稀土元素在化学热处理中的催渗和扩散机理研究

稀土元素的特殊电子结构(4f)决定了它具有很高的化学活性,在化学热处理中能起到活化催渗作用,显著提高渗速;稀土元素被渗入钢件表层,有效地改善了渗层组织和性能.从化学热处理的基本过程入手,简要介绍了稀土在化学热处理中的作用,着重分析了稀土元素的活化催渗和扩散机理.     

稀土化学热处理的研究与生产应用前景

本文以大量研究结果为根据,明确指出稀土元素在化学热处理过程中具有显著的催化与微合金化的双重作用。一方面可使渗碳、渗氮、碳氮共渗、渗金属或多元共渗等工艺过程加快,或者可使渗入温度大大降低,另一方面稀土渗入后可使沉淀的第二相细化和弥散分布,从而使金相组织和性能得到相应改善。稀土将给化学热处理带来新的活力,从而获得巨大的技术经济效益。为此,广大热处理工作者应充分注意和开发利用。     

钢的稀土氮碳共渗技术研究进展

稀土元素对氮碳共渗渗层的硬度、耐磨性等性能的提高起到了积极的作用,稀土在氮碳共渗中的作用及相关机理有待进一步研究。通过参考现有国内外报道的试验及机理研究,对钢的稀土氮碳共渗的发展过程、类型及稀土的加入方式、在共渗过程中的作用机理、对渗层及基体力学性能的影响进行了综合分析和总结。对钢的稀土氮碳共渗存在的问题进行了探讨,并给出了一些建议。     

稀土在金属表面处理工艺中的应用技术(1)——稀土的概念和基本情况

介绍了稀土的概念以及稀土元素原子结构状态,并介绍了稀土元素的物理、化学性能和常用稀土化合物的制备方法;同时简述了稀土在金属表面处理工艺应用中的关键事项.     

稀土配合物的摩擦学研究

为开拓稀土化合物在摩擦学中的应用这一新领域,研制了硫配位和氧配位的含稀土元素La、Pr、Sm、Eu、Gd等的稀土化合物作为润滑油的抗磨减摩添加剂。采用质谱、核磁共振波谱、红外光谱、紫外光谱等方法,对两类稀土化合物进行了结构表征。研究表明,所研制的稀土化合物具有优异的油溶性、抗氧抗腐性和抗磨减摩性能,在润滑油中具有巨大的应用潜力。稀土化合物的润滑性能表现出一定的规律,即对六方晶系的稀土金属而言,其六方晶系的晶轴c越长,相应稀土化合物的抗磨减摩性能就越好。采用俄歇电子能谱(AES)、扫描电子显微镜(SEM)、X-射线光电子能谱(XPS)等方法,对稀土化合物的抗磨减摩机理进行了系统的研究,结果发现,稀土化合物具有优异抗磨减摩性能的主要原因来自两方面:一是在摩擦表面生成含稀土元素的多相表面润滑保护膜提高减摩性能;二是在摩擦亚表面形成稀土摩擦扩散层,使金属摩擦副材料的硬度提高,耐磨性能改善。研究还发现,在摩擦过程中,稀土元素可促进含硼元素的润滑添加剂中硼元素向金属摩擦副材料基体内扩散,增大摩擦渗硼层的厚度和硬度。在此基础上提出并论证了“稀土摩擦扩散”和“稀土摩擦催渗硼”的新观点,实现了“原位摩擦化学处理和化学热处理在本质上异曲同工”的基本设想,丰富了摩擦学理论体系     

齿轮用钢稀土碳氮共渗层摩擦学性能研究

研究了稀土元素对齿轮钢碳氮共渗过程及其摩擦磨损性能的影响.结果表面:稀土对齿轮钢碳氮共渗过程有明显的催渗作用;稀土在碳氮共渗中渗入钢表面起微合金化作用改善了渗层组织;稀土碳氮共渗处理后的抗干磨损性能及抗滑动磨损性能均明显优于普通碳氮共渗处理.     

汽车齿轮热处理工艺的研究进展

综述了汽车齿轮制造中热处理的主要工艺,重点介绍了预备热处理工艺、渗碳、碳氮共渗、渗氮和感应淬火工艺及其进展,简述了激光淬火、低压真空渗碳、稀土共渗等汽车热处理新工艺及应用现状,最后从高品质、低能耗、环保和智能化方面展望了汽车热处理工艺的发展方向.     

稀土元素对碳氮共渗过程中渗层碳氮浓度的影响

本文研究了稀土元素对碳氮共渗过程中渗层浓度的影响。试验结果表明,稀土可使共渗表层碳氮浓度有所提高,渗层深度增加。用电子探针能谱测出渗层沿表面的碳浓度分布曲线,从而进一步证实了稀土的活化催渗作用。     

稀土元素对中碳钢组织、力学性能和渗氮的影响

在一种中碳钢中通过添加微量稀土元素,研究稀土微合金化对钢的微观组织、力学性能以及在渗氮热处理条件下对渗层的影响.结果表明,添加稀土后,长条状的MnS夹杂和粗大块状的A12O3转变成小球状的稀土硫氧化物夹杂;铁素体的含量降低,并促进细小片层结构的珠光体形成;冲击性能提升126％以及塑性提高10％;渗氮处理后,添加稀土能显...     

稀土催渗对耐蚀氮化的影响

针对Q235钢采用常规气体氮化,其耐腐蚀性能日渐不能适应工程应用要求的问题,探索了添加稀土催渗剂对Q235钢进行稀土催渗氮化的方法.详细研究了渗氮工艺对氮化层厚度的影响.测量了渗氮试样表层硬度沿渗层深度的分布及耐蚀性能与渗氮工艺的定量关系.所有实验与观察均为稀土与常规2种渗氮试样在相同条件下平行操作并做对比分析.采用X光荧光谱仪测量了渗层稀土元素的分布.用X射线衍射仪测量了渗层的相组成.用金相显微镜观察了2种渗氮试样的显微组织.研究结果得出,稀土催渗氮化比常规氮化显著增加了氮化层的厚度,其显微硬度与耐腐蚀性能大幅提高.600℃下渗氮2 h为最适宜的稀土氮化条件.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...