G206H高风压钻具用球齿的开发与应用

针对G206高风压钻具用球齿开采坚硬岩层时易出现碎片的问题,通过调整原料中碳化钨粉的配方和改进生产工艺,开发出了一种牌号为G206H的高风压钻具用球齿,其耐磨性、抗弯强度等物理性能优良,在现场凿岩试验过程中未出现碎片状况。     

国内外采煤截齿合金的现状与发展

本文论述了采煤截齿的失效形式,国内外采煤截齿合金现状(包括牌号、齿型)及发展趋势,为截齿合金的研制提供技术依据.     

凿岩用硬质合金失效分析及牌号选择

本文论述了凿岩用硬质合金的失效机理,在理论分析的基础上,研究开发出了适用于不同岩层的各种凿岩用硬质合金牌号。并且选择了适应于中硬、硬岩层使用的合金牌号GF20D进行现场试验,结果表明:在相同的使用条件下,牌号为GF20D的新型凿岩用硬质合金的材质达到国内外同类产品的先进水平。     

高效低耗复合钎具的研究和应用

近几年来,中国地质大学(武汉)研制成功具有片状和球齿钎具综合优势的新一代复合钎头和复合整钎,开始批量投入市场使用。该系列钎具是在长期、大量凿岩实践经验的基础上,运用力学和仿生学原理,对传统钎具实现了扬长避短,其钻速、寿命和硬质合金片齿有效利用率,均显著优于相应凿岩条件下目前国内外普遍使用的片状和球齿钎具。     

G308中偏粗晶粒硬质合金柱齿的研制与应用

分析了片状与柱齿合金的磨损情况。通过调整粒度、改进工艺制度成功地研制出了G308中偏粗晶粒硬质合金,通过现场凿岩试验,其使用寿命明显提高。     

φ65柱齿钎头在我局南矿的应用

本文扼要介绍了锡矿山南矿使用φ６５柱齿钎头凿岩及其修磨情况，总结了柱齿钎头凿岩的实践经验，分析了它在我局推广应用的前景。     

硬质合金柱齿钎头压嵌时齿裂原因探讨

一、问题的提出 由于柱齿钎头具有较高的凿岩效率,使得柱齿钎头在我国得到迅速的普及和发展,目前全国约有近二十多个钎头生产厂家在生产这类钎头。由于发展过快,各钎头厂家的生产水平显然是不一样的,在一段时间内,听到一些钎头生产厂家反映,硬质合金柱齿钎头在嵌齿时发现硬质合金柱齿开裂的现象,有的是在冷嵌时发生的,有的在热嵌时也有裂齿现象产生。合金柱齿压嵌时开裂,造成了钎头生产中的最终废品,从而严重影响着钎头厂家的经济效益与社会效益,而且也严重地威协着企业的信誉和竞争能力。     

硬质合金柱齿钎头断齿原因的分析

一、柱齿合金钎头失效的原因 七十年代初,由于高效大功率液压凿岩机的迅速发展把柱齿合金钎头推上了历史舞台,并形成与片状合金针头对抗、竞争的局面,有的还认为柱齿合金钎头有可能取代片状合金钎头。     

球齿钎头工艺与结构分析试验报告

对国内外的部分球齿钎头的失效样进行了材质分析，探讨了球齿钎头早期失效的原因及其斜角与受力的关系。     

硬质合金中WC相的塑性变形

用两种不同的原料制造同种牌号的硬质合金，并对其微观组织进行了TEM分析，通过对电子衍射花样的标定，确定了WC相中存在W2C、WC1-x等相。同时对两种合金施加了一定的应变，研究了其滑移、孪生变形特性，结果表明，当WC为单一相时，WC相能产生孪生-滑移协调变形，从而具有较高的塑性。这种高塑性合金，可满足凿岩领域的使用要求。     

A STUDY OF THE FACTORS CONTROLLING GRAIN SIZE IN SINTERED HARD-METAL

Abstract

Previous experimental work concerning the grain growth observed during the sintering of tungsten carbide–cobalt alloys is reviewed. Particle-sizing methods suitable for the examination of hard-metal powders are described, and techniques for the evaluation of the carbide grain size in the sintered compacts are discussed.

By using a Model A Coulter Counter to examine the size distribution of the carbide grains (obtained from the milled hard-metal powders by dissolution of the cobalt with hydrochloric acid), and by counting techniques on electron photomicrographs of carbon replicas of the sintered compacts, it has been established that the increase in grain size during sintering is quantitatively related to the carbon content of the material after pre-heating. The results presented indicate that the cobalt content exerts little influence on the average grain size of the sintered structures A cobalt content >10% by weight is shown to exert a strong damping effect on the rate of comminution during milling.

The linear relationships between the specific surface area of the carbide grains in milled powders (obtained using a Perkin–Elmer Sorptometer) and the specific surface of the carbide phase in sintered compacts are given. The influence of sintering temperature and time on average grain size and contiguity in a commercial alloy is shown. Some preliminary work indicates that the morphologies of the initial carbide powders may be important factors with respect to the grain size of sintered hard-metal.     

Influence of the density of zirconium carbide compacts on the density of sintered specimens

Summary The article presents the results of an investigation into the influence of the density of starting compacts on the density of sintered specimens. Zirconium carbide powders of different specific surfaces were used as starting materials. It is shown that the influence of the density of starting compacts can be quantitatively estimated when coarse powders of low activity are employed. In the case of fine powders, whose activity stimulates the sintering process, it is virtually impossible to evaluate quantitatively the influence of the density of starting compacts on the density of sintered parts.Translated from Poroshkovaya Metallurgiya, No. 1, pp. 14–16, January, 1968.     

Investigation into the compaction of nanopowders and micropowders of silicon carbide in high-pressure apparatus

The results of the investigation into the compaction (sintering) of silicon carbide nanopowders and micropowders in a DO-138 high-pressure apparatus are presented. Compaction modes for both types of materials are identical (a pressure of 3.5–4.0 GPa, a temperature of 1600—1700°C, and a holding time of 10 s). The influence of cladding of SiC nanopowders and micropowders with titanium and titanium nitride on the properties of compacts (cakes) formed under the same sintering modes is investigated. It is established that, when compacting the silicon carbide nanopowder, cakes differ in regards to higher density, hardness, and lower porosity compared with the samples made of finely dispersed technical silicon carbide. A higher activity of titanium relative to SiC makes it possible to chemically associate the grains of the latter due to the formation of intermediate layers of titanium carbide between them. The resulting ceramics possesses a higher density, hardness, and wear resistance. The wear resistance of synthesized composites based on nano-SiC is higher than for a polycrystalline material based on silicon carbide micropowder by a factor of 4.5.     

Effect of application of ultrasound during pressing on the structure of tungsten carbide base materials

Conclusions An investigation has been carried out to determine the effect of USV on the structure of WC base compacts. The action of USV applied during pressing comminutes the tungsten carbide particles and decreases the porosity of the compact and hence the volume of infiltrating material, which brings about an increase in density. Application of USV promotes a more uniform distribution of the components in VK15 compacts.Translated from Poroshkovaya Metallurgiya, No. 9(237), pp. 35–38, September, 1982.     

THE PROPERTIES OF POROUS NICKEL PRODUCED BY PRESSING AND SINTERING

Abstract

The effects of compacting pressure and of sintering temperature and time on the properties of porous sintered nickel compacts have been studied, using three carbonyl and two reduced nickel powders. For all five powders, the density of the green compacts and the porosity of the sintered compacts were linearly related to the log compacting pressure. Similar relationships with pressure were observed for strength and electrical conductivity.

Photomicrographs of sections through the sintered compacts made from the reduced nickel powders show that there are pores in two different size ranges, originating from the porosity between the original powder particles and the pores within the particles. It is concluded that sintered compacts from all five powders containing 40–50% porosity have adequate strength and conductivity for use in fuel-cell electrodes.     

STUDIES OF THE SINTERING AND HOMOGENIZATION OF NICKEL-COPPER COMPACTS

Abstract

Studies are described of the progress of sintering and alloying in compacts of similar compositions made from nickel-coated copper, copper-coated nickel, and mixed nickel and copper powders. Density losses observed in the early stages of sintering were lower in magnitude and were more quickly recovered in the case of the composite powder compacts. Alloying by diffusion at both 1900 and 2200°F (1040 and 1205°C) progressed most rapidly in compacts prepared from nickel-coated copper powders, and the probable reasons for this observation are discussed in detail. Electrical resistivity was used to follow homogenization of the compacts, and samples were rendered nearly 100% dense by cold working and annealing before making resistivity measurements. Resistivity / sintering-time curves for dense specimens showed no maxima of the type reported by earlier investigators for porous compacts, which were attributed to alloying effects.     

DISSIMILAR-SURFACE CONTACTS AND THEIR INFLUENCE ON SINTERING CHARACTERISTICS OF POWDER COMPOSITE COMPACTS

Abstract

In compacts containing metal and oxide particles, metal/oxide surface contacts modify the diffusional processes. Different distributions of such dissimilar-surface contacts and their influence on the sintering characteristics of some metal-oxide compacts are considered.

By selecting appropriate volume fractions and diameters of matrix and second-phase particles, structures containing different types of dissimilar surface contact distribution have been produced. Isochronal sintering of these structures clearly demonstrates that (a) the presence of chemically inert second-phase particles always hinders densification of the composite, (b) the sintering densification (for a given volume fraction of second-phase particles) is a strong function of (d_m/d_s), where d_m and d_s are the diameters of the matrix and second-phase particles, respectively, and (c) the nature of dissimilar-surface contact distribution has a significant effect on the densification of the composite.     

粘结相对原位合成TiC钢结硬质合金组织结构和性能的影响

以钛铁粉、铬铁粉、铁粉、胶体石墨和镍粉等为原料,原位合成了TiC/Cr18Ni8、TiC/Cr19Al3和TiC/Ni40钢结硬质合金,并用扫描电镜、X射线衍射仪和洛氏硬度计、拉力试验机等对不同粘结相所制备的试样进行了组织结构分析和物理力学性能检测.结果表明:钢结硬质合金主要相组成为TiC、Fe-Cr-Ni和Fe-Cr固溶体,TiC晶粒细小,形状较为规则;粘结相对原位反应合成的钢结硬质合金的密度、硬度和所合成的TiC晶粒有较大影响,在相同烧结条件下TiC/Ni40钢结硬质合金的密度和硬度比TiC/Cr18Ni8和TiC/Cr19Al3钢结硬质合金的高,但TiC/Ni40钢结硬质合金中所合成的TiC晶粒比TiC/Cr18Ni8和TiC/Cr19Al3钢结硬质合金中合成的TiC晶粒偏聚现象严重.TiC/Ni40钢结硬质合金的硬度为60～70.5HRC,TiC/Cr18Ni8和TiC/Cr19Al3钢结硬质合金的硬度多在20～50HRC之间.三者的抗弯强度为960～1452MPa.     

Finite element investigation of backbone binder removal from MIM copper compact

Abstract

Finite element (FE) model based on kinetic analysis was developed to describe the thermal debinding process of previously solvent debinded metal injection moulded (MIM) copper compacts. Thermophysical properties (specific heat, density, thermal diffusivity and thermal conductivity as a function of temperature) of MIM copper compact were measured using differential scanning calorimeter, laser flash analyser, thermogravimetry analyser and pushrod dilatometer. The proposed model is solved numerically to study binder removal and binder distribution during thermal debinding. The investigations included the analysis of residual (backbone) binder content for cylindrical MIM copper compacts at different temperatures and positions. The FE calculations are strongly based on measured thermophysical data and kinetic analysis of copper system. The FE simulated and experimental results were compared to validate the underlying FE model based on FE temperature field calculations. Drawing the real furnace temperature conditions in finite calculation can result in obtaining more accurate data.     

Microstructural changes in Mo steels during sintering and effect on electrical conductivity

Abstract

An electrical conductivity measurement method was used for studying the sintering mechanism and microstructural changes of low alloyed PM Mo steels in a temperature range between 600-1300°C. The influences of alloying method (elemental or prealloyed), Mo content (1·5 and 3·5 wt-%), and sintering temperature were investigated. The results show that the effects of, for example, formation of Mo carbide(s), ferrite-austenite phase transformation, as well as liquid phase formation during heating of the steel compacts can be detected by the technique cited. Mo dissolution during sintering of compacts from mixed powders results in a decrease of the conductivity with increasing sintering temperature while compacts from Fe-Mo prealloyed powders exhibit the standard behaviour of higher conductivity after sintering at higher temperature. Moreover, the relationship between Mo dissolution, formation of sintered contacts, and mechanical properties was demonstrated to assess the viability of the conductivity measurement method for studying the sintering behaviour of PM materials and its influence on physical and mechanical properties. An approach was also demonstrated for relating the conductivity to the microstructural parameters, e.g. total porosity and contiguity between solid phase, that would be useful for predicting relative changes in mechanical properties dependent on porosity and pore morphology.