Papers by Keyword: Casting

Abstract: The influence of applying an external distributed pressure along the upper surface of the molten metal (Aluminum ) during the solidification process on the temperature reduction profile was studied including the time of solidification of the cast and the phase change moving boundary location for two mould wall thicknesses (10mm and 15mm). A 3D model was built up by Solidworks and simulated by ANSYS FLUENT; each mould wall thickness was discussed for two press cases (1bar and 3bar) sequentially, comparing with no press cases. The discussion includes the ambient temperature effect, which is taken (300K then 310K), the overall cases that studied was 7 cases. The study shows a remarkable effect of press on the temperature reduction profile especially when mix with the mould thickness effect as well as the ambient temperature which has a great order in guiding the results. The results showed that the heat reduction increases by increasing the mould thickness as well as the applied pressure. Moreover, this effect will reduce the solidification time and the moving of the boundary of phase change become faster in appearance.

Abstract: The article presents a method for eliminating the crystallization of thermal nodes and shrinkage defects in the form of micro-friable cavities. The method of soldering on castings from steel grades VNL-1 and VNL-6 using 5VA powder solder has been investigated. Also, the optimal soldering modes were determined, the effects of soldering modes on the properties of the base material and the soldered joint were studied, the corrosion resistance was investigated, the corrosion resistance of the soldered joints in corrosive environments. The conducted studies of sealing by soldering cast parts with microdefects lead to the following results: increased corrosion resistance; ensuring increased tightness; improving the presentation; elimination of surface microdefects.

Abstract: One of steel 08H14N5M2DL scopes in the industry is an aircraft industry, to be exact, production of racks of the chassis for airplanes and helicopters which test cyclic types of loadings (take-off/landing). Despite the margin of safety which is put at the design of the aircraft, an important role plays, both quality of the material and its ability to save the mechanical properties during all assigned resource for the aircraft. Therefore the development of necessary conditions of production of steel under which the highest mechanical properties and also the ability to save them on the maximum period will be received becomes relevant and today. Work purpose: Identification and prevention of the most significant negative factors having an impact on mechanical properties of steel 08H14N5M2DL in the course of its receiving. In the work, 257 melting of steel of VNL-3 brand in the open IST-0.16 induction furnace with lining from a ground, magnesite brick is investigated. Methods of research are control of the content of austenite and existence of δ - ferrite in structure there were by measurement of values of a magnetic flux density cold and hot tests on the IFSS-1 device and also calculations of the number of products of wear, the solubility of nitrogen in steel VNL-3 and saturation nitrogen. It is revealed that negative impact on mechanical properties of VNL steel – 3 is rendered by nonmetallic inclusions, the maintenance of δ-ferrite and nitrogen. It is established that for stabilization of mechanical properties of steel, aging temperature after tempering in 500 °C allows to support and save steady indicators of mechanical properties. The fact that δ the ferrite exception of solid steel will allow reducing the oxygen content in it not less, than for 0.019% is confirmed owing to what iron crystallizes in γ-phase, passing δ-modification. The presented results confirm prospects of the developed approach in receiving the high-quality steel intended for use in the aviation industry.

Abstract: The effect of fabrication methods on polysiloxane (POS) composites were studied by analysing both method of casting (CA) and compression (CO). The POS composites were reinforced with 2-12 wt% of natural derived silica from rice husk (RHA SiO₂) as a filler which incinerated at 700°C. The composites behaviour were analysed through tensile testing (ASTM D412). Through comparison study on both CA and CO composites’s tensile behaviour it shows that both composites strength keep increasing with 2wt% - 10wt% RHA SiO₂ addition but strength decreased at 12wt% due to agglomeration of RHA SiO₂. Moreover, it was found that the tensile strength of CO composites had offer 23.56% higher compared to CA composites. The difference were influenced by the distribution of RHA SiO₂ as filler. The surface morphology of CO composites had showed that the most of RHA SiO₂ were embedded and less agglomeration, compared to CA composites that had lots of agglomeration which lead to higher tendency of crack propagation. The arrangement of filler due to the CO method that helps RHA SiO₂ to distributed homogenously and embedded in a matrix of POS to avoid agglomeration and lead better adhesion respectively. Thus, CO method had potential to offer in enhancing tensile behaviour compared to CA method by influencing filler distribution arrangement for vibration absorber application.

Abstract: Aluminum is widely used in various industries in the form of alloys due to its unique properties - lightness, high electrical conductivity, and corrosion resistance. However, when casting alloys, various defects arise, the main of which are nonconformities of the ingot chemical composition, mechanical properties, and internal structure. The RUSAL Bratsk PJSC (, Irkutsk Region) aluminum alloy samples have been examined for pores, cracks, and oxide films. The causes of their occurrence have been analyzed and ways to eliminate these defects proposed. It has been found that, with increasing hydrogen content in the melt, micro-porosity leads to friability and macro-porosity of the alloy structure. According to the study results, the likelihood of cracks in the ingots could be reduced by evenly decreased metal temperature and casting velocity. The oxide film defects have been eliminated by feeding metal into the mold in a steady turbulence-free manner, increasing the metal settling time in a mixer, and reducing the alloy preparation time in a furnace.

Abstract: Manufacturing of thick seamless pipes of age-hardenable aluminum alloys are a specialized technology since their application is limited to specific hi-tech areas. Quality criteria for their inspection are propriety items of the very few production facilities that develop these criteria in-house. Present study relates ultrasonic signals reflecting back from non-continuities in the thickness of seamless pipes with their microstructural features. Detailed study of defects leads to the source of their formation and will ultimately help to systematically control them. Signals from ultrasonic testing trace defects as UT waves reflect back from discontinuities in the material. Defective sections of seamless pipes were cut with precision to reveal the defects. The sectioned surfaces were subjected to metallographic preparation and revealed defects were studied using Optical and Field Emission Scanning Electron Microscopes (FESEM). Defects are grouped based on the shape of UT signals as well as the defect morphology as revealed by microscopic studies. Most of the observed cracks are found to grow in the direction of extrusion. Energy Dispersive Spectroscopy (EDS) analysis was conducted to determine the composition of inclusions in the vicinity of the defects. Data from elemental analysis is used to identify the potential sources. The study recommends measures to control the defects and improve the yield.

Abstract: Linear segregation of high strength aluminum alloy ZL205A castings were studied by X-ray Nondestructive testing, scanning electron microscope and energy dispersive spectrometer. It is found that the linear segregation occurs at the large wall thickness of the casting and/or at the place where the wall thickness is in transition. Segregation element is mainly Cu, which exists as compound θ (Al₂Cu) phase. The formation of linear segregation is related to the flow of Cu-rich melt in the late solidification period, while the occurrence of thermal cracks promotes the formation of linear segregation. The formation of linear segregation of the casting can be effectively prevented by eliminating hot spots of the casting, refining crystal grains and increasing solidification speed of the casting.

Abstract: A 2-D finite volume Computational Fluid Dynamic (CFD) model, using Ansys Fluent vR.1 of a vertically oriented upwards continuous casting (VUCC), was investigated for 8 mm, oxygen free copper (OFCu). The simulations enabled the mapping of the cast OFCu solidification front (SF) interface from liquid to solid. Optimisation of the simulation parameters were investigated which included mesh size and the Ansys specific ‘mushy zone’ constant (A_mush), which is used to account for fluid flow dampening at SF within the model. Observations of the SF, the change in fluid volume in the die, the simulation convergence and the total simulation time, revealed that the optimised casting parameters were for mesh size 1×10^-4 m and A_mush 10⁶ kg/m³s. These parameters were compared with the cast rod and highlighted qualitatively the relationship between grain growth direction and SF position during a casting pulse cycle.

Abstract: The aim of this work was to analyse the microstructural nature of plasticity in ZnAl4Cu1 alloy and its dependence on the processing technology. The alloy condition was analysed after gravity casting, after forging and after ECAP processing. Two alloys with slightly different compositions were studied. For alloy A, the returnable material from a prominent Zn alloy producer was used. For B alloy input raw materials of relatively high purity were used. Tensile testing showed that in the as-cast alloy tensile strength had relatively low levels up to 211 MPa, and particularly low values of ductility only up to 2.5 % were found in B alloy, which was more polluted. By means of ECAP processing of the as-cast alloy, the tensile strength was improved by 50 % (Rm = 312 MPa). In the case of the purer A alloy the majority of samples improved to level A = 27.9 %. Forging of the as-cast alloy preserved strength on a level similar to the ECAP result, but ductility was improved to the level of 34.4 %, although alloy B had lower purity. Further significant ductility improvement was obtained through ECAP processing to A = 147 % of the as-forged alloy. The microstructure of ZnAl4Cu1 consists primarily of segregated η phase (rich in Zn) and fine eutectoid composed of η and alpha phases segregated mostly in dispersive state, but in places also in lamellar form. Close correlation between microstructure and processing method resulted from our fractographic study. In the case of ECAP processing of the forged state the finest microstructure was achieved, which was accompanied by higher plasticity and also by fine dimples of transcrystalline ductile fracture (DTDF).

Abstract: Frozen mold casting uses a casting mold in which only water is added as a binder to sand, and the mixture is kneaded, frozen, and solidified. This method can offer the same level of mold strength and productivity as conventional methods, while maintaining a low environmental impact in terms of resource utilization and ensuring pollution-free processing. We studied the simultaneous fabrication of multiple aluminum alloy castings using a frozen mold. No defects associated with the collapse of the mold due to the molten metal heat were found. No entrainment of sand was observed on the surface of the samples.