Borided Hot-Pressed Powder Materials Based on Iron. Part 2. Effects of Hot Pressing Conditions on Surface Quality and Properties of Borided Powder Materials

Hot pressing is considered for borided and unborided powder blanks. In the hot additional pressing of unborided steel compacts, protection from decarburization is required. The hot pressing of borided blanks should be conducted at 1200°C in the presence of liquid eutectic phase. This produces good quality in the borided layer. Cracks do not arise at the ends of the blanks. The cracks that arise on the side surfaces at the start of deformation are filled by liquid phase in the final stage. The best conditions have been established for heating the blanks made by solid-phase and liquid-phase boriding.     

Borided Hot-Worked Powder Materials Based on Iron. Part 3. Wear Resistance and Mechanical Properties

The wear resistance of borided powder materials is studied. The maximum wear resistance with dry friction is obtained with carbon-free iron powder borided before hot forging. For abrasive wear operating conditions it is preferable to use borided carbon steel after heat treatment. It is established that coating billets with nickel before boriding provides an increase in wear resistance. Nickel promotes the formation of borides FeB and NiB with high microhardness. The mechanical properties of borided materials are studied.     

Powder Metallurgy Wear-Resistant Materials Based on Iron. Part 2. Materials Hot-Pressed from Porous Compacts

We continue our review of the data in the literature on the development of compositions and a technology for the manufacture of iron-based wear-resistant sintered materials. Analysis of the data shows that methods based on hot working of sintered porous compacts by pressure (hot forging, extrusion, etc.) are suitable for producing high-quality wear-resistant materials with superior strength and operating characteristics when working under high loads.     

Powder Metallurgy Wear-Resistant Materials Based on Iron. Part 1. Materials Prepared by Sintering and Infiltration

Available information on the composition and methods of production of iron-based powder metallurgy wear-resistant materials is reviewed. It is shown that most developments in this field are based on the principle of obtaining wear-resistant material by the creation of a pseudoalloy with a clearly defined heterogeneous structure, in which the microhardnesses of the base material and a hard phase are substantially different. In addition to traditional methods, including pressing and sintering porous ingots and (in some cases) infiltration with a lower melting alloy, methods based on hot working sintered porous ingots under pressure have recently found wider application.     

马钢氧化铁粉综合评析

氧化铁粉是铁氧体磁性材料的主要原料.介绍了马鞍山钢铁股份有限公司氧化铁粉质量状况及其物理、化学性能指标情况.     

Layered Powder Metallurgy Wear- and Corrosion-Resistant Materials for Tool and Tribological Applications. Structure and Properties

Three-layered non-tungsten hard alloys for tool applications of the type KKhNFT5 KKhNFT25 KKhNFT5 and layered powder metallurgy materials for tribological applications with a working layer of composites based on stainless steels were investigated. Basic requirements for the creation of wear- and corrosion-resistant powder metallurgy materials for tool and tribological applications were formulated. These mainly concern their composition and structure.     

Features of Compaction Kinetics for Powder Materials under Nonisothermal Conditions. Part 2. Existence of Critical Specimen Dimensions during the Preparation of Highly Compacted Materials

On the basis of a numerical solution of the problem for nonisothermal compaction and cooling of viscous compressible materials within a cylindrical chamber the effect of thermal factors and specimen geometrical dimensions on the characteristic times for two autonomous processes is analyzed: spatial propagation of a compression zone through a specimen from layer to layer and temporary additional compaction of material within the compression zone itself. It was revealed that the effect of retarding compaction (induction period) increases with distance of a specimen cross section from the moving piston as conditions for thermal insulation of the specimen ends worsen. The previously known experimental result of two critical specimen dimensions that govern conditions for preparing pore-free materials is confirmed and substantiated.     

Features of Compaction Kinetics for Powder Materials under Nonisothermal Conditions. Part 1. Compaction Kinetics in Regular and Fiber Regimes

New features of nonisothermal compaction kinetics are established: presence of an induction period during which compaction hardly occurs and the possible “explosive” nature of compaction. Numerical calculations make it possible to refine the picture of compaction in a wave regime and to separate two autonomous processes: propagation of a compression zone within the space from layer to layer and material compaction with time in the compression zone. It is shown that with an increase in the height of a compressed specimen there is a continuous transition from a regular regime to a wave regime of compaction.     

锻压技术的发展及其在新材料加工中的应用

根据锻压生产特点，在简要分析锻压设备及其控制系统的发展趋势基础上，介绍了粉末锻压、精密锻压、等温锻压等新技术及这些新技术在钢结硬质合金、铌钛高温合金钢等新材料加工中的实际应用。     

Features of Compaction Kinetics for Powder Materials under Nonisothermal Conditions. Part 1. Compaction Kinetics in Regular and Fiber Regimes

New features of nonisothermal compaction kinetics are established: presence of an induction period during which compaction hardly occurs and the possible “explosive” nature of compaction. Numerical calculations make it possible to refine the picture of compaction in a wave regime and to separate two autonomous processes: propagation of a compression zone within the space from layer to layer and material compaction with time in the compression zone. It is shown that with an increase in the height of a compressed specimen there is a continuous transition from a regular regime to a wave regime of compaction.

     

稀土在铁基粉末冶金材料中的作用综述

介绍了稀土在铁基粉末冶金材料中的作用机理,总结了到目前为止在这一领域的相关结论和研究进展。     

一种新型Ag-SnO2触头材料的制备及对性能的影响

采用化学共沉淀法和粉末热锻相结合的工艺，研制出新型的Ag—SnO2触头材料，并对其组织结构进行了观察分析，同时还测试了材料的密度、硬度、电阻率等物理性能。     

湿法制备纳米级固体粉末材料的进展

对纳米级固体粉末材料的研究与开发是当前材料领域中非常热点的课题。在纳米级固体料末材料的制备方法中 ,湿法占有非常重要的地位。根据收集到的资料及研究结果 ,对以湿法制备纳米级固体粉末材料做了比较详细的介绍与评述。     

Mechanism of Primary Purification in Zone Melting of Boron-Containing Powder Materials

We have established the regular behavior of the change in chemical composition and grain size of refractory material when sintered in the presence of a moving liquid phase under conditions including a high temperature gradient and continuous heating, and on this basis we propose a mechanism for primary purification to remove impurities from boron-containing powder materials during zone melting. We have shown that the degree of purification depends on the completeness of recrystallization of particles of the refractory material through the solvent melt, and is determined by the physical and processing properties of the original powders, the temperature and time parameters for the zone melting, the structure of the phase diagram, and the kinetics of diffusional interaction processes in the system refractory material solvent for the impurities.     

基于铁水成本的铁矿粉烧结经济价值评价方法

传统的铁矿粉烧结评价方法存在未考虑MgO、Al2O3脉石和酸性炉料的影响等缺点,本文提出了一种新的基于铁水成本的铁矿粉烧结经济价值评价方法,即在一定的炉渣二元碱度和镁铝比下,以单烧矿的铁水成本(元/t)作为铁矿粉烧结经济价值评价指标。其结果比以往的评价方法更准确可靠,能够反映铁矿粉烧结的经济效益。     

钨粉粉末体氧化动力学研究

应用流态化－动态悬浮沉降干法分级新工艺制备的分级钨粉，采用薄料层静态法，对粉末体氧化动力学进行了研究。研究表明，钨粉粉粒的氧化过程同样遵从抛物线－直线氧化机理。根据实验结果，建立了以氧化率为目标的数学模型。     

金属镁粉在铁水预处理脱硫生产中的应用

阐述了在铁水预处理中采用钝化金属镁－钙质粉剂进行复合喷吹和混合喷吹两种工艺及特点，并分析了在铁水预处理中影响金属镁脱硫率的主要因素，从而提出一个合理工艺制度。     

化学液相共沉淀制备超细氧化物粉末

简述了化学液相共沉淀法制备超细粉末的原理及其主要影响因素。     

Improvement of Powder Material Deformation Based on Controlling Contact Friction Forces

The possibility of improving forming conditions for powder materials by controlling contact friction forces is considered. It is shown that friction forces may have both a deleterious and a favorable effect on the compaction characteristics of porous billets. Examples are provided for realizing a number of compaction schemes using active friction forces.     

储能铁矿粉的还原热力学研究

研究了机械力作用下铁矿粉储能的变化规律和还原热力学.对于特定的一种球磨机,铁矿粉的粒度细化程度是有限度的,但其微观晶粒可以逐步细化直至晶粒完全无定形化.铁矿粉储能主要来自表面能、晶界能和位错能,其中贡献最大的为晶界能,表面能贡献较小.储能后,CO或H2还原Fe3O4和FeO的平衡气体浓度降低,有利于提高气体利用率;煤基铁矿粉的还原反应温度也相应降低.