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Defect detection is crucial in ensuring the quality of steel products. This paper proposes a novel deep neural network, cascaded adaptive global location network (CAGLNet), for detecting steel surface defects. The main objective of this study is to address the challenges associated with the irregular shape and dense spatial distribution of defects on steel. To achieve this goal, CAGLNet integrates a feature extraction network that combines residual and feature pyramid networks, a cascade adaptive tree-structure region proposal network (CAT-RPN) that eliminates the need for prior knowledge, and a global localisation regression for steel defect detection. This paper evaluates the effectiveness of CAGLNet on the NEU-DET dataset and demonstrates that the proposed model achieves an average accuracy of 85.40% with a fast frames per second of 10.06, outperforming those state-of-the-art methods. These results suggest that CAGLNet has the potential to significantly improve the effectiveness of defect detection in industrial production processes, leading to increased production yield and cost savings. Abbreviations: AT-RPN, adaptive tree-structure region proposal network; CAGLNet, cascaded adaptive global location network; CAT-RPN, cascade adaptive tree-structure region proposal network; CNN, convolutional neural network; DNN, deep neural network; EPNet, edge proposal network; FPN, feature pyramid network; FCOS, fully convolutional one-stage detector; FPS, frames per second; GMM, Gaussian mixture model; IoU, intersection-over-union; ROIAlign, region of interest align; RPN, region proposal network; ResNet, residual network; ResNet50_FPN, residual network and feature pyramid network; SABL, side aware boundary localisation; SSD, single-shot multiBox detector; TPE, Tree-structured Parzen estimator [ABSTRACT FROM AUTHOR]

We present here experimental verification of a theoretical model previously developed to estimate internal mechanical stress in steel-based elements by means of non-contact electromagnetic induction measurements. Results confirm the validity of the proposed model and demonstrate that stress below 50% of the elastic limit can be detected with standard electronics. [ABSTRACT FROM AUTHOR]

The article, titled "The Role of Migration in Classes of Labour: Work and Life in a Central Indian Steel Town," provides an ethnographic study of the industrial workers in the central Indian steel town of Bhilai. The author explores various topics such as labor recruitment, reservations, promotions, and unions, as well as the relationship between caste and class. The article highlights the significant role of labor migration in shaping and reproducing capitalism in Bhilai, emphasizing how migration created the city and transformed rural sending regions. It also discusses how migration contributes to the formation and consolidation of class divisions among workers, as well as the impact of migration on class-based superiority and non-class identities. The article concludes by raising questions about the potential for migration to challenge capitalism and foster working-class solidarity in the future. [Extracted from the article]

Variations in the microstructure and the dominant fretting wear mechanisms of carbon steel alloy in oscillatory sliding contact against stainless steel in a dry atmosphere were evaluated by various mechanical testing and microanalytical methods. These included scanning electron microscopy and energy dispersive spectrometry with corresponding elemental maps of the wear tracks, in conjunction with cross-sectional transmission electron microscopy of samples prepared by focused ion beam machining to assess subsurface and through-thickness changes in microstructure, all as a function of applied load and sliding time. Heavily dislocated layered microstructures were observed below the wear tracks to vary with both the load and sliding time. During the accumulation of fretting cycles, the subsurface microstructure evolved into stable dislocation cells with cell walls aligned parallel to the surface and the sliding direction. The thickness of the damaged subsurface region increased with the load, consistent with the depth distribution of the maximum shear stress. The primary surface oxide evolved as Fe2O3 and Fe3O4 with increasing sliding time, leading to the formation of a uniform oxide scale at the sliding surface. It is possible that the development of the dislocation cell structure in the subsurface also enhanced oxidation by pipe diffusion along dislocation cores. The results of this study reveal complex phase changes affecting the wear resistance of steels undergoing fretting wear, which involve a synergy between oxidative wear, crack initiation, and crack growth along dislocation cell walls due to the high strains accumulating under high loads and/or prolonged surface sliding.

This work follows on from studies carried out by Jiles and Atherton on magnetic hysteresis and on the magnetomechanical effect. The Jiles–Atherton equation, which models the rate of change of magnetization with respect to stress, was solved numerically in the forward and reverse directions for stress up to 90 MPa, suggesting that stressing carbon steel will cause a lasting change in the magnetization of the sample. This was confirmed experimentally by measuring the B-field in proximity to samples of C45 steel while undergoing tensile stress, with the pattern of magnetization suggesting that the magnetic domains reorient themselves in the geomagnetic field when stressing loosens their pinning. A further experiment on two samples confirms this, with the B-field around the samples showing strong changes according to their orientation in the geomagnetic field at the time of the stressing. This work has relevance to the non-destructive testing of steel structures such as pipelines, and the relevance of the experiments to this work is considered, as well as future prospects. [ABSTRACT FROM AUTHOR]

This work formulates and investigates a steel grade design problem (SGDP) arising from a production process of steelmaking continuous casting. For the first time, we consider uncertain yield and demand in SGDP and construct a two-stage robust optimisation model accordingly. Then, we propose an enhanced column-and-constraint generation algorithm to obtain high-quality solutions. By exploiting the problem characteristics, we first use a Lagrangian relaxation method to decompose SGDP into multiple subproblems and then apply a standard column-and-constraint generation algorithm to solve the latter. At last, we test the proposed algorithm by extensive instances constructed based on actual production rules of a steelmaking shop. Numerical results show that it can effectively solve large-scale SGDPs. The obtained plan is better than those obtained by a commonly-used and standard column-and-constraint generation algorithm. [ABSTRACT FROM AUTHOR]

The microstructure and hydrogen embrittlement sensitivity of two X65 pipeline steels at different t 8/5 (the time required to cool from 800 °C to 500 °C) were investigated employing thermal simulation. With the increase of t 8/5 for both steels, the martensite transferred to acicular ferrite (AF) and bainite, and further converts to bainite and martensite/austenite (M/A) constituents. Elongated polygonal Mn–Nb–S inclusions appear in steel A, which are easy to fall off and the hydrogen embrittlement sensitivity is thus increased. However, spherical Al–Ca–Nb–N–O–S inclusions appear in steel B, which can promote nucleation of AF, thus obtaining lower hydrogen embrittlement sensitivity under lower t 8/5. • The HE sensitivity of two X65 pipeline steels at different t 8/5 were investigated. • The elimination of M and the nucleation of AF can reduce HE sensitivity. • Elongated polygonal Mn–Nb–S inclusions easily shed and increase HE sensitivity. • Spherical Al–Ca–Nb–O–S inclusions promote AF nucleation and reduce HE sensitivity. [ABSTRACT FROM AUTHOR]

Common alloying elements such as Mn and Al can significantly influence the local dynamics of Hydrogen in steel, promoting or attenuating the mechanisms associated with Hydrogen induced Embrittlement (HIE). Here, we propose a first principles-based framework to systematically unlock the physical underpinnings of such influence in Mn/Al-alloyed γ-Fe. Our framework can be readily adapted to analyse H behaviour in the bulk phase of any face-centred cubic (FCC) Fe-X-Y alloy, provided that solutes X and Y substitute the Fe sites. In our scheme, all thermodynamically stable substitutional solute sites were identified (≤5.4 wt% Mn; ≤4 wt% Al) up to the third nearest neighbour (NN) shell of a single H atom. The impact of Mn/Al on H-binding was quantitatively evaluated, indicating a surprisingly strong correlation with the local Al distribution regardless Mn content, and indirect stabilization by Al when present in the 2nd NN shell. Nonetheless, Al strongly repels H bonding. The contradictory role of Al was explained in terms of bonding/anti-bonding orbitals occupancy in H-M interactions (M = Al, Mn, Fe). The barriers to H hopping between adjacent local environments and the corresponding jump frequencies were subsequently calculated, providing insights into the limits imposed by the presence of Al and Mn on H mobility in Mn/Al-alloyed γ-Fe. Most notably, presence of Al in the 2nd NN shell of H severely reduces the H jump frequency, leading to potential irreversible trapping at high Al contents. Such behaviour may critically contribute to mitigate H-induced delayed fracture in Al-rich austenite steel. [Display omitted] • H-binding strength is strongly correlated with local distribution of Al, regardless Mn content. • Al repels H but indirectly strengthen the H-binding when present in the 2nd NN shell. • The unique dual role of Al on H-binding is explained via COHP analysis. • Reversible and irreversible trapping sites are isolated for Fe-Mn-Al alloys. • Irreversible H-trapping may contribute to mitigate H-induced delayed fracture. [ABSTRACT FROM AUTHOR]

• The mechanism of carbonation of steel slag was explored. • Process simultaneously carbon sequestration, CO 2 capture and waste heat recovery. • Directly use the lime kiln gas as the gas source without purification. • Average treatment cost of 0.68 MWh for 1 t of steel slag for the process. The iron and steel-making industries have garnered significant attention in research related to low-carbon transitions and the reuse of steel slag. This industry is known for its high carbon emissions and the substantial amount of steel slag it generates. To address these challenges, a waste heat recovery process route has been developed for molten steel slag, which integrates CO 2 capture and fixation as well as efficient utilization of steel slag. This process involves the use of lime kiln flue gas from the steel plant as the gas quenching agent, thereby mitigating carbon emissions and facilitating carbonation conversion of steel slag while simultaneously recovering waste heat. The established carbonation model of steel slag reveals that the insufficient diffusion of CO 2 gas molecules within the product layer is the underlying mechanism hindering the carbonation performance of steel slag. This finding forms the basis for enhancing the carbonation performance of steel slag. The results of Aspen Plus simulation indicate that 1 t of steel slag (with a carbonation conversion rate of 15.169 %) can fix 55.19 kg of CO 2 , process 6.08 kmol of flue gas (with a carbon capture rate of 92.733 %), and recover 2.04 GJ of heat, 0.43 GJ of exergy, and 0.68 MWh of operating cost. These findings contribute to the development of sustainable and efficient solutions for steel slag management, with potential applications in the steel production industry and other relevant fields. [ABSTRACT FROM AUTHOR]

Accumulative roll bonding (ARB) is a repeated cladding process in which two or more sheets of material are joined together by rolling at temperatures below recrystallization. The present review is focused on ARB of high‐alloy steels, which, among other laminated metal composites (LMCs), deliver the highest mechanical properties. After a brief description of high‐strength steels, history, and state of the art of LMCs, the principal roll bonding mechanism is explained. Further, the methodology of ARB of steels and variable parameters (stacking, temperature, etc.) are discussed. Known examples of steel–steel laminates are summarized with respect to their rolling temperature and mechanical properties. Further, the main toughening mechanisms of steel‐based LMCs are listed. The most promising candidates of high‐alloy steel laminates are presented in more detail. The important deformation mechanisms of twinning‐ and transformation‐induced plasticity (TWIP and TRIP) high‐alloy steels are explained. Microstructural changes and layer bonding as well as mechanical properties and damage behavior of two‐ and four‐layered TRIP/TWIP steel laminates are illustrated, including some specific phenomena, such as deformation lenses. Finally, by summarizing the analyzed data on steel laminates, conclusions and outlook are formulated. [ABSTRACT FROM AUTHOR]

To address the issue of low detection accuracy of steel surface defects due to complex texture background interference and complex defect morphology, this paper proposes an improved YOLOv8 model based on MobileViTv2 and Cross-Local Connection for steel surface defect detection. Firstly, the lightweight MobileViTv2 network is introduced into the backbone network, which enhances the feature extraction capability of the model in complex defect shapes by combining the advantages of CNN and Transformer. Then, the designed CLC method is introduced into the neck network, which connects deep and shallow features through additional convolutional layers, further integrating defect features in the presence of complex texture background interference. Finally, the NET-DET dataset is augmented to improve the model's robustness. Experimental results show that the mAP of the improved model is 74.1%, with a detection speed of 86.2 FPS and model memory usage of 27.5 MB. Compared to YOLOv5 and YOLOv8, the mAP of the improved model is increased by 6.5% and 4%, respectively. Compared to existing object detection models, the improved model has the characteristics of high detection accuracy and fast detection speed, meeting the requirements of industrial production for steel surface defect detection. [ABSTRACT FROM AUTHOR]

Virtual trial assembly (VTA) using 3D laser scanning as the digital carrier can overcome the shortcomings of time‐consuming and costly physical preassembly. However, its application in large steel structures with bolted connections remains limited. First, this study introduces a novel approach for acquiring multiscale point cloud data of large steel members using terrestrial laser scanners (TLSs) and hand‐held scanner (HHS). This approach considers both the global data and the local details of the steel members. Additionally, a precise registration method based on magnetic 3D targets is proposed for multiscale point clouds, which enables the registration accuracy of multisource point clouds to reach submillimeter precision. Subsequently, a novel algorithm for feature point screening is introduced, which utilizes a dichotomous point cloud grid approach to identify and extract a significant quantity of bolt holes effectively. This approach enables fully automated and fast extraction of the point cloud on the cylindrical inner surface of the holes. Finally, the bounding box and Procrustes analysis approach are employed to perform VTA using the point cloud of the cylindrical bolt holes as the assembled features. The accuracy and feasibility of the above method are verified by a down‐scale modeling experiment and project test, which provide technical support for the VTA of large steel truss structures. [ABSTRACT FROM AUTHOR]

This paper discusses web slenderness effects on the flexural behaviour of epoxy adhesive-bonded compound normal and high-strength steel beams. The compound beams were simply supported and consisted of an I-section connected, on its top flange, to a channel section using an epoxy adhesive. A non-linear three-dimensional finite-element modelling study was performed using Abaqus software for the analysis of the beams. The non-linear finite-element modelling was verified against tests on compound steel beams with different cross-sections. An extensive parametric study was carried out using the finite-element modelling to study the effects of the change in web slenderness, cross-sectional geometries, beam lengths and steel strengths on the flexural behaviour of compound steel beams. The failure moments predicted by the finite-element modelling were compared with the design moments predicted by the European code for steel beams in flexure. It is shown that the code generally overestimated the design failure moments for most of the epoxy adhesive-bonded compound steel beams investigated in this study. In addition, reliability analysis was performed to assess the reliability of the design rules of the code. Generally, it was found that the European code is unconservative and statistically unreliable for the epoxy adhesive-bonded compound beams investigated in this study. [ABSTRACT FROM AUTHOR]

To examine the frictional action of stacked disk springs with low initial cone angle, axial compression tests were conducted by varying sizes and stacked forms of springs. Each stacked form exhibited stable and predictable behavior and the increase of parallel springs improves frictional dissipation. Lubricating greases can reduce but not eliminate the frictional action. The finite element analysis (FEA) employing friction coefficients from 0.2 to 0.3 can match test results on the whole. Verifications show that some existing predictions, except for the prediction from the standard, can well reflect the frictional action between the end plates and disk springs. Besides, convenient formulas to correctly reflect the frictional action between parallel springs are still needed due to existing theoretical models with either low precision or implicit and complicate calculation of relative sliding deformations between parallel springs. Therefore, based on a method employing either the moment balance or the energy balance, theoretical models and convenient formulas to predict the frictional action for the stacked springs in parallel were proposed. Furthermore, a formula to comprehensively consider the frictional action for springs stacked in both parallel and series was given. The effectiveness of the proposed formulas was verified by comparing with both the FEA and the test results. In addition, possible contacts between springs and the control bar would induce additional frictional actions, which can be compensated in some degree by appropriately adjusting the friction coefficients. Equivalent coefficients that can be employed in the formula of the standard to improve precision were provided. [ABSTRACT FROM AUTHOR]

Steel structures are invariably analyzed and designed excluding the global stiffening effect of the roof cladding. Including this effect historically required complex design methods or deprecated standards. This paper presents a simplified numerical modeling method which allows this stiffening effect to be included. The method is an extension of the already established Component Method but utilizes only elements commonly available in typical design and analysis software. The results of the models were favorably compared to standardized test cases; an average difference of 0.24 mm maximum displacement was found, corresponding to a 3.4% discrepancy. The consistency of these results implies that the proposed model can be considered to be used for scientific and practical purposes when assessing a building's most realistic behavior is necessary. [ABSTRACT FROM AUTHOR]

For the post-fire safety evaluation of metal structures or parts thereof, we still rely too often on experiential and non-scientific methods, as there exists today no transparent approach allowing to perform this using reliability-based approaches. Nevertheless, hundreds of tests have been carried out in the past on carbon and stainless steels samples that have been subjected to a heating and subsequent cooling procedure. Unfortunately, up to now, these data were not processed in a statistical way and there exists no elaborate method allowing designers to assess structural safety after a fire has occurred in an existing structure. In this research, we have solved this issue by analysing the variation in material properties of metals over time, as a function of the maximum reached temperature, and by proposing a modified reliability factor adapted to the study of existing buildings. The method is explained in detail and provided with the necessary practical information so that it is straightforwardly usable by all those involved in a post-fire evaluation. In the end, a practical example is used to illustrate the differences between carbon and stainless steels, the post-fire behaviour of which were analysed. [ABSTRACT FROM AUTHOR]

Hybrid fire testing is a testing method for structures on fire based on a substructuring method. A complete structure is divided in two substructures, one in a fire test laboratory (physical substructure), and one numerically simulated (numerical substructure). In fire engineering, some hybrid fire tests have been successfully performed in the last decades, but as the method is still in its infancy, these hybrid tests were limited to one-degree-of-freedom tests. The paper presents the first successful multi-degree-of-freedom hybrid test performed in fire engineering. The physical substructure is a steel column with an axial displacement and rotations at the ends controlled by electric jacks. The numerical substructure is a non-linear 2D plane frame structure modelled in SAFIR®. The equations of the algorithm, the experimental setup, the testing process, and the results are presented. [ABSTRACT FROM AUTHOR]

Off-site steel construction (OSC) is an emerging alternative to traditional on-site methods that offers advantages such as reduced waste, improved quality, and faster delivery. However, OSC also requires robust monitoring and control mechanisms within fabrication shops to ensure the timely and cost-effective completion of projects. This study presents the development and application of a machine learning (ML) model to estimate the cost performance index (CPI), a pivotal indicator of project progress and performance, by considering influential factors that affect OSC projects. A comprehensive analysis of data from 56 OSC projects fabricated in a steel parts manufacturing facility between 2020 and 2022 was conducted. The investigation focused on four key features: project weight, project utilization type, project connection type, and material supply method, examining their impact on CPI. The data set was meticulously preprocessed, and three ML algorithms—support vector machine (SVM), gradient boosting (GB), and decision tree (DT)—were employed to model CPI. Model performance was evaluated and compared using metrics including root mean square error, accuracy, and R-squared. The findings demonstrated that GB excelled in CPI prediction, achieving an accuracy rate of 91%. This research underscores the utility of ML as a valuable tool for monitoring and controlling off-site steel construction projects. It also provides insights into the factors that influence CPI and suggests ways to optimize them for better project outcomes. Furthermore, the study contributes to the literature on OSC by exploring the relationship between project characteristics and performance indicators, which can help practitioners improve their decision-making and planning processes. The study also discusses the limitations and challenges of applying ML models to OSC data, such as data availability, quality, and consistency. [ABSTRACT FROM AUTHOR]

The detection of steel surface defects is of great significance to steel production. In order to better meet the requirements of accuracy, real-time, and lightweight model, this paper proposes a highly efficient and lightweight steel surface defect detection method based on YOLOv5n. Firstly, ODMobileNetV2 composed of MobileNetV2 and ODConv is used as the backbone to improve the defect feature extraction capability. Secondly, GSConv is utilized in the neck to achieve deep information fusion through channel concatenation and shuffling, enhancing the ability of feature fusion. Finally, this paper proposes a spatial-channel reconstruction block (SCRB) designed to suppress redundant features and improve the representation ability of defect features through feature separation and reconstruction. Experimental results show that this method achieves 84.1% mAP and 109 FPS on the NEU-DET dataset, and 72.9% mAP and 110.1 FPS on the GC10-DET dataset, enabling accurate and efficient detection. Furthermore, the number of parameters is only 5.04M, which has a significant lightweight advantage. [ABSTRACT FROM AUTHOR]

To understand the effect of the interactions between Ce‐treated steel and refractory on steel cleanliness, the high‐temperature reaction behaviors of Ce‐treated Al‐killed steel with different refractories (MgO, Al2O3, MgO⋅Al2O3, and CeO2) are investigated in laboratory at different times (30–90 min), and the inclusions in steel and the total oxygen contents of the steel are also analyzed. The results show that when the MgO refractory contacts with conventional Al‐killed steel grades, MgO‐Al2O3 spinel is generated as the reacted layer at the boundary; while it reacts with Ce‐treated steel, MgO–Al2O3 spinel is also formed, but it further transforms into Ce2O2S and CeAlO3 with time. In the Ce‐treated steel, CeAlO3 is proved as the stable phase; thus, the reacted layer of CeAlO3 can also be detected at the edges of Al2O3, MgO⋅Al2O3, and CeO2 refractories. Ce treatment leads to more serious degradation of refractory, and the thickness of the reacted layers at the steel–refractory boundary decreases with time due to the spalling of the layer, resulting in the formation of many CeAlO3 macroinclusions in steel and the rise of total oxygen contents of the steel. [ABSTRACT FROM AUTHOR]

Herein, a 3D stability diagram is established in the AlON system. Based on that, four sets of experiments with different Al contents are designed to prepare different inclusions. Subsequently, the agglomeration behavior of inclusion is observed in situ by using confocal laser scanning microscopy (CLSM) combined with an infrared image furnace. The sample with inclusions is heated to melt and the agglomeration behavior of inclusion is recorded by the CRT monitor of CLSM. The calculated agglomeration force of inclusion shows that when the Al content increases from 0.5 to 3 pct, the agglomeration force of Al2O3 inclusions decreases from 7.2 × 10−16 ≈ 6.0 × 10−14 N to 1.2 × 10−16 ≈ 3.2 × 10−15 N. As the Al content increases from 6.5 to 10 pct, the agglomeration force of AlN inclusions increases from 2.2 × 10−17 ≈ 1.1 × 10−15 N to 1.7 × 10−16 ≈ 7.9 × 10−15 N. The theoretical calculation also shows that the agglomeration force of Al2O3 inclusions decreases and that of AlN inclusions increases with the increasing Al content. When the Al content is >4.7 pct, the agglomeration force of AlN inclusions is larger than that of Al2O3 inclusions. [ABSTRACT FROM AUTHOR]

To optimize the flow field of a multistrand tundish and improve the steel quality, a prediction model integrating the techniques of computational fluid dynamics (CFD) and support vector regression (SVR) is proposed. A total of 125 cases with different structure parameters, i.e., the diameter and inclination angle of the orifices, are designed. The flow field of liquid steel in the tundish is calculated by CFD, and a sample dataset is established. Then, the SVR, combining the genetic algorithm with K‐fold, is employed to train and predict the sample dataset. In the results, it is shown that the SVR model demonstrates good learning performance on the training dataset. The average absolute errors of predictions for dead volume fraction and consistency are 0.50% and 0.71%. In addition, the SVR model takes much less computational cost than the CFD method to predict the flow performance of tundish in a given baffle structure. [ABSTRACT FROM AUTHOR]

Herein, the effect of nonmetallic inclusions (NMIs) on the microstructure and dynamic recrystallization (DRX) of Fe–23Mn–6Al–0.7C low‐density steel is studied. The specimens are separately added sulfur (S) and nitrogen (N) to change the characteristics of NMIs. As a result, the addition of S significantly increases the number of MnS inclusions and AlN–MnS complex inclusions in low‐density steel. The addition of N results in a significant increase in the size of NMIs. In the results, NMIs act as the heterogeneous nucleation sites for austenite and refine the as‐cast grains in low‐density steel. In addition, the treated specimens are subjected to a thermal compression simulation experiment. During the thermal compression process, discontinuous DRX is considered to be the main recrystallization method in the experimental low‐density steels. Meanwhile, the typical NMIs significantly accelerate the DRX within grains in low‐density steel through the mechanism of particle‐stimulated nucleation and continuous DRX. [ABSTRACT FROM AUTHOR]

Two types of inclusions in the stainless steels are detected: MnO·Cr2O3–MnS dual‐phase ones and pure MnS ones. The increase of sulfur content can inhibit the formation of MnO–Cr2O3–MnS inclusions and reduce the harm of MnO·Cr2O3–MnS inclusions on the pitting corrosion of stainless steels. When the sulfur content increases from 26 to 70 ppm, the average pitting potential increases from 0.34 to 0.4 VSCE due to the decrease in the number density of MnO–Cr2O3–MnS inclusions. A Cr‐depletion zone exists in the steel matrix around MnO–Cr2O3–MnS inclusions. The size of pits induced by MnO·Cr2O3–MnS inclusions is larger, which poses a more serious threat to the pitting resistance of stainless steels. [ABSTRACT FROM AUTHOR]

A fibre laser was used to weld Q345D/20Mn2 dissimilar steel with and without a Ni60 powder filler. Finite element (FE) simulation of the temperature and stress fields in the laser beam welding (LBW) was conducted COMSOL. Experimental investigation determined the effect of Ni-based powder filled welding on the microstructure, morphology, element content, microhardness and fracture morphology of the weld cross-section. The results show that when the laser power was 2700 W, the scanning speed was 1 mm/s and the out-of-focus amount was 0 mm, the tensile properties of Q345D/20Mn2 steel welds were optimal and deformation was minimal. Under such conditions the depth of the weld pool can reach 2.7 mm and the width 2.8 mm. After the Ni-based powder melts and penetrates the bottom of the base material (BM) along the weld seam, small cytosolic, equiaxed and columnar crystal grains can be observed near the fusion line, and the Ni-based filler powder can achieve a good metallurgical bond with the BM. The location of tensile fracture is at the weld and small tough nests can be observed in the cross-section leading to judgment that the fracture mode is ductile. [ABSTRACT FROM AUTHOR]

In order to solve the problem of insufficient hardness and friction wear performance of Ni-based coatings under certain extreme working conditions, this paper designs experiments from a process perspective to study the effects of laser scanning method and overlap rate on the microstructure and properties of laser clad Ni60-WC composite coatings. Unlike previous studies, this study considers the comprehensive effects of laser scanning method and overlap rate on coating performance for specific laser clad layers, rather than just one of them. The results show that the performance of the coating after fusion is the best in the single line scanning mode and the overlap rate is within the range of 30 to 35%. The maximum hardness of the laser clad coating can reach 1216 HV, which is 1.08 to 1.43 times the 850 to 1150 HV hardness of the Ni-WC coating reported so far. The wear resistance of the laser clad coating has also been improved to some extent. The results confirm the phenomenon of interactive influence between scanning mode and overlap rate in the laser cladding process, which will provide a new 4knowledge for optimizing laser cladding in the future. [ABSTRACT FROM AUTHOR]

The single-peak overload test based on DIC technology was carried out in this study, and U71MnG steel was used to explore the influence of dislocation motion on crack propagation during overload. The changes in the shape and size of the plastic zone during the overload fatigue cycle are tracked and recorded, and the trends in the stress intensity factors of the Christopher–James–Patterson (CJP) and dislocation correction models are compared. The degree of influence of the dislocation motion on the variation in the stress intensity factors is evaluated, and the variation pattern of the plastic flow factor is derived (the amount of crack tip blunting, ρ). The results showed that the dislocation correction model increased the accuracy of the solution of the coefficient set, and the predicted size of the plastic zone of the correction model was more consistent with the experimental data. A better match with the crack tip was observed in the experimental plastic zone, the dislocation correction model error with the theoretical plastic zone fluctuates within 10%, whereas the CJP model can reach a maximum of 36.75%, demonstrating the insensitivity of the dislocation correction model. The plastic flow factor ρ follows the same pattern as that of the plastic zone area and stress intensity factor amplitude, ρ increases slowly with the increase of crack length before overload, ρ increases significantly after overload and then decreases sharply, and it recovers to be stable with the disappearance of the overload hysteresis effect of crack propagation. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the seismic response of multitiered buckling-restrained braced frames (MT-BRBFs), assess the design provisions specified by the 2022 AISC Seismic Provisions for multitiered BRBFs, and propose improvements to these provisions. A set of 17 frames is first selected by varying bracing configuration, frame height, number of tiers, and tier height ratio. The frames are then designed in accordance with the 2010 and 2022 AISC Seismic Provisions. A numerical parametric study is performed under scaled ground motion accelerations. The results of the parametric study show that when the frames are designed to the 2010 provisions, the frame inelastic deformation tends to concentrate in the tier(s) undergoing tensile yielding due to their lower postyield stiffness, compared to BRBs yielding in compression, which creates unequal story shear, contributed by braces, in adjacent tiers with BRBs in tension and compression and engages column flexure to compensate for unbalanced brace story shears between tiers. Columns experience yielding and even buckling in several cases due to combined flexural and axial load demands. MT-BRBFs designed to the 2022 AISC Seismic Provisions exhibit a more uniform deformation response between tiers and relatively lower flexural demands in their columns. However, these provisions may overestimate column in-plane flexural demands (on the order of 3), resulting in potentially uneconomical design solutions. On the basis of the numerical simulations, modifications are proposed to compression BRBs' adjusted strength to better estimate column in-plane flexure and tier deformation while achieving an economical column design. The proposed improvements are validated using dynamic analyses. [ABSTRACT FROM AUTHOR]

This study explores the possibility of using low yield point steel (LYPS) as the material for seismic retrofitting braces without casing. While buckling restrained brace has commonly been considered for LYPS applications, it is demonstrated that a more effective usage of LYPS can be achieved without the casing, which not only provides economic advantages but also facilitate a more complete utilization of the excellent ductility of LYPS. In developing design procedures for noncasing LYPS braces, calculations for stability, such as those related to compactness requirements and buckling strength, become a major concern, as seemingly too optimistic values are obtained for them when using LYPS with a particularly low yield stress. Therefore, both monotonic and cyclic loading tests were first conducted to extend the current stability-related provisions to LYPS. Cyclic test results confirmed the outstanding hysteretic performance of noncasing LYPS braces compared to those fabricated from ordinary steels. Using the results from the cyclic tests and additional test-validated numerical analyses, a nonlinear static procedure was developed for the seismic evaluation of noncasing LYPS braces. This procedure includes guides for performing a pushover analysis for the retrofitted structure and setting the acceptance criteria. The developed seismic evaluation procedure is demonstrated through a case study, in which a steel moment-resisting frame is retrofitted with noncasing bracing. Noncasing braces made of LYPS are shown to be effective in improving seismic performance, whereas those made of ordinary steel are shown to be inferior for seismic retrofit. [ABSTRACT FROM AUTHOR]

A set of seismic analysis and design requirements are presented to improve seismic stability of steel two-tiered eccentrically braced frames (EBFs) with I-shaped link beams. The proposed requirements include strength, stability, and stiffness provisions for braces, intermediate beams, and columns. In particular, these requirements aim to make use of intermediate beams to limit out-of-plane deformation of diagonal braces, torsionally brace the link beam in the intermediate level using diagonal braces, utilize column stiffness and strength to brace the intermediate beam out-of-plane, estimate and account for in-plane bending demands of the columns due to uneven yielding of the links, and control inelastic link rotation. The proposed special analysis and design requirements for two-tiered steel EBFs prevent excessive out-of-plane deformation of the intermediate beam and columns, promote sequential yielding of link beams, and limit inelastic rotation of the link in the tier experiencing the largest lateral deformation. The proposed requirements are demonstrated for a case study two-tiered EBF. Nonlinear static and dynamic analyses are performed to evaluate the seismic response of the case study frame against the frame designed without special design provisions and to validate the proposed requirements. [ABSTRACT FROM AUTHOR]

The protection of steel surfaces from wear under extreme pressure conditions is of major importance in several industries as it provides better performance and longer life of machinery. The motivation for this work was to study the lubrication of steel by ionic liquids (ILs), which have recently emerged as greener alternatives to commercial lubricants and additives. Three ILs based on sulfur-containing anions, used as 2-wt% additives in polyethylene glycol base oil (MW 200; PEG 200), were tested in the lubrication of ASTM 52100 bearing steel contacts in extreme pressure conditions (under mixed lubrication with a Hertzian pressure of 1.12 GPa) using a mini traction machine (MTM). Due to the poor resistance to corrosion of bearing steel, a semi-ester of succinic acid derivative corrosion inhibitor (Lanxess RC 4801) was added to the mixtures at a 1 wt% concentration. The ILs 1-hexyl-methylimidazolium trifluoromethanesulfonate ([C6mim][TfO]) and 1-hexyl-4-picolinium trifluoromethanesulfonate ([C6-4-pic][TfO]) revealed promising results in terms of surface protection of bearing steel. In contrast, 4-picolinium hydrogen sulfate ([4-picH][HSO4]) as 2-wt% additive to PEG 200 + 1% RC 4801 did not show any improvement in wear performance compared to neat PEG 200 + 1% RC 4801. PEG 200 + 2% [C6mim][TfO] + 1%RC 4801 allowed for a decrease in wear up to ~ 76% and PEG 200 + 2% [C6-4-pic][TfO] + 1%RC 4801 up to ~ 46% when compared with neat PEG 200 + 1% RC 4801. Optical microscopy images suggest the formation of an adsorbed layer, which was further supported by chemical analysis via x-ray photoelectron spectroscopy (XPS) data for [C6mim][TfO]. [ABSTRACT FROM AUTHOR]

As deep learning advances, neural network technologies are increasingly penetrating the field of steel surface defect detection. To tackle the challenges of low accuracy and inadequate quality, we introduce CMS-YOLOv8s, a defect detection algorithm engineered for superior precision and efficiency. Initially, integrate the CBAM to enhance the network's focus on relevant information, allowing it to leverage multi-dimensional data like spatial and channel dimensions fully. Next, introduce the SPPFCSPC module to fuse feature information from different scales, expanding the model's receptive field and enhancing its feature extraction abilities. Finally, incorporate a small object detection head to boost the model's capability in identifying tiny targets, strengthening its ability to detect targets across different scales. Experimental findings show that CMS-YOLOv8s attains a detection accuracy of 70.4%, registering a significant 3.3% enhancement compared to the original YOLOv8s. This advancement distinctly improves defect detection accuracy across all categories. [ABSTRACT FROM AUTHOR]

The blast resistance of a typical two-lane steel girder highway bridge structural system was modeled using a nonlinear finite-element approach that considered material damage, fracture, and separation. Critical blast scenarios were based on field observations of terrorist attacks on bridges in Iraq, while system failure was defined in terms of practical emergency serviceability criteria used on actual blast-damaged bridges. The blast resistance of various design parameters was assessed, including the number of girders, deck concrete strength, reinforcement ratio, slab thickness, girder and reinforcement yield strength, girder sectional dimensions, and pier column width. The presented approach uniquely quantifies structural system blast resistance in terms of the charge weight that can be applied at different locations until failure. A sensitivity analysis was conducted to determine the most influential design parameters. It was found that system blast capacity was primarily influenced by the number of girders and girder yield strength, while additional significant parameters were deck compressive strength, deck thickness, web stiffener width, and girder depth. Secondary parameters were deck reinforcement ratio, girder flange, and web thickness, while deck reinforcement yield stress was found to be insignificant. Based on the results, recommendations for improving blast resistance are provided. [ABSTRACT FROM AUTHOR]

This paper investigates a steel moment resisting frame (MRF) with a novel type of self‐centering (SC) base isolators, wherein superelastic shape memory alloy (SMA) U‐shaped dampers (SMAUDs) work as core components. A two‐story steel MRF model equipped with two SMAUD‐based isolators was designed and built in the laboratory, and a series of shake table tests were conducted to examine the dynamic behavior and seismic performance of the frame. Throughout all the tests, no interventions, such as repair or replacement of frame or isolator members, were done. Shake table test results demonstrated that the SMAUD‐based isolators could withstand multiple strong earthquakes with stable SC behavior. The utilization of SMAUD‐based isolators provided effective protection for the frame, enabling it to restore its original position with minimal structural damage. A numerical model of the tested steel MRF with SMAUD‐based isolators was also built. The results obtained from the numerical analyses agreed with those of the shake table tests satisfactorily. A comparative study of the seismic performance between the MRF with SMAUD‐based isolators and the MRF with traditional steel U‐shaped damper‐based isolators was also conducted in the shake table tests. The results showed that SMAUD‐based isolators not only inherit the isolation function of conventional isolators to protect the frame but also possess an SC ability to eliminate residual isolator deformation effectively. Moreover, SMAUD‐based isolators demonstrate remarkable resilience to withstand multiple strong seismic events without any need for repair or replacement. [ABSTRACT FROM AUTHOR]

In this paper, the tensile properties, texture evolution, and deformation anisotropy of a cold-rolled Fe−0.3C–6.86Mn–3.5Al steel during superplastic deformation at 650 °C–750 °C and 0.25 × 10−3 s−1− 4 × 10−3 s−1 were studied. In particular, under 750 °C and 1 × 10−3 s−1, the anisotropic microstructure evolution and texture characteristics were measured using EBSD. The results indicate that Medium Mn steel (MMS) sheets exhibit significant anisotropy under high tensile stress. The transverse direction (TD) specimens exhibit the highest peak strength of 145 MPa, and rolling direction (RD) specimens exhibit the highest elongation of 1295 pct. The plastic anisotropy r value of the RD sample varied more significantly than that of the TD sample. When the RD sample fractures, the aspect ratio reaches its minimum value (1.52), and ellipse fitting angle (θ) distributes from 0 to 90 degree and from 180 to 90 degree, which indicates that a large number of grains have undergone rotation. [ABSTRACT FROM AUTHOR]

Prominent δ-ferrite to γ-austenite transition in the coarse-grained heat-affected zone of P92 steel has been documented in situ by confocal scanning laser microscope under different thermal cycles, with emphasis on the quantifying of migration of the γ/δ interface. With reducing cooling rate, the fraction of retained δ-ferrite decreases appreciably from 12.0 to 1.6 pct. It is further quantified that the average migration distance of γ/δ interface is enhanced from 10.74 to 17.81 μm. [ABSTRACT FROM AUTHOR]

The investigation focused on the precipitation behavior and mechanism during ferrite transformation in a Nb-alloyed steel, revealing a diverse range of NbC morphologies. The presence of interphase precipitation in regular sheet planes with three variants was attributed to a higher interfacial migration rate, while the non-uniform sheet spacing of interphase precipitation increased as the phase boundary approached. A qualitative analysis using the solute drag effect (SDE) model may potentially elucidate the non-uniform sheet spacing observed. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the effect of titanium on the corrosion characteristics of bridge weathering steel plates in marine environments. The corrosion characteristics of steel containing different Ti additions were studied by simulating marine corrosion by cycles of the dry and wet environments. The addition of appropriate amounts of Ti can promote the production of γ-Fe2O3, which produces a protective rust layer. Steel containing 0.087 wt pct Ti, gave the best results. During long-term dry/wet cyclic corrosion experiments, the corrosion rate of the #0.087Ti steel first accelerated when a protective product layer has not completely covered the surface. The surface of the #0.087Ti steel was only fully covered after 144 hours of testing. With the further extension of periodic immersion testing the corrosion rate began to decrease gradually. After 576 hours of testing a stable protective product layer formed on the #0.087Ti steel, limiting further corrosion. [ABSTRACT FROM AUTHOR]

EH36 shipbuilding steels with varied Ti contents have been designed to investigate the roles of Ti upon inclusion evolution and microstructural characteristics. As the Ti content increases, the number density of Ti-containing inclusions appreciably multiplies, and corresponding area fraction of acicular ferrite boosts sharply from 5.0 to 29.9 pct. Additionally, through in-situ confocal scanning laser microscopy, it is clarified that acicular ferrite start temperature has been elevated, thanks to the population of Ti-containing inclusions. [ABSTRACT FROM AUTHOR]

The influence of stress/strain on the movement/rearrangement of γ / ϵ interfaces and the coalescence of ϵ plates under a fixed location of a high Mn steel have been investigated through fractal measurement of ϵ plates. Image texture analysis has also been implemented to recognize the stored energy and configurational stability of such plates under γ matrix as a function of tensile deformation. Fractality of ϵ variants are correlated with their geometrical configurations at different directions with systematic increment of tensile strain. [ABSTRACT FROM AUTHOR]