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The prediction of the martensite start temperature (Ms) for steels based on their chemical compositions is a complex problem. Previous work has developed empirical, thermodynamic, and machine learning models to estimate Ms. However, the empirical models are limited to specific steel grades, the thermodynamic models rely on different model assumptions, and the machine learning models are based on a small number of data, are limited to specific steel grades, as well or are not available for easy use to the public. Herein, a new machine learning model for the prediction of Ms is developed on the basis of two publicly available datasets consisting of 1800 steels from different steel grades. Extensive hyperparameter tuning is performed to find the best artificial neural network for the dataset. The best model improves prediction accuracy compared to previous state of the art. Despite a very good prediction accuracy of the model, unexpected behavior is observed in specific unseen data. This opens up the discussion for the requirements of new metrics. The dataset and the model are freely available at https://github.com/EAH‐Materials. An easy‐to‐use web tool to estimate Ms without the need of programming based on the chemical composition can be found at https://eah‐jena‐ms‐predictor.streamlit.app/. [ABSTRACT FROM AUTHOR]

Hydrogen segregation behaviors at BCC-Fe Σ3 (111) grain boundary (GB) as well as the effects of alloying solutes were studied by the first-principles method. The segregation energy of alloying solutes at different periods presents a concave-down parabolic-like relationship with the atomic number, and the 4 d transition alloying solutes show a higher averaged segregation tendency. At the favorable trapping site, hydrogen segregation energy decreased by increasing the number of hydrogen atoms up to 0.85/Å2 in the plane vertical to the GB. Mo, Tc, Ru, Ta, W, Re, Os, and Ir strengthen GB and inhibit hydrogen segregation. Significantly, the interaction between alloying solutes and hydrogen segregation was elucidated by emphasizing the separation of the chemical and the mechanical contributions, and appropriate descriptors on hydrogen segregation energy influenced by alloying solutes were screened. This work offers theoretical backing to comprehend hydrogen segregation behaviors and the effects of alloying solutes to design advanced high-strength steels resistant to hydrogen embrittlement. • Hydrogen segregation behaviors at pure BCC Σ3 (111) grain boundary were studied. • Alloy solute segregation behaviors at pure BCC Σ3 (111) grain boundary were studied. • Interaction between alloying solutes and hydrogen at grain boundary was elucidated. • Descriptors on hydrogen segregation energy at grain boundary were screened. • Relationship between hydrogen segregation at grain boundary and HE was discussed. [ABSTRACT FROM AUTHOR]

Continuous casting is the most common method for producing steel into semi-finished shapes like billets or slabs. Throughout this process, steel experiences mechanical and thermal stresses, which influence its mechanical properties. During continuous casting, decreased formability in steel components leads to crack formation and failure. One reason for this phenomenon is the appearance of the soft ferrite phase during cooling. However, it is unclear under which conditions this ferrite is detrimental to the formability. In the present research, we investigated what microstructural changes decrease the formability of microalloyed steels during continuous casting. We studied the hot compression behaviour of microalloyed steel over temperatures ranging from 650 °C to 1100 °C and strain rates of 0.1 s − 1 to 0.001 s − 1 using a Gleeble 3800® (Dynamic Systems Inc, Poestenkill, NY, USA) device. We examined microstructural changes at various deformation conditions using microscopy. Furthermore, we implemented a physically-based model to describe the deformation of austenite and ferrite. The model describes the work hardening and dynamic restoration mechanisms, i.e., discontinuous dynamic recrystallisation in austenite and dynamic recovery in ferrite and austenite. The model considers the stress, strain, and strain rate distribution between phases by describing the dynamic phase transformation during the deformation in iso-work conditions. Increasing the strain rate below the transformation temperature improves hot ductility by reducing dynamic recovery and strain concentration in ferrite. Due to limited grain boundary sliding, the hot ductility improves at lower temperatures (<750 °C). In the single-phase domain, dynamic recrystallisation improves the hot ductility provided that fracture occurs at strains in which dynamic recrystallisation advances. However, at very low strain rates, the ductility decreases due to prolonged time for grain boundary sliding and crack propagation. [ABSTRACT FROM AUTHOR]

Demand for steel scrap as feedstock for steelmaking increases, allowing the production of steel with lower energy costs and reduced CO2 emissions. In general, steel scrap may contain high levels of undesirable residual elements, which may contribute to processing challenges such as surface hot‐shortness, bulk hot‐shortness, hot‐brittleness, and higher rolling loads during the hot‐working process of steel production. The effect of different residual elements during the hot‐deformation process is a broad topic and involves the understanding of both individual and combined behavior of residual elements for different thermal and mechanical conditions that arise. In this article, the behavior of various residual elements is critically reviewed, individually and synergistically at high temperatures during the hot‐working process (i.e., reheat furnace stage, descaling stage, and deformation stage) of steel production, with a focus on (surface) hot‐shortness, delayed recrystallization, and higher rolling loads caused by the residual elements. Herein, it is aimed to help the steel community to identify challenges and opportunities in efficiently utilizing steel scrap. [ABSTRACT FROM AUTHOR]

Reliable microstructure characterization is essential for establishing process–microstructure–property links and effective quality control. Traditional manual microstructure analysis often struggles with objectivity, reproducibility, and scalability, particularly in complex materials. Machine learning methods offer a promising alternative but are hindered by the challenge of assigning an accurate and consistent ground truth, especially for complex microstructures. This paper introduces a methodology that uses correlative microscopy—combining light optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD)—to create objective, reproducible pixel-by-pixel annotations for ML training. In a semi-automated manner, EBSD-based annotations are employed to generate an objective ground truth mask for training a semantic segmentation model for quantifying simple light optical micrographs. The training masks are directly derived from raw EBSD data using modern deep learning methods. By using EBSD-based annotations, which incorporate crystallographic and misorientation data, the correctness and objectivity of the training mask creation can be assured. The final approach is capable of reproducibly and objectively differentiating bainite and martensite in optical micrographs of complex quenched steels. Through the reduction in the microstructural evaluation to light optical micrographs as the simplest and most widely used method, this way of quantifying microstructures is characterized by high efficiency as well as good scalability. [ABSTRACT FROM AUTHOR]

Previous research has indicated that hydrogen decreases the fracture toughness of gas‐transmission pipeline steels. This study produced two values of fracture toughness for the X65 steel in the Dampier Bunbury natural gas‐transmission pipeline in air (JQ of 590 and 778 kJ m−2; equivalent to KQ of 369 and 487 MPa√m$\sqrt{} \text{m}$) and two essentially American Society for Testing of Materials–valid values of fracture toughness of KJ1C of 150 and 189 MPa√m$\sqrt{} \text{m}$ for X65 subjected to in situ hydrogen charging thought to be equivalent to a hydrogen gas pressure of 200 bar. The fracture toughness for hydrogen‐charged specimens was lower than in air. The large spread of the fracture toughness in air was attributable to the fact that these JQ values were dependent on testing details. The spread of fracture toughness values in hydrogen was attributed to the variability of fracture toughness in hydrogen under these hydrogen‐charging conditions. There was considerable stable crack growth. The energy for stable crack growth increased with crack length. The fractography in the presence of hydrogen showed significant ductility, consistent with hydrogen‐assisted plastic fracture. The values of fracture toughness in air and with hydrogen were consistent with literature values. [ABSTRACT FROM AUTHOR]

This research project, reported in three parts, focuses on Henry Nock’s ‘screwless lock’, or, as it is called in documents at the time of its manufacture, the ‘Duke’s Lock’, in the most important production variant of this novel and sophisticated design. This is the 5.5in long ‘Type 2’ Duke’s Lock, as fitted to the final design iteration of the Board of Ordnance’s Duke of Richmond’s Musket (DoRM), namely its rammer-to-the-muzzle (RTM) version. The three papers report the results of the first published systematic assessment of the Duke’s Lock’s interchangeability. No statement has yet been found in archival material to suggest that the lock is, or was considered to be, interchangeable, or that it has interchangeable components, but the authors of many secondary works think that it was, and therefore we set out to investigate this important matter systematically. This, the first paper, presents the findings of a five-lock component exchange experiment, which permits 20 component interchange tests. Measurements of key dimensions have also been made to assist in understanding the fits at which interchangeability was achieved. The exchange experiments establish that from 50% to 100% of the lock’s small components are interchangeable, with two especially surprising results: all cocks exchange on the large centres of the locks (20/20 or 100%), and all sears which can be tested are found to exchange between bents (17/17 or 100%). Tests assessing the complete assembly of all components in the lock thickness direction, omitting problematic individual components, show success rates of 16/20 (80%) and 14/20 (70%). The results of this process are placed in a material context through metallographic analysis of components of a less well-preserved Board of Ordnance 5.5in Duke’s Lock by Nock, and, for comparison, on an almost contemporary Board of Ordnance India Pattern Musket lock. The analysis has revealed that many components of the Duke’s Lock are made of steel rather than wrought iron, and that, for the centres and some other key components, these steels were selected because their properties suited machine turning, and this reflects Nock’s expert use of lathes within a factory that was using steam power by 1795. The analysis is supported by the disassembly and technical examination of some locks, including one that was partially completed, to analyse methods of construction. As regards archival sources, we have built upon Howard Blackmore’s seminal paper of 1956 by discovering additional archival data in the Ordnance Bill books, specifically the records of transactions with Nock’s executors after his death in 1804, to as late as 1808. This has allowed an improved understanding of the number of locks supplied and the uses to which they were put. The Ordnance Bill Books show that Nock delivered 12,010 Duke’s Locks in only 29 months, between 4 July 1793 and 25 November 1795. Together the papers explore how Henry Nock was able to produce the remarkable figure of 12,010 interchangeable locks in 1793–95, five years before the production of 10,000 interchangeable locks was achieved in France by Honoré Blanc, who is widely regarded as the first in this field. Significantly, Nock’s work also preceded that of Samuel Bentham, Mark Brunel and Henry Maudslay on the famous machines for making interchangeable components – in wood – for the blocks required for ships’ rigging; the three principals began their work on this in 1799. The present three-part study not only firmly establishes Henry Nock’s leading position in the field of firearm development but also as one of the pioneers of interchangeable manufacture at scale in engineering more widely, both nationally and internationally. Part 2 uses studies of the marks on a sample of 25 locks to reveal more about the manufacturing system for Duke’s Lock and how the people within the system were organised. The final paper, Part 3, discusses the small changes in design and inspection made during and after production that are revealed in the earlier Parts, and also how the design of George Bolton’s later patent lock was influenced by Nock’s work and the experience of his workmen. [ABSTRACT FROM AUTHOR]

Self‐organized ripple and pillar structures are fabricated on steel surface using femtosecond laser. Their wettability is investigated in terms of static contact angle, roughness, and chemical bonds. The pillar structure is treated in low surface energy solution to further improve its hydrophobicity. The corrosion and biofouling behaviors of the structures in sea water are investigated by electrochemical and chlorella immersion experiments, respectively. The results show that the ripple structure is hydrophilic with a static contact angle similar to the original surface, while the pillar structure is highly hydrophobic since it has higher roughness and amount of non polar chemical bonds. The pillar structure is further transferred to superhydrophobic through the low surface energy treatment. The improved hydrophobicity facilitates a better anti‐corrosion and anti‐biofouling behavior, and the superhydrophobic pillar structure exhibits the best performance due to its strongest ability to repel water and chlorella adhesion. [ABSTRACT FROM AUTHOR]

The application of organic coatings is the most cost-effective and common method for metallic equipment toward corrosion, whose anti-corrosion property needs to be improved and evaluated in a short time. To rapidly and rationally assess the anti-corrosion property of organic coatings in the ocean splash zone, a new accelerated test was proposed. In the study, the corrosion protection property of the coating samples was measured by an improved AC-DC-AC test in a simulated seawater of 3.5 wt.% NaCl solution, a simulated ocean splash zone test and a new accelerated test combining the above two tests. The results showed that the corrosion rate of the coating samples was high in the improved AC-DC-AC test, which lost its anti-corrosion property after 24 cycles equal to 96 h. The main rapid failure reason was that the time of the water and corrosive media arriving at the carbon steel substrate under the alternating cathodic and anodic polarization with symmetrical positive and negative electric charges was shortened. The entire impedance of the coating samples was improved by about 1.6 times more than that in the initial early time in the simulated ocean splash zone test, which was caused by the damage effect from the salt spraying, drying, humidifying, salt immersion, high temperature and UVA irradiation being weaker than the enhancement effect from the post-curing process by the UVA irradiation. In the new accelerated test, the samples lost their corrosion resistance after 12 cycles equal to 288 h with the fastest failure rate. On account of the coupling process of the salt spraying, drying, humidifying, salt immersion, high temperature combined with the cathodic and anodic polarization and the UVA irradiation, the penetration and transmission rate of water and corrosive media in the coating were further accelerated, the corrosion rate on the carbon steel substrate was reinforced even larger and the destruction of the top polymer molecules was more serious. The new accelerated test showed the strongest damage-acceleration effect than that in the other two tests. [ABSTRACT FROM AUTHOR]

The acid pickling phase, generally entrusted to HCl‐based solutions, plays a fundamental role in the production of low‐C and interstitial‐free steel coils. Very often, however, pickling operations are challenging due to the possible onset of surface defects (underpickling, overpickling, appearance of surface defects, etc.) linked to complex phenomena involving numerous factors, such as acid concentration, Fe ions in solution, temperature, time, steel type, and scale structure. Moreover, the use of inhibitors, which is essential for controlling the pickling process, represents one of the major challenges. Their dosage, although minimal, must be carefully chosen based on the type of processed coils and other plant engineering variables. The flow of hydrogen that is generated on the surface of the steel during etching causes absorption of hydrogen by the metal and its measurement is strictly linked to the phenomena occurring during scale removal. The correlation of data obtained from a Devanathan double‐cell hydrogen permeation system to results of other techniques, such as weight loss, surface analysis, metallography, and electron microscopy shows that this system can be effectively used to indirectly measure the solution aggressiveness. This experimental approach is applied to two industrial steels: a simple carbon base and an interstitial free Ti steel. [ABSTRACT FROM AUTHOR]

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The present case study involves a thorough and methodical metallurgical analysis of a failed water wall tube to identify sulfidation corrosion as the cause of failure. The investigation into the failure of the water wall tube was conducted through various methods, including visual observation, chemical analysis, examinations using optical and scanning electron microscopy, fractography and surface analysis via SEM–EDS, x-ray diffraction analysis of deposits and reaction products, and evaluation of mechanical properties. The water wall tube exhibited failure in the form of an elliptical puncture, with no significant thinning at the location of the puncture. The chemical composition, mechanical properties, and microstructure of the failed water wall tube were in accordance with the specified standards for SA 210 grade C steel. The microstructure of the tube consisted of a ferrite–pearlite structure and showed no anomalies related to microstructure. The experimental results revealed that the tube failed due to sulfidation corrosion on its outer surface. This sulfidation reaction was initiated by sulfur from pyrite (FeS2) in the coal-ash deposits on the outer surface. Moreover, the buildup of ash deposits caused localized overheating, which accelerated the sulfidation reaction, followed by an oxidation reaction. [ABSTRACT FROM AUTHOR]

This study investigates the factors that affect surface quality in low-speed milling of steel with a hardness greater than 50 HRC, specifically for forming molds. The material used in the experiment was SKT4 mold steel with a hardness of 50 HRC, which is commonly employed to form molds, with dimensions of 100x100x50 mm. The cutting tools put into service were carbide ball end mills of the HARD Series 5Rx10x60L. This study examines changes in the surface roughness values of the milled workpiece material based on the feed rate and cutting depth. The constant spindle speed deployed was 1,200 rpm, and heat dissipation was achieved by air cooling. The results revealed that the feed rate and the interaction between the feed rate and the cutting depth had a p-value of 0.000. This considerably influences the average surface roughness (Ra) value at the 0.05 significance level. However, the cutting depth had a p-value of 0.061, which is greater than the significance level of 0.05 and thus does not substantially affect the average surface roughness. [ABSTRACT FROM AUTHOR]

During hard machining, steels subjected to very high thermal and mechanical loads can result in microstructural/phase changes such as the formation of a white layer. This layer, which is often harder than the raw material, is considered detrimental to the fatigue performance and in-service life of machined parts. This paper proposes a comprehensive study of white layer formation during hard machining of steels using statistical analysis and artificial neural networks (ANN) modeling. To this end, two steals, named AISI 52100 and AISI 4340, commonly used in the manufacturing of structural machines' components and extensively studied in the last decade, have been considered in this study. First, Taguchi method combined with response surface methodology (RSM) was applied to analyze and to optimize the machining parameters regarding the white layer thickness. Second, an ANN model is developed to predict the white layer thickness during hard machining of the studied steels using a large amount of machining data. Three training algorithms were tested to find the most robust configuration. The equivalent carbon parameter was introduced for the first time in machining modeling which make the proposed ANN-based model capable of predicting the white layer thickness for different hardened steels. The results show a significant agreement between predictions and experimental results, avoiding costly experimental machining tests. [ABSTRACT FROM AUTHOR]

Previous research has consistently found that introducing metastable retained austenite (RA) as a second phase retards the failure of steel under fatigue. However, the reasons for this benefit are not understood. Accordingly, the properties of RA most advantageous to resist fatigue are not known. Within this context, this paper examines the interaction between second-phase RA and short fatigue crack growth in a steel processed via quenching and partitioning, using quasi in situ electron backscatter diffraction experiments. Results show that most RA transforms into martensite under the plastic strain surrounding the crack. They also reveal various mechanisms whereby RA transformation delays short fatigue crack propagation; transformation-induced crack closure (TICC), crack deflection and branching, and roughness-induced crack closure (RICC). Crack deflection and branching are driven by a tendency of cracks to propagate towards transformed RA, which is against the previous assumptions in the literature. Furthermore, the impact of crack deflection/branching on retardation is more powerful than that of TICC acting alone. Microstructures including second-phase RA should avoid RA-lean areas and promote elongated RA grains, with relatively large size, and major axis normal to the preferential crack growth direction. Untransformed RA within the plastic zone (i.e. overstabilized) does not contribute to crack retardation.

AbstractThe thermodynamics of mass transfer during gaseous carburization and its overall efficiency across various alloyed steels were investigated to discern the influence of alloy content. Quantitative analyses were conducted on the coefficients of mass transfer and carbon diffusivities for EN3, EN35, 20MnCr5, and EN353 steels at a carburization temperature of 930 °C. The study revealed distinct trends in mass transfer dynamics and carbon diffusion rates among the different alloyed steels. For instance, nickel majorly an austenite stabilizer, was found to enhance carbon diffusion in gamma iron, with observed coefficients of mass transfer ranging from 8.85 × 10−6 to 1.87 × 10−5 cm/s. However, EN35 steel exhibited slower mass transfer rates due to weaker atomic interactions, resulting in lower observed coefficients of mass transfer. Conversely, chromium and molybdenum, known carbide-forming elements, facilitated carbon transfer from the gaseous environment to the steel case in 20MnCr5 and EN353 steels, with observed coefficients of mass transfer ranging from 1.39 × 10−5 to 1.55 × 10−5 cm/s. Additionally, the study compared observed carbon diffusivities with those predicted by DICTRA (Diffusion Controlled TRAnsformation) kinetic and thermodynamic datasets, demonstrating excellent consistency. These findings underscore the significance of considering alloy content in achieving consistent carburizing outcomes and suggest potential modifications to existing carburizing methods to improve diffusion depth homogeneity. Overall, the study provides valuable insights into the impact of alloy elements on the carburization process and offers implications for optimizing carburizing practices in alloy steel manufacturing.

Activating fluxes can be used in welding processes like gas metal arc welding (GMAW) or tungsten inert gas welding (TIG) to improve the welding outcomes, as they can affect mechanical properties and microstructure as well as weld bead geometry, depth of penetration, shielding gas behavior, etc. The application of activating fluxes was researched on a wide range of welding materials like iron, magnesium, aluminum, or titanium alloys. This paper offers a summarized review of the effects of activating fluxes on the metallurgical properties of ferrous materials, presenting the influence of activating fluxes on the increase of ferrite content, phase transformation, and grain size. [ABSTRACT FROM AUTHOR]

The formation of defects such as cracks in continuous casting deteriorates the quality of cast products and efficiency of steelmaking. To evaluate the risks and identify the root causes of defect formation, phenomenological quality criteria computed with a solidification and microstructure model known as InterDendritic Solidification (IDS) have previously been applied. This approach is computationally efficient and provides a fundamental perspective to defect formation in continuous casting. The aim of this work is to study the capabilities of these criteria as features in predicting transverse cracking with interpretable machine learning models. IDS is coupled with a heat transfer model known as Tempsimu to simulate the continuous casting process. Measured compositions are utilized in the simulations and defects reported at a steelmaking plant are used as labels in classification. Logistic regression, decision tree, and Gaussian Naïve Bayes classifiers are developed to predict transverse cracking in peritectic C–Mn, low‐carbon B–Ti microalloyed, and peritectic Nb‐microalloyed steels. The corresponding balanced accuracies of the best classifiers from cross‐validation are 92%, 94.6%, and 82.8%. Due to the good performance and the interpretability of the developed classifiers, the fundamental causes of transverse cracking and possibilities of avoiding it by changes in the compositions are identified. [ABSTRACT FROM AUTHOR]

The microstructure evolution during dissimilar friction stir welding of copper with stainless steel 316L is studied. The welding is performed in transparence configuration using tools of two different geometries. The joints are characterized by optical microscopy, scanning and transmission electron microscopy, electron backscattered diffraction, and microhardness. The microstructure and crystallographic texture of base metals are significantly affected. The joint produced using a shoulder of 8 mm in diameter is characterized by a copper nugget with refined grains. The texture of copper is dominated by B/B¯$B / \bar{B}$ component of the shear texture. The steel beneath the tool shows a grain refinement with grains of sub‐micron size and a texture which is close to the ideal simple shear texture. For the joint produced by the 16 mm diameter tool shoulder, the nugget consists of large grains of copper, while the steel beneath the tool shows small recrystallized grains of micrometer size. The texture in the steel is dominated by the B/B¯$B / \bar{B}$ component of the shear texture. The Cu/316L interface in both types of joint is of very good quality. In a detailed study of the interface, it is revealed that the welding of metals is achieved by mutual intense mechanical interlocking without formation of any intermetallic compounds. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive review of electric arc furnace (EAF) slag recycling in the United States, examining its classification and the associated challenges and opportunities of its industrial use. The study affirms EAF slag's nonhazardous status. The main challenges identified in EAF slag applications include substantial variations in composition and volume instability during/after hydration. Analysis of the U.S. recycling practices reveals that EAF slag is predominantly reused, with minimal landfill disposal. However, its prevalent use as a low value‐added aggregate in construction applications underscores the industry's ongoing challenge to get additional value from EAF slag recycling. Despite these challenges, the study highlights a great potential for increased value extraction from EAF slag recycling. Beyond conventional applications as a clinker material for the cement industry, the review explores modern technologies for steelmaking slag recycling, revealing options for recovering valuable metals such as Cr, V, Mo, and Fe through methods such as leaching, reduction, and oxidation. [ABSTRACT FROM AUTHOR]

The phase transformation temperature plays an important role in the design, production and heat treatment process of steels. In the present work, an improved version of the gradient-boosting method LightGBM has been utilized to study the influencing factors of the four phase transformation temperatures, namely Ac1, Ac3, the martensite transformation start (MS) temperature and the bainitic transformation start (BS) temperature. The effects of the alloying element were discussed in detail by comparing their influencing mechanisms on different phase transformation temperatures. The training accuracy was significantly improved by further introducing appropriate features related to atomic parameters. The melting temperature and coefficient of linear thermal expansion of the pure metals corresponding to the alloying elements, atomic Waber–Cromer pseudopotential radii and valence electron number were the top four among the eighteen atomic parameters used to improve the trained model performance. The training and prediction processes were analyzed using a partial dependence plot (PDP) and Shapley additive explanation (SHAP) methods to reveal the relationships between the features and phase transformation temperature. [ABSTRACT FROM AUTHOR]

This article analyzes the turbulence dissipation rate in liquid steel in selected metallurgical equipment (i.e., electric arc furnace, ladle furnace, and tundish) based on advanced computational fluid dynamics simulations. The approach enables evaluation of the efficiency of electromagnetic stirrer (EMS) devices based on the molten steel flow behavior in comparison with the standard mixing process. Particular attention is put on the determination of the effectiveness of novel EMS with the horizontal stirring device, which supports the mixing process of molten steel. For that, the concept of the new formula to evaluate the stirring energy is presented and compared with the literature results to prove the correctness of the developed method. [ABSTRACT FROM AUTHOR]

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels. [ABSTRACT FROM AUTHOR]

The hydrogen solubility in ferritic and martensitic steels is affected by hydrostatic stress, pressure, and temperature. In general, compressive stresses decrease but tensile stresses increase the hydrogen solubility. This important aspect must be considered when qualifying materials for high‐pressure hydrogen applications (e.g., for pipelines or tanks) by using autoclave systems. In this work, a pressure equivalent for compensating the effect of compressive stresses on the hydrogen solubility inside of closed autoclaves is proposed to achieve solubilities that are equivalent to those in pipelines and tanks subjected to tensile stresses. Moreover, it is shown that the temperature effect becomes critical at low temperatures (e.g., under cryogenic conditions for storing liquid hydrogen). Trapping of hydrogen in the microstructure can increase the hydrogen solubility with decreasing temperature, having a solubility minimum at about room temperature. To demonstrate this effect, the generalized law of the hydrogen solubility is parameterized for different steels using measured contents of gaseous hydrogen. The constant parameter sets are verified and critically discussed with respect to the high‐pressure hydrogen experiments. [ABSTRACT FROM AUTHOR]

Refractories have a significant impact on the cleanliness of molten steel, especially when utilized as ceramic filters. To explore the feasibility of applying rare‐earth oxides in ceramic filters, the interactions between CeO2/CeAlO3 functional refractories and steels with different Al contents are explored, and compared with the microporous magnesia refractory. In the test of CeO2 refractory, the total oxygen (T.O) content significantly increases, while the dissolved Al content obviously decreases in 38CrMoAl steel (0.876 wt% [Al]). Furthermore, the T.O contents in 38CrMoAl and X70 steel (0.040 wt% [Al]) in the test of CeAlO3 refractory are 22.9% and 70.9% of that in the test of microporous magnesia refractory, respectively. Meanwhile, the loss of dissolved Al in steel caused by the interaction between CeAlO3 refractory and steel is relatively small. Therefore, CeAlO3 is relatively stable after contact with molten steel and promising to be applicated in the ceramic filter for improving the cleanliness of molten steel. [ABSTRACT FROM AUTHOR]

A procedure is outlined for calibrating a finite element model to simulate ductile cracking that employs a continuum damage criterion for ductile fracture initiation, termed the Stress Weighted Ductile Fracture Model, with an Adaptive Cohesive Zone method to simulate crack propagation. The proposed procedure is implemented and validated with data from 44 coupon‐scale tests of an A913 structural steel. The fracture model calibration is performed in two stages to determine parameters to evaluate: (1) the continuum damage mechanics criterion and (2) ductile crack initiation and propagation. Sensitivity of the calibration to parameter uncertainty is evaluated using synthetic data, followed by calibration and validation against experimental test data. The results indicate that the computational model can accurately simulate the overall response of experimental specimens, as well as other key aspects of observed behavior, including crack tunneling and crack face closure. Guidelines are provided for practical calibration of the model components. Highlights: A calibration method for simulating ductile crack propagation in steels is proposed.The calibration method is validated against the results of experimental tests.The proposed model may be used to simulate ductile cracking in steel structures. [ABSTRACT FROM AUTHOR]

Activating fluxes can be used in welding processes like gas metal arc welding (GMAW) or tungsten inert gas welding (TIG) to improve the welding outcomes, as they can affect mechanical properties and microstructure as well as weld bead geometry, depth of penetration, shielding gas behavior, etc. The application of activating fluxes was researched on a wide range of welding materials like iron, magnesium, aluminum, or titanium alloys. This paper offers a summarized review of the effects of activating fluxes on the metallurgical properties of ferrous materials, presenting the influence of activating fluxes on the increase of ferrite content, phase transformation, and grain size.

Integrated computational materials engineering (ICME) is emerging as an increasingly powerful approach to integrate computational materials science tools into a holistic system and address the multiscale modeling challenges in the processing of advanced steels. This work aims at incorporating macroscopic model (finite element-based thermal model) and microscopic model (CALPHAD-based microstructure model), building an industry-oriented computational tool (MICAST) for casting of steels. Two case studies were performed for solidification simulations of tool steel and stainless steel by using the CALPHAD approach (Thermo-Calc package and CALPHAD database). The predicted microsegregation results agree with the measured ones. In addition, two case studies were performed for continuous casting and ingot casting with selected steel grades, mold geometries and process conditions. The temperature distributions and histories in continuous casting and ingot casting process of steels were calculated using in-house finite-element code which is integrated in MICAST. The predicted temperature history from the casting process simulation was exported as input data for the DICTRA simulation of solidification. The resulting microsegregation by the DICTRA simulation can reflect the microstructure evolution in the real casting process. Current computational practice demonstrates that CALPHAD-based material models can be directly linked with casting process models to predict location-specific microstructures for smart material processing.

Continuous casting is the most common method for producing steel into semi-finished shapes like billets or slabs. Throughout this process, steel experiences mechanical and thermal stresses, which influence its mechanical properties. During continuous casting, decreased formability in steel components leads to crack formation and failure. One reason for this phenomenon is the appearance of the soft ferrite phase during cooling. However, it is unclear under which conditions this ferrite is detrimental to the formability. In the present research, we investigated what microstructural changes decrease the formability of microalloyed steels during continuous casting. We studied the hot compression behaviour of microalloyed steel over temperatures ranging from 650 °C to 1100 °C and strain rates of 0.1 s−1 to 0.001 s−1 using a Gleeble 3800® (Dynamic Systems Inc, Poestenkill, NY, USA) device. We examined microstructural changes at various deformation conditions using microscopy. Furthermore, we implemented a physically-based model to describe the deformation of austenite and ferrite. The model describes the work hardening and dynamic restoration mechanisms, i.e., discontinuous dynamic recrystallisation in austenite and dynamic recovery in ferrite and austenite. The model considers the stress, strain, and strain rate distribution between phases by describing the dynamic phase transformation during the deformation in iso-work conditions. Increasing the strain rate below the transformation temperature improves hot ductility by reducing dynamic recovery and strain concentration in ferrite. Due to limited grain boundary sliding, the hot ductility improves at lower temperatures (

Reliable microstructure characterization is essential for establishing process–microstructure–property links and effective quality control. Traditional manual microstructure analysis often struggles with objectivity, reproducibility, and scalability, particularly in complex materials. Machine learning methods offer a promising alternative but are hindered by the challenge of assigning an accurate and consistent ground truth, especially for complex microstructures. This paper introduces a methodology that uses correlative microscopy—combining light optical microscopy, scanning electron microscopy, and electron backscatter diffraction (EBSD)—to create objective, reproducible pixel-by-pixel annotations for ML training. In a semi-automated manner, EBSD-based annotations are employed to generate an objective ground truth mask for training a semantic segmentation model for quantifying simple light optical micrographs. The training masks are directly derived from raw EBSD data using modern deep learning methods. By using EBSD-based annotations, which incorporate crystallographic and misorientation data, the correctness and objectivity of the training mask creation can be assured. The final approach is capable of reproducibly and objectively differentiating bainite and martensite in optical micrographs of complex quenched steels. Through the reduction in the microstructural evaluation to light optical micrographs as the simplest and most widely used method, this way of quantifying microstructures is characterized by high efficiency as well as good scalability.

The usage of fossil fuels such as coal is now being reduced and shifted to bio-fuel in the boilers. It is because fossil fuels are exhaustible and generate CO2 emission during burning. Whereas, bio-fuels are abundantly available at low cost and also produce fewer greenhouse gases. However, burning of such fuels create a lot of corrosive species which can damage the components used for construction of boilers. Ferritic, austenitic, and martensitic steels are widely used to construct various parts of the boiler. Hence, in this study, four different grades of steels known as T91, SS304, SS316, and SS410 have been placed in the actual boiler environment for 493h. The boiler utilizes wood chips, rice husk, sawdust, bamboo base and leaf cuttings as burning fuel and operates at 850±50∘C. The results indicate that T91 steel showed a maximum rate of corrosion followed by SS304, SS316, and SS410. Martensitic steel 410 showed the minimum loss in weight among other steels. No intergranular corrosion was noticed in 410 steel, but the oxide so formed on the surface was fragile and porous although the chromium content is less in SS410 as compared to SS304 and SS316. [ABSTRACT FROM AUTHOR]

The thermodynamics of mass transfer during gaseous carburization and its overall efficiency across various alloyed steels were investigated to discern the influence of alloy content. Quantitative analyses were conducted on the coefficients of mass transfer and carbon diffusivities for EN3, EN35, 20MnCr5, and EN353 steels at a carburization temperature of 930 °C. The study revealed distinct trends in mass transfer dynamics and carbon diffusion rates among the different alloyed steels. For instance, nickel majorly an austenite stabilizer, was found to enhance carbon diffusion in gamma iron, with observed coefficients of mass transfer ranging from 8.85 x 10-6 to 1.87 x 10-5 cm/s. However, EN35 steel exhibited slower mass transfer rates due to weaker atomic interactions, resulting in lower observed coefficients of mass transfer. Conversely, chromium and molybdenum, known carbide-forming elements, facilitated carbon transfer from the gaseous environment to the steel case in 20MnCr5 and EN353 steels, with observed coefficients of mass transfer ranging from 1.39 x 10-5 to 1.55 x 10-5 cm/s. Additionally, the study compared observed carbon diffusivities with those predicted by DICTRA (Diffusion Controlled TRAnsformation) kinetic and thermodynamic datasets, demonstrating excellent consistency. These findings underscore the significance of considering alloy content in achieving consistent carburizing outcomes and suggest potential modifications to existing carburizing methods to improve diffusion depth homogeneity. Overall, the study provides valuable insights into the impact of alloy elements on the carburization process and offers implications for optimizing carburizing practices in alloy steel manufacturing. [ABSTRACT FROM AUTHOR]

Experiments were carried out to investigate the wetting behaviour of liquid tin on two different steel substrates EN1.4301 stainless steel and 42CrMo4 low-alloyed steel. The experiments were carried out in a vacuum furnace at residual pressure (10−8 bar) with the temperature raised till 1233 K (960 °C). The transition of the liquid tin droplet from a non-wetting to a wetting state was achieved on the surface of both steels after the spontaneous oxide removal. The transition temperatures in the Sn/EN1.4301 and Sn/42CrMo4 systems were nearly identical, 1140 K and 1130 K, respectively. SEM images showed the formation of the Fe–Sn intermetallic compounds at the Sn/steel interfaces above the transition temperature. Tin penetration into the grain boundaries of EN1.4301 and 42CrMo4 steels was also observed. [ABSTRACT FROM AUTHOR]

Research papers devoted to development of laser-plasma processes during the last two decades are reviewed. It was found that the current directions of scientific research of the processes of laser-plasma welding are focused mainly on studying the peculiarities of joint impact of constricted arc plasma and laser radiation with wave length of 1.03 -- 1.07 μm (first of all, fiber laser) on steels and alloys, as well as studying the physical fundamentals of manifestation of the synergic (hybrid) effect at such an impact and determination of the possibilities of its practical application. It was determined, in particular, that increase of the effectiveness of synergic effect manifestation is related to improvement of the plasma arc burning conditions in the zone of ionized vapour plume, which forms under the impact of focused laser radiation, as well as simplification of laser keyhole formation due to plasma arc pressure. [ABSTRACT FROM AUTHOR]

The steels from which the components of mining machinery are constructed must be based primarily on knowledge of their behaviour under environmental conditions and of the excavation technology. Secondly, the structural changes undergone by the materials due to mechanical and thermal processing and the stresses generated by the action of excavation forces that can induce internal stresses at a level that is difficult to determine must be taken into account. Determining the level of structural and mechanical degradation involves sampling the load-bearing structure elements of the excavation and storage machinery for analysis of the mechanical and chemical properties of the component materials. The paper focuses on issues related to the structural and mechanical degradation of steel as a material for parts of mining machinery. In this paper, a methodology for evaluating the degree of structural degradation of three types of bucket wheel excavators with different operating hours (ERc 1400-30/7-07 with 50,400 h, ERc 1400-30/7-08 with 69,264 h, and SRs 1300-26/3.5 with 112,000 h) is proposed. The methodology aims to provide a quantitative assessment of the structural degradation by considering the specific elastic limit of the material used in the machines and the number of hours of operation. This method uses a minimum set of destructive mechanical tests, such as tensile, resilience for three working temperatures, chemical analysis, and durometry on resistance elements taken from the machine, as well as the use of Weibull analysis. By combining this information with the number of hours of operation, a comprehensive evaluation can be made to determine the extent of degradation and potential maintenance requirements. The use of a minimum set of mechanical tests ensures an efficient and cost-effective approach to assessing the structural integrity of these machines. The metallographic analysis highlighted a predominant and defined form of grain rearrangement in the E14-07 machine after only 50,400 h. The constituents identified in the samples taken from the three machines are ferrite and pearlite. The highest hardness of the samples was recorded for the E14-08 machine, with values between 162–165 HV10. For bucket wheel excavators E14-07 and E14-08, the material structure showed elongated grains in the direction of deformation, compared to the material structure of E13-04, which has finely equiaxed grains. As a result of the research, final conclusions were formulated. [ABSTRACT FROM AUTHOR]

This study investigates the utilization of cyclic heat treatment (CHT), also referred to as thermal cycling, to design microstructures in steel to achieve specific properties. Through a comprehensive review of existing literature, it analyzes the influence of CHT on microstructure, strengthening mechanisms, and structure-property relationships, drawing parallels with conventional heat treatment methods. Mechanical properties are examined to establish meaningful correlations with structural modifications. The study delves into the impact of CHT parameters on microstructural changes and suggests to optimize these parameters to attain an ideal microstructure. While underscoring the potential advantages of CHT in enhancing steel's mechanical properties, it also conscientiously acknowledges its limitations, concluding with valuable recommendations for future research and practical implementation. [ABSTRACT FROM AUTHOR]

Model alloys, Fe–20Cr and Fe–20Cr–20Ni (wt%) with and without 1% Si, were exposed to four different gas mixtures Ar–10H2O, Ar–10H2O–0.1HCl, Ar–10H2O–0.1HCl–10CO2, Ar–10H2O–0.1HCl–10CO2–0.5SO2 (vol.%) at 650 °C. The Fe–20Cr and Fe–20Cr–20Ni alloys underwent breakaway corrosion in Ar–10H2O–(0.1HCl)–(10CO2), forming Cr2O3 and Fe-rich oxide nodules. Silicon addition markedly increased corrosion resistance for both alloys by forming an additional SiO2 layer beneath the Cr2O3 scale. Addition of SO2 to Ar–10H2O–0.1HCl–10CO2 significantly suppressed the formation of Fe-rich oxide nodules on Fe–20Cr. Corrosion in the SO2-bearing gas resulted in (Cr, Fe, S)-rich precipitates in all alloys. The effects of gas composition and Si alloying on corrosion of both alloys are discussed in terms of transport processes within the scales. [ABSTRACT FROM AUTHOR]

Research papers devoted to development of laser-plasma processes during the last two decades are reviewed. It was found that the current directions of scientific research of the processes of laser-plasma welding are focused mainly on studying the peculiarities of joint impact of constricted arc plasma and laser radiation with wave length of 1.03 – 1.07 μm (first of all, fiber laser) on steels and alloys, as well as studying the physical fundamentals of manifestation of the synergic (hybrid) effect at such an impact and determination of the possibilities of its practical application. It was determined, in particular, that increase of the effectiveness of synergic effect manifestation is related to improvement of the plasma arc burning conditions in the zone of ionized vapour plume, which forms under the impact of focused laser radiation, as well as simplification of laser keyhole formation due to plasma arc pressure. Ref. 49, Fig. 9. [ABSTRACT FROM AUTHOR]

The panels of high chromium steel (A1010), high-performance steel (HPS 70W) and weathering steel (WS) were exposed to accelerated salt-spray corrosion test for 1 week and to less aggressive test for additional 13 weeks. After the tests, the corrosion products formed were extracted layer after layer and examined as a function of their depth with Mössbauer transmission spectroscopy. In the case of A1010 steel, the amounts of goethite (α-FeOOH) and akaganéite (β-FeOOH) were almost equal along the depth of the corroded layer up to ∼20 μm. The rust layers on HPS and WS panels were much thicker, respectively up to ∼0.6 mm and ∼1 mm, poorly adherent and contained mostly akaganéite near the metal–rust interface, α-FeOOH increasingly further away, and – after long exposure – also up to 20% Fe as maghemite (γ-Fe2O3). Formation of β-FeOOH near the interface was promoted by chloride concentrated by spray-dry cycles. The microstructure and depth profiles of identified species, and especially the role of β-FeOOH, are discussed. [ABSTRACT FROM AUTHOR]

Laser-directed energy deposition (L-DED) is a key enabling technology for the repair of high-value aerospace components, as damaged regions can be removed and replaced with additively deposited material. While L-DED repair improves strength and fatigue performance compared to conventional subtractive techniques, mechanical performance can be limited by process-related defects. To assess the role of oxygen on defect formation, local and chamber-based shielding methods were applied in the repair of 300M high strength steel. Oxidation between layers for locally shielded specimens is confirmed to cause large gas pores which have deleterious effects on fatigue life. Such pores are eliminated for chamber shielded specimens, resulting in an increased ductility of ∼15%, compared to ∼11% with chamber shielding. Despite this, unmelted powder defects are not affected by oxygen content and are found in both chamber- and locally shielded samples, which still have negative consequences for fatigue. [ABSTRACT FROM AUTHOR]

Integrated computational materials engineering (ICME) is emerging as an increasingly powerful approach to integrate computational materials science tools into a holistic system and address the multiscale modeling challenges in the processing of advanced steels. This work aims at incorporating macroscopic model (finite element-based thermal model) and microscopic model (CALPHAD-based microstructure model), building an industry-oriented computational tool (MICAST) for casting of steels. Two case studies were performed for solidification simulations of tool steel and stainless steel by using the CALPHAD approach (Thermo-Calc package and CALPHAD database). The predicted microsegregation results agree with the measured ones. In addition, two case studies were performed for continuous casting and ingot casting with selected steel grades, mold geometries and process conditions. The temperature distributions and histories in continuous casting and ingot casting process of steels were calculated using in-house finite-element code which is integrated in MICAST. The predicted temperature history from the casting process simulation was exported as input data for the DICTRA simulation of solidification. The resulting microsegregation by the DICTRA simulation can reflect the microstructure evolution in the real casting process. Current computational practice demonstrates that CALPHAD-based material models can be directly linked with casting process models to predict location-specific microstructures for smart material processing. [ABSTRACT FROM AUTHOR]

The "electron wind effect" has long been cited as a potential catalyst of solid-state transformations in metals, particularly when high current densities are involved. However, the literature exploring similar effects at lower current densities, such as those occurring during Gleeble thermomechanical simulation, remains scarce. The present work compares recrystallization activity in cold-rolled low-carbon steel during heat treatment by conventional furnace versus direct resistance heating (Gleeble). Multiple levels of cold work, annealing durations, and soak temperatures were examined, allowing for an in-depth comparison of recrystallization rates and activation energies between samples subjected to identical time–temperature profiles in the furnace and Gleeble. In addition to the expected increase in recrystallization behavior with the increases in temperature and cold-reduction levels, the use of the Gleeble system as the heating method resulted in faster initial microstructural transformation than a conventional furnace. The variability in recrystallized fractions persisted until the microstructures had saturated to their nearly fully recrystallized levels, at which point the microhardness and electron backscatter diffraction (EBSD) revealed convergence to equivalent behavior irrespective of the heating method. Analysis of the recrystallization kinetics by fitting to a JMAK relationship reflected the increased transformation activity during Gleeble treatment, with the value of the kinetic exponent also indicating greater grain growth activity at higher temperature. [ABSTRACT FROM AUTHOR]