可得到高使用性能的一次压制/一次烧结生产工艺

高密度粉末冶金零件(PM)意味着力学性能增高与零件的使用性能改进.虽然,高密度零件生产工艺不是新工艺(熔渗铜与二次压制/二次烧结工艺都已应用了许多年),但是最近10多年的发展,使着用一次压制/一次烧结工艺已可得到较高的密度.这些先进的生产工艺叫做温压,其是一种利用有专利权的润滑剂与温模或温热粉末相结合的压制工艺.其在得到高密度烧结件的同时,仍然可保持粉末冶金固有的优势.可得到高密度的其它粉末冶金工艺还有模壁润滑与选择性表面致密化.对于每一种方法都进行了述评,并附带用资料证明了材料的性能与使用性能.     

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。     

粉末冶金温压工艺在扬州保来得投入生产

扬州保来得工业有限公司在消化吸收国际粉末冶金最新温压技术成果的基础上 ,用温压工艺制造高密度粉末冶金冲击齿轮已批量投入生产。粉末冶金温压工艺是 90年代工业先进国家普遍重视的一项新技术 ,它是将预混合粉末和模具同时加热到一定温度进行压制 ,然后常规烧结。这一工艺不仅大大提高了铁基零件一次压制———烧结的密度 ,而且该工艺的压制压力和脱模力均较传统方法低 ,从而提高了模具寿命 ,降低了成本。特别对复杂形状、高密度、高强度零件的开发具有巨大的生命力和潜力。扬州保来得公司用粉末冶金温压工艺生产的冲击棘轮主要应用在冲…     

关于用不同工艺制作的高密度铁基粉末冶金材料性能的研究

可能有几种方法可使铁基粉末冶金零件达到较高密度。二次压制/二次烧结可使密度大于7.3g/cm3,但受到成本与几何形状条件的限制。对一种新方法进行了评价,用这种方法可一次压制得到高使用性能材料,并将其和其他生产工艺进行了比较。比较是利用Ancorsteel 85HP与Distaloy 4800A基本材料进行的。对各种生坯与烧结件性能进行了评价,其中包括:生坯强度,横向断裂强度,拉伸性能及冲击值。数据清楚地证明,拥有专利的[1]ANCORDENSETM工艺(温压)提供的使用性能可与二次压制/二次烧结制作的相比拟。用一次压制达到了生坯密度值的无孔隙密度极限的98.5%。     

高密度粉末冶金螺旋齿轮

汽车行业已证实,粉末冶金是生产高强度齿轮的一种技术。粉末生产、压制及烧结的进展和二次压制相结合,可以使正齿轮零件密度达到7.5g/cm3。然而,由于螺旋齿轮的几何形状不适用于DP/DS工艺,所以螺旋齿轮很难达到相同的密度。本文主要讲述能够生产芯部密度接近7.4g/cm3的一次压制与一次烧结螺旋齿轮的制造工艺。讲述了试验过程,制造烧结零件的密度及零件间的变动性。为了进一步改进这些螺旋齿轮的使用性能与几何形状,接着用辗压将之进行了表面致密化。将说明表面的密度与齿轮品质的改进。     

粉末冶金零件需要的高性能润滑剂

目前粉末冶金零件产业要解决的主要问题是:在合理降低成本的情况下生产高密度零件。生产高密度零件的工艺方法有很多种,其中包括零件的成形工艺和烧结技术。特别是,像温压与模壁润滑之类的一次压制工艺。这种工艺依据粉末的组成,生坯密度可达到的范围为7.2~7.5 g·cm-3。尽管如此,和传统压制工艺相比,这些压制工艺一般都需要严密控制,费用也相对较高,还有可能减小生产率。为了能让冷压制或控制温度的阴模压制达到较高的生坯密度,最近开发了一些新的高性能润滑剂。本文介绍了这些新开发的高性能润滑剂在试验室与大量生产中得出的生坯与烧结件特性。特别对这些新润滑剂和其他常规润滑剂的压制与脱出特性进行了对比。     

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。     

金属粉末温压工艺的研究现状和进展

温压工艺是对传统的一次压制／ 烧结工艺的改进，即将预合金粉末在一定温度下压制，然后常规烧结，以获得较高的产品密度。其关键技术，一是预混合粉末的制备，二是温压系统的设计。温压工艺生产的零件，主要用于制备高磁性材料、高密度复杂形状的零件，特别是在高强度汽车零件制造方面，具有更强的生命力。粉末冶金温压工艺的开发和应用，填补了传统的一次压制和复压之间的空白，在技术上和经济上为扩大粉末冶金的应用提供了可能性。     

高密度零件用润滑剂的使用性能

随着粉末冶金零件应用领域的不断扩大,对高密度零件的需求量逐步增多,这些零件都需要较先进的混合粉与高使用性能的润滑剂。润滑剂的含量必须尽量低,以使零件达到较高的密度。所以,高密度零件用润滑剂必须在比传统润滑剂的浓度低得多的条件下,能提供和传统润滑剂同样的润滑性能。本文介绍了为使铁基粉末冶金零件的密度达到7.30 g/cm3以上,专门设计的新润滑剂的压制与脱出性能。在实际生产条件下,对这些润滑剂进行了系统评定,讨论了用这些润滑剂制备的混合粉的物理与烧结性能。最后,将试验结果和粉末冶金产业中一般使用的润滑剂进行了比较。     

用于汽车自动变速器的温压涡轮毂

温压是一种可将增高密度与选择高使用性能材料相结合的技术。增高密度有助于提高零件的力学性能,以及整体使用性能。将密度增高与高使用性能相结合,可使制造的零件的使用性能超过相应的铸锻材料产品,同时可制成具有最终形的零件,从而显著减低生产成本。因此,自动变速器的涡轮毂就成为了温压的一个理想对象。这篇论文将评述,将用于高扭矩自动变速器的常规锻件切削加工的涡轮毂转换为用一次压制/一次烧结制造的粉末冶金涡轮毂。粉末冶金涡轮毂使用的材料是FD-0405。在试验室对这种扩散合金化材料进行了评价,和报告了几个密度水平的力学性能。温压可使高应力的内花键区全面达到高密度。为了证明粉末冶金零件的适用性,进行了广泛的力学与零件的特定试验。     

Effect of Density and Processing Conditions on Oxide Transformations and Mechanical Properties in Cr–Mo-Alloyed PM steels

To improve the mechanical properties and performances of water-atomized powder metallurgy steels, it is necessary to enhance the density. Consolidating water-atomized steel powders via conventional pressing and sintering to a relative density level > 95 pct involves processing challenges. Consolidation of gas-atomized powders to full density by hot isostatic pressing (HIP) is an established process route but utilizing water-atomized powders in HIP involves challenges that result in the formation of prior particle boundaries due to higher oxygen content. In this study, the effect of density and processing conditions on the oxide transformations and mechanical properties from conventional press and sintering, and HIP are evaluated. Hence, water-atomized Cr–Mo-alloyed powder is used and consolidated into different density levels between 6.8 and 7.3 g cm⁻³ by conventional die pressing and sintering. Fully dense material produced through HIP is evaluated not only of mechanical properties but also for microstructural and fractographic analysis. An empirical model based on power law is fitted to the sintered material properties to estimate and predict the properties up to full density at different sintering conditions. A model describing the mechanism of oxide transformation during sintering and HIP is proposed. The challenges when it comes to the HIP of water-atomized powder are addressed and the requirements for successful HIP processing are discussed.

     

Sintering behaviour of Al-6061 powder produced by rapid solidification process

Abstract

Complex aluminium alloy components fabricated by powder metallurgy (P/M) offer the promise of a low cost and high strength-to-weight ratio, which meets the demands of the automotive sector. This paper describes the die compaction and sintering response of an atomised Al-6061 alloy powder containing Mg and Si produced by rapid solidification. A design of experiments is used involving three levels for each of the die compaction pressure, sintering temperature, peak temperature hold time and heating rate. Three trials were used to obtain the optimum press sinter processing conditions. Besides the mechanical properties, phase transformation and microstructure are investigated. Supplemental insight is gained through thermogravimetric analysis, differential scanning calorimetry and SEM with energy dispersive spectroscopy. Analysis of variation is used to quantify the contribution of each design variable to the mechanical properties.     

PM processing of elemental and prealloyed 6061 aluminium alloy with and without common lubricants and sintering aids

Abstract

A comparison has been made between compaction, sintering, microstructural and mechanical properties of the 6061 aluminium alloy prepared via premixed elemental (EL) and prealloyed (PA) powders (as received and degassed) with and without additions of sintering aids and various solid and/or liquid lubricants. Both EL and PA powders were cold pressed at different pressures, ranging from 250 to 770 MPa, and sintered under vacuum in the range 580–640^°C for 30–120 min. and then under pure nitrogen atmosphere for comparison. Vacuum degassing of the PA powder provided better compressibility and thus higher green densities than those for the as received PA or the premixed EL powder compacts pressed at compaction pressures ≥340 MPa. Near full sintered densities of , ～98%TD were obtained for both EL and PA 6061 Al alloys. Degassed PA Al with 0·6 wt-% paraffin wax (PW) or with only 0·12 wt-%Pb addition as sintering aid and no lubricant, and premixed EL with only 0·12 wt-%Pb addition and no lubricant gave the best optimum properties. It became apparent that additions of some solid lubricants such as lithium stearate (LS) and acrawax to both the premixed EL and PA powders provided reasonable green densities, but had deleterious effect on sintered densities and microstructures, particularly under vacuum sintering. Heating data curves during the sintering cycle, revealed formation of both transient and persistent liquid phases for the EL and mainly supersolidus liquid phase sintering (SLPS) mechanism for the PA. Tensile properties of the degassed, vacuum or nitrogen sintered PA Al alloy in T6 condition were higher than those of the equivalent alloy prepared by EL mixing with the former giving a tensile strength of 330 MPa and 6–8% elongation to failure, which are similar to those of the commercial (wrought) 6061 Al alloys.     

The properties of tungsten processed by chemically activated sintering

Two tungsten powders have been treated with small concentrations of sintering activators to provide for enhanced low temperature sintering. The experimental study focused on the determination of the processing effects on properties such as sintered density, grain size, hardness, and strength. Variables in the plan included tungsten particle size, type of activator, amount of activator, compaction pressure, and sintering temperature. The sintered density is found to have a dominant effect on strength and hardness. The various processing variables are analyzed in terms of their effects on density. At high sintered densities, grain growth acts to degrade the strength. Additionally, the nature of the sintering activator influences the fracture strength. In this study optimal strength occurred with a 0.7 μm tungsten powder treated with 0.29 wt pct Ni, sintered at 1200 °C for one hour. The resulting density was 18.21 g/cm³, with aR _A hardness of 69 and a transverse rupture strength of 460 MPa.     

电解铁粉的制备及压缩烧结性能

摘要：以电解铁片为原料制备了电解铁粉并且研究了其纯度及硬度，同时以某电解厂生产的电解铁粉为原料，研究了电解铁粉的压缩及烧结性能。结果表明，最佳因素组合下电解得到的电解铁片及电解铁粉纯度(质量分数)分别达到99.98%和99.99%；电解铁粉压坯密度随着压制压力的增加而增大，粒径大的铁粉更利于压制成型，但会导致孔隙尺寸大变大且分布不均匀；铁粉烧结坯密度随着烧结温度的升高而增大，同时随保温时间增加增长缓慢，因此在实际生产中应通过适当提高烧结温度和缩短烧结时间，进而提高烧结效率。     

高线斯太尔摩风冷线冷却模型

摘要：以电解铁片为原料制备了电解铁粉并且研究了其纯度及硬度，同时以某电解厂生产的电解铁粉为原料，研究了电解铁粉的压缩及烧结性能。结果表明，最佳因素组合下电解得到的电解铁片及电解铁粉纯度(质量分数)分别达到99.98%和99.99%；电解铁粉压坯密度随着压制压力的增加而增大，粒径大的铁粉更利于压制成型，但会导致孔隙尺寸大变大且分布不均匀；铁粉烧结坯密度随着烧结温度的升高而增大，同时随保温时间增加增长缓慢，因此在实际生产中应通过适当提高烧结温度和缩短烧结时间，进而提高烧结效率。     

On development of press and sinter Al–Ni–Mg powder metallurgy alloys

Abstract

The objective of this research was to initiate the development of powder metallurgy alloys based on the Al–Ni–Mg system. In doing so, binary (Al–Mg) and ternary (Al–Ni–Mg) blends were prepared, compacted and sintered using elemental and master alloy feedstock powders. Research began with fundamental studies on the sintering response of the base aluminium powder with additions of magnesium. This element proved essential to the development of a well sintered microstructure while promoting the formation of a small nodular phase that appeared to be AlN. In Al–Ni–Mg systems a well sintered structure comprised of α aluminium plus NiAl₃ was produced at the higher sintering temperatures investigated. Of these ternary alloys studied, Al–15Ni–1Mg exhibited mechanical properties that were comparable with existing commercial 'press and sinter' alloys. The processing, reaction sintering and tensile properties of this alloy were also found to be reproducible in an industrial production environment.     

High-performance Ni3Al synthesized from composite powders

Specimens of Ni₃Al + B of high density (>99.3 Pct RD) and relatively large dimension have been synthesized from composite powders through processes of replacing plating and electroless Ni-B plating on Al powder, sintering, and thermal-mechanical treatment. The uniformly coated Ni layer over fine Al or Ni core particles constituting these coating/core composite powders has advantages such as better resistance to oxidation relative to pure Al powder, a greater green density as a compacted powder than prealloyed powder, the possibility of atomically added B to the material by careful choice of a suitable plating solution, and avoidance of the expensive powder metallurgy (PM) equipment such as a hot isostatic press (HIP), hot press (HP),etc. The final Ni₃Al + B product is made from Ni-B-Al and Ni-B-Ni mixed composite powders by means of traditional PM processes such as compacting, sintering, rolling, and annealing, and therefore, the dimensions of the product are not constrained by the capacity of an HIP or HP. The properties of Ni₃Al composite powder metallurgy (CPM) specimens tested at room temperature have been obtained, and comparison with previous reports is conducted. A tensile elongation of about 16 Pct at room temperature was attained.