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。     

‘Double strength for green parts’ claim ushers in new Hoeganaes technology…

Hoeganaes Corporation has introduced a high green strength powder that it says gives up to twice the green strength for conventionally produced ferrous metal powder parts. The aim of ANCORMIX HGS is to produce metal powder premix materials that help prevent crack formation during part ejection, and other problems associated with green parts without warm compaction or high compression techniques.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

Making better PM products

A two-day seminar dealing with machinability of PM parts is to be held in Dearborn, Michigan, in early December. The meeting at the Hyatt Regency on December 3-4 is designed to provide delegates with in-depth knowledge and understanding of both the fundamental and practical aspects of machinability in PM parts. Among the topics to be covered are improving operations to make higher quality parts, reducing costs, increasing productivity and greater profits.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

温压压制压力强化因子及压制曲线的唯象分析

介绍了一种使用钢铁粉末室温压制回归方程来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。     

Bearing Materials by Powder Metallurgy

Abstract

The dependence of green strength on green density and on compacting pressure was investigated for the bidirectional die pressed and isostatically pressed Cu powder compacts. The breaking strength of the pressed Cu compact was found to increase with green density and also with compacting pressure. The green strength seemed to be directly proportional to the contact area between powder particles. A theoretical equation for the relationship between green density and contact area was derived from a geometrical consideration, and agreed well with experimental findings. PM/0272     

Study of warm compaction of Alumix 123 L

Abstract

Although powder metallurgy (PM) material is dominated by ferrous alloys, there is a growing interest in Al PM. The usage of Al PM in automotive applications depends on the development of higher density and improved dynamic properties. Several approaches have been proposed to increase density of sintered parts. Warm compaction process of Al powder was used to achieve high density. In this study the authors focused on the effect of warm compaction on Alumix 123 L (ECKA Granules) powder blend. It has been found that warm compaction at 110°C led to a reduction in the ejection force by 27·9%, increased green density to 94% of theoretical density and increased sintered strength to 315 MPa as compared to those pressed at room temperature.     

Stainless winners

According to American Metal Market, Ford is set to use a record number of PM stainless steel parts in new premium midsize saloons and sport wagons.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

用先进的温模压制工艺生产高密度汽车零件

高密度压制工艺(温模压制)扩大了粉末冶金零件的应用范围。鉴于一次压制/一次烧结(1P/1S)所达到的密度已超过了7.3 g/cm~3,这种成本可行的零件生产方法,往往是最新高密度汽车零件应用采用的方法。达到较高零件密度的关键的第一步是改进润滑剂与预混合工艺,以将润滑剂的含量减小到预混合粉重量的0.25%。本文详述了新润滑剂系统,能够使润滑剂含量减低到预混合粉重量的0.25%,并使生坯密度高达7.5 g/cm~3左右。除了生坯密度高外,生坯强度也达到了30 MPa左右;并能将压制与生坯零件后续处理时开裂的可能性减小到最小程度。虽然还不能用于所有类型的零件,但在Cloyes Gear已证明,这种新的粉末预混合粉,对于生产汽车的气门机构零件是成功的。将详述开发工作的情况和得到的生产体验,并讨论其优点与局限性。     

Numerical simulation of metal powder die compaction with special consideration of cracking

Abstract

Powder die compaction is modelled using the finite element method and a phenomenological material model. The Drucker–Prager cap model is modified with the goal to describe the formation of cracks during powder transfer, compaction, unloading, and ejection of the parts from the die. This is achieved by considering the cohesive strength and the cohesion slope, which characterise the current strength of the powder compact in the Drucker–Prager model, as state dependent variables. Evolution equations are formulated for these variables, so that the strength increases by densification and decreases by forced shear deformation. Some of the parameters appearing in the evolution equations are determined from measured green strength values. An iron based powder (Distaloy AE) is used for the experiments. Examples are shown to demonstrate that the density distribution can be calculated accurately as compared with an experiment, that cracking can be modelled at least qualitatively correctly, and that the compaction of complex 3D parts can be simulated.     

HVC punches PM to new mass production limits

High-velocity compaction enables the production of large, high-density PM parts weighing more than 10 pounds. Three researchers from Swedish powder producer Höganäs AB say that metal powder is compacted in less than 20 milliseconds by high-energy impact, and can be further compacted by additional multiple impacts with intervals as short as 300 milliseconds. They say this is a mass-production method that can expand the use of PM beyond its current limitations…     

Characterisation of machinability of sintered steels during drilling operations

Abstract

This study deals with the quantitative evaluation of the machinability of sintered steels during drilling operations. A characterisation technique using scanning electron microscopy and image analysis was developed to characterise quantitatively the amount of flank wear on drillbits. It was shown experimentally, using a drilling test bench, that the evolution of flank wear was proportional to the rate of variation of the thrust force as measured during drilling. Thus, the results show that the slope of the linear region measured on the curve of the thrust force v. the amount of material removed is a more accurate criterion to characterise the machinability of PM products than the average thrust force, which is often suggested in the literature.

Furthermore, the effect of the technique used to add MnS to PM powders was investigated. Quantitative characterisation of machinability during drilling operations showed that parts made with steel powders of the type FC–0208 + 0·5 wt-%MnS machine better when the manganese sulphide particles are pre-alloyed rather than admixed. Finally, machinability of parts made with two sinter hardening powders was characterised including a pre-alloyed MnS powder. The results showed that the ‘drillability’ of this type of part is improved when they are in the presintered state rather than when they are in the green state, i.e. unsintered. Moreover, parts made with the sinter hardening powder pre-alloyed with manganese sulphide particles (MnS) showed superior machinability characteristics.     

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.     

Fe-1.0Cu-2.0Ni-0.55Mo扩散型合金钢粉的研制

本文针对莱粉公司生产的Fe-1.0Cu-2.0Ni-0.55Mo扩散型合金钢粉的生产工艺、粉末性能及其烧结件性能进行了研究。结果表明,采用本工艺生产的扩散型合金钢粉基本保持了基体粉末压缩性高、流动性好的特点,可获得高的压坯密度和烧结体密度;合金粉末损失少且分布均匀,制件尺寸精度高、机械性能稳定;扩散合金化效果好,制件具有较高的硬度和抗拉强度。同时,该生产工艺减少了合金粉末(细粉)的损失和飞扬,生产环境得以很大改善。     

开发高性能水雾化钢铁粉末的新思路

高性能水雾化钢铁粉末是指其不仅具有高纯度、高压缩性,而且能达到较高的压坯强度,其工艺性能应介于高压缩性的雾化粉和高成形性的还原(海绵)粉之间,在不改变V型喷嘴水雾化基本工艺的前提下,将雾化水压提高以获得数量多的极细颗粒(-325目)和通过适当升高精还原温度以增加不规则形状及中等粒度范围(-80+200目)的粉末数量,从而保证粉末可获得高的压坯强度,鉴于国外钢铁粉末的标准中已采用压坯强度或转鼓试验磨损值作为考核粉末成形性的指标,作者建议我国在修订钢铁粉末标准时增加压坯强度的测试项目。     

New year, new thinking and new presses

As the year turns, so do the options open to manufacturers. That's true in powder metallurgy just as in any other industry. For although stamping out green parts may seem to be the run-of-the-mill first stage to PM production, a US press maker has combined new thinking with new technology to get profitable results that should set the small world of press builders talking…     

Design competition opens

The Metal Powder Industries Federation (MPIF) has opened the 2004 International PM Design Competition. Entries must be received by 27 February. The competition recognises outstanding achievements in the commercial production of PM components.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

用温压制造汽车变速器输出轴毂

汽车中应用的铁基粉末冶金零件在不断增加,这主要是由于密度的增高和动态性能的改进。粉末冶金零件的新应用还必须通过不断采用新工艺的最终形成形能力及减少制造工序,降低生产成本。用于制造某些新零件的生产工艺,还必须能生产出几何形状复杂的薄壁零件。采用温压工艺(ANCORDENSETM),用一次压制可达到较高密度水平。这种工艺还能增高生坯强度与减小脱模力。汽车变速器输出轴毂在20世纪90年代以前,是用二次压制/二次烧结工艺大量生产的一个重要粉末冶金零件。1995年前后,用温压工艺进行了制造这种零件的试验,并和用二次压制/二次烧结工艺生产的零件进行了对比。     

The history of Distaloy

Abstract

The low alloy steel powder Distaloy, is today widely used in applications demanding high strength and wear resistance. Its basic properties and composition were designed half a century ago in the USA. The advantage lay in the fact that it was a partial prealloy, i.e. the alloying elements – copper, nickel and molybdenum – were bonded in particulate form to the basic iron particles, thus avoiding impairment of the compressibility. By balancing the contents of nickel and copper it was possible to minimize dimensional change on sintering. Bonding the alloy particles to the iron particles minimised segregation and also contributed to dimensional stability. Carbon was added conventionally as fine graphite. However, the new powder, marketed as Ancoloy, did not take off in North America, due to the lack of suitable applications, the cost of the alloying elements and – above all – the poor compressibility and high oxygen content of the iron powder then available. The high, variable oxygen content made it impossible to control the carbon content with the precision necessary to achieve the desired strength and hardness.

In the 1960s, demand for high strength precision parts emerged in the European car industry, initially at Citroen, which pioneered increased use of PM parts in European cars. The component was (and still is) the synchronising hub used in manual transmissions. Höganäs had in the mid-1960s developed a sponge iron powder with much higher compressibility, and this was taken as a raw material for an improved grade, later to be called Distaloy SA. This new powder had improved compressibility and very low oxygen and carbon contents, which made it possible to make the high strength precision parts that the car industry required. Distaloy was immediately accepted and used, first in the French car industry, then elsewhere in Europe and subsequently also in Japan. Some years later, when high compressibility atomised powder became available, the same basic technique was applied to these, to produce the Distaloy A grades, which now are most popular. Höganäs continues to improve and refine the production techniques and to come up with compositions for new applications.

The properties and the metallurgy of Distaloy-based materials have been thoroughly studied by metallurgists at Höganäs and at PM laboratories throughout the world, and new results are still being reported with respect to both applications and fundamental properties. A parameter of great relevance is of course the cost of raw materials and much effort is going into finding more cost effective ways of achieving the desired results.     

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%。