机床铸件变形量的影响因素

根据生产经验,阐述了采用树脂砂造型时,铸件结构、化学成分、冷却速度、保温时间和铸件浇注时的摆放方式对机床铸件变形量的影响;分析了这些因素影响铸件变形量的机理,列举了采用不同生产工艺的铸件变形量,并指出:铸件的结构和材料是铸件挠曲变形的最主要影响因素,而且是不能改变的因素,在实际生产中,应根据铸件的材料和结构,采取适当的造型方法、适当的保温时间和铸件摆放方式等措施来控制铸件变形,减少铸件因变形而报废的几率。     

QSn7-0.2铜合金半固态挤压成形组织研究

采用不同半固态挤压成形工艺制备了空压机斜盘用双T型QSn7-0.2铜合金部件,研究了铸态、半固态挤压的组织,对比分析了保温时间、保温温度以及挤压速度对不同部位组织的影响。结果表明,半固态挤压成形铸件组织致密性、均匀性、协同变形性均优于直接浇注铸件。最佳的半固态挤压成形工艺为:保温温度940℃、保温时间60 min、挤压速度10 mm/s。冲头区域和铸件中部组织均匀,而铸件前端组织均匀性较差。     

6061铝合金自孕育流变压铸薄壁件制备及组织性能

采用自孕育法制备6061变形铝合金半固态浆料,研究浆料保温时间对自孕育流变压铸件凝固组织及力学性能的影响,并分析了压铸件不同部位的凝固组织及其差异形成的原因。结果表明:自孕育法可有效改善6061铝合金传统铸造形成的粗大树枝晶组织,制备出具有等轴状或球状初生α-Al晶粒的铸件。采用自孕育法制浆结合高压压铸能成形完整的6061铝合金半固态流变压铸件。相比传统金属型铸造和液态高压压铸,自孕育流变压铸能显著提高铸件的力学性能。浆料等温保温过程中,初生α-Al晶粒尺寸随着保温时间的延长逐渐增大且逐渐圆整,在保温时间为5 min时获得的流变压铸件组织最为圆整,力学性能最好,过长的保温时间会恶化组织并显著降低铸件的力学性能。对于同一参数的压铸件,随着浆料充型距离的增加,模具冷却速率逐渐增大,压铸件内部组织差异明显。     

大型铸钢件的保温补贴工艺研究

保温补贴替代金属补贴在大型铸钢件上的应用还很少。本文对文献中的保温补贴替代金属补贴情况下确定保温补贴厚度的E-δ/M关系进行了修正,使得结果更准确。并指出保温补贴的模数增强最大效果为砂型和保温补贴的蓄热系数之比,超出此范围后,增厚保温补贴也不再满足保温要求。选择了大型厚板型试件1 200 mm×1 200 mm×180 mm,设计并优化了其保温补贴工艺方案,模拟结果发现由于保温补贴厚度小于金属补贴,因此必须对冒口下部因采用保温补贴而暴露给砂型的表面采用保温补贴保温,否则补缩通道在冒口颈部易产生缩颈。分别采用金属补贴和保温补贴两种工艺方案浇注了铸件。对浇注板件的探伤和解剖表明,铸件内部无缺陷。浇注结果和数值模拟结果均表明保温补贴可以替代金属补贴。但大型铸钢件要求保温补贴具有高的耐热性能,否则容易导致铸件变形。     

织机长横梁铸件的挠曲变形及防止

通过对织机长横梁铸铁件侧弯变形的应力分析,认为导致铸件产生挠曲变形的原因在于铸件两侧面存在着温差.提出在铸件主浇注系统对侧适当位置上增设“保温浇注系统”,以控制铸件两侧面温差的工艺措施,使铸件的侧弯变形量稳定的控制在2.5mm以下,大大提高了铸件的合格率.     

精密铸造空心杆状件的偏心原因分析与对策

对一种空心杆状件的偏心原因进行了分析，由于浇注系统的不合理，在钢液浮力和热变形的共同作用下，型芯产生挠度变形，从而产生铸件偏心现象。通过改变浇注系统将杆状铸件水平组树方案改为倾斜组树，该缺陷可以基本克服。     

大型扁平类铸件的变形与控制

大型扁平类铸件由于其刚度差而引起的变形可以说是不可避免的，本文通过工艺实践证实，经过适当提高其弹性模量和采取特殊工艺措施，可以将变形减小到允许范围。     

高温合金环形件整体铸造工艺设计优化

以某航空发动机环形件的整体精铸为例，使用数值模拟技术分析整体精铸工艺的熔体充型、铸件凝固缺陷和尺寸变形等关键问题，为工艺设计和优化提供理论依据。模拟和试验结果表明：通过整体浇注既满足了铸件成形需求又保证了铸件尺寸精度。通过冒口保温，有效控制了铸件缩松缺陷。最后获得了合格铸件。     

高温铝液的Sr—RE复合变质研究

由于铝合金消失模铸造的特点,铝液浇注温度较高。浇注温达760℃时,Sr变质后铸件针孔倾向大,铝液保温时间小于20min;加RE变质后铸件针孔倾向小,保温时间延长为35-40min,但用量偏大;Sr RE复合处理铝液具有变质效果好,铸件针孔倾向小,且剂用量小的优点,是一种实用的铝液处理方法。     

保温时间对ZL102合金熔液质量的影响

研究了实际生产中，保温时间对ZL102铝液质量的彤响，探讨了保温时间与变质效果和针孔度之间的关系．结果表明：Sr变质达到最佳变质效果大约需要60min；随着保温时间的延长，Sr以大约每h0.002％(质量分数)的速率烧损，其变质效果可以持续长达6～7h；精炼变质后30～90min，铸件中针孔度最小．铝液质量最好。     

Dynamic measurements of the load on castings and the contraction of castings during cooling in sand molds

The load on flange castings in sand molds was gradually increased beginning from the end of the solidification process until the final cooling stage. The maximum tensile load on the flange castings in furan sand molds was larger than that of the flange castings in green sand molds. With the furan sand mold, permanent deformation in the flange castings occurred beginning from the end of the solidification process until reaching a temperature of approximately 250 °C. The mechanical interaction between the casting and the sand mold should be considered for more accurate stress calculations, particularly in furan sand molds.     

Linear contraction of ductile iron castings

The effect of casting design on the linear contraction of ductile iron castings produced in clay- and silicate-bonded sand moulds has been studied. The designs included free and restrained square bar castings.

Free contraction of very thin sections of ductile iron in sand moulds was found to approach 1.35%. As sections increased to 25 mm thick, the contraction decreased linearly to 1.08% in silicate-bonded sand moulds, but to 0.90% in clay-bonded sand moulds.

For test pieces with end flanges which stimulated various degrees of constraint as would be experienced in a shaped casting, the contraction was found to be sensitive to the third power of the relative cooling time of the flange and the cast section. In conditions of high constraint, contraction could fall as low as 0.55%.

The data from this study represent a first attempt to provide a designer and toolmaker with realistic contraction allowances for shaped castings.     

The Influence of Processing Variables on the Dimensional Integrity of Spheroidal-graphite Iron Castings

Abstract

This investigation was carried out to identify the major factors and their degree of influence on the dimensional accuracy of spheroidal-graphite iron castings produced in chemically- bonded sand moulds. Test castings were poured into furan-resin-bonded zircon sand and silica sand moulds and sodium silicate/ CO₂ bonded silica sand moulds. A comparison of casting sizes with those of the mould cavity into which they were poured showed considerable scatter and overlap. From these data the size that each casting would have had, had it solidified without graphite formation, was calculated and found to depend on mould cavity size for each type of mould. By isolating the differences in casting size due to graphite it was possible to identify the influencing factors. Thus castings poured into furan-resin-bonded zircon sand have the highest contraction and their size depends primarily on the amount of graphite present. The dimensions of castings poured into silica sand moulds show more variation and depend not only on the amount of graphite present and the structure of the metal but also on the thermal expansion of the silica sand moulds.     

缸体、缸盖铸件生产的总体工艺路线——车用中小型发动机灰铸铁缸体缸盖铸件生产工艺(1)

介绍发动机缸体、缸盖铸件生产的总体工艺路线.目前大多数汽车发动机铸件生产企业都采用冲天炉-电炉双联熔炼,为防止铁液晶核减少、过冷度增加、白口化倾向较大,应控制电炉熔炼温度,避免长时间过热和保温;为确保铸件尺寸精度,铸型宜采用高密度造型,也可以采用呋喃树脂砂型或PEP-SET树脂砂型.根据国内目前情况,建议主体砂芯采用冷芯工艺,而水套等部位的砂芯采用覆膜砂工艺更为稳妥可靠.     

Numerical modeling of the gas evolution in furan binder-silica sand mold castings

Modelling of gas evolution during sand-mould castings is one of the most important technical and environmental issues facing the metal casting industry. The current effort focused on developing the capability of numerically predicting the gas evolution for the furan binder-silica sand system. Specifically, the decomposition of furan was experimentally analyzed and then predicted based upon the work developed in the current project. This methodology can be easily implemented into existing commercial casting codes. A parametric study was also performed for steel 4340 and aluminium A356 cylinders (D100 × H200 m) and bars (H50 mm × W50 mm × L250 mm) cast into silica sand moulds (furan binder) of 50-mm mould wall thickness to investigate the effects of superheat and heating/cooling conditions of the mould on the gas evolution. Such information would enable more technically and environmentally friendly decisions to be made concerning the process design used to make a given casting.     

大型灰铸铁皮带轮铸造工艺设计

介绍了大型灰铸铁皮带轮的铸造工艺设计.铸件质量约1.82 t,材料牌号为HT250,为了利用石墨化膨胀的自补缩作用,铸件采用刚度较高的呋喃树脂砂型生产.长期生产实践表明,工艺出品率达到90％,铸件质量符合要求.     

Influence of furfuryl moulding sand on flake graphite formation in surface layer of ductile iron castings

The influence of the use of moulding sand with furan resin, prepared both with fresh sand and reclaimed matrix, on the formation of a flake graphite formation at the surface layer of ductile iron castings has been investigated. A series of experimental heats of ductile iron cast in moulds made of moulding sand characterised by different levels of surface active elements (sulphur, oxygen) were performed. The effect of the wall thickness and the initial temperature of the metal in the mould cavity on the formation of flake graphite in the surface layer of the casting is shown in the paper. Investigations carried out by means of scanning electron microscopy (energy dispersive X-ray spectroscopy and wavelength dispersive X-ray spectroscopy) showed concentration of gradient profiles of surface active elements in the castings surface layer, which are responsible for their quality. Finally, it has been shown that there exists a significant effect of the quality of the sand on the formation of the flake graphite layer and the surface characteristics of ductile iron castings.     

铁型覆砂铸造及其发展

铁型覆砂铸造是指在金属型（铁型）内腔覆上一薄层树脂砂，然后采用这种覆砂铁型浇注铸件。原来主要用于球铁曲轴，现已扩大应用到50余种（类）铸件。由于覆砂铁型刚度较高，用于球铁件能实现无冒口铸造．提高工艺出品率，并能提高铸件尺寸精度，改善表面质量。笔者介绍铁型覆砂工艺的基本原理、发展情况以及计算机凝固模拟在该工艺上的应用。     

用呋喃树脂砂生产大型铸铁件的工艺分析与质量控制

依据对呋喃树脂砂生产大型铸铁件的特性分析,阐述了用呋喃树脂砂生产大型铸铁件的铸造工艺要点与关键工序的过程质量控制.通过介绍几种典型大型铸铁件用呋喃树脂砂生产的实例,具体说明了用呋喃树脂砂生产大型铸铁件质量的控制原则.     

The role and impact of 3D printing technologies in casting

3D printing is such a magical technology that it extends into almost every sector relating to manufacturing, not to mention casting production. In this paper, the past, present and future of 3D printing in the foundry sector are profoundly reviewed. 3D printing has the potential to supplement or partially replace the casting method. Today, some castings can be directly printed by metal powders, for example, titanium alloys, nickel alloys and steel parts. Meanwhile, 3D printing has found an unique position in other casting aspects as well, such as printing the wax pattern, ceramic shell, sand core, sand mould, etc. Most importantly, 3D printing is not just a manufacturing method, it will also revolutionize the design of products, assemblies and parts, such as castings,patterns, cores, moulds and shells in casting production. The solid structure of castings and moulds will be redesigned in future into truss or spatially open and skeleton structures. This kind of revolution is just sprouting, but it will bring unimaginable impact on manufacturing including casting production. Nobody doubts the potential of 3D printing technologies in manufacturing, but they do have limitations and drawbacks.