EBS蜡静电荷电和模壁润滑特性研究

采用粉末冶金静电模壁润滑和冷压／温压技术，通过对316L不锈钢粉进行压制和烧结，从而研究出压制过程中润滑剂EBS蜡粉的静电和润滑特性。结果表明：经较长（L）的输粉软管摩擦后，EBS蜡粉表现出较好的荷电性和低压吸附能力；在温压中（110℃）EBS蜡粉比室温下表现出更好的润滑性；高密度生坯中EBS蜡粉作为内润滑剂少量存在对烧结样品的密度和形状并没有出现负面的影响。     

润滑剂对Fe基粉末冶金材料温压工艺的影响

通过扫描电子显微镜观察和性能测试研究了硬脂酸锌、乙烯基双硬脂酰胺(ethylene bis stearamide,EBS)、复合润滑剂以及压制温度对Fe基粉末冶金材料温压工艺的影响规律。结果表明:当润滑剂加入量(质量分数)超过0.4%后,Fe基粉末的流动性和松装密度均随润滑剂加入量的增加而降低,其中加入单一EBS润滑剂的影响更大。添加润滑剂后增加了Fe基粉末冶金生坯的致密度,其中添加硬脂酸锌和复合润滑剂的Fe基粉末冶金生坯断口颗粒间结合更为紧密。润滑剂对提高Fe基粉末冶金试样生坯密度、烧结密度及抗弯强度的作用顺序为复合润滑剂硬脂酸锌EBS,Fe基粉末冶金材料的密度和力学性能均随温压温度的升高而增加。在最佳润滑剂加入量0.4%时,120℃温压Fe基粉末冶金试样密度比室温压制Fe基粉末冶金试样的密度提高了0.14~0.21 g/cm~3,硬度和抗弯强度提高了40%~65%。     

316L不锈钢粉末温压与模壁润滑的高密度成形

通常在室温下，用内润滑厅式难以将316L不锈钢粉末压制成高密度生坯。本工作研究了316L不锈钢粉末的温压、模壁润滑和同时使用温压与模壁润滑的压制过程。研究发现：（1）模壁润滑和温压的同时使用可大幅度提高316L粉末的模压生坯密度。（2）复合润滑剂比单质EBS蜡更适用于有模壁润滑的温压过程，在工业常用的压制压力下，粒度〈74μm的316L粉末的生坯密度超过7．4g／cm^3。（3）316L粉末的高密度成形使得粉末颗粒强烈塑性变形，出现了晶粒内的亚晶结构。（4）同时使用模壁润滑和温压得到的高密度生坯在烧结过程不会发生体积膨胀，烧结密度超过7．56g／cm^3。     

模壁润滑剂对氢化钛粉末冷压成型的影响

以海绵钛通过氢化脱氢法(HDH)制取的氢化钛TiH2粉体为原料,分别选择硬脂酸锌(ZnSt)、硬脂酸(SA)和聚乙二醇(PEG-6000)作为模壁润滑剂进行冷压成形,并真空烧结得到最终制件。对比不同模壁润滑剂对生坯和烧结件的性能及质量的影响,研究分析对钛及钛合金粉末冶金冷压成型最适宜的模壁润滑剂。研究结果表明,模壁润滑剂的使用不仅能提高生坯的密度和强度,还能有效改善掉边和裂纹现象,延长模具寿命。同时,模壁润滑剂还有一定的提高烧结密度的能力,并有利于孔洞的减少和优化,对制件的增氧影响也较为有限。这些实验结果说明模壁润滑剂是适合钛及钛合金粉末冶金的。而相比于其他两种模壁润滑剂,硬脂酸无论是在成形生坯件还是烧结件上都具有明显的优势,是较为适宜的钛及钛合金粉末冶金成型的模壁润滑剂选择之一。     

利用高生坯强度润滑剂开发无线通讯装置用PM软磁零件

软磁烧结铁框是无线通讯装置中的一个重要零件，用其来防止电子元件间的电磁干扰和对人有害的电磁辐射。铁框结构复杂且轻巧，依据电子电路的具体设计，壁厚可薄至0.8mm。传统的金属冲压成形因零件挠曲而不能满足尺寸公差与平直度的要求。用粉末冶金工艺制造铁框面临的难题是因壁薄，截面处易碎而使生坯难以搬运。用常规的硬脂酸锌或EBS蜡之类润滑剂混粉，生坯的废品率高达50％。因此，采取了用新近开发的高生坯强度润滑剂，制造烧结铁框的方法。为使开发的烧结铁框能达到磁性要求，选用了添加0.45%磷的高纯铁粉ATOMET 1001HP。采用冷压、温压及在压制后进行和不进行固化的不同工艺，测试了几种高生坯强度润滑剂纱列，从中选出了一种使压坯强度满足粉末冶金铁框压坯搬运要求的润滑剂系列，从而大大降低了生产成本。     

模具润滑技术的定量评价和新润滑剂开发

为了使粉末冶金零件达到高密度,近年来采用了几种新技术,诸如温压、表面致密化、高速压制等。模壁润滑是这些技术中之一种。可是,很少研究模壁润滑的定量分析,也没有适合模壁润滑的润滑剂。作者们通过比较摩擦式(TRIBO)与电晕火花式研究了模壁润滑技术,还研究了几种润滑剂的电位值。通过这些研究,合成了一种模壁润滑用的新润滑剂。     

专利信息

一种不锈钢粉末热压成形方法本发明提供了一种316 L不锈钢粉末热压成形方法,先对316 L不锈钢压制粉末与模具进行加热,并用热电偶分别控制316 L不锈钢压制粉末与模具的温度,316 L不锈钢压制粉末加热温度控制在100~140℃,模具加热温度控制在100~160℃;使用静电模壁润滑装置对模具内壁喷涂复合润滑粉,使用的复合润滑粉组成为:25%~75%EBS蜡+25%~75%石墨或25%~75%W-special蜡+25%~75%石墨,模具引导线接地,复合润滑粉喷涂完毕后,把加热后的316 L不锈钢压制粉末倒入模具的模腔中进行压制成形。其优点在于:能获得较高密度生坯,达到较好的尺寸精…     

专利信息

粉末冶金用铁基混合粉　提供一种由用粘合剂将合金用粉末等粘着在表面上的铁基粉末,还有游离润滑剂构成的铁基混合粉,由于铁基粉由6 0 % -90 % (质量分数)的雾化铁粉与4 0 % - 10 % (质量分数)的还原铁粉的混合铁粉构成,因此为填充性、压缩性优良,且防止偏析的粉末冶金用铁基混合粉。粘合剂为选自硬脂酸、油酸酰胺、硬脂酸酰胺、硬脂酸酰胺与乙撑双硬脂酸酰胺的熔融混合物和乙撑双硬脂酸酰胺中的1种或2种以上,或为由选自油酸、锭子油、透平油中的1种或2种以上与硬脂酸锌构成的粘合剂是理想的。另外,游离润滑剂使用选自热可塑性树脂粉、硬脂…     

外润滑代替内润滑

在粉末压制过程中,为减少摩擦,需加润滑剂。通常的作法是,在粉末中混入润滑剂。但是这样做,一方面降低了密度,另外还有污染环境等问题。有些润滑剂在烧结中不易除去,引起部件起皮,有些则沉积于炉壁上,降低炉子寿命。模壁外润滑可减少这些问题,但难于将润滑剂有效地保持在模壁上。美国锌公司经过多     

几种润滑剂对温压工艺的影响

温压工艺的技术关键之一是润滑剂 ,其主要作用是减小压制过程中粉末颗粒与模壁之间及粉末颗粒之间的摩擦 ,增大有效压力 ,从而使压坯密度相对于传统压制工艺明显提高。不同润滑剂的润滑效果不同 ,最佳压制温度也有差异。本文选用 3种不同的润滑剂 ,在不同温度、压力条件下采用温压技术制备铁基粉末冶金材料 ,研究了压坯密度的变化规律和它的力学性能 ,探讨了润滑剂对温压工艺的影响     

Influence of Lubricants on Dimensional Changes and Mechanical Properties of Sintered Ferrous Compacts

Abstract

The influence of admixed zinc stéarate on the shrinkage of uniaxially pressed iron powder compacts has been studied. For pressing conditions which caused inhibition of compaction the removal of the stéarate during sintering produced an increase in shrinkage parallel to the pressing axis and in direct proportion to lubricant content. Additions of stearic acid (varying particle size), zinc stearate, lithium stearate, stearamide, and Cosmic 64 wax were used to investigate the influence of lubricant on mechanical properties of green and sintered iron powder compacts. Green strength was reduced relative to unlubricated material only by lubricants whose physical and chemical properties enabled them to produce and maintain extensive interparticle films during pressing. Vapour from the rapid initial decomposition of lubricants which reduced green strength could have a deleterious physical influence on the tensile strength of dewaxed or sintered Fe compacts. Decomposing lubricants also produced undesirable chemical effects. These arose from reactions between lubricant decomposition products and the matrix or by these products interfering with reactions between matrix and sintering atmosphere.     

Pressing behavior of atomized iron powders

Conclusions The optimum zinc stearate content, ensuring the greatest compressibility of a powder at a given pressing pressure, is determined mainly by the volume of interparticle pores. The higher the density of a compact and the smaller the size of its pores, the smaller is the amount of zinc stearate it can hold. The weakening action of zinc stearate, which manifests itself in stress relief at interparticle contacts during pressing, substantially increases the density of compacts and at the same time decreases their strength. This phenomenon is particularly pronounced with compacts from powders of poor compactibility. After pressing at any given pressure, the strength of a compact with zinc stearate will be higher than that of a compact without a lubricant when the decrease of the contact surface brought about by the elastic aftereffect in the stearate is counterbalanced by the increase of this surface resulting from better compressibility of the powder. The addition of an optimum amount of zinc stearate to an iron powder is always more effective than lubrication of the die walls. A new mechanism of densification of iron powder with zinc stearate is proposed, in which the key factor is an intensification of stress relief at interparticle contacts by the solid lubricant.Translated from Poroshkovaya Metallurgiya, No. 5(221), pp. 16–22, May, 1981.     

IMPORTANCE OF STEARATES IN THE FABRICATION OF UO2 AND (U,Pu)O2 PELLETS

Abstract

Eighteen qualities of metallic soaps have been studied, either as lubricants or as additives for the fabrication of UO₂ and (U,Pu)O₂ pellets. Compounds of the same family, such as zinc stearates, differ in their effectiveness as lubricants. This property is strongly dependent on the particle size of the powder and its purity. The behaviour of the dry lubricants when used as admixtures in UO₂ and also when employed for the direct lubrication of the pelletizing tools is discussed.

The efficiency of metallic soaps as additives to lower the density of the sintered pellets is related to the nature of the metallic ion. Thus, zinc stearate has little influence on the fired density of UO₂, whereas barium stearate and other barium compounds are very effective. Barium inhibits sintering, but zinc, which is eliminated at low temperature, does not diminish the sinterability of the oxide powders. In the latter case, the decrease in density is caused by thermal decomposition of the organic molecule.     

润滑剂对温压FeSiAl磁粉芯性能的影响

采用温压成形工艺将水雾化Fe Si Al粉末制备成磁粉芯;用X射线衍射对原始粉末和经过绝缘包覆及热处理的粉末进行物相分析;采用软磁交流测试仪测量磁粉芯的磁损耗;利用精密磁性元件分析仪测量样品的磁导率。混合不同质量分数的硬脂酸锌和聚乙二醇(PEG)作为温压润滑剂,并研究其对Fe Si Al磁粉芯性能的影响。结果表明,1 100 MPa/100℃的温压成形条件下,当硬脂酸锌和PEG质量比为2:3,添加温压润滑剂的质量分数为1.3%时,磁粉芯生坯密度达到最大值5.75 g/cm3,热处理后为5.74 g/cm3。660℃×1 h热处理后,100 k Hz下,相应的有效磁导率?e达到137.9;350 k Hz/50 m T下磁损耗Ps为81.78 W/kg。     

Certain features of warm isothermal compression of iron powder

Processes of warm compression of mixtures of iron powder with organic binder (animal fat, zinc stearate) are investigated. Comparative experiments on the compressibility of SC-100.26 and PZhRV-200.28 iron with different binders are conducted. An increment in the density in warm compression of iron powder is achieved only where the iron powder is of high ductility, high purity, and the lubricants present in the mixture are of sufficient viscosity at the temperature and pressure of warm compression.     

New technological approach to fabrication of high density PM parts by cold pressing sintering

Abstract

A new technological approach to the fabrication of high density powder metallurgy (PM) parts via single pressing sintering, allowing cold compaction to be performed without admixed lubricants, has been studied. The influence of in pore gas on the compacts' green density and their sintered properties were evaluated. A mathematical expression relating in pore gas pressure in the compacts to the green density was developed. The expression showed that in order to reduce the negative influence of gases trapped in the pores it is necessary to ensure effective air drainage from the compaction zone. In order to ensure sufficient air evacuation during cold compaction, a new design of porous die was developed. The behaviour of powder mixes with different lubricants during cold compaction in porous die was investigated. All the test conditions were evaluated in terms of green and sintered properties, including the ejection force, green and sintered densities, tensile strength and surface hardness. In the context of the experimental work, compaction in porous die promoted the improved combination of green and sintered properties compared with compaction in conventional dies.     

LUBRICATION EFFECTS IN THE COMPACTION OF SPONGE-IRON POWDER AT LOW AND HIGH SPEEDS

Abstract

The effects of the amount and method of lubrication have been investigated when compacting Höganäs sponge-iron powder, NC100-24, at both low and high speeds. Pressing characteristics, ejection loads, and the final properties of the sintered compacts were markedly affected by both the amount and the method of lubrication. From the results obtained, an optimum amount of admixed zinc stearate is recommended for both low and high-speed conditions.