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1
Eperješi, Š., M. Matvija, ľ. Eperješi und M. Vojtko. „Evaluation of Cracking Causes of AlSi5Cu3 Alloy Castings“. Archives of Metallurgy and Materials 59, Nr. 3 (28.10.2014): 1089–92. http://dx.doi.org/10.2478/amm-2014-0187.
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Abstract Recently, the castings made from aluminum-silicon alloys by pressure die casting are increasingly used in the automotive industry. In practice, on these castings are high demands, mainly demands on quality of their structure, operating life and safety ensuring of their utilization. The AlSi5Cu3 alloy castings are widely used for production of car components. After the prescribed tests, the cracks and low mechanical properties have been identified for several castings of this alloy, which were produced by low pressure casting into a metal mould and subsequent they were heat treated. Therefore, analyses of the castings were realized to determine the causes of these defects. Evaluation of structure of the AlSi5Cu3 alloy and causes of failure were the subjects of investigation presented in this article.
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Zeng, Yi Dan, Li Tong He und Jin Zhang. „Numerical Simulation of Casting Deformation and Stress of A356 Aluminum Alloy Thin-Walled Frame Casting“. Materials Science Forum 1033 (Juni 2021): 24–30. http://dx.doi.org/10.4028/www.scientific.net/msf.1033.24.
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One of the main reasons for the scrap of cast thin-wall frame aluminum alloy castings is deformation and cracking. It is an effective method for solving the problem by predicting the distribution of casting stress, clarifying the size of the deformation and the location of the crack, and taking necessary measures in the process. This paper uses the ProCAST software to simulate the thermal stress coupling of A356 thin-walled frame castings, analyzes the influence of pouring temperature, pouring speed and mold temperature on the stress field distribution of castings, predicts the hot cracking trend and deformation, and optimizes Casting process..
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Svobodová, Jaroslava, Štefan Michna und Iryna Hren. „Fractographic Analysis of Castings from Al-Si Alloy Produced by Low-Pressure Casting“. Materials Science Forum 994 (Mai 2020): 3–10. http://dx.doi.org/10.4028/www.scientific.net/msf.994.3.
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The article deals with the use of newly developed hypoeutectic silumin type AlSi9NiCuMg0.5 in manufacturing practice. This type of silumin has been produced and patented by a team of workers at the Faculty of Mechanical Engineering at the University of J. E. Purkyně in Ústí nad Labem, Czech Republic. This alloy was developed and tested directly for the technical practice where the special mechanical and technological properties of the alloy were required [1]. The experiment, which is presented in this paper, focuses on the cause of the castings cracking in operating conditions. When the material was put into practice, castings were produced and subsequently used for breaking and cracking across the entire casting section. AlSi9NiCuMg0.5 alloy castings were manufactured using low-pressure technology. The research is focused on the observation of the fracture surface, identification of microstructure of AlSi9NiCuMg0.5 alloy casting and determination of the chemical composition of structural components on the surface of fracture by EDS analysis. Fractional field research has measured the chemical composition and it has been compared with the required declared alloy. Increased iron content and associated intermetallic phases were identified in the alloy. Evaluating of the obtained results can identify the cause of the premature cracking of the castings made from the newly developed hypoeutectic silumin.
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Stradomski, Z., S. Stachura und G. Stradomski. „Fracture Mechanisms in Steel Castings“. Archives of Foundry Engineering 13, Nr. 3 (01.09.2013): 88–91. http://dx.doi.org/10.2478/afe-2013-0066.
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Abstract The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.
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Adamiec, Janusz. „The Assessment of Impact of Construction Factors on Weldability of MSRB Alloy“. Materials Science Forum 690 (Juni 2011): 37–40. http://dx.doi.org/10.4028/www.scientific.net/msf.690.37.
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The purpose of the work was to assess the impact of construction factors on weldability of MSRB alloy. One conducted transvarestraint test, which allowed to assess welds' susceptibility to cracking under the conditions of forced strain of the casting, Fisco test which simulates welding under the conditions of strong stiffening of the weld, as well as Houldcroft test simulating variable strain of the weld. One concluded that the strain of castings is characteristic of the process of pad welding and welding. Assessment of susceptibility of MSRB alloy to cracking under the conditions of forced strain allows to determine the width of the high-temperature brittleness range (HTBR), critical strain speed of the weld CSS and critical temperature strain intensity CST. These parameters are the criteria of hot cracking of welds from MSRB alloy, therefore, they are indicators of the assessment of the alloy's weldability. Castings from MSRB alloys with constant rigidity should be classified as easily weldable. On the other hand, variable rigidity of the casting, resulting from e.g. diverse thickness of the walls, causes significant increase in the alloy's susceptibility to hot cracking.
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Tang, Zheng Lian, und Xin Ping Zhang. „Effect of Rare Earth on 30CrMnSi Steel Investment Castings Cracking“. Advanced Materials Research 160-162 (November 2010): 692–97. http://dx.doi.org/10.4028/www.scientific.net/amr.160-162.692.
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Through adding different amounts of rare earth into the crack sensitive 30CrMnSi steel samples used in investment casting, the cracking tendency of the steel was evaluated and the optimum amount of rare earth addition was obtained. The results show that the cracking susceptibility decreases with the increase of the amount of rare earth added. The cracking susceptibility was lowest at the addition amount of rare earth ferrosilicon alloy being 450g per 50kg of 30CrMnSi steel, while increasing again thereafter with the addition amount up to 600g. It was revealed that the addition of rare earth with an appropriate amount can refine grains, reduce sulfur content, change the volume fraction and size of inclusions as well as improve their distribution, reduce or eliminate ferrite network in castings, and improve the hardness of the matrix, thus finally reduce the cracking susceptibility of the steel.
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Cao, G., und S. Kou. „Hot Cracking Susceptibility of Ternary Mg-Al-Ca Alloys“. Advanced Materials Research 15-17 (Februar 2006): 501–6. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.501.
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Hot cracking of ternary Mg-Al-Ca alloys in permanent mold casting was studied. The alloys are the base of some potential creep-resistant Mg alloys. The Mg-xAl-yCa alloys included Mg-4Al-1Ca, Mg-4Al-2Ca, Mg-4Al-3Ca, Mg-4Al-4Ca, Mg-5Al-3Ca, and Mg-6Al-3Ca. Constrained-rod casting was conducted with a steel mold. Rods were cast with their ends enlarged to act as anchors, which kept the rods from free contraction and thus induced tension in the rods to cause cracking during solidification. The susceptibility to hot cracking was evaluated based on both the widths and locations of cracks in the resultant castings. Both binary Mg-4Al and commercial alloy AZ91E, which is known to have a low susceptibility to hot cracking, were also included for comparison. It was found that within the composition range studied, the crack susceptibility decreased significantly with increasing Ca content (y) but did not change much with the Al content (x).
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Guan, Tian Yang, Zhi Feng Zhang, Min He, Yue Long Bai und Ping Wang. „Effects of Annular Electromagnetic Stirring Melt Treatment on Microstructure and Mechanical Properties of 7050 Rheo-Casting“. Solid State Phenomena 285 (Januar 2019): 219–23. http://dx.doi.org/10.4028/www.scientific.net/ssp.285.219.
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The microstructure and mechanical properties of 7050 alloy rheo-castings after treated by Annular Electromagnetic Stirring (A-EMS) melt treatment were investigated. The results revealed that, under A-EMS, the refinement and homogeneity of the solidification structure could be improved greatly and the slurry was suitable for the following rheo-casting; and also the hot-cracking defects in the casting process were significantly alleviated, meanwhile, the strength and ductility of the alloy casting were found to be comparable to those of conventionally forged 7000 series alloys.
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Cao, G., und S. Kou. „Hot cracking of binary Mg–Al alloy castings“. Materials Science and Engineering: A 417, Nr. 1-2 (Februar 2006): 230–38. http://dx.doi.org/10.1016/j.msea.2005.10.050.
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Łyczkowska, K., J. Adamiec, R. Jachym und K. Kwieciński. „Properties of the Inconel 713 Alloy Within the High Temperature Brittleness Range“. Archives of Foundry Engineering 17, Nr. 4 (20.12.2017): 103–8. http://dx.doi.org/10.1515/afe-2017-0138.
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Abstract Nickel-based alloys are widely used in industries such as the aircraft industry, chemicals, power generation, and others. Their stable mechanical properties in combination with high resistance to aggressive environments at high temperatures make these materials suitable for the production of components of devices and machines intended for operation in extremely difficult conditions, e.g. in aircraft engines. This paper presents the results of thermal and mechanical tests performed on precision castings made of the Inconel 713C alloy and intended for use in the production of low pressure turbine blades. The tests enabled the determination of the nil strength temperature (NST), the nil ductility temperature (NDT), and the ductility recovery temperature (DRT) of the material tested. Based on the values obtained, the high temperature brittleness range (HTBR) and the hot cracking resistance index were determined. Metallographic examinations were conducted in order to describe the cracking mechanisms. It was found that the main cracking mechanism was the partial melting of grains and subsequently the rupture of a thin liquid film along crystal boundaries as a result of deformation during crystallisation. Another cracking mechanism identified was the DDC (Ductility Dip Cracking) mechanism. The results obtained provide a basis for improving precision casting processes for aircraft components and constitute guidelines for designers, engineers, and casting technologists.
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Кузовов, Сергей, Sergey Kuzovov, Константин Макаренко, Konstantin Makarenko, Дмитрий Илюшкин und Dmitriy Ilyushkin. „Features hot cracking under temperature variability pouring steel castings.“ Bulletin of Bryansk state technical university 2014, Nr. 3 (30.09.2014): 38–41. http://dx.doi.org/10.12737/23202.
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12
Álvarez, Pedro, Alberto Cobos, Lexuri Vázquez, Noelia Ruiz, Pedro Pablo Rodríguez, Ana Magaña, Andrea Niklas und Fernando Santos. „Weldability Evaluation of Alloy 718 Investment Castings with Different Si Contents and Thermal Stories and Hot Cracking Mechanism in Their Laser Beam Welds“. Metals 11, Nr. 3 (01.03.2021): 402. http://dx.doi.org/10.3390/met11030402.
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In this work, weldability and hot cracking susceptibility of five alloy 718 investment castings in laser beam welding (LBW) were investigated. Influence of chemical composition, with varying Si contents from 0.05 to 0.17 wt %, solidification rate, and pre-weld heat treatment were studied by carrying out three different weldability tests, i.e., hot ductility, Varestraint, and bead-on-plate tests, after hot isostatic pressing (HIP) and solution annealing treatment. Onset of hot ductility drop was directly related to the presence of residual Laves phase, whereas the hot ductility recovery behaviour was connected to the Si content and γ grain size. LBW Varestraint tests gave rise to enhanced fusion zone (FZ) cracking with much more reduced heat-affected zone (HAZ) cracking that was mostly independent of Si content and residual Laves phase. Microstructural characterisation of bead-on-plate welding samples showed that HAZ cracking susceptibility was closely related to welding morphology. Multiple HAZ cracks were detected in nail or mushroom welding shapes, typical in keyhole mode LBW, irrespective of the chemical composition and thermal story of castings. In all LBW welds, Laves phase with a composition similar to the eutectic of the pseudo-binary equilibrium diagram of alloy 718 was formed in the FZ. The composition of this regenerated Laves phase matched with the continuous Laves phase film observed along HAZ cracks. This was strong evidence of backfilling mechanism, which is described as wetting and infiltration of terminal liquid along γ grain boundaries of parent material. The current results suggest that this cracking mechanism was activated in three-point intersections resulting from perpendicular crossing of columnar grain boundaries with fusion line and was enhanced by nail or mushroom weld shapes and narrow and columnar γ grain characteristics of castings. Neither Varestraint nor hot ductility weldability tests can reproduce this particular cracking mechanism.
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Chen, Tao, Dun Ming Liao und Jian Xin Zhou. „Numerical Simulation of Casting Thermal Stress and Deformation Based on Finite Difference Method“. Materials Science Forum 762 (Juli 2013): 224–29. http://dx.doi.org/10.4028/www.scientific.net/msf.762.224.
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Thermal stress simulation is an important part in the numerical simulation of casting process. It provides engineers with insights into the evolution of displacement, strain and stress of castings in the solidification process. With thermal stress simulation, some defects of casting, i.e. hot tearing, cold cracking and large deformation can be predicted and the engineers are instructed to optimize and improve the casting process. Based on the finite difference method (FDM), this paper presents an integrated numerical method to simulate the thermal stress and deformation of casting in the solidification process. Practical examples show that the method is capable to predict stress distribution and deformation as well as the defects in the experiment.
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Duchek, Michal, Filip Tikal, Jan Nachazel und Bozik Martinek. „Optimization of Heat Treatment of Castings“. Applied Mechanics and Materials 751 (April 2015): 231–34. http://dx.doi.org/10.4028/www.scientific.net/amm.751.231.
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The use of various types of software for rapid identification of potential problems in manufacturing processes is becoming ever more popular. One of such programs is DEFORM, simulation software for forming and heat treatment processes. The purpose of this study was to construct a 3D model of a specific casting, to identify its critical locations and then select the optimum heat treatment procedure preventing cracking. Results of this work include a detailed analysis of stress and temperature fields in the cast part.
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Gawrońska, Elżbieta, Robert Dyja und Norbert Sczygiol. „Stress analysis in solid-liquid parts of solidifying castings“. MATEC Web of Conferences 254 (2019): 02019. http://dx.doi.org/10.1051/matecconf/201925402019.
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In the paper, we present results of stress analysis in domains which are a mixture of solid and liquid phases. Such mixtures occur in solidifying castings and are a result of forming a structure with solid skeleton and filling of a liquid phase. In this structure, stress occurs due to the appearance of temperature gradients, different values of material properties for the solid and liquid phase, and the appearance of friction forces between the solidified part of the casting and the mold on a macroscopic scale. This can lead to casting defects, such as hot cracking. The results are obtained with the use of a authors computer program based on the Finite Element Method. The stress analysis takes into account the elastic-plastic state of considered computational area. The presented results are focused on the microscopic scale, for which a finite element mesh is created which imitates the growing grains of the metal alloy in the casting, on the basis of macroscopic parameters.
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Guan, J., G. W. Dieckhues und P. R. Sahm. „Analysis of residual stresses and cracking of γ-TiAl castings“. Intermetallics 2, Nr. 2 (Januar 1994): 89–94. http://dx.doi.org/10.1016/0966-9795(94)90002-7.
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17
Manohar, P. A. „Stress Corrosion Cracking Failure of Jackbolts for Die Casting Press“. Materials Science Forum 539-543 (März 2007): 2162–67. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2162.
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Several prematurely failed jack bolts were analyzed to determine the root causes of failure. Bolts were employed to ensure that die halves do not separate during casting of high pressure die castings of light metals. Fractography of jack bolts revealed unusual morphology consisting of both circumferential and longitudinal cracking. The basic fracture type was identified as transgranular cleavage (brittle) fracture mode. SEM / EDS analysis of the fracture surface revealed the presence of, to varying degrees, chemical species containing sulfur (S), oxygen (O) and chlorine (Cl). Material composition, heat treatment, microstructure and hardnesses of the jack bolts were found to be in agreement with the expected steel grade and properties. It was concluded that the failure of the bolts was due to a combination of inappropriately chosen mechanical properties of the bolts, operating stress, and the presence of corrosive environmental materials leading to ideal conditions that promoted stress corrosion cracking failures. Suitable remedial actions to alleviate the risk of SCC failure of the bolts are presented and discussed in the paper.
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Adamiec, Janusz. „The Quantitative Assessment of the Fracture Profile of Magnesium Alloy QE22 Welded Joint“. Solid State Phenomena 197 (Februar 2013): 215–20. http://dx.doi.org/10.4028/www.scientific.net/ssp.197.215.
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Magnesium alloys are a part of a group of lightweight and ultra-lightweight alloys, which are important in practical use in constructions. QE22 casting magnesium alloy containing silver, rare earth elements and zirconium is characterized by creep resistance up to the temperature of 200 °C, while during a short exposure it can resist up to the temperature of 250°C. Nowadays, QE22 magnesium alloy are used for casting into sand moulds. In castings of magnesium alloys defects or inconsistencies (such as casting misruns, porosities and cracks) often appear, particularly in huge dimensional castings. Such defects are repaired with the use of padding and welding. Welded joints must ensure suitable operational properties, mainly in terms of creep, so that the repaired casting can work under the same conditions as the correct cast. The basic source of information about the cause and cracking propagation is fracture after creep test. The quantitative fractography, in particular profilomety, allows to describe the fracture and basis on it conclude the causes of destruction. In this paper quantitative procedure for assessing the fracture profile of QE22 welded joints after creep test was worked out. Base on its analysis result, it was found that creep resistant of the QE22 joints is determined by eutectic areas, therefore they must be heat treated after welding joints.
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Bernstein, H. L., R. C. McClung, T. R. Sharron und J. M. Allen. „Analysis of General Electric Model 7001 First-Stage Nozzle Cracking“. Journal of Engineering for Gas Turbines and Power 116, Nr. 1 (01.01.1994): 207–16. http://dx.doi.org/10.1115/1.2906794.
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Analyses of first-stage nozzle cracking in General Electric Model 7001B and 7001E industrial gas turbines are presented. Empirical algorithms are developed to predict the maximum extent of cracking that is visible on these nozzles as a function of engine cyclic history and the number of fired hours. It is shown that the algorithms predict this cracking to within a factor of two. Metallurgical analyses of nozzles show that crack growth follows the carbide-matrix interface, environmental attack occurs at the crack tip, and that the microstructure changes by increasing the amount of carbide precipitation, which increases the hardness. These metallurgical results, along with mechanical test data and stress analyses from the literature, are used to understand the nature of nozzle cracking. The maximum extent of cracking coincides with locations of maximum thermal stresses as determined by finite element analyses of similar nozzle designs. This location is at the airfoil-shroud junction on the middle vanes of multivane castings. The use of these algorithms as a predictive maintenance tool and the ability to inspect nozzles visually in the engine also are discussed.
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Zych, J., und J. Wróbel. „Influence of the Selected Factors on Thermal Fatigue of the ADI in an Aspect of its Suitability as the Material for Metal Moulds“. Archives of Metallurgy and Materials 59, Nr. 2 (01.06.2014): 693–97. http://dx.doi.org/10.2478/amm-2014-0113.
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Abstract The investigation results of the thermal fatigue resistance of two ADI grades (EN-GJS-1200-2 and EN-GJS-800-8) are presented in the paper. Tests were performed on the author’s research stand, by means of the resistance heating of samples acc. L.F. Coffin method. The thermal fatigue resistance is the basic criterion in assessing the material suitability for metal moulds. The maximal temperature (Tmax) of thermal cycles influence on their number, which the sample can withstand before cracking, were estimated. Structure transformations, hardness and strength changes of the austempered ductile iron (ADI) were analysed. It was found, that at cyclic heating to Tmax <500°C, the ADI retains its primary ausferritic structure, even after more than 10.000 thermal cycles. Such ADI behaviour predisposes it to be applied as a material for metal moulds used in the pressure die casting, it means mainly at casting Mg and Zn alloys as well as for small castings of Al alloys.
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Stephan, D. „Testing the susceptibility of welds in high alloy steel castings to hot cracking“. Welding International 5, Nr. 3 (Januar 1991): 227–29. http://dx.doi.org/10.1080/09507119109446726.
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Wu, Xin Hua, D. Hu und M. H. Loretto. „Processing and Alloy Development to Optimise the Properties and Cost-Effectiveness of Components Manufactured from TiAl-Based Alloys“. Materials Science Forum 449-452 (März 2004): 25–30. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.25.
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The IRC has carried out a major research programme over the last ten or so years aimed at developing the processing and optimisation of TiAl-based alloys. This work has covered melting, the production of shaped castings, powder processing and a range of thermomechanical processing routes in parallel with alloy development. In this paper the work aimed at understanding the factors that influence the properties of thermo-mechanically processed and cast samples of TiAl-based alloys will be reviewed. It is shown that the use of boron to control the grain size of castings leads to limited ductility in the stronger and more highly alloyed TiAl alloys because ribbon-like borides up to 200µm in length can be formed. It is also shown that although a fully lamellar microstructure offers a good balance of properties their plastic anisotropy leads to pre-yield fracture and to reduced fatigue life. It is clear that grain size control is essential if an acceptable balance of properties is to be obtained but that if casting is to be used grain refinement via boron addition is not totally satisfactory. A simple heat treatment can be used to refine the microstructure of cast boron-free alloys, which leads to ductility comparable with that in wrought samples and the associated convoluted microstructure should also eliminate pre-yield cracking.
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Leushina, L. I., I. O. Leushin, S. V. Plokhov und V. B. Deev. „Recycling of shards of quartz ceramic shells from investment casting“. Izvestiya Visshikh Uchebnykh Zavedenii. Chernaya Metallurgiya = Izvestiya. Ferrous Metallurgy 61, Nr. 11 (24.12.2018): 859–65. http://dx.doi.org/10.17073/0368-0797-2018-11-859-865.
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The use of quartz for its low-temperature modification creates additional risks in the manufacture of molds in the part of their reduced crack resistance due to polymorphous transformations and in practice it often leads to cracking and even destruction of individual layers of the shell wall or the mold as a whole. Preliminary calcination of the covering material practiced in many foundries can somewhat reduce the negative consequence of dangerous polymorphic transformations of quartz. But at the same time, smooth heating of the molds to reduce the likelihood of their cracking, which is carried out in the support filler, contributes to an increase in duration of the technological process and in additional energy costs. Among the options for reducing the likelihood of cracking and the destruction of RP during their calcination, the most popular is replacement of pulverized quartz sand, as filler, with dispersed quartz sand of a polyfraction composition, disten-sillimanite, pulverized aluminosilicate, spherical corundum or fused quartz. However, all of them are quite expensive and do not meet modern challenges and resource saving requirements in foundry and metallurgical industries. In this connection, attention is drawn to the ceramic shards of shells of steel and aluminum investment casting on silica-based models. At present, the shards of spent ceramic shell molds for investment models is not used for recycling. This material is sent to the dump or used as a supporting filler of the flasks when the shells are formed therein. The conducted component chemical and phase analysis of the material has shown that in shards of ceramic shells formed after knocking out steel and aluminum castings from molds, in addition to quartz in the high-temperature phases of tridymite and cristobalite (base), there are up to 5 - 10 % of iron and iron scale and 3 - 5 % of aluminum and its oxides. The use of ceramic shell shards as a covering material excludes the repeated polymorphic quartz transformations during calcination and pouring of shapes that determine the change in volume, density, and change in types of material crystal lattices, which makes it possible to increase the fracture toughness and strength of the shells and to minimize discard of the resulting castings. Residual iron, aluminum and their oxides contribute to improving the processability of the mold. Experimental testing of the proposed recycling option in the conditions of current production has confirmed its effectiveness.
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Klimpel, A., M. Mazur und Z. Bulski. „Zirconium and the occurrence of weld cracking during the welding of GA8 magnesium alloy castings“. Welding International 17, Nr. 2 (Januar 2003): 94–97. http://dx.doi.org/10.1533/wint.2003.3073.
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du Toit, Madeleine, Patronica Letsoalo und Heinrich Möller. „Fusion Welding of Rheocast Semi-Solid Metal (SSM) Processed Aluminium Alloy 7017“. Solid State Phenomena 192-193 (Oktober 2012): 161–66. http://dx.doi.org/10.4028/www.scientific.net/ssp.192-193.161.
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Near-net shape casting of wrought aluminium alloys has proven to be difficult due to a tendency towards hot tearing during cooling. Rheocasting, or semi-solid metal (SSM) processing followed by high pressure die casting (HPDC), has recently been shown to be an effective alternative to conventional die casting, yielding near-net shape wrought aluminium alloy castings with less risk of hot tearing. This casting process involves pouring the liquid metal into a processing cup, which is then transferred into a coil for induction stirring and simultaneous forced air cooling. When the metal reaches the semi-solid casting temperature, the resultant slurry is transferred to a high pressure die casting machine and cast to near-net shape. This modifies the as-cast microstructure, yielding a more globular primary phase and results in mechanical properties in the -T6 condition closely approaching those of wrought material in the same condition. Little information is currently available on the response of SSM-HPDC material to welding. This project investigated the influence of autogenous laser and gas tungsten arc welding on the microstructure and mechanical properties of aluminium 7017 after rheocasting. It is possible to successfully weld this material without solidification or liquation cracking. The effect of welding on the rheocast microstructure in the heat-affected zone and weld metal was shown, and the hardness and tensile properties of the resulting joints in the as-welded condition were tested and related to the microstructures achieved.
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Molnár, Dániel, und Jenő Dúl. „The Influence of the Solidification Process to the Dimensional Accuracy of Castings“. Materials Science Forum 649 (Mai 2010): 431–36. http://dx.doi.org/10.4028/www.scientific.net/msf.649.431.
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The real system under consideration comprises of a solidifying casting with the casting mould, environment and other external influences. The process observed begins with the introduction of liquid metal to the channels of the runner system and filling of the mould cavity. This is connected with the contact of liquid metal with the atmosphere and also, with the walls of the mould. During the filling of the mould cavity heat transfer between the metal surface and the walls of the mould takes place (by radiation and conduction), which in practice can lead to mould cracking, and next to the formation of casting surface defects. In this stage of the process of great significance are the hydrodynamic conditions. These are dependent on the metal itself (its viscosity), and also on the runner system (rate of flow, resistances). During this time in the volume of the casting and mould, a pseudo-initial temperature fields is generated which is significant for the filling of the mould cavity and also for further cooling and solidification of the casting.
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Stradomski, G. „The Role of Carbon in the Mechanism of Ferritic-Austenitic Cast Steel Solidification“. Archives of Foundry Engineering 14, Nr. 3 (08.08.2014): 83–86. http://dx.doi.org/10.2478/afe-2014-0067.
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Abstract The paper presents the results of research on the microstructure of GX2CrNiMoCuN25-6-3-3 and GX2CrNiMoCuN25-6-3 cast steels with a varying carbon content. The cause for undertaking the research were technological problems with hot cracking in bulk castings of duplex cast steel with a carbon content of approx. 0.06% and with 23% Cr, 8.5% Ni, 3% Mo and 2.4% Cu. The research has shown a significant effect of increased carbon content on the ferrite and austenite microstructure morphology, while exceeding the carbon content of 0.06% results in a change of the shape of primary grains from equiaxial to columnar.
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Yang, Jing’an, Baicheng Liu und Houfa Shen. „Study of hot cracking potential in a 6-ton steel ingot casting“. Metallurgical Research & Technology 115, Nr. 3 (2018): 308. http://dx.doi.org/10.1051/metal/2017106.
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A new hot cracking potential (HCP) criterion, for the appearance of hot tearing in steel ingot castings, is proposed. The maximum value of the first principal stress, divided by the dynamic yield strength in the brittle temperature range (BTR), was used to identify the HCP. Experiments were carried out on a 6-ton P91 steel ingot in which severe hot tearing was detected in the upper centerline. Another ingot, with a better heat preservation riser, and without hot tearing, was used for comparison. Samples were obtained from the area of the ingot body with hot tearing, and their morphologies were inspected by a X-ray high energy industrial computed tomography. The carbon and sulfur distributions around the hot tearing were characterized by an infrared spectrometry carbon and sulfur analyzer. High temperature mechanical properties were obtained by a Gleeble thermal simulation machine, under different strain rates. Then, thermo-mechanical simulations using an elasto-viscoplastic finite-element model were conducted to analyze the stress and strain evolution during ingot solidification. The results showed that the hot tearing area, which was rich in both carbon and sulfur, was under excessive tensile stress in the BTR, bearing the highest HCP.
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Omar, M. F. M., S. Sharif, Mustaffa Ibrahim, Mohd Hasbullah Idris, A. S. A. Fadzil und Azriszul Mohd Amin. „Differential Ceramic Shell Thickness Evaluation for Direct Rapid Investment Casting“. Applied Mechanics and Materials 315 (April 2013): 418–22. http://dx.doi.org/10.4028/www.scientific.net/amm.315.418.
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Rapid prototyping (RP) process offers a promising economical way as a sacrificial pattern in investment casting (IC) at high speed and low cost for low volume part manufacturing. However direct sacrificial RP pattern have encountered shell cracking during burnout process due to polymer based materials. Shell mould thickness was need to be concerned to have strong enough to withstand RP part expansion for employing direct method. The aim of present research was to compare the efficacy of different shell thickness for aluminum casting part fabricated from acrylonitrile butadiene styrene (ABS) and acrylate based material made from FDM and MJM respectively. The hollow RP pattern has been used directly to produce ceramic moulds. The feasibility of ceramic mould has been assessed in term of burnout ability and crack defect. Dimensional accuracies and surface roughness of the castings part have been observed in this investigation. Result shows thicker mould with proposed stuco procedure resulted without any crack defect for botRP part and no residual ash remained when firing higher than 870°C of temperature.In addition, FDM produced better accuracy for overall mould thickness, but MJM have better surface roughness. Therefore both direct RP pattern were suitable to be used in IC process with proposed shell thickness.
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Evstigneev, A. I., V. I. Odinokov, A. V. Sviridov, E. A. Dmitriev und V. V. Petrov. „Mathematical Modelling of Stress-Strain State of Multilayer Shell Molds“. Materials Science Forum 857 (Mai 2016): 565–72. http://dx.doi.org/10.4028/www.scientific.net/msf.857.565.
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The analysis of the trends for development of technological processes to form shell molds shows that the accuracy and purity of the surface of shaped castings are one of the main criteria for the level of development of the science and technology of foundry engineering. The equations of continuum mechanics and thermal conductivity and the numerical method were used to build a mathematical model of SSS of multilayer shell mold to determine the temperature fields in a shell mold and solidifying casting, thickness of solidified layer of the casting, stress, strain, and displacement of shell layers against each other, as well as ferrostatic pressure on the metal form. The calculation results show that at metal casting, the highest temperature differences occur between the first and second layers of a shell mold, and the maximum values of the stresses and strains are typical for the first layer of a shell mold. The mechanism of the effect of temperature difference between the layers of the shell mold on fracture toughness of the shells and its critical value are determined, above which either a decomposition of a shell mold occur, or through-thickness cracking occur, which lead to the destruction of a shell mold. The ignition process of shell molds in the control filler has no significant influence on the formation of cracks, since the temperature difference between the shell layers does not reach critical values.
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Schindler, Ivo, Stanislav Rusz, Rostislav Kawulok, Petr Kawulok, Miroslava Subíková und Michal Cagala. „Homogenization of Microstructure of Castings from the Alloy Fe-40at.%Al-Zr-B“. Materials Science Forum 782 (April 2014): 87–92. http://dx.doi.org/10.4028/www.scientific.net/msf.782.87.
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The samples intended for the study of static recrystallization on plastometer Gleeble were prepared from the laboratory castings of iron aluminide containing 24.6 Al 0.17 Mn 0.16 Zr 0.026 B 0.004 C (in wt. %, remainder Fe). Nevertheless, the structure analysis discovered that the results were excessively influenced by the huge heterogeneity of the as-cast microstructure, mostly of the grain size. Combination of the hot forming and recrystallization process during the long-term high-temperature annealing was selected for the necessary structure homogenization. As the tested intermetallic alloy is extremely brittle and susceptible to surface cracking, the original method was applied for its processing. The method consists in hot rolling in the protective capsules welded from the ferritic stainless steel sheet. The castings were rolled to 2/3 of their thickness by 4 reductions with the inter-stage heating, and then annealed at the temperature of 1200 °C in the vacuum furnace for several periods. Metallographic analysis revealed that annealing lasting 7 hours was essential for the uniform coarsening of the recrystallized grains. Material processed in this way proved successful for the subsequent metallographical study of static recrystallization.
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Papkovskiy, P. I., A. I. Valko und S. G. Sandomirskii. „Influence of non-ferrous metals on the structural quality of the high-alloy mild steel 20X2H4A billets received by centrifugal electroslag remelting“. Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), Nr. 1 (07.04.2020): 65–73. http://dx.doi.org/10.21122/1683-6065-2020-1-65-73.
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The problem of the formation of cracks and the conditions of their origin in the cast of metal products have been widely studied in world practice, but the real mechanism of this process is not yet clear enough that it could be applied in production. Hot cracks – one of the most common and the most detrimental defects of steel castings, leading to a significant increase in the cost of products. The formation of hot cracks in steel castings depends on many factors, including the chemical composition of steel, the presence of non-metallic inclusions and gases, conditions of deoxidation and solidification of steel, etc. Therefore, special attention in the real conditions of production should be given to the metallurgical side of the issue. There is no quantitative measure of steel purity in the books of steel, which is divided into chemical, defined by the chemical analysis, and metallographic, defined by the content of non-metallic inclusions. The effect of the general purity of steel on the characteristics of destruction is studied sufficiently, but the data on the individual impact of impurities is very incomplete.In many respects, pure steel has a clear advantage over steel with harmful impurities. This applies to all mechanical properties associated with destruction or processes occurring on the edge of grains. The cardinal way of obtaining cleaner steel, including the reduction of impurities of non-ferrous metals, is the use of pure original charge mixture.The article discusses the topical problem of cracking formation after chemical-thermal treatment in the material of sun gears of the second row of quarry dump trucks BELAZ, obtained by the method of CESR rolled steel 20X2H4А, the possible impact of small concentrations of non-ferrous metals (Pb, Zn, Sn, Bi, As, Se) on the development of external and internal cracks in castings and on structural heterogeneity of steel after CESR.The obtained results allowed to draw conclusions about the impact of non-ferrous metals on the formation of cracks in castings and to establish their limited quantitative characteristics. Based on the results, measures have been proposed to minimize the impact of small amounts of non-ferrous metals on the formation of cracks in castings.
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Cieśla, Marek, Franciszek Binczyk und Marcin Mańka. „Analysis of Cracking Process in Conditions of High-Temperature Creep of Castings Form the Modified Superalloy IN-713C“. Solid State Phenomena 212 (Dezember 2013): 247–54. http://dx.doi.org/10.4028/www.scientific.net/ssp.212.247.
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mpact of complex modification and filtration during pouring into moulds on durability has been evaluated in this study in conditions of high-temperature creep of castings made from nickel superalloy IN-713C post production rejects. The conditions of initiation and propagation of cracks in the specimens were analysed with consideration of morphological properties of material macro-, micro-and substructure. It has been demonstrated that in conditions of high-temperature creep at temperature 980°C with stress σ =150 MPa creep resistance of the IN-713C superalloy increases significantly with the increase of macrograin size. Creep resistance of specimens made of coarse grain material was significantly higher than the resistance of fine grain material.
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Kopyciński, D., D. Siekaniec, A. Szczęsny, M. Sokolnicki und A. Nowak. „The Althoff-Radtke Test Adapted for High Chromium Cast Iron“. Archives of Foundry Engineering 16, Nr. 4 (01.12.2016): 61–64. http://dx.doi.org/10.1515/afe-2016-0084.
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Abstract The paper presents results of the possibility of adapting the Althoff-Radtke test for High Chromium Cast Iron. The Althoff-Radtke test is a clump attempt used for steel. The Althoff-Radtke test has four different lengths of clamp which qualifies it as a test to quantitatively take into account different kinds of shrinkage ΔL. The length of the slot of the cracked corner and the length of each staple (50 - 350 mm) are the parameters tendency to cast cracks. Castings of white cast iron have a high tendency to hot cracking due to the large range of solidification temperatures, unfavorable kinetics parameters of shrinkage, and especially a lack of expansion before shrinkage. Shrinkage of high chromium white cast iron is similar to the shrinkage of cast steel, and is approximately 2%. Therefore it is important to test susceptibility to hot cracks. Research was carried out under industrial conditions. Four melts were performed, one of the initial chemical composition and the other three modified by different amounts of Fe-Ti, respectively, 0.25%, 0.5% and 0.75% Fe-Ti. The propensity for hot cracking was based on the observation of the dark surface in the corner of the sample. The study shows that the Althoff-Radtke test can be adapted to determine the tendency for hot cracking of high chromium cast iron. It should however be noted that the test results cannot be compared with those for other alloys.
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Turowska, A., und J. Adamiec. „Mechanical Properties of WE43 Magnesium Alloy Joint at Elevated Temperature / Właściwości Mechaniczne Złączy Ze Stopu Magnezu WE43 W Podwyższonej Temperaturze“. Archives of Metallurgy and Materials 60, Nr. 4 (01.12.2015): 2695–702. http://dx.doi.org/10.1515/amm-2015-0434.
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The WE43 cast magnesium alloy, containing yttrium and rare earth elements, remains stable at temperatures up to 300°C, according to the manufacturer, and therefore it is considered for a possible application in the aerospace and automotive. Usually, it is cast gravitationally into sand moulds and used for large-size castings that find application in the aerospace industry. After the casting process any possible defects that might appear in the casting are repaired with the application of welding techniques. These techniques also find application in renovation of the used cast elements and in the process of joining the cast parts into complex structures. An important factor determining the validity of the application of welding techniques for repairing or joining cast magnesium alloys is the structural stability and the stability of the properties of the joint in operating conditions. In the literature of the subject are information on the properties of the WE43 alloy or an impact of heat treatment on the structure and properties of the alloy, however, there is a lack of information concerning the welded joints produced from this alloy. This paper has been focused on the analysis the microstructure of the welded joints and their mechanical properties at elevated temperatures. To do this, tensile tests at temperatures ranging from 20°C to 300°C were performed. The tests showed, that up to the temperature of 150°C the crack occurred in the base material, whereas above this temperature level the rapture occurred within the weld. The loss of cohesion resulted from the nucleation of voids on grain boundaries and their formation into the main crack. The strength of the joints ranged from 150 MPa to 235 MPa, i.e. around 90 % of strength of the WE43 alloy after heat treatment (T6). Also performed a profilometric examination was to establish the shape of the fracture and to analyze how the temperature affected a contribution of phases in the process of cracking. It was found that the contribution of intermetallic phases in the process of cracking was three times lower for cracks located in the area of the weld.
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Crha, Jan, J. Havlíček, Jiri Molínek und Petr Kozelský. „Acoustic Emission Monitoring during Solidification Processes“. Advanced Materials Research 13-14 (Februar 2006): 299–304. http://dx.doi.org/10.4028/www.scientific.net/amr.13-14.299.
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The paper summarizes the experiences acquired from on-line acoustic emission monitoring (herafter AE) of heavy castings during their manufacturing (solidification and following cooling in the mould). They are usually monitored elastic waves generated above all by stress changes in the solid state. In order to exactly determine plastic-elastic transition state the investigation was focused on raising the sensitivity of detection. The suitable experimental technique is discussed in the first part of this article. The main problem of the measurement by high temperatures was solved by using waveguides. It is very important in this case to select useful signal sources from mechanical and electromagnetical disturbances. Some laboratory experiments were done for studying the signal origin in the first state of solidification. The results from on-line monitoring of two types cast rolls during manufacturing were compared. Each type of casting has its typical AE histogram. For the quality evaluation ( in our case) is significant the time period of approximate 5 days after pouring . The time delayed stress induced cracking generates high level AE signal in this time period and the presence of such signal indicates defective product. The study of high temperature tensile tests, structural phase transformation and solidification processes using AE is very important for analysis of AE sources. The use of the laboratory results for the AE source analysis on real products will be subject to futher research.
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Martinez Holguin, David A., Seungkyu Han und Namsoo P. Kim. „Magnesium Alloy 3D Printing by Wire and Arc Additive Manufacturing (WAAM)“. MRS Advances 3, Nr. 49 (2018): 2959–64. http://dx.doi.org/10.1557/adv.2018.553.
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ABSTRACTMechanical properties similar to natural bone and good biocompatibility make magnesium a great option for its use as biodegradable implant material. The use of castings as fabrication technique brings inherent problems, such as segregation and void formation. Also, the architecture of the specimens created by using these techniques is limited. This study shows the implementation of WAAM for the fabrication of elements made out of AZ91D magnesium alloy (9% aluminium and 1% zinc). The results demonstrate that porosity or cracking only appears at the surface of the individual printed lines, while the central sections presents a void-less structure composed by an HCP magnesium matrix and a high density of well dispersed aluminium-zinc rich precipitates. EDS mapping confirms the presence of orthorhombic Al5Mg11Zn4 phase. Also, the relationship between the heat present in the system and the morphology of the lines is analysed.
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Sediako, Dimitry, Joshua Stroh, Alexandra McDougall und Ermia Aghaie. „Residual Stress Analysis of A362 Aluminum Alloy Gear Case Using Neutron Diffraction“. Materials Science Forum 941 (Dezember 2018): 1288–94. http://dx.doi.org/10.4028/www.scientific.net/msf.941.1288.
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Mercury Marine has used a new alloy, Mercalloy A362, for the manufacturing of a re-designed lower unit transmission gearcase. The enhanced strength of the alloy allowed for a substantial weight reduction in the new design. The purpose of this study was to examine and determine why cracking may develop in the gear casing during in service testing. Two types of material states, (i) as cast and (ii) heat treated were compared. Metallography and neutron diffraction analysis was carried out at locations identified as being areas of high stress by Magma software – which was performed in a separate study. Microstructural characterization at these locations revealed microstructural and the compositional differences. Differences in the porosity, eutectic phase, and volume fraction of the precipitates were observed at various locations of interest in each material state. The residual stress analysis was performed with application of neutron diffraction and revealed that the stresses in the as-cast component reached a maximum value of 120 MPa, which is below the yield strength of the alloy. The heat treatment applied to the castings reduced the stress by approximately 50 MPa. Based on the microstructure and neutron diffraction results, it is likely that performing a heat treatment process extends the lifetime of the component, however, it may not completely eliminate the cracking problem. Farther studies are currently nearing completion, targeting the mass production of the redesigned gearcase.
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Burnat, B., M. Parchańska-Kowalik und L. Klimek. „The Influence of Chemical Surface Treatment on the Corrosion Resistance of Titanium Castings Used in Dental Prosthetics“. Archives of Foundry Engineering 14, Nr. 3 (08.08.2014): 11–16. http://dx.doi.org/10.2478/afe-2014-0052.
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Abstract Air abrasion process is used for cleaning casting surface of prosthetic components, and to prepare the surface of these elements for the application of veneering items. Its side effect, however, is that abrasive particles are embedded in the treated surface, which can be up to 30% of the surface and it constitutes the side effect of this procedure. Such a significant participation of foreign material can not be indifferent to the properties of the surface. Embedded particles can be the place of stress concentration causing cracking of ceramics, and may deteriorate corrosion resistance by forming corrosive microlinks. In the latter cases, it would be advisable to remove elements embedded into the surface. The simplest method is chemical etching or electrochemical one. Nevertheless, these procedures should not significantly change the parameters of the surface. Among many possible reagents only a few fulfills all the above conditions. In addition, processing should not impair corrosion resistance of titanium, which is one of the most important factors determining its use as a prosthetic restoration in the mouth. The study presented results of corrosion resistance of titanium used to make prosthetic components by means of casting method, which were subjected to chemical processing designed to remove the embedded abrasive particles. The aim of the study was to investigate whether etching with selected reagents affects the corrosion resistance of titanium castings. For etching the following reagents were used: 30% HNO3 + 3% HF + H2O, HNO3+ HF+ glycerol (1:2:3), 4% HF in H2O2, 4% HF in H2O, with a control sandblasted sample, not subjected to etching. Tests demonstrated that the etching affected corrosion properties of test samples, in each case the reduction of the corrosion potential occurred - possibly due to the removal of particles of Al2O3 from the surface and activation of the surface. None of the samples underwent pitting corrosion as a result of polarization to 9 V. Values of the polarization resistance, and potentiodynamic characteristics indicated that the best corrosion resistance exhibited the samples after etching in a mixture of 4% solution of HF in H2O2. They showed very good passivation of the surface.
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Suprapto, Wahyono, Bambang Suharno, Johny Wahyuadi Soedarsono und Dedi Priadi. „Analytical and Experimental Models of Porosity Formation of Duralumin Cast in Vacuum Casting System“. Advanced Materials Research 277 (Juli 2011): 76–83. http://dx.doi.org/10.4028/www.scientific.net/amr.277.76.
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Porosity in cast metals often leads to cracking of components due to stress concentration and leakage, and as the result, the castings need be repaired or rejected. Disharmony in casting process was resulting in porosity. Prediction of porosity in the casting is necessary as a step to avoid the waste products and reduce costs. But to ensure whether these predictions are accurate and precise, it is still necessary to validate the test trials and testing. This paper aims to provide early information when, where, and how large a defect occurs in particular foundry casting porosity on duralumin. The analytical study of porosity formation based analytic equilibrium wt% of element, the behavior of the thermodynamic, hydrodynamic, and rules of metallurgical on vacuum casting of duralumin. Experiments as a validation study are conducted by duralumin remelting on stainless-steel bowl in a vacuum casting furnace. Analytical simulation and experiments of the casting that has been vacuumed by melting 10 cmHg pressures higher than the pressure solidification, and duralumin melt is poured automatically into permanent mold carbon steel. In the study cast duralumin created five different thicknesses. Both these studies assume the addition of copper (2.5%, 3.0%, 3.5 %, 4.0%, and 4.5% Cu) and vacuum pressure (76, 50, 40, cmHg), as independent variables, while dependent variable in the studies is porosity characteristics, which includes morphology, number and dimensions of the porosity. Optical emission spectrometry test, Reynold's and Niyama numbers, Sievert's law, Archimedes' principle (Pycnometry and Straube-Pfeiffer tests), and Eichenauer equation are instruments which are used to determine the characterization of duralumin casting porosity. Duralumin ingots remelting process was performed by the control pressure (p1) and temperature (T1). Vacuuming process performed after the smelting room temperature reaches 600 °C. Once melted, it followed by duralumin into a permanent mold (p2, T2). As a control parameter is the height of pouring (7 cm), pour temperature and mold temperature respectively at 750 °C and 300 °C. The porosity characteristics studies of two models produce two types of porosity (gas and shrinkage), the quantity dimension and porosity, and distribution of porosity in the cast duralumin.
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Francis, Roger, und Stan Hebdon. „The Corrosion of Cast Duplex Stainless Steels in Seawater and Sour Brines“. CORROSION 75, Nr. 11 (16.09.2019): 1383–90. http://dx.doi.org/10.5006/3284.
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Modern duplex stainless steels have been in use since the early 1970s and cast versions of the wrought alloys were soon in demand for pumps and valves. Since that time a range of cast duplex stainless steels have been developed with a wide range of compositions, but all with approximately 50/50 austenite/ferrite phase balance and deliberate additions of nitrogen. This paper presents some comparative corrosion data on a range of cast duplex stainless steels, mainly in seawater. The differences in performance related to composition and microstructure are discussed. Corrosion data in lower chloride brines are also presented to show the limits of use of some lower alloyed duplex materials. In addition to oxidizing chloride solutions, some data are presented on cast duplex stainless steels in reducing brines containing H2S, where the main corrosion problem is sulfide stress corrosion cracking. Finally, the importance of using a suitable technical specification, over and above ASTM, combined with selecting a suitably skilled foundry in order to obtain satisfactory castings is discussed.
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Yang, Keun-Hyeok. „Shear Stress-Relative Slip Relationship at Concrete Interfaces“. Advances in Materials Science and Engineering 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/6475161.
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This study develops a simple and rational shear stress-relative slip model of concrete interfaces with monolithic castings or smooth construction joints. In developing the model, the initial shear cracking stress and relative slip amount at peak stress were formulated from a nonlinear regression analysis using test data for push-off specimens. The shear friction strength was determined from the generalized equations on the basis of the upper-bound theorem of concrete plasticity. Then, a parametric fitting analysis was performed to derive equations for the key parameters determining the shapes of the ascending and descending branches of the shear stress-relative slip curve. The comparisons of predictions and measurements obtained from push-off tests confirmed that the proposed model provides superior accuracy in predicting the shear stress-relative slip relationship of interfacial shear planes. This was evidenced by the lower normalized root mean square error than those in Xu et al.’s model and the CEB-FIB model, which have many limitations in terms of the roughness of the substrate surface along an interface and the magnitude of equivalent normal stress.
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Ksiazek, Marzanna, Lukasz Boron und Adam Tchorz. „Study on the Microstructure, Mechanical Properties, and Erosive Wear Behavior of HVOF Sprayed Al2O3-15 wt.%TiO2 Coating with NiAl Interlayer on Al-Si Cast Alloy“. Materials 13, Nr. 18 (16.09.2020): 4122. http://dx.doi.org/10.3390/ma13184122.
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Alumina oxide coatings are widely used in many industrial applications to improve corrosion protection, wear and erosion resistances, and thermal insulation of metallic surfaces. The paper presents study of the microstructure, mechanical, and wear properties of HVOF (high velocity oxy-fuel process) sprayed of Al2O3-15 wt.% TiO2 coating with the NiAl interlayer on the surface of Al-Si alloy castings. The microstructure of Al2O3-15 wt.% TiO2/NiAl coating was characterized by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of coating with low porosity, compact structure, good adhesion to the substrate with typical lamellar structure composed of a solid phase consisting of compounds included in the coating material and their phase variations. For analysis of the adhesion of coatings to the substrate, the scratch test was applied. An assessment of the erosive wear resistance of coatings was also carried out, confirming the significant impact of the interlayer as well as the microstructure and phase composition of the oxide coating on the wear resistance of the tested coating system. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the Al2O3-15 wt.% TiO2/NiAl/Al-Si alloy as microhardness and erosion resistance of the coating. It was found that the introduction of the NiAl metallic interlayer significantly increased resistance to cracking and wear behavior in the studied system.
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Burapa, R., S. Rawangwong, J. Chatthong und Worapong Boonchouytan. „Effects of Mold Temperature and Casting Temperature on Hot Cracking in Al-4.5 wt.% Cu Alloy“. Advanced Materials Research 747 (August 2013): 623–26. http://dx.doi.org/10.4028/www.scientific.net/amr.747.623.
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Hot cracking is an important defect that occurs during solidification of aluminum-copper alloys. In this present work, the effects of mold temperature and casting temperature on hot cracking in the Al-4.5 wt.% Cu alloy has been studied using a ring mold for hot cracking assessment. For the experimental conditions, three mold temperatures between 150 and 350°C and three casting temperatures between 670 and 770°C were studied and Al-7 wt.% Si alloy was used as reference for comparison. The results showed Al-7 wt.% Si alloy has high resistance to hot cracking and no hot cracking forms under three different mold temperatures, while Al-4.5 wt.% Cu alloy shows significant hot cracking tendency under the same casting conditions. The severity of hot cracking in Al-4.5 wt.% Cu alloy decreased significantly with increasing the mold temperature and decreasing the casting temperature. On the other hand, an increasing casting temperature resulted in severer hot cracking in Al-4.5 wt.% Cu alloy.
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Maslak, Volodymyr, Yevhenii Lashko und Olga Chencheva. „Theoretical and practical aspects of the identification of the bladed weapon on the example of the SG 98/05 bayonet to the Mauser rifle based on metal science research“. History of science and technology 11, Nr. 1 (26.06.2021): 191–211. http://dx.doi.org/10.32703/2415-7422-2021-11-1-191-211.
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The article examines the studies of the bayonet fragment with severe damages of metal found in the city Kremenchuk (Ukraine) in one of the canals on the outskirts of the city, near the Dnipro River. Theoretical research to study blade weapons of the World War I period and the typology of the bayonets of that period, which made it possible to put forward an assumption about the possible identification of the object as a modified bayonet to the Mauser rifle has been carried out. Metal science expert examination was based on X-ray fluorescence spectrometry to determine the concentration of elements in the sample from the cleaned part of the blade. Analysis of the chemical composition showed that the blade was made of hardened carbon steel alloyed with silicon, chromium, manganese, nickel and copper. Measure results of the chemical composition of the object correspond to steel for castings of grade 55L with an average blade hardness of 42 HRC. Manufacturing technology of the casting corresponds to the end of the XIX – the beginning of the XX century with the use of converter production. The bayonet blade was subjected to strengthening heat treatment in the form of hardening and medium tempering. Metallographic analysis showed that the research object of blade fragment suffered corrosion cracking between crystals or along the body of grains, indicating a long stay in silty deposits. The identification of the research object has been carried out using applied technologies based on visual inspection with a description of the state of conservation and comparison with the results reflected in scientific periodicals; metal science expertise; determination of weight and size characteristics and their compliance with the original, including experimental reconstruction, which identifies the preserved fragment with the original drawing at the control points. A comparison of the chemical composition of the blade steel and the “Haenel” steel, differing in concentration and additional alloying elements has been made. The remains of the royal monogram imprint of the stamp and the absence of the regimental stamp have become the basis for searching through catalogs of registered bayonets. This allowed the identification of the object under study as part of the German imperial modified bayonet model 1898/1905 for the Mauser rifle, which was manufactured in the period from 1915 to 1918. Prospects for further research are seen in an increase in the number of metal science examinations for more accurate identification of discovered specimens.
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Alvarez, Pedro, Lexuri Vázquez, Noelia Ruiz, Pedro Rodríguez, Ana Magaña, Andrea Niklas und Fernando Santos. „Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing“. Metals 9, Nr. 9 (05.09.2019): 985. http://dx.doi.org/10.3390/met9090985.
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Reduced hot cracking susceptibility is essential to ensure the flawless manufacturing of nickel superalloys typically employed in welded aircraft engine structures. The hot cracking of precipitation strengthened alloy 718 mainly depends on chemical composition and microstructure resulting from the thermal story. Alloy 718 is usually welded in a solution annealed state. However, even with this thermal treatment, cracks can be induced during standard industrial manufacturing conditions, leading to costly and time-consuming reworking. In this work, the cracking susceptibility of wrought and investment casting alloy 718 is studied by the Varestraint test. The test is performed while applying different welding conditions, i.e., continuous tungsten inert gas (TIG), low frequency pulsed TIG, continuous laser beam welding (LBW) and pulsed LBW. Welding parameters are selected for each welding technology in order to meet the welding quality criteria requested for targeted aeronautical applications, that is, full penetration, minimum cross-sectional welding width and reduced overhang and underfill. Results show that the hot cracking susceptibility of LBW samples determined by the Varestraint test is enhanced due to extended center line hot cracking, resulting in a fish-bone like cracking pattern. On the contrary, the minor effect of material source (wrought or casting), grain size and pulsation is observed. In fact, casting samples with a 30 times coarser grain size have shown better performance than wrought material.
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YAMANAKA, Akihiro, Kazuo OKAMURA und Takashi KANAZAWA. „Mechanism of Internal Cracking in Continuous Casting“. Tetsu-to-Hagane 82, Nr. 12 (1996): 999–1004. http://dx.doi.org/10.2355/tetsutohagane1955.82.12_999.
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Klobčar, D., L. Kosec, B. Kosec und J. Tušek. „Thermo fatigue cracking of die casting dies“. Engineering Failure Analysis 20 (März 2012): 43–53. http://dx.doi.org/10.1016/j.engfailanal.2011.10.005.
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Pisarek, B. P., D. Kołakowski und T. Pacyniak. „Analysis of the Causes of Cracks in a Thick-Walled Bush Made of Die-Cast Aluminum Bronze“. Archives of Foundry Engineering 16, Nr. 4 (01.12.2016): 119–24. http://dx.doi.org/10.1515/afe-2016-0095.
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Abstract For the die casting conditions of aluminium bronzes assumed based on the literature data, a thick-walled bush was cast, made of complex aluminium bronze (Cu-Al-Fe-Ni-Cr). After the cast was removed from the mould, cracks were observed inside it. In order to identify the stage in the technological production process at which, potentially, the formation of stresses damaging the continuity of the microstructure created in the cast was possible (hot cracking and/or cold cracking), a computer simulation was performed. The article presents the results of the computer simulation of the process of casting the material into the gravity die as well as solidifying and cooling of the cast in the shape of a thick-walled bush. The simulation was performed with the use of the MAGMA5 program and by application of the CuAl10Ni5,5Fe4,5 alloy from the MAGMA5 program database. The results were compared with the location of the defects identified in the actual cast. As a result of the simulation of the die-casting process of this bush, potential regions were identified where significant principal stresses accumulate, which can cause local hot and cold cracking. Until now, no research has been made of die-cast aluminium bronzes with a Cr addition. Correlating the results of the computer simulation validated by the analysis of the actual cast made it possible to clearly determine the critical regions in the cast exposed to cracking and point to the causes of its occurrence. Proposals of changes in the bush die casting process were elaborated, in order to avoid hot tearing and cold cracking. The article discusses the results of preliminary tests being a prologue to the optimization of the die-casting process parameters of complex aluminium bronze thick-walled bushs.
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Lalpoor, Mehdi, Dmitry G. Eskin, Hallvard Gustav Fjær, Andreas Ten Cate, Nick Ontijt und Laurens Katgerman. „Application of a Criterion for Cold Cracking to Casting High Strength Aluminium Alloys“. Materials Science Forum 654-656 (Juni 2010): 1432–35. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1432.
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Direct chill (DC) casting of high strength 7xxx series aluminum alloys is difficult mainly due to solidification cracking (hot cracks) and solid state cracking (cold cracks). Poor thermal properties along with extreme brittleness in the as-cast condition make DC-casting of such alloys a challenging process. Therefore, a criterion that can predict the catastrophic failure and cold cracking of the ingots would be highly beneficial to the aluminum industry. The already established criteria are dealing with the maximum principal stress component in the ingot and the plane strain fracture toughness (KIc) of the alloy under discussion. In this research work such a criterion was applied to a typical 7xxx series alloy which is highly prone to cold cracking. The mechanical properties, constitutive parameters, as well as the KIc values of the alloy were determined experimentally in the genuine as-cast condition and used as input data for the finite element package ALSIM5. Thermomechanical simulations were run for billets of various diameters and the state of residual thermal stresses was determined. Following the contour maps of the critical crack size gained from the model, the casting conditions were optimized to produce a crack-free billet.