Papers by Keyword: Casting

Abstract: Magnesium alloys are one of the lightest structural metallic materials. Their specific strength and stiffness is comparable to this, characterizing aluminum alloys and even some groups of steel and titanium alloys. Their main disadvantage is low maximum working temperature (about 120°C for Mg-Al-Zn alloys). This led to development of Mg-RE-Zr alloys, which can work up to 250°C. The paper presents results of the investigations of influence of subsequent melting operations on the Elektron 21 and WE43 magnesium alloys. Elektron 21 alloy had been prepared from the pure ingots, while WE43 alloy from the scrap material. Average area of the grain flat section and eutectics volume fraction had been evaluated quantitatively. The results of the evaluation have been verified by means of Mann-Whitney U-Test and Kolmogorov-Smirnov statistical tests. The liquid metal treatment led to refinement of the grain only in Elektron 21 alloy (from Ᾱ=3559μm² to Ᾱ=1849 μm²). Multiple modification of the WE43 alloy does not lead to further decrease of the average area of grain flat section (from Ᾱ=1638μm² to Ᾱ=1871 μm²).

Abstract: Cast aluminium alloy 354 finds extensive applications in the automobile and aerospace industry due to its attractive combination of mechanical properties and excellent castability. A high fatigue strength value is desirable for these applications. The present study explores the possibility of improving the fatigue life of cast aluminium alloy by subjecting it to Hot Isostatic Pressing (commonly known as Hipping). A three parameter Weibull analysis of the fatigue test results was carried out for both Hipped and Non-Hipped samples. The Hipped samples showed an improved fatigue life compared to the Non-Hipped samples.

Abstract: This paper presents an overview and example using optimization techniques in casting numerical simulation. Most of the design work can fulfill with the software without human intervention. It really frees the engineer from the amount of trial-and-error that is necessary in traditional modeling.

Abstract: Composite castings exhibit high residual stresses, mainly because of different thermal expansion of the used materials. Similar to the in-cast cylinder liners in a motor block, a composite specimen, consisting of a steel insert and an aluminum cast surrounding, was analyzed by neutron diffraction. The temperature- and time-dependent change of lattice spacing and thus the strain evolution was investigated by in-situ experiments directly after casting and during the cooling of the part. Different cooling conditions were investigated using two different molds, namely a sand and a permanent (steel) mold, optimized for in-situ neutron diffraction.

Abstract: The objective of this work is to study the effect of antimony on as-cast microstructures and hardness of dual phase brassed. The studied compositions consisted of 56Cu-(42-X)Zn-1Si-0.5Al-0.5Sn-(X)Sb with varied antimony content in the range of 0.5-2.0 wt%. The alloys were prepared by melting pure elements using an induction furnace in graphite crucible at the temperature about 1,200 °C. The chemical composition of each alloy has been analyzed by X-ray fluorescence (XRF). Microstructures of the as-cast ingots were investigated by optical microscopy and scanning electron microscopy including the chemical analysis of the phase determined by X-ray energy dispersive spectroscopy (EDS). The obtained results suggested that the microstructures of as-cast ingots exhibited the beta-gamma dual phases. The beta phase was the matrix and the gamma phase extended along the grain boundary. The increase in antimony content increased the gamma phase and enhanced the hardness. Moreover, the antimony addition 2 wt% created the intermetallic compound (IMC) phase like a needle shape. The EDS analysis of IMC displayed 12.35 wt% antimony.

Abstract: The casting filling numerical simulation technology is of great significance to optimize the casting process, improve castings quality, and reduce production costs. Component wise splitting method only uses a small amount of iterations between velocity field and pressure field, so it has high computational efficiency in theory. The calculation accuracy is analyzed through Lid-driven cavity flow model, the result has a good agreement with literature results in low Reynolds number, but there is a big deviation when high Reynolds number. Finally the fraction step method is applied to the solution of the low pressure casting filling process, Calculation results coincided with the experimental results.

Abstract: In the article data about application nanopowder on a structure of coatings of the form are submitted at a casting of lead-tin bronzes. Elimination of gas porosity on a surface bronze cast preparations of high pressure compressors piston rings was the primary goal of such application protectively-dividing coverings. For experimental works mark of multicomponent bronze has been chosen. Its structure includes tin, lead, zinc and nickel. Casting from this bronze received a method of centrifugal molding. Influence of a structure of used protective - separating coating of a foundry core on a surface smoothness was probeed. Was compared action of coatings of a following composition: anti-burning-in coating (a blend of a low dispersible powder of chromium oxide with calcinated vegetable oil); anti-burning-in material ASPF-2/RgU (on the basis a low dispersible powder of graphite and the calcinated vegetable oil); the patent № 2297300 (blend of a ultradispersible powder of dioxide of zirconium with inpowderrial oil. Molding without use of coverings leads porosity depth to 4-5 mm and to a marriage significant amount (to 50 %). Use ASPF-2/RgU completely eliminates welding casting to a casting mold, but porosity on a surface remains. Application of coverings of a casting mold containing in quality of a filler ultradisperse powders oxide metals with low heat conductivity allows in to lower much a roughness and to eliminate gas porosity on a cast surface from lead-tin bronze. A gas time of a surface still remains, but them becomes much less and their form changes. Depth of defects doesn't exceed 1-1,5 mm that doesn't fall outside the limits the admission.

Abstract: In paper problem concerning inoculation of primary structure of Al with purity of 99,5% and 99,8% and AlSi2 alloy, which is realized mainly by intensification of liquid metal movement in mould is presented. In aim of realization of forced movement during the crystallization of liquid metal was used horizontal electromagnetic field produced by the induction coil (stirrer) supplied by current with elevated frequency. The degree of structure refinement was represented mainly by equiaxed crystals zone content on transverse section of ingot and average area of macro-grain in this zone. Effect of structure refinement obtained by influence of electromagnetic stirring was compared with refinement obtained by use of traditional inoculation, which consists in introducing of additives i.e. titanium, boron and strontium to metal bath. The results of studies and their analysis show possibility of effective refinement of pure Al and Al-Si alloy primary structure, only with use of horizontal electromagnetic field and without necessity of application of inoculants such a Ti and B. This method of inoculation is important, because inoculants decrease the degree of purity and electrical conductivity of pure Al. Moreover inoculants are reason of point cracks formation during rolling of ingots.

Abstract: 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.

Abstract: Free-surface phenomena play an important role in many engineering applications, such as filling process in casting, etching process and so on. As we know, level set kind method is more accurate than Volume of Fluid kind method. In this paper, we implement a hybrid lattice Boltzmann and particle level set method to simulate filling processes in a 2D cavity. Results obtained by the hybrid lattice Boltzmann and particle level set method show the same filling pattern with other methods in two different Reynolds numbers.