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设定了慢压射工艺参数和临界速度优化方案,测定了不同慢压射条件下AM50压铸件的密度和力学性能,研究了不同匀速慢压射条件和优化方案情况下铸件的卷气,讨论了慢压射工艺与铸件强度的关系.结果表明,慢压射速度对铸件卷气有较大影响,并存在临界慢压射速度使压室卷气减少;在优化低速工艺方案条件下,选择合理的减速位置是关键因素,可以进一步减少卷气,使压铸件具有更高的密度和强度. 相似文献
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在AZ91D镁合金真空压铸过程中使用2种分段慢压射速度(两段和三段)。在充型之前型腔内真空压力变化情况通过真空传感器进行监测。压铸件组织通过光学显微镜和图像分析软件进行分析。结果表明,采用三段慢压射速度时充型时刻型腔真空压力明显降低,导致所得压铸件中气孔含量很低。通过恰当选用分段慢压射速度,在充型之前金属液在压室中的停留时间可缩短,在慢压射过程后期阶段金属液在压室中的流动也将受到抑制,这些因素可导致所得压铸件中压室预结晶组织含量较低。 相似文献
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慢压射技术的开发和理论要点 总被引:9,自引:6,他引:3
陈金城 《特种铸造及有色合金》1998,(5):30-33
压室中气体卷入金属液内而造成压铸件内部气孔是压铸过程常见的问题。针对这个问题进行过大量的研究和试验,并已取得了重大的进展,为发展慢压射技术奠定了理论基础。 相似文献
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根据慢压射、二次填充技术的基本原理,结合p-Q2图技术,论述了慢压射的加速度、临界速度的设置方法,推荐了预填充时间、预填充量的计算方式.通过成功开发气缸体压铸件的实例,诠释了慢压射、预填充两项工艺技术在实际生产中的应用方法.强调生产气缸体压铸件时须高度重视慢压射(临界)速度和加速度的设定.填充时须按金属液填充总量(包括溢流槽部分)的10%~30%对型腔进行低速预填充,其后才进行高速填充,其关键是计算预填充金属液量,正确选择预填充时填充速度及预填充行程的切换点. 相似文献
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根据慢压射理论,设定慢压射速度,在AMESim和MATLAB/Simulink的平台上实现慢压射过程的联合仿真,并运用模糊控制对压射速度进行闭环控制。结果表明,实际压射速度与预设压射速度相符合,而且没有超调,响应性也很好,对实际生产中慢压射速度的控制具有参考作用。 相似文献
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冷室压铸机最大空压射速度表示压铸机所能提供的压射能量,也表示在较短充型时间内能向型腔内充填大容量的金属熔体,以及与模具特性一起表示工艺灵活性. 相似文献
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对不同慢压射速度条件下真空辅助对AZ91D镁合金压铸件组织及力学性能的影响进行了评估。在联合有自行改进的TOYO真空系统的TOYO BD-350V5型冷室压铸机上制备片状AZ91D镁合金压铸件。研究发现,充型时型腔真空压力随着慢压射速度的升高呈现3次方增长,导致真空辅助对压铸件中气孔的降低能力随着慢压射速度的降低而下降。常规和真空压铸件中压室预结晶组织(ESC)含量随着慢压射速度的变化趋势相似。在较低慢压射速度时,真空压铸件拉伸性能受ESC含量的影响很大,随着慢压射速度的升高,真空压铸件中气孔含量的影响将变得显著。 相似文献
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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
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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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The effects of vacuum assistance on the microstructure and mechanical properties of high pressure die cast A390 alloy at different slow shot speeds were evaluated. Plate-shaped specimens of hypereutectic A390 aluminum alloy were produced on a TOYO BD-350V5 cold chamber die casting machine incorporated with a self-improved TOYO vacuum system. According to the results, the vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of mold filling. Meanwhile, tensile properties of vacuum die castings were deteriorated by the porosity content. In addition, the average primary silicon size decreased from 23 to 14 µm when the slow shot speed increased from 0.05 to 0.2 m/s, which has a binary functional relationship with the slow shot speed. After heat treatment, microstructural morphologies revealed that needle-shaped and thin-flaked eutectic silicon particles became rounded while Al2Cu dissolved into α(Al) matrix. Furthermore, the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture to a fracture mode with many dimples after heat treatment. 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