SF-1填充PTFE表面层配方的摩擦特性研究

以填充改性PTFE为表面层、青铜粉为中间层、背面为钢板的SF-1三层复合自润滑轴承材料，在工程上的应用日益广泛。该材料表面层的配方和性能，是整个材料的摩擦特性的决定因素。本文针对高压齿轮泵轴承的应用场合，设计了几种填充PTFE的表面层配方，在Amsler摩擦磨损试验机上测定不同表面层配方的SF-1材料的摩擦和磨损性能，并优选出两种配方的SF-1材料制成滑动轴承试样，在轴承试验机上进行极限PV植试验评价，同时讨论了SF-1表面层配方中固体润滑剂对摩擦特性的影响及耐磨机理。     

激光硬化粉末烧结钢的组织结构及耐磨性

两种Fe-Ni-Cr-Cu-Mo-C系粉末烧结钢宽带激光硬化处理表明,激光硬化的粉末烧结钢表面层的组织结构由马氏体、贝氏体、残余奥氏体和游离态石墨等组成.激光硬化处理显著改善了粉末烧结钢的耐磨性.     

超声振动场对热浸镀稀土铝表面层厚度影响的动力学分析

用溶剂法制备了稀土铝镀层，采用金相显微镜、扫描电镜观察测定了超声场对热浸镀稀土铝表面层厚度的影响，绘制了表面层厚度变化的动力学曲线。研究得知，稀土铝镀层由表面层和过渡层组成。通过厚度测定发现，过渡层厚度遵循抛物线生长规律，而表面层的厚度变化则明显不同。随着热浸稀土铝时间的延长，表面层厚度经历了先减少至谷值，然后增加到峰值，又减少至稳定值的3个阶段。每一阶段控制厚度变化的因素不同，将其变化过程分为由凝固-重熔控制的第Ⅰ阶段，由浸润-凝固控制的第Ⅱ阶段和完全由浸润控制的第Ⅲ阶段。不管是否施加超声场，表面层厚度变化的规律相似，只不过施加超声场后表面层厚度有不同程度的减小，同时表面层的组织变得更加均匀。     

拉拔钼丝表面微缺陷的形成及控制

描述了拉拔钼丝表面沟槽和凹坑两种主要微缺陷及其形成原因,通过分析拉拔钼丝的表面层结构,明确提升钼丝拉拔加工过程中圆周受力的均匀性和润滑的有效性是提高钼丝表面质量的有效途径。在实际生产过程中,通过控制拉拔钼丝原料的表面金属微堆叠和均匀化表面组织结构,同时提高拉拔模具孔型的对称性和提高设备的精度能有效提高钼丝拉拔过程的圆周受力均匀性;通过控制石墨乳的粒度分布、粘度和分散度,并在加工过程中合理设置石墨乳比重和加热方式,能有效提高拉拔过程中石墨乳润滑的有效性。为高表面质量的高端钼丝国产化生产工艺的制定提供参考借鉴。     

双频淬火时轧辊表面层内的温度分布测定

在５０Ｈｚ／２５０Ｈｚ双频淬火机床上，对φ４２０轧辊表面层内的温度分布进行测试。结果表明：在双频淬火过程中，轧辊表面层内的温差可达６０℃，最高温度发生在距辊面１０－１５ｍｍ处。在轧辊辊面之下２０ｍｍ处的平均冷却速度为１．９℃／ｓ。     

短墩基础在旧房加层改造中的尝试

对表面层土较软弱，而下面为含砾砂层基础砖混结构加层，基础设计尝试运用短墩处理。     

石墨添加量对热压镍铬钼-石墨复合材料性能的影响

本论文研究了热压制备添加石墨的镍铬钼复合材料的力学性能及摩擦磨损特性。结果表明，随着石墨添加量的增加，复合材料的抗拉强度和伸长率逐渐下降，硬度逐渐上升，摩擦系数逐渐变大。其中添加石墨后的复合材料硬度明显高于不添加石墨的基体合金硬度，石墨添加量（质量分数）为1％时复合材料的磨损率最低。新材料中由于添加石墨而形成的硬质碳化物及游离石墨的存在，正是这种力学性能及摩擦磨损变化规律的根本原因。     

冶金新技术20行

铁粉生产方法的改进新日铁于1989年11月22日获得一项铁粉生产新方法的专利。此方法的要点是,用转炉炉尘作为原料,将它们进行球磨并分级,使所得到铁粉的表面层氧化,将氧化后的铁粉表面层还原成多孔的铁粉表面层,而形成多孔性还原铁粉。最好的炼钢转炉炉尘所生产的铁粉的成分是(按重量百分比):C为0.5％,Fe为95.8％,FeO为1.72％,Fe_2O_3为0.67％,所得铁粉的颗粒往往是椭球形的。由于所生产的铁粉的表面层是一种粗糙的多孔的表面层,因此,这种铁粉的单位表面积增加了,从而具有好的可压实性和良好的烧结     

放电等离子烧结制备镍掺杂石墨-铜复合材料组织性能研究

通过超声波分散结合行星球磨对复合粉末进行混料，利用放电等离子烧结技术（SPS）制备镍掺杂石墨-铜复合材料。运用扫描电子显微镜（SEM）、X射线衍射（XRD）、硬度计和摩擦磨损试验机等方法，研究了不同镍掺杂含量对石墨-铜复合材料组织和力学性能的影响。结果表明:通过该工艺制备石墨-铜复合材料石墨均匀分散于铜基体，并与铜基体形成良好的界面结合。随着镍掺杂含量的增加，石墨-铜复合材料相对密度和硬度逐渐增加。当镍掺杂含量（指质量分数）为7.0%时，石墨-铜复合材料相对密度为95.2%，HV_0.5硬度为53.4，摩擦系数相对较低，磨损表面较光滑，此时综合性能较好。      

从炼钢的石墨结块产物中回收片状石墨

作为促进自然资源保护和再利用的尝试性研究的一部分，美国矿业管理局开发出一种从名为石墨结块的炼钢废料中生产优质片状石墨的工艺。现代炼钢生产中产生的石墨结块是由石墨、脱硫渣和铁组成的混合物．是从进入氧气顶吹转炉的铁水上扒出的。结块物料经筛分及水力分级综合处理后．可获得含石墨70％以上的精科。精科再经过酸浸，即可生产出纯度为95-99％和10目以下的片状石墨产品。工业石墨用户反映，用石墨结块生产的石墨产品，在多数场合下是天然石墨的适用替代物。     

高炉炉缸凝铁层物相分析

在高炉炉缸破损调研的基础上对高炉炉缸耐火材料热面凝铁层进行取样,利用扫描电子显微镜、物相分析等分析手段揭示了凝铁层的物相组成,并运用Thermol-calc热力学计算软件结合TCFE8数据库对铁水中石墨碳的析出温度及析出相分数进行了计算,最后揭示了炉缸凝铁层物相的形成机理.结果表明,高炉炉缸凝铁层主要由Fe相和石墨碳相交替分布组成,铁水成分对石墨碳析出温度影响较大,石墨碳析出温度远高于铁水凝固温度,铁水中C、Si元素含量对石墨碳析出相分数影响较大,而石墨碳析出相可增大铁水黏度11.9%.凝铁层中石墨碳的析出主要是由于Fe-耐火材料界面温度低于石墨碳析出温度,使得铁水中C不断向耐火材料热面迁移,进而形成Fe-C交替的分层结构.     

Effectiveness of reducing agents during sintering of Cr-prealloyed PM steels

Abstract

Development of strong inter-particle necks requires successful removal of surface oxides, present on the powder particles, during the initial stages of sintering. In the case of water-atomised powder prealloyed with chromium, the surface oxide consists mainly of an iron oxide layer with some more stable fine particulate oxides. The formation of sufficiently strong inter-particle necks requires as a minimum full removal of the iron surface oxide layer. This can be achieved by gaseous reducing agents (e.g. H₂, CO or a mixture of both) or by carbon, typically admixed in the form of graphite. The reducing power of various sintering atmospheres (active gas content ≤10 vol.-%) and their combined effect with graphite has been investigated by a thermal analysis technique. Results indicate that a combination of a dry hydrogen-containing atmosphere and fine graphite allows successful sintering of chromium alloyed PM steels.     

Structure of fullerene-containing deformed powder steels

The effect of dynamic hot compaction (DHC) and intensive plastic torsional deformation (IPTD) on the structure and properties fullerene-containing powdered compositions of Fe graphite and Fe cast iron has been investigated. It is found that sintering Fe graphite samples results in the synthesis of fullerenes in their surface layer and a fullerene-containing phase is observed in their body after DHC as well. DHC results in an increase in the wear resistance of the Fe graphite composition. It is shown that a 6.16 Å line appears on diffractograms of all examined samples (both Fe graphite and Fe cast iron) as a result of IPTD. Scanning probe microscopy found that the elasticity modulus of samples of iron graphite increases from 50–58 to 67–91 GPa and local hardness increases from 10–19 to 137–155 GPa because of IPTD. The elasticity modulus of iron-pig-iron samples also increases from 63 GPa before IPTD to 55–109 GPa afterwards. A wide scatter in values of this index testifies to the inhomogeneity of the structure formed in the course of deformation.     

高炉内铁?焦界面的渗碳润湿行为研究

高炉内铁水渗碳过程是影响冶炼效率及未饱和铁水对炉缸炉衬侵蚀的重要因素。本文通过高温真空润湿性测试装置模拟了高炉炉缸区的铁水渗碳反应,分析了不同碳质量分数（3.8%、4.3%、4.8%）的Fe?C熔体与质量分数为99.9%的石墨基体在高温下界面间的润湿反应,同时利用扫描电镜（SEM）和能谱仪（EDS）研究了渗碳界面的微观形貌及渗碳距离。结果表明:界面接触角随着Fe?C熔体中碳含量的增加而变大;熔化过程中,接触角随着反应时间延长而减小,并最终趋于稳定;4.8%碳质量分数的Fe?C熔体中由于含碳量已至饱和,处于不润湿状态。扫描电镜分析显示,Fe?C熔体与石墨基体的接触界面形成了“球帽状”凹陷,凹陷半径与体积随碳含量的增加而减小。能谱线扫描分析显示,随着Fe?C熔体中初始碳含量的增加,石墨基体中的碳素溶解量减少,渗碳效果变差,良好的润湿性有利于碳的传质。通过计算表面能发现,石墨基体中碳素溶解进入Fe?C熔体后,有效减小了两者之间的表面能,使得表面张力减小,接触角在熔化期间递减。      

Microprocesses of metal dusting on nickel and Ni-base alloys

Microstructural and microchemical investigations were carried out on nickel and Inconel 600 after exposure to strongly carburizing atmospheres at temperatures of about 600 to 650°C to study their metal dusting behaviour. Contrary to iron and low-alloy steels, where metal dusting proceeds via the formation and disintegration of a metastable carbide M₃C, both nickel and Inconel 600 directly disintegrate. Inside the metal this disintegration proceeds by formation of thin graphite filaments of nearly 10 nm in diameter, the atomic basal planes of which are oriented perpendicular to the surface thus effecting a high reactivity at the growth front. Subsequently, fine particles or larger parts of the metal surface layer are released, which are buried in the deposited graphite layer on the surface. In case of Inconel 600, containing Cr with mass contents of about 15%, the disintegration can be delayed by the formation of a chromium oxide layer, but no safe protection against metal dusting is obtained.     

Influence of ash on mass transfer and interfacial reaction between natural graphite and liquid iron

The interfacial reaction is a factor that plays an important role in governing the rate of many metallurgical processes. In the direct iron smelting process, interfacial reactions of carbonaceous materials, such as coals, with molten iron is one of the key factors that dictate the rate of carbon transfer from the carbonaceous materials into molten iron and establish a carbon concentrated melt to reduce iron oxide in the slag phase. In the current investigation, wetting of natural graphite, which contains 8.8 pct ash, by iron was studied in a horizontal tube furnace at 1600 °C using the sessile drop approach to establish a fundamental understanding of the influence of ash on interactions between graphite and iron. The mass-transfer phenomena between the solid substrate and the iron droplet were studied by withdrawing the assembly at different time intervals. After the wetting experiment, the contacting surface of the iron droplet was observed by a field emission scanning electron microscope (FESEM). The components of the interfacial layer formed during the experiment were examined by energy dispersive spectroscopy (EDS). The change in the carbon and sulfur contents of the droplet at different time intervals during the wetting experiment was analyzed by a LECO carbon and sulfur analyzer. It was found that the formation of an ash interfacial layer between the carbonaceous materials and the liquid iron has a strong influence on the mass transfer and interfacial reaction. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

Microprocesses of metal dusting on iron

In strongly carburizing atmospheres iron and steels are subject to ‘metal dusting’, a catastrophic carburization, leading to disintegration into a dust of carbon and metal particles. TEM investigations of iron foils in different states of this corrosion process have clearly shown now that unstable cementite is an intermediate in the reaction. The carbide is formed at the iron surface after supersaturation (a_C > 1), its disintegration is started by graphite deposition on its surface (a_C = 1). The carbon atoms from Fe₃C disintegration are attached to the graphite planes which are vertically oriented to the cementite surface, the iron atoms diffuse through the graphite and agglomerate to small particles (～ 20 nm) which act as catalysts for further carbon deposition from the atmosphere, till they are densely covered with graphite. The TEM investigations are in good agreement with preceding studies concerning kinetics and mechanisms of metal dusting.     

The role of interphase boundary adsorption in the formation of spheroidal graphite in cast iron

The interphase boundaries in gray and ductile cast iron were studied with a scanning Auger microprobe (SAM). Sulfur and oxygen were found to be adsorbed at the flake/ metal interfaces in the gray iron, while the nodule/metal and intercrystalline graphite interfaces in the ductile iron were free of foreign elements. The only magnesium detected in the magnesium modified ductile iron was combined with phosphorus and sulfur as a compound. A model is presented which proposes that Fe−C−Si eutectic alloys in the absence of surface active impurities (such as in vacuum casting of high purity materials) produce nodular graphite due to the inherent instability of the graphite/melt interface. The sulfur and oxygen always present in commercial alloys adsorb at the graphite/melt interface, effectively “stabilizing” the active sites on the graphite basal planes, and preventing spherulitic growth. The purpose of modifiers is to getter these impurities.     

SMRI—92型D墨铸铁玻璃模具的性能研究

本试验研究了玻璃模具用Ｄ墨铸铁的墨微组织及耐热性能。结果表明，试样断口呈银灰色，晶粒细小而致密，石墨形态为Ｄ形石墨，基体组织为细片状珠光体（〉９０％）；Ｄ墨铸铁的抗氧化、抗生长及热疲劳抗力等综合性能良好。工业性试验表明，该玻璃模具具有抗氧化、耐磨损、易修复、使用寿命长等特点，其热循环次数达７０万次，使用寿命比ＣｒＭｏＣｕ材料提高３．５倍。     

Influence of the Structure of Fe–Si–Mg–Rare Earth Modifiers on the Production of Compacted Graphite Iron for Camshafts

The structure of a modifier in two forms (ingot and chip) for the production of compacted graphite iron (also known as vermicular graphite iron) is investigated by means of an electron microscope and also by X-ray microspectral analysis. The possibility of qualitative identification of the phase composition and surface macroanalysis of the modifier particles is considered.