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In this paper, the fatigue damage degree of low-alloy structural steel is evaluated by using the attenuation characteristics of laser-induced surface acoustic wave (SAW) during propagation. Taking the typical structural steel material Q345 as an example, a cracks model of fatigue damage is established, and the finite element method is used to solve the model. The results showed that the attenuation coefficient of SAW can reflect the depth and density of fatigue cracks. The surface measurement experiments of specimens with stress cycles of 0, 50000, 100000, 150000, and 200,000 showed that with the increase of stress cycles, the attenuation coefficient of SAW increases as a whole, indicating that it is feasible to evaluate the fatigue damage degree based on the attenuation of SAW. A method of applying tensile stress to the material to improve the sensitivity of fatigue damage evaluation is proposed. The tensile stress is used to offset the horizontal amplitude of the SAW, keeping the fatigue cracks in an open state and increasing the attenuation coefficient of SAW. The attenuation coefficient measurement experiment shows that this method is feasible. [ABSTRACT FROM AUTHOR]

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The low alloy bainitic steel used in reactor pressure vessels deteriorates during thermal service while the macroscopic thermodynamic parameters that cause thermal aging remains unknown. In this work, a thermal aging restructuring scheme was proposed by step-up aging the steel from 350 °C to 490 °C, with a total duration of 7500 hours. Samples from varied thickness of the steel were characterized in terms of carbides evolution and Charpy impact toughness at 20 °C. The carbide size and its fraction were statistically analyzed showing partial coarsening and dissolution during aging, while the carbide fraction was found linearly correlated with the impact energy for the first time. The critical transition temperature parameter of the aging process was found to be 470 °C for the steel. The macroscopic thermodynamic parameters, including the thermal aging time and temperature, facilitate a comprehensive understanding of the material degradation mechanism and provide a basis for long-term safety of equipment. [ABSTRACT FROM AUTHOR]

With the development of 3D metal printers for rapid prototyping and industrial component production, heightened attention was directed towards post-processing operations for achieving precise surface quality and geometrical tolerances for these components. This paper investigated the orthogonal cutting of multi-material 3D printed workpieces using a coated cutting tool through finite element simulation. The workpieces featured different horizontal and vertical arrangements of layers composed of aluminum 7075-T6 alloy (Al), stainless steel 316 low alloy (SS), and Ti6Al4V alloy (Ti). The study explored the impacts of multi-material composition, coating thickness, and the rake angle of the cutting tool on machining forces, stress distribution, temperature distribution, and chip formation geometry. The results revealed a bimodal chip morphology in the machining process of horizontally arranged SS layers combined with other alloys. The SS layer resulted in a relatively uniform chip formation, while layers with two other materials exhibited a serrated chip formation. In contrast, a discontinuous chip formed when combining Al and Ti materials, as well as in the horizontally arranged layers made of Al, SS, and Ti alloys. The cutting force increased by 2.26 times when cutting workpieces with the horizontal arrangement of SS and Al layers compared to those with a single Al material. For the horizontal and vertical arrangement of layers made of Al and SS, von Mises stress values over the edge of the coated cutting tool significantly increased where the tool contacted the SS layer. Additionally, the horizontal arrangement of layers made of Al and SS materials caused the coated cutting tool to exhibit an extensive temperature distribution, with the maximum recorded temperature reaching 1448 °K. Increasing coating thickness led to a decrease in maximum principal stress at the surface of the tool and a rise in temperature at the cutting edge of the insert. [ABSTRACT FROM AUTHOR]

In the present work, the Q345B low-alloy steel with different contents and ER309L stainless steel were melted together to obtain new alloys. The aim was to design the composition of weld metal (Q345B low-alloy steel as the base material and ER309L welding wire as the filler material) and improve the corrosion resistance of the weld metal. During the welding process, the composition of the weld metal was controlled to match the new alloys by changing the welding heat input. A relationship curve between fusion ration and welding heat input was obtained. The research focused on analyzing the effect of mixed-smelting ratio between Q345B and ER309L and welding heat input on the microscopic structure and corrosion performance of the prepared samples. The results show that the melted alloys containing 20% to 30% Q345B consist of a ferrite (δ) phase and austenite (A) phase, the samples containing 45% to 50% Q345B consist of a martensite (M) phase and austenite (A) phase, and the sample containing 40% Q345B consists of a martensite (M) phase, ferrite (δ) phase, and austenite (A) phase. As the mixed-smelting ratio of Q345B/ER309L increased, the corrosion resistance of samples decreased gradually. For the weld metal, the fusion ration between Q345B base material and ER309L welding wire increases with the welding heat input. When the heat input changed from 0.645 kJ/mm to 2.860 kJ/mm, the composition of the weld metal was consistent with the melted alloys containing 20–45% Q345B. The microstructure and corrosion resistance of the weld metal could be designed by the melting means, which has important guiding significance for engineering applications. [ABSTRACT FROM AUTHOR]

The Chaudonneret model cannot fully and effectively characterize the linear correlation between the strain energy density release rate and the number of cycles in the damage evolution stage of low carbon alloy steels under multiaxial non-proportional loading. In order to solve this problem, the fatigue failure process of Q355B is captured by digital image correlation technology, and the factors affecting fatigue failure under multiaxial loading are analyzed in combination with fracture morphology characteristics. Based on the concept of critical plane, a new stress combination form is introduced to reflect the failure factors, and the corresponding damage evolution model is proposed. The model considers the interaction between different stresses and can describe the damage evolution law under non-proportional loading. Compared with different types of life prediction models, the distribution range of life prediction results of the improved model under multiaxial non-proportional loading has a good correlation with the experimental values. [ABSTRACT FROM AUTHOR]

In this paper, an interval type-2 radial basis function neural network system is presented that produces an accurate forecast of the temperature of liquid steel in a secondary metallurgical monitoring and control process. The main goal of this proposal is to get the precise temperatures and times to aggregate the additives to the liquid bath to produce high-strength, low-alloy steel and not waste materials due to the oxidation caused by high temperatures. Also, the proposal reduces the replacement times of measurement instruments that are damaged by the high temperatures. The novelty of this proposal is the lack of this class of neural networks in steelmaking processes and the fact that this is an emergent technology that has only been around for less than 10 years. The produced results show an error in order of 0.12% that is a figure well below 0.30% which is the typo error produced by the measurement devices such as thermocouples of the k-type that are damaged at 1600° and produce erroneous measurements in temperatures superior to 1200 °C and less than the classic interval type-2 fuzzy logic systems. [ABSTRACT FROM AUTHOR]

The influence of the centerline segregation region (CSR) on the hydrogen embrittlement (HE) of two different API 5L X80 pipeline steel plates was investigated. The novelty of this work was to establish relationships between the CSR, microstructure, and distribution of localized fragile particles on HE susceptibility and on fracture morphology. This work intended to establish a relationship between centerline segregation and HE susceptibility in high-strength low-alloy steels submitted to inhomogeneous transformations. Microscopy, hydrogen permeation, and slow strain rate (SSR) tests were used to investigate hydrogen-related degradation. The solution used on the charging cell of the permeation tests—and on the SSR test cell—was 0.5 mol L−1 H2SO4 + 10 mg L−1 As2O3, and in the oxidation cell, 0.1 M NaOH was used as a solution. The CSR led the thicker plate to present the highest HE index (0.612) in analyses carried out in the mid-thickness; however, the same plate showed the lowest HE index in near-surface tests. The presence of hydrogen changed the fracture morphology from ductile to a brittle and ductile feature; this occurred due to the interaction with localized fragile particles and the significant reduction of the shear stress necessary for the dislocation movement. [ABSTRACT FROM AUTHOR]

To ensure consistent performance of additively manufactured metal parts, it is advantageous to identify alloys that are robust to process variations. This paper investigates the effect of steel alloy composition on mechanical property robustness in laser-directed energy deposition (L-DED). In situ blending of ultra-high-strength low-alloy steel (UHSLA) and pure iron powders produced 10 compositions containing 10–100 wt% UHSLA. Samples were deposited using a novel configuration that enabled rapid collection of hardness data. The Vickers hardness sensitivity of each alloy was evaluated with respect to laser power and interlayer delay time. Yield strength (YS) and ultimate tensile strength (UTS) sensitivities of five select alloys were investigated in a subsequent experiment. Microstructure analysis revealed that cooling rate-driven phase fluctuations between lath martensite and upper bainite were a key factor leading to high hardness sensitivity. By keeping the UHSLA content ≤20% or ≥70%, the microstructure transformed primarily to ferrite or martensite, respectively, which generally corresponded to improved robustness. Above 70% UHSLA, the YS sensitivity remained low while the UTS sensitivity increased. This finding, coupled with the observation of auto-tempered martensite at lower cooling rates, may suggest a strong response of the work hardening capability to auto-tempering at higher alloy contents. This work demonstrates a methodology for incorporating robust design into the development of alloys for additive manufacturing. [ABSTRACT FROM AUTHOR]

In the present study, directional and spatial variations in the mechanical properties are calculated in two nuclear-grade materials. In practice, multiple ASTM standard specimens are tested to measure mechanical properties of any material. The variations obtained in the properties during the tests are generally neglected assuming such variations are due to experimental uncertainties. However, such variations may indicate some degree of anisotropy and spatial inhomogeneity in the material due to component fabrication. In the present study, multiple miniaturized tensile specimens are tested. These specimen materials are taken across the thickness and at different geometrical locations in the two manufactured nuclear-grade components. The experimental load versus displacement data of all the specimens are then used to evaluate stress-strain data and cohesive zone parameters. These parameters are determined for each tested specimen separately to gather variations over the geometries of the components. Subsequently, TPB specimens are analyzed employing these parameters to calculate variations in fracture initiation toughness over the geometry. The key findings of the present work include higher strengths in circumferential direction in comparison to the longitudinal direction for SA333 Gr6 steel. A new equation is developed to correlate the material toughness with the fracture toughness with a proportionality constant of 2.7778 for low-alloy carbon steels. The study showed that directional and spatial variations in Jini are less pronounced in 20MnMoNi55 compared to SA333Gr6 materials. This finding is crucial for safety analyses in nuclear components and indicates that this methodology can be applied more widely across different materials. [ABSTRACT FROM AUTHOR]

Demand for optimized high-strength, low-alloy steel used in sensor applications and as load elements is rising. Achieving strength through grain refinement while preserving toughness is both practical and sustainable. Severe plastic deformation, which is necessary for this effect, is not always feasible owing to constraints in manufacturing and product forms, such as welding or significant components. In this study, we explored grain refinement via cyclic heat treatment to circumvent these limitations, employing varied heating (medium-frequency heating and salt bath treatment), and cooling (water quenching, oil quenching, and air cooling) rates, and additional heat treatments. The process aimed at refining grains through repeated austenite to martensite transformations. The analysis covered microstructural impacts on mechanical properties and grain refinement efficiency. Comparatively, cyclic heat treatment enhanced tensile strength by 180 MPa and reduced grain size to 5.72 µm, outperforming quenching and tempering methods. Additionally, the efficacy of grain refinement improved with more cyclic heat treatment cycles. [ABSTRACT FROM AUTHOR]

One of the well‐known methods for correctly managing sludge disposal is using produced sludges as fuel in biogas‐burning power plants. This study employed the ReCiPe2016 life cycle assessment methodology in conjunction with SimaPro software to assess the environmental impacts of a biogas‐fired power plant in Tehran with a total capacity of 2.4 MW. The results were analyzed, and the 13 necessary pieces of information for the biogas burning system per 1 MWh produced heat and power by the combined heat and power unit were considered. In anaerobic digestion, heat and power in all classes had reducing effects on the environment. The heat and power classes, reinforced steel, chrome steel, low alloy steel, copper, and cast iron, exhibited the highest environmental impacts within the integrated heat and power system. Among all impact classes, power (for anaerobic digestion) in the class of carcinogenic toxicity in humans with a value of −6.01976 kg 1,4‐DCB and copper (for combined heat and power) in the marine environmental toxicity class with a value of 0.731434 kg 1,4‐DCB had the most reduction effect and the most impact of pollutant on the environment among the considered classes, respectively. Conclusively, in the anaerobic digestion process, heat and power had a positive effect on the environment in all impact classes. So, sludge can be an adequate candidate and anaerobic digestion can be an eco‐friendly method for power generation. Other effect classes are presented in detail as results. This study could guide the development of similar facilities globally, considering factors like wastewater volume and combined heat and power technology. [ABSTRACT FROM AUTHOR]

To achieve a balanced combination of high strength and high plasticity in high-strength low-alloy (HSLA) steel through a hot-rolling process, post-heat treatment is essential. The effects of post-roll air cooling and oil quenching and subsequent tempering treatment on the microstructure and mechanical properties of HSLA steels were investigated, and the relevant strengthening and toughening mechanisms were analyzed. The microstructure after hot rolling consists of fine martensite and/or bainite with a high density of internal dislocations and lattice defects. Grain boundary strengthening and dislocation strengthening are the main strengthening mechanisms. After tempering, the specimens' microstructures are dominated by tempered martensite, with fine carbides precipitated inside. The oil-quenched and tempered specimens exhibit tempering performance, with a yield strength (YS) of 1410.5 MPa, an ultimate tensile strength (UTS) of 1758.6 MPa, and an elongation of 15.02%, which realizes the optimization of the comprehensive performance of HSLA steel. [ABSTRACT FROM AUTHOR]

Herein, the interaction between hydrogen, microstructure, and mechanical properties in low-alloy high-strength marine steel was elucidated via microstructural characterization, internal friction analysis, hydrogen diffusion, and hydrogen-embrittlement sensitivity evaluation. Results indicated that the bainite structure of hot-rolled steel transformed into a coarse ferrite–pearlite structure after normalizing, and the hydrogen trap density decreased with decreasing grain boundary and dislocation densities. Therefore, the effective diffusion coefficient of hydrogen in the normalized steel plates increased with decreasing hydrogen permeation time. Owing to the coarsening of the microstructure, the normalized steel plates exhibited higher sensitivity to hydrogen embrittlement. The diffusion of a large amount of hydrogen into the steel considerably deteriorated its plasticity, resulting in a transition of its fracture mode from microvoid coalescence fracture to cleavage fracture. The internal friction behavior indicated that hydrogen in the microstructure generated a hydrogen-induced Snoek peak, as well as reduced the activation energy of Snoek–Kê–Köster and Kê peaks. Finally, the internal friction spectra revealed that the interaction between hydrogen and point defects, dislocations, grain boundaries, and precipitates was sequentially enhanced due to the increase in activation energy. [ABSTRACT FROM AUTHOR]

The adhesion of microorganisms and the subsequent formation of mineralized layers in biofilms are of great significance in inhibiting the corrosion of metal materials. In this work, we found that the adhesion and subsequent mineralization of Bacillus subtilis on the surface of low-alloy steel are influenced by the molybdenum in the material. The addition of molybdenum will lead to increased adhesion of B. subtilis on the material surface, and the subsequent biomineralization ability has also been improved. Through transcriptome and physiological and biochemical tests, we found that molybdenum can affect the chemotaxis, mobility and carbonic anhydrase secretion related genes of B. subtilis, and then affect the formation and mineralization of the biofilm of B. subtilis. [ABSTRACT FROM AUTHOR]

The influence of co-regulating Mo and Sn on the corrosion resistance of low alloy steel in tropical marine atmospheric was investigated. The combined addition of Mo and Sn has been found to significantly improve the corrosion resistance of low alloy steel, augmenting the protective capabilities of the rust layer. This combined addition promotes the formation of protective compounds like α-FeOOH and FeCr2O4 within the alloy rust layer. Furthermore, it facilitates the conversion of Cr, Ni and Cu into corrosion-resistant oxides such as Cr2O3, NiFe2O4 and CuO, thereby enhancing the density of the rust layer. Additionally, as corrosion progresses over time, higher levels of Sn addition lead to increased Sn content within the inner rust layer, consequently bolstering the protective qualities of the rust layer. This comprehensive understanding sheds light on the synergistic effects of Mo and Sn in fortifying the corrosion resistance of low alloy steel, offering insights for the development of advanced corrosion-resistant materials in marine environments. [ABSTRACT FROM AUTHOR]

Pipe steel 06Mn2MoNb is studied after hot rolling and subsequent heat treatment, i.e., austenitizing at 980°C, 30 min and cooling at different rates. By means of orientation microscopy and crystallographic analysis using various orientation relationships the possibility is demonstrated of creating structural and textural characteristics based upon transformation products (martensite, bainite) of deformed austenite within the steel. It is shown that the crystallographic texture resulting from a multivariant γ → α-transformation may be explained by α-phase generation at crystallographically ordered boundaries between deformed γ-phase grains. [ABSTRACT FROM AUTHOR]

The microstructure and impact toughness of high-strength low-alloy steels joined by friction stir welding are studied. The hardened steel samples are tempered at a temperature of 600–650°C for 1 hour, followed by warm rolling to a total strain of 1.5 at the same temperature. The resulting steels are characterized by an ultrafine-grained lamella-type microstructure. The as-processed steel plates are joined by friction stir welding. A martensitic microstructure is formed in the stir zone. The steel samples with a carbon content of 0.15% show high impact toughness of 68 J/cm2 at room temperature with a gradual decrease to 16 J/cm2 at a temperature of –196°C, while the steel samples with a carbon content of 0.36% exhibit an impact toughness of 10 J/cm2 at room temperature. The 0.36% carbon steel joints are tempered at a temperature of 650°C for 1 hour, which increases their room-temperature impact toughness to 67 J/cm2. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) technologies have demonstrated a promising material efficiency potential in comparison to traditional material removal processes. A new directed energy deposition (DED) category AM process called wire arc additive manufacturing (WAAM) is evolving due to its benefits which include faster build rates, capacity to build large volumes, and inexpensive feedstock materials and machine tools compared to more technologically mature powder-based AM technologies. However, WAAM products present challenges like poor surface finish and lower dimensional accuracy compared to powder-based processes or machined parts, prevalence of thermal distortions, residual stresses, and defects like porosity, cracks, and humping, often requiring post-processing operations like finish machining and heat treatment. These post-processing operations add to the production cost and environmental footprint of WAAM-built parts. Therefore, considering the opportunities and challenges presented by WAAM, this paper analyses the environmental impact, production costs, and mechanical properties of WAAM parts and compares them with those achieved by laser powder bed fusion (LPBF) and traditional computer numerical control (CNC) milling. A high-strength low-alloy steel (ER70S) mechanical part with medium complexity was fabricated using WAAM. Based on the data collected during this experiment, environmental impact and cost models were built using life cycle assessment and life cycle costing methodologies. WAAM was observed to be the most environmentally friendly option due to its superior material efficacy than CNC milling and has a better energy efficiency than LPBF. Also, WAAM was the most cost-friendly option when adopted in batch production for batch sizes above 3. The environmental and cost potential of WAAM is amplified when used for manufacturing large products, resulting in significant material, emission, and cost savings. The fabricated WAAM part demonstrated good mechanical properties comparable to that of cast/forged material. The methodology and experimental data presented in this study can be used to calculate environmental impacts and costs for other products and can be helpful to manufacturers in selecting the most ecofriendly and cost-efficient manufacturing process. [ABSTRACT FROM AUTHOR]

Solid-to-solid diffusion bond between ferritic SA508 low alloy steel (LAS) and austenitic 316L stainless steel (SS) via hot isostatic pressing (HIP) was evaluated. This study investigated the microstructural and mechanical evolutions of the bimetallic interface before and after heat treatment. The interfacial region between two materials demonstrated uniform microstructure, no visible manufacturing defects, and higher interfacial hardness and tensile strength. The joint interface was stronger than for both 316L SS and SA508 LAS. The interfacial hardening was attributed to the significant grain refinement at the interface region and dislocation hardening under as-HIP'ed condition. Post-HIP heat treatment considerably reduced the interfacial strength, attributed to dislocation recovery and grain growth. From the mechanical perspective, the work confirmed utilizing HIP capsules during HIP manufacturing provides adequate interfacial strength between 316L SS HIP capsule and SA508 LAS for cladding purposes. The 316L SS HIP capsule may be used as the cladding layer for corrosion protection. [ABSTRACT FROM AUTHOR]

Nickel-based, high-temperature alloy GH3536 and high-strength low-alloy steel HY130 samples were prepared by the laser melting deposition method. The high-temperature tensile properties of the as-manufactured GH3536 and the corrosion resistance of the as-manufactured HY130 were highlighted. The physical properties, mechanical properties, and microstructure of the two materials under laser additive manufacturing were analyzed and compared. The effects of different printing parameters on the mechanical and corrosion properties were also explored. It was found that GH3536 maintained high toughness in high-temperature tensile tests at 500°C and 815°C, with elongation reaching 74.45% and 60.48%, respectively, and tensile strength reaching 762 MPa at room temperature. Optical microscopy and SEM showed that thermal cracks were generated in the GH3536 during the printing process, reducing the strength. Combining XRD and EDS analysis demonstrated that GH3536 samples have a face-centered cubic structure, while HY130 is mainly α-Fe phase. HY130 has the best corrosion resistance and strength at low laser power (1000 W). These findings provide a valuable reference for further optimization of the properties of both materials in the laser additive manufacturing process. [ABSTRACT FROM AUTHOR]

Overcoming the trade-off relationship between strength and ductility has always been a challenge. In this article, a neatly arranged ultrafine bainite that is composed of multi-scale retained austenite was obtained by introducing weak chemical heterogeneity in low-alloy steel. The optimized microstructure makes transformation-induced plasticity (TRIP) behavior and coordinating deformation behavior between each phase to be smoother. This results in better comprehensive properties, with 28.5% and 9% increases in uniform elongation and toughness, respectively, and a similar strength. This study provides a new way to improve the properties of low-alloy steels. A strategy of weak chemical heterogeneity has been proposed in low-alloy steel, which effectively optimizes the microstructure and enhances the plasticity and toughness of steel. [ABSTRACT FROM AUTHOR]

The hot deformation behaviour of a Cu containing high strength low alloy (HSLA) steel has been evaluated by carrying out hot compression tests over a temperature range of 900 °C to 1100 °C and constant true strain rates of 0.0003 to 1 s−1. Although single peak flow curve is observed predominantly, a tendency to exhibit multiple peaks at low strain rates (0.0003 and/or 0.001 s−1) at temperature greater than 950 °C. The important parameters pertaining to dynamic recrystallisation (DRX), such as critical, peak, steady state stress and strain were ascertained, and the DRX state diagram depicting the variation of critical parameters governing DRX with Zener-Hollomon parameter Z was established. The volume fraction of recrystallised grains, computed from flow stress, as expected, follows a sigmoidal trend indicating higher kinetics at low strain rates for a given temperature. Reconstruction of prior austenite grain boundaries (PAGB) based on electron back scattered diffraction (EBSD) technique for a few select specimens clearly elucidated the effect of temperature and strain rate on the DRX behaviour of the steel. The DRX state diagram established here clearly demarcates the deformation space i.e. temperature-strain rate-stain space into regimes where the material exhibits full DRX, hardening/softening + DRX and only hardening (no DRX) behaviour. This would be useful for designing suitable forging sequence to achieve the desired microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

In this study, a new method for welding an API 5L X65 steel pipe that is internally clad with Alloy 625 cladding using Alloy 22 and AWS ER100S-G steel was developed. The first and second weld passes were made using Alloy 22 to provide excellent corrosion resistance for the Alloy 625 cladding region. The remaining weld passes were made using 100S-G steel to provide high mechanical strength. The welded joints were evaluated for their microstructure and mechanical properties. No significant solidification defects were found in the welded joints, as confirmed by bending and transverse tensile tests. The yield strength of the welded joint showed that welding was capable of delivering the necessary strength compatible with API 5L X65, X70, and X80 steels for subsequent installation using the reel lay process. The microstructure of the welded joint was complex, with the first two weld passes having a soft Ni-fcc matrix composed mainly of Alloy 22, while the first three 100S-G steel weld passes had a hard martensite matrix. The main region of the welded joint had a soft acicular ferritic matrix. Impact toughness testing showed that the energy absorbed by the notch positioned at the first steel weld pass was better than that for the notch positioned at the steel weld pass without a dilution effect for Alloy 22 (approximately 46 J and 14 J, respectively). The toughness of the weld pass increased due to the high Ni incorporation by dilution with Alloy 22, even at − 15 °C, while the steel weld passes that were not affected by dilution with Alloy 22 exhibited very low energy absorption, which is characteristic of steel materials assessed under conditions below the ductile-to-brittle transition temperature (DBTT). The fracture toughness tests confirmed this result, as the major steel weld passes exhibited brittle features that caused abrupt failure during the test at − 15 °C. [ABSTRACT FROM AUTHOR]

In the present study, the glass slurry coating to a high-strength low-alloy steel (HSLA) substrate was investigated for corrosion resistance material. The crystallographic phases, degree of crystallinity, lattice parameters, and potential changes due to the coating process, and microstructural changes such as visual inspection of the surface, revealing thickness, uniformity, adhesion, potential defects, and elemental composition of the bare and coated steel were investigated by using the X-ray diffraction (XRD) and scanning electron microscopy and electron dispersive spectroscopy (SEM/EDS). The electrochemical behavior of the bare and coated steel samples was compared using potentiodynamic polarization and electrochemical impedance spectroscopy at various immersion periods in a 3.5 wt.% of sodium chloride (NaCl) solution. The higher corrosion resistance and lower corrosion rates of the coated steel surfaces were observed. The protection effectiveness of coatings is evaluated by examining their impedance and polarization characteristics. The effectiveness of the glass coatings in inhibiting corrosion is attributed to their role as a physical barrier and their ability to release corrosion inhibitors into the surrounding electrolyte. This information can be crucial for real-world applications requiring corrosion resistance. [ABSTRACT FROM AUTHOR]

This study investigates the effect of changing the chemical composition during ultrasonic atomization (UA) and laser powder bed fusion (LPBF) of low‐alloy steel. UA is used to produce a spherical powder with d50 equal to 49 μm. During UA, the chemical composition of the material changes, which is associated with selective evaporation of Mn from 1.42% to 0.35% and B from 0.0012% to <0.0001%. Thermodynamic calculations confirm that during atomization, mostly Mn and Fe evaporate. To achieve a high density of 3D printed parts, in situ remelting in LPBF is applied. A microstructure consisting of fine grains of tempered martensite and bainite in crystallized meltpools is observed. The selected high‐quality LPBF samples are austenitized in the temperature range of 900–1200 °C for 20 min and quenched in oil. The samples are characterized by light and scanning electron microscopy, as well as Vickers hardness. Changes in chemical composition result in a decrease in the hardenability of the material, and quenching only at 1200 °C produces a martensitic microstructure. LPBF samples show a hardness higher than that of the postheat‐treated sample, but still significantly lower than that of the as‐delivery condition, which is related to the change in chemical composition. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage could provide buffer capacity to store the excess energy from renewable resources. A lined rock cavern (LRC) is one of the hydrogen geologic storage site options. It offers great flexibility because it does not rely on the existence of salt caverns, aquifer formations or depleted hydrocarbon reservoir fields. However, many important aspects have to be investigated before its full-scale implementation, among them (1) the effect of spatial variation of rock mass properties and (2) hydrogen embrittlement on the steel lining. We present a numerical study on these two aspects by simulating field tests at a pilot LRC project. For the effect of rock heterogeneity, we assign a spatial variation of elastic properties based on the Gaussian covariance model. The results show a good agreement with the field measurements. The spatial correlation length of rock mass elastic properties only has a minor impact on the cavern surface deformation. Regarding hydrogen embrittlement, our simulations predict a significant hydrogen diffusion in the low alloy steel (S355) lining after ∼2 months of operation. The fracture simulations show little fracture propagation even after 10 years of contact with hydrogen gas. However, the product loss may be too high for the low alloy steel (S355). We would recommend the use of stainless steel to inhibit the hydrogen diffusion. We show that advanced numerical models are powerful tools to ensure the safety of hydrogen storage in LRCs. • The finite element simulation results show a good agreement with the field measurements of rock displacement. • The spatial correlation length of rock mass elastic properties only has a minor impact on the cavern surface deformation. • We would recommend the use of stainless steel as the liner material to inhibit the hydrogen diffusion. [ABSTRACT FROM AUTHOR]

High strength low alloy steels which are having excellent corrosion-resistant properties are called corten steels. In the present investigation, 3 mm thick ASTM A242 Corten steel sheets were welded together using the cold metal transfer (CMT) method based on two welding controllable parameters like welding current and welding speed. The controllable input parameters like welding current and welding speed have been altered to produce joints that have no flaws and a complete depth of weld penetration. The evaluation of the microstructure and weld geometry was performed for the cold metal transfer welded ASTM A242 sheets using ER70S6 filler wire. The experimental design of welding parameters was developed using an orthogonal array of full factorial design. The dominance of acicular ferrite microstructure is visible in the fusion zone. Results from Energy Dispersive x-Ray Analysis (EDAX) show that manganese content is higher and nickel concentration is lower in the weld fusion region. The fusion zone of the CMT welded specimen has the greatest hardness, which was measured at 270.2 HV. Due to the formation of acicular and bainite microstructure in the welding seam, the tensile properties at room temperature (RT) were found to be 589.79 and 405.63 MPa, accordingly. Bend tests additionally confirmed the satisfactory ductility of the welded joint. [ABSTRACT FROM AUTHOR]

The welding thermal simulation experiment of Q1100 low alloy high-strength steel was conducted using high-temperature laser scanning confocal microscope(HT-LSCM) and Gleeble-3500 thermal simulation tester with different welding heat inputs. In situ observation showed that prior austenite grains merged and grew instantly when the temperature reached the peak temperature, and then continued to migrate and grow during the subsequent cooling process. The prior austenite grain sizes and the CGHAZ microstructure were similar for the different welding heat inputs between high-temperature laser scanning confocal microscope and Gleeble-3500 thermal simulation. The microstructure consisted of granular bainite and proeutectoid ferrite, and a small amount of martensite/austenite (M–A) constituents when at t8/5 of 300 s. With increasing cooling rate, the microstructure transformed into lath bainite and lath martensite. When t8/5 was reduced to 15 s, the microstructure became lath martensite. Microhardness increased gradually as the welding heat inputs decreased, and impact toughness first increased and then decreased. By in situ observation of the microstructure and impact toughness testing, it is feasible to rapidly determine appropriate welding parameters and evaluate the weldability of materials. [ABSTRACT FROM AUTHOR]

Using scanning tunneling microscopy, it is shown that a lath structure is formed in the heat-affected zone of the low-carbon, low-alloy 09G2S steel after electric arc surfacing. Analysis of the results of scanning tunneling microscopy revealed a number of subtle morphological features of the lath structure, which makes it possible to explain the mechanism of its formation and identify it as lower bainite. The lower bainite structure in the heat-affected zone of the base metal of the 09G2S steel is favourable for increasing the impact strength of the coating – base metal composition, which was established earlier in our work. [ABSTRACT FROM AUTHOR]

The X100 pipeline steel is classified as a type of high-strength, low-alloy steel that is mostly used in the construction of pipelines designed for the extensive transit of natural gas and oil. Although X100 steel has exceptional mechanical qualities, it is vulnerable to stress corrosion cracking (SCC) when exposed to specific environmental conditions. Stress corrosion cracking has the potential to induce the development of minute fissures on the steel surface, which then propagate throughout the material, ultimately resulting in structural failure. The microstructure and electro-corrosion phenomena were investigated by the utilization of scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and polarization curves. Additionally, the susceptibility to stress corrosion cracking was assessed by analyzing the mechanical properties and cross-sectional characteristics utilizing interrupted slow strain rate testing (SSRT) techniques. Upon examining X100 steel, the granular bainite structure of the ferrite and martensite–austenite (M–A) components was observed. Overall, the average corrosion rates were 7.57 mpy. The main cracks occurred laterally and perpendicular to the direction of applied tension, whereas secondary cracks occurred almost to the point of cross-sectional fracture, demonstrating X100 susceptibility to SCC in NS4 solution. [ABSTRACT FROM AUTHOR]

Nowadays, low alloy steels effectively contribute to the manufacture of several important products, thus welding these types of steel is of great importance. Two different common welding processes, namely SMAW and OAW using two different fillers (E6013 electrode and A5.2 RG45 wire respectively) were employed to join 6 mm thick AISI 5160 low alloy steel plates. Compared to SMAW, the OAW process resulted in much wider HAZ. Microscopy of both welds revealed that the structure of the weld metal was generally ferrite and pearlite, while that of the unaffected base metal was predominantly pearlite. The structure in the fusion zone and CGHAZ of the oxy-acetylene weld was coarser than that of the SMA weld. Nevertheless, the hardness values across the oxy-acetylene weld were generally lower than those found across the SMA weld. The highest hardness across both welds was in the CGHAZ, while the lowest was in the inter-critical HAZ, and the average hardness in the weld center was lower than that of the base metal. Finally, the average tensile strength value of the SMA weld was much higher than that of the oxyacetylene weld, where fractography observation revealed porosity and an oxide layer, and the fracture was brittle. [ABSTRACT FROM AUTHOR]

The unexpected scaling phenomena have resulted in significant damages to the oil and gas industries, leading to issues such as heat exchanger failures and pipeline clogging. It is of practical and fundamental importance to understand the scaling mechanisms and develop efficient anti-scaling strategies. However, the underlying surface interaction mechanisms of scalants (e.g., calcite) with various substrates are still not fully understood. In this work, the colloidal probe atomic force microscopy (AFM) technique has been applied to directly quantify the surface forces between calcite particles and different metallic substrates, including carbon steel (CR1018), low alloy steel (4140), stainless steel (SS304) and tungsten carbide, under different water chemistries (i.e., salinity and pH). Measured force profiles revealed that the attractive van der Waals (VDW) interaction contributed to the attachment of the calcium carbonate particles on substrate surfaces, while the repulsive electric double layer (EDL) interactions could inhibit the attachment behaviors. High salinity and acidic pH conditions of aqueous solutions could weaken the EDL repulsion and promote the attachment behavior. The adhesion of calcite particles with CR1018 and 4140 substrates was much stronger than that with SS304 and tungsten carbide substrates. The bulk scaling tests in aqueous solutions from an industrial oil production process showed that much more severe scaling behaviors of calcite was detected on CR1018 and 4140 than those on SS304 and tungsten carbide, which agreed with surface force measurement results. Besides, high salinity and acidic pH can significantly enhance the scaling phenomena. This work provides fundamental insights into the scaling mechanisms of calcite at the nanoscale with practical implications for the selection of suitable antiscaling materials in petroleum industries. [ABSTRACT FROM AUTHOR]

This study aimed to determine the nucleation mechanism, particle shape, and strengthening behavior of (Ti, Nb) (C, N) particles in Fe-based composite coatings. In this study, an in-situ technique combined with a plasma spray welding process was proposed to obtain a coating with in-situ (Ti, Nb) (C, N) particles. Composite coatings were successfully prepared on low-alloy steel by plasma spray welding using a mixture of Fe-based, Ti and Nb powders. N gas was used to provide the N atoms. The microstructural analysis results indicated that the reinforced particles transformed from irregular dendritic into massive and spherical particles, and then into spherical and lath particles, as the atomic ratio of Ti/Nb decreased. During solidification, TiN nucleated preferentially and Ti (C, N) particles were formed sequentially. Subsequently, NbC nucleated and grew with Ti (C, N) as its core, and (Ti, Nb) (C, N) particles were formed at the end. The microhardness values of these composite coatings were 680–970 HV, whereas that of low-alloy steel was 174 HV. The wear resistance of the composite coatings increased as the Ti/Nb atomic ratio decreased. The composite coating had the highest average microhardness and the best wear resistance when Ti/Nb = 1:3. Its average microhardness was five times more than that of the low-alloy steel. In addition, the mass loss of the composite coating was 0.4 mg, which is only one-sixth that of the low-alloy steel (2.4 mg). The main reason for this was the in-situ formation of (Ti, Nb) (C, N) particles, which were evenly distributed in the composite coatings. • The nucleation mechanism, particle shape, and strengthening behavior of the (Ti, Nb) (C, N) particles were investigated. • The problem of the uneven distribution of TiC or TiN in coatings was solved. • A reliable coating preparation method with a stable effect is provided. [ABSTRACT FROM AUTHOR]

Powder metallurgy–hot isostatic pressing (PM-HIP) is a form of advanced manufacturing that offers the ability to produce near-net shape components that are otherwise not achievable via conventional forging or wrought manufacturing. Accessing the design space of PM-HIP is dependent upon the ability to achieve uniform or known properties in finalized components, which has resulted in a number of programs aimed at identifying properties achievable via PM-HIP manufacturing. One result of these programs has been the consistent observation of a variation in toughness observed for the low-alloy steel ASTM A508 Grades 3 and 4N. While observed, the degree of variability and the mechanism resulting in the variability have not yet been fully defined. Thus, a systematic approach to evaluate the variation observed in impact toughness in PM-HIP ASTM A508 Grade 4N was proposed to elucidate the responsible metallurgical mechanism. Four unique billets manufactured from two heats of powder with different particle size distributions (PSDs) were fabricated and tested for impact toughness and tensile properties. The degradation in impact toughness was confirmed to be location-specific where the near-can region of all billets had reduced impact toughness relative to the interior of each billet. The mechanism driving the location-specific property development was identified to be mobile oxygen that follows the thermal gradient that develops during the HIP cycle and leads to a redistribution of mobile oxygen where oxygen is concentrated ~1" inboard of the original canister/billet interface. Redistributed oxygen then forms stable oxides along coincident prior particle and prior austenite grain boundaries, effectively reducing the impact toughness. With the mechanism now addressed, necessary actions can be taken to mitigate the effect of the oxygen redistribution, allowing for use in PM-HIP A508 Grade 4N in commercial industry. [ABSTRACT FROM AUTHOR]

The machinability of steel is a crucial factor in manufacturing, influencing tool life, cutting forces, surface finish, and production costs. Traditional machinability assessments are labor-intensive and costly. This study presents a novel methodology to rapidly determine steel machinability using spark testing and convolutional neural networks (CNNs). We evaluated 45 steel samples, including various low-alloy and high-alloy steels, with most samples being calcium steels known for their superior machinability. Grinding experiments were conducted using a CNC machine with a ceramic grinding wheel under controlled conditions to ensure a constant cutting force. Spark images captured during grinding were analyzed using CNN models with the ResNet18 architecture to predict V15 values, which were measured using the standard ISO 3685 test. Our results demonstrate that the created prediction models achieved a mean absolute percentage error (MAPE) of 12.88%. While some samples exhibited high MAPE values, the method overall provided accurate machinability predictions. Compared to the standard ISO test, which takes several hours to complete, our method is significantly faster, taking only a few minutes. This study highlights the potential for a cost-effective and time-efficient alternative testing method, thereby supporting improved manufacturing processes. [ABSTRACT FROM AUTHOR]

The corrosion behaviors of three bridge steels in a real tropical marine environment for 2 years were studied. One weathering steel (WS) was designed with higher levels of nickel, copper, and molybdenum compared to the other. These two kinds of WSs and one kind of ordinary high-strength low-alloy steel (Q345qe) were compared under two conditions (marine atmospheric zone and marine immersion zone at Sanya Marine Environmental Test Station). The morphology, corrosion rate, and corrosion product analysis of the steels were performed through SEM, XPS, FTIR and other characterization methods. The results demonstrated that weathering steels facilitate the densification of the corrosion product layer due to the addition of alloying elements Cr, Ni, and Cu, promoting rust nucleation and enhancing the compactness of the protective layer. However, in an immersion environment, the extensive erosion by chloride ions renders the benefits of WS ineffective. [ABSTRACT FROM AUTHOR]

This study investigated the effects of partially replacing expensive Mo with cheaper Nb on the microstructure and properties of high-strength low-alloy (HSLA) steel during reverse austenisation. The mechanical properties of the steel in the hot-rolled state were lower with a partial replacement of Mo by Nb. However, after pre-tempering and reheating and quenching, the strength increased greatly while the ductility and toughness did not decrease much. Thus, the negative effects of replacing Mo with Nb were mostly alleviated, and a good balance between strength, ductility and toughness was achieved. After heat treatment, the mass percentage of precipitates increased substantially, which helped to pin grain boundaries during austenisation. The percent of high-angle grain boundaries greatly increased while the average effective grain size decreased, which improved grain refinement. The results showed that combining a partial replacement of Mo by Nb with heat treatment allows the microstructure and mechanical properties of HSLA steel to be effectively controlled while improving the balance between cost and performance. These findings provide valuable insights into the preparation and design of steels with similar microstructures. [ABSTRACT FROM AUTHOR]

Long-term steel reinforcement corrosion greatly impacts reinforced concrete structures, particularly in marine and coastal settings. Concrete failure leads to human casualties, requiring extensive demolition and maintenance, which represents an inefficient use of energy and resources. This study utilizes microscopic observation, atomic force microscopy (SKPM), electrochemical experiments, and XPS analysis to investigate the corrosion behavior of 500CE and 500E under identical conditions. We compared 500E with 500CE, supplemented with 0.94% Cr, 0.46% Mo, 0.37% Ni, and 0.51% Cu through alloying element regulation to obtain a finer ferrite grain and lower pearlitic content. The results indicate that 500CE maintains a stable potential, whereas 500E exhibits larger grain sizes and significant surface potential fluctuations, which may predispose it to corrosion. In addition, despite its more uniform microstructure and stable electrochemical activity, 500E shows inferior corrosion resistance under prolonged exposure. The electrochemical corrosion rate of 500CE in both the pristine and passivated states and for various passivation durations is slower than that of 500E, indicating superior corrosion performance. Notably, there is a significant increase in the corrosion rate of 500E after 144 h of exposure. This study provides valuable insights into the chloride corrosion phenomena of low-alloy corrosion-resistant steel reinforcement in service, potentially enhancing the longevity of reinforced concrete structures. [ABSTRACT FROM AUTHOR]

With the addition of microalloy elements to a high-strength low-alloy (HSLA) steel, various fine particles of carbides and nitrides are formed, which increase the matrix strength. These precipitates play a crucial role in precipitation strengthening. However, the role of precipitates in microstructural refinement is frequently overlooked. In this study, a series of hot-rolled HSLA steel samples were reheated to different temperatures above the austenite transformation point for a specified period to refine austenite grains via precipitation, then cooled to a dual-phase (austenitic/ferritic) region, and finally air-cooled to room temperature. The influences of different austenitising conditions on the microstructure and mechanical properties of the HSLA steel were examined. When a hot-rolled sample was reheated to 15 °C above the austenitic transition temperature for 20 min and then cooled to 25 °C below the austenitic transition temperature for 25 min, the most low-angle boundaries were formed, and the smallest effective grain size was achieved. Meanwhile, compared with the hot-rolled sample, the tensile and yield strengths of the reheated sample increased by 12.3% and 3.4%, respectively, while the elongation increased by 162.5%, exhibiting a good strength–ductility balance. By adopting an appropriate austenitising process, precipitates can refine the crystalline grains during austenitisation, thereby enhancing the comprehensive mechanical properties of the steel. Meanwhile, excessively high austenitising temperatures lead to the coarsening of the steel microstructure, decreasing the microstructural refinement efficiency via precipitation and consequently degrading the comprehensive mechanical properties of the steel. The findings provide valuable insights into the preparation process design of such steels or other steels with similar microstructures. [ABSTRACT FROM AUTHOR]

In view of the corrosion of steel strusture surface and its supporting strusture in an ambient water solution, the crack corrosion experiment, soaking experiment and electrochemical experiment of low alloy steel have been studied in the simulated aqueous solution. The corrosion morphology, corrosion product composition and electrochemical parameters of low alloy steel seamlss sample and crack sample in simulated aqueous solution have been analyzed. The results show that the corrosion of low alloy steel is mainly electrochemical reaction in the simulated aqueous solution. The initial corrosion products of rust layer are Fe(OH)3 and FeOOH products while the corrosion products in middle and later period are Fe3O4. The corrosion of crack sample is weaker than that of seamless sample, and the corrosion in the crack is much weaker than the corrosion outside the crack. Therefore, low alloy steel is not sensitive to crack corrosion in the simulated aqueous solution. [ABSTRACT FROM AUTHOR]

AISI 4340 is a medium-carbon low-alloy steel that has gained distinctive attention due to its advanced properties including high strength, high toughness, and heat resistance. This has led to its commercial usage in a wide variety of industries such as construction, automotive, and aerospace. AISI 4340 is usually machined in a hardened state through a hard-turning process, which results in high heat generation, accelerated tool wear, low productivity, and poor surface quality. The application of high-speed machining helps improve the material removal rate and surface finish quality, yet the elevated temperature at the cutting zone still poses problems to the tool's lifespan. Apart from using advanced cutting tool materials, which is costly, researchers have also explored various cooling methods to tackle the heat problem. This paper presents a review of a sustainable cooling method known as minimum quantity lubrication (MQL) for its application in the high-speed turning of AISI 4340 steel. This study is centered on high-speed turning and the application of MQL systems in machining AISI 4340 steel. It has been observed that the hard part turning of materials with a hardness exceeding 45 HRC offers advantages such as improved accuracy and tighter tolerances compared to traditional grinding methods. However, this process leads to increased temperatures, and MQL proves to be a viable alternative to dry conditions. Challenges in optimizing MQL performance include fluid penetration and lubrication effectiveness. [ABSTRACT FROM AUTHOR]

HRB500E rebar is a low-alloy high-strength steel with excellent mechanical properties and good plasticity but suffers from deficient corrosion resistance. This can be solved by adding trace elements, including rare earth elements. Herein, the corrosion-resistant behavior of rebar was evaluated by weightlessness testing and electrochemical measurements, and the effects of Ce on the structural evolution of the corrosion product layer were investigated by scanning electron microscopy (SEM), Electron Probe X-ray Micro-Analyzer (EPMA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that adding Ce to the rebar improved the densification of the reinforcing surface corrosion products, as well as reduced the corrosion rate of the experimental rebar. Compared to C0 sample without Ce, the rebar sample containing 0.044 wt.% Ce displayed increased Ecorr by 0.051 V, decreased Icorr by 15.573 mA cm−2, enhanced Rc of the corrosion product layer by 112.71 Ω cm2, incremented α-FeOOH content in the corrosion product layer, and boosted ratio of α/γ* in the corrosion product layer by 10.11%. Furthermore, the oxide (CeO2) formed by Ce in the corrosion layer of the rebar bar surface existed in the rust layer, resulting in a stable corrosion product layer with improved blocking ability of the corrosive medium. Overall, the addition of Ce at certain ratios looks promising to produce HRB500E rebar with excellent corrosion resistance and extended service life under harsh conditions. [ABSTRACT FROM AUTHOR]

Gas tungsten arc welding was used to produce an aluminum clad metal (CM) on SCM440 steel, and the effect of GTAW heat input on the properties of the CM on the steel surface was investigated. Experimental results concluded that increasing the GTAW heat input increased the width and penetration but decreased the reinforcement height of the CM. Furthermore, increasing the heat input increased the dendrite arm width and spacing and decreased the aluminum content in the CM, resulting in a decrease in CM hardness. Microstructure examination revealed no defects or brittle intermetallic compound formation at any location of the CM and the interface between the CM and the heat-affected zone. [ABSTRACT FROM AUTHOR]

Improving long-term stability is an important issue for large-scale applications of laser-induced breakdown spectroscopy (LIBS). Unlike laboratory instruments, many applications of LIBS instruments are in harsh outdoor environments, where instrument drift can lead to deterioration of long-term stability, hindering the use of LIBS technology in applications with high-precision requirements. In this work, based on the designed LIBS sensor for molten steel, we analyzed the spectral drift problem of different day measurements, on the basis of which we proposed a drift correction method combining the internal standard and the dominant factor partial least squares (PLS) regression. In this method, spectra are first preprocessed to build an internal standard model of the elemental concentration ratios to spectral line intensity ratios. Then the PLS regression is utilized to construct a corrected model between the spectral intensity and the drift value of the intensity ratio. Finally, elemental concentration predictions are made by using the established internal standard model with modified spectral line intensity ratios. The method was tested on low alloy steel samples. In the experiment, the detection spectra were recorded for 9 days for quantitative analysis and drift correction of the major elements C, Si, Cr, Ni, Cu, and Mn in alloy steels. Compared with the uncalibrated internal standard method, for the prediction of unknown samples over a long period of time, the RMSE values of C, Si, Cr, Ni, Cu, and Mn decreased by 48.74%, 50.00%, 73.30%, 72.15%, 72.57%, and 18.23%, respectively, and the RSD decreased by 27.71%, 42.97%, 35.17%, 38.95%, 55.58%, and 23.40%, respectively. Furthermore, several typical drift correction methods were also studied for comparison, and the proposed method achieved the best results for different test sets. [ABSTRACT FROM AUTHOR]