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《粉末冶金学》2013,56(35):89-106
AbstractDepending on the type of rock and on the drilling procedure used in rock drilling, cemented carbide is exposed to greatly differing mechanical and thermal conditions. These influence the properties of the cemented carbide required. By means of metallographical examination of rock drill inserts used under different conditions, it has been possible to determine what type of wear mechanism is critical in each case. Two kinds of mechanisms in particular were found to have a great influence on performance. When a drill is run under conditions of high mechanical stress and high temperature, which is the condition present when drilling in highly abrasive rocks, a major factor influencing performance is the creep resistance of the cemented carbide. One way of improving this property appears to be to increase the grain size. Percussive drilling in low-abrasive rock, where the mechanical stress is moderate, gives rise to another wear mechanism. In this, high thermal stresses are induced which lead to the formation of cracks and sometimes to rupture. Thus for this kind of application good thermal-crack resistance is important. During percussive drilling in rocks, with intermediate abrasivity, both mechanisms are active, making the choice of cemented carbide for this application more difficult. 相似文献
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宋大有 《有色金属材料与工程》1997,18(2):74-87
文中以详尽的数据和事实分析了近几年世界半导体硅材料工业的发展及未来趋势。指出:欧、美、日各国的硅材料工业近几年产量增加、效益看好,仍然是各国的投资热点,大直径化的发展速度非常快,估计1998年Φ200mm硅片的产量将达到380万片/月,而且Φ300mm和Φ400mm硅片的研制已经在国际大协调的局面下启动。与此相适应,为了满足亚微米器件的需求,硅片的质量水平也在不断提高,从世界各地区的发展趋势看,存在着明显的不平衡,亚太地区显著地优于其他地区,此外,对多晶硅的大量需求与多晶硅生产能力不足的矛盾正成为硅材料工业发展的瓶颈,估计这种局面要到1997年后才能有所改观。 相似文献
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陈后定 《有色金属材料与工程》1996,(2)
详细介绍了美国及日本生产无氧铜杆的浸渍成型设备及工艺流程。该法整个过程均封闭在保护气氛中进行,采用自动控制。优点是设备占地面积小,投资小,生产能力达3.6~10t/h,产品表面光亮,拉丝断裂少,质量高。 相似文献
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针对目前钎杆用中空钢的使用寿命短问题,设计了横截面为奇数边形的正七边形中空钢。然后借助ABAQUS软件,建立了其轧制计算模型,给定中空钢在轧制过程中的一系列工艺参数,进行了热力耦合的非线性数值模拟。所得数值模拟结果变形合理,应力场和温度场分布均匀。 相似文献
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随着网络信息技术的发展,给专业图书馆文献资源建设带来了许多影响。阐述了网络环境下专业图书馆文献资源建设的变化以及相应的建设内容。 相似文献
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我国锰矿业的生产发展概况 总被引:4,自引:0,他引:4
Editorial Board 《中国锰业》1994,12(1):3-7
文章回顾了建国44年来锰矿业生产发展的进程,并对锰矿产品产量、质量进行了分析,指出了锰矿石当前生产存在的问题与对策。 相似文献
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《粉末冶金学》2013,56(24):566-581
AbstractThe stress, strain, and temperature at the interface between tool and work material during metal cutting are such as to promote seizure. Conditions of seizure normally exist over part of the interface during most metal-cutting operations. The wear processes that are significant on those parts of the interface where seizure is complete are considered separately from those in areas where contact is localized and intermittent. Examination of worn tools suggests that two major wear processes take place on cemented carbide under each of these sets of conditions. It is believed to be unlikely that abrasion plays a major role in the wear of cemented carbide tools except in special circumstances.The influence of powder-metallurgical processing variables in the production of cemented carbide tools is considered in relation to each of the main wear processes. 相似文献
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《粉末冶金学》2013,56(24):462-470
AbstractFrom studies of the friction between metal surfaces it has been possible to form a new concept of friction in relation to wear. Its basis is the fact that certain intermetallic compounds are unlikely to stick on common metals. Friction can be produced by adding a small amount of metal to the intermetallic compound and it is shown theoretically that the condition of friction without wear is then achieved. The elastic vibrations produced in the metals lead to the necessary sticking followed by shearing to cause friction. Practical results are given where the lives of clutches have been prolonged by factors of up to 100; similar improvements are gained for the brakes of trains and aircraft. New phenomena are explained that limit the life of the friction materials even though wear is negligible. 相似文献
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EMPIRICAL RESEARCH ON THE BASES AND CORRELATES OF MANAGERIAL MOTIVATION: A REVIEW OF THE LITERATURE.
REVIEWS THE LITERATURE SINCE 1959 RELATING TO THE CORRELATES AND BASES OF MANAGERIAL MOTIVATION. 2 THEORETICAL PERSPECTIVES ARE USED AS A FRAMEWORK: A NEED-HIERARCHY MOTIVATIONAL SCHEME, AND THE MOTIVATION-HYGIENE DICHOTOMY. EVALUATIONS OF THESE FRAMEWORKS ARE MADE IN THE LIGHT OF THE SUPPORTIVE AND NONSUPPORTIVE LITERATURE TO DATE. THEORETICAL AND METHODOLOGICAL OBSTACLES ARE SUGGESTED AS LIMITING UNDERSTANDING OF MANAGERIAL MOTIVATION. SUGGESTIONS ARE MADE FOR IMPROVING THE EMPIRICAL BASE AND THEORETICAL RICHNESS THROUGH: (1) THE DEVELOPMENT OF SYSTEMATIC THEORETICAL STATEMENTS ABOUT MANAGERIAL ATTITUDES AND MOTIVATION, (2) THE USE OF MORE RIGOROUS STUDY DESIGNS AND IMPROVED MEASURING DEVICES, AND (3) THE INCORPORATION OF AN INCREASED VARIETY OF POSSIBLE MODERATOR VARIABLES. (2 P. REF.) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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在扇形中深孔采矿中 ,采用单孔爆破漏斗试验 ,变孔距多孔同段爆破试验与斜面台阶爆破试验相结合 ,确定凿岩爆破参数。实践表明 ,大块率低 ,爆破效果好 ,出矿能力大 ,经济效益明显 ,试验确定的凿岩爆破参数准确、实用 相似文献
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研究了锻造对飞机刹车副动片钢对偶材料摩擦磨损性能与组织的影响,结果表明:锻造提高了动片钢对偶材料的耐磨性和抗收缩性。 相似文献
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本文介绍了澳大利亚铁矿资源概况、生产铁矿石的主要企业、铁矿石的物理化学性能及对铁矿石的基本评价,指出了该国铁矿迅开发的原因及今后的发展趋势。 相似文献