing steel is an important foundation and guarantees for determining the performance, accuracy, service life, and reliability of bearings. Nowadays, advances in refining technology have led to a significant increase in the cleanliness of bearing steel, and the control of large‐size carbides (primary, banded, and network carbides) has become particularly important. In this article, the recent research on large‐size carbides regarding morphology, precipitation mechanism, and control methods is reviewed. Firstly, the morphological characteristics of carbides are summarized. Primary carbides appear as blocky, lamellar, or irregular shapes, while banded carbides are distributed in bands. Network carbides mainly precipitate along the austenitic grain boundaries and aggregate to form networks. Secondly, the precipitation mechanisms of carbides are summarized. Dendritic segregation is the fundamental cause of the formation of primary and banded carbides, whereas network carbides are the supersaturation precipitation of carbon at austenite grain boundaries. Finally, methods for controlling large‐size carbides are summarized, including improving dendritic segregation, high‐temperature diffusion annealing, improving rolling and cooling processes and using magnesium or rare‐earth treatments. No single method offers sufficient carbide control, and mechanism of rare‐earth refining carbides is unknown. Thus, a comprehensive approach should be used in production to effectively regulate carbides in steel. [ABSTRACT FROM AUTHOR]

The alloying elements in 8Cr4Mo4V bearing steel tend to form large primary carbides with carbon, which not only causes element segregation but also becomes the primary source of fatigue crack initiation, thereby decreasing the material's usability and machinability. Owing to the excellent thermal stability of primary carbides, traditional homogenization annealing requires high temperatures, which is both time‐ and energy‐intensive. Excessively high heat treatment temperatures can also result in “overburning” of the sample. Herein, primary carbides are rapidly dissolved at low temperatures using pulsed electric current treatment. The additional free energy introduced by the pulsed electric current lowers the thermodynamic barrier for carbide dissolution. During the second‐phase dissolution process, the unbalanced diffusion of elements may cause the formation of Kirkendall voids. Due to the difference in electrical conductivity between the voids and the matrix, the pulsed electric current generates thermal compressive stress on the voids, promoting rapid atom migration to these voids and accelerating their healing. This pulse‐current treatment technology offers a novel method for the rapid dissolution of carbides in alloys at low temperatures and for the rapid healing of related voids. [ABSTRACT FROM AUTHOR]

Electroslag remelting (ESR) is essential for producing high‐end special steel, but its complex process and numerous influencing factors make quality control challenging. This study addresses oxygen content control during ESR using a big data machine learning approach. An incremental learning strategy is proposed based on an optimized Wasserstein generative adversarial network with gradient penalty (WGAN‐GP) for data enhancement, focusing on G20Cr2Ni4A bearing steel. The WGAN‐GP model enhances time‐series data and metadata, utilizing long short‐term memory networks, fully connected networks, and attention mechanisms. The effectiveness of data enhancement is verified using a deep neural network classifier and statistical methods. Data is divided into historical and data streams, with an incremental learning strategy based on histogram gradient boosting regression trees to prevent catastrophic forgetting and improve efficiency through knowledge distillation and real‐time hyperparameter adjustment. Results show that the data augmentation method significantly improves model generalization and accuracy in small sample metallurgy. The incremental learning strategy enhances prediction accuracy for oxygen content, contributing to better cleanliness quality of electroslag steel. This study offers a novel approach for addressing small sample challenges in metallurgical processes. [ABSTRACT FROM AUTHOR]

The impact of transient reoxidation environments on the chemical morphology evolution of nonmetallic oxide inclusions in rare‐earth‐treated bearing steel is investigated using FactSage thermodynamic simulation calculations, vacuum induction furnace experiments, and high‐temperature laser confocal microscopy experiments. Thermodynamic calculations indicate a direct correlation between the initial rare‐earth content and the oxygen required to transform Ce2O2S to CeAlO3 during secondary oxidation. Furthermore, a higher initial rare‐earth content leads to a more extensive and complete conversion to CeAlO3. Vacuum induction furnace experiments reveal that the inclusions transform from Ce2O2S to CeAlO3 and Al2O3 and eventually into composite oxide clusters. This results in a significant increase in inclusions, with near‐spherical Ce2O2S inclusions transforming into aggregated CeAlO3, leading to an increase in the average inclusion size from 2.4 to 4.2 μm. Laser confocal scanning microscopy experiments show that CeAlO3 exhibits a higher tendency to aggregate than Ce2O2S inclusions, the primary factor contributing to the observed increase in the average inclusion size after secondary oxidation. The results of this study provide theoretical guidance for mitigating the adverse effects of rare‐earth secondary oxidation on bearing steels, particularly in terms of inclusion control. [ABSTRACT FROM AUTHOR]

By means of salt‐bath austempering treatment, microstructure observation, X‐Ray diffraction analysis, microhardness measurement, and friction and wear performance tests for 8Cr4Mo4V steels with standard composition and with trace addition of 0.005% boron, the effect of boron on the phase composition and mechanical properties of the steel is studied. The results show that trace element boron greatly increases the content of needle‐like lower bainite in the quenched microstructure, promotes the dissolution of undissolved carbides, reduces the content of M/A island, but coarsens grains. After tempering, trace element B increases the amount of bainite generation, refines the lath martensite, and significantly promotes the precipitation of carbides, whose size is finer, and the distribution is more dispersed. In terms of mechanical properties, trace element B improves the hardness by promoting the precipitation of the second phase and refining the lath martensite, and the increase in the bainite content changes the wear mechanism and enhances the wear resistance. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties and microstructures of bearing steels with arsenic contents of 30, 40, and 120 ppm have been investigated. The results show that As‐40 steel has the highest tensile strength but lower fatigue strength than As‐120 steel. The fatigue crack propagation rate of As‐120 steel is relatively low, mainly due to the increase in ΔKth. After quenching and tempering, As‐120 steel has larger prior austenite grains and more undecomposed, elongated carbides appear, reducing the uniformity of the steel. For carbides with an aspect ratio greater than 2, they cannot grow by the Oswald mechanism of spontaneous migration but are spheroidized by self‐cracking. The undissolved elongated carbides have a lower chemical potential, which increases the diffusion tendency of arsenic in the matrix. SIMS and EPMA analyses show that there is no significant distortion of the trace element arsenic. Highlights: The arsenic content in bearing steel has property advantages within the optimal range.Trace element arsenic will diffuse near low chemical potential strip carbides.A certain amount of arsenic coarsening grains can improve the fatigue strength of steel [ABSTRACT FROM AUTHOR]

Steel structures are typically engineered for the upper range of the steel toughness‐temperature curve. To account for the reduction in toughness properties within the temperature transition range, additional safety assessments are necessary. These assessments rely on fracture mechanics considerations and enable the selection of an adequate steel material to prevent brittle fracture. Considering this context, recommendations were already put forth in 2011 to govern the appropriate choice of steel grades for bearing components. However, these recommendations are no longer entirely current in light of more recent findings. As a result, the German Centre for Rail Traffic Research has called a research project with the aim to formulate proposals to expand the regulatory framework related to suitable material selection, aimed at preventing brittle fracture in bridge bearings. [ABSTRACT FROM AUTHOR]

Machine learning (ML) accurately predicts the shear bearing capacity of steel tube‐reinforced concrete (STRC) shear walls, aiding optimization design. However, creating a database for STRC shear walls experimentally is time‐consuming and costly. The aim of this study is to propose a method for high‐accuracy prediction of STRC shear wall shear bearing capacity using a small‐sample dataset. This study employs generative adversarial network (GAN) data augmentation techniques to address the issues of insufficient ML model training and low prediction accuracy in small‐sample databases. Based on the stacking framework, a fusion model (Stacking‐XRL) combining extreme gradient boosting (XGBoost), random forest (RF), and least absolute shrinkage and selection operator (LASSO) is established to predict the shear bearing capacity of STRC shear walls. Results show that after augmenting the training set with GAN, the prediction performance of K‐nearest neighbors (KNN), backpropagation neural network (BPNN), RF, light gradient boosting machine (LightGBM), XGBoost, and stacking‐XRL models significantly improve, with average increases of 10% in R2 and average decreases of 30% and 25% in MAE and RMSE, respectively. The proposed stacking‐XRL fusion model outperforms tested models, existing formulas, and Abaqus numerical simulations for the shear bearing capacity of STRC shear walls. Model interpretation reveals that the shear span ratios as the most important factors in predicting shear bearing capacity, followed by axial force ratio and whole section configuration steel tubular index. [ABSTRACT FROM AUTHOR]

The submerged entry nozzle (SEN) is an indispensable functional structural ceramic in the current continuous casting production. The stability and safety of the SEN is very important during the casting process. In this article, the functional failure of the SEN during the continuous casting process of the bearing steel GCr15 is studied. The results show that the functional failure of the SEN during the bearing steel GCr15 casting process is caused by the clogging inside the SEN which is led by the low cleanliness and the high impurities n the molten steel. The clogging in the SEN can be divided into solidified steel area, loose area, dense area, and surface area. To improve the castability of bearing steel or other high‐cleanliness steel, it is necessary to strengthen the refining process and treatment effect, strengthen the sealing and the effect of the protective casting of the molten steel, and moderate optimization of nozzle materials or the application of external fields on the SEN. [ABSTRACT FROM AUTHOR]

The partial factor method is widely employed as a design approach for structural reliability and serves as a crucial foundation for structural design codes. However, in practical applications, this method has gradually revealed shortcomings, such as issues with generality and insufficient precision in reliability control. In this article, an improved design value method for the bearing capacity design of steel plate strengthened RC beams was established. Additionally, considering the impact of the live‐to‐dead load effect ratio on the partial safety factor of resistance, a simplified expression for the ultimate limit state design of bearing capacity was proposed. The results show that the reliability index calculated using the partial factor method for the bearing capacity of steel plate strengthened RC beams has a significantly larger relative error. In contrast, the reliability indexes calculated based on the improved design value method are all greater than the target reliability index, ensuring the requirements of reliability design and providing a higher degree of precision in reliability control. [ABSTRACT FROM AUTHOR]

Strengthening planning for the Chemnitz Viaduct from the perspective of the checking engineer The Chemnitz Viaduct was built for four‐track traffic with a length of 275 m between 1901 and 1909. After 120 years of use, it had to be technically repaired and strengthed for the use for another 80 years. The bridge consists of four parallel superstructures, each spans over two arches and ten beam bridges. For future double‐track traffic, the two inner superstructures were equipped with tracks for rail traffic, and the two outer superstructures were used for side and emergency sidewalks as well as for technical equipment. For this purpose, the inner beam bridges were replaced and designed as a steel composite structure. The substructures and other superstructures were largely preserved in accordance with the requirements of monument protection and renovated or replaced in small parts as necessary. Particular attention was paid to preserving the large number of historical steel bearings. The structural implementation of this complex project under "rolling wheels" required special measures for ongoing railway traffic. In this article, after an overview of the historical building and its assessment, the work in the advisory board is discussed and the handling of various measures for technical repairs and strengthenings, taking into account the monument protection in conjunction with the additional necessary permits and approvals. [ABSTRACT FROM AUTHOR]

The effects of Ce on inclusions and the primary carbide network of AISI 440C bearing steel are experimentally and theoretically investigated. Adding Ce improves the cleanliness and refinement of primary carbide networks in AISI 440C bearing steel ingots. The addition of Ce substantially reduces the contents of total oxygen (T.O) and S in the steel, and MnS and Al2O3 inclusions are modified into finer Ce‐containing inclusions (Ce2O2S and Ce2O3). When Ce is added, the average equivalent diameter of the inclusions decreases from 1.82 to 1.33 μm, and the number of inclusions per unit area (mm2) increases from 59 to 105. Moreover, the addition of Ce reduces the secondary dendrite spacing from 33.82 to 24.2 μm, and the proportion of primary carbide is reduced from 22.08% to 11.17%. The 2D lattice disregistry theory confirms that Ce2O2S and Ce2O3 inclusions can be utilized as effective heterogeneous nucleation cores for γ‐Fe, thus refining the solidification microstructure and also the primary carbide. This study provides theoretical guidelines for the fabrication of domestic AISI 440C bearing steel ingots. [ABSTRACT FROM AUTHOR]

High‐nitrogen stainless bearing steel (HNSBS) is the most representative third‐generation aviation bearing steel, and the cleanliness and microstructure characteristics of bearing steel are crucial to its high performance and long service life. In this work, the effect of cerium addition on the cleanliness and microstructure characteristics of as‐cast HNSBS was systematically studied by combining microstructural characterization and thermodynamic analysis methods. The results show that with increasing Ce content, the cleanliness of steel first improved and then decreased, and Ce2O2S, Ce2O3 and CeN inclusions were generated successively. The Ce content should be controlled to ≈0.012 wt% to ensure that all Al2O3, MgO · Al2O3, and MnS inclusions were modified, and minimize the formation of large‐size Ce‐bearing inclusions. Furthermore, cerium addition refined the dendrite structure due to more nucleation sites for γ‐Fe and the enrichment of Ce in the liquid phase at solidifying front. The finer and more dispersed distribution in precipitates was ascribed to the reduction of growth space and Cr segregation, as well as the increase in effective nucleation sites. These results can offer theoretical guidance for inhibiting the formation of harmful inclusions in high‐nitrogen alloy systems and refining the microstructure of alloy systems containing M23(C, N)6 and M2(C, N) precipitates. [ABSTRACT FROM AUTHOR]

Numerical investigations as part of the assessment of the historic bearings of the Chemnitz viaduct As part of the refurbishment of the Chemnitz viaduct in line with monument protection requirements, the cast steel bearing components also had to be assessed. This required extensive numerical calculations in order to carry out the verifications in the ultimate limit state and the serviceability limit state. The results of the finite element calculations, taking into account the exceptional combination of actions and unit load cases, served as input parameters for fracture mechanical investigations to assess the risk of brittle fracture and to verify safety against fatigue. Non‐destructive and destructive tests as well as casting simulations and 3D scans completed the state assessment and thus the overall assessment of the cast bearings. Complex load conditions, such as impressed stress conditions from initial plasticization, were taken into account by means of non‐linear calculations with loading, unloading and reloading. The numerical calculations are presented in this article, in addition to the explanations regarding the other components of the assessment in the first part of this paper, and exemplary results are shown. The detailed recalculation was an important basis for the continued use of a large part of the bearing components. [ABSTRACT FROM AUTHOR]

White etching area (WEA) is a primary damage in rolling contact fatigue (RCF) of bearing steels. In spite of extensive investigations, there is a large discrepancy in the existing mechanisms of WEA formation. We attempt to unify the mechanisms from the perspective of shear localization and plastic damage accumulation based on ductile damage. RCF tests were conducted to generate WEAs with various microstructures and compositions. A thermodynamically consistent model of the ductile damage evolution from an inclusion was established by developing the phase field damage coupled with the crystal elastic‐viscoplastic constitutive relationship under RCF. The model was implemented into the FE framework through a user materials subroutine. The results indicated that the WEA is the shear band resulting from shear localization. The large inhomogeneity and scatter in WEA's microstructure are due to the influence of the crystal orientation. The development and orientation of SBs predicted by the model and the experimental observation of the WEA are in good agreement. The large micro‐shear strain in the WEA provides the driving force for mechanically controlled austenite phase transformation. The shear band center, which has the largest strain and the least stress, is where cracks initiate. This demonstrates that contrary to earlier reports that WEA is induced by previously formed crack faces friction, cracks actually initiate from the interior of the WEA. Highlights: WEA presents the form of shear band as a result of shear localization.WEA's orientation is significantly influenced by the crystal orientation.Large micro‐shear strain in WEA is the driving force for phase transformation.Instead of WEA being induced by friction of crack faces, cracks begin in WEA. [ABSTRACT FROM AUTHOR]

The hierarchical martensite structure of secondary hardening low‐carbon high‐alloy bearing steel at different solution temperatures is characterized in detail, and the effect of microstructural evolution on mechanical properties of the experimental steel is studied. The results show there are a large number of micron‐M6C at the boundary of the prior austenite grain when the solution temperature is 1,000–1,025 °C, which is conducive to hinder the growth of the prior austenite grain and produces smaller packets that improve the yield strength of the material. At the same time, such micron‐M6C is prone to stress concentration when the material is subjected to an external force load, which can severely reduce the material toughness. The M6C completely dissolves into the matrix when the solution temperature exceeds 1,050 °C, and the packets size grows rapidly with the prior austenite grain size. At this point, the effect of packets on yield strength no longer dominates, and the rate of decrease in yield strength tends to be gradual. Under the comprehensive function of the micron‐M6C‐remelting, the martensitic blocks refinement, the increased number of the Σ3 grain boundaries, and the growth of cracks can be hindered, and the toughness of material can be improved accordingly. [ABSTRACT FROM AUTHOR]

Rolling contact fatigue tests were performed on specimens containing spheroidal inclusions to clarify the effect of the orientation of inclusions, and the results were compared with those of specimens containing stringer‐shaped inclusions. For all types of inclusion, cracks first formed on the rolling surface and then propagated in the depth direction, and an internal crack parallel to the rolling surface formed from the deepest point of the vertical crack, which led to flaking. The flaking life of the specimens with spheroidal inclusions was longer than that of the specimens with stringer‐shaped inclusions, where the initiation and propagation lives of cracks were affected by the inclusion shape and size. The surface crack initiation life was shorter for specimens with longer surface inclusions, whereas the crack propagation life decreased with the depth of surface inclusion. The greater the scatter of the size of inclusions, the greater the scatter of flaking life. Highlights: In every orientation, formation of surface crack precedes formation of interior crack.Flaking life of spheroidal inclusion was longer than that of stringer‐shaped inclusion.Surface crack initiation life was shorter for longer inclusions at the surface.Lateral crack propagation life was shorter with increasing inclusion depth. [ABSTRACT FROM AUTHOR]

By comparing the advantages and disadvantages of the existing single‐step pressurized metallurgical manufacturing technologies of high nitrogen stainless steel (HNS), a promising pressurized duplex manufacturing route, i.e., pressurized induction melting (PIM) and pressurized electroslag remelting (PESR), is proposed. The PIM stage mainly carries on the nitrogen alloying, deoxidation and desulfurization, and the PESR process mainly takes responsibility for further desulfurization, removal of large‐size inclusion, and elevating solidification quality. During PIM, the deoxidation is achieved by vacuum carbon deoxidation combined with magnesium and rare‐earth compound treatment. Subsequently, the PESR is conducted under high nitrogen pressure without adding nitrided ferroalloys. To precisely control the nitrogen content and avoid segregation and escape of nitrogen, the three‐stage nitrogen pressure collocation is developed. The high nitrogen stainless bearing steel 30Cr15Mo1N (DIN 1.4108) is manufactured as an example by the duplex route, and a PIM–PESR ingot with high nitrogen content, high cleanliness, fine and dispersive inclusions, and compact solidification structure is obtained. Moreover, the steel possesses a homogeneous microstructure, slightly better mechanical properties, and corrosion resistance compared with that manufactured by the single‐step PESR process. Finally, a pressurized ladle refining and PESR duplex route are proposed for large‐scale industrial production of HNSs. [ABSTRACT FROM AUTHOR]

This paper investigates the suitability and interpretability of a data‐driven deep learning algorithm for multi cross sectional overstrength factor prediction. For this purpose, we first compile datasets consisting of experiments from literature on the overstrength factor of circular, rectangular and square hollow sections as well as I‐ and H‐sections. We then propose a novel multi‐head encoder architecture consisting of three input heads (one head per section type represented by respective features), a shared embedding layer as well as a subsequent regression tail for predicting the overstrength factor. By construction, this multi‐head architecture simultaneously allows for (i) the exploration of the nonlinear embedding of different cross‐sectional profiles towards the overstrength factor within the shared layer, and (ii) a forward prediction of the overstrength factor given profile features. Our framework enables for the first time an exploration of cross‐section similarity w.r.t. the overstrength factor across multiple sections and hence provides new domain insights in bearing capacities of steel cross‐sections, a much wider data exploration, since the encoder‐regressor can serve as meta model predictor. We demonstrate the quality of the predictive capabilities of the model and gain new insights of the latent space of different steel sections w.r.t. the overstrength factor. Our proposed method can easily be transferred to other multi‐input problems of Scientific Machine Learning. [ABSTRACT FROM AUTHOR]

A new composite column system using a solid core and an encasing jacket made from (ultra‐)high‐strength structural steel filled with concrete is presented in this paper that can serve as a promising alternative to prefabricated reinforced concrete columns from an economic and constructive point of view. Within the scope of a research project, this topic is being investigated in more detail by means of numerous experimental and theoretical investigations to enable the use of (ultra‐)high‐strength steels in the future. In this article, stub column tests were carried out to assess the resistance to pure compression and to gain insights into the structural performance of this new composite column system. Novel measurement techniques are used to evaluate the different normal force bearing components of the steel core, the hollow steel section, and the filled concrete over the entire loading process. A clear dependence of the load‐bearing behaviour on the cross‐sectional shape and the load introduction form (full‐surface load introduction vs. load introduction via the core surface) was observed. [ABSTRACT FROM AUTHOR]

According to the variation in the average composition, the average size, the number density, and the area fraction of large‐size inclusions during Ruhrstahl Heraeus (RH) refining process, large‐size inclusions in the high‐carbon chromium‐bearing steel reach the lowest level when the vacuum cycle time is 25 min. When the soft blowing time reaches over 25 min, the number density and area fraction of large‐size inclusions increase. The rolling contact fatigue (RCF) life of the forged steel samples is measured using a thrust RCF tester, indicating that the fatigue life of no. 1 steel (vacuum cycle 40 min, soft blowing 20 min) is 12% higher than that of no. 2 steel (vacuum cycle 20 min, soft blowing 40 min). Based on the estimation of the characteristic size of inclusions in the forged steel by the statistics of extreme values (SEV) method, it is concluded that when the characteristic size and the chemical composition of inclusions in steels are similar, the RCF life is increased by 12% when the number density of large‐size inclusions decreases from 0.63 to 0.44 mm−2. [ABSTRACT FROM AUTHOR]

High‐frequency pressure pulsations are hydraulic phenomena that are frequently observed in pumped storage power stations. These pulsations can propagate through the steel pipes, concrete lining, and the surrounding rock system, which in turn may have detrimental effects on the environment, such as noise pollution, and relocation of the local residents. This paper proposes a vibration‐damping concept that involves wrapping a local soft cushion layer outside the buried steel pipe; this layer could partially eliminate the pressure fluctuations in the headrace tunnel, thereby reducing the ground vibrations caused by the pressure pulsations. In this study, the finite element method was used to model the propagation of vibrations in the surrounding rock and fluid‐filled pipes, including static simulation of the structure, and dynamic simulation of the surrounding rock. The simulation results suggest that adding an appropriate local soft bedding layer can effectively reduce the ground vibrations by more than 60% and the possible surface noise within the standard vertical vibration norms. The inhibitory effect of the soft cushion on the propagation of vibrations is determined by the wrapping angle, thickness, and material of the bedding layer. This effect increases with increasing wrapping angle and thickness of the bedding layer, and decreases with increasing elastic modulus of the material. After the addition of the bedding layer between the steel pipe and concrete lining, the pressure in the inner pipe is primarily borne by the steel lining rather than the coupling of the steel lining, concrete lining, and the surrounding rock. Hence, the thickness of the part of the steel liner in contact with the soft bedding layer should be increased. In addition, the thickness variations in the steel pipe joints should be smooth to avoid stress concentration. Highlights: This paper proposes a vibration‐damping concept of partially wrapping a soft cushion between the buried underground steel pipes and the concrete.Owing to the additional bedding layer, the pressure pipe needs to be appropriately strengthened. Finite element static structural simulation is used to develop and verify a design that satisfies the structural strength requirements.Finite element dynamic response simulation was done for the mountain surrounding the pumped storage power station and underground buried pipe system to evaluate the ground acceleration and vibration‐damping behavior for various bedding layers. [ABSTRACT FROM AUTHOR]

Cr4Mo4Ni4V steel has excellent fracture toughness and fatigue life, which is one of the main materials for the new generation of aeroengine bearing rings. However, there is still lack of investigation on hot processing of Cr4Mo4Ni4V steel up to now. Herein, the hot processing map is established based on systemic compression tests; then, according to the requirements of Cr4Mo4Ni4V steel for carbide content, improved hot processing map is established based on the carbide content by superimposing the carbide content zoning map. Results reveal that the activation energy is 304.9 kJ mol−1, and power dissipation value increases only within the strain range of 0.2–0.4, while the instability zone always moves toward the direction of high strain rate with the increase of strain. In 900–1150 °C, 0.01–5 s−1, the content of carbide could be divided into three zones: little dissolved zone, mostly dissolved zone, and completely dissolved zone. Improved hot processing map indicates that the ideal processing domain is 950–1050 °C, 0.01–0.3 s−1 etc. [ABSTRACT FROM AUTHOR]

The paper presents the experimental studies on the enhanced comprehensive properties of Cr4Mo4V bearing steel using ultrasonic surface rolling process. Considerable improvements in mechanical properties and rolling contact fatigue performance are achieved in the present study, accompanied by the characterization of surface microstructures. The ultrasonic surface rolling process promotes the formation of fine nanocrystalline structures and nano‐sized elongated grains with severe deformation, leading to the increasing residual stress, micro‐hardness and high temperatures hardness. The crack propagation and delamination pit in the surface after ultrasonic surface rolling process is inhibited, further enhancing the rolling contact fatigue life of Cr4Mo4V bearing steel. [ABSTRACT FROM AUTHOR]

The fatigue life prediction of the bearings is a crucial and challenging issue, especially under random cyclic loadings. Although numerous methods have been proposed, the remaining useful life of bearings is still unclear. In this study, the tensile and fatigue properties of high‐speed train bearings after various operating mileages were investigated. The experimental results reveal that the microhardness, tensile strength, elongation, and fatigue strength of the bearing steel present a downward trend with increasing the operating mileage. Based on Miner's law, we proposed the generalized linear cumulative damage theory, which illustrates that fatigue damage of components per unit mileage can be linearly superimposed. Accordingly, the residual strength model was established to evaluate the fatigue life of high‐speed train bearings. It would provide a new insight for the fatigue life prediction of bearings under random loadings. Highlights: The fatigue damage behavior of high‐speed train bearings was systematically explored.The tensile and fatigue strength show a downward trend with the operating mileage.The fatigue life calculated by residual static/fatigue strength is 10–27 and 6 million km.It provides a new insight into the fatigue life prediction of engineering components. [ABSTRACT FROM AUTHOR]

This paper presents a detailed analysis of the nucleation and propagation of surface‐initiated crack in rolling contact fatigue (RCF) of bearing steel under heavy load. The cracks initiated from the junction of machining marks and trailing edge of dents formed by the plastic deformation. Crack propagation and spalling were mainly composed of three stages: (1) cracks initiating from surface defects propagate downward to form small spalling pits; (2) due to the surface stress and the maximum Hertz stress form a stress bridge, the cracks continue to expand towards the Hertz stress peak forming big spall; (3) the trailing edge of the spalling pit is used as the stress raiser to initiate next subsurface cracks and spalling expansion in successive. Different from previous understanding on the formation of subsurface‐initiated spalling, the results indicate that under heavy load the spalling at depth of the maximum shear stress zone in the subsurface can initiate from surface cracks. Highlights: Discovering that the spalling at depth of the Hertz stress zone in the subsurface can be caused by the initiation and propagation of surface cracks.Explaining in detail both initiation and propagation of surface‐initiated RCF damage that the spalling is formed by stepwise expansion.The stress variations involved in the formation of spalling are explained. [ABSTRACT FROM AUTHOR]

Non alloyed carbon deoxidation can fundamentally solve the technical difficulty of fatigue failure of high‐quality bearing steel caused by inclusions. Herein, nonalloyed carbon deoxidation is presented with CO as a product, which can avoid the problem of residual inclusions. The thermodynamic and kinetic nucleation models of [C] deoxidation are constructed. The results suggest that a decrease in pCO strengthens the deoxidation ability of [C], and the [%O] balanced with [%C] shows multiple decreases. When pCO = 0.1 atm and [%C] = 0.5%, [%O] can be reduced to less than 10 ppm. However, from the results of the nucleation kinetic model, as pCO decreases, the critical radius r* increases, and the resistance of CO nucleation also increases. This results in difficulty of nucleation. Based on the nucleation kinetic model, the following C–O reaction mechanism is proposed: 1) [C] and [O] move to the reaction interface, 2) [C] + [O] = CO, forming a critical bubble nucleus, and 3) the newly formed CO diffuses continuously into the critical bubble, causing the bubble to grow and float away. Alternatively, the CO separates from the gas–liquid interface and enters the bubble, which floats away. [ABSTRACT FROM AUTHOR]

Universal high‐performance columns made of high‐strength steels without welding In recent years, steel‐concrete composite columns made of normal‐strength steels are seldom used owing to the economic and technological advantages of precast reinforced concrete columns. Though, the use of high‐strength structural steels bears high potential for the efficient production of composite columns with excellent structural performance that are economically competitive to precast concrete columns, there are currently major obstacles to use of the ultra‐high‐strength steels (UHSS) in Germany. Hollow section composite columns with embedded high strength steel core without welded connections provide an opportunity to regain lost market share. A research project, funded by the AiF (Arbeitsgemeinschaft industrieller Forschungsvereinigungen), is intended to explore the potential of UHSS composite columns by experimental and theoretical investigations. The present paper demonstrates the concept of such composite columns with UHSS and gives first exciting insights into the research results. In addition to column tests under ambient and fire conditions, small scale tests are necessary to investigate various influencing factors and to create the basis for new and easy to use design and construction principles that allow efficient application. [ABSTRACT FROM AUTHOR]

In the current study, laboratory experiments of the slag‐steel reaction are performed to investigate the effect of CaF2 contents in the refining slag on the inclusion absorption of the bearing steel. The increase of the CaO/Al2O3 ratio effectively enhances the absorption of inclusions by slag. The increase of the CaO/Al2O3 ratio enhances the driving force of the inclusion dissolution and lowers the slag viscosity. It is noted that the excessive CaO/Al2O3 ratio led to the formation of solid phases in the slag, lowering the absorption effect of slag. The appropriate addition of CaF2 in the slag is helpful to remove inclusions while aggravating the corrosion of MgO crucibles. The addition of CaF2 mainly reduces the viscosity and melting temperature of slag. The inclusion removal factor is proposed to effectively evaluate the inclusion removal rate in steel during slag steel reaction. As a result, the most recommended composition of slags is 7% CaF2; the CaO/Al2O3 ratio is 2.0. [ABSTRACT FROM AUTHOR]

The process of fatigue spalling in the rings of ball bearings at durability exceeding 108 cycles under in‐service loading conditions is analyzed on the basis of fractography and the slices prepared in radial planes of rings. The cracks are shown to originate at subsurface from carbides inherent in the bearing steel or inclusions permissible by sizes for the material. Subsequently, the development of cracks perpendicular to the ring raceway surface takes place similarly as in the very‐high‐cycle fatigue (VHCF) regime with the elliptical "fish‐eye" formation. The subsequent crack growth was demonstrated step‐by‐step up to the ring material fragment separation. The total crack path by alternating stops of propagation and new crack nucleation under conditions of mixed‐mode I + II + III mechanisms with the crack branching was discussed. In the final stage, the crack grows towards the ring raceway and either appears on the raceway surface or coalesces with a similar adjacent crack followed by fatigue spalling formation. Highlights: VHCF regime of bearings under conventional service conditions is demonstrated.Review of fatigue spalling process in bearings under RCF conditions is presented.Features of crack origination in VHCF fracture of ball‐bearings are shown.Sequence of fatigue cracking from the initiation up to spalling formation is discussed. [ABSTRACT FROM AUTHOR]

Eight groups of "Z" joint specimens were designed for conducting direct shear tests on steel keyed joints. The shape, size, number and joint type of steel keys were taken as experimental parameters, and the cracking load, ultimate load, residual load, and the relationship between vertical loading force and vertical relative displacement of specimens were investigated. The results reveal that the joints relied on the mechanical occlusion between the steel keys and concrete to transmit the shear forces, the load–displacement curve of the joints had a long development course, and the joints could bear large relative displacement. The bearing capacity of steel shear keyed joints increased with the increase in diameter and material strength of the tenon. The ultimate bearing capacity of the epoxied joints with 1 and 2 steel keys were respectively 151.39%, and 69.68% higher than dry joints. Meanwhile, the epoxied joints were found to become brittle and fail in more sudden manner. After direct shear failure, the shear resistance of epoxied joints was completely provided by the steel shear key. The elastic stiffness and bearing capacity of the epoxied joints was not controlled by the number of the steel shear keys, while the dry joints were sensitive with the number of keys. By adding 1 or 2 steel shear keys to a flat joint, the ultimate bearing capacity could be increased by 3.81 and 6.06 times for dry joints, and 43% and 33% for epoxied joints, respectively. [ABSTRACT FROM AUTHOR]

An axial static magnetic field (ASMF) is superimposed during the electroslag remelting (ESR) process to regulate the inclusion removal (GCr15 bearing steel) in the current study. After applying a 50 mT ASMF, the metal pool of the ESR ingot becomes shallower and the solidified dendritic structure tends to grow axially, together with a higher inclusion removal efficiency. The number of inclusions in ESR ingot decreases, and the inclusion with larger size (>10 μm) is almost eliminated. By tailoring the morphology of the liquid melt film (LMF), droplet, and metal pool, the ASMF applied in this study strengthens the kinetic conditions (inclusion migrated to slag/metal interface) for the inclusion removal, thus realizing the multi‐stage enhanced removal of inclusion during ESR process. [ABSTRACT FROM AUTHOR]

Nowadays, deep cryogenic treatment (DCT) is taken as a promising technique for improving the performance of steel. This article is focused on the influence of different heat treatment processes involving DCT on the microstructural evolution of a high Cr–Co–Mo high‐temperature‐bearing steel. Moreover, a multiphysical field coupling numerical model is built to investigate the martensitic transformation kinetics during DCT. The results show that DCT significantly improves the hardness and promotes the transformation of retained austenite to martensite at low temperatures. DCT not only refines the retained austenite as thin‐film morphology but also increases the precipitation of carbides and induces the carbides more homogenous distribution. This indicates that DCT promoted the segregation of carbon atoms and reduced the carbon content of martensite. The finite element model simulation shows that the retained austenite transformation is still incomplete, and the simulation results agree well with the experimental data by X‐Ray diffraction and transmission electron microscope analysis. This implies that the finite element simulation can better reflect and verify the experimental results. [ABSTRACT FROM AUTHOR]

The roller‐straightening process is a steel cold production technique which consists of passing a steel element through a series of rolls that bend the member, what leads progressively to a reduction of the initial geometrical imperfections along its weak axis. In addition, this post‐treatment process induces a continuous yielding of the steel member and thus may present a second interest which is the reduction of the compression residual stresses at flange tips. This modification of the residual stress pattern could lead to an increase of the carrying capacity of steel columns. Indeed, the capacity of columns in compression is evaluated through the European buckling curves reported in EN1993‐1‐1 in which the compression resistances are highly affected by the initial bow imperfections and residual stresses resulting from the rolling process. However, whilst all long products seem to be systematically straightened nowadays, EN1993‐1‐1 does not consider the potential beneficial effect of the roller‐straightening process. In other words, it means that the current recommendations of EN1993‐1‐1 neglect the potential benefit of this process on the buckling capacity. In this context, a collaboration for a research study has been initiated between ArcelorMittal and the University of Liège to numerically estimate the residual stress patterns after the roller‐straightening process of three relevant heavy H‐shape profiles (HE 600 B, HE 500 M and HD 400 x 262) in HISTAR®460 and evaluate whether these new distributions could lead to a significant increase of the column bearing capacity. [ABSTRACT FROM AUTHOR]

By using field‐emission scanning electron microscope (SEM), transmission electron microscope (TEM), X‐Ray diffraction (XRD), and tensile‐property tests, the effect of cold treatment temperature on size stability and mechanical properties of M50 bearing steel is studied. Results show that when the thermal treatment temperature is fixed to be 440 °C, the number of precipitated secondary carbides (SC) in the steel increases first and then decreases with the decrease of cold treatment temperature in the range of −50 to −90 °C. The amount of the precipitated carbides and the transformed residual austenite (RA) reaches the maximum at −70 °C. Carbide precipitation during cold treatment reduces the size of M50 steel, while martensitic transformation leads to the size increase. The size change of M50 steel is the smallest at −80 °C, about 0.5 μm. The elongation of the steel is 3.16% before stabilization treatment, which is improved after stabilization treatment under different conditions. The tensile strength and yield strength decrease at −60 °C and increase at −80 °C, and the other cold treatment temperature has little effect on the tensile strength of the steel. [ABSTRACT FROM AUTHOR]

Herein, by using scanning electron microscopy, transmission electron microscope, X‐ray diffraction, residual stress analyzer, and mechanical‐property tests, the effect of minor carburizing on the microstructure and mechanical properties of M50 steel is studied. It is shown in the results that after minor carburizing, the austenite content in the surface layer of the quenched M50 steel increases, while the martensite content and the hardness decrease. After tempering, the retained austenite in the surface layer is transformed into martensite, and a large amount of uniformly distributed carbides are precipitated. The hardness of the surface layer increases to exceed that of the core region in the steel. After the minor carburizing, there is a carbon concentration gradient between the surface layer and the core region of the M50 steel, which influences the phase transformation behavior and the residual stress state in the surface layer during the tempering process. Minor carburizing increases the rotational bending fatigue limit of the steel by 16.7% and improves the tensile strength, yield strength, and impact absorption energy of the steel. [ABSTRACT FROM AUTHOR]

A new double vacuum melting route (conventional second refining + vacuum arc refining [CSR + VAR]) with 33% lower production cost than the traditional VIM + VAR route has been tried. Compared with the CSR route, the CSR + VAR route reduces the average inclusion size from 27.1 ± 12.3 μm to 13.7 ± 2.4 μm, and the CSR + VAR steel processes a 13.1% higher rotatory bending fatigue (RBF) fatigue strength (σ−1) and a 3‐timeslonger RCF L10 life. The crescent‐shaped granular bright facet (GBF) zone, normally found in high‐strength steels' very high cycle fatigue regimes beyond 107 cycles normally under a much lower stress amplitude, appears around inner inclusions on the CSR + VAR steel RBF fracture surfaces in high cycle fatigue regimes beyond 3 × 105 cycles. The development of GBF zones is estimated to account for 79%–90% of the RBF fatigue life. The average crack propagation rate (da/dN) for GBF zones varies from 1.3 × 10−12 m/cycle to 24 × 10−12 m/cycle and increases with the stress amplitude. Highlights: The new CSR + VAR route is an effective and feasible method to improve cleanliness.The new CSR + VAR route provides a cost 33% lower than the traditional VIM + VAR route.The new CSR + VAR route improves RBF strength by 13.1% and RCF L10 life by 3times.Crescent‐shaped GBF zones are first observed in high cycle fatigue regimes. [ABSTRACT FROM AUTHOR]

The quest for high‐performance energy efficient aircraft turbine engines has led to the development of a number of high‐performance rolling element bearing materials and engine lubricants with the aim of providing superior mechanical component durability. The heat treatments/surface treatments used to achieve the desired physical and mechanical properties for these newer alloys can result in altered surface chemistry from currently used materials. Surface chemistry plays an important role during lubricant‐bearing material interactions and the formation of beneficial tribological films during component operation. The objective of this study was to analyse the tribo‐films formed on bearing surfaces and investigate the interaction of lubricant additives, specifically the phosphorus‐based anti‐wear additive tricresyl phosphate (TCP), with different bearing materials under relevant bearing operating conditions. Bearing tests were conducted on 208‐size (40 mm bore) angular contact bearings at 127°C and 154°C using gas turbine engine lubricants conforming to MIL‐PRF‐23699G at maximum Hertzian contact stresses of 3.1 GPa and 3.55 GPa. Bearing materials evaluated included AISI M50, M50NiL, nitrided M50NiL (N) and three variants of Pyrowear 675 with silicon nitride rolling elements. Tribo‐films were analysed using Energy dispersive X‐ray spectroscopy and Auger Electron spectroscopy. Results indicate that phosphorus‐rich anti‐wear tribo‐films form on all of the bearing materials studied. The applied thrust load and heat treatment had a significant effect on tribo‐film thickness. The study also suggests that current gas turbine engine lubricants formulated with TCP should form beneficial tribo‐films that enhance bearing fatigue life and performance. [ABSTRACT FROM AUTHOR]

Summary: K‐shaped intersecting joint is a common type of joint in steel tubular structures, and its bearing capacity has an important effect on the structural performance. The relevant literatures and design codes are still lacking of the calculation theory on bearing capacity of steel tubular K‐shaped joints stiffened with joint plates, by which the effect of well‐welded stiffeners could not be considered. Four steel tubular K‐shaped joints with or without stiffened plates are designed, and their tests and nonlinear FEAs are carried out to investigate the bearing capacity characteristics, failure modes, and the effectiveness of stiffeners. The tests shown that the stiffened plates can significantly improve the bearing capacities of K‐shaped joints, and the plates should be looked as joint plates to evaluate its contribution to intensity, not just as stiffeners. Then, the parameter simulations and their influences on bearing capacities of stiffened K‐shaped joints are performed, in which the different sizes of chords, braces, and stiffened plates are selected. Compared with the test and simulation results, the bearing capacity of tubular K‐shaped joints with no stiffened plates could be calculated well by the theory in the relevant design codes. Using the superposition method of bearing capacities, the annular strength model and the calculation theory of stiffened tubular K‐shaped joints are proposed, in which the coefficients of multiparameter model are determined through regression analysis. Lastly, the theoretical bearing capacities of stiffened K‐shaped joints are analyzed and have good agreements with the test values. It can be concluded that the proposed calculation theory can be used to calculate the bearing capacity of stiffened K‐shaped joints with plates. [ABSTRACT FROM AUTHOR]

Industrial trials and thermodynamic calculation are carried out to systematically investigate the variation of steel cleanliness and inclusions during the reoxidation of molten steel, steady and unsteady continuous casting process of GCr15 bearing steels. Comparing with inclusions in molten steel, the content of Al2O3, CaO, CaS, and MgO of inclusions in the steady bloom is increased by 2.17%, −18.47%, 14.01%, and 2.27%, respectively, due to the reoxidation of molten steel will inhibit the transformation of inclusions. As the casting length in the first bloom increases from 2 to 9 m, the total oxygen (T.O) content reduced from 12.9 to 7.2 ppm and the number density of inclusions decreases from 15.65 to 10.97 # mm−2 with a gradual decrease in Al2O3 content. Based on thermodynamic consideration, in molten steel, the lower content of T.O, the lower Al2O3 content of inclusions. For solid steel, with the increase in content of T.O, mainly the Al2O3 content of inclusions gradually increases and the CaS content gradually decreases when the T.O content is between 4 and 8 ppm. However, the Al2O3 and CaO content of inclusions gradually increases, then the MgO and CaS contents gradually decreases when the T.O content is between 8 and 25 ppm. [ABSTRACT FROM AUTHOR]

During the past few decades, concentrically braced frames (CBFs) have become a commonly used load-resistant bearing system in steel structures, to overcome the post-earthquake performance issues frequently associated with conventional seismic-resisting structural systems. CBF systems have high lateral stiffness and lateral strength; however, they have low ductility and a low seismic energy dissipating capacity. Under seismic loading, the diagonal members of a CBF system are susceptible to buckling, causing hysteresis in the compression zone and severely reducing energy absorption. Although the use of steel dampers to enhance the behavior of CBF systems can prevent the buckling of CBF members and improve the hysteretic behavior of braces, their use imposes additional costs on structures. Therefore, in this paper, an I-shaped steel damper with a shear yield mechanism is introduced which is economical, has a simple construction, and can be easily replaced after an earthquake. The proposed damper is evaluated numerically and parametrically. The results indicate that the proposed damper acts as a ductile fuse that prevents buckling of the diagonal members of a CBF system. It was found that both the web and flange plates contribute to the shear resistance, with the flange carrying approximately 15% of the shear force, as expressed in the equations presented. The overstrength obtained for the damper was found to be greater than the value of 1.5 proposed by the AISC. Equations are presented for the design of the proposed damper and the brace elements connected to the damper. [ABSTRACT FROM AUTHOR]

A calculation method for the fatigue limit of components made of high‐strength steels that fail at inclusions is described. The method consists of two parts: first, the size of failure‐critical inclusions is determined based on metallographic investigations. Then, the fatigue limit is determined based on the expected inclusion sizes using a fracture mechanics model. Influencing factors such as sample size, heat‐treatment conditions, and mean stresses are considered. The model parameters are derived from fatigue test data collected over decades within the framework of several research projects. The dominant influencing factors are the inclusion size and the hardness of the steel matrix. Finally, the model is used to predict the fatigue limit of different specimens made of a bearing steel SAE 52 100. The sizes of failure‐critical inclusions and fatigue limits calculated with the model are compared and evaluated on the basis of the inclusion sizes found in the samples' fracture surface and the experimentally determined fatigue limits. [ABSTRACT FROM AUTHOR]

When the soft rock roadway in underground mine is supported by steel frame, the bearing capacity of steel structure is the key to the success of roadway support. Taking the soft rock roadway support in Mengnuo lead‐zinc mine as an example, this paper studies the displacement and stress change law of U‐shaped steel, I‐shaped steel, rail steel, and surrounding rock, analyzes the bearing capacity characteristics of steel structure support, and conducts field application tests. The results show that: (a) the deformation resistance of U‐shaped steel is the best, the overall deformation of which is 85.0% of that of track steel, followed by that of I‐shaped steel, which is 92% of that of track steel, and the deformation resistance of track steel is the weakest in comparison; (b) the main stress positions of the three kinds of supporting steel structures are the joint of the support shoulder and the waist. When simulating the support of 10 m roadway, the deformation of the middle 4‐6 m roadway is larger than that of the surrounding rock of the head and tail roadway; (c) when the horizontal stress of the deep soft rock roadway is larger, the floor heave of the roadway is larger than that of the shallow roadway only when the side and top support are used; (d) by the analysis of three different forms and stress states of support steel structures, it is found that the shape of support has a great impact on the bearing mechanical characteristics. It is of great value to study the shape of support with more bearing advantages under the same amount of steel. [ABSTRACT FROM AUTHOR]

Fatigue tests were carried out on real bearings with various types of artificial defects on their outer‐ring raceways. Finite element analysis (FEM) revealed that the stress intensity factor (SIF) ranges and stress ratios were complex and variable, depending on the gap fittings between the outer rings and housings, as well as on the sizes of the initial defects, both of which influenced the fatigue thresholds of the bearings. In order to establish a comprehensive evaluation of fatigue limits under several combinations of bearing geometries and defect sizes, fatigue crack‐growth thresholds were also measured at different stress ratios by focusing on crack‐closure behaviour. Based on all of the analytical and experimental results, fracture mechanics‐based criteria were proposed for the assessment of fatigue fracture in rolling bearings. [ABSTRACT FROM AUTHOR]

Prof. Ke Yang reviews high-nitrogen nickel-free stainless steel as an attractive biomedical metallic material with high strength, high fatigue resistance, high pitting corrosion resistance and excellent biocompatibility. High-nitrogen steels (HNS) have attracted raised attention due to their exceptional mechanical properties, corrosion resistance and wear resistance. [Extracted from the article]

In the current study, industrial trials are performed to investigate the effect of argon stirring conditions on nonmetallic inclusions of a bearing steel during vacuum degassing (VD). Three argon stirring modes, including strong stirring, moderate stirring, and weak stirring during the last 10 min of the high‐vacuum period, are compared. The removal fraction of >1 μm inclusions and >5 μm inclusions is the highest with the moderate stirring mode, reaching 15.7% and 42.2%, respectively. Inclusions of MgO·Al2O3 are easier to remove than CaO–Al2O3 and entrained CaO–Al2O3–SiO2 ones as MgO·Al2O3 inclusions have a higher coagulation coefficient, a higher contact angle, and a lower adhesion work between the inclusion and the molten steel. Meanwhile, the removal efficiency of inclusions in the bearing steel is in the order of Al2O3 > MgO·Al2O3 > solid CaO–Al2O3 > liquid CaO–Al2O3 and entrained CaO–Al2O3–SiO2. Liquid CaO–Al2O3 inclusions with >5 μm size originate from slag entrainment and can be efficiently removed from the molten steel by the moderate stirring mode. [ABSTRACT FROM AUTHOR]

The service life of roller bearings strongly depends on nonmetallic inclusions (NMIs). Therefore, these steels request highest metallurgical standards in their production. To determine the effect of the Al2O3 content and a protective atmosphere (N2) on the electroslag remelting (ESR) behavior, laboratory scale experiments are conducted. Changes in the composition of the remelted materials and in the slag are determined. In addition, the amount and composition of the NMI prior and after remelting are investigated, and thermodynamic simulations on the formation of NMI are conducted. Changes in the chemical composition can largely be explained by well‐known equilibrium reactions between the slag and the metal. Lowest Al contents in the remelted steel can only be achieved with the Al2O3‐free slag. Higher Al2O3 contents in the slag lead to higher oxygen and sulfur contents in the steel and corresponding higher amounts of NMI after remelting. The use of a protective gas mainly reduced the loss of Si and led to lower O and S contents after remelting with the Al2O3‐free slag. The composition of the NMI changed from alumina type to MgO–Al2O3 (MA)‐spinel type and finally mixed MgO–SiO2 oxides with decreasing Al2O3 contents. These results are confirmed by thermodynamic calculations. [ABSTRACT FROM AUTHOR]

Herein, the thermodynamic and kinetic limitations of carbide dissolution behavior during the traditional heat treatment process are broken through the external field treatment. The difference in electrical conductivity between the matrix and the carbide affects the electric current distribution, which ultimately results in electric field distortion. The numerical calculation results show that under the coupled field of heat and pulsed electric current, the distribution of the current density around the particles is related to the size of the particles. The selective distribution of current caused the energy difference to eventually promote the preferential dissolution of coarse network carbides at grain boundaries. The redistribution of carbon atoms between the grain boundaries and the grain interior provides a good initial structure for the subsequent precipitation process, and finally, uniform precipitation of cementite is achieved in the matrix. Meanwhile, the electromigration of carbon atoms under pulsed electric current increases the diffusion rate of carbon atom and shortens the processing time (traditional heat treatment is about 20 h, and the electropulse‐based method in this study is about 4 h). [ABSTRACT FROM AUTHOR]

In the present study, the diffusion constant for hydrogen in hardened 100Cr6 was measured in permeation tests. The tests were conducted on samples of different thicknesses. The diffusivity of hydrogen was also measured in prestrained samples to study the influence of plastic strain on the diffusion rate. A finite element‐based diffusion model was applied to confirm the experimental results by computing the concentrations of diffusible hydrogen and trapped hydrogen due to deformation‐induced defects. The results showed that the concentration of trapped hydrogen remained very low throughout the plastic strain regime under consideration. The average effective diffusion coefficient of hydrogen in 100Cr6 at 30°C was found to be Deff = 4.9 × 10−12 m2/s. [ABSTRACT FROM AUTHOR]