选择性激光烧结工艺参数对影响铸造砂型精度的优化设计

阐述了选择性激光烧结(SLS)的成型原理,并将此成型方式运用于直接砂型制作。通过用自主研制的快速成型机进行烧结试验,采用正交试验和方差分析,对影响铸造砂型精度的工艺参数进行了优化设计,得到激光功率、扫描速度、扫描间距及铺粉厚度工艺参数的最佳组合,可为基于选择性激光烧结铸造砂型的制造提供指导和参考。     

铸造3D喷墨打印砂型尺寸精度测量评定方法研究

随着铸造行业的转型发展,3D打印技术已经成熟的应用于制造铸造砂型,所制作的砂型不再单单作为铸造过程中的半成品,而是可以作为产品面向各铸造厂进行销售。但是目前对于砂型的检验标准存在缺失,对于砂型质量的把控和评定缺少依据。针对铸造砂型的尺寸精度,通过设计制作测量试块,给出了一种3D喷墨打印砂型的测量方法及评定标准,填补了目前铸造行业中这一领域在标准上的空白,对推动3D打印技术在铸造行业的应用以及砂型的产品化有着重要的意义。     

Effect of gel time of 3D sand printing binder system on quality of sand mold/core

Two important factors affecting the performance of sand mold/core generated by 3D printing (3DP) are strength and dimensional accuracy,which are not only closely related to the reactivity of furan resin and the phase transition of silica sand,but also the curing agent system of furan resin.This paper studies the influence of gel time on the strength and dimensional accuracy of a 3DP sand mold/core,taking the furan resin system as an example and using a sand specimen generated by a 3DP inkjet molding machine.The experiment demonstrates that the gel time of 3 to 6 min for the sand mixture suits 3DP core-making most under the experimental condition.However,it should be noted that under the same resin condition,the strength of a no-bake sand mold/core is higher than that of a 3DP sand mold/core.The dimensional accuracy of the sand mold/core does not change significantly when the gel time is less than 15 min.Improving the activity of binder and developing ultra-strong acid with low corrosion shall be an effective way to improve the quality of the mold/core by 3D printing.     

铝-硅合金砂型铸件改为压铸生产的工艺改进

通过一个铝-硅合金端盖压铸件设计实例,探讨了铝-硅合金砂型铸件改为压铸生产时,要在合金化学成分、熔炼工艺和铸件的工艺性能等方面,根据压铸工艺的特点对铸件整个生产工艺进行改进,以满足压铸生产的特殊要求。压铸铝-硅合金中ω（Fe）可以达到1．0％。ω（Fe）〈0．150%时,ω（Mn）要达到0．5％-0．8％,以防止粘模。对于不太重要的铝合金压铸件可以省略熔炼过程中的变质处理过程,通过合理设置加强筋、减少壁厚、减小拔模斜度等措施,改善压铸件的结构工艺性。     

薄板坯连铸凝固状态分析与结晶器长度设计

推导了薄板坯连铸过程中钢液在结晶器内的凝固传热有限元方程,开发了钢液凝固状态及温度场分布的模拟分析软件,探讨了拉坯速度及结晶器长度对结晶器出口坯壳厚度的影响。     

Computer simulation for centrifugal mold filling of precision titanium castings

Computer simulation codes were developed based on a proposed mathematical model for centrifugal mold filling processes and previous computer software for 3D mold filling and solidification of castings (CASM-3D for Windows). Sample simulations were implemented for mold filling processes of precision titanium castings under gravity and different centrifugal casting techniques. The computation results show that the alloy melt has a much stronger mold filling ability for thin section castings under a centrifugal force field than that only under the gravity. A "return back" mold filling manner is showed to be a reasonable technique for centrifugal casting processes, especially for thin section precision castings.     

Foundry technology and its applications of ductile iron castings produced by water-cooled copper alloy mold

The high efficiency mechanized foundry technology of castings produced by using water-cooled copper alloy permanent mold has been systematically studied. Through the researching a Cu-Cr-Mg alloy with high conductivity and good combined mechanical properties used for making permanent mold was developed, and the basic design principles of the water-cooled permanent mold along with the control-range of relevant foundry processing parameters were also established.A cast production line equipped with water-cooled copper alloy mold was designed and fabricated for production of ductile iron automobile gear castings. This production line can consistently make automobile gear castings in QT500-15 and QT600-5 (Chinese Standard) grades of ductile iron with up to 95 % casting success rate.     

基于3D打印的玩具枪弹夹模具水路设计

以玩具枪弹夹为研究对象,借助UG软件进行产品建模,利用Moldflow模流仿真对塑件进行水路设计。通过对传统水路和跟形环绕设计的随形水路两种方案的冷却效果对比,结合实际水路加工工艺,确定了最优水路设计方案,为多孔深腔类模具水路设计提供参考示例。经过实际生产验证,与传统水路相比较,采用跟形环绕随形水路产品的生产周期由55s缩短至35s,效率提升了36个百分点以上。     

锌铝合金热型连铸的工艺方法

就热型连铸工艺条件下对具有共晶、包晶和共析转变的5种典型锌铝合金的连续定向凝固进行了研究,找出了各种合金的最佳工艺参数配合范围.研究表明引锭操作是热型连铸工艺的关键环节,型口温度、拉铸速度、冷却条件、合金成分和液位压头对铸锭表面质量有直接影响,型口位置的固液区存在着热和力的平衡.只有通过调节工艺参数,维持固液界面的良好位置,才能拉铸出表面光滑的线材.     

Investigating on casting mold (or core) making with coated sand by the selected laser sintering

1 .Introduction Based on the parameters and cross-section's information from a CAD model, the selected laser sintering (SLS) uses a laser beam to sinter selectively powdered solid materials (plastic, wax, ceramic, metal, etc.), and the solidified material is built up layer by layer to formthepart needed} As there are still some problems in material and technology, it is difficulty to sinter or produce directly     

Thermal stress analysis method considering geometric effect of risers in sand mold casting process

Solidification and fluid flow analysis using computer simulation is a current common practice. There is also a high demand for thermal stress analysis in the casting process because casting engineers want to control the defects related to thermal stresses, such as large deformation and crack generation during casting. The riser system is an essential part of preventing the shrinkage defects in the casting process, and it has a great influence on thermal phenomena. The analysis domain is dramatically expanded by attaching the riser system to a casting product due to its large volume, and it makes FEM mesh generation difficult. However, it is difficult to study and solve the above proposed problem caused by riser system using traditional analysis methods which use single numerical method such as FEM or FDM. In this paper, some research information is presented on the effects of the riser system on thermal stress analysis using a FDM/FEM hybrid method in the casting process simulation. The results show the optimal conditions for stress analysis of the riser model in order to save computation time and memory resources.     

热型连铸锌铝合金定向凝固线材的组织分析

对热型连铸锌铝合金定向凝固线材的铸态及热处理组织进行了观察、分析和讨论。结果表明：热型连铸锌铝合金线材的显微组织为定向生长的平行柱状枝晶组织;共晶合金ZA5的枝状芥是的每个枝晶都由多层片状共晶β和η两相构成,过共晶合金的组织为初生树枝晶和枝晶间共晶组织,其中ZA8,ZA12初生相为β相,ZA22和ZA27的初生相是α相。     

大型复杂薄壁铝合金铸件的复合型铸造

以大型、薄壁、复杂铝合金铸件为实例,介绍复合铸型的制造和应用范例。     

金属型铸造模具水冷工艺试验

对低压铸造铝合金车轮模具的水冷效果进行了测试,对比了风冷工艺与水冷工艺对铸件各部位材料性能和金相组织的影响。由水冷工艺的模具温度梯度变化,得到了提高铸件质量和生产效率的相关数据,为铝车轮低压铸造水冷却工艺的应用提供了基础技术积累。     

A verification of the thermal stress analysis,including the furan sand mold,used to predict the thermal stress in castings

The restraint exerted on a casting by a furan sand mold on the casting and the contraction of the casting during cooling was dynamically and simultaneously measured using a device that we developed. The measurements were compared during cooling with thermal stress analyses. The thermal stress analyses were based on the representative mechanical models for the furan sand mold, i.e., the elastic and elasto-plastic models used in previous studies. The comparison demonstrated that the elasto-plastic model simulates the restraint force more accurately than the elastic model. In the thermal stress analysis, it was important to describe the development of inelastic deformation and the fracture of the sand mold. However, the simulated restraint force was still twice as large as the measured force even in the elasto-plastic model. This error is most likely attributable to using the temperature-independent mechanical properties of the furan sand mold and the mechanical model of the casting alloy, which neglected the viscoplasticity at high temperature in the thermal stress analysis.     

3D打印技术的最新发展及在铸造中的应用

介绍了3D打印技术的现状与发展,重点介绍了3D打印技术在未来铸造生产中的发展和应用。3D打印技术是新的工业革命的标志性技术之一,3D打印砂芯技术用于铸造,可实现无模铸造,有效提高复杂铸件的生产效益和效率,将给铸造业带来一场新的技术革命。     

铁型覆砂工艺水基涂料简易喷涂设备研究

为解决铁型覆砂涂料涂敷效率低,涂敷质量差,涂敷成本高的问题,根据自身情况,开展涂敷工艺、涂敷设备的优化改进研究,自主设计了一种铁型覆砂工艺水基涂料喷涂设备,有效的提高生产效率和生产成本。     

"杯盖"三板式注塑模具设计与制造

从"杯盖"三板式注塑模的结构设计、制造工艺着手,对三板式注塑模的典型结构进行了剖析,对模具制造的结构工艺性(制造的可行性、经济性)进行了分析.着重介绍了三板式注塑模的结构特点和设计要点,同时,从模具制造的结构工艺方面,介绍了凸、凹模的定位加工、定模底板和剥料板的合件加工、凸模部位顶出杆孔的制造加工,以及其他的一些部位制造加工等制造要点.     

热型连铸锌铝合金的缺陷形成与机理

对5种典型锌铝合金在热型连铸工艺条件下的连续定向凝固进行了研究, 探讨该工艺下锌铝合金线材表面缺陷的产生机理, 并对部分缺陷的组织结构进行了显微分析. 结果表明 只有金属液压头、型口温度、拉铸速度和冷却条件诸工艺参数在一定范围内的协调配合, 才能拉铸出表面光滑的锌铝合金线材. 不合理的工艺参数将导致热裂、表面粗糙、糊状型口和拉漏等缺陷. 固液两相区的形状和位置对上述缺陷的形成有重要影响, 当固液两相区位于型口或型内时, 凝固界面将向型内凸入, 如果剩余液体不能抵消凝固收缩, 就会出现表面粗糙; 若凝固界面深入型内较多, 则使型内凝固的铸锭摩擦力过大, 形成热裂; 固液两相区移至型外, 凝固界面将变成平面, 容易发生拉漏.     

Sand-bed defect recognition for 3D sand printing based on deep residual network

The 3D sand printing (3DSP), by binder jetting technology for rapid casting, has a pivotal role in promoting the development of the traditional casting industry as a result of producing high-quality and economical sand molds. This work presents an approach for monitoring and analyzing powder sand-bed images to serve as a realtime control system in a 3DSP machine. A deep residual network (ResNet) is used to classify the defects occurring during the powder spreading stage of the process. Firstly, a pre-trained network was applied as the initial parameter; then it was fine-tuned on the labelled defective sample dataset to accomplish the task, which defines the sand-bed defects induced in the 3DSP processing. Furthermore, the recognition and positioning of sand-bed defects were readily achieved by dividing the sand-bed images into blocks. Experiments show that the fine-tuned network has a 98.7% classification accuracy on the validation dataset of sand-bed defects and 95.4% recognition accuracy for the sand-bed images.