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侧压系数及压坯高径比对温压有效性的影响 总被引:10,自引:1,他引:9
钢铁粉末温压技术的有效性不仅取决于粉末/模具加热温度、压制压力及润滑剂的特性,而且取决于所要生产的零件的特点,如几何形状。本文通过引入温压侧压系数(β)并运用唯象的温压压制方程着重分析了压坯高径比或高径差比对温压生坯密度的影响。理论分析表明,当β值超过某值时,温压生坯密度明显降低。不同β值的压坯温压实验表明,当β=3~10,温压生坯密度随粉末/模具温度变化有一最大值;而β≥24时,无模壁润滑生坯密度随粉末温度升高而降低,而适当的模壁润滑却可保证得到690MPa下的738g/cm3的高的温压生坯密度。 相似文献
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温压是一种用加热粉末混合料与模具来提高被压制零件生坯密度的技术。加热的温度范围一般为 90~ 15 0℃。依据零件大小、粉末混合料配方及压制参数 ,与“冷”压制相比 ,采用用温压技术一般可将生坯密度提高 0 0 7~ 0 3g/cm3。可是 ,要想通过适度地提高压制温度来提高生坯密度 ,必须正确地设计粉末混合料 ,使之能在作业温度下稳定地充填阴模型腔 ,以保证压制的零件质量 (重量 )与密度均匀一致。另外 ,还必须在保持脱模力小与零件表面粗糙度值低的条件下 ,正确选择基体粉末与混入的元素粉末 ,以使生坯密度与烧结件密度都能达到最大值。要特别指出 ,润滑剂的选择是温压的关键。本文讨论了在不同的压制条件下 ,各种温压粉末混合料的性状。介绍了基体钢粉牌号和各种添加剂的数量与类型对生坯与烧结件性能的影响。着重阐述了润滑剂对生坯密度与脱模力的影响。 相似文献
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温压技术是由在加热的阴模中压制预热的粉末组成[1],已知温压有助于零件密实,从而改进烧结件的性能[2,3]。温压需要在适合温压的温度范围内进行。特别是,粉末混合粉应具有好的流动性,同时对阴模模壁有良好润滑性,以减小脱模力。在试验室和工业生产中都研究了用粘结剂处理的和未经粘剂处理的用温压技术制造的材料的性状与性能。为了确定和定量各种关键生产参数,诸如压制压力,粉末温度与阴模温度,生产速率及零件大小对生坯和烧结件特性和零件脱模力的影响,进行了专门的试验研究。依照粉末流动性与松装密度的稳定性,压制压力与温度以及压制零件的重量与密度讨论了温压的工艺性。 相似文献
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高密度铁基粉末冶金零部件制造原料的研究 总被引:1,自引:0,他引:1
温压粉末原料是采用温压成形技术制造高密度粉末冶金零件的基础和温压工艺的技术核心。高价格的进口温压粉末制约了我国高密度铁基粉末冶金零件的开发与应用,因此,必须开发出符合我国国情的温压粉末原料体系。作者根据我国资源特点,采用鞍钢产水雾化铁粉、水雾化低合金钢粉和攀枝花钢铁公司产转炉烟尘铁粉为原料,进行了制备相应体系的温压粉末原料和温压工艺参数优化的研究。以水雾化铁粉为原料设计制造的Fe-1.5Ni-0.5Mo-0.5Cu-0.6C粉末经637MPa压制,温压密度为7.46g/cm~3;压坯的回弹率为0.03%.在1150℃烧结40 min后,收缩率为0.025%。而以转炉烟尘铁粉设计制造的Fe-1.5Ni-0.5Mo-0.5Cu-0.6C粉末经686 MPa压制,压坯密度达7.35g/cm~3;以Fe-1.5Ni-0.5Mo水雾化合金钢粉为原料制造的Fe-1.5Ni-0.5Mo-1.5Cu-0.8C粉末在686 MPa时压制密度为7.35g/cm~3。这些粉末原料的设计为我国高强度铁基粉末冶金零部件的制造创造了条件。 相似文献
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用作温压基粉原料的Fe-Ni-Mo合金钢粉温压与烧结行为研究 总被引:3,自引:0,他引:3
与通常采用纯雾化铁粉和部分合金化铁粉作为温压基粉不同,作者对水雾化Fe-Ni-Mo合金钢粉作基粉的Fe-1.5Ni-0.5Mo-1.0Cu-xC(x=0.6,0.8,1.0)粉末进行了温压与烧结行为的研究.结果表明,通过设计新型聚合物润滑剂,高硬度的合金钢粉仍适用于温压工艺.当粉末和模具的加热温度分别为125和145℃时,Fe-1.5Ni-0.5Mo-1.0Cu-0.8C的温压密度较高,在735MPa的压力下进行压制,压坯密度达到7.35g/cm~3,比室温压制提高了0.19g/cm~3左右.并且,温压压坯的弹性后效比室温压制降低了40%,在1120℃烧结1h后的烧结密度为7.32g/cm~3. 相似文献
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《粉末冶金学》2013,56(2):159-164
AbstractThe effects of warm compaction on the green density and sintering behaviour of aluminium alloys were investigated. Particular attention is paid to prealloyed powders, i.e. eutectic and hypereutectic Al-Si alloys, regarding their potential applications in the automotive industry. The effects of chemical composition, alloying method, compacting temperature and the amount of powder lubricant were studied. The compaction behaviour was examined by an instrumented die enabling simultaneous measurement of density, die wall friction coefficient, the triaxial stresses acting on the powder during the course of compaction and ejection pressure. The sintering behaviour was studied via dilatometeric analysis as well as normal batch sintering. The results show that warm compaction could be a promising way to increase the green density of aluminium alloys, especially prealloyed powders, and to decreased imensional instability during sintering. Moreover, it reduces the sliding friction coefficient and the ejection force during the powder shaping process. This paper presents the significant advantages and drawbacks of using the warm compaction process for commercial PM aluminium alloys. 相似文献
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《粉末冶金学》2013,56(3):281-287
AbstractAn instrumented die was used to investigate the behaviour of metal powders during cold (ambienttemperature) and warm (up to 140°C) compaction. This instrument enables simultaneousmeasurement of density, die wall friction coefficient, the triaxial stresses acting on the powderduring the course of compaction and ejection pressure. Commercial iron, titanium, aluminium,316L stainless steel (SS) and aluminium–silicon powders were employed for investigation. Theresults demonstrated the advantages of powder preheating on the compaction behaviour of metalpowders concerning green density, dimensional changes, frictional behaviour, ejectioncharacteristics and compactibility. However, the outlines also determined that the response ofthe non-ferrous powders to powder preheating is somehow different from those of the ferrouspowders. In this context, the behaviour of prealloy aluminium–silicon powders during compactionwas found of particular interest, as their compactibility is strongly affected by powder preheating,whereas the dimensional changes after ejection decrease considerably. This article presents theeffect of cold and warm compaction on the consolidation and ejection characteristics of ferrousand non-ferrous metal powders. The influence of compaction condition (pressure andtemperature) with considering of the powder characteristics and densification mechanisms areunderlined. 相似文献
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温压压制压力强化因子及压制曲线的唯象分析 总被引:7,自引:1,他引:6
介绍了一种使用钢铁粉末室温压制回归方程建立其温压压制方程的分析方法,粉末和模具温度,装粉高度通过压力强化因子影响温压生坯密度,温压压制方程描绘的压制曲线与实验数据相符合,曲线表明装粉高度增加时,粉末和模具加热温度应当降低,对于某些装粉高度温压失去有效性。 相似文献
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利用粉末冶金技术制备纯铁软磁材料,在不同温度和压力下将不同粒径铁粉压制成生坯,并在保护气氛下进行烧结。结果表明:不同粒径铁粉混合有助于压坯密度的增加,适宜的压制温度可以有效地促进粉末流动,避免大尺寸孔洞的形成,优化组织。140℃、800 MPa温压条件下雾化铁粉压坯密度最高可达7.35 g·cm-3。对比常温压制,温压压坯烧结后孔洞分布均匀。烧结体密度随温度的升高而上升,雾化铁粉压坯在1250℃烧结后密度最高可达7.47 g·cm-3。在一定范围内,软磁材料磁性能与密度成正比,混粉压制试样的密度接近理论值,但在混合铁粉中,较细的铁粉夹杂于粗粉中,阻碍磁畴壁移动,造成饱和磁化强度(Ms)偏小、矫顽力(Hc)偏大的现象,Ms为205.51 emu·g-1,Hc为7.9780 Oe。 相似文献
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A. K. Radchenko 《Powder Metallurgy and Metal Ceramics》2004,43(11-12):552-563
Mechanisms of strength for green compacts made from powders of iron, nickel and its alloys, copper, tin, and zinc are analyzed. The strength of green compacts prepared from metal powders of medium fineness with a relative bulk density (RBD) from 0.119 to 0.568 by two-way compaction in rigid dies with homologous temperatures from 0.15 to 0.59 (pressure from 200 to 800 MPa, powder deformation rate 10?2–10?3 m/sec) is studied. Compact strength is determined by diametric compression of cylindrical compacts. The dependence of strength on compact porosity is studied by the Bal’shin equation. The possibility is demonstrated of using this relationship in order to describe hot compaction and formally describe cold compaction of powders with RBD up to 0.40. The effect of homologous temperature and powder RBD on compact strength is determined. The homologous temperature for transition from warm to hot compaction and the effect of compact density (degree of deformation) on this temperature is studied. It is shown that linear approximation is possible for the dependence of compact strength on powder RBD according to the equation σ f.c = 87–217?RBD. 相似文献