共查询到20条相似文献,搜索用时 62 毫秒
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《International Journal of Cast Metals Research》2013,26(6):401-407
AbstractAir that becomes entrapped in the molten metal during the die casting process has a major effect on the formation of porosity in horizontal cold chamber die castings. In this study, a three-dimensional computational fluid dynamics model was developed to study the flow patterns of liquid metal in the injection chamber, in which the moving boundary conditions of the plunger movement was considered in detail. According to the principle of die casting machines, a water analogue system was designed and built to investigate the slow shot process. A colour high speed camera was used to record the fluid flow patterns under different plunger movement profiles. The numerical simulation results agreed well with the water analogue experimental results, which validated the numerical model of shot processing in the cold chamber of the die casting process. 相似文献
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压室液态金属流动耦合温度场三维数值模拟 总被引:3,自引:0,他引:3
压铸过程中,压室内液态金属卷入的气体是影响铸件质量的原因之一.针对压室压射过程,引入冲头的移动规律以及流动过程中热量传递的计算,实现并开发了压室压射过程的流场耦合温度场的数值模拟程序.采用所开发的模拟程序对压室金属流动及传热过程进行了模拟,模拟结果与FLOW-3D的计算结果以及临界速度理论作比较,两者均吻合.采用压室模拟能够优化冲头的运动规律,使卷气最小. 相似文献
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《International Journal of Cast Metals Research》2013,26(4):246-249
AbstractThe quality of hot chamber die cast aluminium alloys can vary, due to differences of casting conditions, in particular the casting pressure. This is caused by the plunger tip galling during the casting process. To solve this problem, a new injection system is proposed using a flexible movable plunger tip and an insert type shot sleeve. With this system, the plunger tip can be turned around and slid into the piston holder, which facilitates smooth insertion of the plunger into the shot sleeve. The proposed insert type sleeve can be made with a strong structure. Moreover, even if the sleeve is partially fractured, it can easily be replaced. With the proposed injection system, high quality hot chamber die cast components can be created. In addition, the maintenance cost of the injection system is dramatically reduced. 相似文献
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The objective of this paper is to analyse a plunger acceleration law that is expected to minimize air entrapment in the slow shot phase of pressure die casting in horizontal cold chambers, and thus to reduce porosity in manufactured parts. The study is carried out using results from an analytical model of the flow of molten metal in the shot sleeve, which is based on the shallow-water approximation, and whose predicted optimum acceleration parameters are in good agreement with available experimental results. The results for the surface profiles of the wave formed during plunger movement using plunger acceleration laws which are typically used in pressure die casting are compared with those corresponding to the proposed law. Some analytical predictions for the wave profiles and for the mass of trapped air are compared with numerical results obtained from a finite-element code, which solves momentum and mass conservation equations. The limiting values of the initial filling fraction required for appropriate operating conditions are determined for wide ranges of acceleration parameters and pouring hole locations. 相似文献
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Laihua Wang Thang Nguyen Gary Savage Cameron Davidson 《International Journal of Cast Metals Research》2013,26(4):409-417
Air entrapment and premature solidification in the shot sleeve of the cold chamber high pressure die casting process are problems affecting the casting quality. These issues are addressed from several viewpoints, including heat loss during metal ladling, turbulence generation and gas escape during pouring, wave formation and propagation during metal pouring and injection, and heat loss and solid creation in the shot sleeve during metal injection. Measurements and simulations have been conducted for a typical industrial case where the fill ratio of the shot sleeve is about 30%. It has been found that the settling time of the aluminium alloy in the shot sleeve has a profound influence on the air entrapment. The settling time also has a negative effect on the metal quality the solid formation (premature solidification or cold flakes) in the shot sleeve. Fast pouring and quick injection (no settling time) are recommended as a good approach to minimise the air entrapment and cold flakes in the shot sleeve in this particular case. IJCMR/474 相似文献
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袁有录 《特种铸造及有色合金》2007,27(6):436-438
在普通压铸流场模拟的基础上,通过建立冲头、压室及金属液之间的运动学与动力学控制方程,以及三者之间的边界条件与初始条件,模拟了压室内金属液在冲头推动下的二维流动形态.分析了冲头的不同运动参数对压室内金属液卷气的影响,为实际压铸中慢压射速度的选择提供了参考. 相似文献
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《International Journal of Cast Metals Research》2013,26(1-4):299-303
AbstractThe vacuum analysis algorithm was developed to simulate the total system of high pressure die casting process including vacuum vent, cavity and plunger area. The various vacuum degrees (760, 650, 500, 250 and 60 mmHg) were artificially applied in cavity. The filling behaviours of molten metal under the applied vacuum conditions were simulated and compared with those of experiment. The filling amount in cavity was increased with the increase of applied vacuum pressure during partial shot experiments. The simulated filling behaviours of molten metal were relatively well agreed with those of experiment. Through the results of fluid flow simulation, the relationship of filling length and filling velocity with the variation of vacuum pressure was analysed respectively. And it applied to a real die casting product and the internal gas quantity of product was significantly reduced by modification of vacuum gate system. 相似文献
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《International Journal of Cast Metals Research》2013,26(5):339-348
AbstractAlthough hot chamber diecasting is an appropriate technology for producing high quality cast components, there are material limitations; at the process temperature, aluminium alloy erodes the immersed steel shot sleeve and plunger. Attempts have been made to employ a Si3N4 ceramic in place of steel. High quality Al hot chamber diecast components can be manufactured in this manner, but long production runs are not possible because failures occur in the ceramic sleeve even after, for example, a few thousand shots. The fracture in the ceramic sleeve is caused by high stresses arising from the plunger galling the sleeve surface owing to penetration of the Al alloy into the gap between the sleeve and plunger. The infiltrated Al alloy has been found to react chemically with the ceramics; silicon in the ceramic reacts with iron particles present as inclusions in the Al alloy. Hence, the purity of the molten Al alloy in the crucible is a significant factor in the production of high quality diecast components. To prevent penetration of the Al alloy, the injection system is cleaned periodically using hydrochloric acid, which dissolves the infiltrated Al alloy. Since etching by HCl can reduce the strength of the ceramic parts, this cleaning process must also be reconsidered. Recommendations to improve the quality of hot chamber diecast Al components are proposed. 相似文献
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应用流体力学原理对液态金属在卧式冷室压铸机压室中的运动进行了理论分析和计算,阐明了冲头匀速运动和匀加速运动情况下波的运动情况和计算公式。据此分析认为:卧式冷室压铸机冲头的慢压射过程是加速运动和匀速运动的组合,组合的结果直接影响压铸件的质量。液态金属在压室卷入的空气量,与慢压射加速度、慢压射速度、起始充满度、压室直径有关,并存在一个临界慢压射速度和最佳加速度,在此速度和加速度下可使卷入的空气量最小,铸件气孔率最小。 相似文献
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The feasibility of semi-solid die casting of ADC12 aluminum alloy was studied. The effects of plunger speed, gate thickness, and solid fraction of the slurry on the defects were determined. The defects investigated are gas and shrinkage porosity. In the experiments, semi-solid slurry was prepared by the gas-induced semi-solid (GISS) technique. Then, the slurry was transferred to the shot sleeve and injected into the die. The die and shot sleeve temperatures were kept at 180 °C and 250 °C, respectively. The results show that the samples produced by the GISS die casting give little porosity, no blister and uniform microstructure. From all the results, it can be concluded that the GISS process is feasible to apply in the ADC12 aluminum die casting process. In addition, the GISS process can give improved properties such as decreased porosity and increased microstructure uniformity. 相似文献
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During the cold-chamber high pressure die casting(HPDC) process, samples were produced to investigate the microstructure characteristics of AM60B magnesium alloy. Special attention was paid to the effects of process parameters on the morphology and distribution of externally solidified crystals(ESCs) in the microstructure of magnesium alloy die castings, such as slow shot phase plunger velocity, delay time of pouring and fast shot phase plunger velocity. On the basis of metallographic observation and quantitative statistics, it is concluded that a lower slow shot phase plunger velocity and a longer delay time of pouring both lead to an increment of the size and percentage of the ESCs, due to the fact that a longer holding time of the melt in the shot sleeve will cause a more severe loss of the superheat. The impingement of the melt flow on the ESCs is more intensive with a higher fast shot phase plunger velocity, in such case the ESCs reveal a more granular and roundish morphology and are dispersed throughout the cross section of the castings. Based on analysis of the filling and solidification processes of the melt during the HPDC process, reasonable explanations were proposed in terms of the nucleation, growth, remelting and fragmentation of the ESCs to interpret the effects of process parameters on the morphology and distribution of the ESCs in the microstructure of magnesium alloy die castings. 相似文献
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H. B. Wu Z. T. Fan N. Y. Huang X. P. Dong X. F. Tian 《Journal of Materials Engineering and Performance》2005,14(1):132-135
The magnesium (Mg) alloy low-pressure expendable pattern casting (EPC) process is a newly developed casting technique combining
the advantages of both EPC and low-pressure casting. In this article, metal filling and the effect of the flow quantity of
inert gas on the filling rate in the low-pressure EPC process are investigated. The results showed that the molten Mg alloy
filled the mold cavity with a convex front laminar flow and the metal-filling rate increased significantly with increasing
flow quantity when flow quantity was below a critical value. However, once the flow quantity exceeded a critical value, the
filling rate increased slightly. The influence of the flow quantity of inert gas on melt-filling rate reveals that the mold
fill is controlled by flow quantity for a lower filling rate, and, subsequently, controlled by the evaporation of polystyrene
and the evaporation products for higher metal velocity. Meanwhile, the experimental results showed that the melt-filling rate
significantly affected the flow profile, and the filling procedure for the Mg alloy in the low-pressure EPC process. A slower
melt-filling rate could lead to misrun defects, whereas a higher filling rate results in folds, blisters, and porosity. The
optimized filling rate with Mg alloy casting is 140 to 170 mm/s in low-pressure EPC. 相似文献
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《International Journal of Cast Metals Research》2013,26(1-4):327-330
AbstractHigh pressure die casting (HPDC) experiments were conducted on a 650 t cold chamber die casting machine to study the interfacial heat transfer behaviour between casting and die. A 'step shape' casting and two commercial alloys namely ADC12 and AM50 were used during the experiments. Temperature and pressure measurements were made inside the die and at the die surface. The metal/die interfacial heat transfer coefficient (IHTC) was successfully determined based on the measured temperature inside the die by solving the inverse heat transfer problem. The IHTC was then used as the boundary condition to determine the 3-D temperature field inside the casting. Based on the predicted temperature distribution, the pressure distribution inside the casting was evaluated by assuming that the transferred pressure from the plunger tip of the injection side to the casting is primarily influenced by the solid fraction of the casting. Reasonable agreement was found between the determined pressure values and the measured pressures at the die surface of the casting. 相似文献