Dissertations / Theses: 'Steel alloys – Metallurgy'

1

Yu, Dawei. "Welding metallurgy and toughness improvement for mild and low-alloyed steel electroslag weldments /." Full text open access at:, 1988. http://content.ohsu.edu/u?/etd,164.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Yao, Lan Lance. "Atom probe microscopy of clustering and precipitation processes in microalloyed strip cast steels." Thesis, The University of Sydney, 2011. https://hdl.handle.net/2123/29282.

Full text

Abstract:

The challenge of climate change is pushing the modern steel industry to focus on not only products with better properties and performance but also those produced by greener steelmaking processes. The CASTRIP® process is a recently-developed technology that can produce strip cast steels in a cheaper, more efficient and less energy-intensive way. Thin CASTRIP ® steel products are unprecedented in thickness at 0.8-1.5 mm and display very good mechanical properties. They are an excellent alternative to products made by hot and cold rolling methods that are relatively costly and less efficient. Nb, a well-known effective element for grain refinement of steels, has been tentatively added into CASTRIP® plain carbon steels. Preliminary research outcomes showed finer microstructure and corresponding improved strength as the result of Nb additions. Moreover, Nb solutes are thought to be uniformly distributed within the grain. No obvious precipitates are found in the microstructure. Providing the well-known affinity between Nb and interstitials i.e. C and N, opportunities are hypothesised to further strengthening by utilising these Nb solutes in solid solution. In this thesis, heat treatment is adopted to induce modification of the solid solution. Through ageing at 525° C, secondary phases are believed to be formed in the steels as the properties of tl1e aged sample are improved. Interestingly both yield strength and total elongation exhibit improvement despites the conventional dilemma in improving both of these antagonist properties. To explore the origins beyond this fascinating property changes, atom probe microscopy (APM) is adopted to provide materials information in three dimensions with near atomic resolution and high chemical sensitivity. Several APM techniques have been developed essentially to support this project: The optimal experimental conditions for running microalloyed steel specimens, a filtering technique for atom probe microscopy data, a new method for the quantitative determination of crystal structure (plane spacings and angles between families of planes) via Hough transformation and the idea of time-chemical correlation in atom probe data were introduced and investigated. Using these technical advances, unprecedented fine microscopic imaging and quantitative analyses of NbCN clustering processes in aged samples are characterized. It is concluded that the strengthening originates from both clustering and precipitation, leading to the win-win property change in both strength and ductility after ageing.

APA, Harvard, Vancouver, ISO, and other styles

3

Daames, Sherwyn. "The metallurgical phase transformations in ROQ-tuf AD690 due to the MMA welding process." Thesis, Peninsula Technikon, 2002. http://hdl.handle.net/20.500.11838/1264.

Full text

Abstract:

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2002
Phase transformations in steel are of profound commercial importance due to the fact that they influence the physical and mechanical properties of the end product. During the casting process, which occurs at temperatures in excess of 1500°C, the microstructure of the steel is austenitic. During slow cooling the austenite will decompose into lower temperature microstructures such as ferrite, pearlite or hard, brittle cementite, the latter becoming increasingly present the higher the carbon content of the steel. Steel manufacturers, however, make use of additional forming processes such as rolling, quenching and reheat or tempering to impart specific mechanical or metallurgical properties to a particular steel. If the cooling rate is increased, as would be the case during a quenching process, the austenite will decompose forming a needle like microstructure called bainite in addition to the other microstructures. A further increase in the cooling rate will result in the diffusionless transformation of part of the austenite to form martensite, a hard brittle microstructure. If heat was now to be applied to the steel, as in a tempering process, some of the martensite formed during the quenching process will again transform into a softer microstructure such as pearlite or ferrite.

APA, Harvard, Vancouver, ISO, and other styles

4

Johnston, Scott R. "Initial stage sintering model of 316L stainless steel with application to three dimensionally printed (3DPtm) components /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/7052.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Coffey, Melvin W. "The effect of antimony on segregation during dendritic solidification in a cast modified 4720 alloy /." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,93.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Sulaiman, Samsiah. "Structure of properties of the heat affected zone of P91 creep resistant steel." Access electronically, 2007. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080916.150054/index.html.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Anderson, Danny. "Effect of the joint addition of aluminum and molybdenum on the precipitation and recrystallization in HSLA steels." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66207.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Xie, Kelvin Yu Xuan. "The effect of niobium-rich clusters on the mechanical properties of ultra-thin strip cast steels produced by the CASTRIP® process." Thesis, The University of Sydney, 2012. http://hdl.handle.net/2123/17140.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Tucker, Laura Arias. "Microstructure-property relations throughout the powder metallurgy process." Master's thesis, Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11092007-005857.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Gould, Elijah Katunich. "Development of Constitution Diagram for Dissimilar Metal Welds in Nickel Alloys and Carbon and Low-Alloy Steels." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285007217.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Bao, Yaxin. "Mechanical properties and microstructure study for direct metal deposition of titanium alloy and tool steel." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Bao_09007dcc803c0daf.pdf.

Full text

Abstract:

Thesis (M.S.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 29, 2007) Includes bibliographical references.

APA, Harvard, Vancouver, ISO, and other styles

12

Lundberg, Daniel, Filip Wilson, Hjalmar Gunnarsson, Leo Sjörén, Robin Xu, and Erik Djurberg. "Long term aging and creep exposure for advanced heat resistant alloys : A phase analysis." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446407.

Full text

Abstract:

This project was ordered by Sandvik Materials Technology and was performed by a group of students at Uppsala university. The purpose of the project was to study precipitation behavior and structure stability in six advanced heat resistant alloys. Each sample were subjected to a creep rupture test in 600 or 700°C depending on the alloy type. Two parts of each alloy where examined; one part which had been affected by creep and another part which was unaffected by creep. A literature study was performed first to gain knowledge of the scientific theory utilized in this project, namely creep, precipitation hardening, and about the different materials which were analyzed. Preliminary results for the phase composition of the materials were obtained from a Thermo-Calc (TC) simulation. The SEM-images showed nothing noteworthy for any sample due to the roughness of the sample surfaces. The EDS-analysis showed chromium depletion in the centers of the aged samples of HT9 and Sanicro® 75X. Other minority phases such as Cr23C6 in Sanicro®70, P-phase and a titanium nitride phase in sanicro® 60X, VB in Esshete 1250 and Sigma-phase in 4C54 were identified using EDSmapping. It was found that when using XRD to analyze the phase compositions of small samples it is impractical to have the samples cast in bakelite beforehand. The XRD-results obtained in this project showed that more than 90% of the XRD diffractogram for every sample was graphite, which made the identification of minority phases impossible. The quality of the LOM-images varied greatly between samples, for 4C54 grain sizes were measured in all images, for Esshete 1250 grain sizes were measured for the crept sample, and for Sanicro® 60X measurements could only be taken from one image. Most of the sample preparation was insufficient to achieve the test results necessary for complete microstructural analysis and phase analysis of the samples. The mistakes in the practical steps of the project were noted and improvements for these mistakes are presented in the conclusion.

APA, Harvard, Vancouver, ISO, and other styles

13

Shi, Shu. "Repair weldability of heat-resistant stainless steel casings-HP45NB, HP50NB and 20-32NB alloys." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1140490923.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Kim, Yeong Ho. "Chromium-free consumable for welding stainless steel corrosion perspective /." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1133285376.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Doyle, Richard John-Paul. "An investigation into the hydrogen embrittlement susceptibility of experimental 304 stainless steel alloys modified with ruthenium and palladium additions." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6763/.

Full text

Abstract:

The motivation for this work was provided by the results of an interdisciplinary, multi-university research programme funded by the Ministry of Defence. The significant finding in question was that the stress corrosion cracking (SCC) resistance of AISI type 304 stainless steel (SS) alloys can be significantly improved by the addition of the platinum group metals (PGM), ruthenium and palladium. The increased SCC resistance could be attributed to the enhancement of the cathodic hydrogen reduction reaction. Thus, the primary objective of this work was to confirm that the increase in hydrogen production at the surface would not counteract the improvement in SCC resistance by increasing the susceptibility to hydrogen embrittlement (HE). Electrochemical hydrogen charging was employed and melt extraction was used to measure the bulk concentration of absorbed hydrogen as a function of alloy chemistry. Both Ru and Pd doped experimental 304 SSs showed a decrease in the concentration of absorbed hydrogen compared to an experimental standard 304 SS (i.e., a controlled, non PGM-doped reference 304). This result is thought to be due to the PGMs enhancing the recombination kinetics of adsorbed hydrogen. Ru proved more effective than Pd at hindering absorption and this is likely associated to the more homogenous distribution of Ru in solid solution. Slow strain rate tensile (SSRT) testing was performed in air at sub-ambient temperatures on pre-hydrogen charged specimens. PGM addition was found not to increase the susceptibility of 304 to HE. Conversely, an approximately equal enhancement of the HE resistance was observed for the addition of both Ru and Pd. The modest improvements are attributed to the reduced concentration of absorbed hydrogen, with a further possible beneficial trapping effect of Pd concentrated bands, contributing to the HE resistance of Pd doped 304.

APA, Harvard, Vancouver, ISO, and other styles

16

Romo, Arango Sebastian A. "Low-Cycle Fatigue of Low-Alloy Steel Welded Joints." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1573054310351145.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Macêdo, Gabriel. "Material Transfer Mechanisms during Interaction of Aluminium Alloy and Tool Steel at Elevated Temperatures." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80118.

Full text

Abstract:

Hot stamping of aluminium alloys allows for increased formability, decreased springback and the possibility of integrating age-hardening heat treatments into the process. However, it can be challenging due to the occurrence of material transfer of aluminium onto the tool, as aluminium is prone to adhesion even at low temperatures. Hence, lubrication is always necessary when forming aluminium, but lubricants can still fail, leading to direct interaction between tool and workpiece and thus material transfer. This phenomenon reduces the efficiency of the process, as interruptions are necessary for the refurbishment of the tools. Understanding of how material transfer takes place is important in order to find new or improved solutions, in terms of lubrication and surface engineering, to prevent adhesion. Nevertheless, current research in high temperature tribology of aluminium, mainly in terms of material transfer mechanisms, is very limited, as many of the works focus on lubricated conditions and do not look into the fundamental interactions between aluminium alloys and tool steels. In this context, the aim of this work is to investigate the mechanisms behind the occurrence of aluminium alloy transfer onto tool steel during sliding at high temperature and in dry conditions. A hot-strip drawing tribometer was used to perform tests at room temperature, 300°C, 400°C, and 500°C, directly after solubilizing the aluminium alloy at 520°C. Two different topographies for the tool steel were used: ground and polished. Material transfer characterization was performed mainly through scanning electron microscopy. It was found that grinding marks (ground tool steel) and carbides (polished tool steel) act as initiation sites for the transfer to occur. Temperature plays a role on the growth mechanisms of the transfer films during sliding, as thermal softening of the aluminium alloy is the dominant factor in determining the growth direction of the transfer layers. A growth towards the trailing edge (shearing and smearing of the transferred aluminium) or a growth towards the leading edge (build-up of transferred aluminium, leading to a thicker and more localized transfer material).

APA, Harvard, Vancouver, ISO, and other styles

18

Lee, Trevor J. "Investigation of ASTM E 238 Bearing Pin Properties for Various Aerospace Alloys." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1074.

Full text

Abstract:

Aircraft are often designed with numbers determined by testing in a lab, rather than by repeatedly building prototypes. These lab tests conform to testing specifications so that the numbers can be compared between manufacturers, suppliers, and lab technicians. One such specification is ASTM specification E238 – 84(08), and it is used to determine important properties of a bearing pin joint like hinges, bolt holes, and rivet joints. The properties determined from this fastener-through-plate method are bearing strength, bearing yield strength, and bearing stiffness. Adhering to the methods outlined in ASTM E238, a study was performed, looking at the effects that plate material, fastener used, fastener lubrication, and plate hole preparation method (whether drilled and reamed or just drilled) have on the three bearing joint properties. The plate materials used were Al 7050 – T7451, Ti – 6Al – 4V (mill annealed), and PH13 – 8Mo – H1000. The fasteners were Ti – 6Al – 4V screws, coated A286 screws, and high speed steel (HSS) pins used as a control. Lubrication was tested using a corrosion inhibitor, PR – 1776M B – 2 from PRC – DeSoto, on the fastener or leaving the fastener uncoated. The HSS pins were always tested in the uncoated condition. 54 runs were performed, as outlined by a D-optimal design of experiment. It was discovered from the statistical analysis of the results via ANOVA that both the plate material used and the pin material, whether a screw or a pin, had a significant effect on the bearing strength, bearing yield strength, and bearing stiffness. The interaction between the two factors was also significant on all responses but the bearing stiffness. PH13 – 8Mo – H1000 plates seemed to perform best on average, followed by Ti – 6Al – 4V plates, then Al 7050 – T7451 plates. PH13 – 8Mo – H1000 and Ti – 6Al – 4V plates had similar bearing strength and bearing yield strength averages with the HSS control pins being used, which had the highest mean values for a given plate and fastener. The Ti – 6Al – 4V and A286 screws behaved and performed statistically similar in most cases, except when hole preparation method was take into account. The Ti – 6Al – 4V screws performed better when the hole was drilled and reamed, while the coated A286 screws performed better when the hole was drilled only. All screws had lower resulting bearing properties than the HSS control pins. It was also found that ASTM specification E238 – 84(08) is a precise test method, since the method could be performed repeatably and reliably with no missing data points. Therefore, this ASTM testing method is reasonable for determining bearing properties, which can then be used to design aircraft.

APA, Harvard, Vancouver, ISO, and other styles

19

Hammond, Derek. "An investigation of the impact of selected cooling strategies on milling of difficult-to-cut materials with an emphasis on titanium alloys and hardened steel." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80372.

Full text

Abstract:

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The aerospace- and automotive industries have an urgency to save space and reduce weight, as well as a need to increase fuel efficiency and reduce emissions. This has led to the use of lightweight structural materials, such as Ti6A14V alloy, which is the most widely used titanium alloy in the aerospace industry. This alloy has an exceptional strength-to-density ratio. The work also covers studies on tool steel 40CrMnMo7 that is used in applications in the tooling-, aerospace and automotive industry. In the quest for improved performance new alternative methods of efficiently machining these materials are investigated. One of the important criteria during machining of these materials is their machinability. This study discusses current research in high performance machining strategies and techniques for advanced materials such as Ti6Al4V and 40CrMnMo7. The properties that make these materials advantageous for the use in the aerospace- and automotive industry also make them difficult to cut. The widespread application of Ti6Al4V in the aerospace industry has encouraged investigations into cooling strategies or -techniques to maintain and improve tool life. Ti6Al4V has a low thermal conductivity causing the heat generated during machining to accumulate on the cutting edge of the tool. During various experiments the application of external compressed air blow cooling (dry cutting), flood cooling, high pressure through spindle cooling (HPTSC) and modifications thereof were investigated. The research project also evaluated the performance of a coating (TiAlN) and various coating treatments. The objectives of the HPTSC modifications were to improve the coolant stream impingement on the tool surface, effectively compressing the thermal barrier, and to reduce the chip-tool contact area. This would lead to a decrease in tool heating and wear. The modified techniques failed to increase tool life but showed signs of increased heat removal capability under the given conditions. It was observed that air blow cooling (dry cutting) delivered the best results when considering cutting materials, coating, coating treatment and cooling strategies or –techniques throughout the experiments conducted.
AFRIKAANSE OPSOMMING: Die Ruimte-en motor-industrie het 'n dringendheid om ruimte te bespaar en gewig te verminder, sowel as 'n behoefte om brandstofdoeltreffendheid te verbeter en emissies te verminder. Dit het gelei tot die gebruik van liggewig strukturele materiale, soos Ti6A14V Allooi , wat die mees gebruikte titanium allooi in die Ruimte is. Hierdie allooi het 'n uitsonderlike krag-tot-digtheid-verhouding. Die studie dek ook gereedskapstaal 40CrMnMo7 wat in die gereedskap, Ruimte-en motor-industrie aangewend word. In die soeke na verbeterde prestasie word nuwe alternatiewe metodes om effektief bewerking van hierdie materiaal ondersoek. Een van die belangrikste kriteria tydens bewerking van hierdie materiaal is die bewerkbaar daarvan. Hierdie studie bespreek die huidige navorsing in hoë prestasie bewerking strategieë en tegnieke vir gevorderde materiale, soos Ti6Al4V en 40CrMnMo7. Die eienskappe wat hierdie materiaal voordelig maak vir die gebruik in die lug-en Ruimte-en motor-industrie, maak dit terselfdetyd moeilik om te sny. Die wydverspreide toepassing van Ti6Al4V in die lug-en Ruimte industrie moedig ondersoeke aan na koelstrategieë of -tegnieke om die instrumentlewe te handhaaf en te verbeter. Ti6Al4V het lae termiese geleidingsvermoë wat veroorsaak dat die hitte, wat gegenereer word tydens bewerking, versamel op die voorpunt van die instrument. Tydens verskillende eksperimente was die toepassing van eksterne saamgeperste lugblaas-verkoeling (droë sny), vloed verkoeling, hoë-druk-deur-die-spil-afkoeling (HPTSC) en aanpassings daarvan geondersoek. Die navorsingsprojek het ook die prestasie van 'n bedekkingslaag (TiAlN) en verskeie bedekkingslaagbehandelings geëvalueer. Die doelwit van die HPTSC aanpassing was om die koelmiddelstroom beklemming op die instrument oppervlak te verbeter, en effektiewelik die termiese versperring saam te pers, asook die skerf-teenoorinstrument kontak te verminder. Dit sou lei tot 'n afname in die instrumentverwarming en -slytasie. Die gewysigde tegnieke het daarin misluk om die instrumentlewe te verhoog, maar het tekens getoon van 'n toename in hitte verwydering vermoë onder die gegewe omstandighede. Dit is dus waargeneem dat lugblaasverkoeling (droë sny) die beste resultate gelewer het in die oorweging van sny materiale, bedekkingslaag, bedekkingslaagbehandelings en verkoeling strategieë of -tegnieke wat regdeur die eksperimente uitgevoer was.

APA, Harvard, Vancouver, ISO, and other styles

20

Sowards, Jeffrey William. "Development of a chromium-free consumable for joining stainless steel." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1237845645.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Tahir, Abdul Malik. "Alloy element redistribution during sintering of powder metallurgy steels." Doctoral thesis, KTH, Fysiokemisk strömningsmekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145251.

Full text

Abstract:

Homogenization of alloying elements is desired during sintering of powder metallurgy components. The redistribution processes such as penetration of liquid phase into the interparticle/grain boundaries of solid particles and subsequent solid-state diffusion of alloy element(s) in the base powder, are important for the effective homogenization of alloy element(s) during liquid phase sintering of the mixed powders. The aim of this study is to increase the understanding of alloy element redistribution processes and their effect on the dimensional properties of the compact by means of numerical and experimental techniques. The phase field model coupled with Navier-Stokes equations is used for the simulations of dynamic wetting of millimeter- and micrometer-sized metal drops and liquid phase penetration into interparticle boundaries. The simulations of solid particle rearrangement under the action of capillary forces exerted by the liquid phase are carried out by using the equilibrium equation for a linear elastic material. Thermodynamic and kinetic calculations are performed to predict the phase diagram and the diffusion distances respectively. The test materials used for the experimental studies are three different powder mixes; Fe-2%Cu, Fe-2%Cu-0.5%C, and Fe-2%(Cu-2%Ni-1.5%Si)-0.5%C. Light optical microscopy, energy dispersive X-ray spectroscopy and dilatometry are used to study the microstructure, kinetics of the liquid phase penetration, solid-state diffusion of the Cu, and the dimensional changes during sintering. The wetting simulations are verified by matching the spreading experiments of millimeter-sized metal drops and it is observed that wetting kinetics is much faster for a micrometer-sized drop compared to the millimeter-sized drop. The simulations predicted the liquid phase penetration kinetics and the motion of solid particles during the primary rearrangement stage of liquid phase sintering in agreement with the analytical model. Microscopy revealed that the C addition delayed the penetration of the Cu rich liquid phase into interparticle/grain boundaries of Fe particles, especially into the grain boundaries of large Fe particles, and consequently the Cu diffusion in Fe is also delayed. We propose that the relatively lower magnitude of the sudden volumetric expansion in the master alloy system could be due to the continuous melting of liquid forming master alloy particles.

QC 20140515

APA, Harvard, Vancouver, ISO, and other styles

22

Jubica, Jubica. "Characterization of Secondary Carbides in Low-Alloyed Martensitic Model Alloy Tool Steels." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284449.

Full text

Abstract:

The development of tool steels for making and shaping other materials requires a better understanding of the material's properties during manufacture. These high-quality steels include many alloying elements, which give increased hardness during tempering. For producing hardened microstructures, austenite generation is essential. The martensite formed by rapid quenching of austenite followed by tempering helps develop high strength steels. Studying carbide precipitation is a challenge as they are very small in size, present only in small volume fractions and high number densities. The carbide reactions are complicated due to so-called metastable carbides, which are only present as part of the precipitation process. This work focuses on model alloys with two main elements in addition to iron and carbon, molybdenum, and vanadium, to clarify and simplify the carbide characterization. This is done to determine the effect of molybdenum and vanadium carbides on the overall hardness. In this work, two model alloys, A and B, are tempered at 550°C and 600°C with the same vanadium content but different molybdenum contents. The hardness of the materials is evaluated and compared at these temperatures. A more detailed characterization work is done for material A with Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy (STEM-EDS) to understand the microstructure and analyze the precipitates. Simulations are performed with Thermo-Calc Prisma (TC-Prisma) to support the experimental work, which includes the simulation of the secondary carbide precipitation, mainly molybdenum carbides in material A tempered for 24h at 600°C, and predicts the carbide precipitation behavior in this steel. The results from STEM-EDS and TC-Prisma for material A, show that the small secondary carbides in the martensite contribute to the increased strength of material A. Due to the overaging of the carbides at 600°C, the hardness at 550°C is higher than at 600°C for material A. The given thesis work is an attempt to interpret the development of secondary carbides of Mo and V in the martensitic matrix and their role in the overall hardness.
Den ständiga utvecklingen av högpresterande stål för transport, konstruktion och energisektorn kräver bättre förståelse för materialets egenskaper vid tillverkning. Dessa martensitiska stål inkluderar många legeringselement vilket ger ökad hårdhet vid härdning och anlöpning. Att studera utskiljning av karbider är en utmaning eftersom de är närvarande endast i liten volymsfraktion. Karbidreaktionerna är komplexa till följd av så kallade metastabila karbider vilka endast är närvarande vid en del av utskiljningsförloppet. För att tydliggöra och förenkla karbidkarakteriseringen fokuserar detta arbete på modellegeringar med två huvudelement utöver järn och kol, molybden och vanadin. Detta görs för att fastställa effekten av molybden och vanadinkarbider på den totala hårdheten. I detta arbete studeras två modellegeringar, A och B, härdade och anlöpta vid 550 °C och 600 °C med samma vanadininnehåll men olika molybdeninnehåll. Materialens hårdhet utvärderas och jämförs vid dessa temperaturer. Ett mer detaljerat karaktäriseringsarbete görs för material A med hjälp av STEM-EDS för att förstå mikrostrukturen och analysera utskiljningarna. Simuleringar görs med TC-PRISMA för att stödja det experimentella arbetet, vilket inkluderar simulering av den sekundära karbidutskiljningen och predikterar karbidstrukturen i dessa stål. Resultaten visar att de små sekundärkarbiderna i martensiten bidrar till den ökade styrkan hos material A. Hårdheten vid 550 °C är högre än vid 600 °C för material A eftersom både utskiljningen av karbider är sker långsammare och även dislokationsåterhämtning.

APA, Harvard, Vancouver, ISO, and other styles

23

Brisenmark, Emil, and Valencik Jane Jönsson. "Evaluation of the Effect of Non-Metallic Inclusions on the Corrosion Resistance of Stainless Steels and Nickel-based Alloys." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277900.

Full text

Abstract:

Non-metallic inclusions (NMI) are small impurities that can always be found in steel and other materials. NMIs are of great importance because they may negatively impact various properties of the steel, depending on their composition, morphology and numbers. In the oil and gas industry, one of the most concerning property that can be affected by the NMIs is corrosion resistance. In this report, certain aspects of NMIs were investigated, such as size or composition and effect which they have on the corrosion resistance. To accomplish this, two different steel alloy samples from pipelines were analyzed using electrolytic extraction,a scanning electron microscope (SEM) and a software called ImageJ. The results showed that only Niobium-Titanium carbides (NbTi-C) which were found on one of the samples had the potential to be dangerous, due to them causing pits ranging from 1 to 12.5 times their inclusion size. It was also found out that the size of the inclusions did not affect the size of the pitting that they caused.
Icke metalliska inneslutningar (NMI) är små föroreningar som alltid finns i stål och andramaterial. NMI:er är mycket viktiga eftersom de kan negativt påverka olika egenskaper hos stål, beroende på deras komposition, morfologi och antal. I olje -och gasindustrin är en särskilt oroande egenskap som kan påverkas av NMI:er deras korrosionsmotstånd. I denna rapport undersöktes hur olika aspekter hos NMI:er, som storlek eller komposition, påverkade korrosionsmotståndet i rostfritt stål. För att utföra detta analyserades två olika stållegeringsprovbitar från pipelines med elektrolytisk extraktion, ett svepelektronmikroskop (SEM) och ett program som kallas ImageJ. Från resultatet framkom det att baraNiob-Titankarbider (NbTi-C) som fanns på en av provbitarna hade potentialen att vara farlig, då den orsakar gropar som är 1 till 12.5 gånger större än sin egen storlek. Det framkom också att storleken på inneslutningarna inte påverkade storleken på deras gropar.

APA, Harvard, Vancouver, ISO, and other styles

24

Englund, Hanna, and Henrietta Isaksson. "Regulation of Nitrogen Content in High Alloyed Stainless Steels during the AOD Process." Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254419.

Full text

Abstract:

As a final step in the argon oxygen decarburisation (AOD) process, argon- and nitrogen gas is blown through the melt. To regulate the nitrogen content in the steel melt during this step a reliable model is needed. With data from 31 heats of the duplex stainless steel SAF2507 collected at Sandvik Materials Technology (SMT), different models are investigated. This is done by looking at the partial pressure of the nitrogen gas and the nitrogen content achieved during each heat. By calculating the nitrogen solubility in the steel melt with different models and then using Sieverts’s law, a partial pressure for the nitrogen gas is obtained for each heat and compared with the data. With adjustments done for a model obtained from J. Kijac et al., more reliable results are attained than by the model used today at SMT. It should be kept in mind that this model is based on the theory with diluted solution and is therefore not optimal for high alloyed steels, and it is suggested to develop a model from a software based on real solution such as Thermo-Calc.
I slutskedet av AOD-processen blåses argon- och kvävgas genom stålsmältan. En pålitlig modell behövs för att reglera kvävehalten i stålsmältan under det här steget. Olika modeller undersöks med data från 31 charger av det duplexa rostfria stålet SAF2507 samlad från Sandvik Materials Technology (SMT). Undersökningen sker genom att titta på partialtrycket av kvävgasen och kvävehalten som uppnåddes för varje charge. Genom att beräkna kvävelösligheten i stålsmältan med olika modeller och sedan använda Sieverts lag, kan ett partialtryck för kvävgas räknas ut för varje charge och jämföras med datan. Mer exakta resultat är uppnådda med en justerad modell hämtad från J. Kijac et al. jämfört med den modell använd på SMT idag. Att ha i åtanke är att denna modell är baserad på teori med antagande om utspädd lösning, vilket inte är optimalt för höglegerade stål och ett förslag är att utveckla en modell med hjälp av ett mjukvaruprogram som baseras på äkta lösning såsom Thermo-Calc.

APA, Harvard, Vancouver, ISO, and other styles

25

Williams, Ceri Ann. "Atomic scale characterisation of oxide dispersion strengthened steels for fusion applications." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:4f03864f-4fe1-4005-ac28-6d9e8244989b.

Full text

Abstract:

Reduced-activation ferritic steels are considered as the primary candidate materials for structural applications within nuclear fusion power plants. It is known that by mechanically alloying ferritic steel powder with Y (usually in the form of Y₂O₃) then consolidating the material by hot isostatic pressing, a nanoscale dispersion of oxygen rich nanoclusters as small as ~2nm is introduced into the microstructure. This vastly improves high temperature strength and creep resistance, and the nanoclusters also act as trapping sites for helium and point defects produced under irradiation. In this thesis, the evolution of the oxide nanoclusters in a Fe-14Cr-2W-0.3Ti & 0.3Y₂O₃ ODS alloy was investigated primarily using atom probe tomography. The microstructure was characterised at various points during processing to give an insight into the factors influencing the formation of the nanoclusters. It was found that the nanoclusters nucleated during the mechanical alloying stage, then followed near classical nucleation and growth mechanisms keeping the same composition of ~8%Y, ~12%Ti,~25%O and ~45%Cr throughout. The formation and evolution of 5-15nm grain boundary oxides was also observed, and these were shown to form first as Cr₂O₃ particles that subsequently transform into a Y-Ti-O based oxide on further processing. The influence of mechanical alloying with 0.5wt.%Fe₂Y rather than 0.3wt.%Y₂O₃ was also investigated, and this showed that there was no difference in the final microstructure produced provided the level of Ti in the starting powder was tightly controlled. Without sufficient Ti, the nanoclusters were Y-O based and ~6nm diameter. Both the Y-O and Y-Ti-O nanoclusters were moderately stable on annealing at 1200°C for up to 100 hours, with only minimal coarsening observed. Ti was found not to influence the coarsening rate of the nanoclusters significantly. The stability of the oxide nanoclusters under irradiation was investigated by using Fe²⁺ ion irradiation to simulate displacement cascade damage in the ODS-Eurofer material (the official European candidate material for testing in the ITER fusion test reactor). Doses up to ~6 dpa at 400°C were used, and there was no significant change to the nanocluster distribution. However segregation of Mn to dislocations was observed after irradiation. These results indicate that ODS steels are good candidate structural materials, as the microstructure is stable at high temperature and under irradiation. The starting powders, and processing parameters need to be tightly controlled in order to produce the optimal material for use in service.

APA, Harvard, Vancouver, ISO, and other styles

26

Rios, P. R. "Some effects of niobium in alloy steels." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373698.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Burrows, Christopher John. "The irradiation resistance of oxide dispersion strengthened steels." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:e464cc9c-5ac0-43cb-acd2-c09706176d9a.

Full text

Abstract:

Reduced activation oxide dispersion strengthened (ODS) steels are candidate alloys for use in fusion reactor systems and are fabricated by mechanically alloying yttrium oxide to a reduced activation ferritic steel powder. The product is consolidated at high temperature by hot isostatic pressing (HIP), producing a dispersion of nanometre sized oxide particles throughout the ferritic microstructure. These particles have been shown to both improve the high temperature mechanical properties of the alloy and provide trapping sites for helium gas. The use of these particles to sequester helium is of particular significance in the development of a structural ODS steel for fusion reactor systems. A fusion power reactor, based on the ITER design, is expected to produce over 2000 appm transmutant helium in any steel components exposed to the core neutron flux. At these gas concentrations, conventional steels undergo severe swelling and embrittlement, motivating the development of materials capable of managing helium accumulation. This thesis investigates the use of the oxide particle dispersion in sequestering helium introduced by ion implantation. An initial characterisation of a model Fe-14Cr-0.25Y₂O₃ (wt%) system was completed using high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). This demonstrated the efficacy of the production methods and the gas trapping capabilities of the oxide particles via argon gas, introduced during the mechanical alloying process. The subsequent consolidation of a full set of Fe-14Cr-3W-0.2Ti-0.25Y₂O₃ (wt%) ODS alloys at 1150°C, 1050 °C and 950 °C produced a systematic variation in the density of the particle dispersion. The characterisation of these materials using APT provided an insight into the consistent Y₂Ti₃O₅ particle chemistry found in each consolidation, and identified a stoichiometric shift from Y₂Ti₃O₅ to YTiO2 following short term annealing periods at 1000°C. Though further work is required, this shift is thought to be consistent with a thermodynamically mediated transition of the metastable clusters to stable oxide particles. Following implantation with 2000 appm helium and examination under TEM, the helium bubble and particle densities were found to be closely correlated thus providing evidence for an association between the particles and the gas bubbles. Controlling the helium bubble density via the particle dispersion demonstrates the potential use of processing temperature in controlling how helium accumulates in an implanted ODS microstructure. The effects of both bubble and particle densities on mechanical properties were investigated further using nanoindentation methods. Significant local variation in the hardness of the ODS steels was found to result from the bimodal grain size distribution of the material. By using only those measurements taken from large grained regions of the ODS, the grain refinement and particle hardening effects could be deconvolved and used to quantify particle hardening using a dispersed barrier model. The significant hardening effects with helium addition observed in the reference alloys were found to be almost entirely absent from the ODS systems, though anomalous softening in the 950°C consolidation indicated a potentially unexpected interaction between the bubble and particle populations. A possible explanation for this anomaly and a proposal for further work to establish its origin is discussed.

APA, Harvard, Vancouver, ISO, and other styles

28

Chou, Tung-Sheng. "Recrystallisation and structure of mechanically alloyed steels." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319558.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Punch, Rachel Bridget. "Toughness enhancement of high strength low alloy strip steels." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5143/.

Full text

Abstract:

High strength strip steels with a yield strength of ~700 MPa are used in the yellow goods industry, with recent trends requiring thicker strips with an improved toughness. Strip steel was produced to thicknesses of 10 – 17 mm, with thinner strips showing improved Charpy impact toughness compared to the thicker strip. It was found that all samples (different thicknesses and test orientations) showed splits on the fracture surfaces in the upper transition region. The hot rolled strip steels showed a predominantly fine-grained (~4 µm ECD) ferrite microstructure, with some coarse grain patches (grains ≥5 µm grouped together). No significant differences were noted for the grain size, yield stress, tensile strength, hardness and texture for the different compositions. Splits were characterised and produced successfully by low blow Charpy testing with acoustic emission (AE) sensors indicating the presence of splits which occurred in the upper transition region predominantly without main crack propagation. Analysis by x-ray tomography and sectioning was carried out showing splits propagate by transgranular cleavage, preferentially following coarse-grained regions, with the 10 mm strip producing deeper splits which was related to elongated grains (high aspect ratio). Therefore the presence of deep splits improved toughness through a reduction of the impact transition temperature, which was achieved by ensuring the presence of a bimodal grain structure, containing coarse elongated grain patches.

APA, Harvard, Vancouver, ISO, and other styles

30

Yin, Jiaqing. "Formation of Bainite in Steels." Doctoral thesis, KTH, Metallografi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207596.

Full text

Abstract:

A systematic survey of morphology of bainite and proeutectoid ferrite was carried out in order to validate some old thoughts of bainite transformation mechanism. It is confirmed that there is no morphological evidence supporting a sharp change neither between Widmanstätten ferrite and the ferritic component of upper bainite, nor between upper and lower bainite. Both Widmanstätten ferrite and upper bainite start with precipitation of ferrite plates at a grain boundary while lower bainite starts with intragranular nucleation. In case of grain boundary nucleation, a group of parallel plates with same crystallographic orientation to the parent austenite grain forms. This process is followed by a second stage of decomposition of the austenitic interspace, which remained in between the primary ferrite plates. At high temperature, the austenitic interspace would either retain as thin slabs or transform into pearlite through a nodule originated from a grain boundary. At lower temperature, cementite precipitation starts to be possible and initiates simultaneous growth of ferrite. Generally, there are two modes of such eutectoid reactions operating in the second stage, i.e. a degenerate and a cooperative mode, which would lead to typical upper and lower bainite, respectively, in definition of carbides morphology. Both upper and lower bainite according to this definition are observed in a wide temperature range. A sharp temperature between the upper and lower bainite structures thus exists only when the definition is based on their nucleation sites, i.e. grain boundary nucleation for upper bainite and intragranular nucleation for lower bainite. Supposing that the first stage is a diffusionless process it should have a high growth rate to prevent carbon diffusion. This is not supported by lengthening rate obtained in current study as well as data from literature for Fe-C alloys. Finally, it is shown that the “subunits” play no role in the lengthening process of bainite.

QC 20170523

APA, Harvard, Vancouver, ISO, and other styles

31

Lewis, Colin Andrew. "Prediction of thermal stress and strain generated during the quenching of low-alloy steel." Thesis, Sheffield Hallam University, 1990. http://shura.shu.ac.uk/19954/.

Full text

Abstract:

The free edge of a quenched plate is subject to zero stress in a direction perpendicular to this edge. Therefore the thermal stresses set up in such a component must be modified in the vicinity of the edge in order to allow the required stress configuration to be produced. This is referred to as the 'edge effect' and its magnitude is conventionally estimated by the well-known Saint Venant Principle. However a detailed understanding of the variation in stress in such a specimen is not well understood and it has been the objective of the present programme to make a detailed elastic/plastic analysis of the stress generation process using a finite element method. To this end a disc specimen has been considered, so that both experimental and theoretical estimates of the stress fields are not influenced by the presence of sharp corners, which lead to a very complex stress system. The stress generation process has been followed by a finite element axisymmetric model. The use of such a plane strain representation has been checked by comparison with a full 3 dimensional elastic analysis, at a very early stage in the process when plastic flow was not present. The results obtained by the two methods of calculation were in good agreement and justify the use of the plane strain model. The finite element programme calculated the thermal history of the specimen by the Crank-Nicholson method, and the weighted mean technique was selected as the best method of smoothing the results. The effects of different element stress functions, and element size, as well as time and load steps have been studied and the optimum combination selected. Considerable difficulty had been experienced with the stability of the results, which was found to be due to limitations in the BERSAFE finite element package. The elimination of this problem led to a situation where successive stages in the stress generation process were calculated and examined with confidence, although great care was required to balance the time step with the thermal loading step. The results from this model in the central region of the plate were ingood agreement with those results reported by earlier workers. The complex variation of stress distribution predicted by the model asthe free edge is approached has been examined and justified against theclassical governing equations. This includes non-linear decay of in-plane stresses and the development of axial and shear stresses near the edge of the plate. A further product of this work has been an evaluation of the development of plastic zones during the quench process. Although the effect of the edge on the inplane stresses differs with axial position in the plate, the derivation of an overall edge correction factor (which is a mean ratio of average stress to the stress on the axis) provides a value which is consistent with the Saint Venant Principle. Therefore, it is concluded that the use of edge correction factors based on the linear decay of in-plane stresses from a position that is one plate's thickness from the edge is satisfactory for determining "real" body stresses from a finite difference model.

APA, Harvard, Vancouver, ISO, and other styles

32

Cowley, S. A. "Aspects of the bainite and proeutectoid cementite transformations in alloy steels." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375221.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Buchanan, Karl Graham. "The Effects of Long-Term Isothermal Ageing on the Microstructure of HP-Nb and HP-NbTi Alloys." Thesis, University of Canterbury. Mechanical Engineering, 2013. http://hdl.handle.net/10092/8210.

Full text

Abstract:

High alloy Fe-Cr-Ni-C austenitic stainless steels have become the principal alloys for use in steam-methane reforming furnaces within the petrochemical industry. Each furnace contains a large array of vertically oriented centrifugally cast tubes through which a mixture of methane and steam is flowed across a nickel-oxide catalyst in order to obtain a mixture of hydrogen, carbon monoxide and carbon dioxide and water commonly known as synthesis gas (or syngas). Generally, the tubes operate at temperatures between 850-1050°C, internal pressures between 1-3.5MPa and are expected to withstand service lives in excess of 100,000 hours. The combination of high temperatures and moderate stresses causes creep to be the dominant failure mechanism experienced by these tubes in service. The HP austenitic alloys are the latest in a series of heat resisting (H-series) stainless steels developed to provide high temperature strength, ductility, and corrosion resistance in the oxygen, carbon, and sulphur rich environments typical of these furnaces. Extensive work has been carried out to optimise HP alloys’ microstructure in order to maximise the alloy’s creep resistance. Strength increases have largely been realized through the use of niobium and/or titanium additions, which modify the primary precipitates (formed during solidification) and secondary precipitates (formed during exposure to the service temperatures). These strength increases have typically been observed during laboratory accelerated creep testing of the ‘modified’ HP alloys where the temperature and/or stress is increased to achieve failure of the material within reasonable time period (typically between 1000-2000 hours). However, since the duration of typical accelerated creep tests often represent less than 2% of the tubes’ actual service life, uncertainty surrounds the validity of using this testing method as the basis to predict the tubes actual service life. This uncertainty has largely arisen due to the significant microstructural evolution that occurs within these alloys during prolonged service exposure and is not captured within the typical accelerated testing time-frame. In the present work, the microstructures of HP alloys modified with a single addition of niobium (HP-Nb) and dual additions of niobium and titanium (HP-NbTi) have been characterized in the as-cast condition and after long-term (10,000 hours) isothermal laboratory ageing at 1000, 1050 and 1100°C. The main focus of this study is to provide further insight into the microstructural features that increase the HP-NbTi alloy’s creep resistance in comparison to the HP-Nb alloy when performing accelerated creep testing and determine if these microstructural features remain stable during long-term ageing. The microstructure and crystallography of the primary and secondary precipitates in each alloy have been studied in detail using light optical microscopy, high resolution scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (EBSD, SAD and CBED), Powder X-ray Diffraction and energy dispersive X-ray spectroscopy. Specific attention has been paid to the niobium-rich and niobium-titanium-rich phases that form as a direct result of HP alloy’s modification with niobium and titanium. The current research is part of a wider project conducted in collaboration with Quest Integrity Group Ltd. (Wellington, New Zealand) that aims to characterize the microstructural and mechanical properties of the HP-Nb and HP-NbTi alloys during long-term service exposure. The microstructural characterization presented in this thesis will subsequently be used by Quest Integrity Group to build a comprehensive understanding of the relationship between HP-Nb and HP-NbTi alloy’s microstructure and creep properties. This understanding will allow Quest Integrity Group to more accurately predict the service life of HP-Nb and HP-NbTi alloy tubes within steam-methane reforming furnaces.

APA, Harvard, Vancouver, ISO, and other styles

34

Lewis, G. "The effects of composition and microstructure on the temper embrittlement of 2.25Cr-1Mo alloy steel." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356278.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Carr, Martin J. "An investigation of hydrogen embrittlement of high strength steel due to zinc/nickel alloy electroplating." Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283258.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Smith, Ryan Thomas. "Development of a Nitrogen-Modified Stainless-Steel Hardfacing Alloy." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440156184.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Maropoulos, S. "The effect of heat treatment on structure-property relationships in a low alloy Ni-Cr-Mo-V steel." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370954.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Cogswell, Daniel J. "Statistical modelling of the transition toughness properties of low alloy pressure vessel steels." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1209/.

Full text

Abstract:

The transition toughness of low alloy steels used in pressure vessels is of key importance to establishing the safe operation of a number of structures; of these, the integrity of a nuclear reactor vessel is of greatest concern. The through life toughness of such vessels is a combination of the start of life properties and irradiation damage response of the material. Modelling of the inherent scatter of toughness measurements has received much academic interest since the mid-twentieth century and is found to be dependent on a number of metallurgical factors and failure modes; therefore, the micro-mechanisms of the ductile and brittle failure are explored and an assessment of the current best thinking on the modelling of crack arrest toughness is also considered. It has been established in this work that a highly accurate representation of a large toughness database can be achieved by the inclusion of constraint loss effects and the interaction between initiation and arrest toughness distributions.

APA, Harvard, Vancouver, ISO, and other styles

39

Pereira, Thiago Soares. "Bauschinger effect in macro and micro sized high strength low alloy pipeline steels." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7265/.

Full text

Abstract:

The Bauschinger effects in X70, X80 and X100 high strength low alloy pipeline steels were presented. The microstructure of the as-received alloys was characterized. A variety of microstructures was present across the different alloys, ranging from a refined granular ferrite with small amounts of perlite to a bainitic structure containing martensite/austenite islands, retained austenite and small cementite constituents along with a small amount carbides. Similarly, the dislocation structures varied from homogeneously distributed across the ferrite grains to clusters/walls of dislocations. Mechanical tests on macro and micro sized samples were carried out up to 1% and 2% plastic strains. A micro-device for Bauschinger test was designed and manufactured using micro-electro-mechanical-system (MEMS) technology and was incorporated onto a FIB/SEM in order to prepare the micro sized samples and perform the micro Bauschinger tests. The Bauschinger stress parameter showed that the Bauschinger effect becomes more obvious in samples with higher yield strength and also with increasing pre-strain. In addition, the Bauschinger effect remained similar on the samples of different sizes in the current study. The results indicate that the cause of the early yielding during reverse loading of these alloys is dominated by the dislocation-dislocation interaction.

APA, Harvard, Vancouver, ISO, and other styles

40

O'Brien, Evan Daniel. "Welding with Low Alloy Steel Filler Metal of X65 Pipes Internally Clad with Alloy 625: Application in Pre-Salt Oil Extraction." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469018389.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Riley, A. "The role of repassivation in the stress-corrosion cracking of low alloy steels : An electrochemical study." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371557.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Beech, S. M. "Structure-property relationships in low alloy Ni-Cr-Mo-V steels manufactured by different production routes." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370389.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Mehrabi, H. A. "Influence of tempering and normalising on the structure and properties of low alloy and plain carbon-manganese steels." Thesis, City University London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357373.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Duffey, Matthew James. "Metallurgical Characterization and Weldability Evaluation of Ferritic and Austenitic Welds in Armored Steels." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460910681.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Kannan, Manigandan. "A Study of Microstructure, Quasi-Static Response, Fatigue, Deformation and Fracture Behavior of High Strength Alloy Steels." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1417552570.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Suhr, Robert W. "The influence of surface defects and residual stress on the fatigue properties of 12%Cr and low alloy steels." Thesis, Coventry University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367123.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Nilsson, Hultén Leo. "Nitrogen Without Oxygen : The effect of ferroalloys added after vacuum treatment on cleanliness of nitrogen-alloyed tool steel." Thesis, KTH, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298093.

Full text

Abstract:

Nitrogen-alloyed tool steel is made at Uddeholms AB by adding high-nitrogen ferroalloy after vacuum degassing where introduced impurities are hard to remove. In this thesis two types of high-nitrogen ferrochromium are compared, a solid version and a powder cored wire. They are examined in crossection and 16 samples from four charges are examined with Pulse Distribution Analysis as well as systematic microscopy of polished cross sections. The PDA results missed smaller spinel inclusions shown in previous research to be detrimental. The wire form shows promise but more charges need to be evaluated before a conclusion is drawn.
Kvävelegerat verktygsstål tillverkas hos Uddeholms AB genom tillsats av kväverika ferrolegeringar efter vakumavgasning, och orenheter som introduceras i detta steg är svåra att avskilja. I den har uppsatsen jämförs två typer av kväverikt ferrokrom varav en i form av stycken och en i form av tråd med pulverkärna. De undersöks i tvärsnitt och totalt 16 prov från fyra charger undersöks med PDA (pulsfördelningsanalys) och systematisk mikroskopering i tvärsnitt. Resultaten från PDA missade mindre inneslutningar av spinell vilka tidigare har visat sig problematiska. Trådformen verkar lovande men fler charger behöver undersökas för att kunna dra en definitiv slutsats.

APA, Harvard, Vancouver, ISO, and other styles

48

Bergman, Ola. "Studies of oxide reduction and nitrogen uptake in sintering of chromium-alloyed steel powder." Licentiate thesis, KTH, Materials Science and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9555.

Full text

Abstract:

The powder metallurgy (PM) process route is very competitive for mass production of structural steel components with complex shape, due to efficient material utilisation, low energy consumption, and short overall production time. The most commonly used alloying elements are the processing friendly metals Cu, Ni and Mo. However, the prices for these metals are today high and volatile, which threatens to make the PM process less competitive compared to conventional metal forming processes. Consequently, there is a strong desire in the PM industry to increase the use of less costly alloying elements. Cr is an attractive alternative since it, besides low cost, provides high hardenability and also recyclable components. The drawback is that Cr has high affinity for oxygen, which makes oxidation and oxide reduction in PM processing of Cr-alloyed materials a challenging issue. Furthermore, the interaction between nitrogen and Cr-alloyed powder during processing is important to consider, since Cr also has high nitrogen affinity and is prone to form nitrides.

The aim of the research work presented in this thesis was to study oxide reduction and nitrogen uptake in sintering of Cr-alloyed steel powder. Water-atomized powder grades pre-alloyed with 1.5-3% Cr were used as test materials. Sintering experiments were performed in N₂/H₂ (90/10) atmospheres with test bars pressed to density 7.0-7.2 g/cm3. The oxygen content of the sintering atmosphere was varied and different sintering temperatures and cooling rates were applied. The experimental study has been complemented with thermodynamic calculations using the software Thermo-Calc.

The oxygen partial pressure should be below 4 x 10^-18 atm in order to have reducing conditions during sintering at 1120°C of steel powder pre-alloyed with 3% Cr. With graphite added to the powder, conditions are reducing at higher oxygen partial pressures (up to 10^-16 atm) due to favourable conditions locally in the material. Sintering at 1120°C for 30 minutes leads to incomplete reduction of Cr-oxides in the Cr-alloyed PM grades, but remaining oxides are not detrimental for mechanical properties of the PM components. Increased sintering temperature is beneficial for the oxide reduction kinetics and practically all oxides are reduced after sintering for 30 minutes above 1200°C. Nitrogen uptake by Cr-alloyed steel powder from N₂-based sintering atmospheres is strongly dependent on the cooling rate applied after sintering. No nitrides appear in the sintered material and mechanical properties are not affected when normal cooling rates (0.5-1°C/s) are applied. Very low cooling rates (such as 0.05°C/s) may lead to grain boundary precipitation of Cr-nitrides in the sintered material.

APA, Harvard, Vancouver, ISO, and other styles

49

Alexandre, Rex T. "Induction Bending of Internally Clad Steel Pipes: Failure Mechanisms & Processing Parameter Optimization in Ni-base Alloy Weld Overlays." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480422106975311.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Puthucode, Rahul. "Neutralization of acidic wastewaters with the use of landfilled Electric Arc Furnace (EAF) high-alloyed stainless-steel slag : An upscale trial of the NEUTRALSYRA project." Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-258901.

Full text

Abstract:

The landfilling of slag obtained from the high alloyed Electric Arc Furnace (EAF) steel making process, constitutes an environmental treat for society as well as an economical problem for the companies producing it, due to the costs related to waste management practices. Conventional methods of slag recycling are abundantly used among the steelmaking business, but due to their particular physical properties, high- alloyed EAF slags cannot be properly valorized. Moreover, the pickling process that high-alloyed EAF steels undergo to, generates acidic wastewaters, that need to be collected and neutralized, before they can be recirculated into the natural water streams. For such a task, steel mills currently utilize slaked lime (a Ca rich mineral) to raise the pH and to remove any metal particles dissolved into the wastewaters. Slag contains high amount of Ca; therefore, it has already been tested as a slaked lime replacement. In fact, previous studies conducted at the Material Science and Engineering department at KTH Royal Institute of Technology showed, on a laboratory scale, that slag has the potential to replace lime for the neutralization and purification of the acidic wastewaters. This Master’s thesis project aims at upscaling the volumes of wastewaters to be tested, about 70 to 90 folds of the one from previous research, bridging the gap between laboratory tests and the industrial scale. The thesis is divided into three tranches, a first part where a water-salt solution conductivity trials were carried out, to model the behavior or slag dispersion in the acidic wastewaters. After the results obtained from the conductivity trials, neutralization trials with slag and the lime product currently in use by the company, were carried out at the neutralization plant in Outokumpu Stainless, Avesta (Sweden). The neutralization trials were carried out with 70 and 90 liters of acidic wastewaters and in order to perform the trials on site, the slag sample was dried and later sieved to a particle size of less than 350μm. Moreover, data was analyzed and compared to previous studies in order to have a clearer understanding regarding the neutralization efficiency of the slag, especially whether or not the technology would had worked on upscaled volumes. Additionally, the project checked if it was possible to find a generalized relationship between the mass of slag and volume of wastewaters required for the neutralization process. Slag demonstrated to be able to buffer the pH to the target values of 9, while also showing an almost linear trend compared to previous studies. The reaction progress between slag, lime, and the acidic wastewaters was also analyzed.
Deponering av slagg som erhållits från den höglegerade ljusbågsugn (EAF) stålframställningsprocessen utgör en miljömässig behandling för samhället och ettekonomiskt problem för de företag som producerar den på grund av kostnaderna för avfallshantering. Konventionella metoder för återvinning av slagg används i storutsträckning bland stålindustrin, men på grund av deras speciella fysiska egenskaper kan höglegerade EAF-slaggen inte värderas ordentligt. Dessutom produceras sura avloppsvatten av betningsprocessen som höglegerade EAF-stål genomgår som sedan måste samlas in och neutraliseras innan de kan återcirkuleras i det naturliga vattnet. För en sådan uppgift använder stålfabriker för närvarande släckt kalk (ett Ca-rikt mineral) för att höja pH-värdet och för att avlägsna alla metallpartiklar som löses upp i avloppsvattnet. Slaggen innehåller hög mängd Ca och därför har den testats som en ersättning till släckt kalk. Tidigare studier utförda vid avdelningen materialvetenskap och teknik vid Kungliga Tekniska Högskola visade på laboratorieskala att slagg har potential att ersätta kalk för neutralisering och rening av sura avloppsvatten. Detta examensarbete syftar till att skala upp volymerna av avloppsvattnet som ska testas till cirka 70–90 gånger av den från tidigare forskning, och därav fylla ut bryggan mellan laboratorietester och industriell skala. Avhandlingen är uppdelad i tre delar, Första delen innehåller försök på ledningsförmåga i en vatten-saltlösning som genomfördes för att modellera beteende eller slaggspridning i sura avloppsvatten. Efter de resultat som erhållits från konduktivitetsmätningarna genomfördes neutraliseringsförsök med slagg och kalk som för närvarande används av företaget vid neutraliseringsanläggningen i Outokumpu Stainless, Avesta (Sverige). Neutraliseringsförsöken genomfördes med 70 och 90 liter sura avloppsvatten och för att utföra experimenten på plats torkades slagg provet och siktades senare till en partikelstorlek på mindre än 350 μm. Dessutom analyserades data och jämfördes med tidigare studier för att få en tydligare förståelse för slaggens neutraliseringseffektivitet, särskilt huruvida tekniken skulle ha fungerat på större volymer, och även om det också var möjligt att hitta ett generaliserat samband mellan mängden slagg och volym avloppsvatten som krävs för neutraliseringsprocessen. Slagget visade sig kunna buffra pH till målvärdena 9, samtidigt som den visade en nästan linjär trend jämfört med tidigare studier. Reaktionsförloppet mellan slaggkalk och de sura avloppsvattnen analyserades också.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Steel alloys – Metallurgy'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles