元素粉末预合金化对烧结合金钢组织和性能的影响

为充分发挥合金元素提高铁基烧结材料强度的作用,加快我国中、高强度铁基粉末冶金产品的发展,通过试验分析比较了混合粉、部分(扩散)预合金粉、完全预合金粉对镍钼铜合金钢显微组织和力学性能的影响。结果表明:显微组织取决于成分的分布均匀性,其中Ni和C的均匀性影响最大;混合粉烧结钢的显微组织主要由珠光体、铁素体构成,部分预合金粉烧结钢的显微组织由珠光体、铁素体、贝氏体和马氏体组成,完全预合金粉烧结钢的显微组织主要为铁素体基体上分布碳化物颗粒;经过部分预合金化和完全预合金化后,材料的力学性能有明显提高,淬火态抗弯强度分别为968MPa和1027MPa,冲击韧性分别为26J/cm2和30J/cm2。     

球磨时间及预氧化方式对粉末冶金M3:2高速钢组织及力学性能的影响

采用球磨混合和预氧化活化烧结法制备新型粉末冶金M3:2高速钢,重点研究球磨时间和预氧化方式对其致密度、微观组织和力学性能的影响。利用FEI Quanta 250 FEG型扫描电镜对高速钢组织进行显微分析,同时测试样品硬度、抗弯强度和断裂韧性等力学性能。结果表明,球磨72 h且负压干燥时,M3:2高速钢具有最优的碳含量、致密度和力学性能组合。烧结后的抗弯强度最高为3 092 MPa,热处理后的弯曲强度为4 786 MPa。经过干燥增氧之后,负压干燥粉末具有较低的氧含量,烧结后的氧含量最低可降到17×10-6,表现出更好的致密度和力学性能。     

含Fe-Mo-B预合金粉的铁基合金温压行为

为深入了解含Fe-Mo-B预合金粉的铁基合金的温压行为,研究了不同成形温度、不同Fe-Mo-B预合金粉含量对压坯密度、弹性后效以及样品显微组织和力学性能的影响。结果表明:与常温成形相比,温压能够明显提高压坯密度,在120℃时含10%和15.4%Fe-Mo-B预合金粉的压坯密度较室温压制的分别提高0.34 g/cm3和0.32 g/cm3;温压成形能显著降低压坯的弹性后效;温压工艺的温度效应对铁基合金的温压影响不明显;压坯烧结后,温压坯件的径向收缩小于室温压坯;温压可以改善合金的显微组织,从而提高其力学性能。     

新开发的低松装密度雾化粉末的性能

为满足市场需求,开发出了一种低松装密度雾化铁粉,Ancorsteel(R) AMH.这种材料主要用在密度较低的场合,在那里生坯强度与烧结体强度对粉末冶金零件的使用性能是至关重要的.本文将着重于以添加石墨的预混合粉与铜+石墨的预混合粉的方式,对Ancorsteel AMH与传统海绵铁粉之间生坯与烧结态的性能进行比较.将要...     

粉末冶金工艺对纯铁软磁材料性能的影响

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（M_s）偏小、矫顽力（H_c）偏大的现象,M_s为205.51 emu·g-1,Hc为7.9780 Oe。     

球磨对雾化铁基合金14YWT粉末烧结性能的影响

采用惰性气体雾化法制备铁基预合金粉末14YWT,然后进行高能球磨;对雾化粉末和球磨后的雾化粉末分别进行压制和真空烧结,通过测定烧结收缩曲线研究粉末的烧结行为,并分析其烧结机制。结果表明:未球磨的雾化粉末在20～770℃因受热发生膨胀,在770～1250℃粉末颗粒间出现烧结收缩,膨胀率略有降低,在1 250℃发生明显的烧结收缩,原始颗粒边界逐渐消失;烧结温度从1 250℃提高到1 400℃时,粉末原始颗粒界面基本消失,再结晶基本完成,密度、孔隙度和硬度分别为6.56 g/cm3,1.03%和70.2HB。球磨后的雾化粉末由于粒度更细,并形成高密度位错和缺陷浓度,在1 100℃发生明显的烧结收缩,1 400℃时再结晶基本完成,合金的密度和硬度分别为7.26 g/cm3和71.7HB,明显高于未球磨的雾化铁基合金粉末烧结体的相应密度和硬度。     

德国水雾化铁粉还原炉

粉末冶金是我国目前急需大力发展的重要工业。为提高粉末冶金制品的性能,采用高品质铁粉是很重要的前提。制造低密度水雾化铁粉是各国粉末冶金界努力的方向。一般情况下,水雾化铁粉的松装密度为2.8～3.09/cm~3。在水雾化铁粉生产中,增大雾化用水的压力和提高喷向铁水流的水流量可获得不规则形状的铁粉,并降低其松装密度。但是,这样做却难以制得适合工业化生产的、经济的低密度铁粉。西德曼内斯曼公司米尔厂近年来在这个领域有所突破,开发了生产低松装密度(2.5g/cm~3)铁粉的技术,由这种铁粉压制出生坯强度很高的中等密度压坯。这种铁粉的生产关键在于调整好雾化角度和采用高温(在1000～1200℃,而通常在900℃左右)还原工艺。     

俄罗斯的粉末冶金及其主要企业概述

粉末冶金是俄罗斯冶金生产的优先发展方向之一,在世界粉末冶金领域具有很强的生命力.简述了俄罗斯粉末冶金工艺技术特点;介绍了俄罗斯从事铁粉、有色金属粉、合金粉、硬质合金、结构零件、电触头材料和抗摩擦材料生产的主要企业,纳米粉末、雾化法制粉和高速电脉冲等离子烧结工艺是其工艺技术的亮点.     

高温还原对水雾化铁粉压缩性的影响

以莱钢集团粉末冶金有限公司LAP100.29水雾化铁粉为原料,在900℃下进行高温氢气还原,研究高温还原处理对水雾化铁粉的显微硬度、化学成分、松装密度、流动性、压缩性等性质的影响,以期对实际生产起到一定的借鉴和指导作用。结果表明:经900℃高温氢气还原处理后的铁粉纯度提高,大部分样品的流动性提高约2 s/50 g,松装密度提高0.1 g/cm3左右,压制密度提高0.1 g/cm3以上,而粉末显微硬度大幅降低至69～89 HV。在600 MPa下铁粉压制密度大部分达到7.15 g/cm3以上。     

掺杂稀土的高速钢预合金粉对WC基钢结硬质合金组织和性能影响

钢结硬质合金是一种性能介于硬质合金与高速合金钢的材料,可以取代部分传统硬质合金与工模具钢在模具和切削刀具领域的应用。本研究采用气雾化法制备稀土掺杂高速钢预合金粉作为钢结硬质合金的粘结相,制备了掺杂稀土的WC基钢结硬质合金,用扫描电子显微镜观察了样品的显微组织和断口形貌,并对合金的密度、硬度、抗弯强度和冲击韧性进行了检测。研究结果表明,在高速钢预合金粉中掺杂稀土元素能提高WC基钢结硬质合金的密度,改善其硬度、抗弯强度、冲击韧性等力学性能;添加Ce元素的效果好于Y元素;采用掺杂稀土元素Ce的高速钢预合金粉制备的WC基钢结硬质合金力学性能优于传统球磨混料法掺入稀土元素Ce制备的WC基钢结硬质合金。     

添加羰基铁粉提高铁基合金烧结密度的研究

在Ｆｅ－Ｎｉ－Ｃｕ－Ｍｏ－Ｃ系合金中添加羰基铁粉，改善了粉料的压制性能和粉坯的烧结性能。以钢模成形、一次烧结工艺制造的合金，密度达７．５２ｇ／ｃｍ＾３，相对密度９５．２％，提高了制品的力学性能。     

高密度铁基粉末冶金零部件制造原料的研究

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。     

Characterization,Physical and Mechanical Behavior of Sintered Atomized Iron–Zinc Stearate Composite

Powder metallurgy is an effective method to process the iron component in near net shape. In this paper, the influence of particle size, lubricant and compaction load on the physical and mechanical properties of the sintered iron–zinc stearate composite sample has been investigated. Atomized iron powders of particle size 100–200 and 200–300 mesh with zinc stearate 2.5, 5.0 and 7.5 wt% were used for preparing the samples. Green samples were prepared by cold compaction at various loads of 200, 180 and 160 KN and the sintering is done at 500 °C. The physical properties and the mechanical properties such as density, hardness and compression strength have been measured for the sintered samples. Scanning electron microscope was used to characterize the atomized iron powders and the sintered samples. It were confirmed that the shape of atomized iron powder particles were irregular, dendritic and acicular. Energy dispersive spectroscopy was used to identify the elemental compositions of powders and the sintered samples. Taguchi (L₁₈) method was effectively used to develop the regression model and describe the contribution of the input parameters in compressive strength, density, and hardness. The highest effect on density was powder particle size followed by compaction load and lubricant wt%. The Hardness value increased with increase in the powder particle size and compaction load and decreases with increase in the lubricant wt%. The compression strength increased with increase of compaction load and decrease of lubricant wt% and particle size.     

机械活化W-Cu粉末的压力烧结

为了改善工艺与提高W-Cu合金的密度及性能，在对原料粉末进行机械活化处理后进行压力烧结，包括加压烧结与气压烧结，制备出W-Cu合金，考察其烧结合金的组织与性能。结果表明，机械活化能有效的促进烧结。加压烧结与气压烧结都能够有效地促进合金的致密化。加压烧结时，在加压方向上有明显的收缩，但在与加压垂直的方向上却略有膨胀。而气压烧结则可以使合金在各个方向上收缩。烧结组织细密、均匀．相对密度达98％以上。压力烧结是提高W-Cu合金密度的有效手段。     

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.

     

预混合粉材料烧结

深入了解预混合粉材料的烧结,对促进铁基粉末冶金零件产业的发展具有重要作用.这涉及到固态烧结与液相烧结两个方面.本论文讨论了添加下列合金元素粉末的预混合粉材料的烧结:(1)石墨粉;(2)镍粉与石墨粉;(3)铜粉与石墨粉;(4)磷铁粉状的磷;(5)硼铁粉状的硼.另外,还讨论了这些材料的显微组织与力学性能.     

THE EFFECT OF PHOSPHORUS ADDITIONS ON THE TENSILE,FATIGUE, AND IMPACT STRENGTH OF SINTERED STEELS BASED ON SPONGE IRON POWDER AND HIGH-PURITY ATOMIZED IRON POWDER

Abstract

The mechanisms operating during the sintering of iron-phosphorus PM alloys are discussed, as well as the factors contributing to the unique combination of strength, ductility, and toughness that is characteristic of these materials. Alloying methods are reviewed with special reference to powder compressibility, tool wear during compaction, and homogenization during sintering. The preferred production method is to add phosphorus in the form of a fine Fe₃P powder to iron powder. The mechanical properties of a number of sintered steels made with and without Fe₃P additions to sponge iron or to high-purity atomized iron powders are reported. Use of atomized powder makes it possible to reach extremely high density by single pressing and the resulting phosphorus-containing sintered steels have very high ductility and impact strength. The fatigue strength is related linearly to the tensile strength, with a correlation coefficient of 0·91. It is concluded that structural factors other than those that control ductility and toughness are responsible for the fatigue resistance of sintered steels.     

PM processing and characterisation of Ti–7Fe low cost titanium alloys

Abstract

This work studies a set of low cost beta alloys with the composition Ti–7Fe, processed by conventional powder metallurgy (PM). The materials were prepared by conventional blending of elemental Ti hydride–dehydride powder with three different Fe powder additions: water atomised Fe, Fe carbonyl and master alloy Fe–25Ti. The optimal sintering behaviour and the best mechanical properties were attained with the use of Fe carbonyl powder, which reached a sintered density of up to 93% of the theoretical density, with UTS values of 800 MPa in the ‘as sintered’ condition. Coarse water atomised powder particles promoted reactive sintering, and coarse porosity was found due to the coalescence of Kirkendall porosity and by the pores generated during the exothermic reaction between Ti and Fe. The addition of Fe–25Ti produced brittle materials, as its low purity (91·5%) was found to be unsuitable for formulating Ti alloys.     

用机械活化与化学活化方法制备 W-Cu 合金

为了改进制备工艺和提高W－Cu合金的性能,对原材料粉末做了机械活化和化学活化处理,通过成形和烧结制备了W－Cu合金,考察了经机械活化和化学活化后粉末的变化,观察了烧结合金的组织、测试了合金的密度等性能。结果表明,机械活化可以使粉末颗粒变细,至亚微米乃至纳米级、比表面增大、缺陷增多,并使铜在钨中具有一定溶解度。化学活化可以在粉末颗粒表面形成微量合金元素的较均匀分布,并通过反应形成高活性层。二者都能使粉末的活性提高,对经活化处理的粉末施以烧结可以获得较高密度和性能的W－Cu合金。