Papers by Keyword: Chemical Composition

Abstract: Actuality. The accumulation of damage due to fatigue, plastic deformation, and wear significantly reduces the service life of railway rolled metal products. The development of a fatigue crack to its critical length (main cracks) leads to failure at stress levels much lower than the material's strength limit. In industrial-grade steels, there may be chemical micro-inhomogeneity of the main element—carbon. Objective of the study: To determine the effect of chemical micro-inhomogeneity (carbon content variation of 0.02%) on fatigue failure characteristics (crack growth rate, threshold stress intensity factor, fatigue life, and critical defect size) of railway wheel steels of grades ER7 and ER8 according to EN 13262. Results. Segments of the fatigue crack growth rate (FCGR) diagram were constructed to characterize the development of fatigue cracks. The crack growth rate on the second linear section of the diagram and the critical value of the stress intensity factor at which failure occurs were determined. It was found that on the linear portion, which describes the crack growth process, the indicator values vary slightly (up to 10%), indicating that the crack growth rate differs minimally between these steels. Fatigue life—the number of loading cycles until failure—was also determined, and the critical size of the fatigue crack was calculated. A carbon content fluctuation within 0.02% by mass leads to a reduction in fatigue life by approximately 10% for ER7 steel and about 20% for ER8 steel, and a reduction in the critical crack size by around 8% for ER7 and 18% for ER8. Conclusion. Chemical micro-inhomogeneity with carbon content variation in the range of 0.02% in ER7 and ER8 railway wheel steels leads to a decrease in fatigue life (as determined from specimens with cracks) and in the critical size of the fatigue crack (up to 20%). However, it has only a minor effect (about 10%) on the stable fatigue crack growth rate.

Abstract: Relevance of the work. One of the key challenges currently faced by manufacturers of steel wire rod for welding applications worldwide is achieving maximum plasticity in the metal before delivery to hardware plants. This need arises due to the ongoing technological advancements in hardware plants and the integration of modern equipment capable of producing wire at high drawing speeds with significant degrees of unit deformation. Such processes demand high-quality raw materials (wire rod). Another crucial aspect is ensuring a high-quality surface for the welding wire, free from microcracks and hard inclusions. These defects can negatively impact the welding process by increasing metal spatter, causing electric arc instability, and leading to critical defects in welded joints, such as cavities and cracks. Rational microstructural design is a key principle in producing highly plastic wire rod for the efficient manufacturing of solid-section welding wire from low-carbon alloy steels. The presence of hard components (such as martensite, bainite, or their mixtures) in the wire rod’s structure is undesirable, as they increase the risk of metal failure during intensive cold deformation by drawing. Minimizing these hard phases remains an urgent scientific and practical challenge. The aim of the study is to determine the mechanism of martensite grains formation during slow cooling of low-carbon alloy steel grade CrMoV1Si wire rod, used for producing welding wire, from the austenitization temperature to room temperature. Material and methodology. The material used in this study was steel with the chemical composition (in wt.%) 0.08C–1.30Mn–0.54Si–1.06Cr–0.54Mo–0.24V–Fe_(balance). The samples were subjected to thermal cycles using an automated Gleeble 3800 thermal deformation simulation system. The thermal cycle involved heating the samples to the temperature required for complete austenitization, holding them at this temperature, and then continuously cooling at controlled rates of 0.20, 0.10, and 0.05 °C/s to room temperature. Metallographic analysis was conducted using an optical microscope and a scanning electron microscope. The hardness of individual structural components was measured using a microhardness tester following the standard method. The chemical composition of the phases was determined by energy-dispersive X-ray spectroscopy and Auger electron spectroscopy. Results. The study established an anomalous increase in the volume fraction of austenite shear transformation products in CrMoV1Si steel after continuous slow cooling at rates of 0.20–0.05 °C/s, at the same time, martensite had a relatively high carbon content (up to 1.6 wt.%). The authors attribute this microstructural evolution to dynamic changes in the chemical composition of individual phases during cooling, primarily due to the partitioning of carbon and other alloying elements between the α and γ phases, as confirmed experimentally. Based on the obtained results, a mechanism has been proposed for the formation of high-carbon martensite grains in low-carbon alloy steel wire rod during slow cooling from the austenitization temperature to room temperature.

Abstract: This study presents the Assessment of the structural, compositional, and performance characteristics of the obtained fiber from Bauhinia Racemosa (BR). Epoxy composites reinforced with Bauhinia Racemosa fiber (BRF) Were produced through the use of the compression molding process. Chemical analysis revealed that BRF contains a high percentage of cellulose, while exhibiting relatively low amounts of lignin, ash, and wax. Mechanical performance was assessed through tensile, flexural, and impact strength tests. Examination of the fracture surfaces using Scanning Electron Microscopy (SEM) revealed that fiber pull-out was one of the main modes of failure, matrix cracking, and fiber breakage.

Abstract: The main interest in Additive Manufacturing, specifically Powder Bed Fusion - Laser/Metal (PBF-L/M) technology relates to its ability to produce complex components with significant weight reduction using the minimum material required by the application. Being the aerospace sector one of the sectors where this technology has more interest and applications, particularly the Ti-6Al-4V alloy, ensuring the quality of parts thus the processed material becomes more critical since the criticality of the using powder affects directly.This study aims to analyze the effect of powder reuse on titanium alloy Ti‑6Al‑4V manufactured by PBF-L as well as the material processability when a significant processing parameters optimization is conducted by modifying the laser scan speed for the process efficiency by keeping the energy density without compromising the material performance. The chemical composition and the physical properties of specimens manufactured with virgin powder and after several build jobs are analyzed and compared to assess the influence of virgin and reused powder material on the consolidated material.Furthermore, the manuscript also provides perspectives and recommendations to enable AM users to develop a well-defined and standard powder reuse process to maintain the desired characteristics' consistency. By optimizing the laser parameters, both manufacturing efficiency and material behavior can be improved. Fatigue and tensile testing should be done too to prove this after several heat treatments in different conditions, to improve alloy properties and minimize residual stress at the same time.Finally, it is worth mentioning that the development carried out around this dual-phase Ti alloy has contributed to some parts manufacturing of structural components for aerospace applications. Hence, the material performance has a long journey ahead of that industry.

Abstract: The scope of generation, accumulation and use of ash and slag waste of thermal power plants in different countries has been analyzed. The results of the study of the phase, mineralogical and chemical composition of ash and slag waste obtained with the dominance of solid and liquid fuel in the energy balance have been presented. It has been shown that the newly formed and previously accumulated ashes and slags of thermal power plants, with their correct and effective use, are a powerful source of expansion of raw materials in various industries. The existing methods of using ash and slag waste, which have been developed based on their mineral composition and the content of trace elements and impurities in them, have been considered. The most effective application of these wastes is in the construction industry, as well as when used as a raw material for obtaining compounds of rare metals, for example, vanadium.

Abstract: Water treatment sludge (WTS) is a by-product produced in the process of water treatment plants (WTP). It is estimated that an ordinary WTP produces over 10,000 tonnes of WTS per day, which has become a major concern in the management of WTS. Numerous previous studies have been accomplished to determine a safe disposal method and the potential reuse of WTS. In most investigations, material characterisation was the adopted method. It is known that each WTP produces different chemical composition of WTS according to raw water intake and the treatment process. The aim of this paper is to examine the chemical composition of WTS in the WTP at Melaka. The WTS sample is collected from WTP after the pressing process, where large amounts of water have been removed. The sample is tested using the Scanning Electron Microscopy with energy dispersive X-ray (SEM-EDX) and X-ray Diffraction (XRD). The SEM-EDX results revealed that by weight percentage (%), WTS contains zirconium (Zr) (28 to 46%), oxygen (28 to 40%) and carbon (7 to 26%). Aluminium and silicon have weight percentages ranging from 7 to 8%. The outcomes are then confirmed by XRD, which showed the high intensity of Zr and α-Zr at approximately 35.3 and 36.1. of 2θ. Based on these findings, the suitable and potential reuse of WTS would be the extraction of Zr. However, further research is required to verify the consistency of Zr in WTS.

Abstract: As a producer of aluminium coils in a broad variety of applications AMAG faces challenges to control and monitor a long, multi-step production process with an immense number of parameters. Identifying impactful parameters or outliers becomes increasingly difficult when considering multiple production steps. Monitoring many coils over a big set of parameters manually is difficult, time consuming and error-prone and thus an unreasonable endeavour. To support employees in technology- and process-oriented domains, AMAG data scientists develop analytical tools for data exploration and data analysis. Based on material data containing mechanical properties in deformation tests, chemical composition, hot rolling temperature, intermediate annealing, and pre-heating duration we propose a framework of data collecting mechanisms and subsequent statistical methods to analyse and visualise data. The produced visuals can be interactively explored by material experts to gain better understanding of the complex interactions in production parameters and the effect on mechanical properties. Incorporating many coils at once, the framework offers a means to point out problems in process stability. A collaboration and a feedback loop between material scientists and data scientists is key to further develop advanced analytical methods.

Abstract: The quality of silica sand used in composite cements is crucial. A significant factor is the dilation of sand grains. In this study, two types of silica sands from related deposits were examined to identify differences in properties, such as grain size and shape, chemical purity (using SEM and XRFS), and their impact on dilation. It was found that the location supplying coarser-grained sand exhibited higher chemical purity but also 19.8% higher dilatation.

Abstract: Indonesia has been facing COVID-19 since March 2020, causing significant problems for public health. Indonesia is trying to solve this problem, and the vaccination program began in January 2021. Several obstacles include public acceptance of the composition of the COVID-19 vaccine. We systematically searched peer-reviewed studies during 2020-2022, examining analyses of the Chemical Composition of the COVID-19 Vaccine authorized in Indonesia. We also explored the related information from the official body. Finally, we constructed a short review of the public acceptance of the vaccine focusing on the chemical composition. All COVID-19 vaccines are intended to induce humoral and cellular immunity toward infection. The antigen causes this as an active ingredient of the vaccine. The vaccine also contains adjuvants, and some other chemicals are required. The expansion aims to maintain the content of the vaccine, strengthen the body's reaction to the vaccine, and facilitate the administration process. But there are concerns about the risk of unintended effects of the substances used. This perception includes those that hinder the implementation of COVID-19 Vaccination in Indonesia. There is a need to disseminate information and education about the vaccine composition so that the optimal vaccination program benefits the community.

Abstract: ST 41 steel is a low carbon steel which can be used for propeller shafts because it is categorized as a carbon steel permitted by BKI with a tensile strength requirement of 400 to 800 N/mm². The propeller shaft deteriorates due to its surface frequently rubbing against the bearings. Carburizing is a technique used to increase the surface hardness by heating the specimen in a closed container containing mixture of carbon and a catalyst. The main objective of the subsequent quenching and tempering processes is to increase toughness and ductility while eliminating residual stresses. The achieved results are based on tests conducted on ST 41 steel with a measured carbon layer thickness of 229.12 μm, namely coal carbon media. Based on the results of wear tests, coal carbon media possesses a minimum value of 6.38287E-05 mm²/kg. In torsional testing, the maximum shear stress value for carbon media made from coconut shell charcoal is 429.79 MPa. When measuring hardness, coal carbon media has the highest value, which is 340.918 VHN. And metallographic testing shows that pearlite is the main phase in coal carbon media. The media with the most carbon is coal carbon, which 0.729% on the surface of the steel. Keywords: St 41 Steel, Carburizing, Wear, Hardness, Torsion, Chemical Composition, Micrograph.