共查询到20条相似文献,搜索用时 312 毫秒
1.
2.
Tsung-Hsien Han Jer-Haur Kuo Weng-Sing Hwang 《Journal of Materials Engineering and Performance》2007,16(5):521-526
A mathematical model has been developed to simulate the flow pattern of molten metal and to predict the liquid-gas interface
shape in the shot sleeve of a cold chamber die casting machine during the injection stage. The flow pattern in the shot sleeve
is known to be closely related to the extent of gas entrapment of molten metal in the sleeve during the injection operation.
In this study, a Variable Spacing Even Mesh (VSEM) method is proposed to incorporate with a computational fluid dynamics technique,
named SOLA-MAC, to simulate the flow pattern in the shot sleeve. SOLA-MAC can deal with free surface flow problems while the
VSEM method is used to handle the problem where the space in the shot sleeve keeps decreasing as the plunger moves to push
the molten metal. The model is then tested on the shot sleeve of a cold chamber die casting machine. Four plunger speeds are
tested to demonstrate the effects on the flow pattern of molten metal in the shot sleeve. The critical speed found in this
study is 38 cm/s and it is close to the reported critical speed under the conditions that the space between the plunger and
the sleeve end is 5 cm in diameter and 30 cm in length, and the fill ratio is 50%. As the plunger speed is slower than the
critical speed, the wave front propagates along the sleeve faster than the plunger and reflects against the end wall of the
sleeve. The remaining air in the shot sleeve is entrained as the wave front enters to the gate. As the plunger speed is higher
than the suggested critical speed, the melt is immediately pushed higher in front of the plunger and forms a surge. The surge
traps air in the early stage of the injection process. 相似文献
3.
V. D. Tsoukalas 《International Journal of Cast Metals Research》2013,26(6):581-588
The primary objective of this research is to investigate the effect of machine related parameters on porosity formation in the aluminum die casting process. The amount and distribution of porosity in die castings was examined in relation to plunger velocity during the 1st phase, fast shot set point, plunger velocity during the 2nd phase, die cavity filling time and multiplied pressure during the 3rd phase.Standard statistical analysis was performed in order to identify the effect of each of the considered parameters and parameter interactions on porosity formation. It was found that, among the parameters considered, multiplied pressure, plunger velocity in the 2nd phase and die cavity filling time have the most significant effect on porosity formation. Using optimal die casting machine parameter levels, the optimum porosity value of aluminum alloy die-castings was predicted. The results were confirmed by further experiments. 相似文献
4.
5.
《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
6.
《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
7.
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
8.
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
9.
研究了压铸镁合金缺陷带的组织形貌及分布特征,建立缺陷带与压室预结晶(ESCs)、气缩孔及压铸工艺参数之间的对应关系,在此基础上探讨了缺陷带的形成及演化机理。结果表明,压铸镁合金截面凝固组织以缺陷带为界可划分为3个有明显组织特征差异的区域。随着压铸低速速度提高,镁合金凝固组织中ESCs含量逐渐降低,而缺陷带组织愈加明显并向压铸件中心靠拢,缺陷带宽度减小,其内部孔洞更加聚集;高速速度越大,压铸镁合金凝固组织中ESCs越分散,缺陷带向压铸件中心靠拢,压铸在无高速速度情况下,镁合金凝固组织横截面出现双缺陷带现象。压铸充型过程中金属液流的形态决定了缺陷带的分布位置和发展趋势,在高速金属液的剧烈冲刷及增压压力的作用下,靠近金属液流外轮廓的晶粒发生破碎或转动,在晶粒间形成大于剩余金属液体积的间隙,随着凝固的进行,形成沿液流轮廓分布孔洞聚集的缺陷带组织。 相似文献
10.
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
11.
JorgenG.Hedenhag 《特种铸造及有色合金》2002,(Z1)
对模具内的填充状态有影响的变数很多 ,尽可能消除这些变数的影响是十分重要的。压射端是对压铸工艺有直接影响的最活跃的因素。如果一个压射控制系统能够在压射过程中对这些变量产生的影响进行有效的补偿 ,就可以十分容易地实现连续高质量的压铸生产。这里对实时闭环控制系统的工作机理进行了分析。对响应时间长短的重要性进行了解释 ,并对不同机型与不同吨位下的一系列压射曲线进行了分析。对于模具内金属压力的低冲击特性与对影响余料长度的变量的修正的重要性也做了说明 相似文献
12.
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
13.
14.
15.
G.O. Verran R.P.K. Mendes L.V.O. Dalla Valentina 《Journal of Materials Processing Technology》2008,200(1-3):120-125
This paper discusses the application of a design of experiments (DOEs) experimental method for analysing the influence of three injection parameters (slow shot, fast shot and up set pressure) on the internal quality of die casting SAE 305 alloy parts. Initially, the experimental methods applied to the manufacturing process are described. An experimental design was followed: it employed different combinations of injection parameters and aimed to assess the presence of porosity in the die casting parts. The quality assessment of the die casting parts was based on density measurements and qualitative image analysis. Results were evaluated by means of variance analysis, which assessed how the variation in the three different injection parameters influenced the integrity of the components. 相似文献
16.
Development of vacuum die-casting process 总被引:1,自引:0,他引:1
Masashi Uchida 《中国铸造》2009,6(2):137-144
The vacuum die-casting process, started 25 years ago in Japan, has been widely applied. This technology contributes very much to improvement of castings quality. The main factor causing the defects of die castings is the trapped air in the mold cavity, while the key technology of vacuum die-casting process is to avoid the trapped air effectively by evacuating the cavity before casting. At the same time, due to the shot speed and the casting pressure reduced in half, the service life of the die is prolonged and the productivity is enhanced, as well. Vacuum die-casting process is of great significance in improving the die castings quality and making up the shortcomings of super-high-speed shot casting. 相似文献
17.
Study on interfacial heat transfer coefficient at metal/die interface during high pressure die casting process of AZ91D alloy 总被引:1,自引:0,他引:1
The high pressure die casting (HPDC) process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today's manufacturing industry. In this study, a high pressure die casting experiment using AZ91D magnesium alloy was conducted, and the temperature profiles inside the die were measured. By using a computer program based on solving the inverse heat problem, the metal/die interfacial heat transfer coefficient (IHTC) was calculated and studied. The results show that the IHTC between the metal and die increases right after the liquid metal is brought into the cavity by the plunger, and decreases as the solidification process of the liquid metal proceeds until the liquid metal is completely solidified, when the IHTC tends to be stable. The interfacial heat transfer coefficient shows different characteristics under different casting wall thicknesses and varies with the change of solidification behavior. 相似文献
18.
19.
《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
20.
《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