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1
Almotairy, Saud, Dong Bin Wei i Zheng Yi Jiang. "Study on Surface Roughness Transformation during Metal Rolling". Materials Science Forum 706-709 (styczeń 2012): 2517–22. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2517.
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Increasing the demand for cold rolled ultra thin strip as feedstock for miniaturized products has encouraged researchers to investigate the ways to increase the quality of such products, especially those related to strip surface roughness. Surface is known as quality factor in most of manufacturing processes. In this paper, the effect of the rolling parameters on the surface roughness transformation during metal rolling has been studied. The experimental results demonstrate that the surface roughness transformation during the metal rolling is highly affected by the designation of the processing parameters such as finishing temperature, reduction, rolling passes and lubrication. The results have been discussed to verify the validity of the new findings.
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Almotairy, Saud, Dong Bin Wei i Zheng Yi Jiang. "Study on Surface Roughness Transformation during Metal Rolling". Advanced Materials Research 418-420 (grudzień 2011): 897–902. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.897.
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Increasing the demand for cold rolled ultra thin strip as feedstock for miniaturized products has encouraged researchers to investigate the ways to increase the quality of such products, especially those related to strip surface roughness. Surface is known as quality factor in most of manufacturing processes. In this paper, the effect of the rolling parameters on the surface roughness transformation during metal rolling has been studied. The experimental results demonstrate that the surface roughness transformation during metal rolling is highly affected by the designation of the processing parameters such as finishing temperature, reduction, rolling passes and lubrication. The results have been discussed to verify the validity of the new findings.
3
Morris, J. W., D. C. Chrzan i Shigeru Kuramoto. "Anomalous Transformation-Induced Deformation in Gum Metal". Key Engineering Materials 465 (styczeń 2011): 21–28. http://dx.doi.org/10.4028/www.scientific.net/kem.465.21.
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Tensile tests of single crystals of Gum Metal (Ti-36Nb-2Ta-3Zr-0.3O (wt %)) showed, anomalously, that (1) extensive, stress-induced (bcc)”(orthorhombic) transformation occurred in a crystal pulled in the <110> direction, but no transformation was observed in crystals pulled in the <100> or <111> directions and (2) little or no transformation occurred in tensile tests of severely worked rods, which are polycrystals with very strong <110> texture. Analysis of the energetics of the ” transformation offers straightforward explanations for these results. (1) An ” precipitate has very low elastic energy if it forms as a thin plate with a habit near {11√2}. A <110> tensile load significantly decreases the energy of this plate, promoting the transformation; loading along <100> or <111> is much less effective. (2) While cold-swaged rods of Gum Metal have a strong <110> axial texture, their perpendicular planes are severely distorted, increasing the elastic energy of ” and inhibiting the transformation.
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Abro, Shahid Hussain, Muhammad Sohail Hanif i Fayaz Hussain. "On the Effect of γ-phase transformation kinetics upon microstructure response of Cold Heading Quality Steel". NUST Journal of Engineering Sciences 11, nr 2 (31.12.2018): 51–55. http://dx.doi.org/10.24949/njes.v11i2.399.
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Cold heading quality CHQ steel is a versatile form over other steels as they are used non-heat treated; their strengthening mechanism is achieved through cold heading operations. Metal is therefore stretched without applying any source of heat, metal flow during the cold heading operation must depend on grains flow which increases the mechanical properties such as strength, resistance to indentation and toughness. It is therefore necessary to form the isotropic grains before applying cold heading operation may increase the properties. Gamma phase formation during the heat treatment is crucial factor for cold operation. An effort is made in this research work to study and find out the Austenite nucleation and growth morphology of commercial CHQ steel through continuous heating experiments by utilizing lead-bath up-quenching technique at differentaustenizing temperature ranges. High class Optical Microscope Olympus GX51, scanning electron microscopy techniques have been utilized to reveal and interpret the microstructure and it was found that At the 740°C, the microstructure shows the lack of homogeneity in the structure hence cold-head-ability of CHQ steel is anisotropic but at the high temperature in austenite domain at 60sec the resultant austenite is highly homogenous due to high volume fraction of austenite has been formed then the cold-head-ability properties of CHQ steel turned to be isotropic. Keywords: Up-quenching, cold heading steel, gamma transformation, heating rate etc.
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Shen, Yan Fang, Wan Song, Xin Yu Cui i Tian Ying Xiong. "A Brief Review on TiO2 Coating Deposited by Cold Spraying". Materials Science Forum 804 (październik 2014): 111–14. http://dx.doi.org/10.4028/www.scientific.net/msf.804.111.
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TiO2is a promising photocatalyst with great potential for environment purification and energy conversion. TiO2coatings have more advantages over powders in practical use. Cold spraying is an ideal technique to fabricate TiO2coatings because of its low heat input compared with thermal sparing which may induce undesirable phase transformation from anatase to rutile. The paper will give a short introduction on recent development of TiO2coatings by cold spraying. Then, the factors affecting the quality of coating should be analyzed. And finally, the bonding mechanism of cold sprayed TiO2coating on metal substrates will also be proposed.
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Demenkova, L. G., S. A. Solodsky i D. P. Ilyashchenko. "Studies of Kinetic Plasticity Effect in High-Speed Steels under Martensite Transformation". Solid State Phenomena 303 (maj 2020): 8–14. http://dx.doi.org/10.4028/www.scientific.net/ssp.303.8.
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In the paper the authors study how the kinetic plasticity effects the temporary and residual stresses formed in instrumental steels when cooling. They also present the results of temporary stresses relaxation. This phenomenon was applied within the temperature range of the martensite transformation to reduce the cold cracking of the surfaced metal. The paper shows that the superplasticity effect emerging at the moment of martensite transformation plays the crucial role in temporary stresses relaxation.
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Chen, T. C., C. T. Hsieh i L. W. Tsay. "Fatigue Crack Growth of Cold Worked 304L Stainless Steel in Gaseous Hydrogen". Applied Mechanics and Materials 378 (sierpień 2013): 140–44. http://dx.doi.org/10.4028/www.scientific.net/amm.378.140.
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The fatigue crack growth behaviors of cold worked 304L stainless steel (SS) in air and gaseous hydrogen were evaluated, and further compared with the base plate. Cold rolling caused a rise in surface hardness and induced austenite to martensite transformation of 304L SS. Despite of testing environment, the fatigue crack growth rate (FCGR) of the cold worked specimen was higher than that of the base metal. Furthermore, both kinds of specimens were susceptible to hydrogen-accelerated crack growth. Mainly quasi-cleavage fracture related with the strain-induced martensite together with separation along twin boundaries accounted for the accelerated crack growth of the specimens in hydrogen.
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Chen, Junwei, Jie Liu, Haobin Wang, Bo Li, Quan Hu, Tianjing Shao, Ruijing Yang i in. "Experimental Study on Neutral Salt Spray Accelerated Corrosion of Metal Protective Coatings for Power-Transmission and Transformation Equipment". Coatings 13, nr 3 (21.02.2023): 480. http://dx.doi.org/10.3390/coatings13030480.
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At present, the common protection technology of power-transmission and transformation equipment is mainly coating protection and hot-dip zinc protection. However, due to the low adhesion of epoxy zinc-rich coating, and the poor compatibility with top paint, environmental pollution, complex processing, high energy consumption and other defects of the hot-dip zinc process, its development is limited. In view of the above deficiencies, new anti-corrosion coating materials and processes were investigated in this study. Zinc coatings and Al-Zn coatings were prepared on the C45 steel matrix by hot-spraying and cold-spraying processes. The macro appearance, micromorphology and phase composition analysis of the coatings were evaluated. The adhesion of the coating to the substrate after the salt-spray test was tested. The results showed that the hot dip zinc coating and hot spray zinc coating had obvious cracking after the salt-spray test. The surface structure of cold-sprayed Al-Zn coating was relatively dense after the salt-spray test. The critical load of the cold-sprayed Al-Zn coating after the salt-spray test was higher than that of the other two coatings. The corrosion resistance to salt spray of cold-sprayed Al-Zn coating was demonstrated to be better than the hot-dip zinc coating, and thus has great application prospects.
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Xikeranmu, Zilajiguli, Ji Ma i Xiaoning Liu. "Characterization of a Mn-SOD from the desert beetle Microdera punctipennis and its increased resistance to cold stress in E. coli cells". PeerJ 8 (14.02.2020): e8507. http://dx.doi.org/10.7717/peerj.8507.
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Insects have developed a complex network of enzymatic antioxidant systems for handling reactive oxygen species (ROS) generated during stress. Superoxide dismutases (SODs) play a determinant role in balancing ROS in insect. However, studies devoted to SODs functions in insects under cold stress are limited. In the present study, we attempted to identify and characterize a mitochondrial manganese SOD (mMn-SOD) from the desert beetle Micordera punctipennis (denoted as MpmMn-SOD) and explore its protective effects on bacteria cells under cold stress. MpmMn-SOD is composed of 202 amino acids with conserved domains required for metal ions binding and enzyme activity. RT-qPCR experiments revealed that the expression of MpmMn-SOD was ubiquitous but tissue-specific and was induced by cold stress. An E. coli (BL21) system was applied to study the function of MpmMn-SOD. The MpmMn-SOD gene was cloned into the prokaryotic expression vector pET-32a to generate a recombinant plasmid pET-32a(MpmMn-SOD). After transformation of the plasmid into E. coli BL21, the fusion protein Trx-His-MpmMn-SOD was overexpressed and identified by SDS-PAGE and Western blotting. Antioxidant activity assay showed that the death zones of the transformed bacteria BL21 (pET32a-mMn-SOD) were smaller in diameter than the control bacteria BL21 (pET32a). Survival curves under −4 °C showed that BL21 (pET32a-mMn-SOD) had significant enhanced cold resistance compared to BL21 (pET32a). Its SOD activity under −4 °C had a significant negative correlation (r = − 0.995) with superoxide anion O2•− content. Accordingly, under cold stress BL21 (pET32a-mMn-SOD) had lower electric conductivity and malondialdehyde (MDA) content than BL21 (pET32a). Taken together, our results showed that cold stress stimulated the expression of MpmMn-SOD in M. punctipennis. The E. coli cells that overexpress MpmMn-SOD increase their resistance to cold stress by scavenging ROS, and mitigate potential cell damage caused by ROS under cold conditions.
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Muncut, Elena, Ion Aurel Perianu, Dan Glavan i Gheorghe Sima. "Structural Analysis for Joining Dissimilar Thin Sheets with CMT (Cold Metal Transfer) Process". Advanced Materials Research 1111 (lipiec 2015): 49–55. http://dx.doi.org/10.4028/www.scientific.net/amr.1111.49.
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The work includes work steps for joining thin sheets with a thickness ranging from1.0 mm (according to EN10327-2004). The study presents the following steps: problems arising from joining with CMT weld-brazing process of galvanized low-carbon steel sheets, used as filler material CuSi3. This is due to the fact that copper induces: grain refinement by lowering the transformation temperature and precipitation hardening after rapid cooling and tempering the theoretical and experimental study of these problems leads to the possibility of combining copper with iron. This is an experiment to investigate the formation of interlayer containing intermetallic compounds, inter layer located between the molten material and the base material. An important part of the study was the optimizing of weld-brazing parameters: welding current, welding speed and dynamic correction factor Ina.Keywords: galvanized sheets steel, joining, weld-brazing CMT, preserving the zinc layer, intermetallic layer.
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Presz, W., i M. Kaczorowski. "Strengthening Mechanisms of 1H18N9T Austenitic Steel Buildups Created with Cold Forming Processes". Advanced Materials Research 23 (październik 2007): 165–68. http://dx.doi.org/10.4028/www.scientific.net/amr.23.165.
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In metal forming processes in the tool-workpiece contact area occur high pressure, surface expansion and elevated temperature. It makes ideal circumstances for braking of the lubricant film that causes a direct contact between metallic surfaces. Such a contact usually leads to buildups creation on the tool surface. These phenomena mainly result product surface damage. Damages can also refer to tool surface since the hardness of buildups can be comparable with the tool hardness. The cause of this investigation was finding the answer of the question what was the reason of extreme hardness of buildups created during bulk metal forming processes of 1H18N9T austenitic stainless steel. The studies were conducted using transmission electron microscopy (TEM). On the basis of analysis structural and electron diffraction pattern it was suggested that simultaneously to very well known strengthening mechanism like grain refinement, the additional mechanism can not be excluded. Based mostly on the electron diffraction pattern (appearance of forbidden reflexes for FCC) it is suggested that this additional mechanism could be the marthensitic transformation caused by very high plastic deformation.
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Wang, Qiang, i Ming Xing Zhang. "Review on Recent Research and Development of Cold Spray Technologies". Key Engineering Materials 533 (grudzień 2012): 1–52. http://dx.doi.org/10.4028/www.scientific.net/kem.533.1.
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Cold spray (CS) is an emerging revolutionary technology for deposition of metal or composite powders at a low temperature. High quality deposits can be produced without heating related defects, such as oxidation, phase transformation and residual tensile stress due to the shrinkage during fast cooling. The present contribution demonstrates the state of the art of CS process. Since nozzle is a key component in the CS equipment to prompt the efficiency of particle acceleration, the progress of its design is summarized. Major issues regarding to the successful adhesion of particles and corresponding interaction with substrates and existing deposits are discussed, in terms of numerical simulation and experimental observation. Current implemented CS applications are presented, and potential industrial applications are discussed. Keywords: cold spray; coatings; rapid manufacturing; particle impact; bonding mechanism; nozzle design
13
Yang, Gwon Seung, Jong Kook Lee i Woo Yang Jang. "Mechanical Properties and Microstructure Observation with Grain Refinement in CuZnAl Alloy". Materials Science Forum 569 (styczeń 2008): 173–76. http://dx.doi.org/10.4028/www.scientific.net/msf.569.173.
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A small amount of misch metal was added to CuZnAl alloy in order to study the effect of grain refinement and mechanical properties, phase transformation behavior and stabilization of martensite. It was found that the addition of misch metal was very effective for reducing the grain size. The coarse grains over 1000 μm have been refined to the size of 30 μm by the addition of 0.43wt% misch metal. The grain size of thermo-mechanically treated alloys was barely affected by cold working. The fracture strength and ductility have been significantly increased with the increase of misch metal content when tensile test is carried out below Mf temperature. Also, the fracture strength has been more increased in the case of post-quench ageing treatment than the direct quench ageing treatment. The fracture mode has been changed from transgranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal.
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Stockert, Sven, Matthias Wehr, Johannes Lohmar, Gerhard Hirt i Dirk Abel. "Development of a Laser Triangulation Gauge for High Precision Strip Thickness Control". Advanced Materials Research 1140 (sierpień 2016): 107–14. http://dx.doi.org/10.4028/www.scientific.net/amr.1140.107.
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Almost all metal strips with thicknesses of < 2 mm are produced by cold rolling. Thickness variations of cold rolled strips are caused by various factors like fluctuation in strength of the material, the eccentricity of the rolls or thickness variation of the incoming strip. As the demands concerning the thickness variation are ever increasing the Institute of Automatic Control and the Institute of Metal Forming aim at reducing the thickness tolerance of thin, cold-rolled steel and copper strips to 1 μm. As high frequency disturbances are expected, it is assumed that this goal can only be achieved by using a predictive controller in combination with a high precision strip thickness gauge and, for roll adjustment, a piezoelectric actuator in addition to the existing electromechanical actuator. The objective of this work is the constructive implementation and the testing of a thickness gauge based on laser triangulation. The gauge includes guide rollers to prevent strip vibration, a C-frame to allow an inline calibration and mechanical adjustment of the measuring range so that even flexible strip thicknesses can be measured. The designed gauge showed a high repeat accuracy of 0.4 μm for two different metal strips. Furthermore the gauge was used to investigate the dynamics of the thickness change of a steel strip at maximum rolling speed of 5 m/s using a Fourier transformation. This frequency analysis supports the need for a piezoelectric actuator that can also subsequently be dimensioned based on the obtained frequency data.
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Winnicki, Marcin. "Advanced Functional Metal-Ceramic and Ceramic Coatings Deposited by Low-Pressure Cold Spraying: A Review". Coatings 11, nr 9 (30.08.2021): 1044. http://dx.doi.org/10.3390/coatings11091044.
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Based on the recent analysis of various databases, cold spray (CS), the newest method among thermal spraying technologies, has received the unabated attention of hundreds of researchers continuously since its invention in the 1980s. The significance of CS lies in the low process temperature, which usually ensures compressive residual stresses and allows for the formation of coatings on a thermally sensitive substrate. This paper concerns the low-pressure cold spray (LPCS) variant employed for forming metal matrix composites (MMCs) with high ceramic contents and all-ceramic coatings. At the very beginning, the influence of LPCS process parameters on deposition efficiency (DE) is analysed. In the next part, the most useful feedstock powder preparation techniques for LCPS are presented. Due to the combination of bottom-up powder production methods (e.g., sol-gel (SG)) with LCPS, the metal matrix that works as a binder for ceramic particles in MMC coatings can be removed, resulting in all-ceramic coatings. Furthermore, with optimization of spraying parameters, it is possible to predict and control phase transformation in the feedstock material. Further in the paper, differences in the bonding mechanism of metal–ceramic mixtures and ceramic particles are presented. The properties and applications of various MMC and ceramic coatings are also discussed. Finally, the exemplary direction of CS development is suggested.
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Xiong, Zhiliang, Wenjian Zheng, Liping Tang i Jianguo Yang. "Self-Gathering Effect of the Hydrogen Diffusion in Welding Induced by the Solid-State Phase Transformation". Materials 12, nr 18 (7.09.2019): 2897. http://dx.doi.org/10.3390/ma12182897.
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The hydrogen diffusion in welding was investigated by using thermal-mechanical-hydrogen diffusion sequential coupled procedures based on finite element method. A self-gathering effect induced by the solid-state phase transformation was discovered. Because of the self-gathering effect, the hydrogen concentration in weld metal was accumulated to a peak value which can be larger than the initial hydrogen concentration in molten pool, and subsequently the hydrogen concentration in heat affect zone was redistributed. In multi-pass welding, the gathered effect not only happened inside a weld pass, but also in the inter-pass, which further increased the sensitivity of the hydrogen-assisted cold cracking. Controlling should be adopted to restrain the hydrogen accumulation. Welding stress evolution during the solid-state phase transformation process had limited effect on the hydrogen diffusion.
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Shao, Yiyu, Wenfei Peng i Shaoqiang Chen. "Effect of cold treatment process on roundness of bearing ring". Materials Research Express 9, nr 2 (1.02.2022): 026513. http://dx.doi.org/10.1088/2053-1591/ac4e3e.
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Abstract In the heat treatment of the bearing ring, due to the different degree of thermal expansion of the outer surface and inner metal of the bearing ring, and the large thermal stress and tissue stress generated in the ring, resulting in serious deformation of the ring in the diameter direction and increased roundness error. For these problems, the heat treatment test of the bearing ring was carried out, with the cold treatment process added to the heat treatment. The effect of cold treatment on the residual stress, retained austenite and roundness of the bearing ring was analyzed. The research results show that: because the degree of deformation of the bearing ring is affected by the residual stress, the cold treatment process can significantly improve the residual stress on the bearing ring surface and reduce the deformation. The cold treatment process can accelerate the transformation from retained austenite to martensite in the bearing ring, reduce the content of retained austenite, refine the martensite structure and promote the precipitation of network carbide. The cold treatment after quenching also can improve the roundness accuracy of the bear outer ring and the bearing ring raceway, and ensure the processing quality and dimensional stability, which will be a significant benefit in industrial applications.
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Agudo, L., S. Weber, Haroldo Pinto, Enno Arenholz, Juergen Wagner, Heinz Hackl, Jürgen Bruckner i Anke Pyzalla. "Study of Microstructure and Residual Stresses in Dissimilar Al/Steels Welds Produced by Cold Metal Transfer". Materials Science Forum 571-572 (marzec 2008): 347–53. http://dx.doi.org/10.4028/www.scientific.net/msf.571-572.347.
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Recently a new welding technique, the so-called ‘Cold Metal Transfer’ (CMT) technique was introduced, which due to integrated wire feeding leads to lower heat input and higher productivity compared to other gas metal arc (GMA) techniques. Here microstructure formation and residual stress state in dissimilar steel to aluminum CMT welds are investigated. The intermetallic phase seam between the filler and the steel is only a few micrometers thick. Residual stress analyses reveal the formation of the typical residual stress state of a weld without phase transformation. Both in longitudinal and in transversal direction compressive residual stresses exist in the steel plate parent material, tensile residual stresses are present in the heat affected zone of the steel and the aluminum alloy. The area containing tensile residual stresses is larger in the aluminum alloy due to its higher heat conductivity than in the steel. Due to the symmetry in the patented voestalpine welding geometry and the welding from bottom and face side of the weld, the residual stress distributions at the top and at the bottom side of the weld are very similar.
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Peng, Xiaowen, Kexing Song, Yanjun Zhou, Tao Huang, Haitao Liu, Yunxiao Hua, Jingzhao Yang i Guojie Wang. "Influence of P Content on Microstructure and Texture Evolution of the Oxygen-Free Copper". Metals 12, nr 10 (28.09.2022): 1622. http://dx.doi.org/10.3390/met12101622.
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The present work aims to systematically investigate the influence of P content on the microstructure and texture evolution of oxygen-free copper during intermediate annealing and final cold rolling. The microstructure and texture evolution were studied by electron backscattered diffraction and transmission electron microscopy. With the addition of P, the grains refined and a large fraction of low angle grain boundaries (LAGBs) emerged after intermediate annealing. The texture transformed from pure metal type for pure Cu to the α-fiber texture which included brass and Goss texture as P was added. The recrystallization temperature increased with the addition of P, and refined grains after the final cold rolling process. The addition of elemental P would reduce the stacking fault energy, and then influence the transformation of the deformation and recrystallization texture of the copper. Accompanied by the evolution of the deformation texture, the recrystallization cubic texture {001}<100> was suppressed and a strong {236}<385> brass recrystallization texture emerged with the addition of elemental P after the intermediate annealing and subsequent final cold rolling process.
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Gautam, Jai, Roumen H. Petrov, Elke Leunis i Leo Kestens. "Surface Microstructure Evolution during Phase Transformation on Mn, Al and Si Alloyed Ultra Low Carbon Steel". Defect and Diffusion Forum 297-301 (kwiecień 2010): 757–63. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.757.
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This paper investigates the surface texture evolution after a short phase transformation annealing in low vacuum on ultra low carbon steel sheets alloyed with high Mn and Al and the cold rolled steel sheets of industrial composition alloyed with silicon. The ultra low carbon steel sheets with high Mn and Al show surface monolayer which has a characteristic surface texture components <100>//ND texture and microstructure with special grain morphology. Contrastingly, the industrial composition alloyed with silicon does not show specific surface texture components inspired by surface energy anisotropy at the surface. The composition depth profiling investigations performed on the all steel sheet surface shows that oxidation characteristics of alloying elements at the metal vapour interface have played a decisive influence on surface texture evolution. Further, transformation annealing in higher vacuum reveals that surface texture can be obtained in an industrial composition alloyed with silicon.
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Fei, Zhenyu, Zengxi Pan, Dominic Cuiuri, Huijun Li i Azdiar A. Gazder. "A Combination of Keyhole GTAW with a Trapezoidal Interlayer: A New Insight into Armour Steel Welding". Materials 12, nr 21 (31.10.2019): 3571. http://dx.doi.org/10.3390/ma12213571.
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The ballistic performance of armour steel welds using austenitic filler materials is poor on account of the disparity in the mechanical properties of the weld and base metals. Consequently, a novel Keyhole Gas Tungsten Arc Welding process with a trapezoidal AISI309 austenitic stainless steel interlayer was developed to tailor chemical composition and microstructure by controlling the solidification sequence. Results show that the dilution rate in the weld metal region can reach up to 43.5% by placing a specially designed interlayer in between the base metal, providing a major scope for microstructure modification. Detailed weld analysis was undertaken by X-ray diffraction, optical and secondary and transmission electron microscopy, energy dispersive spectroscopy and electron back-scattering diffraction. The results from Vickers hardness indents and Charpy impact toughness testing at −40 °C show that the properties of the weld metal region are comparable to that of the base metal. This is ascribed to the weld metal comprising a two phase microstructure of martensite and retained austenite, which contribute to improvements in strength and toughness, respectively. Furthermore, the tailored chemical composition, microstructure and low temperature phase transformation in the weld metal may reduce the tendency toward both solidification cracking and hydrogen assisted cold cracking.
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Johnson, Nathan S., Donald W. Brown, John S. Carpenter, Behnam Amin-Ahmadi, Craig A. Brice, Branden B. Kappes i Aaron P. Stebner. "The roles of kinematic constraint and diffusion in non-equilibrium solid state phase transformations of Ti-6Al-4V". Applied Physics Letters 120, nr 17 (25.04.2022): 171901. http://dx.doi.org/10.1063/5.0084229.
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A solid state phase transformation of Ti-6Al-4V was studied using high speed in situ x-ray diffraction measurements made during rapid cooling of a cold metal transfer arc weld bead deposited onto a water cooled substrate. Analysis of body centered cubic (BCC) and hexagonal close packed (HCP) lattices revealed an abrupt, nonlinear shift in the lattice parameters of both phases just after the HCP phase had nucleated. Postmortem transmission electron microscopy confirmed that V diffusion was mostly suppressed during cooling. Together, these results indicate that at this cooling rate of approximately 104 K/s, which is representative of cooling rates of many additive manufacturing and welding processes, kinematic coherency of the BCC–HCP interfaces gives rise to the anomalous lattice expansion and contraction behaviors of both phases during the initial nucleation and growth stages of (mostly) martensitic transformation from BCC to HCP; the role of diffusion in such lattice anomalies is shown to be minimal.
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Johnson, Nathan S., Donald W. Brown, John S. Carpenter, Behnam Amin-Ahmadi, Craig A. Brice, Branden B. Kappes i Aaron P. Stebner. "The roles of kinematic constraint and diffusion in non-equilibrium solid state phase transformations of Ti-6Al-4V". Applied Physics Letters 120, nr 17 (25.04.2022): 171901. http://dx.doi.org/10.1063/5.0084229.
Pełny tekst źródłaStreszczenie:
A solid state phase transformation of Ti-6Al-4V was studied using high speed in situ x-ray diffraction measurements made during rapid cooling of a cold metal transfer arc weld bead deposited onto a water cooled substrate. Analysis of body centered cubic (BCC) and hexagonal close packed (HCP) lattices revealed an abrupt, nonlinear shift in the lattice parameters of both phases just after the HCP phase had nucleated. Postmortem transmission electron microscopy confirmed that V diffusion was mostly suppressed during cooling. Together, these results indicate that at this cooling rate of approximately 104 K/s, which is representative of cooling rates of many additive manufacturing and welding processes, kinematic coherency of the BCC–HCP interfaces gives rise to the anomalous lattice expansion and contraction behaviors of both phases during the initial nucleation and growth stages of (mostly) martensitic transformation from BCC to HCP; the role of diffusion in such lattice anomalies is shown to be minimal.
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Wang, Wen-Quan, Shu-Cheng Dong, Fan Jiang i Ming Cao. "Effects of Ar and He on Microstructures and Properties of Laser Welded 800MPa TRIP Steel". MATEC Web of Conferences 142 (2018): 03004. http://dx.doi.org/10.1051/matecconf/201814203004.
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Fiber laser welding of cold rolled TRIP steel (transformation Induced Plasticity steel) sheet with tensile strength of 820MPa and thickness of 1.4mm was carried out using shielding gases Ar and He, respectively. For the same laser power and welding speed, the effects of different shielding gases on penetration and bead section morphologies were investigated. The microstructures and properties of the TRIP steel joints were also studied. The investigation showed that higher penetration and lower porosity could be obtained under shielding gas He using the same laser power and welding speed. The microstructures of the TRIP joint mainly included martensite and retained austenite. But the joint microhardness and tensile strength were higher under the shielding gas He. The tensile strength of the welded joint perpendicular to the weld line was equal to that of the base metal. But the tensile strength of the joint parallel with the weld line was higher than that of the base metal. The plasticity and formability of the welded joint were impaired due to the formation of martensite in the weld metal.
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Triani, Rafael Magalhães, José Benedito Tosoni Decarlis Rodrigues Neto, Pedro Gabriel Bonella De Oliveira, Galtiere Corrêa Rêgo, Amadeu Lombardi Neto i Luiz Carlos Casteletti. "In-Situ Production of Metal Matrix Composites Layers by TIG Surface Alloying to Improve Wear Resistance of Ductile Cast Iron Using a Buffer-Layer and Post Weld Heat Treatment". Coatings 13, nr 7 (22.06.2023): 1137. http://dx.doi.org/10.3390/coatings13071137.
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A TIG surface alloying process was applied to modify the surface of ductile cast iron samples. Using this process, in-situ metal matrix composite (MMC) layers were produced on samples to improve their wear resistance. These layers were made by melting substrates and powders as additional material into this melt pool. The efficiency of preheating of the samples to prevent cold cracks during solidification was verified. Moreover, a buffer layer produced in situ to decrease the mismatches between the chemical and physical properties of the materials was also tested. Post-weld heat treatment (PWHT) was used to increase the tribological characteristics of the layers and eliminate adverse effects of the heat-affected zone (HAZ) created by the fusion of the substrate surface. The results showed that, in the samples without preheating, the formation of cold cracks occurred. Additionally, layers produced without a buffer layer showed defects, such as shrinkage and porosity. However, using both preheating and a buffer layer prevented cold cracks, discontinuities, shrinkage, and porosity defects in the layers. Furthermore, PWHT allowed for the transformation of brittle martensite into tempered martensite at the HAZ. MMC layers presented high hardness of up to 1230 HV and wear resistance up to 5.8 times greater compared to the substrate samples without layers.
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Meseguer-Valdenebro, José, Antonio Portoles i Eusebio Martínez-Conesa. "Analytical determination and validation by finite elements method of hydrogen weld of carbon steel after post-heating". Thermal Science, nr 00 (2020): 297. http://dx.doi.org/10.2298/tsci200517297m.
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The objective of this work is to determine analytically the amount of hydrogen residual in a weld after having carried out post-heating for a certain period of time in order to reduce the risk of cold cracking due to the presence of hydrogen in the weld and its validation by the finite element method. Post-heating is a variable present in the welding procedures and therefore it is mandatory in those welds that require it. This work can be helpful to determine both numerically by the finite element method and analytically the post-heating suitable in a welding process depending on that process, the welded material and the base material. In this work, the phase transformation and time difference of the phase transformation between the weld metal and base metal are not considered. The diffusivity values are those used by the reference method that analytically calculates the residual hydrogen in a carbon steel weld. There are two values of hydrogen diffusivity (minimum value and maximum value) in this way the diffusivity values that represent all types of carbon steel are collected. The least amount of hydrogen in the weld is with a post-heating to 200?C, producing a decrease in hydrogen in the weld at a higher speed than with the rest of temperatures below this.
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Gautam, Jai, Roumen H. Petrov i Leo Kestens. "Surface Texture Evolution during α-γ-α Transformation in Mn and Al Alloyed Ultra-Low Carbon Steel". Materials Science Forum 550 (lipiec 2007): 503–8. http://dx.doi.org/10.4028/www.scientific.net/msf.550.503.
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This paper investigates the surface texture evolution during α−γ−α phase transformation. After austenite annealing of the cold rolled sheets a weak texture was formed at the surface of ultra low carbon steel alloyed with Mn and Al. This texture consists of <100>//ND and <110>//ND fiber orientations with an intensity of approximately 2 X random. This surface texture is confined to a mono-layer of surface grains which are in direct contact with the metal/vapour interface. In order to interpret this surface effect, two alternative mechanisms were considered: (i) one assumption attributes the occurrence of the specific surface texture to the minimization of the outer surface energy and (ii) according to an alternative hypothesis the release of elastic work parallel to ND in the surface area is responsible for the observed surface fibers. After analyzing the experimental data it is concluded that the evidence in support of hypothesis (i) is the more convincing in this experiment.
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Peng, Chih Wei, i Jui Ming Yeh. "Preparation and Corrosion Protection Effect of Electroactive Polyurethane Containing Amino-Capped Aniline Trimer". Advanced Materials Research 123-125 (sierpień 2010): 1255–58. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.1255.
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Electroactive polyurethane (EPU) containing conjugated segments of electroactive amino-capped aniline trimer (ACAT) has been successfully synthesized and characterized through Fourier-Transformation infrared and UV–visible absorption spectroscopy. Subsequently, electroactivity (i.e., redox capability) of as-prepared EPU was investigated by electrochemical cyclic voltammetry (CV) studies. It was noticed that the as-prepared EPU exhibited reversible redox capability was found to reveal better corrosion protection effect on cold-rolled steel (CRS) electrodes than that of non-electroactive polyurethane based on a series of electrochemical measurements such as corrosion potential, polarization resistance, corrosion current and electrochemical impedance spectroscopy (EIS) studies in 5 wt-% NaCl electrolyte. This significant enhancement of corrosion protection on CRS electrodes as compared to non-electroactive polyurethane might be probably ascribed to the redox catalytic property of as-prepared EPU coatings inducing the formation of passive layer of metal oxide, as evidenced by the SEM and ESCA studies.
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Kobasko, Nikolai. "COOLING INTENSITY OF INVERSE SOLUBILITY POLYALKYLENE GLYKOL POLYMERS AND SOME RESULTS OF INVESTIGATIONS FOCUSED ON MINIMIZING DISTORTION OF METAL COMPONENTS". EUREKA: Physics and Engineering 2 (31.03.2017): 55–62. http://dx.doi.org/10.21303/2461-4262.2017.00294.
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Poly(Alkylene Glycol) polymers of inverse solubility (PAG) provide ideal uniform cooling for minimizing distortion and preventing crack formation during hardening machine components and tools. However, in spite of ideal cooling, from time to time, a big distortion takes place during hardening process. A reason for a big distortion development during hardening in PAG solutions is explained and an idea how to fix the problem is suggested. It is shown that at the end of cooling coating can be locally dissolved by a cold water flow creating local open area where martensite transformation starts first. Due to greater specific volume of martensite, it creates a big distortion. To solve the problem, one should interrupt cooling process or stop agitation before insulating coating is dissolved. To perform correctly proposed technology, cooling intensity of inverse solubility PAG polymers of 1–20 % were investigated on the basis of use of regular thermal condition theory. As a result, dimensionless effective numbers Kn were obtained for recipes development. A technique for solving the problem is proposed by author. Examples of calculations are provided.
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Sacco, Alessandro, Anna Martina Battaglia, Cirino Botta, Ilenia Aversa, Serafina Mancuso, Francesco Costanzo i Flavia Biamonte. "Iron Metabolism in the Tumor Microenvironment—Implications for Anti-Cancer Immune Response". Cells 10, nr 2 (2.02.2021): 303. http://dx.doi.org/10.3390/cells10020303.
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New insights into the field of iron metabolism within the tumor microenvironment have been uncovered in recent years. Iron promotes the production of reactive oxygen species, which may either trigger ferroptosis cell death or contribute to malignant transformation. Once transformed, cancer cells divert tumor-infiltrating immune cells to satisfy their iron demand, thus affecting the tumor immunosurveillance. In this review, we highlight how the bioavailability of this metal shapes complex metabolic pathways within the tumor microenvironment and how this affects both tumor-associated macrophages and tumor-infiltrating lymphocytes functions. Furthermore, we discuss the potentials as well as the current clinical controversies surrounding the use of iron metabolism as a target for new anticancer treatments in two opposed conditions: (i) the “hot” tumors, which are usually enriched in immune cells infiltration and are extremely rich in iron availability within the microenvironment, and (ii) the “cold” tumors, which are often very poor in immune cells, mainly due to immune exclusion.
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Xie, Lin, Chunpeng Wang, Yuhui Wang, Guilin Wu i Xiaoxu Huang. "Grain Size Effect on the Mechanical Behavior of Metastable Fe-23Cr-8.5Ni Alloy". Metals 9, nr 7 (29.06.2019): 734. http://dx.doi.org/10.3390/met9070734.
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An Fe-23Cr-8.5Ni alloy was used as a model material to study the grain size effect on the mechanical behavior of metastable duplex metal. Alloy samples with different grain sizes ranging from 0.1 to 2 μm were prepared by cold-rolling and annealing. A structural refinement to about 0.1 μm results in a high yield strength but very limited ductility. A significant improvement of ductility occurred at the grain size of about 0.4 μm. A further increase in grain size results in a decreased strength and a slightly improved ductility. The alloy with a grain size of about 0.4 μm exhibits an excellent combination of strength and ductility, where the yield strength and tensile elongation are increased up to 738 MPa and 29% as compared to 320 MPa and 33% of a coarse-grained (about 2 μm) sample, respectively. The origin of the excellent mechanical properties was attributed to the unique deformation characteristics associated with the transformation induced plasticity and the development of back stress.
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Kwiecień, M., P. Graca, K. Muszka i J. Majta. "Selected Problems of the Microstructure Evolution During Microalloyed Steel Wire Rod Production Process". Archives of Metallurgy and Materials 62, nr 2 (1.06.2017): 899–904. http://dx.doi.org/10.1515/amm-2017-0132.
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Abstract In the present study, we have discussed the selected problems of microstructure development during the whole manufacturing process, i.e. continuous casting, thermomechanical processing, and cold metal forming of the microalloyed steels wires. In the investigated steels, the microstructure development was controlled by the history of deformation and by the effects of microalloying elements, mostly Nb, Ti, and B. It has been concluded that obtained in the ultrafine grained microalloyed steel wires mechanical properties were first of all resulting from specific structural composition and grain refinement. Additionally, it has been proven that austenite grain refinement, that increases nucleation rate during the austenite-to-ferrite phase transformation, as a result of the thermomechanical processing, are very beneficial from point of view of the final mechanical properties. This problem starts to be very important when the microalloyed steel products are subjected to severe plastic deformation, as it has been shown discussed in the present work for combined processes of wire drawing and wire flattening.
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Kuluev, Bulat R., Zoya A. Berezhneva, Elena V. Mikhaylova, Bogdan N. Postrigan i Aleksey V. Knyazev. "Productivity and stress-tolerance of transgenic tobacco plants with constitutive expression of rapeseed glutathione synthetase gene BnGSH". Ecological genetics 15, nr 1 (15.03.2017): 12. http://dx.doi.org/10.17816/ecogen15112-19.
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Glutathione is the most important part of plant antioxidant defense system. Biosynthesis of glutathione in the cells is performed by two enzymes: glutamylcysteine ligase and glutathione synthetase, the latter catalyzing the attachment of glycine to a dipeptide glutamylcysteine. In literature there is information on the improvement of heavy metal-tolerance of transgenic plants due to the increase in the expression level of glutathione synthetase genes. However there is not enough data on the tolerance of these plants to other types of abiotic stress. Therefore the aim of our research was to make transgenic tobacco plants with constitutive expression of rapeseed glutathione synthetase gene BnGSH and to estimate their growth parameters in normal conditions and under salt, drough and cold stress. Using agrobacterial transformation method, we generated 17 lines of transgenic plants containing rapeseed BnGSH gene under control of 35S promoter. The presence of transgenes was confirmed by PCR method and histochemical analysis of the activity of GUS reporter gene. 12 lines with the highest expression of BnGSH gene were chosen on the basis of the results of RT-PCR. We performed morphological analysis, including measurements of stem hight, leaf area, flower length, fresh and dry weight of shoots and root length. Some transgenic plants demonstrated increased productivity in normal conditions as well as under NaCl stress. However, no change in drought and cold tolerance was observed in transgenic plants.
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Votava, Filip, Hana Jirková, Ludmila Kučerová i Štěpán Jeníček. "Study of Transition Areas in Press-Hardened Steels in a Combined Tool for Hot and Cold Forming". Materials 16, nr 1 (3.01.2023): 442. http://dx.doi.org/10.3390/ma16010442.
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Press-hardening, also known as hot stamping, is a manufacturing process for producing car body parts that must meet the high demands of their mechanical properties and safety parameters. Moreover, these components often require different mechanical properties in different parts of the component. This work presents the press-hardening process in a special combined tool where one half of the tool is heated and the other half is cooled. The cooled part has been 3D printed due to the complexity of the internal cooling channels. The aim of this work is to investigate the variation of the microstructures in the sheet metal and the mechanical properties in relation to the cooling process in the tool and to determine the transition area where these properties cross over. Two steels were chosen for the experiment. The most commonly used steel 22MnB5, and an experimental high-strength steel with 0.2% C alloyed with manganese and aluminium. A temperature of 425 °C was set in the heated part of the tool, and different holding times in the tool were tested. In the heated part of the tool, a bainitic structure with a fraction of ferrite and retained austenite was formed, while in the quenched part of the tool, a martensitic transformation was promoted due to rapid cooling. In addition to microscopic analyses, mechanical tests and hardness measurements were also performed.
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Mazur, V. L., V. I. Tymoshenko i I. Yu Prykhodko. "Implementation of calculation methods in a specialized computer system of the stress-deformation and temperature state of steel bar coils". Fundamental and applied problems of ferrous metallurgy 36 (2022): 240–53. http://dx.doi.org/10.52150/2522-9117-2022-36-240-253.
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The theory of formation and transformation of the stress-deformation and temperature state of rolls of hot-rolled and cold-rolled steel bars during their winding-unwinding in the processes of rolling, heat treatment, training, transportation, storage, and performance of other production operations at metallurgical plants has been developed. Mathematical models, algorithms and a computer system implementing them are proposed. A description of the possibilities of using this system when solving various tasks is given. In the computer system, an approach to assessing the influence of the parameters of the process of cold rolling and winding the stock into rolls, the temperature and speed regimes of their heating and cooling during annealing in hood furnaces is considered. For the first time, the methodology for identifying patterns of influence of inter-turn gaps in rolls on their stress-strain state was disclosed. The procedure for detecting the effects of cold rolling speed, temperature, tension of the rods rolled and wound into rolls, and their surface roughness on the stress-strain state of the rolls is shown. In detail, the implementation of new ideologies and approaches to solving the problem of determining the stress-strain state (STS) of rolls is shown in the computer system. Models and algorithms for calculating VAT, which are the basis of the computer system, are developed on the basis of classic solutions in the field of materials science, theories of elasticity, metal pressure treatment, heat engineering, gas dynamics, numerical methods and other fields of knowledge. The computer system revealed the mechanisms of forming the temperature and stress-strain state of rolls of steel bars in the processes of rolling, heating, isothermal aging and cooling during annealing in hood furnaces; the influence of the temperature and speed regimes of rolling and annealing on the occurrence of critical inter-turn pressures in the rolls, which lead to surface defects of the "bend line" (breaks) and defects in the shape of the rolls, is taken into account. The possibilities of influencing the VAT of rolls during rolling by adjusting the tension of the staffs, and during annealing by adjusting the duration of isothermal exposure and the rate of subsequent cooling of the rolls, are revealed. References to literary sources are provided, which detail the results of research on scientific and technical problems implemented in the computer system. In the computer system, methods of winding cold-rolled bars into rolls are used, which exclude the loss of their stability and the formation of "bends", subsidence, "bird" defects during the production of thin sheet steel in industrial conditions. Recommendations are given regarding the choice of a rational technology for the roll production of hot-rolled and cold-rolled sheet metal. The developed solutions are implemented in the "CoilTemper3D" computer system and are used in production.
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Thuong, Nguyen Van, Zuhailawati Hussain, Anasyida Abu Seman i T. D. Huy. "Preparation of Globular Microstructure Aluminum Alloy Using Cooling Slope Casting as Feed Material for Equal Channel Pressing Process". Advanced Materials Research 1024 (sierpień 2014): 247–50. http://dx.doi.org/10.4028/www.scientific.net/amr.1024.247.
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Equal channel angular pressing (ECAP) could be used to achieve ultra fine grains in bulk aluminum alloy through severe plastic deformation. Typically a feed material of as-cast aluminum alloys is used with a typical hypoeutectic solidification structure, consisting of primary aluminum dendrites and interdendritic network of lamellar eutectic silicon. On the other hand, semi-solid metal casting provides non-dendritic and globular microstructure which is one of a considerable factor in obtaining homogenous microstructure after ECAP. This work is an attempt to produce aluminum alloy with globular microstructure using cooling slope semi-solid casting process which is believed suitable as a feedstock for ECAP. The aim of this work described in this paper was to understand of microstructural evolution of aluminum structure during cooling slope casting process. Two experiments were carried out. A sample was casted via a cooling slope into a vertical cold mild steel mould at pouring temperature of 640°C. Cooling slope length of 250 mm, slope temperature of room temperature and tilt angle of 60owas applied. Another sample was casted directly into a vertical cold mild steel mould at pouring temperature of 640°C. The primary α-Al phases in the sample that casted without cooling slope was mostly in dendritic throughout the section of sample whilst the primary α-Al phases transformed completely into non-dendritic in the sample that was casted via the cooling slope. Therefore, the transformation is believed resulted from the effect of cooling slope
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Wang, Zhenbiao, Shuai Wang, Lingling Ren, Chengde Li, Wei Wang, Zhu Ming i Yuchun Zhai. "Effect of the Deposition Process on High-Temperature Microstructure and Properties of the Direct Energy Deposition Al-Cu Alloy". Metals 13, nr 4 (14.04.2023): 765. http://dx.doi.org/10.3390/met13040765.
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The excellent microstructure and mechanical properties of Al-Cu alloy deposited using the Direct Energy Deposition (DED) process has been shown in previous studies, which is the most likely aluminum alloy material to meet the load-bearing requirements of hypersonic aircraft. However, its high-temperature performance and the law of microstructure transformation during the high-temperature process still need to be determined. In this paper, DED Al-Cu alloy samples were prepared using the Cold Metal Transfer (CMT) process, CMT Pulse process, and CMT Pulse Advanced process. The effect of different deposition processes on the microstructure and mechanical properties of the deposits was investigated at 200 °C for 30 min. The results show that the Al-Cu alloy’s main strengthening phase θ′ is excessively transformed into the equilibrium θ phase after the high-temperature process, which is the main reason for the degradation in the DED Al-Cu alloy’s properties at high temperatures. Different deposition processes have almost no effect on the high-temperature performance of the DED Al-Cu alloy, and the deposition process can be selected according to the product’s structure.
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Becher, Marcin, Mirosław Kobierski, Krzysztof Pakuła i Dawid Jaremko. "Distribution of Mercury in Drained Peatlands as the Effect of Secondary Transformation of Soil Organic Matter". Agriculture 13, nr 5 (30.04.2023): 995. http://dx.doi.org/10.3390/agriculture13050995.
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Peat organic soils play a major role in the accumulation of soil organic matter (SOM) and the mercury (Hg) cycle. Large mercury resources in peatlands can be a source of methylmercury for many decades and centuries, even if deposition is significantly reduced. The organic matter of peatland soils drained for agricultural use is subject to secondary transformation, which may affect the accumulation and resources of mercury. The aim of our work is to assess the secondary transformation of organic matter in the soils of drained peatlands of the temperate climate zone and to examine whether it affects mercury resources and profile distribution in organic soils. Field research was conducted in peatlands located in eastern Poland. In the present study, evaluation of secondary transformations occurring after drainage was based on observations of soil morphological characteristics, physical and chemical properties as well as fractional composition of organic matter of the identified soil horizons (to depth 70 cm). Standard cold vapor atomic absorption spectrometry (CV-AAS) was used to measure the total mercury content. In our research, we found a significant effect of the secondary transformation of organic matter occurring in drained peatlands of the temperate climate zone on the total mercury content and stock in soils. The highest content and differentiation of mercury occurred in murshic horizons (up to a maximum depth of 43 cm). The average mercury content of the distinguished soil horizons is grouped in the following series (in μg kg−1): M1 (212.0) > M2 (182.8) > M3 (126.3) > Pt (84.9). The mercury stock, up to a depth of 70 cm in the tested soils, ranged from 17.5 to 39.6 mg m−2. As much as 82.2% of soil mercury was found in the upper murshic horizons. We found strong correlations between soil properties characteristically variable in the secondary transformation process and total mercury content. The increased content of humic substances in murshic horizons caused a significant increase in the total mercury content. Our research is of great importance for soil monitoring, as the amount of determined mercury was greatly influenced by the depth of sampling (up to 25 cm). The results of the research should be taken into account when planning the restoration of peatlands of the temperate climate zone. There is a potential risk that elevated mercury concentrations in the upper murshic horizons may be a source of methylmercury for a long period of time. In peat soils with a high concentration of mercury, the risk of contamination with this toxic metal should be determined before re-irrigation.
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Kumar, Amit, Mangey Ram i Rohit Singh Rawat. "Optimization of casting process through reliability approach". International Journal of Quality & Reliability Management 34, nr 6 (5.06.2017): 833–48. http://dx.doi.org/10.1108/ijqrm-07-2016-0103.
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Purpose The quality of production is an essential factor for the performance measure of a system; a casting process is the same section. It is a type of metal-forming practice in which the required shape of metal is acquired by pouring molten metal into the mold cavity and allowing it to solidify. Casting is done to provide strength and rigidity to the parts of a system for bearing mechanical impacts. The purpose of this paper is to investigate the various aspects which affect the casting process in the foundry industry, in order to optimize the quality of casting, with the assumption that sufficient repair facility is always available. Design/methodology/approach The considered casting system can have many defects such as the mold shift defect, blowhole defect, defect of shrinkage and porosity, defect of inclusion, defect of cold shut and much more. The studied system can be in three states during the process, namely, good state, failed state and degraded state. The system can repair after minor failures as well as a major failure. The average failure rates of various defects of the system considered as constant and repairs follow the general time distribution. The system is analyzed with the help of the supplementary variable technique and the Laplace transformation for evaluating its various performance measures in order to improve its performance/production. Findings This work provides a strong understanding of the casting industry, that which failure affects the production of casting and how much. For better understanding, the results have been demonstrated with the help of graphs. Originality/value In the present paper, a mathematical model based on the casting process in manufacturing industry has been developed.
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Widyastuti, Budi P. Febrian i Sutarsis. "Hydrogen Absorpsivity-Desorbsivity of Mg Doped by Ni, Cu, Al Produced by Mechanical Alloying". Advanced Materials Research 789 (wrzesień 2013): 37–41. http://dx.doi.org/10.4028/www.scientific.net/amr.789.37.
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Mg, in the form of MgH2,is one kinds of materials widely used as hydrogen storage materials. Absorption and desorption properties of hydrogen which comes from metal hydride depend on materials itself, addition of elements, as well as manufacturing method. In this research, Mg as hydrogen storage were prepared by mechanical alloying with Ni, Cu, and Al as element addition and variation milling time for 10, 20 and 30 hours. Some morphological analyses (XRD, SEM) were done to observe phase transformation. Absorption and desorption properties characterization were employed by DSC and hydrogenation tests. The improvement in milling time decreased particle size, therefore enhanced wt% of absorbed hydrogen and decrease onset desorption temperature. However, the excessive of agglomeration and cold welding on mechanical alloying process resulted in bigger particle size. Alloying elements, Al and Cu, served as catalyst, while Ni acted as alloying which reacted with hydrogen. Mg10wt%Al with 20 hours milling time at hydrogenation temperature 250°C, 3 atm pressure, and 1 hour holding time resulted in the highest weight percent of H2(0.38%wt). However, Mg10wt%Al with 30 hours milling time had the lowest onset temperature, 341.49°C
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Chen, Yi-Cheng, i Shih-Fu Ou. "Effects of Reinforcement Ratios and Sintering Temperatures on the Mechanical Properties of Titanium Nitride/Nickel Composites". Materials 13, nr 20 (9.10.2020): 4473. http://dx.doi.org/10.3390/ma13204473.
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In this study, powder metallurgy was used to fabricate titanium nitride/nickel metal-matrix composites. First, titanium and nickel powders with weight ratios of 20:80, 50:50 and 80:20 were dry mixed for 24 h. After cold isostatic pressing, the green compacts were soaked in a water-based hot forging lubricant and sintered at 850, 950 and 1050 °C for 1.5 h in an air atmosphere. The effects of the amounts of titanium powder and the sintering temperatures on the mechanical properties (hardness, wear resistance and compressive strength) of the composites were investigated. The results indicated that titanium gradually transformed into titanium nitride near the surface after sintering due to the carbothermal reduction reaction; this transformation was observed to significantly increase the hardness. In addition, an oxygen-rich film was observed to form between the titanium nitride particles and the nickel matrix. An optimum sintering temperature of 950 °C provides the composites (titanium–nickel weight ratios of 20:80) the best mechanical properties (wear resistance and compressive strength) among other groups. Furthermore, increasing the titanium content to 80% in the composite increased the hardness; however, the wear resistance and compressive strength decreased.
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Matsuda, Fukuhisa, Hiroji Nakagawa, Kenji Shinozaki i Yasuhiro Nishio. "Cold cracking susceptibility in weld metal of HY-steel. Part 5. Relaxation phenomenon of the restraint stress due to transformation expansion in weld zone of HY-steel." QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY 5, nr 2 (1987): 250–55. http://dx.doi.org/10.2207/qjjws.5.250.
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Okhay, Olena, i Alexander Tkach. "Impact of Graphene or Reduced Graphene Oxide on Performance of Thermoelectric Composites". C 7, nr 2 (21.04.2021): 37. http://dx.doi.org/10.3390/c7020037.
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In recent years, worldwide research has been focused on clean and sustainable energy sources that can respond to the exponentially rising energy demands of humankind. The harvesting of unused heat in relation to automotive exhaustion, industrial processes, and home heating is one possible way of enabling the transformation from a fossil fuel-based society to a low-carbon socioeconomic epoch. Thermoelectric (TE) generators can convert heat to electrical energy thanks to high-performance TE materials that work via Seebeck effects when electricity appears between the cold part and the hot part of these materials. High figure of merit (ZT) TE material is characterized by high electrical conductivity and Seebeck coefficient, together with low thermal conductivity. This article aims to summarize ZT values reported for chalcogenides, skutterudites, and metal oxides with graphene (G) or reduced graphene oxide (rGO), and intends to understand the relationship between the addition of G-rGO to composites and ZT variation. In a majority of the publications, ZT value increases with the addition of G/rGO, although the relative growth of ZT varies for different material families, as well as inside the same group of materials, with it often being related not to a G/rGO amount but with the quality of the composite.
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Yvell, Karin, Michael Lindgren i Ulf Bexell. "A Microstructural Investigation of Roll Formed Austenitic Stainless Steel". Key Engineering Materials 549 (kwiecień 2013): 364–71. http://dx.doi.org/10.4028/www.scientific.net/kem.549.364.
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Due to high production rates and the possibility to form complex geometries roll forming has become an increasingly popular forming process for sheet metal. Increasing quantities of high strength steels are used today but can be difficult to form due to their low ductility. One way to partly overcome this problem is to heat the steel in the forming area thus locally increasing the ductility. In the present study partially heated cold rolled high strength AISI 301 type austenitic stainless steel was investigated using electron backscattered diffraction (EBSD), and the results were compared to microhardness measurements. The results show that partial heating will give an almost complete reverse martensite transformation, i.e. martensite (α ́) transforms to austenite (γ), close to the surfaces and grain growth in the middle of the steel sheet. The extension of the heat affected zone can be determined using either microhardness or EBSD measurements. Both these measurements can be used to determine the position of the neutral layer after roll forming. The hardness measurement cannot distinguish between microstructural features but the results are in good agreement with the EBSD results for volume fraction of α ́-martensite. A major advantage of using EBSD is the possibility to characterize and follow the microstructural development when heating and roll forming.
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Gremyachikh, V. A., D. A. Kvasov i E. S. Ivanova. "Patterns of mercury accumulation in the organs of bank vole Myodes glareolus (Rodentia, Cricetidae)". Biosystems Diversity 27, nr 4 (9.11.2019): 329–33. http://dx.doi.org/10.15421/011943.
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Mercury (Hg) and its compounds are among the most hazardous environmental pollutants with a high cumulative potential and they can have toxic effects on human and animal health even in low concentrations. Due to the increasing rate of human economic activity and the increase in the amount of Hg in the total cycling of matter, the study of its distribution, transformation, redistribution and accumulation in the abiotic and biotic components of various ecosystems remains important up to the present time. We assessed the content of metal in organs and tissues of the bank vole Myodes (Clethrionomys) glareolus Schreber, 1780 (Rodentia, Cricetidae), a widespread small rodent, caught in different biotopes of forest-steppe and steppe zones of Voronezh region. Measurements of Hg in samples were carried out with a mercury analyzer RA-915+ with the accessory PYRO (Lumex) using the atomic absorption method of cold steam without preliminary sample preparation (the lower limit of mercury detection in samples was 0.001 mg/kg). The sample size was 344 specimens. Mean Hg concentrations ranged from values below the analytical determination threshold to 0.887 mg/kg dry weight in the kidneys, 0.411 in the liver, 0.031 in the muscle tissue, and 0.040 in the brain. A positive correlation was found between the metal content in all possible pairs of organs (except for the “muscle – brain” pair) and a weak negative correlation was found between the Hg level and the mass of the animals. Hg concentrations in the studied organs did not differ between males and females. The metal content in the liver and kidneys of voles from the forest-steppe zone was significantly higher than in those from the steppe zone. Among all studied biotopes (meadow, pine and mixed forest, shrub thickets), the lowest concentrations were observed in animals living in pine forests, while the highest one – in more humidified bush thickets. During the vegetation season, there was a decrease in the average values of animal body mass in the samples and an increase in the content of Hg in the liver and kidneys. The results of the study are relevant in the assessment of atmospheric mercury pollution of terrestrial ecosystems using small mammals, such as Myodes glareolus, as a model object.
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Matrosov, M. Yu, P. G. Martynov, A. V. Mitrofanov, K. Yu Barabash, T. V. Goroshko i M. I. Zvereva. "Study of the thermal treatment modes influence on the forming of microstructure and specified complex of mechanical properties of high-strength sheet product with guaranteed level of hardness (400–450 HB) of low-alloyed steel". Ferrous Metallurgy. Bulletin of Scientific , Technical and Economic Information 75, nr 4 (18.05.2019): 480–87. http://dx.doi.org/10.32339/0135-5910-2019-4-480-487.
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High-strength sheet product of low-alloyed steel, used at manufacturing of heavy-loaded structures, must have, apart from wear resistance, high toughness, good weldability, ability to hot and cold forming, machinability and low cost. Combination of these properties based on forming fine grain austenite structure before the martensitic transformation at definite its thermal treatment modes. Results of study of microstructure, fine structure and mechanical properties of high-strength boron-containing low-alloyed steel after different technological methods of the rolled product manufacturing presented: high-temperature hot rolling and twostages controlled rolling with accelerated cooling followed by thermal treatment – quenching with tempering. Variants of optimal modes of thermal treatment determined, providing combination of high level of impact toughness under negative temperatures, hardness and strength properties of sheet product. The two considered in the article technological variants, comprising treatment of low-alloyed steel with boron (hot rolling and two-stages controlled rolling with accelerated cooling) followed by thermal treatment results in forming fine structure of tempered martensite, which provides high mechanical properties, meeting the made requirements. Depending on the heating temperature before quenching in the range 770–950 °С, the morphology of the actual steel grain is changing from elongated to equiaxed, which is connected with the metal recrystallization process during heating after plastic deformation. The study results obtained allow to optimize the thermal treatment processes of sheet product of low-alloyed boron containing steel for particular conditions of application.
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Martínez-Munuera, Juan Carlos, Javier A. Giménez-Mañogil, Roberto Matarrese, Lidia Castoldi i Avelina García-García. "NOx Reduction Pathways during LNT Operation over Ceria Containing Catalysts: Effect of Copper Presence and Barium Content". Applied Sciences 11, nr 12 (19.06.2021): 5700. http://dx.doi.org/10.3390/app11125700.
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Ceria-based catalysts, with Cu in substitution of noble metals, were studied in a vertical microreactor system under isothermal conditions, where NOx was previously stored, followed by the reduction step conducted under H2. The possible remaining ad-NOx species after the reduction stage, were investigated by Temperature Programmed Desorption in He. In situ DRIFTS was used as a complementary technique for the analysis of the surface species formation/transformation on the catalysts’ surface. Catalysts containing both Ba and Cu were found to be selective in the NOx reduction, producing N2 and minor amounts of NH3 during the reduction step, as well as NO. The different ceria-based formulations (containing copper and/or barium) were prepared and tested at two different temperatures in the NOx reduction (NSR) processes. Their catalytic activities were analyzed in terms of their compositions and have been useful in the elucidation of the possible origin and relevant pathways for NOx reduction product formation, which seems to involve the oxygen vacancies of the ceria-based materials (whose generation seems to be promoted by copper) during the rich step. The scope of this work involves an interdisciplinary study of the impact that catalysts’ formulations (noble metal-free) have on their LNT performance under simulated conditions, thus covering aspects of Materials Science and Chemical Engineering in a highly applied context, related to the development of control strategies for hybrid powertrains and/or the reduction of the impact of cold-start emissions.
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Zhang, Yuanbo, Bei Zhang, Bingbing Liu, Junjie Huang, Jing Ye i Yuelong Li. "Physicochemical Aspects of Oxidative Consolidation Behavior of Manganese Ore Powders with Various Mn/Fe Mass Ratios for Pellet Preparation". Materials 15, nr 5 (25.02.2022): 1722. http://dx.doi.org/10.3390/ma15051722.
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With the depletion of rich manganese ore resources, plentiful manganese ore powders with various Mn/Fe mass ratios are produced. The physicochemical aspects of oxidative consolidation behavior of manganese ores with various Mn/Fe mass ratios were investigated in this work to determine whether manganese ore powders with high iron content (Fe-Mn ore) can be prepared as high-quality pellets. Physicochemical properties of the pellets were investigated, including cold compression strength (CCS), phase transformation, microstructural evolution, Vickers hardness (HV), porosity, and lattice parameter. CCS testing indicated that the strength of roasted Fe-Mn ore pellets was observably lower than that of pure hematite or manganese ore pellets. Phase and morphology results showed that in Fe-Mn ore pellets, an Mn ferrite phase was generated between hematite and pyrolusite particles. However, newborn Mn ferrites and hematite had an obvious crystal boundary in the crystallographic particles. Moreover, poorly crystallized Mn ferrite particles were evident, along with Mn and Fe element concentration gradients, due to the inadequate diffusion of metal ions. This resulted in poor mechanical properties of the Fe-Mn ore pellets. A temperature over 1275 ∘C and a roasting time of 15 min is required for the oxidative consolidation of Fe-Mn ores. In such optimized cases, Mn, Fe, O, and Al elements were uniformly distributed in the well-crystallized Mn ferrite grains, which provided favorable mineralogy for the consolidation of Fe-Mn ore powders.
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Sivak, Roman, Anatoliy Ostrovsky i Roman Zalizniak. "DETERMINATION OF KINEMATIC CHARACTERISTICS OF METAL PLASTIC FLOW UNDER CONDITIONS OF AXIAL SYMMETRY OF THE DEFORMATION PROCESS". Vibrations in engineering and technology, nr 1(104) (29.04.2022): 92–97. http://dx.doi.org/10.37128/2306-8744-2022-1-11.
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With axisymmetric deformation, the deformable body and the load have a common axis of symmetry. Such deformation occurs in numerous technological operations. About 70% of parts obtained by cold extrusion are deformed under conditions of axial symmetry. The plane problem of the theory of plasticity is reduced to a solution in the framework of a two-dimensional statement, when the motion of points in the section of a workpiece is analyzed. Each point can move only in the section plane, and its velocity can be decomposed into two mutually perpendicular directions along the coordinate axes. For plane deformation, it is assumed that the velocity in the direction of the third coordinate axis is equal to zero. The presence of axial symmetry allows us to confine ourselves to studying the behavior of points located on the plane of the meridional section of the workpiece. In this case, each point can move only in the section plane and its velocity can be decomposed into two orthogonal directions: along the axis and along the radius. The component of the velocity vector in the circumferential direction is equal to zero, so only four of the six independent components of the strain rate tensor remain. In this regard, axisymmetric problems of the theory of plasticity are of considerable interest from the point of view of solving applied problems. The article discusses the possibility of using mixed Euler and Lagrange coordinates to determine the components of the strain rate tensor in plastic deformation processes characterized by the axisymmetric nature of metal plastic flow. The vector field of displacements at each point in space reflects the transformation of the initial (non-deformed) configuration into the current one, and therefore determines the configuration of the deformed body in space in a certain frame of reference. The deformation process is first considered in a single Cartesian coordinate system, and then in a cylindrical coordinate system, the use of which is more appropriate for axisymmetric deformation. It is assumed that the functions of the Euler coordinates from the Lagrange coordinates are obtained by approximating the experimental data.
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Yang, Jianguo, Guohao Liu i Wenjian Zheng. "Study on Hydrogen Diffusion Behavior during Welding of Heavy Plate". Materials 13, nr 17 (3.09.2020): 3887. http://dx.doi.org/10.3390/ma13173887.
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For the multi-layer and multi-pass welding process of the heavy plate, the hydrogen diffusion behavior was numerically simulated to study the effect of solid-state phase transition (SSPT) on the hydrogen diffusion in the thickness direction, and the influence of the residual stress-induced diffusion after SSPT. The calculation results were compared with the experimental results. The comparison shows that the distribution of hydrogen concentration in the direction of thickness was in good agreement. The position with the most severe cold cracking sensitivity was located at a 20–30 mm depth from the top surface in this article. After welding, the hydrogen concentration in this position was kept at a high level for a long time under the effect of the size-constraint effect of the heavy plate and the existence of welding residual stress gradient. In addition, the SSPT reduced the residual stress level of weld metal (WM) significantly, increased that of the heat affected zone (HAZ), and the hydrogen was redistributed under the influence of stress. In the process of phase transformation, the parameters of hydrogen diffusion property of the material changed dramatically in a short time, the hydrogen diffusion coefficient increased in order of magnitude, and the solubility decreased in order of magnitude. This directly led to the upward diffusion of hydrogen in WM, and produced a self-gathering effect. For a welded joint of heavy plate, the self-gathering effect between passes was effective in the short-range and ineffective in the long-range.