Academic literature on the topic 'Powder metallurgy. eng'
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Journal articles on the topic "Powder metallurgy. eng"
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Zhao, Lei, Mengna Zhang, Zihan Yu, Guojun Ma, Bin Ma, and Peipeng Jin. "Corrigendum to “Abnormal twinning behaviors in ZK60 alloy by powder metallurgy process” [Mater. Sci. Eng., A 779 (2020) 139145]." Materials Science and Engineering: A 805 (February 2021): 140799. http://dx.doi.org/10.1016/j.msea.2021.140799.
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Novák, Pavel. "Advanced Powder Metallurgy Technologies." Materials 13, no. 7 (April 8, 2020): 1742. http://dx.doi.org/10.3390/ma13071742.
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Powder metallurgy is a group of advanced processes for the synthesis, processing, and shaping of various kinds of materials. Initially inspired by ceramics processing, the methodology comprising of the production of a powder and its transformation to a compact solid product has attracted great attention since the end of World War II. At present, there are many technologies for powder production (e.g., gas atomization of the melt, chemical reduction, milling, and mechanical alloying) and its consolidation (e.g., pressing and sintering, hot isostatic pressing, and spark plasma sintering). The most promising ones can achieve an ultra-fine or nano-grained structure of the powder, and preserve it during consolidation. Among these methods, mechanical alloying and spark plasma sintering play a key role. This Special Issue gives special focus to the advancement of mechanical alloying, spark plasma sintering and self-propagating high-temperature synthesis methods, as well as to the role of these processes in the development of new materials.
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Danninger, Herbert. "Perspectives of Powder Metallurgy in the 2020s." Advanced Engineering Forum 34 (October 2019): 18–27. http://dx.doi.org/10.4028/www.scientific.net/aef.34.18.
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In the automotive industry there is a clear trend towards alternative drivetrain systems, away from the classical internal combustion – gasoline or diesel - engines. This poses a challenge to the traditional markets of powder metallurgy, the ferrous precision parts for automotive engines and transmissions which form the major tonnage of today’s powder metallurgy [1, 2], but also the hardmetal tools for machining automotive components from stock material or for finishing [3]. To counter these trends, powder metallurgy can rely on its high flexibility regarding materials, geometries, processing and properties and finally applications, which enables PM to adapt itself to changing requirements in a changing industrial environment [4]. In the present article, examples are given both for PM precision parts and hardmetals but also functional materials such as soft magnetic composites. It is shown that the potential of ferrous PM parts regarding mechanical performance is still higher than currently used, high and graded density being attractive ways [5]. Also the use of advanced alloying systems offers economical and technical advantages and should enable PM to enter non-automotive markets for precision parts. In the hardmetal branch, non-automotive applications, e.g. in construction and mining, should be considered while from the material viewpoint replacing tungsten and in particular Co as binder metal are intensely studied. PM functional materials such as Fe-Ni, Fe-Co and in particular soft magnetic composites will find markets in electrical drive systems [6], enabling new designs for electric motors. On the other end of the spectrum, superhard rare earth magnets are regularly produced by the powder route. Finally, the multitude of additive manufacturing techniques offers chances for powder metallurgy since most of these processes start from metal powders [7]. In addition to the well known laser and electron beam based “direct” AM systems, also indirect, binder-based, variants are attractive, avoiding many problems encountered with the direct systems and enabling transfer of knowhow accumulated in metal injection moulding. In general, future will show how many other technologies and products has to offer in addition to the classical press-and-sinter routes which however will remain for their specific product groups. when designing your figures and tables, etc
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Danninger, Herbert, Raquel de Oro Calderon, and Christian Gierl-Mayer. "Oxygen Transfer Reactions during Sintering of Ferrous Powder Compacts." Advanced Engineering Forum 27 (April 2018): 3–13. http://dx.doi.org/10.4028/www.scientific.net/aef.27.3.
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Powder metallurgy products may be started from powders with widely varying oxygen affinity. Thus the natural oxygen content of the powder compacts also varies in reducibility in the early stages of sintering. Here it is shown that prealloyed powders containing Cr require higher temperatures for oxygen removal than e.g. unalloyed or Ni-Cu alloyed grades. In case of powder mixes of base iron powder with Cr, Mn or Si, oxygen transfer from Fe to the additive powders may occur during heating up to sintering temperature, the “internal getter effect”. A similar effect can be observed in Cr prealloyed powders in which iron oxides initially present on the powder surfaces are transformed to more stable oxides in a fairly early stage of heating. Finally, also the formation of CH4observed when sintering alloy steels containing Si, Mn or Cr in H2can be attributed to an oxygen transfer effect.
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Ho, Ching Yen, Yu Hsiang Tsai, and Feng Ming Sui. "Thermal Transport in the Copper Powders with Nanometer and Micrometer Particles." Advanced Materials Research 126-128 (August 2010): 952–56. http://dx.doi.org/10.4028/www.scientific.net/amr.126-128.952.
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This paper investigates effects of particle size on heat transfer in copper powders. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. Nanosized particles possess characteristic physical and chemical properties different from those of bulk materials due to the confinement of electrons, excitons, and photons into small volumes. Therefore it is valuable to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The powder is wrapped up in the slender tube. One end of the slender tube filled with powder is connected to the low constant-temperature reservoir and the other end is kept at room temperature. The temperature histories at the 1cm location of the slender tube from the low constant-temperature reservoir are recorded using thermal couples. Powders of particles with the sizes 50nm and 5000nm are employed in this experiment. The results show that the thermal diffusion in the 50nm Cu powder is faster than that in the 5000nm Cu powder.
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Ho, Ching Yen, Cheng Sao Chen, and Yu Hsiang Tsai. "Experiments on Heat Transfer in Fe Micrometer and Nanometer Powders." Applied Mechanics and Materials 66-68 (July 2011): 2148–52. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.2148.
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This paper investigates characteristics of heat transfer in Fe micrometer and nanometer powder. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. Nanosized particles possess characteristic physical and chemical properties different from those of bulk materials due to the confinement of electrons, excitons, and photons into small volumes. Therefore it is valuable to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The powder is wrapped up in the slender tube. One end of the slender tube filled with powder is connected to the low constant-temperature reservoir and the other end is kept at room temperature. The temperature histories at the 1cm location of the slender tube from the low constant-temperature reservoir are recorded using thermalcouples. Powders of particles with the diameter sizes 20nm and 5000nm are employed in this experiment. The results show that the thermal diffusion in the 20nm Fe powder is faster than that in the 5000nm Fe powder.
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Danninger, Herbert. "What Will Be the Future of Powder Metallurgy?" Powder Metallurgy Progress 18, no. 2 (November 1, 2018): 70–79. http://dx.doi.org/10.1515/pmp-2018-0008.
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Abstract Traditionally, powder metallurgy has been based on two major industrial sectors – ferrous precision parts and hardmetals. Both of them relied heavily on the automotive industry, with focus on internal combustion engines. Today, there is an increasing trend towards alternative drivetrain systems, and powder metallurgy faces the challenge to find new applications to replace those lost with the decrease of classical internal combustion drives. In this presentation it is shown that the main strength of powder metallurgy lies in its enormous flexibility regarding materials, geometries, processing and properties. This enables PM to adapt itself to changing requirements in a changing industrial environment. Examples given are PM parts in alternative drivetrain systems, new alloying concepts and processing routes offering distinct advantages. With hardmetals, innovative microstructures as well as sophisticated coatings offer increased lifetime, applications ranging from metalworking to rockdrilling and concrete cutting. A particularly wide area is found in functional materials which range from components for high power switches to such for fuel cells. Soft and hard magnets are accessible by PM with particularly good properties, PM having in part exclusivity in that respect, such as for NdFeB superhard magnets as well as soft magnetic composites (SMCs). Metal injection moulding (MIM) is gaining further ground, e.g. in the medical area which is a fast-growing field, due to demographic effects. Finally, most additive manufacturing techniques are powder based, and here, the knowledge in powder handling and processing available in the PM community is essential for obtaining stable processes and reliable products. Conclusively it can be stated that PM is on the way to fully exploit its potential far beyond its traditional areas of applications.
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Ho, Ching Yen, Yu Hsiang Tsai, and Mao Yu Wen. "Experimental Study on the Heat Transfer in the Al Powder." Advanced Materials Research 83-86 (December 2009): 953–58. http://dx.doi.org/10.4028/www.scientific.net/amr.83-86.953.
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Nanometer-sized particles possess characteristic physical and chemical properties different from those of bulk materials due to an increase in surface-to-volume ratios as well as of confinement of electrons, excitons, and photons into small volumes. Therefore it is worthwhile to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The heat transfer in the powder composed of nanoparticles is experimentally investigated in this paper. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. The powder is wrapped up in the slender tube made of insulating material. One end of the slender tube filled with powder is maintained at temperature 0°C and the other end is kept at room temperature. The temperature histories at two different locations in the slender tube are recorded using thermal couples. The results show that the thermal diffusivity in the powder composed of nanoparticles is larger than that in bulk material. The pressure on the Al powders enhances the rate of heat transport due to the increase of contact area for thermal conduction.
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Jiang, Z., C. Lucien Falticeanu, and I. T. H. Chang. "Warm Compression of Al Alloy PM Blends." Materials Science Forum 534-536 (January 2007): 333–36. http://dx.doi.org/10.4028/www.scientific.net/msf.534-536.333.
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With the onging trend of reducing the weight of automotive parts, there is also an increasing trend in the use of light alloys. Recently, aluminum powder metallurgy has been the subject of great attention due to the combination of the lightweight characteristics of aluminium and the efficient material utilisation of the powder metallurgical process, which offer attractive benefits to potential end-users. Conventional press and sinter route of non-ferrous P/M products are based compaction at room temperature prior to the sintering cycle. However, warm compaction process has successfully provided increased density in ferrous powder metallurgy parts, which contributes to better mechanical properties and consequently overall performance of those parts. This study is aimed at exploring the use of warm compaction process to aluminium powder metallurgy. This paper presents a detailed study of the effect of warm compression and sintering conditions on the resultant microstructures and mechanical properties of Al-Cu-Mg-Si PM blend.
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Málek, Jaroslav, Jiří Zýka, František Lukáč, Jakub Čížek, Lenka Kunčická, and Radim Kocich. "Microstructure and Mechanical Properties of Sintered and Heat-Treated HfNbTaTiZr High Entropy Alloy." Metals 9, no. 12 (December 7, 2019): 1324. http://dx.doi.org/10.3390/met9121324.
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High entropy alloys (HEAs) have attracted researchers’ interest in recent years. The aim of this work was to prepare the HfNbTaTiZr high entropy alloy via the powder metallurgy process and characterize its properties. The powder metallurgy process is a prospective solution for the synthesis of various alloys and has several advantages over arc melting (e.g., no dendritic structure, near net-shape, etc.). Cold isostatic pressing of blended elemental powders and subsequent sintering at 1400 °C for various time periods up to 64 h was used. Certain residual porosity, as well as bcc2 (Nb- and Ta-rich) and hcp (Zr- and Hf-rich) phases, remained in the bcc microstructure after sintering. The bcc2 phase was completely eliminated during annealing (1200 °C/1h) and subsequent water quenching. The hardness values of the sintered specimens ranged from 300 to 400 HV10. The grain coarsening during sintering was significantly limited and the maximum average grain diameter after 64 h of sintering was approximately 60 μm. The compression strength at 800 °C was 370 MPa and decreased to 47 MPa at 1200 °C. Porosity can be removed during the hot deformation process, leading to an increase in hardness to ~450 HV10.
Dissertations / Theses on the topic "Powder metallurgy. eng"
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Santos, Dalcy Roberto dos. "Obtenção da liga Ti-35Nb por metalurgia do pó para utilização em próteses ortopédicas /." Guaratinguetá : [s.n.], 2006. http://hdl.handle.net/11449/105374.
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Resumo: A liga Ti-35Nb e uma liga da classe beta que apresenta baixo modulo de elasticidade e uma composicao quimica adequada para a utilizacao em implantes. Essa liga e composta apenas por elementos considerados biocompativeis e apresenta modulo de elasticidade mais proximo aos dos tecidos osseos do que as ligas convencionalmente utilizadas. O niobio e um importante estabilizador da fase À e quando presente em um teor entre 35 a 50% produz uma composicao de baixo modulo quando ligado ao titanio. A liga Ti-35Nb foi obtida por metalurgia do po utilizando a mistura dos pos elementares na forma de hidretos de titanio e niobio, obtidos por hidrogenacao e moidos por 12 e 36 horas. A mistura elementar da liga Ti-35Nb foi compactada por prensagem uniaxial e isostatica a frio, com subsequente densificacao por sinterizacao entre 700 e 1500 C. A evolucao microestrutural na sinterizacao mostrou que a estabilizacao da fase ocorre pela difusao do niobio na estrutura do titanio e a 1500o C a liga e composta de uma estrutura com predominancia de fase À e pouca fase ¿, com 97,5% da densidade teorica. As propriedades mecanicas avaliadas por ensaios de flexao apresentaram modulo elastico de 78,5 GPa e e tensao de ruptura maxima de 818,8 MPa. Para o ensaio de tracao os resultados foram de 80,7 GPa, para o modulo elastico e 600,0 MPa para a tensao de ruptura maxima. A dureza avaliada por identacao Vickers alcancou 394,8 Hv.Abstract: Ti-35Nb is classified as a â titanium alloy and is believed to identify an optimal low modulus and chemical composition for implant applications, with high strength and biocompatibility. Implants of this alloy have a modulus of elasticity closer to that of bone than other typically-used metal alloys and do not include any elements which have been shown or suggest as having short term potential adverse effect. Niobium is an important â-phase stabilizer and when present in preferred quantities of from about 35-50% produces a low modulus composition when alloyed with titanium. The Ti- 35Nb alloy was produced by powder metallurgy through a mixture of hydride elementary powders (Titanium and Niobium) milled for 12 and 36 hours. Samples were produced from that mixture followed by uniaxial and cold isostatic pressing with subsequent densification by isochronal sintering between 700 up to 1500° C, in vacuum. The microstructural evolution on sintering showed that niobium particles play an important role on phase stabilization by its difusion through Titanium structure, The alloy, produced at 1500° C, presents 97,5 % of the theoretical density and shows a little amount of á-phase with a predominance of â-phase. The mechanical properties were evaluated by flexural and tensile tests. Through flexural test was obtained a elastic modulus of 78,5 GPa and a rupture stress of 818,8 MPa.. The results from tensile test were 80,7 GPa for elastic modulus and 600,0 MPa for rupture stress. The Vickers indentation micro hardness reach 394,8 Hv.
Orientador: Marcelo dos Santos Pereira
Coorientador: Carlos Alberto Alves Cairo
Banca: Humberto Lopes Rodrigues
Banca: Pedro Paulo de Campos
Banca: Francisco Piorino Neto
Doutor
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Nogueira, Rosiane de Castro. "Estudo do efeito do tempo e do meio de moagem de alta energia para obtenção de pós nanométricos de hidretos de titânio e nióbio /." Guaratinguetá : [s.n.], 2009. http://hdl.handle.net/11449/94419.
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Resumo: As ligas Ti-Nb são apropriadas para uso em implantes devido a sua alta resistência e biocompatibilidade. Um dos métodos de obter estas ligas é a metalurgia do pó, pois ele permite obter peças próximas ao seu formato final. Teorias indicam que a razão de densificação varia inversamente como uma função do tamanho da partícula. O aumento de interesse na fabricação de materiais nanoestruturados (partículas menores que 100 nm) é devido à possibilidade de obter um material sinterizado em um tempo menor e em temperaturas mais baixas, com uma melhor densificação do que pós convencionais, pois é mais reativo. Neste trabalho, após hidrogenação e moagem de alta energia por até 60 min, obteve-se pós de hidreto de titânio e hidreto de nióbio, com estrutura ultrafina/nanométrica, que auxilia o processo de difusão numa posterior etapa de sinterização. Meios de moagem de diferentes materiais (aço inoxidável e nitreto de silício - Si3N4) foram usados. Independentemente dos meios de moagem usados, o material obtido apresentou aproximadamente 5% das partículas com valores cumulativos de tamanhos de até 100 nm. Mas, o material obtido do recipiente de Si3N4 após 20 min de moagem apresentou uma maior porcentagem de partículas com diâmetros médios equivalentes entre 40 nm e 1000 nm, correspondente a 29%.Abstract: The Ti-Nb alloys are suitable for use in implants due to their high tensile strength and biocompatibility. One of the methods to obtain these alloys is the powder metallurgy, because it allowing to get pieces closer to near-net-shape. Theories showing that the densification rate range conversely like a function of the grain size. The great interest in the manufacturing of nanostructured materials - NsM (particles smaller than 100 nm) is due to possibility to obtain a sintered material in a smaller time and in more low temperatures than conventional powders, with the best densification, because it is more reactive. In this work, after hydrogenation and use of higher energy ball milling by until 60 min, were obtained powders of titanium hydride and niobium hydride, with ultra-fine/nanometric structure, what help in the diffusion process during a later stage of sintered. Milling medium of different materials (stainless steel and silicon nitride - Si3N4) were used. Independently of the grinding medium used, the material obtained exhibit approximating 5% of the particles with the cumulative values of size until 100 nm. But, is the possible to verify that the material obtained of the Si3N4 vessel, after milling by 20 min, exhibited a greater percentage of particles with average equivalent diameters between 40 nm and 1000 nm, than correspond to 29%.
Orientador: Tomaz Manabu Hashimoto
Coorientador: Carlos Alberto Alves Cairo
Banca: Antonio Jorge Abdalla
Banca: Alfeu Saraiva Ramos
Mestre
Conference papers on the topic "Powder metallurgy. eng"
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Sutton, Ben, and David Gandy. "Assessment of Powder Metallurgy-Hot Isostatic Pressed Nozzle-to-Safe End Transition Joints." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65776.
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Dissimilar metal nozzle-to-safe end welds represent a complex manufacturing operation for nuclear reactor fabrication. Transitioning from a low alloy steel nozzle to corrosion-resistant reactor coolant system piping systems requires weld buttering, an intermediate heat treatment, and a dissimilar metal weld between the nozzle buttering and safe-end. The process can be both time consuming and costly, and often provides difficulties for inspection of welds in the field. Through the use of powder metallurgy and hot isostatic pressing (PM-HIP), a series of transition joint configurations have been evaluated that could reduce the complexity of nozzle-to-safe end fabrication by eliminating fusion welding from the process. Test coupons of SA508 low alloy steel have been joined via PM-HIP to either 316L SS or 347NG SS using various powder metal interlayer materials (Alloy 82, Nb-modified Alloy 600 (600M), Alloy 690, and 316L SS). The microstructural evolution and mechanical performance of the joints have been evaluated following a post-HIP solution anneal, quench and temper heat treatment. Particular attention was given to evaluating bond-line regions via Charpy V-notch impact testing, tensile testing, microhardness, optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Results demonstrate that multiple transition layer configurations are capable of meeting the acceptable tensile and impact energy specifications of the two parent base material substrates. Interface impact toughness and ductility were dependent upon secondary phase precipitation within the diffusion region of the joints and presence of non-metallic inclusions. This assessment demonstrates that acceptable joint performance is achievable through proper material selection and should be considered for DMW applications in the future.
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Ho, C. Y., C. S. Shih, M. Y. Wen, and C. Ma. "Heat Transport in the Al Nanopowder." In ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/detc2008-49238.
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The heat transport in the Al nanopowder is experimentally investigated in this paper. The understanding for thermal behavior of the Al powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. The powder is wrapped up in the slender tube made of insulating material. One end of the slender tube filled with powder is maintained at temperature 0°C and the other end is kept at 24°C. The temperature histories at two different locations in the slender tube are recorded using thermal couples. The results show that the temperature in the powder composed of nanoparticles descends more quickly than that in bulk material. The increase of pressure on the powders enhances the heat transfer.
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Hanuman, N. S. V. N., P. Gangadhara Rao, B. Sudheer Kumar, and N. Karthik. "On modeling the CNC end milling characteristics of Al-7075/WC powder metallurgy composites." In INTERNATIONAL CONFERENCE ON FUNCTIONAL MATERIALS, CHARACTERIZATION, SOLID STATE PHYSICS, POWER, THERMAL AND COMBUSTION ENERGY: FCSPTC-2017. Author(s), 2017. http://dx.doi.org/10.1063/1.4990252.
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Shard, Abhinav, Deepshikha, Vishal Gupta, and M. P. Garg. "Material removal rate during powder metallurgy Cu-Ti electrodes in electrical discharge machining of EN9 steel." In 3RD INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC-2019). AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0001826.
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Lisovskaya, Tatyana A., Alexander S. Maklakov, Roman A. Lisovsky, and Tao Jing. "Linearization Small Deviation Model of Active Front End Rectifier." In 2020 Russian Workshop on Power Engineering and Automation of Metallurgy Industry: Research & Practice (PEAMI). IEEE, 2020. http://dx.doi.org/10.1109/peami49900.2020.9234369.
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Ioffe, Igor, Rustam Iunusov, and Aleksey Kostylev. "The Comparative Analysis of Processes in Active Front End (AFE) for Cases of Different Power Sources." In 2019 IEEE Russian Workshop on Power Engineering and Automation of Metallurgy Industry: Research & Practice (PEAMI). IEEE, 2019. http://dx.doi.org/10.1109/peami.2019.8915097.
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Kyffin, William, David Gandy, and Barry Burdett. "A Systematic Study of the Material Performance of Hot Isostatically Pressed Type 316L Stainless Steel Powder for the Civil Nuclear Sector." In 2018 26th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icone26-81438.
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Hot Isostatic Pressing (HIP) of type 316L stainless steel powder has been an established manufacturing practice for more than twenty-five years in the oil and gas sector and more recently in the naval defence sector. To demonstrate the capability of the powder metallurgy HIP (PM/HIP) for nuclear power applications a systematic study of 316L commercial powder production, encapsulation/consolidation providers and selected HIP parameters was undertaken by the Nuclear AMRC in collaboration with the Electric Power Research Institute (EPRI). In the study, the 316L powder specification limited the oxygen content of the powder to under 130 parts per million (ppm), which reflects the improvements that commercial powder suppliers have been making over the past decade to ensure greater powder cleanliness. The test programme assessed powder supply, HIP service provider and HIP sustain time. Excellent test results were achieved across the full range of variables studied with all billets meeting the specification requirements of ASTM A988 and additional requirements imposed based on nuclear manufacturing standards. Significantly, the study demonstrated the robustness of the PM/HIP supply chain, as material produced via differing HIP service providers resulted in very consistent material properties across the destructive test programme. Furthermore, no significant difference in material properties were noted for material HIP’ed between 2–8 hours hold time, suggesting that the HIP process window is large. Both these results are significant from an end-user standpoint as they highlight the uniformity of the process through the full manufacturing cycle from powder procurement to destructive testing. Despite all material passing specification requirements, some property variation was noted for differing powder suppliers. Considering the systematic approach, this was attributed to powder composition, with both low oxygen and high nitrogen contents contributing to improvements in Charpy impact strength and tensile strength respectively.
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Dobrzanski, Janusz, and Jerzy Pasternak. "Reliability and Safety of the Power Equipment in Respect of Properties Evaluation of Welded Joints Made From New Generation Creep-Resisting Steels." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77044.
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The modernisation of power generation sector has involved the construction of new power units, having supercritical parameters e.g. 580/ 600°C with 280bar, and calculated efficiency of approx. 43%. The new boilers are supercritical ones of capacities 440MW and 840MW. Their investors expect that new creep-resistant steels to be used in order to comply with the operational requirements, as well as to assure the appropriate reliability and safety of the boiler equipment in operation. Authors describe a co-operating process has been made with RAFAKO S.A. the Institute for Ferrous Metallurgy in Gliwice, the Institute of Welding and the Silesian Technical University in Katowice, for several years now, initiating research and development programmes. This paper contains selected information, test results and their evaluation before implementation of the new creep-resistant steels, including evaluation of: - working parameters and temperature conditions of main boiler components, which influence reliability and safety procedures, - base material, welded joints and HAZ structure by means of LM and SEM methods in the welding technology implementation process, - the requested level of mechanical properties, including corrosion mechanisms, - corrosion and creep-resistance results, - loss of service life for selected evaporator and steam superheater components, as crucial elements in evaluation of reliability and safety of boiler equipment.
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Zielinski, Stephen M., Anthony A. Sansone, and Rusi P. Taleyarkhan. "Melt-Water Explosive Interactions: Triggering and Suppression." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10258.
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Under appropriate thermal-hydraulic conditions the combination of a hot fluid (e.g., molten metals) and a cold vaporizing fluid (e.g. water) can be made to undergo spontaneous or externally assisted (e.g., via trigger shock) onset of explosive interactions (via destabilization of the interfacial vapor layer) and resulting in rapid heat transfer, phase change, pressure buildup and melt fragmentation. Energetic melt-water explosions are a well-established contributor to the risk of nuclear reactor systems such as the infamous Chernobyl Accident. The prevention of triggering of such interactions in nuclear systems is of paramount importance. However, once the fundamentals are understood, it may be possible to not only intensify but more importantly, to control the intensity of the interaction. The control and intensification of explosive interactions can become of considerable importance in the areas covering variable thrust propulsion with tailored pressure profiles, for enhancing rapid heat transfer, and also for powder metallurgy (i.e., supercooled powder production in which the resulting materials may turn super-plastic with enhanced ductility and strength). This paper discusses results of experiments conducted with various molten metals specifically, tin, galinstan and aluminum interacting with water, with and without non-condensable gases such as hydrogen. It is found that under the appropriate combination of conditions, spontaneous and energetic liquid water to vapor phase changes can be readily introduced within milliseconds if the hot metal fluid is tin or galinstan (but not for aluminum) including the timed feedback of shocks generated from earlier explosions leading to chain-type reaction fronts propagating through mixtures. Using 3–10 g metal masses of tin or galinstan spontaneously exploding in water, shock over-pressures up to 12 bar (175 psig) were monitored about 4 cm from the explosion zone, accompanied with mechanical shock power levels of about 2 kW. A previously slow phase change process (viz., normal metal quenching) occurring over tens of seconds could be turned explosive to transpire within milliseconds for melt-water thermal states within the so-called thermal interaction zone (TIZ). However, it was also conclusively revealed that, for an otherwise spontaneously explosive combination of tin-water or galinstan-water, the inclusion of even trace (0.3 w/o) quantities of aluminum which generates monoatomic non-condensable gas in the interfacial layer is found to have a radical influence on stabilizing the interfacial vapor layer between hot fluid and cold fluid, thereby ensuring conclusive (100% of time) prevention of explosion triggering for all cases tested. This paper compares and presents the results obtained in this study along with insights into energetics, with gram quantity melt droplets and draws analogies with data taken for industrial scale aluminum casthouse safety conditions involving thousands of kilograms of melt. Insights drawn for adaption to industrial settings are provided for enabling physics-based prevention or initiation.
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Berglund, Tomas, and Martin Östlund. "Impact Toughness for PM HIP 316L at Cryogenic Temperatures." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-64002.
Full textAbstract:
It is well known throughout the PM HIP (Powder Metallurgy Hot Isostatic Pressing) industry that PM HIPed 316L material in general exhibit higher strength than conventional 316L. However, previous studies have shown an uncharacteristic behavior in impact toughness properties at cryogenic temperatures compared to conventional forged material. The uncharacteristic behavior consists of unexpectedly large drop in impact toughness at cryogenic temperatures which is not seen in the same extent in conventional material e.g. forged 316L. With the recent code case approval for PM HIPed 316L material, this behavior can be seen as an uncertainty regarding the performance of the material and its use in nuclear applications can therefore become limited. The behavior and underlying mechanisms is yet to be explained in detail. One possible explanation is that it is caused by oxides in the material, of which a large amount originates from oxygen picked up by the very large surface area of the powder during the manufacturing process. The correlation between impact toughness at room temperature and oxygen content is often referred to. In this study the non-metallic inclusion content is correlated to the impact properties at −196°C (−321°F), and a suggested explanation for the behavior of PM HIP 316L/316LN vs. conventional 316L is presented. The size and number of inclusions constitutes a major difference between the PM HIPed and conventional material. The results show that the size of the inclusions is significantly smaller in the PM materials compared to the conventional material and as a consequence they are present in larger numbers in the PM materials. Furthermore, the results clearly show the correlation between inclusion content and the impact toughness at cryogenic temperatures. The correlation is not as clear at room temperature where the different materials behave more similar. The suggested explanation is further supported by literature on cryogenic properties of 316L/316LN, 316L weld material and PM HIP 316LN with greatly reduced oxygen content. The impact toughness testing was performed using instrumented test equipment capable of recording load vs. displacement during testing. From this data the crack propagation and crack initiation energy can be estimated. Furthermore, it is known that grain size can influence mechanical properties. In this study no clear relationship between impact toughness and grain size could be observed. However, a correlation between the grain size and the amount of inclusions in the material was observed. It was found that larger amounts of inclusions in the PM HIPed material are correlated to a finer grain size. The results indicate that the inclusion particles inhibit grain growth during the HIP and heat treatment process by pinning of grain boundaries.