Showing papers on "Spray forming published in 1997"

Modeling of porosity during spray forming

Abstract: The effects of processing parameters on porosity in spray formed materials are investigated in the present paper using a recently developed porosity model. The calculated results showed that processing parameters such as melt superheat, deposition distance, atomization pressure and melt flow rate all have significant influence on the level of porosity. The variations of porosity with these parameters consistently exhibit distinctive V-shapes. When the low porosity is considered the main criterion to characterize the quality of a deposited material, corresponding optimal processing parameters can be determined based on the calculated results. Such processing parameter combinations are not unique, however, the other constraints, such as economical and microstructural issues, should be taken into consideration as well.

Spray Forming of Magnesium Alloys and Composites

Abstract: Rapid solidification can play an important role in the development of high performance magnesium alloys and composites. The investigation reported concentrate don spray forming of magnesium alloys ...

Solid-state spray forming of aluminum near-net shapes

Abstract: The next steps in developing SSF will require sufficient funding to produce samples with the suggested refinements and evaluate these samples. The steps include developing a proprietary auxiliary process that renders the annealing step unnecessary and allows for the direct use of the near-net shape in the assprayed condition, investigating specially prepared strengthening phase powders that better match the mechanical impedance of aluminum for producting near-net-shape aluminum MMC, using heated air as an accelerating gas, and conducting additional mechanical tests of aluminum and aluminum MMC to determine material properties.

Microstructural control by spray forming and wear characteristics of a Babbit alloy

Abstract: The effect of process variables during spray forming of a commercial Babbit alloy containing Pb74–Sn12–Sb11.5–Cu1.25–NiO.75–Cd0.3–As0.2 on its microstructure and wear characteristics were investigated. Variation in atomization gas pressure from 0.6 to 1.2 MPa and nozzle to substrate distance from 0.2 to 0.4 m revealed considerable change in the nature of porosity and microstructural features of the spray deposits. The process variables during spray deposition were optimized to achieve microstructural homogeneity and refinement in second phase particles of this alloy. The wear study of both the spray formed and as-cast alloy under an applied load of 10 to 70 N and sliding velocity of 0.2 to 1.5 ms-1 indicated two distinct regimes of mild and severe wear. In both the regimes, the spray-formed alloy consistently indicated a low wear rate compared to that of the as-cast alloy. In addition, the mild wear regime of the spray-formed alloy was extended to higher load and sliding velocity. Wear characteristics of the spray formed alloy is discussed in light of its microstructural features induced during spray deposition processing.

Modeling and microstructure development in spray forming

Abstract: Models of the spray forming process from different groups show reasonable agreement with each other and with the real process. Use of these models has provided considerable insight into the several complex processes involved in spray forming; in addition, the models allow designed experiments to provide further insight into the process. In the work described it has been shown that the modeled fraction of liquid in the spray f j (s) appears to be an appropriate control parameter for spray forming. Sticking efficiency and porosity have been found to correlate well with f j(S) . The differences found in the optimum value of the fraction of liquid in the spray for billets (0.3) and tubes(0.5-0.6) indicate, however, that the actual control parameter may be the fraction liquid in the deposit, f j (d) on the surface under the spray. The need for improved modeling, particularly of the full thermal profiles in complex geometries such as spray deposited tubes, is discussed as is the value of improved process diagnostic tools for direct experimental measurement of such features as droplet sizes and velocities, and the deposit temperatures in actual spray forming processes.

Thermal Modeling of Deposit Solidification in Uniform Droplet Spray Forming

Abstract: In spray forming, the deposit thermal state is a key parameter which influences the microstructural evolution upon and after droplet impact onto the deposit. The uniform droplet spray (UDS) forming process has been developed to enable precise control of the droplet and deposit thermal state and the resultant material microstructure. By having a uniform droplet size throughout the spray, all the droplets deposited onto the substrate will have the same thermal state upon impact, allowing for precise control of the solidification process. This paper describes a one-dimensional, finite difference model that predicts the temperature and liquid fraction of the deposit during the UDS process. The model employs an explicit temperature-enthalpy method to incorporate a variety of solidification models. Experiments were conducted using Sn-15 wt percent Pb binary alloy. Temperatures were measured in the deposit and acceptable agreement with the simulation was obtained. Modeling has shown that the deposit thermal state is highly dependent on variations in spray conditions, which are predicted using droplet trajectory and droplet thermal models. Using the droplet and deposit models, the relationship between UDS process parameters and material microstructure can be understood.

Particle penetration during spray forming and Co-injection of Ni3Al + B/Al2O3 intermetallic matrix composite

Abstract: Intermetallic matrix Ni3Al + B/Al2O3 composite, with 11 vol pct of Al2O3 particles incorporated into the matrix, was synthesized using a spray atomization and coinjection method The penetration behavior of ceramic particles into atomized droplets during spray atomization and coinjection of Ni3Al + B/Al2O3 composite was investigated experimentally and numerically It was found that the extent of incorporation of Al2O3 into Ni3Al + B droplets depends on the solidification condition of the droplets at the time of droplet/particle interaction Penetration was observed only in fully liquid droplets or partially solidified droplets No penetration was observed for droplets smaller than ∼40 µm, because droplets in this size range were fully solidified at the point of coinjection, and penetration was not possible for fully solidified droplets The distribution of penetrated Al2O3 in the Ni3Al + B droplets was, in general, uniform, with no trends of segregation observed However, it was noted that most Al2O3 particles were located at the grain boundaries inside the droplets, while some Al2O3 particles were trapped inside the droplets by primary dendrite arms resulting from a fast moving solidification front typically associated with rapid solidification processes such as spray atomization Finally, it was believed that the Al2O3 particles facilitated nucleation upon penetration of the Ni3Al + B droplets either by means of thermal gradients or compatibility of preferred growth planes

Aluminum alloy impeller and manufacturing method of the same

Abstract: There is disclosed a high heat resistant aluminum alloy impeller, which is suitably used as an impeller, especially for a centrifugal compressor, and for the rotor and the blade of a turbo molecular pump or the scroll of a scroll compressor. Also, a method for manufacturing this aluminum alloy impeller is disclosed. The impeller is composed of an Al--Fe rapid solidification aluminum alloy, which is produced by a spray forming process for spraying a molten metal with inert gas and rapidly solidifying the metal at a cooling speed of 10 2 ° C./sec. or higher while simultaneously deposing the metal. The rapid solidification aluminum alloy is subjected to hot extrusion processing within a temperature range of 200° C. to 600° C. and further subjected to hot forging.

Modelling microstructural development in spray forming : experimental verification

Abstract: Experiments to determine the sticking efficiency of droplets in spray forming and the as cast porosity in two different spray formed geometries (tubes and billets) have been carried out in two alloys, guided by modelling of different aspects of spray forming. Two major results were found. For a given geometry a single parameter, the liquid fraction f 1 in the spray appears to control the process, independent of the alloy used. For billets the highest sticking efficiencies were obtained at f 1 of about 0·3 and the deposits made with this liquid fraction, and higher, had minimum porosity. Second, this optimum value of f 1 was found to increase, however, to about 0·55–0·6 for tubes. It is argued that this distinction between the geometries arose since f 1 on the top surface of the deposit was significantly lower for the tube geometry than for the billet geometry. This result suggests that the critical control parameter is actually the liquid fraction on the deposit surface. It was also found that the...

Physical Properties of Alloys Relevant to Spray Forming

Abstract: Experimental methods have been developed for the measurement of the physical properties of commercial alloys needed for the mathematical modelling of high temperature processes such as spray forming and atomisation PM/0756

Manufacturing clad products by spray forming

Abstract: Whilst it has been feasible to spray form clad products for several years, it has been difficult to generate a high integrity metallurgical bond at the interface of the mandrel and the sprayed alloy. Consequently, roll preforms have generally been produced in the form of rings which are subsequently fitted to the roll arbor or mandrel. However, a joint project in progress between Forged Rolls (UK) Ltd, British Rollmakers Corporation, Osprey Metals Ltd and Sheffield University (with part funding from the UK, Department of Trade and Industry, under the LINK enhanced engineering materials programme) has demonstrated that direct bonding of roll alloys onto steel arbors can be achieved using arbor preheating in conjunction with multi-atomisers and other special techniques. The equipment to achieve such results is described, together with an outline of the deposition method. Initial metallographic and mechanical property results are also presented with a comparison made between conventionally processed and spray formed roll alloys, where a considerable refinement in the spray formed microstructure is apparent. These encouraging results have led to the spray forming of narrow, clad hot and cold strip mill rolls for actual field trials.

Stand der Technik beim Sprühkompaktieren von Bolzen

Abstract: The spray forming process has to be categorized between the traditional metallurgical processes of casting and sintering as well as gaining from coating processes as plasma and flame spraying. Using adequate process parameters, poor recristallization conditions guarantee fine grained isotropic materials, free of macrosegregations. On behalf of the production of billets, which now is an industrial scale production process of spray forming, advantages of the stationary in comparison with problems arising from the non-stationary spray process will be discussed and illustrated by malformations resulting from non-suitable process parameters.

Spray forming large diameter special steel billets

Abstract: This project is of four years duration and is carried out with the financial aid of the European Coal and Steel Community. It has the fundamental aim of demonstrating the applicability of spray forming as a viable process for industrial scale steel production. The Osprey process has potential for the production of billets in special steels. However, earlier studies had shown that the technology was not developed sufficiently to permit production on an industrial scale. This was because of an absence of the understanding of the process control required for large billets. The objective of the project has been to extend the technology of spray forming steel in the horizontal mode to produce billets up to 400mm diameter and by up to 1200kg in weight. Work conducted within the project is described including the construction of the demonstration plant, commissioning, process development, evaluation and extension of the process from the initial trials on D2 steel to other materials.

Atomizer for spray forming ring structures

Abstract: A method and spray forming system for effectively spraying the inner diameters of intricate objects and makes inner diameter spray forming practical for articles that have various and complicated inner geometries. The spray forming system can include at least one of a rotating mandrel and preform, and atomizer, which is fed with liquid metal, to form a spray. The atomizer is positioned with respect to inner walls of at least one of the rotating mandrel and preform to accurately and fully spray form an inner diameter of an article, even if the article has complicated and irregular inner surfaces.

Spray forming of Zircaloy-4

Abstract: Zircaloy-4 was spray formed using an induction skull melting/spray atomization and deposition unit. The microstructure and phase composition of the spray formed Zircaloy-4 bulk materials and oversprayed Zircaloy-4 powders were investigated. The microstructure of the spray formed Zircaloy-4 bulk materials was found to be Widmanstatten α plates precipitated out from equiaxed β grains, with evident microstructure refinement in terms of the sizes corresponding to equiaxed β phase grains and the α plates, respectively. The microstructure of oversprayed Zircaloy-4 powders was also revealed to be Widmanstatten α plates precipitated out from equiaxed β grains, in contrast with the dendritic structure generally reported for oversprayed powders. These microstructure characteristics were discussed in light of the thermal history experienced by the powders and the deposit. Finally, the density and hardness of spray formed Zircaloy-4 were also characterized, indicating that spray forming had little effect on these properties for Zircaloy-4 studied herein.

Modelling of droplet behaviour during spray forming using fluent

Abstract: A control volume based fluid dynamics software program, FLUENT, has been used to model the 2-dimensional dynamic and thermal behaviour of Udimet 720 droplets during gas atomization and spray forming. The effect of atomizing gas pressure, spray distance and melt mass flow rate (MFR) on the equilibrated droplet spray temperature has been examined and the predictions compared with measured maximum deposit temperatures from spray forming experiments performed under the same process conditions. The predicted spray temperatures at the substrate were consistently higher than the measured deposit temperatures, and in both cases increased with: (i) decreasing gas pressure; (ii) decreasing spray distance; and (iii) increasing MFR. Individual droplet temperatures and velocities were found to be strongly dependent on droplet size with droplet temperature decreasing and mean droplet axial velocities increasing with decreasing droplet size.

Shape detecting roll

Abstract: PURPOSE: To provide a shape detecting roll capable of surely preventing sticking of foreign substance under an adverse condition where much foreign substance is generated and apt to be firmly stuck CONSTITUTION: A shaft 27 of a split roll 26 comprising a shape detecting roll 21 is fitted to a steel core 28 A plurality of load cells 30 are attached on the steel core 28, and a cylindrical sleeve 31 is fitted to the outside of the steel core 28 The load cells 30 are brought into contact with an inner circumferential part of the sleeve 31, ad a thermal spray coating layer 32 is formed on the outer circumferential part of the sleeve 31 by the spray forming The surface of the thermal spray coating layer 32 is ground flat by a grinding wheel or a rotary abrasive grain belt The chromium spray coating material is preferably used as a spray coating material to form the thermal spray coating layer 32 In particular, it is more preferable to use the chromium spray coating material mainly consisting of chromium carbide or chromium oxide

Clean Metal Spray Forming

Abstract: Clean Metal Spray Forming (CMSF) is a new process in which the melt pool from an Electroslag Refining (ESR) furnace is used as the source for a liquid metal stream to be directly processed via spray forming. The process takes advantage of the refining function of the ESR process and the economy of the spray forming process to yield material that is oxide-free, tinegrained, equiaxed, homogeneous, and thus acceptable for fatigue-life critical applications. The controlled transfer of liquid metal from the ESR pool to the spray forming system is performed using a ceramic-free cold-walled-induction guide, which is a segmented induction heated copper funnel. A pilot plant for development of the concept using nickel-based alloys has been constructed and is operational. Oxide cleanliness, microstructure, and mechanical properties of Alloy 718 processed through the system will be discussed. Introduction Ceramic inclusions play a significant role in the low-cycle-fatigue life of components made from superalloys [ 1,2]. Mechanistically, a ceramic inclusion is more brittle than surrounding metal and will crack early in life, possibly as early as the first loading cycle. The cracked inclusion acts as a crack starter for the surrounding metal and may lead to early fatigue failure. Since a large fraction of the fatigue life of any part occurs while cracks are short, it is important to eliminate or limit the size of the ceramic inclusions. This requirement poses a metals processing challenge that has been aggressively attacked in the cast & wrought industry and in the powder metallurgy industry. In the cast & wrought industry, a high level of cleanliness is achieved using a triple melt procedure in which Vacuum Induction Melting (VIM) is used to achieve composition, Electroslag Refining (ESR) is used to achieve cleanliness [3], and Vacuum Arc Remelting (VAR) is used to achieve microstructure and homogeneity. In the powder metallurgy industry, cleanliness is achieved by sieving the powder, and through careful handling during subsequent canning, vacuum degassing, and extrusion. The primary oxide removing process in cast & wrought processing is the ESR step and the primary oxide removing step in powder metallurgy is the sieve step. Superalloys 7X3,625,706 and Various Derivatives Edited by E.A. Loria The Minerals, Metals &Materials Society, 1997

Sprühkompaktieren von unlegiertem Stahl

Abstract: Spray forming as a primary shaping process has found its entrance from the research state into the industrial production line. Due to its advantages, that means the short way from melting to the formed product and the quality of the microstructure, the method is established in many applications. Nevertheless, for steel application this step is still missing. The paper therefore gives an overview of the state of research in spray forming of steel. The work was part of a special research program of the German Research Foundation (DFG) at the University of Bremen and several institutes. The influence of process parameters on the primary structure of unalloyed steels is presented. Principles of shaping, influencing the microstructure and metal forming in combination with spray forming are shown. The results point to the potential of spray forming to produce complex parts, even of higher alloyed steels.

Manufacture of engine block for internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To provide a method of forming an engine block cylinder bore line which is light-weighted, wear-resisting and hard to be hurted and forming the line in an internal combustion engine SOLUTION: An engine block 21 having a cylinder block is machined, a spray-forming cylinder liner is formed with a designated inside diameter and with a designated outline, the cylinder block is heated, a cylinder liner 10 is inserted in a bore 12, and the cylinder block is cooled in such a manner that the liner 10 is fixed to a suitable place in the bore 12 by the compressive force The spray forming liner is a cylindrical body which is formed by a material having designated thermal characteristics and resistance to the generation of abrasion and flaw The cylindrical body has an outside surface formed by spray forming and an inside surface formed by spray forming The liner can be formed as a single spray forming layer or a multi-spray forming layer using different materials

Sensitivity Study on Effects of Process Parameters on Spray Forming Pb—35Sn Alloy

Abstract: The effects of atomisation gas pressure (0·1–0·2 MPa), flight distance (25–45 cm), and spray temperature (300–400°C) on the density and microstructure of Pb–35Sn deposits have been studied. As spray deposited microstructure showed equiaxed primary Pb phase, while as cast showed dendritic morphology. Atomisation gas pressure was found to have a significant effect on the size of primary phase, whereas flight distance and spray temperature had only limited effects. Atomisation gas pressure also had a greater effect on the fraction of primary phase produced and on the density of deposits than spray temperature and flight distance. The effect of flight distance is small because of the confounding influence of atomization gas pressure. The effects of gas impinging angle (45 and 90°) were mixed. Within the range of experimental variables studied, the volume fraction of primary phase increased with cooling rate for spray deposited materials, but decreased as the cooling rate increased for stirred cast mat...