… as QMP offers new high-strength grades

Canadian-based QMP Metal Powders will be promoting a high-strength diffusion-bonded molybdenum steel powder at PM2003 in Valencia later this month. ATOMET DB49 is a newly developed grade that allows the manufacture of PM parts with a tensile strength of more than 850MPa using normal sintering conditions in belt furnaces equipped with a rapid cooling zone. The company will also be exhibiting their own polymeric HGS lubricating system that, they say, “drastically enhances the strength of green parts to the point where they can withstand the stresses applied by cutting tools during machining. QMP will also be showing off a new sponge-type iron powder, ATOMET 24, for high green strength applications that can be used to facilitate the production of more complex parts.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

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。     

SMC Quality rating

SMC Powder Metallurgy of Galeton, Pennsylvania, has passed the tough qualification tests to win accreditation to ISO/TS16949, a quality management system that satisfies the international auto business. Peter Lake, President of the SRI Quality System Register, said: ”SMC has demonstrated effective implementation of a quality management system that satisfies the tough new auto standard for the manufacture of powder metal gears, sprockets, bearings and structural parts.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

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。     

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。     

金属粉末电磁压制基本机理及致密工艺

成型是粉末冶金工艺中比较重要的一环．文章分析了金属粉末电磁压制的基本机理和压制工艺参数对粉末压坯密度的影响，并对粉末压制致密工艺给出了理论参考．     

基于内聚力模型的金属粉末压坯拉伸裂纹扩展模拟

压坯裂纹损伤预测分析对于生产高质量粉末冶金零件具有重要的指导作用。本文将修正的Drucker–Prager Cap模型与内聚力损伤模型相结合,并利用Python语言在损伤断裂区域内批量插入内聚力单元,模拟金属粉末压坯在外载荷作用下裂纹扩展过程。同时,采用不同类型的内聚力模型对巴西圆盘实验过程进行模拟,通过实验验证对比分析可知,采用指数内聚力模型模拟压坯拉伸裂纹扩展的结果与实验结果更为吻合,并且与实验后期压坯边缘出现剪切带的现象也较为一致。     

温压工艺的研究进展

温压工艺在制造低成本、高密度、高强度、高精度异形复杂的粉末冶金零件方面具有巨大的优势。因而，详细介绍了该工艺所具有的诸如压坯密度大、强度高，烧结密度高、密度分布均匀，脱模压力低，制造成本低等技术与经济特点；分析了其关键技术，如温压用粉末制备、新型润滑剂和温压系统；总结了其致密化机理，即颗粒重排和塑性变形，并概括了其应用状况。最后指出发展我国温压工艺的意义。     

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.     

环形薄壁类粉末冶金零件压坯残余应力分析

针对环形薄壁类粉末冶金零件压坯的残余应力进行分析,采用修正的Drucker-Prager Cap弹塑性本构模型对金属粉末压坯压制、卸载和脱模过程进行数值模拟,同时考虑不同零件压坯几何参数(高径比和厚径比)以及压制工艺条件(摩擦条件和脱模角度)对压坯内残余应力的影响.研究结果表明,压坯脱模后的残余应力分布规律是压坯侧表面出现明显的压应力层,内部为拉应力区域,且越靠近压坯中心值越小.随着高径比和厚径比的增加,其残余应力逐渐减小;随着摩擦系数的增加,压坯表面的轴向残余压应力不断增大且压坯内部的拉应力也不断加大;适当增加脱模角度有利于压坯内应力释放而减小残余应力.通过正交模拟试验及方差分析可知,厚径比和脱模角度对金属粉末成形脱模后压坯残余应力影响更为显著.     

Selective Laser Melting of Maraging Steels Using Recycled Powders: A Comprehensive Microstructural and Mechanical Investigation

Selective laser melting (SLM) is an additive manufacturing (AM) technique designed to use a high energy density laser to fuse metallic powders for producing three-dimensional parts. So far, most studies of SLM have been focused on using virgin metal powders. There are few comprehensive studies on the microstructure and mechanical properties of SLM-produced parts using recycled powders, especially for maraging steels. In this study, we employ recycled steel powder (reused after 113 building cycles) in the SLM process to print multiple shaped components and systematically characterize the microstructure and mechanical properties (indentation, tensile, and Charpy testing). Our results show that maraging steel produced with recycled powder exhibit the nearly identical microstructure and mechanical properties (940 MPa yield strength, 1127 MPa ultimate tensile strength, 11 pct elongation, and 47.5 J room temperature impact fracture energy) to those produced using virgin powders. This study provides a useful generic guide towards using recycled metal powders in the SLM processing, promoting an economic solution to industrial productions.

     

金属粉末凝胶注模成形技术的研究现状及应用前景

凝胶注模成形是一种适用于复杂形状、大尺寸部件的近净尺寸成形技术,因其设备简单、成形坯体密度均匀、强度高、不需专门的脱脂工序等突出优点而受到广泛关注。目前国内对该技术的研究多集中在精密陶瓷部件的近净成形上。本文简要介绍了国外金属粉末凝胶注模成形技术的研究现状及本文作者将该技术应用于成形复杂形状铁基粉末冶金零件上的研究进展,并对金属粉末凝胶注模成形技术的主要技术难点、对策以及广阔的应用前景进行了分析与展望。     

Lovejoy invests against economic trends to offer greater accuracy and green density

An Illinois powder metal manufacturer has installed a new manufacturing system it claims to be a ”world-beater” — and set up a new division to take advantage of its capabilities.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

‘More power’ call sparks soft compact research

The 42-volt electrical system is to be introduced in automobiles to provide the extra power needed for various electromagnetic devices. This offers an opportunity for insulated iron powder to replace lamination steel in a variety of motors. Brushless motor design can probably benefit most from insulated iron powder compacts because of the design simplicity of powder metal parts and three-dimensional flux capability that is most beneficial in rotating devices says Sim Narasimhan…     

含水量和粘结剂含量对硬质合金粉末压坯强度的影响

将硬质合金粉末和聚乙烯醇(PVA)水溶液按一定比例混合、球磨,经喷雾造粒后进行压制成型,研究了含水量和粘结剂含量对粉料特性和压坯强度的影响.研究结果表明:随着含水量的增加,粉料松装密度减小,流动性变差,压坯强度增加.水含量控制在0.06 wt%～0.14 wt%较为适宜,此时的粉料适合自动压制成型,压坯强度较高;当粘结剂含量从1.0 wt%增加到2.0 wt%时,压坯强度从0.76 MPa增加到1.93 MPa,当加入的PVA含量从2.0wt%增加到2.4 wt%时,压坯强度有减小的趋势.在保证坯体强度的前提下,合适的粘结剂含量为1.6 wt%～2.2 wt%.     

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.     

Mechanical properties of green compacts. II. Effect of powder relative bulk density on the strength of compacts with different forming temperature conditions

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.     

Influence of injection moulding and sintering parameters on properties of 316L MIM compact

Abstract

This study elucidates the effects of key injection moulding and sintering factors on the dimensions and mechanical properties of 316L stainless steel metal injection moulded compact. Sintered parts of optimal quality can be produced by properly setting the process parameters. Taguchi method and principal component analysis are performed initially to elucidate and optimise the key control factors that affect the qualities of metal injection moulded compact. Next, a feasible process window is tested by observing the powder and binder distribution of green parts, for various control factors of injection moulding. Experimental findings show that, first, a proper injection speed facilitates mould filling during injection moulding and so improving the quality of sintered parts; second, temperature critically determines the rate of dimensional shrinkage, density and hardness of sintered parts; Third, optimal parameters setting can efficiently improve the quality of 316L metal injection moulded compact.     

THE EFFECT OF INTERPARTICLE CONTACT AREA ON THE STRENGTH OF COLD-PRESSED ALUMINIUM POWDER COMPACTS

Abstract

Measurements of the tensile strength of spherical cold-pressed aluminium powder, pressed to various densities up to the theoretical maximum, have shown that compaction is a two-stage process. At some high, intermediate pressure, interparticle sliding occurs in a way that does not itself increase densification but makes it easier for further deformation to occur. It is likely that the pressure at which this sliding takes place is dependent on the work-hardening rate of the powder as well as the powder size and morphology. In any case, it is shown to be important to the densification and strength reached by the compact.

It is concluded that the strength of a green compact is dependent upon the interparticle metallic contacts made during compaction. However,the green strength is well below that of wrought aluminium, probably due to the presence of broken-up oxides,which act as stress-concentrators at the interparticle boundaries.     

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.