气门电镦工艺与计算机控制

1 概述 在机械加工领域内,计算机控制得到了迅速发展。并且获得了实际生产的广泛应用。 本文指出了现有气门毛坯电镦生产中存在的问题,以及解决的方法,分析了过程参数对气门毛坯成形的影响。在此基础上设计了气门电镦过程的计算机控制系统。采用该系统后,能充分利用操作者的经验,自动调节参数,自动寻求参数的合理匹配,从而有效地提高毛坯成形质量和生产率。     

排气门电镦缺陷成因及防治措施

一新购的电镦机安装后镦制进气门未见异常，但镦制排气门却不顺，主要是开裂及成形不佳。经设备生产厂家、本单位及兄弟单位数次调试，结果还是很不理想。后经笔者观察分析后采取一些处理措施，基本解决了问题。下面做个简介。     

组织遗传对(4Cr9Si2钢)制造气门的影响

我厂生产的气门是经电镦蒜头模压成型空冷再调质处理的,在电镦蒜头过程中,由于电镦的电流不稳定,电镦温度增高,使产品造成过热,过烧组织粗大,原我们认为,将钢加热到临界点（ AC_s）以上重新奥氏体化后可以得到细晶粒,因电镦造成的过热组织可以在调质。处理中细化得到改善。但是实践证明电镦过热引起的组织粗大,经调质经理局并没有得到细化,而保留原来的粗大品位尺寸。这种现象与组织遗传有关。     

气门电镦夹子的改进

国内气门毛坯生产几乎都采用电镦工艺,在电镦机上通常用的电镦夹子(钳口)都是由二块各带一槽的长方形铜块所组成,多数用紫铜制成,也有用黄铜制成,前者导电性能较好,可塑性好,易与气门杆材吻合,但磨损快。后者导电性能较差,硬度提高了,但可塑性差,易“跑电”。不管是紫铜或者是黄铜都不耐用。现对电镦机上使用的电镦夹子(钳口)形状、材料及其安装作较大的改进后,我公司从英国引进多台立式电镦机,均已采用,效果显著。     

气门毛坯返修加热设备的改进

一、问题的提出 气门在电镦、成形生产过程中,由于设备、工夹模具故障和操作等各方面的原因,使电镦后的毛坯不能及时地送入模具中锻压成形或由于成形温度低及模具变形超差所造成的气门毛坯未压满等,都需要对气门毛坯局部再次进行加热后锻压成形,这是气门毛坯生产过程中不可避免的问题。 但是,对气门毛坯的再次加热,却存在所选择的加热设备合理性问题,它既要保证产品的加热质量,又要符合局部加热的要求。否则将会影响产品质量和毛坯的锻压成形。 我厂原来对气门毛坯反修品的再次加热,采用的是煤炭火焰炉（类似民间手工锻加热炉）加热,在加热操作过程中,由于加热温度、加热时间和局部加热位置都不易掌握和控制,故被加热后的气门毛坯存在过热、氧化脱炭、甚至过烧等多方面的加热质量问题。另外,由于这种加热方法局部加热的效果性很差,被加热的毛坯很容易使杆部的温度升高而增粗,致使气门杆都不能插入模腔内。 针对上述加热质量问题,我厂根据电镦机的加热原理革新了一台接触电加热机用于气门毛坯反修品的加热。该机可以通过控制和调节装置来调整次级电压,从而使被加热毛坯温度、加热时间控制在所需要的范围之内,解决了原用煤发火焰炉加热气门毛坯反修品所存在的加热质量问题。另外,还具有操作方便,     

气门电镦火花的成因及消除

1 电镦简介 如图所示,砧子与夹紧块(两夹紧块电气连在一起)之间施加工频低电低。工件在顶杆的推动下向砧子前进,砧子根据需要可向后退。砧子与夹紧块之间的部分工件通电被加热软化,同时受到顶杆的推力作用而被镦粗成所需形状。 电镦是气门生产过程中的一道关键工序。我们厂目前在用的电镦机的控制方式中,均为在工件接     

电镦机无级调压(流)改造

1电镦机热量控制现状及其不足　目前,大多数气门制造企业使用的电镦机的加热功率控制是通过人工改变加热变压器初级端档位实现的.这种方式存在明显不足.一是加热电压调节太粗不能连续调节;二是不能避免因电网电压不稳定引起的加热电压不稳定;三是加热过程中不能调节加热电压.这样,在有些材料（如5Cr21Ni4Mn2N）塑性差、要求镦粗比大（如大于30）、镦后形状及其一致性有严格要求等等情况下,常常导致工艺参数匹配困难、成形不理想及质量不稳定等问题.为了提高电压稳定性,我们在电镦机前加了补偿式稳压器.但由于这种稳压器由普通电机拖动碳刷架调节输出电压,电压稳定度差,偏差一般约为10V,而且响应时间一般大于0.5秒.不能做到实时控制,加了这种稳压器后,基本能满足部分产品的工艺要求,但对某些产品,尤其是颈部特长的产品,上述问题依然存在.为此,有必要采取更理想的热量控制方式.     

大型全纤维曲轴TR镦锻成形分析及装置结构优化

大型曲轴是大型内燃机的关键部件.以目前国内最大的全纤维钢曲轴TR镦锻装置为研究对象,该装置在修改曲轴大法兰的成形方式为全封闭成型后的第一次使用时,装置中模座断裂.采用DEFORM-3D软件对曲轴锻造成形过程进行数值模拟,计算得到锻造成形力和成形效果.将曲轴成形仿真的结果作为边界条件引入I-dears软件,对曲轴TR镦锻装置进行结构强度计算.计算获得了TR镦锻装置的应力和变形状态,讨论了现行结构所能承受的最大负荷.对危险区域进行结构优化,从而有效地降低了该区域的应力水平,提高了装置的承载能力,为大型曲轴的热成形工艺设计和工装的合理优化提供帮助.     

微机在气门电镦中的应用

一、问题的提出 进、排气门长期在高温燃气腐蚀和反复冲击负荷恶劣的条件下工作。随着汽车生产的日益发展和发动机性能的不断提高,应用部门对气门提出了愈来愈高的技术要求。例如:抗腐蚀能力、机械强度、生产成本等。 气门采用电镦锻压工艺,在通电加热电镦过程中不易控制工件的温度;各部位的温度不均匀;与砧块接触部温度低;颈部温度高;易产生折叠;电源电压的波动;液压系统的压力及电镦速度都会影响气门电镦质量。 1.晶粒组织对室温和高温机械性能的影响     

气门的电镦技术

0概述 　　所谓电镦,就是利用工件本身电阻在通过低压大电流时产生的热量,实现边加热边镦粗的过程.……     

大口径冲焊三通工艺研究与应用

对冲焊三通的焊接,压制等工艺参数选择进行了介绍。对冲焊三通的使用性能进行了分析。     

Fabrication of micro channels for titanium PEMFC bipolar plates by multistage forming process

Bipolar plates made of ultra-thin titanium sheet metals feature high corrosion resistance, electrical conductivity and strength-weight ratio. They are considered as a satisfying candidate for the proton exchange membrane fuel cell (PEMFC) used in vehicles. Bipolar plates have fine and complex sub-millimeter channel features which are employed to guide the flow of hydrogen, oxygen and cooling medium, to support the reaction space, to provide sealing structure, etc. Stamping process is an efficient method to fabricate those micro features with high precision and efficiency. However, the aspect ratio of those micro features is limited by the low forming limit of titanium sheet metals. Improving the aspect ratio of metallic bipolar plates could facilitate the uniform heat and mass transfer and further improve the efficiency and performance of PEMFC. Hence a challenging issue for the stamping process of bipolar plates is how to further improve the limit aspect ratio after forming. The multistage forming process is an efficient method to increase the ultimate forming depth and the accuracy by reducing the deformation localization tendency. This work aims to investigate the applicability of that process in fabricating high-aspect-ratio micro-channels on titanium sheet metals. Single stage forming experiments of the micro channels featured with fillet radius of 0.15 mm are first conducted. It is found that the ultimate forming depth of the channels parallel to the rolling direction is 12.67% higher than in the transverse direction. Furthermore, a series of punches and dies with three different fillet radii are employed in the multistage forming process. The ultimate depth of formed channels is revealed to increase from 438.1 to 621.0 μm, i.e. the aspect ratio from 0.46 to 0.67, comparing to the single stage forming process. Hence titanium bipolar plates with a higher aspect ratio could be achieved by utilizing the presented method. The contact resistances of the samples fabricated via single and three-stage forming were further tested to find out that the samples with a higher aspect ratio formed in a three-stage manner have an evident lower contact resistance.     

Fabrication of metallic bipolar plate for proton exchange membrane fuel cells by rubber pad forming

In this paper, the rubber pad forming process is used to fabricate the metallic bipolar plate for a proton exchange membrane (PEM) fuel cell, which has multi-array micro-scale flow channels on its surface. The rubber pad forming process has the following advantages: high surface quality and dimensional accuracy of the formed parts, low cost of the die because only one rigid die is required, and high efficiency. The process control parameters (rubber hardness, internal and outer radii, draft angle) of the rubber pad forming are analyzed by the finite element method using the commercial software Abaqus. After that, the rubber pad forming process is used to manufacture a metallic bipolar plate of SS304 stainless steel with perfect flow micro-channels. The results of this effort indicated that the rubber pad forming process is a feasible technique for fabricating the bipolar plates of PEM fuel cells.     

Formability and flow channel design for thin metallic bipolar plates in PEM fuel cells: Modeling

Metallic bipolar plates (BPPs) are regarded as the most promising substitute of traditional carbon‐based BPPs due to their good mechanical properties, electrical conductivity, high productivity, and low cost in mass production. However, conventional design guidelines on flow channels of carbon‐based BPPs are not perfectly valid to metallic BPPs due to the formability of thin metallic sheets, which are at risk of material rupture especially when flow channels decrease. The objective of this work is to develop a forming limit model to establish the relationship between the channel height and channel geometric dimensions by the micro stamping process, and the maximum channel height can be predicted to guide channel design of metallic BPPs from the formability perspective. Firstly, an instability criterion for micro‐scale forming was proposed to estimate when the rupture occurs during the forming process. Forming height as the function of channel features is established, and the limit of forming depth can be predicted. Series of micro stamping experiments with various dimensions are conducted to validate the accuracy of the model. Influences of main parameters on the channel forming limit and evaluation of channel design are discussed based on the model. The model in this study is an effective supplement to the channel design principle for metallic BPPs. Based on the model, design, fabrication, and testing of metallic BPPs will be done in the following research, Part II: Experiments.     

Two-stage forming approach for manufacturing ferritic stainless steel bipolar plates in PEM fuel cell: Experiments and numerical simulations

Multi-stage micro-channel forming by stamping, as a method for cost effective and efficient for mass production, was performed for ultra-thin ferritic stainless steel sheets with thicknesses of 0.1 and 0.075 mm, as a good substitute for traditional graphite bipolar plates of proton exchange membrane fuel cell. Attention was directed to enhance the final forming depth and minimize localized thinning, extremely important aspects of the micro-channel on bipolar plate, by the proposed forming process. A forming depth at the first forming stage was chosen as a process variable, and its effect on the formability of the micro-channel at the second forming stage was experimentally investigated. Finite element simulations for the two-stage forming process were conducted to optimize the punch radius and forming depth at the first stage for improving the formability. The comparative study between the simulations and the experimental results could validate improvements in the formability by the proposed approach. In particular, this study could support the existence of an optimum forming depth at the first forming stage. Based on the simulation results, a mathematical model was established to identify the dominant factor needed for formability improvement and to propose a methodology for the process optimization of the multi-stage forming.     

Dynamics of hydrogen bubbles formed at a laser-induced microstructure on a Ni electrode during hydrogen evolution reaction

We perform the optical detection of hydrogen bubbles formed at a laser-induced microstructure on a Ni electrode during hydrogen evolution reaction, and study the dynamics of individual bubbles. Using the side-illumination technique to take both images of the bubbles and microstructure on a polished electrode we successfully correlate the bubble forming sites and surface morphology with an accuracy of ～μm, and find that there are more than a few bubble forming sites at the periphery of the single microstructure. Interestingly, the responses of those sites to the current density are different, and as the current density increases more sites become active to form bubbles. Under the constant current operation the growth rates and formation periods of the bubbles are different at different sites within the single microstructure. These findings imply that a subtle local structure within a single microstructure greatly matters to the bubble forming activity of the sites.     

锯末制备生物质成型燃料的试验研究

分别采用冷压成型和炭化成型工艺以锯末制备生物质成型燃料。冷压成型工艺主要考察原料水分、成型压力对燃料的成型性能影响。试验结果表明:原料水分为12%~16%,成型压力为60 MPa的条件下能够制得成型性能较好的生物质成型燃料,其密度与抗跌强度分别能够达到0.94 g/cm3和99%;炭化成型工艺主要考察混合料水分、无烟煤配比、J型粘结剂添加量、成型压力对燃料的成型性能影响。试验结果表明:无烟煤配比为50%、混合料水分为30%、J型粘结剂添加量为8%、成型压力为45 MPa的条件下能够制得成型性能较好的优质生物质成型燃料,其密度与抗跌强度分别为0.93 g/cm3和99.3%。     

燃气预混燃烧系统的优化设计与调试

系统地介绍了燃气全预混混合器的种类和预混燃烧系统的各种类型，重点叙述了用于玻璃棉成形用离心机加热系统和玻璃料料加热系统的燃气混燃烧系统的优化设计与调试情况，对预混燃烧技术进行了全面回顾，简要地分析了燃气预混燃烧技术的应用前景。     

Micro-roll forming of stainless steel bipolar plates for fuel cells

Stainless steel bipolar plates for use in proton exchange membrane (PEM) fuel cells have been identified as a lighter and cheaper alternative to graphite plates. Current manufacturing of metal bipolar plates by hydroforming or micro-stamping leads to excessive stretching of the material and therefore limits the channel depths that can be formed. Low channel depths for the bipolar plates will result in low overall fuel cell efficiency. In comparison, the bending-dominated deformation mode present in roll forming provides the potential to form metal bipolar plates with less thinning and to greater channel depths. In this work, the roll forming process is employed for the first time to form thin stainless steel sheets to micro-scale channel sections of the kind required for bipolar plates. This paper describes the process and machine design as well as the establishment of the forming methodology. Experimental trials are performed and the final part quality is evaluated in terms of material thinning, longitudinal bow and cross-sectional shape. The process was numerically analysed to understand the causes of the forming problems and shape defects observed in the experimental trials. The results of this work show that roll forming of micro-scale corrugated bipolar sheets is feasible. Furthermore, the findings provide a summary of both the practical difficulties and the possible advantages of using micro-roll forming to manufacture improved thin metal micro-corrugations for bipolar plates.     

激光选区烧结_SLS_成型机的粉末预热过程的实验研究

在激光选区烧结（SLS）快速成型技术中,热能的传递和吸收是一个关键的过程,热能的有效利用和均匀分布是决定SLS成形技术成败的重要因素。粉末的预热是影响成型加工和成型精度的最重要因素之一,文中对成型机工作腔的一般预热方法的预热过程进行了分析,并在实验基础上获得了关于预热温度场的预热过程数学模型,该模型对于预热装置设计、SLS成型过程控制都具有重要的意义。