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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]

The solidification behavior and structure of droplets during the in-flight process play an important role in the final quality of the materials in spray forming. In the study, the macroscopic cooling and microscopic structural evolution of droplets during solidification were simultaneously explored from a multi-scale perspective. Numerical simulations of the cooling and solidification behaviors of droplets in the spray forming of GCr15 bearing steel were carried out by using fluid dynamics and the incorporated solidification models. A model appropriate for estimating the droplet cooling rate of ultrasonic gas atomization (USGA) was developed. The atomic structures and dendrite growth of droplet solidification were studied by molecular dynamics and phase field method. The results show that the thermal history and solidification behavior of a droplet during flight largely depend on its size. The cluster structures during nucleation and solidification of pure Fe droplet transform from the initial dominant FCC-like and ICO-like types to the final BCC structures. Disordered amorphous structure forms in the solidified structure at high cooling rate. Under the gradient temperature field, dendrite arms grow fast towards low temperature direction with developed secondary dendrite arms, and linear solute concentration distribution is formed in dendrite arm due to solute retention. [ABSTRACT FROM AUTHOR]

The high-nitrogen stainless bearing steel 30Cr15Mo1VN, possessing excellent tensile strength (~ 2466 MPa) and impact toughness (~ 130.3 J), was manufactured by pressurized induction melting and pressurized electroslag remelting (PIM + PESR) duplex process. Herein, the inclusion characteristics and element segregation of as-cast ingots, as well as the precipitate characteristics, retained austenite (RA) distribution were systematically investigated to clarify the effect of PESR on tensile and impact properties. Compared with PIM ingot, the lower quantity and larger spacing of inclusions in PIM + PESR ingot were beneficial to improving toughness. Besides, the dendrite segregation originating from solidification inherited to tempered steels and changed the multiphase structure and toughening mechanism. First, the lighter segregation (C, N, Cr, etc.) was induced by the high cooling rate, directional solidification, and short-time homogenization during PESR process, obtaining the higher contents of precipitates and RA in the PIM + PESR ingot. Second, the smaller precipitates and more RA were uniformly distributed in tempered PIM + PESR steel by alleviating segregation, obtaining better interface and matrix plasticity. Third, the dislocation densities of martensite and RA were increased by the greater precipitation pinning effect after PESR, and the uniform area ratios of close-packed and Bain groups were obtained, effectively inhibiting the propagation of secondary crack. Finally, the smaller strength difference between RA and martensite owing to lighter segregation after PESR, alleviated strain localization at phase interfaces and accommodated plastic deformation of matrix, thus, significantly enhancing the strength and toughness of the PIM+PESR steel. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of rare earth (RE) elements on the microstructure and mechanical properties of SAE 52100 bearing steel with bainite/martensite (B/M) structure. For this purpose, SAE 52100 bearing steels with varying RE contents were prepared and analyzed after undergoing B/M heat treatment. The microstructure analysis results suggest that 0.006 wt pct RE elements can significantly facilitate the intragranular transformation of bainite, leading to an increase in bainite volume fraction and a reduction in martensite and retained austenite (RA) volume fraction. The size of M/A blocks decreases accordingly in the RE-treated steels due to the increased partitioning of austenite grains. As the RE content increases, the volume fraction of bainite first increases and then remains nearly unchanged, while the volume fraction of martensite and RA presents the opposite variation tendency, so does the size of M/A blocks. The testing results of mechanical properties indicate that B/M bearing steel exhibits a notable enhancement in impact toughness compared to martensite bearing steel, almost without sacrificing hardness. RE treatment can further improve the impact toughness of B/M bearing steel. This mainly attributes to the role of RE elements in grain boundary strengthening and the refinement of M/A blocks, which inhibits crack initiation at grain boundary and crack propagation contributed by M/A blocks. [ABSTRACT FROM AUTHOR]

To address the need for rapid repair and emergency support of traffic capacity in damaged tunnels, this study proposed a new structure combining arches assembled from steel plates and shotcrete with high early strength and performance (hereinafter referred to as the steel-shotcreting structure) based on the concept of "modular assembly, rapid formation, and temporary-permanent combination". It is designed to replace the traditional cast-in-place concrete arch repair technique. Based on the principle of equivalent stiffness, the load borne by the steel arches in the new support structure was analyzed. Numerical analyses were performed to examine the influences of steel arch spacing and the types of I beams and channel steel on the load-bearing capacity of the new structure under varying surrounding rock and tunnel span conditions. The new steel-shotcreting structure was applied in a tunnel in China and its load-bearing capacity was compared with that of traditional steel arch support structures. The results show that its load-bearing proportions were 13% and 18% under the conditions of grade IV and V surrounding rock, respectively. In large-span tunnels with unstable surrounding rock, reducing the longitudinal spacing of plate steel arches, upgrading the channel steel model for longitudinal connectors, and increasing the size of I beams can enhance the load-bearing performance of the whole structure. Compared to traditional steel arch support structures, the new structure is more adaptable, flexible, and stable and demonstrates better support effects. The research findings provide a theoretical basis and technical support for the rapid repair of damaged tunnels. [ABSTRACT FROM AUTHOR]

AbstractThis study analyzes the initial subsurface crack propagation in bearing steel by utilizing a 3D Voronoi finite element model to simulate the bearing steel’s grain structure. Subsurface stress calculations validate the model. Stress intensity factors were computed to determine crack propagation as a function of initial crack orientation, length, and depth. A novel aspect of this study is the integration of FE analysis with an Artificial Neural Network for predictive modeling. A grid search method was employed for hyperparameter tuning, and ten-fold cross-validation was used to evaluate the ANN’s performance, ensuring robust and accurate predictions. This hybrid approach enables the prediction of SIFs based on various load and crack parameters, facilitating a rapid assessment of crack propagation risk. The results provide valuable insights into the reliability and lifespan of bearing steel, contributing significantly to the field of bearing failure analysis. [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]

Purpose: Machinery operating in a sand-dust environment is more susceptible to sand particles. The purpose of this paper is to investigate the impact of sand particle deposition rate, surface hardness and normal load on the tribological performance. Design/methodology/approach: A predictive model to approximate the number of sand particles within the pin-on-disc contact surface is proposed. The efficacy of the model is validated through experimental method, which replicates a sand environment with two distinct particle deposition rates. Dry sliding friction experiments are also conducted using 45 carbon steel and H90 brass pins against GCr15 bearing steel discs. Findings: When at high particle deposition rate [6.89 × 10–5 g/(s·mm2)], the contact surfaces are separated by particles, resulting in an indirect metal contact. While at low deposition rate [6.08 × 10–8 g/(s·mm2)], there is an alternating occurrence of direct and indirect metal contacts. In sand environment, the specific wear rate of 45 and H90 decreases by 50% and 33%, respectively, compared to non-sand environment when the applied load is 2.45 N. However, it is only 0.18% for 45 but remains significant at 25% for H90 at load of 9.8 N. Originality/value: The predictive model and experimental method used in this paper are helpful for understanding the interaction between particles and sliding surfaces, thereby providing a solid foundation for material selection and load optimization of friction pairs influenced by sand-dust environments. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0155/ [ABSTRACT FROM AUTHOR]

Predicting cutting forces in hard turning optimizes toolpaths, improving machining efficiency and precision, minimizing tool wear, and enhancing manufacturing processes. This study assesses the potential of ensemble machine learning models for predicting machining force components during the hard turning of AISI 52100 bearing steel. Firstly, it conducts a comprehensive evaluation of Random Forest, Gradient Boosting, XGBoost, and CatBoost machine learning models using experimental data collected during AISI 52100 bearing steel turning with a CBN cutting tool. Cubic Spline-based data augmentation is employed to enrich the data, further enhancing prediction quality. A comparative analysis of the considered models on both original and augmented datasets reveals significant performance improvements associated with the utilization of augmented data. Moreover, this study utilizes SHAP (SHapley Additive exPlanations) to elucidate model predictions, providing insights into the contribution of each feature. Results indicate that ensemble learning methods, particularly CatBoost and XGBoost, demonstrate satisfactory predictive results with an averaged R2 of 0.96 and 0.945, respectively. Ensemble models like CatBoost and XGBoost, coupled with data augmentation, prove effective in predicting cutting forces during hard turning, emphasizing the potential for enhanced machining optimization. [ABSTRACT FROM AUTHOR]

In this paper, ultrasonic surface rolling processing (USRP) is used to process GCr15 (AISI-52100), and a three-dimensional ultrasonic surface rolling processing simulation model is established by finite element method to analyze the influence mechanism of static pressure on residual stress. The design L9 orthogonal test studied the importance of USRP parameters on the surface roughness of GCr15 bearing steel. The influence mechanism of process parameters (feed, static pressure, and rotational speed) on the surface microhardness, microstructure, and wear resistance of GCr15 was also studied. The results show that when the process parameters 1400 N, 0.08, and 100 r/min (specimen A7) were selected for machining, the plastic deformation of the specimen was the most intense and the surface grains were refined, forming a grain refinement layer with a thickness of about 10 μm. The surface defects of the specimen are reduced, and the surface roughness is as low as 0.076 μm. The surface microhardness can reach up to 806.2 HV0.5. And the surface roughness, surface hardness, and residual stress increased by 12.56, 65.91, and 138.89%, respectively. After the USRP treatment, the coefficient of friction of the material is reduced, and the amount of wear is reduced by 30%. The wear mechanism also gradually changes from adhesive wear to abrasive wear. [ABSTRACT FROM AUTHOR]

Steel jacking pipes are potentially prone to buckling instability, a phenomenon that has received limited attention in hard rock formations. This study reports on the field monitoring of a water pipeline project in Zhongshan City, where the circumferential and hoop strains of steel pipe segments jacked in hard rocks were recorded. The buckling deformation observed during steel pipe jacking, as well as the critical buckling load, was analyzed with the aid of numerical simulations using finite element software. The initial defect for the post-buckling analysis of the steel pipe was selected as the first-order buckling mode. Field monitoring revealed that the loading conditions experienced by the steel pipe segments during the jacking process are complex, leading to significant deformation. Throughout the monitoring process, axial stress at each measurement point underwent tensile-compressive transitions. Numerical results showed the actual critical buckling load increases with wall thickness at a constant length-to-diameter ratio, which is significant for short pipes. For pipes with the same wall thickness and outer diameter, the actual critical buckling load of long pipes is significantly lower than that of short pipes. Additionally, initial defects were found to significantly reduce the actual critical buckling load of the steel pipe. Furthermore, the actual critical buckling load of long pipes is much lower than their yield load, whereas, for short pipes, the critical buckling load is limited by their yield load. Measures for managing buckling deformation of steel pipes in situ were also reported. The findings on critical buckling load and the countermeasures for managing buckling in situ would be valuable for the design and construction stages of similar projects employing pipe-jacking technology in hard rock formations. [ABSTRACT FROM AUTHOR]

Two ASTM A295 52100 bearing steels with different concentrations of Al (0.02 and 1.90 wt%) were nitrided by three processes: pure nitriding (gas), oxy-nitrocarburizing (gas) and salt bath nitriding. To assess their electrical performance, the area-specific resistance (ASR) of the surface was measured by the four-point probe method. The microstructure of the surface layer was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the ASR of the non-nitrided sample was only approximately 0.005 Ω cm2, but it became larger after all nitriding processes. Among the 0.02 wt% Al-added samples, the greatest ASR was approximately 30 Ω cm2 for the sample nitrided in a salt bath, which can be ascribed to the large amount of oxides (Fe3O4) in the compound layer that exhibits higher electrical resistivity than other nitrides (ε-Fe3N and γ′-Fe4N) observed in the pure or oxy-nitrocarburized samples. Additionally, the addition of Al significantly increased the ASR in the salt bath nitrided sample, which indicated that the Al2O3 formed along the pores in the compound layer played an important role in improving the electrical resistance. [ABSTRACT FROM AUTHOR]

The surface residual stress of the parts has an important influence on their performance. The generation mechanism of surface residual stress in ultrasonic vibration-assisted grinding (UVAG) of bearing steel was investigated, and the correlation between processing parameters and residual stresses was obtained. Based on the ultrasonic vibration-assisted grinding force and thermal model and the flow stress model considering the initial material microstructure, the mechanical and thermal stresses of the material were calculated. Finally, the theoretical model of residual stress is established based on the yield theory and experimentally verified. High-speed ultrasonic aerostatic spindle for ultrasonic vibration-assisted grinding, change the inlet pressure to realize the ultrasonic amplitude and frequency adjustment, the experimental results show that the cutting direction and the vertical cutting direction of the residual stress test results and the model prediction results of the average relative error of 11.4% and 11.7%, and the rule of change is more consistent. Based on the experimental results, the influence pattern of process parameters on the experimental results was analyzed. The results show that the residual compressive stress on the surface of ultrasonic vibration-assisted grinding is directly proportional to the grinding depth, feed rate, and inlet pressure of pneumatic ultrasonic wave and inversely proportional to the linear speed of the grinding wheel. This study provides a theoretical basis for the analysis of UVAG residual stress and optimization of UVAG process parameters. [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]

Circular steel pipe concrete can give full play to the combination of steel pipes and concrete, resulting in an improvement in the steel pipe's concrete bearing capacity and ductility. In this study, the axial compression load capacities of nine steel pipe concrete columns, including one traditional steel pipe concrete column and eight steel pipe self-stressed concrete columns, were analyzed using an axial pressure test. The damage patterns and stress–strain curves of all the specimens under axial compression load were analyzed, and a comparison analysis was made between the test results of the different specimens. The test results show that the longitudinal expansion displacement of concrete increases with the increase in the expansion agent content. The greater the self-stress, the higher the bearing capacity of steel-tube concrete columns under axial compressive load within a certain range of the expansion agent, indicating that self-stress can increase the bearing capacity of steel-tube concrete columns under axial compressive load, but the effect of the magnitude of the self-stress on the damage pattern of the specimens is limited. The damage patterns of all the specimens were bulging in the center and concave at both ends. In addition, the existing theoretical calculation method of the bearing capacity of steel pipe concrete columns is modified, and a theoretical calculation method applicable to steel pipe self-stressed concrete columns is proposed to simplify the calculation method of the bearing capacity of steel pipe self-stressed concrete columns, which provides a basis for decision-making in practical engineering. [ABSTRACT FROM AUTHOR]

The document discusses the importance of heat treatment in modifying the microstructure of metals to achieve desired properties. It highlights research papers on various heat treatment methods and their effects on different alloys, including bearings, martensitic stainless steel, electrical steels, and high resistance steel. The studies focus on optimizing heat treatment parameters to enhance mechanical and magnetic properties, with implications for industrial applications. The document also presents a method for manufacturing low-cost heat pipes with specific properties and geometry using basic tools and 3D printers. [Extracted from the article]

The influence of magnesium treatment on cleanliness and microstructure characteristics of as-cast high-nitrogen stainless bearing steel (HNSBS) was systematically investigated. Results manifested that as the magnesium content increased from 0.0003 to 0.0054 wt pct, the oxygen and sulfur contents in steel, along with the number density and average size of inclusions significantly decreased due to the strong thermodynamic affinity and the removal of inclusions. Meanwhile, the inclusion evolution processes were Al2O3 → MgO·Al2O3 → MgO and MnS → MgS + Mg3N2, and the magnesium content in HNSBS should not exceed 0.0047 wt pct to prevent the formation of deleterious Mg3N2 inclusion. Additionally, the secondary dendrite spacing and the area fraction of precipitates (M23(C, N)6 and M2(C, N)) at the 1/2 radius of ingots decreased form 83 ± 25 μm and 17 pct to 63 ± 16 μm and 12 pct, respectively. The dendrite structure was refined owing to the increase in effective nucleation sites for γ-Fe provided by MgO·Al2O3 and MgS inclusions, as well as the enrichment of magnesium in the liquid phase at solidifying front. The area fraction and size of precipitates were reduced due to the decrease of chromium activity. The finer and more dispersed precipitates was attributed to the reduction of growth space and increase in effective nucleation sites. This work provides theoretical guidance for preventing the formation of deleterious inclusions (especially for nitrides) 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]

Main-shaft bearings are vital safety components in aeroengines made of bearing steels with outstanding combinational properties. The material is supposed to exhibit high surface hardness, high fracture toughness, high temperature resistance, fatigue resistance and corrosion resistance. However, under harsh operation conditions bearing steels are prone to rolling contact fatigue (RCF) that leads to bearing failure, severely endangering flight. Therefore, accurately predicting the RCF lives of bearing steels is key to the reliability of aeroengine. This manuscript reviews important results and progress in the RCF and life prediction of aeroengine bearing steels and suggests future research directions. Firstly, special stress state as a result of the Hertzian contact between rolling element and raceway is introduced, where shear stress components peak at the subsurface. This explains the origin of complex subsurface-originated RCF mechanisms in bearing steels and indicates subsurface-originated RCF to be an important failure mode of bearing steels under ideal conditions. Meanwhile, with increasing contact pressure, the response of material evolves from elastic mode to plastic mode. Besides, due to the harsh service environment of aero-engine bearings, surface-originated also takes place and hence the competition between these two mechanisms is present. Next, three methodologies for RCF life prediction are summarized, being probabilistic models, mechanistic models and numerical models, with their advantages and limitations analyzed. Probabilistic models are well developed and widely employed by industry, but they are in nature a kind of statistical models without accounting for RCF mechanisms and are hence lacking scientificity; Deterministic models predict RCF life via describing physical processes, which are rich in science but poor in accuracy due to their simplification; numerical models balancing both engineering practice and scientific characteristic is a powerful tool to tackle the problem of RCF life prediction, although their accuracy requires further improvement. Finally, it is suggested that future research may focus on solving key scientific problems in RCF, modifying life prediction models via inserting RCF mechanisms and applying artificial intelligence in RCF life prediction. [ABSTRACT FROM AUTHOR]

The corrosion–wear coupling damage failure of 8Cr4Mo4V bearing steel under marine atmospheric conditions significantly limits aeroengine bearing applications. The present work aims to investigate the evolution of the corrosion–wear properties of 8Cr4Mo4V bearing steel at varied corrosion intervals and estimate the corrosion–wear interaction (CWI) effect. Neutral salt spray tests combined with tribological experiments were employed to explore the effect of corrosion on wear and the influence of wear on corrosion, and a quantitative characterization method of corrosion–wear interactions was proposed by establishing the component relationships of material losses in the corrosion–wear process. The results indicate that the corrosion rates initially increase and then decrease, ultimately resulting in a pattern characterized by predominant total corrosion and nested localized corrosion. The corroded surfaces tremendously influence the friction coefficient curves at the third stage, and a synergistic acceleration effect exists in the CWI behavior of 8Cr4Mo4V bearing steel under the action of corrosion and wear. A sample corroded for 6 h displayed the significant facilitative effect of corrosion on wear, exhibiting the highest CWI ratio and a greater total mass loss primarily attributed to corrosion. This study offers a significant reference for the quantitative assessment of the tribo-corrosion properties of bearings in a marine atmospheric environment. [ABSTRACT FROM AUTHOR]

To solve the problems of surface wear and fracture of bearing rings, tantalum carbide (TaC)-reinforced layer was prepared on the surface of GCr15 bearing steel by in-situ hot pressing diffusion method to improve the comprehensive properties of bearing steel surface. As-obtained TaC layer exhibited uniform thickness and dense structure, and the phase composition mainly consisted of TaC and very small amount of α-Fe phase. The interface between reinforcement layer and matrix showed good metallurgical bonding, and no other impurities were generated. Along normal direction of layer base, grain size of TaC in reinforcement layer decreased gradually (200-50 nm), showing gradient distribution. Volume fraction of TaC particles reached 98%, and the maximum microhardness of reinforcement layer reached 2400 HV0.05. Comprehensive analysis of tensile test shows that mainly intergranular fracture of TaC particles occurred inside reinforcement layer, indicating that bonding strength between reinforcement layer and matrix was higher than cohesive strength of reinforcement layer by 320 MPa. In friction and wear experiment, when wear distance of reinforcement layer was 8 times that of steel matrix, wear rate was only 0.33 times (loading 20 N), and wear mechanism was mainly adhesive wear and abrasive wear. Overall, reinforcement layer obtained by in-situ solid-state hot pressing diffusion exhibits good wear resistance and high bonding strength with the matrix and shows good protective effect on the steel matrix. [ABSTRACT FROM AUTHOR]

Over the past 30 years, screw piles with diverse geometries have gained popularity over conventional piles for deep foundations. The behavior of toe-wing screw piles is not widely recognized on a global scale, and the effect of toe-wing plate position on the performance of screw piles has not been explored. Therefore, this paper investigated the impact of toe-wing position on screw pile performance embedded in the bearing layer. The toe-wing plates were embedded (Ew) in the bearing layer at a depth equal to the wing plate diameter, while the embedment depth (Ed) of the central shaft (pile tip) increased from 0 mm to 90 mm, which reflects the change in the toe-wing position. The model ground was prepared in the steel container with bearing layer densities of 55, 80, and 90 %, while the soil above the bearing layer was placed at a relative density of 45 %. The experimental results indicated that the installation load and torque non-linearly increased with the increase in embedment depth ratio (Ed/Ew). However, if checked at the same embedment depth (Ed), the normalized installation load increased to Ed/Ew = 1.2 and then decreased. In contrast, the normalized installation torque is non-linearly reduced with an increased embedment ratio (Ed/Ew). The normalized ultimate pile capacity increased non-linearly with the increase in embedment ratio (Ed/Ew). Regression equations based on the above trends are presented in this study to quantify the effect of Ed/Ew on installation load, torque, and bearing response. [ABSTRACT FROM AUTHOR]

Residual δ-ferrite is ubiquitous in M50NiL bearing steel and seriously deteriorates impact toughness. In the present work, the formation mechanism of δ-ferrite in M50NiL steel and the influence of element segregation on its formation process were investigated. The residual δ-ferrite was proved to form directly from the final liquid phase at the end of solidification due to serious segregation of Mo and V elements. Calculation results indicate that the segregation of Mo and V elements expanded the “L + δ'' two-phase region and stabilized δ-ferrite. Due to the high concentration of Mo and V, large-sized V-rich MC and Mo-rich M2C carbides would precipitate in δ-ferrite at 900–1200 °C if the cooling rate is slow. When kept at 1200 °C for no more than 30 min, Mo and V elements derived from the decomposition of large-sized carbides are preferentially diffused into δ-ferrite, enhancing the stability of δ-ferrite. To achieve the effective elimination of δ-ferrite in M50NiL steel, it is necessary to keep the ingot at 1200 °C for at least 20 h.

The effects of cooling rate on isothermal spheroidizing annealing (SA) of hot-rolled GCr15 bearing steel have been investigated. The results show that controlling the cooling rate between austenitizing and secondary annealing within a specific range is crucial to prevent the formation of lamellar carbide (LC). With a suitable cooling rate, more uniform carbide distribution, lower dislocation density and hardness can be achieved. An increase in the cooling rate results in a decrease in Ar1 and an increase in undercooling. However, an excessively high cooling rate suppresses the divorced eutectoid transformation (DET), leading to an increase in the amount of LC, dislocation density and hardness in rapidly cooled samples. Conversely, in the sample cooled too slowly, the appearance of LC may be attributed to the sufficient precipitation and coarsening of carbides, resulting in a high density of carbides before phase transformation. LCs can be eliminated by extending the secondary annealing time appropriately. This work demonstrates that for isothermal SA, using an appropriate cooling rate can effectively reduce the secondary annealing time, which provides a new idea for the rapid and complete spheroidization of carbides in GCr15 bearing steel.

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]

The reactions of rare earth elements (REEs) with refractory materials significantly affect their effective concentrations and inclusion modifications in molten steel. This study investigated the influence of steel-refractory reactions on the modification of inclusions in lanthanum-, cerium-, and yttrium-added steels utilizing three types of commonly used crucibles as smelting vessels. Steel-refractory reactions were found to strongly affect inclusions with different outcomes for smelting in MgO, Al 2 O 3 , and MgO·Al 2 O 3 crucibles. The RE-crucible reactions affected the evolution and size of inclusions in molten steel by influencing the content of [Mg] and [Al]. The RE-MgO crucible reactions increased [Mg] content, leading to more MgO inclusions and a smaller average size. The RE-Al 2 O 3 crucible reactions increased [Al] content, resulting in more REAlO 3 inclusions and a bigger average size. The reactions of La, Ce, and Y with MgO·Al 2 O 3 crucibles had varying effects on the evolution of inclusions. La and Ce selectively eroded the crucible, mostly reacting with the Al 2 O 3 component and generating REAlO 3 inclusions. In contrast, the slow reaction rate of Y with the crucible and the formation of the dense Y 2 O 3 layer at the steel/crucible interface made it react almost simultaneously with both MgO and Al 2 O 3 components, and the modification of inclusions was dominated by [Mg] rather than [Al]. The above conclusions provided more information on how the reactions between rare earth elements and refractory materials affected inclusions in rare earth steels during smelting. They also enriched the theory of inclusion control in steel and offered new controlling strategies. [ABSTRACT FROM AUTHOR]

M50 bearing steel is a typical alloy material widely used in aeroengines due to its high hardness and fatigue life at high temperatures. To reveal the frictional mechanisms and wear behaviours of contact and sliding, a molecular dynamics simulation model consisting of an indenter and substrate is constructed. The results indicate that, during the indentation process, the normal load exhibits a linear relationship with the indentation depth at shallow depths. With further penetration, the substrate generates severe deformations and subsurface damages. Throughout the scratching process, the average friction force exhibits a linear increase with the growing scratching depth, while the coefficient of friction decreases. Surface morphologies and shear strain distributions are analyzed to elucidate plastic deformation and atomic displacement. Moreover, the wear atom shows a linear proportionality to both scratching distance and depth. These findings enhance understanding of frictional properties and atomic wear behaviour of M50 bearing steel during contact and sliding, potentially informing bearing failure prediction and material optimization. [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]

In this study, premature damage in cylindrical roller bearings made of 100Cr6 (SAE 52100) was investigated. For this purpose, full bearing tests were carried out using two different lubricant formulations with similar viscosities. Published research has pointed out the occurrence of tribo-chemical reactions that cause lubricant degradation and the release of hydrogen in tribo-contact. Hydrogen content measurements were conducted on tested samples, and these measurements showed dependence on the lubricant formulations. Hydrogen diffusion and trapping were identified as significant factors influencing premature damage. The measurement of trapping energies was conducted by thermal desorption spectroscopy, whereas residual stresses, which influence hydrogen diffusion and accumulation, were measured using X-ray diffraction. The measured trapping energies indicated that rolling contact caused the creation and release of hydrogen traps. Over-rolling resulted in changes in residual stress profiles in the materials, demonstrated by changes in stress gradients. These can be directly linked to subsurface hydrogen accumulation. Hence, it was possible to determine that the location of the microstructural damage (WEC) was correlated with the residual stress profiles and the subsurface von Mises stress peaks. [ABSTRACT FROM AUTHOR]

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Rare earth can effectively improve the morphology of inclusions in steel. This paper investigates the modification effects and mechanisms of La-Ce composite rare earth on the inclusions in GCr15 bearing steel by adding different contents of La-Ce. The research shows that the typical inclusions in GCr15 bearing steel were Al2O3 and MnS. The addition of La-Ce enhanced the cleanliness of the molten steel and caused a morphological transformation of the inclusions. With La-Ce content less than 96 ppm, as the La-Ce content increased, the inclusion types in GCr15 bearing steel transition from Al2O3 + MnS → REAlO3 + RExSy → RE2O2S + RExSy. (RE were La and Ce). Due to the higher interfacial energy between the rare earth inclusions and the matrix, their morphology tended to be more spherical. When the La-Ce content exceeded 96 ppm, it led to the formation of RE2O3 inclusions in the steel. Although the morphology of individual RE2O3 inclusions also tended towards spherical, the overall morphology became irregular due to the aggregation and growth of the inclusions. [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]

Bearing steel (GCr15) is widely used in key parts of mechanical transmission for its excellent mechanical properties. Electrochemical machining (ECM) is a potential method for machining GCr15, as the machining process is the electrochemical dissolution of GCr15 regardless of its high hardness (>50 HRC). In ECM, NaNO3 solution is a popular electrolyte, as it has the ability to help in the nonlinear dissolution of many metallic alloy materials, making it useful for precision machining. However, due to high carbon content of GCr15, the electrochemical dissolution of GCr15 is unique, and there is always a black layer with high roughness on the machined surface, reducing the surface quality. In order to improve the electrochemical machining of GCr15 with a high surface quality, the surface characteristics of GCr15 in ECM were investigated. The anodic polarisation curve in the NaNO3 electrolyte was measured and electrochemical dissolution experiments were conducted with different current densities. SEM, XRD, and XPS were employed to analyse the surface morphology and composition formed on the machined surface at different current densities. The initial results showed that there were two parts (black part and bright part) formed on the machined surface when a short circuit occurred, and the test results suggested that the black part contained a mass of Fe3O4 while the bright part was composed of mainly Fe and Fe3C. Further investigation uncovered that a black flocculent layer (Fe3O4) always formed in a low current density (32 A/cm2) with high roughness. With the current density increased, the amount of black flocculent layer was reduced, and Fe3C particles appeared on the machined surface. When the current density reached 81 A/cm2, the entire flocculent oxide layer was removed, only some spherical Fe3C particles were inserted on the machined surface, and the roughness was reduced from Ra7.743 μm to Ra1.783 μm. In addition, due to exposed Fe3C particles on the machined surface, the corrosion resistance of the machined surface was significantly improved. Finally, circular arc grooves of high quality were well manufactured with current density of 81 A/cm2 in NaNO3 electrolyte. [ABSTRACT FROM AUTHOR]

By means of microstructure observation and mechanical property tests, the influence of the laser pulse energy of the laser shock processing (LSP) on the surface residual stress, microstructure, microhardness and fatigue limits of the M50 steel was studied. Results show that when the laser pulse energy increases from 4, 6 to 8 J, the surface damage of the sample becomes more and more pronounced, which gradually changes from pits to long-strip ravines. LSP increases the hardness of the steel, the maximum hardness occurs on the impact surface, and the microhardness gradually decreases as the distance from the impact surface increases. When the laser pulse energy rises from 4 to 8 J, the maximum hardness of the surface increases from 741 to 845 HV1, which are 2.90 and 11.33% higher than the steel matrix respectively. The depth of the hardened layer of the samples produced by LSP is also deepened when the laser pulse energy increases. The hardened layer depth is approximately 0.3 mm when the laser pulse energy is 4 and 6 J, which reaches 0.5 mm when the laser pulse energy is 8 J. LSP generates residual compressive stresses of − 423, − 565 and − 809 MPa on the surface of the samples when the laser pulse energy are 4, 6 and 8 J respectively. The residual compressive stresses can inhibit the expansion of cracks, so that the steel is less prone to fracture, and thereby the fatigue limit of the steel is increased by 45.95% from 740 MPa of the sample without LSP to 1080 MPa after LSP with the laser pulse energy of 8 J. [ABSTRACT FROM AUTHOR]

Accurately predicting cutting forces in hard turning processes can lead to improved process control, reduced tool wear, and enhanced productivity. This study aims to predict machining force components during the hard turning of AISI 52100 bearing steel using machine learning models. Specifically, eight models were considered, and their prediction performance was assessed using experimental data collected during AISI 52100 bearing steel turning with a CBN cutting tool. The fivefold cross-validation technique has been adopted in training to obtain more reliable estimates of the performance of a model and reduce the risk of overfitting the data. Results showed that the Gaussian process regression (GPR) and decision tree regression outperformed the other models, with averaged root-mean-square error values of 14.44 and 12.72, respectively. GPR also provided prediction uncertainty. Additionally, feature selection was performed using two algorithms, namely Regressional Relief-F and F test, to identify the most important features impacting the cutting forces. The findings of this study can be useful in optimizing cutting parameters for hard turning processes to select cutting forces, reduce tool wear, and minimize the generated heat during the machining process. [ABSTRACT FROM AUTHOR]

The study aims to investigate the effects of carburizing (C), carburizing and nitriding (C+N) sequential treatment on microstructure, microhardness distribution, residual stress distribution and rolling contact fatigue (RCF) properties of M50NiL bearing steel. The results showed that the fatigue limit of the C+N samples was 14.4% higher than that of the C samples. According to analyses of fatigue crack initiation and propagation behavior of RCF specimens revealed that the failure mechanism of the C specimens was deep spalling caused by fatigue crack in a large-angle propagation mode; whereas the C+N specimens had higher surface hardness and residual compressive stresses, which suppressed fatigue crack initiation and propagation, and the failure mechanism was changed to fatigue crack in a small-angle propagation mode caused by shallow spalling. Transmission electron microscopy analysis of C+N specimens after RCF experiments revealed that the dislocations proliferate and shear the carbonitride precipitation phases during the RCF experiments, and the microstructure and precipitation phases of the M50NiL steel are refined, which effectively inhibited the rate of fatigue crack initiation and propagation, and substantially enhanced the RCF life of M50NiL steel. [ABSTRACT FROM AUTHOR]

Samples of AISI 52100 bearing steel were treated by using laminar plasma quenching methods with three optimized process parameters: input power, scanning speed, and scanning distance. The influence of process parameters on the surface morphology and quenching depth of AISI 52100 bearing steels was explored, as well as the influence on their microstructure and microhardness. Furthermore, the surface wear resistance was tested by using a reciprocating wear testing machine. The results showed that samples with a lower surface roughness and a deeper hardened layer could be obtained by treating with the combination of input power 10.6 kW, scanning speed 500 mm/min and distance 20 mm. Microstructure analysis indicated that finer acicular martensite formed at the surface layer. The microhardness analysis shows that the hardness was improved by 20%, and the wear volume was reduced by 37.7%. The treated AISI 52100 bearing steel sample only had some furrow-like abrasive wear, while the untreated sample had more spalling pits in addition to furrow-like wear. The excellent anti-wear performance could be attributed to the hardness of cryptocrystalline martensite, which formed a hardened layer on the surface of the material. Therefore, the plasma quenched AISI 52100 bearing steel exhibited excellent wear resistance, which could effectively improve the service life of the bearing steel and has broad prospects in the field of surface modification. [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]

Grease lubrication is cost-effective and low-maintenance for motorized spindles, but standard steel bearings can fail at high speeds. This study focuses on high-speed full ceramic ball bearings lubricated with grease. The coefficient of friction torque in the empirical formula is corrected by establishing the heat generation model of full ceramic ball bearing and combining it with experiments. A simulation model of grease flow is established to study the influence of grease filling amount on grease distribution. The simulation model of the temperature field of a full ceramic ball bearing is established to analyze the influence of rotating speed on bearing heat generation, and experiments verify the calculation results of the theoretical model. The results show that an optimal grease filling amount of 15~25% ensures even distribution without accumulation. Additionally, when the amount of grease is constant, the outer ring temperature increases with higher rotating speeds. The test results show that when the grease filling is 0.9~1.2 g, it accounts for about 9~12% of the volume of the bearing cavity, and the temperature of the outer ring is the lowest. At a rotation speed of 24,000 rpm, the outer ring temperature of the grease-lubricated bearing is 50.1 °C, indicating a reasonable range for use in motorized spindles. It provides a theoretical basis for the optimization design of macro-structural parameters of full ceramic ball bearings in the future, which can minimize heat generation and maximize bearing capacity. [ABSTRACT FROM AUTHOR]

Surface properties of bearing steel and other small automotive parts are generally modified in an effort to enhance its hardness and wear characteristics. In the current study, tantalum and graphite powders are added to surface of steel during tungsten inert gas (TIG) arcing to create in situ tantalum carbide to improve reinforcement to the modified surface in addition to the hard martensite matrix. Numerical simulation using COMSOL software was performed to estimate the thermal profile and validated by the experimental observation. The microstructural characteristics of the matrix were examined using optical, scanning and transmission electron microscope (OM, SEM and TEM). High resolution transmission electron microscope (HRTEM) along with electron energy loss spectrum (EELS) mode was employed to understand the type of carbide particles formed. It was found that the top modified surface contains TaC particles which enhances the hardness. The extent upto which different zones like fusion and heat affected zone, base metal, etc formed after the arcing was established both by microscopic examination and micro-hardness mapping. Modified surfaces show a notable increase in hardness from 100 to 150 percent relative to the base material. The weight loss during wear testing for different modified surfaces was significantly reduced by two to four times when compared to the substrate, indicating the presence of an effective wear resistance mechanism in the modified surfaces. [ABSTRACT FROM AUTHOR]

The fatigue behaviors of high-strength bearing steel were investigated with rotating bending fatigue loading with a frequency of 52.5 Hz. It was revealed that the high-strength steel tended to initiate at interior non-metallic inclusions in a very high-cycle fatigue regime. During fractography observation, it was also seen that the inclusion acting as a failure-originating site was seldom smaller than 10 μm. Moreover, prior austenite grains could also act as the originating source of failure when inclusion was absent. The crystal plasticity finite element method (CPFEM) was adopted to simulate the residual stress distribution around non-metallic inclusions of different sizes under different loading amplitudes. The accumulated plastic strain around the inclusion suggested that the existence of inclusion may reduce material strength and lead to more fatigue damage. The value of accumulated plastic strain around different inclusion sizes also resembled the crack nucleation or propagation of the materials. The simulation results also indicated that inclusions smaller than 5 μm had little influence on fatigue lifetimes, while inclusions larger than 10 μm had a significant influence on fatigue lifetimes. [ABSTRACT FROM AUTHOR]

Inclusions are an important parameter affecting the fatigue life of materials. In this paper, the type, size, and quantity of inclusions in bearing steel were quantitatively analyzed using scanning electron microscopy and automatic scanning electron microscopy with an X-ray energy dispersive spectroscopy function. The effects of the inclusion parameters and positions on the rotating bending fatigue properties were analyzed using the rotating bending fatigue test. The results proved that for samples 1 and 2, the inclusions were mainly sulfides, Ti-containing inclusions, and their composite inclusions. For samples 3 and 4, the inclusions were mainly oxides or sulfide–oxide complexes. The number and maximum size of inclusions in sample 2 were relatively small. This was mainly due to the difference in the content of Al, S, and Ca elements in the different samples. The inclusion distance to the surface and the maximum inclusion size had a larger influence on the rotating bending fatigue life in comparison to the inclusion type. Moreover, nitride–oxides had a more detrimental effect on the rotating bending fatigue life as compared to the sulfide–oxide complex inclusions. A model was established on the basis of the inclusion size, depth, and stress by using the Python software. The simulation demonstrated that using five parameters fit well with the experiment results. [ABSTRACT FROM AUTHOR]

The impact of rare earth treatment on the chemical morphology evolution of non-metallic inclusions in bearing steel under different initial cleanliness conditions was studied through simulation. Thermodynamic calculations indicate that at an oxygen content of 0.001%, the evolution route of inclusions with increasing Ce content was Al2O3 → CeAl11O18 + CeAlO3 → CeAlO3 + Ce2O2S → Ce2O2S → Ce2O2S + CeS. As the initial oxygen content decreases, the proportion of CeAlO3 decreases, leading to easier conversion of CeAlO3 to Ce2O2S. Vacuum induction furnace experiments demonstrated that with an oxygen content of 0.001%, an increase in Ce content results in a gradual rise in the proportion of inclusions in steel sized 1~2 μm. In contrast, the proportion of inclusions sized 2~5 μm decreases. Consequently, the overall content of inclusions in steel decreases, along with a reduction in both the number density and average size of inclusions. Introducing bearing steel melt with approximately 0.01% Ce rare earth to bearing steel with initial oxygen contents of 0.0005%, 0.001%, and 0.0015% showed an evolution of inclusions from Ce2O2S and CeS to Ce2O3, CeAlO3, etc. The average inclusion size significantly increased from 0.7 μm to 2.16 μm. Morphologically, the transition of inclusions from precipitated to polymerized forms occurred as the initial oxygen content rose. High-temperature laser confocal microscopy experiments demonstrated that inclusions in low cleanliness conditions tend to agglomerate more than those in high cleanliness conditions, contributing to the increase in average size. [ABSTRACT FROM AUTHOR]

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the damage process and failure mode of these hybrid RC columns was similar to those in the conventional steel-reinforced concrete columns. The mode of failure for all specimens is characterized as large eccentricity compression failure, and the ultimate bearing capacity of the columns decreases with the increase in eccentricity. However, the impact of the varying axial stiffness ratio between GFRP and steel bars on the bearing capacity can be considered negligible. In addition, based on theoretical analysis, two boundary states for distinguishing failure mode and the formulae for calculating ultimate bearing capacity in different failure modes of eccentrically loaded hybrid RC columns are proposed. The computed results agree well with test results. [ABSTRACT FROM AUTHOR]

The flange joint is an important connection in steel tube structures. In this paper, 11 groups of flange joint tests were conducted to investigate the influences of tube diameter, flange plate thickness, the distance from the bolt to the tube centroid, bolt numbers and material strength on the mechanical behavior. One of two failure modes in tests is that the excessive plastic deformation on the flange plate makes the flange plate lose the bearing capacity; the other is that the steel tube yield makes the joints fail. The results show that the calculating method for flange joint in Chinese design code is so safe that amplifying the calculating results of the code by 1.2 times would be closer to the bearing capacity of specimens. For a flange joint with different tube diameters, thickening the flange plate of thinner tube or thinning the flange plate of another tube are effective to ensure the deformations on both sides of the flange plates are equivalent. The ratio of the bearing capacity of the steel tube to that of flange plate should be greater than 1.7. And the thickness of the flange plate should be thicker than 14mm to reduce the deformation caused by cutting, drilling and welding during manufacturing. [ABSTRACT FROM AUTHOR]

Due to the strong reducibility and chemical activity of rare earths, the diffusion behavior and secondary oxidation of rare earths in the steel liquid will also have a significant impact on the modified products when rare earths are added to bearing steel, resulting in poor control of distribution behavior. Therefore, this paper studies the influence of time factors on the evolution of rare earth inclusions. The inclusion evolution behavior at different times when the bearing steel was treated with rare earths and subjected to secondary oxidation was simulated at 1873 K (1600 °C). At a cerium content of 0.012% in steel and a secondary oxidation of 0.0025%, the cerium content in steel and the total oxygen (T.O.) content in steel were determined at the 30 s, 3 min, 5 min, and 7 min after the addition and the inclusions were characterized by automatic scanning electron microscopy. The results demonstrated the formation of a cerium-enriched zone after the addition of the cerium alloy to the steel. As time progressed, a considerable number of inclusions were generated in the cerium-enriched zone, which subsequently disappeared. The trend in the composition of the inclusions can be described as Al2O3 → Ce2O2S + CeS → Ce2O2S. The final composition of the inclusions matches the thermodynamic phase diagram. Following the addition of the transient oxidant Fe2O3 to the molten steel, an oxygen-enriched zone was formed. As time progressed, a considerable number of inclusions were generated in the oxygen-enriched zone and subsequently disappeared. The trend of inclusions composition was as follows: Ce2O3 + CeAlO3 + Al2O3 → Ce2O3 + CeAlO3 → Ce2O2S + CeAlO3. The final inclusion composition coincides with the thermodynamic phase diagram. [ABSTRACT FROM AUTHOR]