Cast joining of cast iron to aluminium casting matrix

Abstract

The present study focused on reinforcing Al–Si–Cu alloy with a cast iron insert and using Zn–xAl–3Si–0·5Mg (wt-%) intermediate alloys by the cast joining technique to take advantage of lightness and stiffness of the hybrid structure. The experimental set-up consisted of coating the insert using hot dipping method followed by immersing the coated insert into the Al melt and allowing the system to cool down to the room temperature. The quality of Al–Fe joints in terms of morphology, thickness, chemistry and microhardness was evaluated as a function of coating composition and immersion time in the Al melt. Characteristics of reaction layer at the coating/insert interface and its effects on the joint properties were determined using microstructural analysis and thermodynamic calculations. Combination of a suitable coating containing 27 wt-%Al and optimised process parameters, including 1 min immersion time, resulted in the formation of an Al–Fe joint with promising characteristics.     

铸铁表面上化学沉积Ni—P—SiC复合镀层性能的研究

研究了热处理工艺对沉积在铸铁表面上的Ni-P-SiC复合镀层性能的影响。结果表明:经450℃×2h热处理之后,复合镀层的耐磨性高于400℃×1h热处理复合镀层的耐磨性;并且硬度和结合力达到良好的配合。     

干盘管系统和主动式冷梁的应用探讨

介绍了干工况风机盘管（以下简称“干盘管”）系统的工作原理;举例计算了干盘管系统的空气处理过程;分析了干盘管系统的控制过程,并介绍了干盘管的一种先进的应用形式——主动式冷梁。     

风机盘管变冷水温度运行的性能研究

通过实验分析影响风机盘管冷量的因素，研究了在风机盘管空调系统中冷水温度变化对末端空气处理设备热湿处理能力的影响；确定了判断满足风机盘管设计要求的变水温工况方法及最大冷水供水温度，为风机盘管空调系统变水温节能运行提供依据。     

舰船高温防护涂层技术研究进展

高温防护涂层在舰船高温部件尤其是动力系统部件上能够发挥重要作用,保护其在海洋环境中避免发生氧化和腐蚀。本文简要介绍了舰船高温防护涂层的性能特点、分类及等离子喷涂、激光熔覆、渗铝等耐高温涂层制备方法。     

主动式冷梁系统在智能办公建筑中的应用探讨

介绍主动式冷梁的工作原理以及应用冷梁系统的空调系统与传统空调的区别。分析冷梁系统的控制过程,并指出冷梁系统在运行过程中存在的问题。     

变风量变水温系统解耦控制实验研究

针对变风量变水温空调系统,分析了该多变量多输出系统的回路交互影响,设计了解耦器并整合到控制器中。通过实验证明,解耦器的应用能较好的解决变风量系统中温湿度控制问题,达到了良好的节能效果。     

An estimate of the temperatures and velocities of particles in a gas flame jet using a photoemission method when depositing powder coatings

A method of measuring the temperatures of a flame and of powder particles in it and also their flight velocities in a gas-flame jet by a photoemission method when depositing coatings is described. An estimate is made of the temperature dynamics of the objects being investigated. The time resolution is 5 μsec and the velocity is 76 m/sec. Translated from Izmeritel’naya Tekhnika, No. 3, pp. 49–54, March, 2009.     

内燃机挺杆疲劳磨损过程的X射线研究

对三种合金铸铁挺杆进行了冷拖发动机台架试验,用X射线衍射方法对表面织构,衍射线宽化以及上述台架试验中各阶段的表面残余应力分别进行了测定,通过比较三种挺杆的测定结果可以得出:影响挺杆接触疲劳寿命的因素之一为滑移系统相对于摩擦面的取向;疲劳寿命不同,表面残余应力在整个磨损过程中的变化方式和碳化物的保留程度均有所不同,本文对上述实验结果,在弹—塑性裂纹模型的基础上进行了讨论。     

大温差空调水系统的技术经济分析

空调水大温差技术是一项节能技术,但有其适用场合.本文从水泵能耗减少和冷水机组能耗增加两方面进行对比,得到了大温差技术的适用对象,并从初投资和运行费用两方面对大温差技术进行技术经济分析,提出简单实用的计算方法.     

主动式冷梁空调系统在五星级酒店中的应用

以某五星级酒店为例,介绍了主动式冷梁空调系统的特点,重点介绍了该空调系统应用于五星级酒店时,在客房空调负荷的计算、冷梁供冷方式、冬季冷梁供热等方面需要注意的事项,以及系统运行时应注意的问题。为该系统应用于五星级酒店的客房提供了参考。     

基于DOE的挖掘机排气消声器结构优化设计

以某型挖掘机的排气消声器为例,通过现场测试及仿真分析,找出了消声量较小的频率段。运用DOE方法,对各消声单元主要尺寸进行参数化建模,安排优化拉丁方试验,分析各消声结构对其消声性能的贡献量。通过多目标优化计算得到最优化的消声器结构参数。优化后消声器的模拟计算结果表明,改进后的消声器在目标频率段的消声量明显提高。     

中温锌系磷化膜及皂化膜的组织结构研究

为深入研究磷化皂化润滑机理及改进磷化皂化工艺,利用扫描电镜(SEM)、电子探针(EPMA)、X射线衍射(XRD)等手段对中温锌系磷化膜及硬脂酸钠皂化膜的表面形貌、截面形貌、组织结构以及成分组成进行了研究.结果表明:中温锌系磷化膜主要以磷酸锌(H膜)为主,并有少量磷酸锌铁(P膜),磷化膜表面有棒状和球状两种形貌结构,磷化膜厚度约为20μm.经过皂化后膜层分为磷酸锌、硬脂酸锌和硬脂酸钠三层,硬脂酸锌和硬脂酸钠具有很好的润滑效果,皂化膜表面为棉絮状形貌.     

离心式冷水机组大温差设计运行特性的实验研究

中央空调冷冻水系统大温差设计可以显著降低输配能耗,对系统节能具有重要意义.但随设计温差增大、冷冻水流速降低,蒸发器水侧传热系数逐渐减小,成为制约冷水机组能效的主要因素.本文基于蒸发器换热机理,理论分析了冷冻水大温差对蒸发器换热性能的影响,并通过离心式冷水机组串联运行的方案,实验对比了大温差工况下不同水路流程对整机性能的...     

航空用高温合金防护涂层的研制及其应用的新进展

综述了高温合金防护涂层研究的发展及其应用,重点介绍了其制备工艺和存在的问题以及在航空航天及民用领域中的典型应用.     

加热温度与保温时间对铝-硅镀层组织演变的影响

采用扫描电镜观察了钢板表面铝-硅镀层的微观组织,利用热模拟机研究了铝-硅镀层在不同加热温度和保温时间下镀层中合金层厚度的变化规律,利用辉光光谱仪测定了铁元素向合金层中的扩散规律.结果表明:热处理前镀层合金层组织由Fe2Al5二元金属间化合物和Fe2SiAl7三元金属间化合物组成,热处理后镀层合金层组织由Fe2SiAl2...     

Microstructure evolution in bulk and surface states of chromium rich nickel based cast alloys reinforced by hafnium carbides after exposure to high temperature air

Abstract

Three alloys based on nickel, with a high level of chromium (25 wt-%) and containing varied quantities of carbon, 0·25 and 0·50 wt-%, and hafnium, 3·7 and 5·6 wt-%, fabricated by casting, were subjected to a 46 h long exposure at 1200°C in dry industrial air. The aim of the work was to investigate the thermal stability of their carbide interdendritic network and to discover their general behaviour in high temperature oxidation. The volume fraction of the hafnium carbides decreased slightly during high temperature exposure but their fragmentation was rather limited. In contrast, chromium carbides appeared in the two alloys, which initially contained exclusively HfC, and this may result in a decrease in their high temperature properties. The evolution of the carbides appeared to be responsible for a moderate lowering of room temperature hardness. The behaviour of the three alloys during high temperature oxidation was very good, despite the unusually high content of hafnium. All were chromia-forming, although oxidation of Hf led to HfO₂ islands in the external scale and in the subsurface region. In summary, the behaviour of these three alloys showed that the HfC containing Ni–25Cr family is potentially interesting for applications at very high temperatures.