This project mainly investigated how the niobium(Nb) content influences the microstructure and mechanical properties of grey cast iron. Considering the mechanism, the study also analyzes the relationship between microstructure and mechanical properties. Generally, the work is based on 127 test bars/samples from two cylinder heads and three batches of plates, which were studied by measuring tensile strength, microhardness, graphite size, carbide amount and chemistry. The result data has been evaluated with statistical methods. The experiments mainly included the preparation of the samples for test and analysis. The mechanical properties in this study are evaluated by the tensile strength of the grey cast iron. Meanwhile, various microscopies were applied to observe how niobium and cooling rate influence the microstructure. Finally, from the analysis results, it tells that the niobium does affect the tensile strength of grey cast iron. Higher the niobium content is, higher the tensile strength is. The computed result based on the data also shows niobium’s strong effect. The faster cooling rate will increase the tensile strength and pearlite microhardness of grey cast iron as well. The carbide amount of grey cast iron can be increased by the addition of niobium content. Furthermore, some future work needs to be done to explain the unsolved problem in this result. The reasons of why a specific position A-2-d of plates has high values of tensile strength demand more microstructure investigation. For the niobium influence, more experiments and data containing a larger range of niobium content also need to be done to prove the mathematics results in this report. / Detta projekt undersökte huvudsakligen hur innehållet av niob (Nb) påverkar gråstålens mikrostruktur och mekaniska egenskaper. Med tanke på mekanismen analyserar undersökningen även förhållandet mellan mikrostruktur och mekaniska egenskaper. Arbetet baseras i allmänhet på 127 provstänger / prover från två cylinderhuvuden och tre satser av plattor, vilka studerades genom mätning av draghållfasthet, mikrohårdhet, grafitstorlek, karbidmängd och kemi. Resultatdata har utvärderats med statistiska metoder. Experimenten inbegriper huvudsakligen beredningen av proven för test och analys. De mekaniska egenskaperna i denna studie utvärderas av gråstålets draghållfasthet. Under tiden applicerades olika mikroskopier för att observera hur niob- och kylhastigheten påverkar mikrostrukturen. Slutligen, från analysresultaten, berättar den att niobet påverkar draghållfastheten hos grågjutjärn. Ju högre niobinnehållet är, desto högre är draghållfastheten. Det beräknade resultatet baserat på data visar också niobins starka effekt. Den snabbare kylhastigheten ökar också draghållfastheten och pearliten-mikrohårdheten hos grågjutjärn. Karbidmängden av grågjutjärn kan ökas genom tillsats av niobhalt. Vidare måste vissa framtida arbeten göras för att förklara det olösta problemet i detta resultat. Skälen till varför en specifik position A-2-d av plattor har höga dragkrafter kräver mer mikrostrukturundersökning. För niobinpåverkan måste fler experiment och data som innehåller ett större antal niobinnehåll också göras för att bevisa matematikresultaten i denna rapport.

Cylinder liners in heavy-duty truck engines are subjected to intense vibrations and may sustain damage from the cavitation of bubbles in the coolant liquid, with some risks of leakage and engine breakdown. An ultrasonic oscillating probe was used to simulate the pitting rates and behavior of samples extracted from cylinder liners, which are made of grey cast iron, with differences in surface roughness, glycol and inhibitor content in coolant, coolant temperature and graphite flake class; bainitic microstructures were also tested. Measurements consisted of mass losses under set intervals during experiments lasting 2.5 or 4 hours. Affected surfaces were later evaluated with scanning electron microscopy and confocal microscopy. Results indicate higher cavitation damage with: lower concentrations of glycol and absence of corrosion/cavitation inhibitors in the coolant liquid, lower liquid temperatures between 76⁰C and 90⁰C, and presence of B-type graphite class in the microstructure. Results regarding surface roughness were inconclusive. A sequence of surface damage mechanisms has been proposed, with corresponding microscope observations, to explain the mass loss trends and the associated microstructural changes over time.

В настоящей выпускной квалификационной работе «Исследование процесса удаления серы из полупродукта на установке десульфурации в условиях АО «ЕВРАЗ НТМК» рассмотрено распределение серы по переделам металлургического производства АО «ЕВРАЗ НТМК» а также проведена работа по повышению стойкости фурмы установки десульфурации чугуна. / In this final qualifying work " Study of the process of removing sulfur from a semi-product at a desulfurization plant in the conditions of JSC "EVRAZ NTMK", the distribution of sulfur in the metallurgical production processes of JSC" EVRAZ NTMK " is considered, and work is also carried out to improve the durability of the tuyere of the pig iron desulfurization plant.

Cast iron, taking the advantages of the advanced castability forming components of complex geometries and favorable mechanical properties, is employed in engine components in truck industries. Compacted graphite iron (CGI) integrates both merits of lamellar graphite iron (LGI) and spheroidal graphite iron (SGI) such as good machinability and high thermal conductivity from LGI, high ultimate tensile strength (UTS), good fatigue resistance, high elastic modulus, and high ductility from SGI, thus is now becoming a competitive alternative of traditional LGI in cylinder blocks and heads. Due to the shape complexity of cast components, residual stresses arise accordingly. Normal methods for measuring stresses have various practical difficulties that affect accuracy. For example, in strain gauge measurements such as hole drilling and cutting, casting skins need to be polished as the attachment of strain gauge requires a smooth surface condition for precise detection, though any mechanical treatment would change the residual stress state. On the other hand, electropolishing applied in XRD measurement for extracting depth profile causes no release of stresses, nevertheless, there is no dissolution reaction on graphite particles. This would retard further polishing and form a rough surface instead of flat extraction. A visual strain detection system relies on a stable and clean surface condition, therefore, when it is combined with the drilling technique, the drilling chips could be a vital problem for repeatability when they block the view of drilling edges. Ultrasonic measurement, in theory, has lower precision by averaging the stresses within a certain volume beneath surfaces. A number of methods have been developed to measure residual stresses, ranging from destructive to non-destructive according to the removal amount of materials. In this thesis work, several measurement methods are implemented on cylinder heads and the results are compared with simulation to develop a suitable method of measuring residual stresses in cast engine components. It is found that longer shakeout time lowers the tensile stresses and develops more compressive stresses in the surface layer. Cutting is a suitable method compared with others. Incremental center-hole drilling technique is not suitable to measure cast components as the surface grinding before stain gauge mounting causes high deviation. Hole drilling with visual strain detection provided high errors within the first 0.1 mm as the strains were too weak to be visualized at the beginning of drilling. The electropolishing process was also found retarded by graphite particles, and the XRD results are more trustworthy with more tilt angles. Ultrasonic measurement is rather rough due to the influence of graphite on the traveling velocity of ultrasound. / Tack vare sin utmärkta gjutbarhet, som möjliggör gjutning av komplexa geometrier, samt goda mekaniska egenskaper är gjutjärn första valet i många motorkomponenter inom lastbilsindustrin. Kompaktgrafitjärn (CGI) kombinerar fördelarna med lamellärt grafitjärn (LGI) och sfäroidalt grafitjärn (SGI) såsom god bearbetbarhet och hög värmeledningsförmåga från LGI, hög draghållfasthet (UTS), hög utmattningshållfasthet, hög elastisk modul (E-modul) och hög duktilitet från SGI. Detta gör kompaktgrafitjärn till konkurrenskraftigt alternativ till traditionell LGI i cylinderblock och huvud. På grund av formkomplexiteten hos gjutkomponenter uppstår restspänningar. Normala metoder för att mäta spänningar har olika praktiska svårigheter som påverkar noggrannheten. Vid töjningsmätningar genom hålborrning och sågning måste t ex gjutskinn slipas bort eftersom fästning av töjningsmätare kräver en jämn yta för exakt detektion, även om prepareringen kan påverka spänningstillstånd. Å andra sidan orsakar elektropolering som appliceras i XRD-mätning för extrahering av djupprofil inte att spänningar frigörs, däremot finns det inget etsmedel för grafitpartiklar. Detta gör att poleringen skapar en ojämn yta istället för en platts yta. Systemet för visuell detektering av förlängning förlitar sig på en stabil och ren yta. Därför kan borrspånen, när visuell detektering kombineras med borrteknik, vara ett viktigt problem för repeterbarheten. Ultraljudsmätning har i teorin lägre precision genom att den endast mäter medelvärdet av spänningarna i en viss volym under ytan. Ett antal metoder har utvecklats för att mäta restspänningar, både förstörande och oförstörande. I denna examensarbetesrapport implementeras flera mätmetoder på motorcylinderhuvuden och resultaten jämförs med simulering för att utveckla en lämplig metod för att mäta restspänningar i gjutna motorkomponenter. Det visas i arbetet att längre urslagstid kan sänka dragspänningarna och utveckla mer tryckspänningar i ytskiktet. Sågning är en lämplig metod jämfört med de andra. Inkrementell hålborrningsteknik är inte lämplig för att mäta restspänningar på gjutkomponenter eftersom ytslipningen före montering av töjningsmätare orsakar hög avvikelse. Hålborrning med visuell töjningsdetektering gav höga fel inom den första 0,1 mm från ytan eftersom töjningen är för liten för att kunna visualiseras i början av borrningen. Det är hänt ofta att elektropoleringsprocessen före XRD-mätningen blir fördröjd av grafitpartiklar, och XRD-resultaten är mer pålitliga med fler lutningsvinklar. Ultraljudsmätning är grov på grund av grafitens påverkan på ultraljudets hastighet.

The desulfurizing powers of aplite, aplite-soda ash mixtures, and aplite-dehydrated lime combinations when added to a ladle of cast iron were tested. Ladle conditions were simulated by melting cast iron in a crucible and introducing the reagent mixtures into the molten metal by means of a cast iron cup and steel rod. It was found that in every case the desulfurizlng power was appreciably below that of soda ash and did not warrant testing the mixture to determine its effect upon the corrosion of ladle refractory linings. / Master of Science

[pt] Esta pesquisa teve como objetivo avaliar a vida-fadiga de dois ferros fundidos nodulares modificados metalurgicamente, sendo uma classe predominantemente ferrítica e outra.perlítica. Inicialmente, amostra dos dois ferros fundidos nodulares ferrítico e perlítico foram fundidas adotando-se moldação em areia na geometria padrão Y-block. Em seqüência, corpos de prova para ensaios mecânicos e de fadiga foram usinados das amostras ferríticas e perlíticas. Após os ensaios de tração e dureza, realizaram-se análises metalográficas qualitativas e quantitativas em ambos os materiais, com o intuito de se determinar suas características metalúrgicas, tais como contagem, distribuição e classe dos nódulos de grafita, bem como quantidade da matriz ferrítica e perlítica. Dando continuidade a etapa experimental, as curvas tensão versus número de ciclos para a falha do ferro fundido nodular ferrítico e do ferro fundido nodular perlítico foram levantadas por meio de ensaios de flexão rotativa. A vida útil em fadiga dos dois materiais foi relacionada com as suas características metalúrgicas. Quanto a resistência à fadiga, as amostras do ferro fundido nodular perlítico tiveram um melhor comportamento sob carregamento cíclico do que as amostras do ferro fundido nodular ferrítico. Tal comportamento superior foi atribuído a maior microdureza da matriz e a presença da estrutura olho-de-boi. Finalmente, as curvas experimentais tensão versus número de ciclos para a falha dos ferros fundidos nodulares ferrítico e perlítico foram modeladas pela equação de Coffin-Manson, que se mostrou eficiente no tratamento de dados experimentais da vida em fadiga de ambos os materiais. / [en] The objective of the present work was to evaluate the fatigue life of two nodular cast irons with metallurgical modifications and resulting in ferritic and perlitic different classes of material. Initially, samples of both materials were cast in sand moulds adopting the standard Y-block geometry. In the sequence, tensile and fatigue specimens were machined from the ferritic and perlitic samples. After the tensile and hardness tests, the microstructure of the both materials were analyzed by qualitative and quantitative metallography, aiming to characterize their metallurgical aspects as content, distribution and class of graphite nodules, as well as the contents of the ferritic and perlitic matrix. Following the metallurgical characterization, rolating bend fatigue tests were performed in order to estabilish the stress-life curves of the ferritic and perlitic nodular cast irons. Regarding the fatigue resistance, the specimens machined from the perlitic nodular sample showed a longer fatigue life than that related to the ferritic nodular specimens. The longer fatigue life of the perlitic nodular specimens was associated with a higher microhardness of the perlitic matrix and the preserve of the bull`s-eye structure. Finally, the experimental stress-life curves of the ferritic and perlitic nodular cast irons were modeled adopting the Coffin-Manson law, which was considered efficient in fitting experimental fatigue life data of both materials.

Competitive metallurgical production is almost impossible without the knowledge of the chemical composition of manufactured and finished melt, or the produced product. With growing customer demands for product quality and product characteristics, increasing technology speed and increasing product purity, there is growing demand for analyzes of chemical composition. These demands are very often against each other, especially the increasing demands on the speed and accuracy of analyzes. Analytical requirements may not only apply to the test technique, but also to the quality of the sample, which is inseparable from it. What is recently seen as the biggest drawback, the new technology is trying to use as its main priority. This is undoubtedly true of atomic emission spectrometry.

In this thesis, the structural and mechanical changes, which took place in flake graphite cast iron after electron beam surface melting and chrome-nickel surface alloying, were studied. Furthermore, the effect of set parameters on properties and depth of the melted and alloyed region is also analyzed. In the experimental part, the analyzed microstructures, micro-hardness and the distribution of elements after melting and alloying, were presented. Structural differences of material regions caused by melting were described based on microstructures. In the end of diploma thesis, the conclusions of using EB technology for surface melting and alloying were discussed.

This diploma thesis is focused on production and problems in production of thin-walled ductile iron castings, especially in the inoculation process. The focus is on the influence of elements on the structure and mechanical properties of ductile iron and as well as the influence of some elements, that are commonly used in inoculation alloys. Furthermore, the factors that affect the production technology are written, i.e., solidification rate, wall thickness, cooling rate, and factors used for affecting the thin-walled castings production, i.e., the use of insulating moulding compounds and increasing the graphite nodule count. At the end of the theoretical part, important production processes are analysed, namely inoculation and spheroidization. The experimental part is focused on influencing the structure and mechanical properties using several types of inoculants of different chemical compositions, whereas the tested thicknesses of the test plates are 3-, 5- and 8-mm. Hardness, tensile strength and ductility are evaluated on these plates. Finally, the volume of ferrite in the structure, shape and size of the graphite nodules were examined.

While using iron castings behind temperature of 500 oC namely at cyclic heat straining, degradation of structure and breaching iron castings. For this purpose introduce cast iron with content of Si and Mo. Focusing on improvement of SiMo51 for increased high-temmperature corrosion-and fatigue life in exhaust-gas temperatures up to 800 oC. Thesis set up survey types alloys, properties, and way of casting production.