TiAl基合金发动机排气门的制备和台架试验

采用真空离心铸造 机加工工艺制备的TiAl基合金排气门在 483Q柴油发动机台架上进行了 48h耐久性试验。结果表明 :TiAl基合金排气门质量轻 ,约为 2 1 4材料排气门质量的 50 % ;TiAl基合金排气门与原气门座组成的摩擦副具有更好的磨合性和耐磨性 ,并且实际接触面积由原来的 30 %提高到 70 % ,相对下沉量由 8.0×1 0 - 3 m降低至 1 .0× 1 0 - 3 m ,说明TiAl基合金排气门可满足高性能发动机的服役要求。     

Development of permanent-mold cast TiAl automotive valves

This paper presents the results of an EMTEC funded project to develop low-cost TiAl automotive valves. The alloy studied was Ti-47Al-2Nb-1.75Cr (at %). Over 800 valves were cast, using several variations of the permanent-mold process, in a multi-cavity steel mold. Applying pressure during solidification improved the casting fill. However, none of the permanent-mold casting methods produced pore free as-cast valves. The as-cast microstructures of valves produced by permanent-mold casting were much finer than investment castings of similar section sizes. Of the permanent-mold casting methods, the injection cast method exhibited the finest as-cast structure showing a potential for a new high output method for producing fine-grained TiAl components. Room temperature tensile properties of the permanent-mold material were superior to those of investment castings with a similar microstructure. Two sets of valves were road tested for a total of 50000 km with average 2% fuel savings and no valve damage. There is a need to overcome few challenges before this technology can be implemented in the automotive industry.     

The development of low-cost TiAl automotive valves

This paper presents the results of a project funded by the Edison Materials Technology Center to develop low-cost titanium aluminide automotive valves. In the course of the project, more than 800 valves were produced using several variations of the permanent-mold casting process. Applying pressure during solidification improved the casting fill; however, none of the permanent mold casting methods produced pore-free as-cast valves. The as-cast microstructures of the valves were much finer than investmentcast microstructures of similar section sizes. The room-temperature tensile properties of the permanent mold castings were superior to those of investment castings of a comparable section size. M.M. Keller earned her M.Sc. in materials engineering at the University of Dayton in 1993. She is currently a Ph.D. student in materials engineering. She is also a member of TMS. P.E. Jones earned her M.Sc. in materials at the University of Dayton in 1993. She is currently a Ph.D. student in materials engineering. She is also a member of TMS. W.J. Porter III earned his M.Sc. in materials engineering at the University of Dayton in 1990. He is currently project engineer at the University of Dayton Research Institute. He is also a member of TMS. D. Eylon earned his D. Sc. in materials engineering at Technion, Haifa, Israel, in 1972. He is currently a professor of graduate materials engineering at the University of Dayton. He is also a member of TMS.     

Regeneration of marine engine valves using laser surfacing

This article presents an analysis of the applicability of laser surfacing of the exhaust valve face of a marine diesel engine using cobalt-based powder. After preparation by machining, the selected valves were subjected to laser surfacing using a high-power ROFIN DL020 laser. The EuTroLoy 16012 powder was used in the surfacing process. One of the valves was cut and subjected to metallographic examination and hardness measurements, while the other valves were assembled in the engine, which worked for approx. 3000 h. The tests conducted for the initial condition showed a dendritic structure of the surfacing weld, characteristic for surfaced layers with carbide inclusions uniformly deposited in interdendritic areas and a minimally changed structure of the steel substrate. Similar tests were carried out for the valves after their period of operation. The valves' faces showed little wear. The microstructure of the surface weld was found to have minor changes mainly due to the effects of diffusion processes occurring in the operating temperature and a decrease in hardness. The laser surfacing technique has proven very useful for the regeneration of marine engine valves.     

基于特征的义齿固定桥设计方法

文章以简化义齿设计过程，提高义齿设计准确性为目的，提出了基于特征的义齿固定桥设计方法。该方法首先根据缺失牙邻牙信息，采用Nurbs曲面模型恢复固位体的形态以保证其支撑作用，然后根据邻牙、对颌牙原始特征，运用B样条曲线模型建立了四条整体特征曲线和两条颔特征曲线，用以限制标准牙模型的特征参数，从而完成义齿桥体形态设计。最后对固位体与桥体模型接触区实施圆弧过渡处理。研究结果表明，采用该方法生成的连接体不仅满足临床对连接体形态、位置的要求，并且增强了固位体的支撑作用。     

电磁高速开关阀的设计方案研究

高速开关元件种类繁多、用途各异、正确选择设计方案是提高其性能水平的重要保证。本文用相似理论分析了阀值尺寸大小、驱动方式及工作时制与开关元件快速性之间的关系。电磁高速开关元件的开关时间与尺寸成正比,大通径的高速开关阀宜采用多级（两级或三级）的结构,设计电磁－机械转换器时,采用双隐开关电磁铁（力马达）其温升比长时制的电磁机械转换器的温升减少,工作效率明显提高。     

Diagnosis of austenitic steel valves with the magneto-optical method

Samples selected from damaged austenitic steel valves of diesel engines have been examined using the magneto-optical (MO) method. The method uses a magnetic excitation normal to the material surface and enables the assessment of two conditions of the originally non-magnetic austenitic steel, namely an integral one, when the coercivity H_c is measured, and a local one that concentrates on the detection and assessment of individual defects. The results have shown that the operational load increases H_c of these materials and a defect of the fatigue crack type has been detected in the position of the valve failure.     

气门热锻模具应变疲劳寿命分析

针对气门热锻模具的早期疲劳失效,结合MSC.Marc和MSC.Fatigue数值模拟软件对气门热锻模具的成形过程进行热机耦合模拟,并进行热作模具钢H13(4Cr5MoSiV1)凹模的疲劳仿真与低周疲劳寿命预测。对凹模在热锻过程中的温度分布、等效热应变分布、应变-寿命曲线、周期性变化的节点等效应力等因素进行模拟分析,最终获得了凹模的疲劳寿命分布云图。研究结果表明:最先发生失效的位置在凹模R根部区域,寿命仅1460次,与实际生产情况中模具的失效位置及寿命值相符合,实现了气门热锻模具的疲劳寿命模拟预测。     

Performance,tolerance and cost of TiAl passenger car valves

It is the clear goal of all new engine development to improve efficiency and to reduce emissions. Big efforts are taken and one field of exhaustive research is the valve train of four-stroke SI engines. It is seen as a proven benefit to replace existing cam shafts with so called cam-less systems, however, those require light weight engine valves. Amongst other materials, valves made from intermetallic TiAl γ-alloys were developed in recent history. Those had to fulfil a performance evaluation as well as meet cost objectives. As costs are strongly related to the production process and the required tolerances, a rough outline about these topics is also given.     

Technology for heat treatment of engine valves of VAZ passenger cars

The valve gas-distributing mechanism is an important part of an internal combustion engine. Its main components are inlet and discharge valves, which have to meet specific requirements due to the conditions of their operation. The general requirement on all valves is their close fitting to the seats under a high pressure in the cylinder, which is realized due to the conical camfer that serves as the seat surface. For this reason, the camfers are ground thoroughly. The rod of the valve, which moves inside a guide bush, is also fabricated with high precision. The valves operate at an elevated temperature and therefore are produced from high-temperature alloys. The present paper is devoted to the manufacturing technology for valves of the gas-distributing mechanism.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 6–9, October, 1996.     

气门热精锻模具的正常与异常失效

气门热精锻模在正常工作时其失效方式为磨损、冷热疲劳裂纹或压塌。然而由于模具加工、安装或使用不当会造成开裂,R位刮伤、毛坯卡模或平台麻坑等非正常失效。本文对各种失效形式及其对模具寿命与经济效益的影响进行了探讨。     

伺服阀在铝箔轧机中的使用和维护

电液伺服阀是铝箔轧机压上电液控制系统中的关键零部件。在介绍电液伺服阀工作原理的基础上,就其使用与维护要素作了阐述。     

模糊PID方法用于液压比例阀的高精度定位控制

针对轧钢自动化生产线上对比例阀的定位控制精度要求的日益提高,比例阀在不同的工作区间,需要设定不同的PID参数。本文利用模糊控制器被控对象的时滞、非线性时变性具有一定适应能力的特点,采用模糊控制器使比例阀在不同工作区间自适应调整PID参数值,改进其控制效果。通过在某重卷机组中对自动上卷小车进行定位控制,比例阀输出平稳,定位精度高,动态响应快,误差小。     

Computer modeling of wear in extrusion and forging of automotive exhaust valves

In an automotive engine valve forging process, the billet is cold sheared, induction heated, and fed to a mechanical press for a two-stage forging operation with the first stage being extrusion. The main limiting factor in this operation is the wear of the dies during the first stage, extrusion. In this study. abrasive wear was identified as the primary mode of wear, and computer simulation was used to investigate the effect of process variables, such as press speed, initial billet temperature, and die preheat temperature upon abrasive wear. The result generated by this study should be applicable to other part geometry and not limited just to exhaust valves. R. Thlsyan, Department of Industrial and Systems Engineering, The Ohio State University, Columbus, OH 43210, USA     

超高压溢流阀静动态特性的研究

本文介绍了超高压技术的一些基本特点,对超高溢流阀的静动态特性进行了详细的理论分析与实验研究,阐明了在超高压领域中对单极直动溢流阀分析时与一般压力下的不同点和应注意,并进行了实验论证。     

Tribo-corrosion protection of valves and rotors using cermet layers applied with HVOF

Protection of Metals and Physical Chemistry of Surfaces - Protection of conventional steel parts in equipment that must withstand wear of the tribo-corrosion type (combination of heat and an...