A357合金低压铸造过程及性能研究

采用低压铸造方法对A357合金的充型过程以及铸件微观组织和力学性能进行了研究。结果表明：当充型压力低于30kPa时，随着充型压力增大可以得到表面质量较优的铸件；达到30kPa以上时，就出现粘砂、夹杂、气孔等缺陷。低压铸造有利于优化组织，提高铸件的力学性能。     

镁合金半固态流变充型过程数值模拟

利用所建立的流场、温度场耦合半固态表观粘度的三维数学模型,分析了镁合金及半固态镁合金AZ91B在不同充型速度时的流变特性。结果表明:具有伪塑性体及宾汉体特征的半固态流体,在相同充填条件下,具有充填过程平稳、卷气少等特征,从而可减少液态金属充型时遇到的常见缺陷。半固态材料铸造技术为解决铸件内部缺陷,调整成形工艺,提高产品质量提供了一种新方法。     

A356半固态触变充型与压铸充型过程模拟比较

利用商业软件Flow-3D，模拟了A356合金半固态触变压铸和普通压铸的充型流动过程。模拟结果表明：相同模具结构中的半固态压铸和普通压铸充型过程，半固态流动平稳，普通压铸由于湍流流动，因而容易出现气孔、卷气夹杂等缺陷。半固态触变压铸和普通压铸具有相同的流动通道。     

设计铝合金压铸模具浇注系统类型的原则

根据具体零件结构的特征，可设计出相应的压铸模浇注系统，如环形浇道、中心展开浇道、外侧浇道、集中大溢流等浇注系统。尽管这些浇注系统也存在不足之处，但总的原则是：使流入型腔的铝合金液尽量减少曲折、汇合，尽可能避免直接冲击型芯，不宜立即封住分型面，有利于压力的传递，形成良好的充填状态和排气条件。     

Al-Mg-Si合金半固态触变成形研究

以水泵盖为目标零件,在自行建立的半固态触变成形试验线上使用A357合金和新开发的半固态专用铝合金Al-6Si-2Mg进行了半固态触变压铸试验研究.对这两种合金在半固态坯料制备、二次加热及半固态压铸中的显微组织及工艺性进行了比较.结果表明,Al-6Si-2Mg合金在触变成形过程中均表现出更好的工艺可控性,其半固态压铸件热处理后的性能为σb=335MPa,σs=305MPa,δ5=3%,强度高于A357,伸长率与铸态A357合金相当.试验最终获得了充型完好、性能优异、组织均匀的半固态压铸件.     

半固态A356压铸件充型与凝固过程的数值模拟

利用ProCAST软件对A356合金半固态压铸件下壳体进行耦合数值模拟。结果表明,在模具温度为220℃,充型温度为590℃、压射速度为5m/s时,半固态浆料充型平稳,温度场分布均匀,减少了缩孔、缩松等缺陷,为A356合金半固态压铸成形工艺的制定和优化提供了依据。采用此工艺参数,生产出合格铸件。在该件上所需部位可以钻螺纹孔,与其他零件装配使用。通过试验,验证了数值模拟优化工艺参数的合理性。     

Rapid fabricating process of zinc alloy moulds based on vacuum casting process

Abstract

A rapid fabrication process was developed by combining stereolithography prototype, silicone rubber mould and vacuum casting process for zinc alloy moulds. Transfer coating mould was introduced as casting moulds reproduced from silicone rubber moulds. Vacuum casting process was applied to improve filling ability of complicated mould with fine pattern surface. Vacuum reduces the gas counterpressure in the casting mould cavity and then improves the filling ability.     

磁流铸造条件下A357合金充型能力的试验研究

为了解决大型薄壁铸件的充型问题,利用大型磁流铸造设备对流动磁场作用下的Ａ３５７合金的充型能力进行了试验研究,结果表明：在相同的磁场作用强度下厚壁铸件比薄壁铸件的充型能力好;当铸件的壁厚相同时,在磁场的作用下,合金的充型能力比无磁时提高５０％。     

镁合金半固态流变压铸充型凝固过程数值模拟及试验研究

在前期平板模型流变压铸充型凝固过程数值分析的基础上,利用所建立的数学模型对镁合金压铸件中间轴螺塞进行了数值分析和实验研究,对比分析了零件成形时镁合金牛顿流体与镁合金半固态流体的充型特征及零件中存在缺陷的位置和大小。结果表明,与牛顿流体相比半固态流体更易实现铸液充型时的顺序填充,有利于铸型中的气体的排出和铸件成形质量的提高。模拟结果与试验结果吻合较好。     

Influence of filling parameters on fatigue properties of A357 alloy produced by counter pressure plaster mold casting

The influence of filling parameters including pouring temperature, filling speed, boost pressure and synchronous pressure on the fatigue of A357 alloy produced by counter pressure plaster casting was studied. The Taguchi method was used to investigate the relationship between the fatigue performance and filling parameters. The results show that filling speed is the most significant factor among the four parameters. Synchronous pressures is less influential on the fatigue life when the value of synchronous pressure is from 400 kPa to 600 kPa.     

半固态A356合金流变充型的极限长度

通过对半固态合金流变充型机理分析,推导出可以定量计算半固态A356铝合金在圆管内流变充型极限长度的数学模型,该模型包括了工艺参数和半固态A356合金的自身特性。采用间接挤压铸造阿基米德螺旋线试样的方法对该数学模型进行了实验验证,实验结果表明:理论计算值与实验测定值之间的最大偏差小于8%;该数学模型可以定量分析和估算工艺因素对充型能力的影响,并可预测充型极限长度,这对半固态合金流变成形工艺设计和模具设计都有参考价值。实验和理论计算还表明,充型压力和充型速度是影响半固态合金充型能力的两个主要因素,提高充型压力、一定充型压力下适当减小充型速度都可以提高充型能力。     

铝合金半固态压铸工艺参数及性能研究

应用具有不同厚度的简单板材模具来系统研究压铸工艺参数对A356铝合金半固态压铸件性能的影响,以优化半固态压铸工艺及其参数.试验结果表明,对A356铝合金半固态压铸,其性能随压射压力的增大而提高,当压射压力大于100 MPa,则性能基本上不再提高.压铸速度过小或过大会降低压铸件的性能.另外建压时间、坯料加热温度、模具预热温度以及脱模剂等参数对半固态压铸件性能也有明显的影响.     

基于CAE分析的电脑外壳压铸模浇注系统的设计

针对镁合金特殊的凝固性质和金属铸型的不透明性,借助Pro/Engineer2001软件,基于PlasticAdvisor模块,设计了镁合金电脑外壳压铸模连续锥形浇注系统,探讨了该系统在材质为AZ91D合金时的浇注环境.模拟结果表明,该浇注系统填充过程平稳,温度场分布均匀,所得压铸件气体夹杂和冷隔缺陷少,整体质量较高.     

Effect of section thickness and modification on thermal analysis parameters of A357 alloy

Abstract

Thermal analysis technique relies on the cooling curve obtained when the sample is cooled in a sampling cup. This may not represent the cooling behaviour of the real casting. The microstructure developed during solidification depends not only on the nucleation and modification potential of the melt but also on the thermal gradient imposed during solidification by the mould. The factors affecting the thermal gradient are the mould material and casting section thickness. In the present investigation the effect of modification melt treatment, cooling rate and casting section thickness on the thermal analysis parameters of A357 alloy was studied. It is found that the dimensionless heat flux parameter is high for small section thickness castings. The metal/mould interfacial heat flux is high in a copper mould. Thermal analysis parameters of A357 alloy are found to be affected significantly by the combined action of modification, chilling and section thickness.     

铝合金支架压铸数值模拟及压铸工艺研究

利用ProCAST铸造模拟软件,对铝合金压铸件支架充型、凝固过程进行了数值模拟,得到了速度场、温度场的分布和变化规律。结果表明,浇注温度对压铸铝合金的模拟结果影响最大,其次为模具预热温度、充型速度。本试验条件下得到的优化工艺参数:浇注温度为600℃,模具预热温度为200℃,充型速度为2.5m/s。按照优化后的压铸工艺参数进行生产,得到了合格的铸件。     

智能控制的真空差压反重力铸造工艺参数优化

对智能控制的真空差压反重力铸造的真空度、充型压力、升压时间和结晶压力等主要工艺参数进行了优化分析.研究结果表明,这些参数对薄壁铸件充型能力影响程度的大小依次为升压时间、结晶压力、真空度、充型压力.缩短升压时间,充型能力会大大提高;增大结晶压力,金属液在凝固阶段的补缩作用得到加强,充型能力增强;真空度越高,铸型中的反压就越小,充型能力提高;充型压力增大,充型的初始动量变大,有利于增强金属液对薄壁铸件的充填.     

Influence of technical parameters on strength and ductility of AlSi9Cu3 alloys in squeeze casting

An orthogonal test was conducted to investigate the influence of technical parameters of squeeze casting on the strength and ductility of AlSi9Cu3 alloys. The experimental results showed that when the forming pressure was higher than 65 MPa, the strength (σ_b) of AlSi9Cu3 alloys decreased with the forming pressure and pouring temperature increasing, whereas σ_b increased with the increase of filling velocity and mould preheating temperature. The ductility (δ) by alloy was improved by increasing the forming pressure and filling velocity, but decreased with pouring temperature increasing. When the mould preheating temperature increased, the ductility increased first, and then decreased. Under the optimized parameters of pouring temperature 730 °C, forming pressure 75 MPa, filling velocity 0.50 m/s, and mould preheating temperature 220 °C, the tensile strength, elongation, and hardness of AlSi9Cu3 alloys obtained in squeeze casting were improved by 16.7%, 9.1%, and 10.1%, respectively, as compared with those of sand castings.     

镁合金真空低压消失模铸造的技术特征与实践

介绍了镁合金在真空低压消失模铸造下的技术特征。研究表明：真空低压消失模铸造的流动性受充型气体的流量与压力、浇注温度、涂层厚度、泡沫密度、真空度等多方面的因素影响；在低充型速度和低真空度的条件下，液态镁合金在真空低压消失模铸造过程中的充型形貌均呈现以内浇道为中心的拱形层状推进流动，如充型速度加快金属液流动前沿拱形形貌更加突出。而真空度增加会出现明显的“附壁效应”；与重力消失模铸造比较，真空低压消失模铸造镁合金铸件凝固更呈现“同时凝固”特征；由于快速充型、压力下凝固，镁合金真空低压消失模铸造零件的铸态抗拉强度（σh=180．8MPa）、屈服强度（σ0.2=113．2MPa）、伸长率（δ=4．4％），高于重力消失模铸造、树脂砂空型铸造的铸态性能，达到了金属型铸造的铸态性能，经热处理达到了压铸镁合金的性能范围。浇注实践表明，真空低压消失模铸造对液态镁合金，具有良好的抗氧化保护能力、优良的浇注充型性能和力学性能，可铸造出高精度的、薄壁复杂的镁合金消失模铸件，是一种极有潜力和优势的镁（铝）合金精密铸造技术。     

新型钢丝绳滚轮斜抽芯压铸模设计

在具有斜向孔或斜向凹凸铸件压铸模设计中，斜向抽芯是设计难点之一。本文给出了生产铝合金斜支架铸件的新型钢丝绳．滚轮斜抽芯压铸模实用结构．论述了模具结构特点和工作原理。该模具采用钢丝绳．滚轮抽芯机构实现斜支架铸件的斜向抽芯，模具还设有冷却系统。模具结构紧凑，工作可靠，成型塑件质量好。     

Influence of non-uniform ultrasonic vibration on casting fluidity of liquid aluminum alloy

The application of ultrasonic vibration to the casting process can be realized through mould (die) vibration. However, the resonant vibration of the mould is always accompanied by a non-uniform vibration distribution at different parts, which may induce a complex liquid flow and affect the casting fluidity during the mould filling process. The influence of non-uniform ultrasonic vibration on the fluidity of liquid AlSi9Cu3 alloy was studied by mould vibration with different vibration gradients. It is found that ultrasonic mould vibration can generate two opposite effects on the casting fluidity: the first, ultrasonic cavitation in melt induced by mould vibration promotes the casting fluidity; the second, the non-uniform mould vibration can induce a melt flow toward the weak vibration areas and turbulence there, consequently decreasing the casting fluidity. When the melt flow and turbulence are violent enough to offset the promoting effect of cavitation on fluidity, the ultrasonic vibration will finally induce a resultant decrease of casting fluidity. The decreasing effect is proportional to the vibration gradient.