球形化处理铜锡粉末制备CuSn10含油轴承

以电解铜粉和锡粉为原料,通过高能球磨机进行预混,并采用球形化工艺对所制得的铜锡混合粉进行表面整形,以改善颗粒表面形貌及性能,然后通过压制、烧结工艺制得烧结青铜含油轴承。分析不同处理条件下的颗粒形貌和烧结轴承表面形貌,测定复合粉末的流动性、松装密度,以及烧结青铜含油轴承的密度、含油密度、开孔隙率、径向和轴向伸长率、布氏硬度和压溃强度(RCS)。结果表明:随球形化处理时间的延长或处理转速的提高,颗粒球形化程度提高,粉末流动性得到改善,烧结含油轴承含油率均可达到18%以上,压溃强度随粉末球形化处理时间延长或转速的提高而升高。球形化工艺中转速3 000 r/min,处理时间15 min时,可获得最佳的处理效果,烧结青铜含油轴承含油密度为6.68 g/cm3,开孔隙率为22.45%,压溃强度为220.8 MPa。     

高能球磨对碳纳米管增强铝基烧结含油轴承性能的影响

采用粉末冶金工艺制备铝粉、球磨铝粉和球磨混合粉末(添加2wt％ MWCNTs的铝粉)烧结含油轴承,测定烧结样品的性能,并研究高能球磨对粉末性能及样品性能的影响规律和机理.结果表明,球磨后粉末颗粒尺寸减小并呈薄片状或层状,MWCNTs被剪断分散后包裹在铝粉颗粒中.粉末球磨易于原子扩散促进烧结颈的形成,提高烧结样品压溃强度...     

扩散处理制备CuSn10部分合金化粉末的研究

本文通过对电解Cu粉、雾化Sn粉的部分合金化过程的研究 ,制备出适于制造高速、低噪音、微型含油轴承的CuSn1 0部分合金化粉末。采用SEM对粉末进行了分析 ,同时分析了粉末混合和生坯密度对部分合金化粉末的影响 ,并分析了扩散烧结温度、扩散烧结时间等对其工艺性能的影响     

烧结工艺对CuSn10含油轴承组织与性能的影响

研究了不同H2含量的H2+Ar烧结保护气氛和烧结时间对CuSn10含油轴承材料显微组织和性能的影响。结果表明:在720℃×90 min的烧结条件下,烧结气氛为100%Ar时,粉末颗粒表面氧化严重,烧结组织中存在大量形状不规则的孔隙,并且孔隙尺寸较大,烧结试样的含油率高而含油密度、径向压溃强度、硬度均较低,磨损量高;随着烧结气氛中H2含量的增加,粉末颗粒表面氧化物被还原,孔隙数量减少,孔隙形状趋近于球形并细化,烧结试样的含油率降低而含油密度、径向压溃强度、硬度均提高,磨损量则先减小后增大。在50%H2+50%Ar(体积分数)保护气氛下720℃烧结30 min时,不规则孔隙形状趋近球形,但孔分布不均匀且尺寸较大;延长烧结时间至60 min和90 min,孔隙细化;但进一步增加烧结时间至120 min时,孔隙数量与形态并未产生明显变化;烧结试样的含油密度、力学性能和磨损量均随烧结时间的延长而提高。     

烧结温度对Al-Cu系含油轴承压溃强度、含油率和微观形貌的影响

采用粉末冶金法制备了Al-Cu系含油轴承,研究了烧结温度对Al-Cu系含油轴承的压溃强度、含油率和微观形貌的影响规律及机理。结果表明:烧结温度显著影响Al-Cu系含油轴承的压溃强度、含油率和微观形貌;以540℃、550℃、560℃和570℃真空烧结,烧结坯分别呈现出欠烧结、最佳烧结、过烧结及熔融等不同状态;540℃烧结时,粉末颗粒之间未发生明显的冶金结合,压溃强度较低;高于560℃烧结时,烧结坯发生过烧结及熔融,收缩较大,含油率较低;550℃为最佳烧结温度,在此温度下,烧结坯发生局部熔化,粉末颗粒之间产生良好的冶金结合,微观形貌良好,压溃强度和含油率达到最佳,分别为198MPa和22%。     

粉末热锻温度对锻件密度和性能影响的研究

为了改进粉末热锻工艺,进行了相关锻造试验,选取了7个锻造压力,每个锻造压力下设定5个锻造温度,通过对每组试验的锻件试样密度、硬度和压溃强度的测试分析,根据结果绘制了7种锻造压力下,锻造温度与密度,以及由温度不同引起的密度与硬度和压溃强度关系曲线图,为选择合适的锻造温度,以及预测不同工艺条件下粉末锻件密度和力学性能提供了依据。     

CuSn10青铜粉末热压烧结行为及性能的研究

对混合、部分合金化、雾化三种不同工艺生产的CuSn10粉末,在不同温度下进行了真空热压烧结.主要研究了烧结温度对其热压烧结制品密度、硬度的影响,并通过金相测试对样品显微组织进行了分析.试验结果表明,对于真空热压烧结,在确定的烧结温度下,雾化CuSn10粉末烧结样品的密度和硬度明显高于用其他两种工艺生产的CuSn10粉末;随着烧结温度的升高,三种CuSn10粉末烧结样品的密度及硬度呈现先增加后减小的现象,当烧结温度为750℃左右时,三种CuSn10粉末烧结样品的性能最好.     

氮气保护下铝基烧结含油轴承烧结工艺优化研究

通过粉末冶金技术制备质量分数为7.5%的含铜铝基烧结含油轴承试样,研究了在氮气保护下不同烧结温度以及烧结时间对试样的微观结构和综合性能的影响,优化得到最佳烧结工艺。研究结果表明,当烧结温度超过537℃时,烧结试样发生局部熔化,液相开始生成;随着烧结温度升高和烧结时间的延长,烧结试样的尺寸收缩率以及压溃强度不断提高而含油率不断减小。当烧结温度为560℃、烧结时间为120 min时,烧结试样拥有良好的综合性能,压溃强度和含油率分别为151.3 MPa和16.7%,呈最佳烧结状态。     

不同方法制备的温压粉末形貌及工艺性能

温压粉末质量是温压工艺成败的关键，应据成品件的用途和成本要求选择不同的制粉方法。针对高密度高性能温压零件要求，研究和分析不同制粉方法对Fe-2Cu-2Ni-1Mo-1C（质量分数，％）温压粉末形貌及流动性和松装密度的影响之后，发现：用不同方法制备的粉末在形貌上有很大差异，在室温与130℃均有良好的松装密度与流动性，且多次循环加热对其流动性和松装密度都没有不良影响，而部分扩散预合金粉末的综合特性最佳。     

烧结制度对三维通孔不锈钢泡沫性能影响

研究了烧结制度对具有三维通孔网状结构泡沫不锈钢的线收缩率、开孔孔隙度、抗弯强度的影响。研究发现：随着烧结温度的升高和保温时间的延长，烧结制品的线收缩率增大，开孔孔隙度减小；随着烧结温度的升高，烧结制品抗弯强度先是增大，然后有所降低，保温时间的延长有利于提高抗弯强度，但影响没有烧结温度强烈。前驱体在1260℃温度下烧结30min，可制得孔径大小为1mm左右、具有良好三维通孔结构的不锈钢泡沫．该泡沫的开孔孔隙席为81．2％．杭弯强席为51．72MPa．     

THE INFLUENCE OF A PARTIALLY WETTING SECOND PHASE ON THE SINTERING OF SOLID PARTICLES

Abstract

A geometrical model is considered which describes the sintering kinetics between two solid, spherical particles covered by a partially wetting second phase. Conditions selected are such that the grain boundary is not penetrated by the second phase. The model is kinetically similar to the case of solid-state sintering by grain-boundary diffusion and can also be compared with Kingery’s model of liquid-phase sintering. It predicts that the sintering rate of two solid particles remains virtually unchanged when a second phase (solid or liquid) is added. An example is the sintering behaviour of SmCo₅. The applicability of the model to carbide-metal and oxide-metal systems is discussed.     

THE SINTERING OF PYROPHORIC POWDERS

Abstract

The room-temperature oxidation behaviour of reactive metal and ceramic powders is reviewed and it is shown that many materials under normal circumstances oxidize to give a limiting film thickness of ～50Å. Since the thickness of oxide films has an important bearing on sintering characteristics the control of oxidation may be essential for some materials and desirable for others.

The oxidation behaviour of uranium carbide and uranium nitride in various concentrations of oxygen and water vapour in argon is described and its effects on the sintering behaviour and composition changes that take place during sintering are considered.

Suitable handling conditions for these materials are provided by glove-boxes filled with argon; there is a brief discussion of the factors that might apply if they were used in other areas of powder metallurgy.

The application of high-purity handling atmospheres in the preparation, handling, and sintering of tungsten powders has given pellets that had densities of 95% theoretical and oxygen contents <10 ppm after sintering in hydrogen at 1550°C.     

部分扩散铁基合金粉末的压缩性及烧结均匀化

研究了（%）Fe-1.5Cu-2Ni、Fe-7MC、Fe-2Cu-0.6P部分扩散粉末（分别混入碳）试样的压缩性、烧结均匀化程度、机械性能等。实验结果表明:部分扩散粉末具有较高的压缩性,同时也有较好的烧结均匀化性能,烧结后铜、钼、磷等元素得到较均匀的分布。上述三种材料的烧结态强度分别为500、600和700 N/mm2。     

THE EFFECT OF SURFACE CHARACTERISTICS ON THE SINTERING OF URANIUM AND BERYLLIUM POWDERS

Abstract

Studies of the sintering of uncompacted uranium powders in vacuum have shown that sintering behaviour is markedly affected by the nature of the surface films on the powder. Of the variables in the powder production route that might affect the nature of the surface films, the leaching stage is the most important.

The deleterious effect of surface contaminants on the vacuum-sintering behaviour of beryllium is demonstrated. During the development of a technique for the production of a stable powder from electrolytic flake, the nature of the leaching treatment again proved to have a marked influence on the sintering behaviour of the resultant powder.

Both sets of investigations were hampered by lack of methods for identification of surface films on powders.     

替代扩散合金化粉末的粘结剂处理粉的研制

为替代扩散-合金化粉末,研制了巧妙设计的粘结剂处理的预混合粉.一类粘结剂处理的材料,符合MPIF标准35"粉末冶金结构零件材料标准"中扩散-合金化材料的化学组成范围.另一类粘结剂处理的预混合粉,是用来替代高性能扩散-合金化材料的,这些材料都是以含Mo 1.5%(质量分数)的预合金化低合金钢为基体的.考察了新材料的烧结态和淬火-硬化与回火状态的性能,并将之和化学组成相似的扩散-合金化材料进行了比较.     

铁粉特性对温压生坯密度的影响

从铁粉类型、粒度组成、化学成分和粉末显微硬度等因素对温压生坯密度的影响情况进行了系统试验,结果表明,通过控制粉末形状、粒度分布、化学成分等因素,温压可获得高压坯密度,在本试验中,经过处理的国产粉温压压制密度最高可达7.30g/cm3,接近国外粉末压制密度。     

OBSERVATIONS ON THE SINTERING OF COMPACTSFROM A MIXTURE OF IRON AND COPPER POWDERS

Abstract

Three grades of iron powder-an atomized steel powder, a sponge iron powder reduced from magnetite with carbon, and a powder reduced from mill scale with hydrogen were mixed with 3% of copper powder and pressed into compacts. The diametral dimensional changes of the compacts during sintering below and above the melting point of copper were measured, their microstructures examined, and both related to the characteristics of the powders, particularly their specific surface. During sintering below the melting point of copper, compacts of all three powders shrank. Micrographic examination showed that the copper is transported by solid-state diffusion along the surfacesand grain boundaries of the iron powder particles. During sintering above the melting point of copper, compacts of the atomized and the MH-100 sponge iron powders grew while those of the hydrogen reduced mill-scale powder shrank. This phenomenon is related to the different mode of penetration of liquid copper in the compacts from the three powders, observed in the microstructures of the compacts.     

网络对青少年人格发展的负面影响

互联网对青少年的成长发展起着促进作用的同时，也对其人格发展带来负面影响，影响其价值观的形成、品德行为使其异常，诱发一些心理问题，甚至出现人格的变异。