Structural Carbon Steel Research Articles

Influence of 10% NaCl on Carbon Structural P235TR2 Steel at 25oC

Steels dedicated to work in a corrosive environment are corrosion-resistant steels. Nevertheless, unalloyed steels also work in corrosive environments. Low-carbon non-alloy steels are a popular construction material for pipelines. They owe their popularity to low costs and good susceptibility to welding. An example of the use of steel is pipelines for the transmission of various substances. These substances often contain sodium chlorides. Unalloyed steels are prone to surface corrosion. This type of corrosion does not pose a high risk of failure, is completely predictable and can be monitored very well by measuring the wall thickness of the pipeline with non-destructive methods. Pipelines can be placed in production halls. Unless the temperature of the flowing medium is increased (these steels are not usually used for work at reduced temperatures), their operating temperature is about 20-25oC. Taking the above into account, tests of the corrosion rate of the popular P235TR2 steel grade at 25oC were carried out. The corrosive environment was a 10% NaCl aqueous solution. Samples were taken from the tube and soaked in NaCl solution for up to 432 hours, with weight loss determined every 48 hours. It was found that P235TR2 steel has a satisfactory corrosion resistance to low concentrations of NaCl at 25oC. The nature of the corrosion process was classic and consisted of two typical stages. In the first, the steel showed high resistance to the applied corrosive environment, in the second, due to the progressive development of the surface, the corrosion rate increased at a higher rate.

Influence of Impurity Morphology on the Fatigue Strength of High-Purity Structural Steel Melted in an Electric Furnace

A modern user requires low operating costs, but also reliability from machines and technical devices. Reliability during the service life depends on the quality of construction solutions, but also largely on the quality, properties and adaptation to the working conditions used in the construction of construction materials. During the operation of technical objects, their a highly predictable wear occurs. The problem is the phenomena of premature wear and damage of elements. The causes of failure of technical facilities are usually complex and depend on many factors. They can include the human factor and the one related to the quality, selection, production and technological processes of the materials used in the construc-tion of the facility. In real technical facilities, many premature failures are caused by material fatigue, which is related to the quality and distribution of impurities in the material. The paper presents the change in fatigue strength for rotational bending of low-carbon structural steel hardened and tempered at different temperatures as the effect of the size and distance between impurities on the fatigue strength of high-quality carbon structural steel melted in the industrial conditions in an electric arc furnace.

New proposal for the bending moment capacity of tubular T-joints in carbon steel and stainless steel structures

The expected failure mode of T-joints between rectangular hollow sections subjected to bending moment with a ratio of the brace width (b1) over the chord width (b0) below 0.85 (i.e., β=b1/b0≤0.85) is the chord face failure, produced by yielding. This paper presents the development of a numerical model to reproduce this phenomenon, calibrated against experimental laboratory tests, which is then used to carry out a large parametric study, where the influence of the main geometric parameters involved in the joint resistance –the chord width (b0), the chord thickness (t0), the chord radius (R0), the brace width (b1), the brace height (h1) and the weld thickness (a)– is assessed for two different materials: S275 carbon steel and EN 1.4301 austenitic stainless steel. The results derived from the parametric study suggested that a different yield line mechanism may develop for higher β-values (β≥0.45) than that considered in current European and American codes. Hence, a new formulation for estimating the bending resistance of T-joints exhibiting chord face failure modes is presented based on a different yield line mechanism developed in this paper. This formulation includes additional geometric parameters that are dismissed in the current formulation, such as the chord radius and the weld thickness, which are found to have a non-negligible influence on the joint resistance. Moreover, the proposed formulation is adjusted in order to be used for joints with lower β-values without losing accuracy. Additionally, the new proposed formulation is adapted for stainless steel joints by combining it with the Continuous Strength Method (CSM) formulation with promising results. Finally, the soundness and safety of the proposed formulation is statistically demonstrated.

The analysis of factors affecting the alloy yield of carbon structural steel Q235 in the smelting process

ABSTRACT Ferroalloy is essential for steelmaking, used for deoxidation and alloying of molten steel. However, each plant has different process flows and technical parameters, leading to varying yields for each alloy type. This study collected production records of Q235 carbon structural steel in Ningbo Iron and Steel Co. for nearly 8 months. Consumption of various ferroalloys was counted, and the use rules for silicon, manganese, and aluminum alloys were summarized. The correlation of silicon and manganese yield with other variables was analyzed using Spearman correlation and clustering. Factors affecting alloy yield were identified, and the important degree and action mode of each key factor were obtained through path analysis. This study resulted in increased yields of silicon and manganese by 2.88% and 3.43%, respectively. Despite these improvements, challenges remain, such as poor data collection accuracy and low transmission efficiency.

Loading frequency effect on the fatigue endurance of structural carbon steels: Estimation based on dislocation motion theory and experimental verification of the model

Based on a previous model dedicated to the prediction of the loading frequency effect on the fatigue endurance of low-carbon steels, the present work elaborates a strategy to extend its application range to medium- and high-carbon steels. From this viewpoint, fatigue tests were newly performed for JIS S45C (0.42%C) steel. Thereafter, the model effectiveness has been discussed on the basis of numerous data reported by other researchers, resulting in an overall correlation coefficient of 0.940. Finally, the model outcomes derived from a dislocation energy viewpoint have presented a good agreement with the experimental trend.

Preparation of Superhydrophobic Materials and Establishment of Anticorrosive Coatings on the Tinplate Substrate by Alkylation of Graphene Oxide

Corrosion of structural parts not only reduces the service life of the equipment but also causes safety accidents, so building a long-lasting anti-corrosion coating on its surface is the key to solving this problem. Under the action of alkali catalysis, n-octyltriethoxysilane (OTES), dimethyldimethoxysilane (DMDMS), and perfluorodecyltrimethoxysilane (FTMS) hydrolyzed and polycondensed co-modified graphene oxide (GO), modified to synthesize a self-cleaning superhydrophobic material fluorosilane-modified graphene oxide (FGO). The structure, film morphology, and properties of FGO were systematically characterized. The results showed that the newly synthesized FGO was successfully modified by long-chain fluorocarbon groups and silanes. FGO presented an uneven and rough morphology on the substrate surface, the water contact angle was 151.3°, and the rolling angle was 3.9°, which caused the coating to exhibit excellent self-cleaning function. Meanwhile, the epoxy polymer/fluorosilane-modified graphene oxide (E-FGO) composite coating adhered to the carbon structural steel's surface, and its corrosion resistance was detected by the Tafel curve and EIS impedance. It was found that the current density of the 10 wt% E-FGO coating (Icorr) was the lowest (1.087 × 10-10 A/cm2), which was approximately 3 orders of magnitude lower than that of the unmodified epoxy coating. This was primarily due to the introduction of FGO, which formed a continuous physical barrier in the composite coating and gave the composite coating excellent hydrophobicity. This method might provide new ideas for advances in steel corrosion resistance in the marine sector.

Regulation on Annealing Multiscale Laminar Structure and Mechanical Characteristics of Plain Medium Carbon Steel by Warm Pre-deformation Extent

Regulation on Annealing Multiscale Laminar Structure and Mechanical Characteristics of Plain Medium Carbon Steel by Warm Pre-deformation Extent

Buttering for FSW: Enhancing the fracture toughness of Al-Fe intermetallics through nanocrystallinity and suppressing their growth

The formation of intermetallic compounds (IMCs) is an inevitable phenomenon during friction stir welding (FSW) of dissimilar metals. Majority of approaches that have ever been used to control the IMC thickness during FSW have been process-based. In the present study, the objective was to develop a novel metallurgical approach to control the growth and microstructure of AlFe IMCs during FSW. To do so, the faying surface of a structural carbon steel (CS) was buttered with stainless steel (SS) prior to the FSW process. The joints were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study the intermetallic compounds. Tensile specimens with holes in the joint area were prepared and tested. The fracture surfaces of the specimens were studied by SEM. The analyses showed that the buttering caused the tensile strength and the fracture elongation to increase by 60 % and 250 %, respectively. SEM and TEM results revealed that there were two mechanisms responsible for this improvement. First, the thinning of the IMC layer and second, the nano-crystallinity of the IMC. The underlying physical phenomenon in controlling the IMCs thickness by this approach is discussed, highlighting the mechanisms by which the mechanical properties are enhanced. The alloying elements Cr and Ni introduced by the buttering technique were found to play the major role in controlling the thickness and nano-crystallinity of the IMC layers in the FSW of Al to St. It was found that the harmful intermetallic compounds in FSW of dissimilar metals can be effectively controlled by the alloying elements imparted through buttering before FSW.

Electrochemical Study of a Hydrophobic Film of γ-Al2O3/Hdtms on Low Carbon Steel

The corrosion phenomenon affects several low carbon steel structures leading to excessive expenditure on coatings and other alternatives. However, the coatings used usually contain compounds that pollute the environment. Therefore, environmentally friendly, economical and transparent coatings or films have been developed. The sol-gel method is a reliable way for the development of anticorrosive films, as is the case of alumina or silica films. In this work, the protective capacity of an alumina/HDTMS film was studied. The alumina film was sintered at 350, 450 and 550 °C and then the 1% HDTMS film was deposited. The protective ability of the γ-Al2O3/HDTMS film was evaluated by Electrochemical Impedance Spectroscopy (EIS) and Potenciodynamic Polarization Curves (PDP). The electrochemical results showed that the Al2O3/HDTMS film provided better protection compared to the metallic substrate. The contact angle degree was measured and determined that the sintered alumina/HDTMS films showed hydrophobic and superhydrophobic properties.

Inhibition of microbial extracellular electron transfer corrosion of marine structural steel with multiple alloy elements

The microbial corrosion of marine structural steels (09CrCuSb low alloy steel (LAS) and Q235 carbon steel (CS)) in Desulfovibrio vulgaris medium and Pseudomonas aeruginosa medium based on seawater was investigated. In the D. vulgaris medium, the weight loss and maximum pit depth of 09CrCuSb LAS were 0.59 and 0.56 times as much as those of Q235 CS, respectively. Meanwhile, in the P. aeruginosa medium, the values were 0.53 and 0.67 times, respectively. Compared to Q235 CS, 09CrCuSb LAS contains more alloy elements (Cr, Ni, Cu, Al and Sb), which led to obvious inhibition of sessile bacteria growth but had no effect on planktonic bacteria. The number of live sessile cells on the 09CrCuSb LAS surface was 23.4 % and 26.9 % of that on the Q235 CS surface in the D. vulgaris medium and P. aeruginosa medium, respectively. Fewer sessile cells on the steel surface led to a lower extracellular electron transfer (EET) rate so that less corrosion occurred. In addition, the combined effect of alloying elements on grain refinement and passive film formation also improved the anti-corrosion property of the steels.

Failure analysis and finite element assessment of a torsion spring

The torsion spring is an important component for vehicle steering system. The torsion spring in this study was manufactured using high quality carbon structural steel. In order to study the failure mechanism of the spring, a series of experiments were carried out. All the collected evidences indicated that the spring fracture was due to fatigue crack propagation. At the same time, an obvious machining defect was observed on the inner surface of the ring. There are two crack initiation regions which are located at the areas near and opposite side of the machining defect. Under the cyclic loading induced by the repeated turning, the crack propagated and fractured finally. In order to analyze the effect of the machining defect on the fatigue failure, a computed tomography experiment was conducted. The precise characters of the defect were measured by computed tomography experiments. Then a finite element model was established according to the actual defect size and the stress distribution of the torsion spring was analyzed. The results showed that the local stress of the spring and the area of stress concentration are closely related to the machining defect and the gap between the spring and the two cylindrical objects. Under the actual condition of the torsion spring in service, the severe stress was located on the fracture location, which indicating that the machining defect is the efficient cause of spring failure.

Cracking failure analysis on a high-frequency electric resistance welding pipe in buried fire water pipeline

Leakage of a buried fire water pipeline occurred after in service of 15 years. It was manufactured from a Q235B carbon structural steel plate by high-frequency electric resistance welding. The water pressure increased from 0.8 MPa at a normal operating condition to 1.2 MPa at the tube burst moment. Cracks propagate along the weld and incomplete fusion defects are observed. This paper aims to explore the cracking failure through a combination method of experimental tests and theoretical analysis. The metallographic analysis clearly shows that the crack is located in the fusion zone and grains are coarse in that zone. Mechanical property tests indicate tensile properties of the anti-corrosion layer meet requirements. Finite element analysis reveals that the pipeline with an incomplete fusion can safely operate under a pressure of 0.8 MPa, while fracture occurs under the pressure of 1.2 ∼ 1.3 MPa. The results indicated that the deep unfused defect of the welded joint was the root cause of cracking, and selective seam weld corrosion also played an important role. The failure progress and mechanism were discussed in details.

Effect of plastic deformation on structure and hardness of carbon steels

The microstructure and hardness of pearlitic steels with different carbon content after plastic deformation with different degrees of deformation have been studied. It is shown that with increasing degree of plastic deformation their hardness increases, structural changes are accompanied by grain refinement, crushing of cementite plates and diffusive redistribution of carbon from the surface to depth, as a result of which the steel surface is impoverished with carbon and the main contribution to strengthening of steels is made by grain boundary and dislocation mechanisms.

Research on Adhesion and Properties of Composite Coating on Aluminized Carbon Steel

In this paper, we studied the adhesion and properties of the composite coating on aluminized carbon steel. The part of the review introduces the concept and application of aluminizing technology and composite coating on carbon steel, and the related research is summarized. In the professional content section, the aluminizing process of carbon steel, the preparation method and characteristics of the composite coating, and the evaluation method of composite coating performance are introduced. In the main body, we focused on the research content of aluminized structure and corrosion behavior of carbon steel and studied the adhesion, corrosion resistance, wear resistance, thermal stability, and microstructural properties of composite coatings on aluminized carbon steel. In addition, this study includes the bonding mechanism between the composite coating and the substrate, the corrosion protection mechanism of the composite coating, the wear resistance mechanism of the composite coating, the thermal stability of the composite coating, and the factors affecting the adhesion, corrosion resistance, wear resistance, thermal stability and microstructure of the composite coating. The results show that the composite coating after aluminizing treatment can effectively improve the surface properties of carbon steel. Different preparation methods and process conditions have a significant effect on the performance of the composite coating. This study is of great significance for understanding the properties and preparation of composite coatings after aluminizing treatment of carbon steel.

Определение оптимальных технологических параметров процесса очистки деталей в погружных моечных машинах

Cleaning and washing contaminated surfaces of machine parts is relevant in the repair industry. Improving the efficiency of the process of cleaning metal parts is possible using a combination of submersible, jet and ultrasonic methods. The variety of designs of washing machines and installations using different cleaning methods requires the determination of optimal technological parameters and process modes, as well as the identification of an effective washing solution. For this purpose, an experiment was carried out on the process of cleaning metal parts from the remnants of cutting fluids (coolants) in submersible washing machines using ultrasonic vibrations. Solutions of dimer, labomid, and soda ash were studied to clean metal parts from coolant residues. To intensify the process of washing metal parts, an ultrasonic unit UZDN-A with a constant oscillation frequency was used. The degree of purification of metal parts was estimated by the ratio of the mass of the pollutant removed from its surface to its initial mass, in percent. The obtained mathematical models of the degree of cleaning of metal parts (for grades of structural carbon steels and non-ferrous metals) from coolant made it possible to determine the optimal technological parameters: concentration of cleaning solutions 15 to 20%; working temperature for dimer - 20 to 30°C, for labomid - 70 to 80°C, for soda ash - 80 to 90°C. It has been established that the most energy-efficient and safe cleaning solution is a dimer, and the use of labomid for ultrasonic cleaning is not advisable due to its increased foaming. It was also found that the time of washing (the presence of metal parts in the machine) and the amount of oil on the surface of metal parts do not significantly affect the degree of cleaning.

Shear strength diagnostics of machine parts

This study presents an effective non-destructive method for determining the ultimate shear strength of parts made of structural carbon and alloy steels. The shear strength was determined using the method of controlled part indentation. In addition, a new material characteristic – a shear hardening modulus – is proposed. The experimental study was carried out using an IR 5143-200 software and hardware complex for metal testing and a double-shear testing device. Steel samples of the following grades were examined: steel 10, 20, 35, 45, 20Kh, 40Kh, 25KhGT and 30KhGSA. The value of plastic hardness was used as a strength characteristic due to its advantages over other hardness values. The conducted experiments found a significant discrepancy (up to 20%) between the reference and experimental values of shear strength. Dependencies for determining the shear strength of structural carbon and alloy steel samples were obtained. The accuracy of these dependencies was determined to be sufficient for engineering calculations both according to the obtained experimental results and literature sources. The error associated with shear strength determination does not exceed ±5%. In addition, the paper provides some types of safety parts that can be destroyed by shear loads. The underestimated reference values of the ultimate strength can lead to increased unrealizable safety margins and, as a result, an increase in the specific metal amount of joints. The proposed non-destructive method for shear strength determination exhibits the accuracy sufficient for engineering practice and can be used when manufacturing, operating and repairing various machine parts and units.

Effect of Cr3C2 Content on the Microstructure and Wear Resistance of Fe3Al/Cr3C2 Composites

In this paper, an engine piston ring coating comprising composite material of Fe3Al and Cr3C2 mixed powder was prepared by laser cladding onto carbon structural steel. The microstructure and tribological properties of the cladding materials were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and wear tests. The influence mechanism of the Cr3C2 content in cladding powder was studied. During the process of wear, the soft Fe3Al/Fe2AlCr matrix is first ground off, and the hard Cr7C3 phase initially supports the abrasive surface before being worn away into hard particles, resulting in abrasive wear. With the increase in Cr3C2 content, the hardness of the cladding layer increases, the proportion of the Cr7C3 phase increases, and the morphology changes from a sparse network to a dense floccule. Of the cladding layers with different Cr3C2 content, the 15 wt.% Cr3C2 cladding layer had the lowest friction coefficient, and the 25 wt.% Cr3C2 cladding layer had the lowest wear rate. The low wear rate of the 25 wt.% Cr3C2 cladding layer can be attributed to the fact that adhesive wear does not easily occur and the fine microstructure of the strengthening phase, which facilitates better separation in the grinding surfaces.

The Influence of Carbides on Atomic-Scale Mechanical Properties of Carbon Steel: A Molecular Dynamics Study

Pearlite is an important structure in carbon steel; however, the influence mechanism of carbides in pearlite on its mechanical properties and microstructure evolution has not yet been fully elucidated. In this work, a ferrite-carbide composite model with various carbide types was constructed to investigate the influence of carbide types via a uniaxial compression deformation using classical molecular dynamics simulations. It was found that the carbide type had little effect on the compressive elastic modulus, but a more obvious effect on the yield strain, yield stress, and flow stress. The maximum compressive elastic modulus was in the Fe2C model, with 300.32 GPa, while the minimum was found in the Fe4C model at 285.16 GPa; the error was 5.32%. There were significant differences in the yield stress, yield strain, and flow stress of the ferrite-carbide model according to the stress-strain curve. Secondly, the type of carbide used affected its elastic constant, especially the bulk modulus and Cauchy pressure. The maximum bulk modulus of the Fe4C model was 199.01 GPa, the minimum value of the Fe3C model was 146.03 GPa, and the difference was 52.98 GPa. The Cauchy pressure calculation results were consistent with the yield strain trend. Additionally, the effective elastic moduli of the composite system were used to verify the accuracy of the calculation results of this work. Thirdly, ferrite-carbide interfaces could act as a resource for dislocation emission. The initial stacking fault forms at ferrite-carbide interfaces and expands into ferrite. The dislocation type and segment in the ferrite-carbide model were significantly different due to the type of carbide used.

Simulation of dynamic contact during shot blasting of parts

Shot blasting consists in hardening of the parts surface layer or workpieces with a stream of solid particles, mainly in the form of hardened steel balls. The purpose of the work is to develop and test a method for calculating the parameters of an elastic-plastic dynamic contact during shot blasting of parts based on mathematical modeling. The research technique is based on the consideration of a three-stage model of workpiece deformation under elastic-plastic impact by a steel spherical indenter. At the initial stage, the deformation is carried out elastically. Then, under some dynamic load, in the near-surface layer of the impacted body, a region of plastic state is generated, surrounded by an elastically deformable material. With a further increase in the dynamic load above a certain characteristic value, the region of the plastic state comes to the surface of the impacted part. Subsequently, the process is characterized by elastic-plastic indentation of the indenter (shot) into the impacted part. A method for upper calculating estimate the parameters of the dynamic contact of steel shot with parts based on the energy theory of elastic-plastic impact has been developed. To separate the elastic and plastic components of the deformation energy, the velocity recovery factor upon impact was used. The deformable material is accepted at the final stage of deformation as an ideal elastic – plastic material obeying the Prandtl’s scheme. Analytical dependencies convenient for practical use are obtained, which allow one to make calculating estimate of the depth and diameter of the imprint. Estimated calculations of the depth of the indentation depending on the speed of exposure to steel shot for shot blasting of a number of structural carbon steels have been performed. The results of the research can be used in the educational process in the preparation of engineering personnel of the machine-building profile, as well as in engineering practice.

STUDI KEKUATAN TARIK, KEKERASAN, DAN STRUKTUR MAKRO PADA HASIL PENGELASAN SMAW MATERIAL BAJA KARBON RENDAH MENGGUNAKAN E6013 DENGAN PENAMBAHAN KROM

This study aims to determine the effect of adding chromium to the SMAW process on the tensile strength, hardness value and macro structure of low carbon steel welded joints. The welding process in this study used the E6013 electrode with the addition of chrome and welding without the addition of chrome to compare the results of tensile tests, hardness tests and macro structures. After the welding process, continued with the manufacture of tensile test specimens with 3 specimens each for each variation, the manufacture of hard test specimens and macro structures. In the tensile test results, the tensile strength values ​​between specimens with the addition of chromium and without the addition of chromium (non) did not show a significant difference, the average tensile strength values ​​were 38.33 kg/mm² and 38.67 kg/mm², respectively. The addition of chrome to the SMAW process has been shown to have an effect on the hardness value of low carbon steel welded joints. The hardness value of the specimen with the addition of chrome is greater with an average hardness value of 166.8 VHN in the weld metal area than the specimen without the addition of chromium (non) with an average hardness value of 150.97 VHN. In the macro structure, between the specimens with the addition of chromium and without the addition of chromium (non) there was no porosity.