石膏精铸工艺扩大应用范围

现将东京都立工业技术中心研究用石膏铸造铜合金的现状介绍如下:石膏铸造的现状石膏与水混合而成具有流动性的泥浆,只要把它倒入铸型,由于水合凝结而硬化,这一过程很快捷。另外,还具有取模简单的优点。用石膏作金属铸造的铸型,最初是在金、银等的熔模铸造的填充材料方面,但这种技术现正广泛用于牙科或装饰品的小件铸造。石膏铸型在39年前已用于工业生产,,除了主要用于锌合金、铝合金等之外,还用     

基于光固化成型技术的空心叶片陶瓷铸型制造缺陷控制

陶瓷铸型是制造空心叶片的核心,相对于熔模铸造主流技术,基于光固化成型技术的一体化陶瓷铸型制造方法具有显著的优势：周期短、成本低、响应快,但如何控制铸型的缺陷是该方法发展的技术难题。为此,研究光固化原型台阶效应的解决方法,探讨铸型精细结构的凝胶注模复型行为,分析脱脂过程热应力对铸型质量的影响规律。结果表明：基于液态石蜡的流平性原理,可解决光固化树脂原型的台阶效应问题,显著减小原型表面粗糙度;随温度升高,覆膜RP60石蜡单层厚度减小,90 ℃时稳定在0.06 mm左右;当陶瓷浆料固相体积分数不大于62%时,可实现0.5 mm细小特征陶瓷铸型的凝胶注模真空无缺陷复型;通过镂空处理,脱脂陶瓷铸型无缺陷、精度较高。     

3D打印技术和铸造技术的融合应用与展望

3D打印技术与铸造技术相融合将发挥不可估量的作用。3D打印的蜡模、光敏树脂模、塑料、砂型、砂芯、金属等能用于失蜡蜡模、模具、铸型、型芯、复杂内腔镶件等铸造元素,这些元素可与熔模精密铸造、石膏型铸造、砂型铸造、低压（差压）铸造、双金属复合铸造等几乎所有的铸造方法融合,制造各种金属合金构件。融合解决了3D打印材料和成本的问题,突破了只能先模具后铸造的瓶颈,加速了铸造行业的发展,为快速发展个性化创新工厂、制造业升级提供了可能。     

选区激光烧结在航空件铸造中的应用

选区激光烧结因其选材广泛、成形速度快和精度高等特点,在铸造中的应用越来越多,实现了铸型制造的快速化、柔性化的发展,为铸遗行业开辟了一条新的制造途径。文中介绍了选区激光烧结在砂型铸造、熔模铸造、石膏型铸遗、陶瓷型铸造和金属铸型等方面的应用和进展,列举了一些应用实例和存在的缺陷,并对未来进行了展望。     

均衡凝固技术在实型铸造上的应用

实型铸造是用聚苯乙烯塑料模样代替传统铸造方法中模样的一种新型铸造方法。由于泡沫塑料模样留在铸型内,因而实型铸造方法的浇注充型过程要比传统的空腔铸型浇注充型复杂。空腔铸型中的铁水在型内流动是自由的,而实型铸型中的铁水受实型模样的阻碍,泡沫塑料受热气化产生气体阻     

应用石膏型快速精密铸造技术制造叶轮

根据图纸要求及铸件收缩率设计出叶轮及其浇注系统的三维铸造原型,用FDM工艺的3D打印机将原型件打印出来,并用热熔胶将原型件组装成一体,然后配制石膏浆料、灌浆,再根据FDM原型材料的热特性确定脱水与焙烧工艺规程,按工艺规程制作出叶轮石膏铸型,最后将锌合金铸液倒入石膏铸型中待其凝固后得到叶轮精密铸件。试验结果表明该方法铸造出来的叶轮尺寸精度符合要求,且和其他方法相比其制造成本更低、速度更快。     

砂处理装备：将向配置齐全、节能减排方向发展

铸造生产中使用铸型有砂型、金属型、陶瓷型、石膏型、石墨型等。在各种铸型中最为普遍和大量使用的是砂型。砂型铸造占铸件生产总量的80％以上。砂型铸造分为两大类：粘土湿型砂和化学粘结剂型砂。砂处理装备同样也分为两大类：粘土砂砂处理装备和树脂砂砂处理装备。     

充型压力对石膏型反重力铸造ZM5镁合金组织和拉伸性能的影响

将石膏型熔模铸造和反重力铸造工艺相结合,在不同充型压力下制备ZM5镁合金,研究了充型压力对镁合金石膏型薄壁件成形能力及合金铸态组织和拉伸性能的影响,得到了最佳的铸造工艺参数。结果表明:随着充型压力增大,铸态镁合金的组织明显细化;当充型压力为40kPa时,铸件的成形能力最好,镁合金的拉伸性能最佳,抗拉强度为(192±5)MPa,伸长率为(1.5±0.2)%;330~350℃的铸型预热温度、730~750℃的浇注温度、35~40kPa的充型压力能够满足镁合金薄壁件浇注的需要。     

黄壤土砂铸型与铸件界面烧结层的力学行为

黄壤土天然粘土砂湿型铸造工艺应用于铸铁生产,能有效预防粘砂缺陷、提高铸件表面质量,同时具有成本低、污染小、效率高的综合优势。这种工艺与普通的湿型铸造工艺相比,最大的区别在于,它会在铸型与铸件之间形成一层致密的烧结壳。这层烧结壳能抵挡住金属液的冲刷和渗透,在金属凝固后能牢固的粘附在铸件表面,可实现高温打箱,而不至于使铸件冷却过快、表面硬度过高,从而提高生产效率;在室温时,它又能轻易地从铸件表面脱落,减轻清砂工作量。为深入了解这一现象,开展对黄壤土天然粘土砂烧结层的高温和室温力学性能的研究,结果表明,烧结层试样在高温下具有很好的塑性,随着温度的降低,塑性减小、抗压强度提高,在室温下表现出明显的脆性。这说明烧结层力学性能的变化与其在铸造过程中的行为正好吻合。     

汽车缸套离心铸造凝固数值模拟研究

建立汽车缸套离心铸造凝固过程的数学及物理模型,对汽车缸套离心铸造的凝固过程进行数值模拟,得到汽车缸套离心铸造过程中的温度场、液固相分布及缩孔缩松状况。结果表明:采用数值模拟分析能够使汽车缸套的高速、高温、复杂的卧式离心铸造过程可视化,并可方便地通过改变铸造参数来分析对铸造效果的影响;合适的铸型转速会对充型产生较大的影响,过小则会产生雨淋现象,过大则会使充型不连续;为减少铸件外表面及端面与内表面中心部分凝固速度的差距,可以适当提高铸型的预热温度。     

Studies of microstructures made of Zn–Al alloys using microcasting

The microstructures of Zn–4 wt.% Al alloy with 0.1 mm diameter were prepared by microprecision casting based on gypsum-bonded investment casting. Aspect ratio up to 200 can be replicated in the case of the centrifugal speed of 1,500 rpm and the mold temperature of 270°C. The flow length was significantly influenced by the centrifugal speed and the preheating temperature of the mold. The flow length increases as the rotational speed and the mold temperature increase. The grain size and mechanical properties can be varied within a wide range by choosing different preheating temperatures.     

铸件和铸型间界面传热系数的试验研究

在铸造凝固过程的数值模拟中,铸件/铸型间的界面传热系数是非常关键的一个参数.为提高数值模拟精度,文中采用铝合金铸件设计了金属型铸造试验,考虑了铸型厚度对结果的影响,使用特制的热电偶采集了铸件内部不同位置的温度值.以此实测的温度场数据为基础,结合数值模拟技术和界面传热系数“反问题”的求法,得到界面传热系数与时间的函数关系.结果表明:铸型厚度不同会影响铸件铸型间的热流和界面传热系数的变化规律,且界面传热系数在铸件冷却中并非常数,随着凝固过程的继续而减小.最后将所得界面传热系数用于凝固过程的温度场模拟,与试验结果进行了对比分析,得到了合理的分布,说明此界面传热系数测定方法可行.     

Effects of Sb,Sr, and Bi on the material properties of cast Al-Si-Cu alloys produced through heated mold continuous casting

Rare earth metals can create a fine eutectic Si structure in cast Al-Si_10.6-Cu_2.5 (ADC12) alloys produced through heated mold continuous casting. Fine and spherical eutectic Si phases are created in the ADC12 alloys through the addition of Sr0.04, and fine lamellar eutectic Si phases are created through Sb and Bi addition. Crystal orientation on the face perpendicular to the casting direction is formed by [110]; however, this uniform formation is collapsed in the ADC12 alloy with an increasing amount of Sr addition, such as Sr > 0.04%. The shape of the eutectic Si is statically analyzed, and the effects of the eutectic Si characteristics on the mechanical properties are examined experimentally. On the one hand, the mechanical properties of the ADC12-Sr alloy increase with increasing Sr content because of the fine eutectic Si, the randomly orientated crystal formation, and so on. On the other hand, the material ductility increases in the ADC12 alloy with increasing addition of Sb and Bi elements. A high fracture strain of approximately 14% is obtained for the ADC12-Bi1.5 alloy.     

Optimization of squeeze casting parameters for non symmetrical AC2A aluminium alloy castings through Taguchi method

This paper reports a research in which an attempt was made to prepare AC2A aluminium alloy castings of a non symmetrical component through squeeze casting process. The primary objective was to investigate the influence of process parameters on mechanical properties of the castings. Experiments were conducted based on orthogonal array suggested in Taguchi’s offline quality control concept. The experimental results showed that squeeze pressure, die preheating temperature and compression holding time were the parameters making significant improvement in mechanical properties. The optimal squeeze casting condition was found and mathematical models were also developed for the process.     

Influence of gas flowrate on filling ability and internal quality of A356 aluminum alloy castings fabricated using the expendable pattern shell casting with vacuum and low pressure

In this study, a new casing process named expendable pattern shell casting process with vacuum and low pressure (EPSC-VL) was introduced to produce complicated and thin-walled aluminum alloy castings. The gas flowrate is one of the most important process parameters for manufacturing castings during the EPSC-VL process. In the present work, the influence of gas flowrate on the filling ability and internal quality of A356 aluminum alloy castings fabricated by the EPSC-VL process were investigated. Moreover, the filling ability, internal quality, as well as mechanical properties of A356 aluminum alloy castings obtained by EPSC-VL and lost foam casting (LFC) processes were also compared. The results obtained suggested that the filling length increased with the increase of gas flowrate, and the filling length of the thick section was larger than that of the thin section under the same gas flowrate when the gas flowrate was less than 19 m³/h. Furthermore, the porosity of castings decreased with increasing gas flowrate, and the microstructure of castings became denser, and the internal quality of castings was obviously improved. The comparison experiments showed that the EPSC-VL process had superior filling ability, internal quality, and mechanical properties compared with the LFC process, and the surface quality of castings obtained by EPSC-VL process was also better than that of the LFC process. The casting practice of complicated and thin-walled A356 aluminum alloy intake manifold part also suggested that the EPSC-VL process had an obvious advantage for the fabrication of complicated and thin-walled aluminum alloy castings compared with the LFC process.     

Zn对医用Mg-Mn合金显微组织的影响

Mg合金具有可降解性、生物学特性和力学相容性等一系列特性,是一种极具发展潜力的新型可降解生物医用材料。本文采用真空气氛保护金属型Mg-Zn-Mn合金,通过金相组织观察和硬度试验,研究了合金的性能。结果表明:纯Mg中添加合金元素Zn和Mn可显著地细化晶粒,Zn含量的变化对Mg合金晶粒尺寸影响较小;Mg合金硬度随着Zn含量的增加而提高,并且Zn具有较好的固溶强化效果;Mg合金固溶处理后,晶粒发生一定程度上的长大,Mg合金硬度随Zn含量的增加而提高,这说明固溶强化的效果强于晶粒粗化而造成的力学性能降低。     

Effect of reinforcement on wear behaviour of aluminium hybrid composites

Abstract

Aluminium metal matrix composites are among the recent developments in engineering applications to meet the present day need of light weight, high strength/weight ratio and good wear properties. In the present study, AlSi10Mg alloy reinforced with 3, 6 and 9 wt-% alumina with constant 3 wt-% graphite particles was produced by stir casting technique. Microstructural investigations as well as evaluation of mechanical properties such as hardness, tensile strength and double shear strength were conducted on composites and unreinforced alloy specimens. Tribological behaviour of hybrid composites was studied using pin on disc test machine. Wornout surfaces were analysed using scanning electron microscopy, and wear debris were analysed using X-ray diffraction. Results revealed that the mechanical properties of hybrid composites were higher than unreinforced alloy. Dry sliding wear test results indicated that the aluminium alloy reinforced with 9 wt-% alumina and 3 wt-% graphite has highest wear resistance compared to unreinforced alloy.     

376QB汽油发动机铝合金汽缸盖热处理工艺的改进

通过热处理工艺试验,确定了铸造铝合金ZL111的最佳热处理工艺参数,使其具有良好的综合机械性能,从而满足发动机汽缸盖的机械性能要求。     

原位合成钛基复合材料的高温力学性能

利用钛与B4C反应经普通的熔铸工艺制备了原位合成TiB和TiC增强的钛基复合材料。研究了原位合成钛基复合材料的高温力学性能和断裂机理。结果表明：随着温度的升高，其抗拉强度降低，伸长率提高。但与基体钛合金比较，由于原位合成增强体非常稳定，能有效地强化基体合金，明显提高了复合材料的高温抗拉强度。拉伸断裂机理与温度有关，室温时，增强体断裂是材料失效的主要原因；而随着温度的提高，增强体与基体合金界面脱粘成为材料失效的主要原因。     

金属型铝合金重力浇注装置及其模具设计的研究

为适应较小规模铸造企业的生产模式、有效提高铸件质苎．对铝合金重力浇注装置及其模具结构进行设计研究。在装置上采用简单的机械结构使之方便手动操作，使用完全金属型模具并使之具有倾转功能。研究发现在浇注过程中具有操作简单方便、易于维护，并且制造成本低廉、模具设计制造周期短的特点。铝合金液体在模具中的充型和排气效果良好，可减少气孔、缩孔等铸造缺陷。特别适用与中小型企业的小批量铸件的生产和产品零件的试制加工。