Reaction between Ti and boron nitride based investment shell molds used for casting titanium alloys

The aim of this paper was to study the reaction between a Ti-6Al-4V alloy and boron nitride based investment shell molds used for invest- ment casting titanium. In BN based investment shell molds, the face coatings are made of pretreated hexagonal boron nitride (hBN) with a few yttria (Y2O3) and colloidal yttria as binder. The Ti-6Al-4V alloy was melted in a controlled atmosphere induction furnace with a segment water-cooled copper crucible. The cross-section of reaction interface between Ti alloys and shell mold was investigated by electron probe micro-analyzer (EPMA) and microhardness tester. The results show that the reaction is not serious, the thickness of the reacting layer is about 30-50 μm, and the thickness of α-case is about 180-200 μm. Moreover the α-case formation mechanism was also discussed.     

Integrated process simulation of primary shaping: multi scale approaches

We investigate simulation approaches for the modelling of the primary shaping processes micro powder injection moulding and micro casting. We could reproduce the segregation during micro powder injection moulding (MicroPIM) with a simulation using particle methods. The phase field method allows for accurate prediction of the dynamics of solidification of a melt, whereby model order reduction is used to limit the computational effort. The results give valuable advice for the process conduct and the dimensioning of the micro parts.     

单件小批量铸造生产质量控制

一台设备中铸件质量一般占到30％-70％，铸件生产直接关系着机械行业的整体质量和水平。铸造生产中普遍存在单件小批量形式，其生产特点的八个方面是引起铸件质量不稳定的关键因素。从管理方式、人员素质要求、新技术应用三个方面，提出了如何控制单件小批量铸件质量的具体措施和方法。     

To develop a quantitative method for predicting shrinkage porosity in squeeze casting

In order to secure high strength and high elongation of suspension parts, it is critical to predict shrinkage porosity quantitatively. A new simulation method for quantitative predic'don of shrinkage porosity when replenishing molten metal has been proposed for squeeze casting process. To examine the accuracy of the calculation model, the proposed method was applied to a plate model.     

尼龙梭坯注塑过程中的常见问题及探讨

简介尼龙梭坯注射成型前的物料准备,重点探讨了尼龙梭坯的成型工艺、注塑过程中常见的问题及影响因素,以及尼龙梭坯生产过程中的关键因素控制。按选定的工艺生产尼龙梭坯的合格率达95%以上,上机试验表明,尼龙梭的寿命达60d以上。     

圆盘浇铸机电气控制改进实践

冶炼厂根据原工艺设计,在铜冶炼工艺中为吹炼炉配置有阳极炉,吹炼炉放出粗铜的时间与阳极炉加入粗铜时间相匹配.但是,随着紫杂铜等冷料的加入,阳极炉精炼时间延长,圆盘浇铸机浇铸铜阳极板的时间缩短,造成阳极炉中的剩余阳极铜被迫合炉重新精炼.课题组分析和研究了作业现状,实施了对变频器、PLC等装置的改进,作业效率大幅提高,完全解...     

颗粒尺寸对注塑铁氧体/尼龙12复合材料流动性和磁性能的影响

制备颗粒尺寸不同的铁氧体磁粉,采用混炼工艺制备铁氧体/尼龙复合材料,研究了颗粒尺寸对复合材料流动性和磁性能的影响,结果表明,当铁氧体大小颗粒尺寸之比大于4时,两者级配可以使复合体系获得最佳的流动性.对颗粒尺寸影响机理的研究表明,小颗粒的尺寸下限在0.5μm附近,大颗粒尺寸上限在5μm附近,当大、小颗粒及尼龙体积分数分别...     

预处理温度对高压直流电缆附件绝缘材料空间电荷的影响

采用电声脉冲法(pulsed electro-acoustic method,PEA)研究了经过不同预处理温度处理后的高压直流电缆附件绝缘材料——硅橡胶(silicone rubber,SIR)及三元乙丙橡胶(ethylene propylene diene monomer,EPDM)绝缘层的空间电荷分布。为分析导致此空间电荷积累不同的原因,采用拉伸性能测试和动态热机械分析(dynamic thermal mechanical analysis,DMA)研究了高压直流电缆附件绝缘材料化学分子结构的变化。实验结果表明,SIR材料经过150℃预处理后,硫化更充分、交联密度增加,从而使得绝缘层中的空间电荷量减少,因此SIR的预处理以150℃为宜;EDPM材料经过150℃预处理后,综合表现为解聚反应,从而使得绝缘层中的空间电荷量增加,因此EDPM预处理温度以80℃为宜。     

混合动力汽车引擎用高导热环氧灌封胶的研制

采用环氧为基体树脂,a-Al2O3为填料研制了一种适用于大型工件的高导热灌封胶,分析了环氧树脂种类、固化剂及促进剂用量、粉体种类及用量、后固化条件等因素对灌封胶性能的影响.应用结果表明:高导热灌封胶的主要性能优于国外同类产品:物料粘度小,110℃下的可使用期达1h,便于大型工件的真空脱泡及灌封操作;固化物导热系数达1....     

Relationship between electrical and mechanical loss tangents of hollow glass powder reinforced epoxy composites: A pilot study

This study was focused on the synthesis of monodisperse poly(n‐butyl methacrylate‐co‐methyl methacrylate) submicrospheres via soap‐free emulsion polymerization and on their characterization. The glass‐transition temperatures of poly(n‐butyl methacrylate) and poly(methyl methacrylate) were approximately 25 and 110°C, respectively. Therefore, submicrospheres with different glass‐transition temperatures could be obtained through the variation of the copolymer composition. In addition, relationships between the monomer feed concentration (M₀) and the Mark–Houwink constant (α) for the copolymer submicrospheres were proposed. The molecular weights of the copolymer submicrospheres decreased sharply with an increase in the weight fraction of n‐butyl methacrylate. On the contrary, the particle diameter increased linearly from 277 to 335 nm with an increase in the weight fraction of n‐butyl methacrylate. The α values decreased with an increase in M₀, and this indicated that the branched structures of the copolymer submicrospheres were easily obtained when M₀ was higher than 0.11 g/mL of water. Consequently, the results of this study are expected to provide useful information for the synthesis of monodisperse copolymer submicrospheres by soap‐free emulsion polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011