Steel Grades Research Articles

The upper bound of the buckling stress of axially compressed carbon steel circular cylindrical shells

Abstract The buckling stress of axially compressed circular cylindrical shells (CCSs) is highly sensitive to imperfections. The literature proved that it is hard to generalize the imperfections and the designers are encouraged by the Eurocode EN 1993:1-6 (2007) to conduct geometric and material nonlinear with imperfections analysis (GMNIA) considering different possible forms of imperfections for the shell under design. As GMNIA type of analysis is difficult and requires highly skilled engineers, knowledge of the upper limit of the buckling stress serves as a guide and prevents the overestimation of the shell buckling resistance. It also encourages average skill designers to attempt GMNIA as far as the maximum possible limit is known. Thus, the objective of this study is to provide the upper bound of the buckling stress of carbon steel CCSs. Geometric and material nonlinear analysis (GMNA) of perfect circular cylindrical shells for a wide range of R/t ratio is conducted. It has been found that for cases of small and intermediate R/t values the buckling stress can be predicted by GMNA while the elastic buckling controls those of larger R/t values. The limiting R/t values depend on the steel grade and have been derived for the available standard grades of carbon steel. The obtained results are presented in terms of simplified formulas and a design chart to be used by engineers. Application of the proposed upper bound in simplified design approaches using knock down factor (KDFs) has also been discussed.

Remaining Fatigue Strength of an Orthotropic Steel Deck with Respect to a Repair Method by Cold Joining Techniques

AbstractThe increased traffic loads of the last decades led to an overload of the existing infrastructure. Especially for orthotropic steel decks of bridges, which are prone to fatigue fractures, this have led to structural damages of different categories. With respect to category 2 damages and their retrofit, this paper presents results of fatigue tests on the nonwelded constructional details of an old, demolished orthotropic steel deck. The samples were extracted from a highway bridge with an orthotropic steel deck built in Germany in the 1970s. In comparative fatigue tests on identical constructional details made of new material with the same steel grade, the remaining fatigue strength was determined. Based on the problem of manganese sulfides in old steels the potential of the repair method by cold joining techniques was emphasized. Characteristic load‐bearing capacities for a Eurocode 3‐compliant design of a structural blind fastener were determined and their use in a pilot project was reported.

Material selection for railroad bridge bearings to avoid brittle fracture

AbstractSteel structures are typically engineered for the upper range of the steel toughness‐temperature curve. To account for the reduction in toughness properties within the temperature transition range, additional safety assessments are necessary. These assessments rely on fracture mechanics considerations and enable the selection of an adequate steel material to prevent brittle fracture. Considering this context, recommendations were already put forth in 2011 to govern the appropriate choice of steel grades for bearing components. However, these recommendations are no longer entirely current in light of more recent findings. As a result, the German Centre for Rail Traffic Research has called a research project with the aim to formulate proposals to expand the regulatory framework related to suitable material selection, aimed at preventing brittle fracture in bridge bearings.

High-Temperature Tensile Behavior of Structural Steel Grades with Varying Manganese Contents

Abstract Three low-carbon (∼0.1 wt.% carbon) grades of structural steel with varying manganese content (0.75–1.5 wt.%) with ferrite-pearlite microstructure were used for the study. The 1.5 % manganese steel is a microalloyed steel with vanadium, niobium, and titanium content, which is strengthened by interphase precipitates. The steels were tensile tested at room temperature and in the temperature range between 200°C–700°C, at 100°C intervals. The elevated temperature flow strengths of the steels studied show higher strength values for the higher manganese steel. It was found that the manganese enhanced the strength at all ranges of test temperatures. The retention factor of the conventional structural steels was less than or equal to 0.50 against 0.66 for a fire-resistant steel grade. The study shows that the addition of elements such as chromium, molybdenum is required to achieve a higher retention factor to fulfill the requirement of fire resistance characteristics.

Incorporating composition into life cycle assessment of steel grades

Steel is a vital material in modern industries due to its versatility and remarkable properties. In a world that is increasingly concerned about the environment, it is necessary to incorporate good practices that help reduce the environmental impact of our economies. An important aspect is evaluating the environmental impact of materials throughout their life cycle. However, calculating this impact using generic databases can be challenging, as they may lack the necessary specificity. To obtain more accurate environmental impact calculations, it is essential to consider the composition of the materials. Each steel grade, for example, can vary in the content of alloying elements, which influences its environmental impact. Therefore, particularising calculations based on compositions is essential for making informed and sustainable material selection decisions. This article presents a calculation methodology to establish a Life Cycle Inventory of steel, emphasising the specific composition and using datasets of steel production in a Basic Oxygen Furnace (BOF) developed by ecoinvent as reference. The methodology presented seeks to allow the systematic calculation of the environmental impact of any steel considering its composition, contribute to the incorporation of environmental criteria in the selection of materials, and quantify the content of critical raw materials according to the latest report published by the European Union. Likewise, a case study is included, in which the composition's influence on the environmental impact of 10 steel grades widely used in induction cooktops has been analysed.

Eco-Friendly and Sustainable Inhibitors for Steel Corrosion in Acidic Media

The inhibitory action of eco-friendly food waste extracts, Red Beta Vulgaris leaves (R.B.V.L) and Prunus cerasus seeds (P.C.S), on the B7 grade steel corrosion in 1.0 M HCl were investigated utilizing chemical and electrochemical measurements. The functional groups of both extracts have been predicted utilizing Fourier transform infrared spectroscopy (FTIR). The potentiodynamic polarization technique reveals that the two extracts act as a mixed-type inhibitor. The electrochemical impedance spectroscopy technique shows that the corrosion process is controlled via charge transfer. Both extracts exhibit a maximum inhibitory efficiency of 75%. Langmuir and Flory–Huggins isotherms, as well as the Kinetic-thermodynamic model, were used to study the inhibition mode of both extracts. The values of the change in free energy of adsorption, ΔGads, demonstrate that the adsorption occurs via the physisorption (electrostatic) mechanism. The activation parameters were determined and discussed. The quantum chemical calculations have proceeded to show the main active ingredients.

Experimental study on the fatigue behavior of CFRP-strengthened cracked steel plates under eccentric axial tension

In this paper, an experimental investigation has been conducted to study the fatigue behavior of single edge-notch steel plates strengthened with CFRP (laminates/sheets). The plates have been subjected to eccentric fatigue under axial loading conditions. The experimental study includes fourteen specimens and has been tested under axial loading until failure. The constant parameters in the study are steel material grade, steel plate dimensions, and fatigue loading conditions. Meanwhile, the studied parameters are steel plate initial edge crack size, CFRP configurations (length, one or two-sided, and laminates or sheets), and adhesive material strength. The experimental results revealed that the fatigue life for specimens strengthened with CFRP sheets or CFRP laminates can be improved by a factor of 1.15 to 3.87 and 1.47 to 6.32, respectively, compared with the un-strengthened specimens. The results show that using CFRP can be considered an efficient way to repair the initial cracks in steel elements under eccentric axial fatigue loading.

Morphological Evolution of MnS During Hot Deformation and Isothermal Homogenization in Nonquenched and Tempered F40MnVS Grade Steel

Morphological Evolution of MnS During Hot Deformation and Isothermal Homogenization in Nonquenched and Tempered F40MnVS Grade Steel

Challenges for testing hydrogen-assisted cold cracking in weld seams of high-strength steel grades

Challenges for testing hydrogen-assisted cold cracking in weld seams of high-strength steel grades

Effect of Quenching Post‐Intercritical Austenitizing on the Microstructure and Tensile Properties of an K55 Grade Steel for Oil and Gas Industry

The API K55 grade steel is widely utilized in seamless pipes for oil and gas exploration, especially as casing pipes for wellbores. Traditionally, this steel is processed using hot rolling followed by quenching and tempering to achieve the desired dimensional and microstructural characteristics, balancing high strength with ductility. This article introduces an alternative method to attaining the required tensile properties for API K55 grade steel by employing a biphasic microstructure (ferrite/martensite) achieved through quenching post‐intercritical austenitizing heat treatment to high‐strength‐low‐alloy steel. Thermodynamic simulations and dilatometric experiments revealed that increasing the austenitizing temperature enhances austenite formation, decreasing significantly its carbon content, which facilitates martensitic transformation and increases the Ms and Mf temperatures. A complete phase transformation mapping was presented, highlighting how the austenitizing temperature influences martensitic transformation kinetics during the quenching heat treatment. It was concluded that austenitizing at 750 °C, followed by quenching and short tempering at 650 °C, produced a biphasic microstructure with 30% ferrite and 70% martensite, providing a favorable balance between mechanical strength and ductility that meets the API K55 grade requirements, surpassing traditional methods in the industry.

Analysis of the Suitability of Ultrasonic Testing for Verification of Nonuniform Welded Joints of Austenitic-Ferritic Sheets.

The purpose of the presented research was to determine the suitability of using ultrasonic testing (UT) to inspect heterogeneous, from a material point of view, welded joints on the example of the joints of a ferritic steel element with elements made of an austenitic steel. The echo technique with transverse (SEK) and longitudinal wave heads (SEL) addressed this issue. Due to the widespread use of 13CrMo4-5 and X2CrNiMo17-12-2 steel grades in the energy industry, they were selected as the test materials for the study. The objects of the presented research were welded joint specimens with thicknesses of 8, 12, and 16 mm and dimensions of 300 × 300 mm, made using the 135 metal active gas (MAG) process with the use of the Lincoln 309LSi wire-a ferritic-austenitic filler material. The stages of the research task were (1) making distance-amplitude curve (DAC) patterns from the test materials; (2) preparation of specimens of welded joints with artificial discontinuities in the form of through-holes; (3) performing UT tests on welded joints with artificial discontinuities using heads with 60° and 70° angles for the transverse wave and angle heads for longitudinal waves with similar beam insertion angles; (4) selection, by radiographic testing (RT), of welded joint specimens with natural discontinuities in the form of a lack of sidewall fusion; (5) performing UT tests on welded joints with natural discontinuities, using heads as welded joints with artificial discontinuities. It was found that (1) the highest sensitivity of discontinuity detection was obtained by performing tests on the ferritic steel side, which is due to the lower attenuation of the ultrasonic wave propagating in ferritic steel compared to austenitic steel; (2) the best detection of discontinuities could be obtained using a longitudinal ultrasonic wave; (3) there is a relationship between the thickness of the welded elements, the angle of the ultrasonic beam introduction, and the effectiveness of discontinuity detection.

Effects of spatial microstructure characteristics on mechanical properties of dual phase steel by inverse analysis and machine learning approach

This work aims to investigate complex relationship between microstructure characteristics and mechanical properties of dual phase (DP) steel through an inverse analysis based on Markov chain Monte Carlo (MCMC) method combined with meso-scale material modelling. In this framework, a machine learning approach as surrogate model was developed, in which support vector regression (SVR) and artificial neural network (ANN) were trained using results from representative volume element (RVE) simulations coupled with damage model, which were previously calibrated with experimental data of commercial DP steel grades. Moreover, specific microstructure descriptors including Moran’s index, martensite band index and martensite orientation were proposed for representing effects of spatial distributions of martensitic phase. As a result, inverse predictions of microstructure characteristics of DP steels for achieving defined yield strength, tensile strength, uniform elongation and toughness were presented. The inverse analysis could solve the non-uniqueness of structure–property relationships of steel, whereby significances of dispersed structures and aligned martensite bands were highlighted in details. The approach fairly dealt with multi-target optimization and high dimensional problem, which can be further applied as a guideline for designing DP microstructures with enhanced mechanical properties.

The Process of Steam Oxidation Degradation of High Cr Steel after 125 000 Hours at 568 °C under 16.5 MPa

AbstractThe aim of this work was to analyze the effect of steam oxidation when TP347HFG grade steel was exposed to industrial conditions for 125 000 hrs at 568 °C under 16.5 MPa pressure. The testing material was acquired from one of the coal power plants operating in Poland. Comprehensive investigations were carried out on the outer surface and cross section of the exposed sample using XRD, SEM/EDS and TEM. The analysis revealed the development of a fine grain oxide scale thickness spanning from 20 to 200 µm, consisting Fe2NiO4 (78 %), Cr1.3Fe0.7O3, Fe2O3 (0.8 %) and Fe3Co (0.8 %). Cross-sectional observations showed the formation of grains rich in Nb precipitates type MX carbonitrides surrounded by M23C6 carbides developed as a continuous net at the grain boundaries. The extent of material degradation under the influence of temperature, pressure and exposure time has been meticulously discussed. Graphical Abstract

Investigations on corrosion rate, mechanical properties and structural homogeneity of interpulse TIG dissimilar weldments

This manuscript aims to investigate the welding characteristics, bead profile, structural integrity and corrosion behavior of low-carbon steel and Monel grade 400 dissimilar joints. The structures were developed using advanced welding technique, gas tungsten constricted arc welding, with Mo-based filler wire. Dissimilar metals after welding have been tested for internal inspection using X-ray radiography and confirmed to be free from all welding defects. Corrosion tests were carried out at various zones of weldment and characterized in a 3.5 wt% NaCl solution at 10 mV/s scan rate. The welding characteristics have been studied by conducting various tests including Vickers hardness, tensile and impact test. To reveal the structural integrity and perform chemical composition analysis of constricted arc weldment, OM/SEM techniques were used. Corrosion rate at steel interface is lower than that at the Monel 400 interface by 9.7% due to the less accumulation of heat. Uniform grain distribution and structural homogeneity were also observed along the weld zone due to constricted arc and controlled heat input.

Development of an innovative FlexLock Connector for prefabricated prefinished volumetric construction

Prefabricated Prefinished Volumetric Construction (PPVC) technology has emerged as a revolutionary building method, has garnered increasing global attention and adoption. Given the discontinuous nature of columns within PPVC structures, it becomes imperative to underscore the critical role that the reliability and efficiency of connections between modules play in determining the overall performance and stability of PPVC. This paper introduces an innovative FlexLock Connector which consists of lock cylinder, latch bolt, groove, corner fitting and gusset plate. The designed mechanism of the individual parts makes this connection adaptable to an eight-column, sixteen-beam system, allowing for quick installation and easy disassembly. Considering the potential challenges such as self-locking and geometric conflicts during the installation process of the proposed connection, this paper firstly elucidated the geometric constraints of the connection theoretically. Additionally, several finite element models (FEM) were developed and underwent a validation process conducted against 12 reported inter-module connection experimental results. Following this validation, a FEM was developed and underwent on installation process with the chamfer of the latch bolt falling within the range of the twice the friction angle (2φ) and exceeding the range of 2φ were both studied. Additionally, a total of 19 FlexLock Connector specimens were employed to investigate the tensile performance of the connection, varying parameters were selected such as the height of the strike plate (hlc), width of the latch bolt (wlb), diameter of the inner cylinder (Dic), steel grade of the latch bolt, height of the end plate (hep), height of the latch bolt (hlb), and steel grade of the corner fitting. The results identified five distinct failure modes of the proposed connection under tensile load, highlighting the contributions of key structural elements. Finally, a theoretical formula was proposed for the tensile bearing capacity of the FlexLock Connector, and validated through comparison against numerical results.

Effect of Addition of Rare Earth Element Cerium on the Microstructure and Mechanical Properties of Microalloyed Peritectic Grade Steel

Effect of Addition of Rare Earth Element Cerium on the Microstructure and Mechanical Properties of Microalloyed Peritectic Grade Steel

Local shear fracture properties in heat-affected zone of resistance spot-welded advanced high-strength steel

In the process of resistance spot welding of advanced high-strength steel (AHSS), the development of heat-affected zones (HAZs) considerably modifies the mechanical properties of the weld region. However, the limited reporting in the study of shear behavior in the HAZ hinders the accurate prediction of joint fracture and failure behavior. This study focused on the shear fracture behavior of resistance spot-welded AHSS. Given the limited extent of the HAZ, a miniature shear test was designed and shear fracture tests were conducted on JSC590, JSC980, and JSC1180. These tests facilitated the acquisition and compilation of data regarding the shear mechanical properties of diverse steel grades and their respective HAZs. A hardness-based empirical model for the strength coefficient and the strain-hardening exponent in Hollomon's law was introduced, and this model was subsequently integrated into finite element method calculations. The accuracy of the model was validated by shear strength reproductions, exhibiting errors within the range of 5.4%–13.5% and the averaged error was less than 10%. Further analyses confirmed that stress triaxiality at critical positions varied from 0 to 0.33, indicative of shear-dominant stress conditions. Moreover, the evolution of stress states revealed a notable association between the fracture surfaces across different stress states and steel grades. These findings fill the gap regarding the shear behavior of localized HAZs and expand the understanding of their mechanical behavior under various stress states. It will contribute to accurate fracture prediction by stress triaxiality based fracture criteria, such as Modified Mohr-Coulomb (MMC) model, applied to AHSS.

A Comparative Study on the Corrosion Performance of A7, A36 and A588 Alloys at Different NaCl Concentration Exposure

Corrosion can significantly impact the performance of structures, and corrosion-related maintenance is a primary contribution to annual transportation infrastructure costs. The current NBI data reports that the poor condition of the bridges around US have increased by 10%, and 50% of the bridges in Connecticut are either in poor or fair condition. Bridges in the US share approximately 37% of the total annual cost due to corrosion. Bridges are primarily constructed of A7, A36, A588, and A242 steel. ASTM A7 steel was used in bridge construction until 1967. Major limitations of A7 steel include poor corrosion resistance and mechanical properties, which ultimately led to the replacement of A7 steel by A36 steel after 1967. Though A36 steel shows better mechanical properties, it does not possess improved corrosion performance compared to A7. A588 and A242, which are also called weathering steels, display significantly higher corrosion resistance paired with desired mechanical properties, but the cost of these so-called weathering steels is also higher. The present study aims at characterizing the corrosion performance of bridge steels A7, A36 and A588 under a wide range of chloride-rich environments so that we may improve our predictions for bridge longevity.A major portion of the existing literature on steel corrosion mechanisms considers the study of plain carbon steel. Plain carbon steels form corrosion products such as Goethite, Akageneite, Lepidocrocite, and Magnetite, having the chemical formulas α-FeOOH, β-FeOOH and γ-FeOOH and Fe3O4 respectively. γ-FeOOH forms during the initial stages of corrosion formation where Magnetite being the final product. β-FeOOH is an intermediate product but is detrimental for the performance of the bridge since the oxide formed is not protective.The addition of specific alloying elements in the bridge steel grades (including Cu) can heavily influence the corrosion mechanisms at work and subsequently the corrosion rates. Further, the exposure to various environmental conditions such as rain, snow, hail, wind, and thermal cycles will lead to successive wetting and drying conditions. Bridges in colder climates are exposed to de-icing salts that can accumulate on horizontal surfaces or within the corrosion products that form. Each of these factors makes accurate prediction of corrosion rates on specific bridge components difficult.The current study compares the corrosion performance of A7, A36 and A588 alloys at different NaCl concentration exposure (1 wt.%, 2 wt.%, 3.5 wt.% and 5 wt.%) for difference steel surface conditions (oxidized and polished). Corrosion studies on these alloys were performed using wet-dry cyclic exposure to obtain corrosion at an accelerated pace. Each wet-dry cycle consisted of 15 minutes of wetting and 1 hour drying period. Test coupons were in the size of 50 mm×25 mm×4.76 mm. A total of 400 wet/dry cycles were performed to determine the effect of longer exposure to salt environments. Batches of samples of each alloy were collected at 25, 50,75, 100, 150, 200, 250, 300, 350, 400 cycles to observe corrosion trends with increase in cycles. Further, the samples were photographed, and the surfaces were compared. Corrosion samples retrieved from bridges in Connecticut were compared to the lab-tested coupons. The phases present in the corrosion products were characterized using XRD and SEM. The results showed lower magnetite compared to the field samples, and the presence of detrimental β – FeO(OH,Cl) was significantly higher at the higher [Cl-] concentrations. Mass gain studies were performed by measuring the weight of each test coupon at regular intervals throughout the wet-dry cyclic testing. The mass gain per unit surface area of the sample was calculated for the different conditions. Cross-sections of the corroded samples were examined using optical light microscopy and SEM-EDS. These results will be used to build and validate a prediction tool for field evaluation of bridge corrosion.

Prediction and Prevention of Bridge Performance Degradation Due to Corrosion, Material Loss, and Microstructural Changes

Corrosion can significantly impact the performance of structures, and corrosion-related maintenance is a primary contribution to annual transportation infrastructure costs. The current NBI data reports that the poor condition of the bridges around US have increased by 10%, and 50% of the bridges in Connecticut are either in poor or fair condition. Bridges in the US share approximately 37% of the total annual cost due to corrosion. Bridges are primarily constructed of A7, A36, A588, and A242 steel. ASTM A7 steel was used in bridge construction until 1967. Major limitations of A7 steel include poor corrosion resistance and mechanical properties, which ultimately led to the replacement of A7 steel by A36 steel after 1967. Though A36 steel shows better mechanical properties, it does not possess improved corrosion performance compared to A7. A588 and A242, which are also called weathering steels, display significantly higher corrosion resistance paired with desired mechanical properties, but the cost of these so-called weathering steels is also higher. The present study aims at characterizing the corrosion performance of bridge steels A7, A36 and A588 under a wide range of chloride-rich environments so that we may improve our predictions for bridge longevity.A major portion of the existing literature on steel corrosion mechanisms considers the study of plain carbon steel. Plain carbon steels form corrosion products such as Goethite, Akageneite, Lepidocrocite, and Magnetite, having the chemical formulas α-FeOOH, β-FeOOH and γ-FeOOH and Fe3O4 respectively. γ-FeOOH forms during the initial stages of corrosion formation where Magnetite being the final product. β-FeOOH is an intermediate product but is detrimental for the performance of the bridge since the oxide formed is not protective.The addition of specific alloying elements in the bridge steel grades (including Cu) can heavily influence the corrosion mechanisms at work and subsequently the corrosion rates. Further, the exposure to various environmental conditions such as rain, snow, hail, wind, and thermal cycles will lead to successive wetting and drying conditions. Bridges in colder climates are exposed to de-icing salts that can accumulate on horizontal surfaces or within the corrosion products that form. Each of these factors makes accurate prediction of corrosion rates on specific bridge components difficult.The current study compares the corrosion performance of A7, A36 and A588 alloys at different NaCl concentration exposure (1 wt.%, 2 wt.%, 3.5 wt.% and 5 wt.%) for difference steel surface conditions (oxidized and polished). Corrosion studies on these alloys were performed using wet-dry cyclic exposure to obtain corrosion at an accelerated pace. Each wet-dry cycle consisted of 15 minutes of wetting and 1 hour drying period. Test coupons were in the size of 50 mm×25 mm×4.76 mm. A total of 400 wet/dry cycles were performed to determine the effect of longer exposure to salt environments. Batches of samples of each alloy were collected at 25, 50,75, 100, 150, 200, 250, 300, 350, 400 cycles to observe corrosion trends with increase in cycles. Further, the samples were photographed, and the surfaces were compared. Corrosion samples retrieved from bridges in Connecticut were compared to the lab-tested coupons. The phases present in the corrosion products were characterized using XRD and SEM. The results showed lower magnetite compared to the field samples, and the presence of detrimental β – FeO(OH,Cl) was significantly higher at the higher [Cl-] concentrations. Mass gain studies were performed by measuring the weight of each test coupon at regular intervals throughout the wet-dry cyclic testing. The mass gain per unit surface area of the sample was calculated for the different conditions. Cross-sections of the corroded samples were examined using optical light microscopy and SEM-EDS. These results will be used to build and validate a prediction tool for field evaluation of bridge corrosion.

Microstructural, mechanical and nondestructive characterization of X60 grade steel pipes welded by different processes

Abstract In this paper, the welding quality of API 5L X60 steel pipes was investigated after the application of three different welding scenarios by applying submerged arc welding (SMAW), tungsten inert gas (TIG) and hybrid (TIG + SMAW) welding methods with an average heat input of ca. 1 kJ mm−1 for all passes. For this purpose, the ultrasonic and radiographic tests were done to detect possible discontinuities such as crack and porosity in the welding zones. In addition, the macro and microstructures of weld zones were made to examine different zones in terms of weld quality and phases. Moreover, the hardness, impact toughness and tensile tests were carried out to determine the mechanical properties of the weldments. The tensile strength of the pipe weldments was recorded to be ∼603, 610 and 625 MPa after the welding of pipes by SMAW, TIG + SMAW and TIG welding, respectively. In addition, the impact toughness of the welds was obtained to be 48, 76 and 66 J, for these welding methods, successively. According to the experimental findings, all three welding plans were successfully applied to the steel pipes and found to be suitable regarding the relevant international standards.