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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

AbstractIn 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]

The recrystallization behavior of ferrite single phase in ultrahigh‐strength low‐alloy (UHSLA) steels, with different titanium concentrations (1000, 1500, and 2000 ppm) is presented. Utilizing detailed dilatometer tests, we identified disparities between the observed austenite onset temperatures and those predicted using the JMatPro 13 program and ThermoCalc. This study accentuates the combined effects of titanium, niobium, and reduced manganese levels on the initiation of the ferrite‐to‐austenite transformation. The Hall–Petch relationship was used to draw a correlation between titanium concentration, yield strength, and grain size. Moreover, we explored the recrystallization kinetics of these steels using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, pinpointing titanium's crucial role in modulating the recrystallization dynamics. These findings have significant implications for advancements in steel manufacturing, enhancing the quality and performance of UHSLA steels in industrial applications. [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]

This study focuses on advancing the production of predominantly bainitic heavy plates to meet the API 5L X80 standard. The investigation involves a thorough evaluation of the influence of rolling parameters and austenite conditioning on both microstructural characteristics and mechanical properties. Accurate specifications for chemical composition, processing temperatures, and mean deformations were established using mathematical models and bibliographical references. Four rolling conditions were performed in a reversible single-stand mill, allowing for comprehensive comparison and critical analysis. Microstructural and mechanical characterizations were performed utilizing several techniques, including optical microscopy (OM), scanning electron microscopy (SEM), tensile tests, Charpy impact tests, and hardness tests to ensure adherence to API 5L standards. Additionally, the SEM-EBSD (electron backscattered diffraction) technique was employed for a complementary analysis. The EBSD analysis included crystallographic misorientation maps, mean kernel misorientation parameters (ϑ), low- and high-angle grains boundaries, mean equivalent diameter, and evaluation of the contribution of different strengthening mechanisms to yield strength. Results underscored the significant influence of austenite conditioning on both microstructure and mechanical properties. Considering the specificities of a reversible single-stand mill, it was concluded that, unlike the classic approach for ferritic or ferritic–pearlitic HSLA (high-strength low-alloy steel), when a product with a predominantly bainitic microstructure is required, the accumulated deformation in the austenite during the finishing rolling stage, as well as its temperature, must be meticulously controlled. It was shown that the greater the deformation and the lower the temperature, the more favorable the scenario for the undesired polygonal ferrite formation, which will deteriorate the material's performance. Furthermore, an optimized production route was identified and adapted to the specificities of the employed rolling mill. The presented data have great importance for researchers, manufacturers, and users of API 5L X80 heavy plates. [ABSTRACT FROM AUTHOR]

Two low-alloy quenched-tempered steels (#1 steel and #2 steel) are designed and comparatively studied to achieve ultrahigh yield strength (above 2000 MPa) at relatively low material and process costs. #1 steel and #2 steel have chemical compositions (wt pct) of 0.62 C, 1.62 Si, 0.78 Mn, 1.05 Cr, and 0.18 V and 0.55 C, 1.74 Si, 0.67 Mn, 1.12 Cr, 0.14 V, 0.21 Ni, and 0.20 Mo, respectively. The two steels are heated to 950 °C for 30 minutes, oil quenched, tempered at 240 to 440 °C for 90 minutes and water cooled. Under the same heat treatment parameters, the two steels have basically the same strength (tensile strength 2100 to 2400 MPa; yield strength 1950 to 2100 MPa). Interestingly, as the tempering temperature decreases from 440 °C to 240 °C, the elongation of #1 steel decreases from 10.7 to 1.8 pct, but that of #2 steel is quite stable at ~ 10 pct. #2 Steel has a high tempering resistance, and χ-carbide precipitation of #2 steel is significantly suppressed during tempering. Moreover, when tempering at 240 to 400 °C, the austenite volume fraction of #2 steel is higher than that in the quenched state. The reduction in carbide precipitation contributes to carbon segregation at martensite lath boundaries and other locations, and it may promote the formation of reversed austenite during tempering, which is revealed by 3D atom probe tomography (APT). The excellent mechanical properties of #2 steel are mainly related to the reversed austenite, the fine-grained microstructure of the martensite matrix and the reduced carbides acting as crack initiation sites. [ABSTRACT FROM AUTHOR]

Steel containers used for geological disposal of high-level radioactive waste will be gradually thinned or even perforated due to corrosion, which will lead to radiolysis of nuclides when they contact with infiltrated groundwater and produce H2O2. This work focused on investigating the influence of H2O2 concentration (0%, 0.001%, 0.01%, 0.1% and 1% by volume) on the corrosion behavior of NiCu low alloy steel as the candidate material for containers was comparatively studied by combining corrosion weight loss test, corrosion product analysis, morphology characterization, thermodynamic analysis and electrochemical measurements. As [H2O2] = 0.001%, H2O2 inhibited the formation of γ-FeOOH and enhanced the compactness of rust layer, which effectively blocked the migration of aggressive ions and slowed down the cathodic reduction reaction of rust, thus improving the corrosion resistance of NiCu steel. With the increase of [H2O2] (0.01%→1%), the cathodic process of NiCu steel corrosion was promoted by the increase of dissolved oxygen involved in cathodic depolarization. Meanwhile, the relative content of Fe3O4 in the rust increased, while Fe6(OH)12SO4 and Fe6(OH)12CO3 decreased obviously, which led to the loose and porous rust layer, thus accelerating the corrosion of NiCu steel.

CaF2 has been a very common constituent in the fluxes used for welding of low‐carbon steel plates, owing to its strong ability to lower the liquidus temperature as well as viscosity of the molten flux. But the adverse impact of fluoride evaporation from molten slag on the health of operating personnel and the environment has prompted a worldwide effort to replace CaF2 with more benign constituents. Three compositions with varying MnO concentration in the CaO–MnO–SiO2–Al2O3 system, identified in the current work, have shown promise in terms of ability to control oxygen transfer and modify inclusion generation in the molten metal during the welding of low carbon low alloy steels. However, the melting behavior of a flux needs to be established before recommending its use for welding. Three compositions, with varying MnO concentration, are chosen in the current work. Aided by experimental measurements using high‐temperature microscopy, DTA and simulations using the commercially available thermodynamic package FactSage (version 8.3), this work aims to understand the melting characteristics of the developed fluxes. These characteristics seem to be comparable with a commercial CaF2‐containing welding flux, used as a reference for comparison. In addition, simulations using FactSage suggest that transfer of dissolved O, Si and Mn to the weld metal, while using these fluxes, would be benefitial to performance of the welded joint. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the corrosion resistance in natural seawater (Năvodari area) of two types of low-alloy carbon steels BVDH36 and LRAH36 by electrochemical methods. The electrochemical methods used were the evolution of the free potential (OCP), electrochemical impedance spectroscopy (EIS), polarization resistance (Rp) and corrosion rate (Vcorr), potentiodynamic polarization (PD), and cyclic voltammetry (CV). The studies were completed by ex situ characterization analyzes of the studied surfaces before and after corrosion such as: optical microscopy, scanning electron microscopy and X-ray diffraction analysis. The results of the study show us that the polarization resistance of the low-alloy carbon steel BVDH36 is higher compared to the polarization resistance of the low-alloy carbon steel LRAH36. It is also observed that with the increase in the immersion time of the samples in natural seawater, the polarization resistance of the BVDH36 alloy increases over time and finally decreases, and for the carbon steel LRAH36 the polarization resistance increases. [ABSTRACT FROM AUTHOR]

This study advances the vibration-assisted welding (VAW) technique for joining medium-carbon, low-alloy steels, which are typically challenging to weld. Traditional welding methods suggest low linear energy and mandatory pre- and post-heating due to these steels' poor weldability. However, VAW employs a vibrating table to maintain part vibration throughout the automatic MIG/MAG welding process. This study tested the VAW technique on 42CrMo4 steel samples, achieving satisfactory weld quality without the need for pre- and post-heating treatments. This research revealed that while vibration frequencies between 550 Hz and 9.5 kHz minimally affect the appearance of the weld joint, the oscillation acceleration has a significant impact. The acceleration along the weld axis (ax), combined with the welding speed and vibration frequency, affects the weld surface's appearance, particularly its scaly texture and size. Lateral acceleration (ay) alters the seam width, whereas vertical acceleration (az) affects penetration depth at the root. Notably, if the effective acceleration (aef) surpasses 40 m/s2, there is a risk of molten metal expulsion from the weld pool or piercing at the joint's base. The quality of the joints was assessed through macroscopic and microscopic structural analyses, micro-hardness tests in the weld zone, and bending trials. The mechanical properties of the VAW samples were found to be acceptable, with hardness slightly exceeding that of the samples subjected to pre- and post-heating. Moreover, the VAW process significantly reduced energy consumption and operational time. The employed vibration system, with a power rating of 100 W, operates for just a few minutes, resulting in substantially lower energy usage compared to the traditional pre- and post-heating method, which typically requires a 5 kW electric furnace. [ABSTRACT FROM AUTHOR]

High-strength low-alloy steels are widely used, but their traditional heat-treatment process is complex, energy-intensive, and makes it difficult to fully exploit the material's potential. In this paper, the electropulsing processing technology was applied to the quenching and tempering process of ZG25SiMn2CrB steel. Through microstructural characterization and mechanical property testing, the influence of electropulsing on the solid-state phase transition process of annealing steel was systematically studied. The heating process of the specimen with the annealing state (initial state) is the diffusion-type transition. As the discharge time increased, the microstructure gradually transformed from ferrite/pearlitic to slate martensite. Optimal mechanical properties and fine microstructure were achieved after quenching at 500 ms. The steel subjected to rapid tempering with 160 ms electropulsing exhibited good, comprehensive mechanical properties (tensile strength 1609 MPa, yield strength 1401.27 MPa, elongation 11.63%, and hardness 48.68 HRC). These favorable mechanical properties are attributed to the coupled impact of thermal and non-thermal effects induced by high-density pulse current. Specifically, the thermal effect provides the thermodynamic conditions for phase transformation, while the non-thermal effect reduces the nucleation barrier of austenite, which increases the nucleation rate during instantaneous heating, and the following rapid cooling suppresses the growth of austenite grains. Additionally, the fine microstructure prevents the occurrence of temper brittleness. [ABSTRACT FROM AUTHOR]

It is frequently found in the literature that an acicular ferrite (AF) dominant microstructure has unsteady or even low‐impact toughness. It is necessary to analyze whether they are qualified for real AF. Herein, a Ti‐killed high strength low alloy steel is prepared and subjected to heat‐affected zones simulation tests to induce various AF‐like microstructures. The morphological differences of these microstructures are compared, and their crystallographic characteristics are analyzed. It is found that even within a single prior austenite grain, the transformed microstructure can be heterogeneous. Local areas having clear lath boundaries and a chaotic or interlocking morphology should be classified as AF. Adjacent laths in these areas are from different close‐packed plane and Bain groups. In contrast, local areas having vague lath boundaries and a granular‐bainite‐like morphology should be classified as granular bainite. Neighboring laths in these areas are from the same Bain group, and a relatively low density of high‐angle grain boundaries can be found. The heterogeneous microstructure consisting of granular bainite and AF has a wider grain size distribution and a higher area fraction occupied by large grains, which can lead to the scatter of Charpy impact energy. Criteria for the identification of AF are also proposed in this research. [ABSTRACT FROM AUTHOR]

Herein, a novel approach is developed to enhance the strength, ductility, and low‐temperature toughness of high‐strength low‐alloy steels, overcoming the traditional trade‐off. By incorporating an intercritical subquenching step during the conventional quenching and tempering (QT) process, a microstructure featuring refined lath bainite and a small amount of fine equiaxed ferrite is achieved. The resulting steel exhibits a strength similar to that of QT steel with significantly improved ductility and low‐temperature impact toughness. Compared to traditional QT steel, the new process steel maintains a similar strength. In addition, the elongation increases from ~22.2% to ~24.9%, and the impact energy significantly increases at −50 °C from ~233 to ~347 J. The fine grain size and dense lath structure contribute to the minimal reduction in strength. The presence of equiaxed ferrite and bainite improves the ductility, while plastic deformation and special grain boundaries play a crucial role in enhancing the low‐temperature toughness. This innovative heat treatment method offers an economical solution for producing high‐strength low‐alloy cryogenic vessel steels without compromising strength while greatly improving ductility and low‐temperature toughness. [ABSTRACT FROM AUTHOR]

As one of the protective components, the high strength low alloy structural steel plate had attracted extensive attention because of frequent threats of explosive loads. In this paper, combining explosion experiment, finite element model (FEM) and multi-scale microscopic observation technique, the relationship between macroscopic dynamic response and microscopic damage of low alloy steel plate under the close-range explosion (i.e., 2 cm, 3 cm, 6 cm, and 10 cm) was investigated. After the explosion experiments and validation of the FEMs of the four steel plates, the thickness sections of the position closest to the explosives were selected for microscopic observation of different scales. According to the observation results, the defects were characterized and mainly divided into four damage types. Subsequently, based on the numerical simulation data and microscopic observation results, three models were established to describe the change rules of impulse-explosive distance (I-E), texture-explosive distance (T-E), as well as impulse-texture (I-T), respectively. The results showed that when the explosive distance was 2–10 cm, I-E and T-E were consistent with the quadratic fit. In addition, the texture of base material (BM) was 3.42, which was 2.36 times larger than that of closest explosive distance sample. The variation law of I-T better revealed the relationship between the macroscopic dynamic response and microscopic damage with different explosive distances which agreed with the linear model. These results can be used to predict and prevent damage propagation of low alloy steel plate under the close-range explosion and improve the protective ability of protective materials. [ABSTRACT FROM AUTHOR]

In this work, the effect of laser shock peening (LSP) on the electrochemical behavior of HSLA steel (ASTM A 588 Grade D) in 3.5 wt.% NaCl solution was investigated. The microstructural evolution, micro-texture development, surface roughness, residual stress development, microhardness, dislocation density, potentiodynamic polarization, and electrochemical impedance spectroscopy were studied in depth. The corroded surfaces (with and without LSP) were characterized using scanning electron microscopy and Raman spectroscopy for understanding the nature of the passive film formation and its stability. The results revealed that LSP treatment marginally refines the near-surface microstructure from 9.1 to 7.4 μm and generated high compressive residual stress (CRS) of about 500 MPa on the top surface; such variation happened due to severe plastic deformation during LSP. The micro-texture analyses of the laser-peened specimens (on the surface) revealed that {011} <111> texture components were significantly increased while the γ-fiber weakened after laser-peening. Dislocation density was obtained ~ 9.266 × 1012 on the unpeened and ~ 1.158 × 1013 on the laser-peened surfaces, indicating that higher pressure shock waves plastically deformed the top layer of the peened specimen. The corrosion studies indicated about 4 times improvement in the corrosion resistance of the peened specimens—the combined effects of LSP-induced gradient CRS and refined microstructure improved the corrosion resistance. The EDS and Raman spectroscopy results demonstrated the persistence of a compact and continuous passive oxide film/layer, primarily made of Fe2O3, on the surface of the laser-peened specimens. [ABSTRACT FROM AUTHOR]

This study evaluates the feasibility of producing high-strength low-alloy (HSLA) steel using advanced wire-fed laser additive manufacturing (LAM-W) and wire arc additive manufacturing (WAAM) technologies. Optimized parameters were independently developed for each heat source, utilizing a self-designed HSLA steel wire as the feedstock. Microstructural features and mechanical properties of the fabricated steels were characterized and compared, taking into account differences in heat input and cooling rates. LAM-W samples exhibited a finer columnar grain microstructure, while both LAM-W- and WAAM-produced steels predominantly showed lower bainite and granular bainite microstructures. LAM-W demonstrated higher strength and hardness, lower ductility, and comparable low-temperature toughness compared to WAAM. Both processes demonstrated an excellent balance between strength and ductility, with absorbed energy exceeding 100 J at −40 °C. The study confirms the feasibility of producing high-strength and tough HSLA steel parts using LAM-W and WAAM technologies, and compares the advantages and disadvantages of each method. These findings assist in selecting the most suitable wire-fed AM process for HSLA steel fabrication at high deposition rates. [ABSTRACT FROM AUTHOR]

This study studied the tribological properties of PVD AISI 4140 low – alloy TiN coated and reported. The morphologies before testing are assessed with a laser confocal microscope and XRD. Three tests are conducted per sample: the rotating, scratch, and reciprocation tests. The contour of counter bodies and wear scares are studied and reported. The wear scares are also further studied using the SEM-EDS chemical analysis to study the amount of wear that has occurred. The results showed a change in roughness and waviness after coating. In the reciprocating tests showed a high degree of spalling on the TiN sample is observed with a higher wear volume compared to the substrate. However, a lower coefficient of friction is observed. This is similar to the rest of the tests. [ABSTRACT FROM AUTHOR]

Low-alloy wear-resistant steel often requires the addition of trace alloy elements to enhance its performance while also considering the cost-effectiveness of production. In order to comparatively analyze the strengthening mechanisms of Mo and Cr elements and further explore economically feasible production processes, we designed two types of low-alloy wear-resistant steels, based on C-Mn series wear-resistant steels, with individually added Mo and Cr elements, comparing and investigating the roles of the alloying elements Mo and Cr in low-alloy wear-resistant steels. Utilizing JMatPro software to calculate Continuous Cooling Transformation (CCT) curves, conducting thermal simulation quenching experiments using a Gleeble-3800 thermal simulator, and employing equipment such as a metallographic microscope, transmission electron microscope, and tensile testing machine, this study comparatively investigated the influence of Mo and Cr on the microstructural transformation and mechanical properties of low-alloy wear-resistant steels under different cooling rates. The results indicate that the addition of the Mo element in low-alloy wear-resistant steel can effectively suppress the transformation of ferrite and pearlite, reduce the martensitic transformation temperature, and lower the critical cooling rate for complete martensitic transformation, thereby promoting martensitic transformation. Adding Cr elements can reduce the austenite transformation zone, decrease the rate of austenite formation, and promote the occurrence of low-temperature phase transformation. Additionally, Mo has a better effect on improving the toughness of low-temperature impact, and Cr has a more significant improvement in strength and hardness. The critical cooling rates of C-Mn-Mo steel and C-Mn-Cr steel for complete martensitic transition are 13 °C/s and 24 °C/s, respectively. With the increase in the cooling rate, the martensitic tissues of the two experimental steels gradually refined, and the characteristics of the slats gradually appeared. In comparison, the C-Mn-Mo steel displays a higher dislocation density, accompanied by dislocation entanglement phenomena, and contains a small amount of residual austenite, while granular ε-carbides are clearly precipitated in the C-Mn-Cr steel. The C-Mn-Mo steel achieves its best performance at a cooling rate of 25 °C/s, whereas the C-Mn-Cr steel only needs to increase the cooling rate to 35 °C/s to attain a similar comprehensive performance to the C-Mn-Mo steel. [ABSTRACT FROM AUTHOR]

Using the synergistic effect of the influence of Cr, Mo, Nb, V, Cu, and other elements on the properties of steels, a low-alloy structural steel with high performance properties has been developed. The microstructure, mechanical properties and corrosion resistance of the steel have been studied. The steel structure is multiphase and consists of polygonal ferrite and M/A islands. The yield strength of the steel at 600°C is at least 2/3 of the yield strength at room temperature. During 360 h of the corrosive effect of salt mist, the corrosion rate of the steel gradually decreases with increase of the time, and the structure of the rust layer is transformed from loose to dense. The mechanical properties, heat resistance, corrosion resistance and heat resistance of steel meet the requirements for materials of building structures. [ABSTRACT FROM AUTHOR]

The results of studies of hot cracks formed in cast shapes from low-alloy steel G21Mn5 are presented. Macroand microstructural analyses are carried out. Fractography studies of samples cut from castings used in the production of railway freight cars are performed. The criteria used to assess the susceptibility of alloys to hot brittleness are considered. It is shown that the orientation of dendritic crystals affects significantly the formation of hot cracks, and the direction of the dendrite growth is determined by the conditions of heat dissipation, which are influenced in their turn by the geometry of the casting. The phenomenon of coalescence under the conditions of misorientation of neighbor dendrites and its effect on the formation of hot cracks is studied. A modified RDG criterion is suggested, which allows for the influence of the geometry of the cast product on the formation of hot cracks through the angle of misorientation of neighbor crystals. [ABSTRACT FROM AUTHOR]

Martensitic low-alloy steels are widely used in machine construction. Due to their declared weldability, arc welding is most often used to join elements made of this type of steel. However, the high temperature associated with welding causes unfavourable changes in the microstructure, resulting in reduced abrasion resistance. Therefore, it is important to know the tribological properties of the welded joint. This article presents the results of a study on the abrasion wear resistance of a welded joint of an abrasion-resistant steel. This study tested a welded joint of an abrasive-resistant steel produced by the arc welding method. Wear testing of the welded joint was carried out under laboratory conditions by the ball-cratering method in the presence of abrasive slurry on the cross-section of the welded joint. Based on the test results, the change in the abrasive wear rate of the material as a function of the distance from the welded joint axis was determined. It was also found that the thermal processes accompanying welding caused structural changes that increased the wear rate index value. Adverse changes in the tribological properties of a welded material persist up to a distance of approx. 20 mm from the weld centre. [ABSTRACT FROM AUTHOR]