Materials and Metallurgical Engineering

The creep properties of a nuclear-grade type 316 (L) stainless steel (SS) alloyed with nitrogen (316L (N) SS) and its weld metal were studied at 873 and 923 K in the range of applied stresses from 100 to 335 MPa. The results were compared with those obtained on ...

ABSTRACT Filler material choice for repair welding of stop valve spindle of thermal power plant by-pass pipeline was presented in this paper. Repair welding of the stop valve spindle was necessary because of plant operating problems due to very frequent localized damage appearance in the form of erosive wear on it. For this purpose it was necessary to choice appropriate filler material with high wear resistance characteristic. Experimental investigation and testing (hardness measurement, chemical composition analysis and microstructural investigation) of prepared specimens after welding simulation with different kind of filler material was performed. On the basis of obtained results it was recommended procedure for application of the filler material with generally preferable characteristic.

В отходах пирометаллургического производства меди накоплено значительное количество отвальных шлаков. Даже при среднем содержании меди в них 0,30–0,80 %, видно, что потери металлы
составляет значительных. В этой связи задача создания  рациональной и комплексной технологии переработки шлаков и промпродуктов медного производства является весьма актуальной. В статье рассмотрен инновационный метод снижения потерь меди со шлаком. Для проведения этого исследования
использованы восстановительно-сульфидирующих комплексы (ВСК), состоящие из клинкеров цинкового производства и хвостов обогатительных фабрик АГМК. Полученные результаты  показывает, что внедрение данной технологии в промышленность позволит повысить комплексности использование сырья.

Metallurgical manganese ore samples from Ka’oje
(Nigeria) were enriched to higher Metallurgical grades during
wet gravity separation techniques which included Jigging and
Tabling operations. As-mined samples S1 (36.83%MnO), S2
(47.85%MnO), S3 (58.85%MnO) and S4 (54.96%MnO) were
dressed and screened to -780+500 μm, -500+355μm, -355+250
μm, -250+192 μm and -192 μm particle size ranges. Obtained
Jigging test concentrates assayed 51.54% MnO minimum
recovery level with an enrichment ratio (ER) of 1.02; while
Tabling operation concentrates assayed 91.11% MnO
maximum recovery and 1.14 ER value. These responses
demonstrated the suitability of the two techniques in raising the
enrichment levels of the ores for better applications and higher
economic gains.

The twentieth century was the century in which metallurgy evolved from a handicraft to an engineering science. In the last thirty years of that century and, in particular, the twenty-first century, the world's steel industry, including the Chinese steel industry, are facing with new challenges and opportunities for development. New propositions have been put forward mainly by developments of the times, advances in science and technology, and changes in the global ecology- environment. Where further development of the steel industry is concerned, these propositions cannot be resolved simply by providing answers to such individual issues as quality and variety. A more important and forward-looking proposition calls for the comprehensive resolution of a number of major integrated tasks such as the enhancement of market competitiveness-including such aspects as production costs, materials consumption, energy consumption, production efficiency and investment benefits-and issues of sustainable development, such as the availability of materials and energy resources, and ecological harmony. These propositions for the steel industry in the new century cannot be solved by focus- ing studies simply on the fundamental sciences (such as thermodynamics, kinetics of chemical reactions, etc.) and the applied sciences (such as the transport phenomena and reaction engineering), but have to be resolved in their entirety by studying the functions, structure, efficiency, and other process engineering issues of metallurgical manufacturing.

The monograph presents theoretical approaches and concepts, analytical reviews, practical solutions in specific areas of metallurgy.
The publication may be interesting to Uzbek and foreign scientists, managers and specialists of factories and metallurgical organizations, engineers, technologists, teachers, masters and students of higher educational institutions.
Responsibility for the authenticity and accuracy of citations, names, titles and other information, as well as for compliance with intellectual property laws lies with the authors of published materials.

Welding is a widely used process in industry because welding techniques have some striking features which are included in this project. In other way of saying, welding techniques will be so important in human life in the future because of their unique specialties. For this reason, researches and studies on welding are increasing day by day.
Welding is used in different areas in industry and it has various features. Welding is especially used in the manifacturing area, as a connector between materials in the existence of heat and pressure (with or without additional materials). The main targets in this process are; lowest cost, highest satisfaction in performance and longest life.
In this project, the importance of choosing a suitable production regarding to the intended features and how to improve the mechanical features, tried to be explained. Therefore, the welding process which is going to be applied to the materials which has different metal content, are virtually modelled by using Ansys Workbench software.
Parameters as, used materials and chosen welding techniques within this project are widely explained.  Experimental studies were done in order to help the project to enlighten the future studies and to make the project based on numerical data (simplifies prooving). In the other parts of the experimental studies, welding process is applied to the materials which have different metal contents by using Ansys Workbench software. Modelling a material using different welding techniques before production gives  more practical and more proactive vision.

Production of corrosion inhibitor from Euphorbia heterophylla leaf extract via Maceration extraction method using ethanol, and estimation of its inhibition efficiency on mild steel in HCl medium at different pH levels, using weight loss method was being investigated.
The research was carried out using an environment of varying pH level, ranging from ph1.75-ph4.0; and varying concentration of extract from 4ml- 16ml in a 500ml acid environment. The results obtained reveal that the more acidic an environment, the higher the inhibition efficiency of the plant extract. It was observed that Euphorbia heterophylla leaf extract is an efficient anodic inhibitor in the acidic environment; The corrosion inhibition efficiency increased to an optimum of approximately 90% for 16ml extract in 0.5M HCl. The results obtained shows that the plant extracts inhibited the corrosion process by a spontaneous physical adsorption mechanism.
Key words: Euphorbia heterophylla leaf extract, HCl medium, weight loss method.

High-entropy alloys (HEAs) have recently become a vibrant field of study in the metallic materials area. In the early years, the design of HEAs was more of an exploratory nature. The selection of compositions was somewhat arbitrary, and there was typically no specific goal to be achieved in the design. Very recently, however, the development of HEAs has gradually entered a different stage. Unlike the early alloys, HEAs developed nowadays are usually designed to meet clear goals, and have carefully chosen components, deliberately introduced multiple phases, and tailored microstructures. These alloys are referred to as advanced HEAs. In this paper, the progress in advanced HEAs is briefly reviewed. The design strategies for these materials are examined and are classified into three categories. Representative works in each category are presented. Finally, important issues and future directions in the development of advanced HEAs are pointed out and discussed.

Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 – St.20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St.20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on in-strumented Charpy machine), analysis of the chemical composition of corrosion products – deposit and the microstructural characterization by optical and scanning electron microscopy – SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.

Many efforts have been made to understand the effects of hydrogen on steels, resulting in an abundance of theoretical models and papers. However, a fully developed and practically applicable predictive physical model still does not exist industrially for predicting and preventing hydrogen damage. In practice, it is observed that different types of damages to industrial boiler components have been associated with the presence and localization of hydrogen in metals. In this paper, a damaged boiler tube made of grade 20 – St.20 (or 20G, equivalent to AISI 1020) was investigated. The experimental research was conducted in two distinctive phases: failure analysis of the boiler evaporator tube sample and subsequent postmortem analysis of the viable hydrogen embrittlement mechanisms (HE) in St.20 steel. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack (HTHA) during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, tube wall thickness measurement, tensile testing, hardness measurement, impact strength testing (on in-strumented Charpy machine), analysis of the chemical composition of corrosion products – deposit and the microstructural characterization by optical and scanning electron microscopy – SEM/EDX. The HTHA damage mechanism is a primary cause of boiler tube fracture. Based on the multi-scale special model, applied in subsequent postmortem investigations, the results indicate a simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen-enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. The model is based on the correlation of mechanical properties to the SEM fractography analysis of fracture surfaces.

Thermo-mechanically treated (TMT) ribbed bars modify the overall progress of failure in reinforced concrete. The ribs maintain anchorage after friction on the rest of the bar is eliminated during deformation, taking up the ultimate compressive load. This however, is inadvertently jeopardized by the stress concentration effect of the rib geometry. This paper analyses the extent to which some of the geometric forms of bar lugging affect the prevalence of ductile failure in the steel-concrete composite under monotonic loading otherwise imparted by their preconceived chemical and metallurgical constitution. Thirty pieces of two different types of rib pattern designs of Φ20 mm thermo-mechanically treated ribbed steel bars were subjected to uniaxial tensile testing. Portions of these were stripped of their lugging and subjected to the same test. The tests were repeated after corresponding parts of the same bars were annealed. The fractured surfaces were then examined with a lens for macroscopic features and using an optical microscope at X50. Fracture traits varied from microvoid coalescence ductile features to external transgranular cleavage or intergranular separation. In 28% of the samples, the origin of the fracture was traceable to the rib joints. This reduced to 20% when the samples were annealed with a corresponding average increase in strain after yield evaluated by u/ b of 14 and 8% for ribbed and machined bars, respectively. In 82% of the samples stripped of their lugging, the fracture originated from the center of the bars. This shows that under monotonic loading the presence of ribs originates a stress concentration effect that directs the fracture source to the rib nodes and corners and also reduces of the deformation available after the yield point, curtailing the reinforcing effectiveness of the bar in the steel-concrete composite even in the absence of the surface hardening due to thermo-mechanical treatment.

Problem of boiler component erosion is a very complex and present in practically all fossil fuel power plants burning low heating value coals irrespective of their particular design and operating characteristics. Major fly coal erosion accelerating factors are large amounts of abrasive components in the air-coal mixture and its high velocity. In general terms, there is a trend of implementation of appropriate erosion protection in critical place of pulverized boiler coal preparation equipment. In this paper are presented results of erosion tests provided on samples with different erosion protection materials. Erosion damage profiles of different protection materials were investigated and analyzed on tested samples.

Laboratory techniques for materials science and materials engineering education. From the discipline "Introdução aos Materiais" (Introduction to Materials) lectured at the Department of Ceramics and Glass Engineering of University of Aveiro, Portugal. Includes guidelines for laboratory report writing. In Portuguese.

Today, a large number of people access internet through their smart phones to login to their bank accounts, social networking accounts and various other blogs. In such a scenario, user authentication has emerged as a major security issue in mobile internet. To date, password based authentication schemes have been extensively used to provide authentication and security. The password based authentication has always been cumbersome for the users because human memory is transient and remembering a large number of long and complicated passwords is impossible. Also, it is vulnerable to various kinds of attacks like brute force, rainbow table, dictionary, sniffing, shoulder surfing and so on. As the main contribution of this paper, a new passwordless authentication scheme for smart phones is presented which not only resolves all the weaknesses of password based schemes but also provide robust security. The proposed scheme relieves users from memorizing and storing long and complicated passwords. The proposed scheme uses ECDSA which is based on Elliptic Curve Cryptography (ECC). ECC has remarkable strength and efficiency advantages in terms of bandwidth, key sizes and computational overheads over other public key cryptosystems. It is therefore suitable for resource constraint devices like smart phone. Furthermore, the proposed scheme incorporate CAPTCHA which play a very important role in protecting the web resources from spamming and other malicious activities. To the best of our knowledge, until now no passwordless user authentication protocol based on ECC has been proposed for smart phones. Finally, the security and functionality analysis shows that compared with existing password based authentication schemes, the proposed scheme is more secure and efficient.

Laboratory technique dealing with steel hardness for materials science and materials engineering education. From the discipline "Introdução aos Materiais" (Introduction to Materials) lectured at the Department of Ceramics and Glass Engineering of University of Aveiro, Portugal. In Portuguese.

Thick walled components such as high pressure (HP) steam turbine casings operating under high parameter conditions are subjected to a complex stress state. As a result of that stress state, some parts of HP turbine casing undergo to the creep fatigue caused by the combination of thermal fatigue resulted from repeated start/stop operation and the creep which occurs during long-term operation at high temperature and high-pressure. It is well known that domestic thermal power plants have been in use over 100000 h which means that significant cost is required not only for maintenance, but often for renewal of equipment. Based on comprehensive investigation, the results of residual life assessment of one high pressure steam turbine casing, which belongs to the older turbine generation, taking into account simultaneous action of thermal fatigue and creep, are presented in this paper. Also, the critical flaw crack size of HP turbine casing is determined because this parameter has a strong influence on casing integrity and residual life. The results of residual life assessment provide not only a basis for further maintenance, but also estimated time for reparation or renewal.

One of the key issues in high-entropy alloys (HEAs) is the development of alloys that contains only simple solid solution (SSS) phases. Researchers have proposed various parametric models to predict SSS formation. However, incorrect predictions are not uncommon. Here, we investigate the main cause of these mispredictions. It is found that the premises of most existing models do not apply to some intermetallic phases. Hence, the models cannot distinguish alloys containing these intermetallics from alloys containing only SSSs. A possible solution to this issue is proposed. With this strategy, the accuracy of existing models can be evidently improved.

This paper deals with determination of the failures causes of supporting tubes in a 350 MW fossil fuel power plant. Due to frequent fractures of supporting pipes occurring always at the same location and the ensuing reduction of the plant availability as well as substation financial losses, there was an urgent need to resolve the problem [K. Takahashi, M. Yokouchi, S.K. Lee, K. Ando, J. Am. Ceram. Soc., 86-12, 2003]-[3]. This work describes the test results and the conclusions drawn from the results.

В данной работе были рассмотрены варианты восстановления вал шестерни мельницы МШР 2700×3600. Была сконструирована 3D модель в Autodesk Inventor. Выбранный вариант восстановления увеличивает эксплуатационную производительность вал шестерни в мельницах и позволяет сократить время восстановления работы мельницы. В ходе изучения выбранного варианта был разработан технологический процесс восстановления вала шестерни.

The characteristics of continuous tempering of quenched W-Mo-V high-speed steel in the temperature range from 180°C to 770°C were determined using dilatometric method. Due to scarcity of available information in the literature, special attention was paid to evaluating the destabilization degree of retained austenite and the mechanism of its transformation during cooling from tempering temperature. The results of tests contributed to a better understanding of the complicated tempering process for this type of high-speed steel.

This paper deals with determination of the failures causes of supporting tubes in a 350 MW fossil fuel power plant. Due to frequent fractures of supporting pipes occurring always at the same location and the ensuing reduction of the plant availability as well as substation financial losses, there was an urgent need to resolve the problem [K. Takahashi, M. Yokouchi, S.K. Lee, K. Ando, J. Am. Ceram. Soc., 86-12, 2003]-[3]. This work describes the test results and the conclusions drawn from the results.

This research paper approaches a new insight toward reducing the manual, mechanical and codependent systemization as an upcoming trend for architectural sustainability and autonomous power providing. By describing some new methods of applied and tested functional features through enhancing or rearrange the properties of ordinary and composite materials in the field of build and construction, it demonstrates a new prospect of wider investments in innovative material production in architectural design and actuation. Also, reveals new methodologies for individual and non-linear autonomy to providing long-term maintenance in extreme conditions or sudden damages as a supportive capability for the used materials to be adopted in design processes.

The article discusses an innovative method of reducing the loss of gold with waste cyanide solutions. To conduct this study, chemical reagents were used that allow the removal of harmful impurities and create the optimal conditions for the complete leaching of gold-bearing ores. The results show that the introduction of this technology in industry will increase their productivity.

Microstructures of Fe–TiB2 metal-matrix-composites formed in-situ from Fe–Ti–B melts were investigated for hypo- and hyper-eutectic concentrations down to atomic-scale resolution. Special emphasis is laid on the influence of the solidification rate on particle size, morphology and distribution as well as their relation to mechanical properties. Innovative routes for the cost-effective production of stiff and ductile high modulus steels for lightweight structural applications are discussed, focusing on hyper-eutectic compositions due to their high stiffness/density ratio: firstly, very slow cooling allows the primary particles floating to the top of the cast, from which they can either be easily removed for retaining bulk material containing only fine-dispersed eutectic particles, or be kept and utilised as a wear resistant surface. Secondly, annealing of amorphous matrix material obtained from very fast solidification leads to fine dispersed nano-scaled precipitation of TiB2 particles.

The service lift of thick-walled power plant components exposed to creep, as is the case with pipelines of fresh- and reheated steam, depend on the exhaustion rate of the material Plant operation at elevated temperatures and at temperatures below designed temperatures all relates to the material exhaustion rate, thus complicating remaining life assessment, whereas the operating temperature variation is a most common cause in the mismatching of real service and design life. Apart from temperature, the tube wall stress is a significant variable for remaining life assessment, whose calculation depends on the selected procedure, due to the complex pipeline configuration. In this paper, a remaining life assessment is performed according to the Larson-Miller parametric relation for a phi 324 x 36 pipe bend element of afresh steam-pipeline, made of steel class ICr0.3Mo0.25V, after 160.000 hours of operation. The temperature history of the pipeline, altogether with the pipe bend, is determined based on continuous temperature monitoring records. Compared results of remaining life assessment are displayed for monitored temperature records and for designed operating temperature in the same time period. The stress calculation in the pipe bend wall is performed by three methods that are usually applied so to emphasize the differences in the obtained results of remaining life assessment.

In this paper test results are analyzed of the tempering process of tungsten–molybdenum high-speed cutting steel. Results are acquired by applying dilatometric, microscopic, and X-ray methods, and from hardness tests. The quenched steel was tempered by continuous heating (at the rate of 4 °C/min.) to different temperatures within the interval 180–740°C, and slowly cooled via furnace. Certain questions have generated new discoveries and appropriate explanations.

Thermo-mechanically treated (TMT) ribbed bars modify the overall progress of failure in reinforced concrete. The ribs maintain anchorage after friction on the rest of the bar is eliminated during deformation, taking up the ultimate compressive load. This however, is inadvertently jeopardized by the stress concentration effect of the rib geometry. This paper analyses the extent to which some of the geometric forms of bar lugging affect the prevalence of ductile failure in the steel-concrete composite under monotonic loading otherwise imparted by their preconceived chemical and metallurgical constitution. Thirty pieces of two different types of rib pattern designs of Φ20 mm thermo-mechanically treated ribbed steel bars were subjected to uniaxial tensile testing. Portions of these were stripped of their lugging and subjected to the same test. The tests were repeated after corresponding parts of the same bars were annealed. The fractured surfaces were then examined with a lens for macro...

In the current study, the influence of delta (δ) ferrite on the corrosion susceptibility of AISI 304 austenitic stainless steel was evaluated in 1Molar concentration of sulphuric acid (H 2 SO 4) and 1Molar concentration of sodium chloride (NaCl). The study was performed at ambient temperature using electrochemical technique—Tafel plots to evaluate the corrosive tendencies of the austenitic stainless steel sample. The as-received (stainless steel) specimen and 60% cold-worked (stainless steel) specimens were isothermally annealed at 1,100°C for 2 h and 1 h, respectively, and quenched in water. The results obtained show that the heat-treated specimen and the 60% cold-worked plus heat-treated specimen exhibited higher corrosion susceptibility than the as-received specimen, which invariably contained the highest fraction of δ ferrite particles. The finding shows that the presence of δ ferrite, in which chromium (Cr), the main corrosion inhibitor segregates, does not degrade and or reduces the resistance to aqueous corrosion of the austenitic stainless steel material.

Controlling the biodegradation of scaffolds to tune with that of the growing tissue is crucial for tissue regeneration. Although molecular weight of a polymer is known to influence its degradation, such studies have not been reported for electrospun Polycaprolactone (PCL) based composite scaffolds. In the present study, two low molecular weight PCL, 10 and 45 kDa PCL (10PCL and 45PCL) have been analyzed for their electrospun ability and biodegradation in comparison with 80 kDa PCL (80PCL) in forming pure polymeric and hydroxyapatite composite nanofibrous mats. The 45PCL and 80PCL were electro spin able but the 10PCL resulted in electro spraying of particles. However, 45PCL needed a higher concentration (20 wt.%) of polymer than the 80PCL (8 wt.%) in order to electrospin bead free uniform fibres. The fibres obtained were in the diameter range of 310±50 nm and 400±100 nm for the 45PCL and 45PCL/HA composite mats respectively. The Hydroxyapatite (HA) incorporation in the composites was confirmed through X-ray diffraction and spectroscopic methods. The 45PCL/HA composite degrades at a relatively faster rate than the 80PCL/HA composite. The electrospun mats were also found to be non cytotoxic (Live/Dead assay), commendable cellular metabolic activity (MTT assay) and good proliferation of osteoblast-like cells (HOS) as evidenced through fluorescent and scanning electron microscopy. This work demonstrated the feasibility of fabricating PCL based electrospun composite scaffolds having controlled degradation rates.

The article considers problems of reduction of magnetite with forming bivalent iron after converting copper mattes in horizontal converters. So, it has been showed what methods of reduction of magnetite until ferrous ions with different reducing agents. The magnetite in the slag is reduced with carbonaceous materials or other solid reductants. While the slag is mixed with a water cooled, metal-bladed mechanical stirrer, the reductant is reacted with the slag. As a result of stirring the reductant into the slag, the rate of magnetite reduction is highly accelerated. With the reduction, the copper separates into a copper phase as either immiscible copper, copper sulfide, or a copper-iron-sulfide matte, depending upon the initial composition of the slag.

For a requirements satisfaction in metals annually in the world more than 10 billion t of different types of minerals are taken. At the same time there is a downward tendency of content of valuable components in the extracted ores, the condition of fields worsens, and inventories practically of all types of minerals are reduced. In the modern mining industry waste of mining and metallurgical production shall be processed further in a complex, and the reagents participating in processes of their extraction shall be exposed to complete safe utilization or regeneration and return to production.