Compacted Iron Research Articles

Evaluation of Secondary Cathodes for Glow Discharge Mass Spectrometry Analysis of Different Nonconducting Sample Types

The use of different secondary cathodes is evaluated for the analysis of solid, nonconducting samples by means of dc glow discharge mass spectrometry. Optimum discharge conditions and analytical characteristics are reported for the analysis of a compacted iron ore sinter and a solid glass sample, both with known composition. These conditions seem to differ significantly for the two samples under consideration. This difference is assumed to be caused mainly by the electrical characteristics of the sample. The electrical resistivity of the sample is indeed found to be an important factor, determining the capabilities of the technique, especially with respect to the detection power.

Effect of binder residues on sintering of injection moulded iron compacts : H.C. Chen et al (National Taiwan University, Taipei, Taiwan)

Effect of binder residues on sintering of injection moulded iron compacts : H.C. Chen et al (National Taiwan University, Taipei, Taiwan)

Press powder flow compaction of iron powder with controlled particle size distribution : S. Takahashi, T. Nakagawa (Nihon University, Narashino, Japan), J.Japan Soc, Powder and Powder Metallurgy, vol 40, no 9, 1993, 908–913. (In Japanese)

Metal matrix composites, based on M3/2 high speed steel and reinforced with two different percentages of TiCN (2.5 and 5 wt%), were manufactured following a conventional powder metallurgy route: mixing, compacting and sintering. The carbide and base material powders were dry mixed and uniaxially compacted at 700 MPa. After this, vacuum sintering was carried out at different temperatures to study the sinterability of manufactured composites. Effects of sintering temperature on sintering density, dimensional change and hardness with temperature were measured, and this study was completed with a dilatometric analysis. Materials were sintered at optimum sintering temperature (1275 °C), and transverse rupture strength and wear behaviour of sintered materials was examined.

Infiltration of silver into sintered iron compacts : H-N, Huang, T. Watanabe (Waseda University, Tokyo, Japan), J.Japan Soc. Powder and Powder Metallurgy, vol 40, no 9, 1993, 919–922. (In Japanese)

Infiltration of silver into sintered iron compacts : H-N, Huang, T. Watanabe (Waseda University, Tokyo, Japan), J.Japan Soc. Powder and Powder Metallurgy, vol 40, no 9, 1993, 919–922. (In Japanese)

銅および鉄圧粉体の比抵抗に及ぼす直流パルス通電の効果

The relationship between the number of pulses and the specific resistivity for the copper and iron powder compacts has been investigated to reveal the phenomena which are caused between powder particles in the early stage of the spark sintering process. The results are summarized as follows: The values of specific resistivity of the both powder compacts decrease with increasing the number of pulses, and the rates of decrease of specific resistivity increase with decreasing the applied punch pressures. The limited changes of the relative densities of compacts are observed in this continuously pulse discharge process. Therefore, it is considered that the specific resistivity of compacts are decreased, not because their relative densities are changed but because the properties of the contact area between powder particles are changed by the pulse discharge. Where, this change of the properties is caused by the dielectric breakdown of the oxide film between the powder particle surfaces in the pulse discharge process. The metallic contact parts are created between powder particles after this dielectric breakdown. It is cosidered that the spark can not be caused in these metallic contact parts.It is suggested on the basis of the simple model of electric resistance of a compact that the fraction of the metallic contact area created by the dielectric breakdown of the oxide film is extremely small.It is assumed on the basis of the first order equation of the chemical reaction that the rate of decrease of the area fraction of the oxide film between powder particles per one pulse discharge is proportional to this retained area. The relationship between the number of pulses and the specific resistivity of compacts can be explained quantitatively by this assumption.

Creep of highly-porous iron compacts under conditions of cyclic ? ? ?-transformations

Features of the creep of highly-porous iron compacts with cyclic α ↔ γ-transformation are studied. Possible reasons are explored for acceleration of deformation during α → γ-transformation and sintering of compacts with γ → α-transformation.

Electroless Nickel Coating of Sintered Iron Compacts

Sintered iron specimens with a 9% porosity level were successfully coated by electroless nickel deposition using a hypophosphite bath. The problems encountered during the deposition process are discussed. Some important deposit characteristics such as composition, thickness, hardness, and adhesion strength of the deposit are also reported for both as deposited and coated specimens heat treated at 400°C for 1 h in a vacuum. PM/0650

Advances in powder metallurgy of soft magnetic materials

This paper discusses two new powder metallurgy processes that provide increased soft magnetic performance over conventional techniques. The first is a process involving elevated compaction temperatures which enable sintered densities of 7.59 g/cm/sup 3/ for iron containing 0.35% by weight of phosphorus. Maximum permeabilities exceeding 6,000 with saturation inductions of 19,730 G are typical results utilizing this process. The second process involves producing a thin plastic coating on discrete iron particles. Upon compaction, the plastic coating between particles provides a material with constant permeability up to 100,000 Hz and mechanical strength of 250 MPa. Plastic coated iron compacts provide a moldable material with isotropic high frequency soft magnetic properties.

Granular films of iron oxide prepared by aerosol deposition for the detection of organic vapours

Gas-sensitive layers of iron oxide microparticles have been obtained by nebulization of iron oxalate solution, size-selective deposition of the dried aerosol particles and final heating at 350°C to transform the oxalate to iron oxide. Clustered layers of spherical particles with a size of about 800 nm resulted. For comparison sputtered iron films were oxidized at the same temperature to yield oxide films of compact morphology. With secondary-neutral and secondary-ion mass spectrometry film thicknesses, elemental compositions and chemical states were measured. All prepared iron oxides were determined to be primarily Fe 2O 3. The granular as well as the compact iron oxide films were investigated concerning their change in electrical conductivity upon exposure with organic gases contained in air. The sensitivities at 350°C for propane and methane, but not for benzene, were found to be higher for the granular films. The response times were not much different between the particulate and the compact iron oxide layers.

Influences of additives on the machinability of PM iron compacts

Influences of additives on the machinability of PM iron compacts

Methods for enhancement of sintering of injection moulded pure iron compacts

Despite the acute drug-related and behavioural risk factors for experiencing a drug overdose, few remote childhood experiences have been examined as risk factors for subsequent later life overdose risk. Parental heavy drinking has been associated with some later life negative outcomes, but little is known regarding the impact on drug overdoses, especially among people who inject drugs. Given the current overdose crisis in North America, we sought to evaluate the impact of parental heavy drinking on later life non-fatal overdose among people who inject drugs in Vancouver, Canada.Data were derived from two prospective cohort studies of community-recruited people who inject drugs in Vancouver between December 2012 and May 2016. We employed multivariable generalized estimating equations to examine the relationship between parental heavy drinking and non-fatal overdose in the past six months.Among 327 eligible participants, 111 (33.9%) reported parental heavy drinking and 95 (29.1%) reported a non-fatal overdose at least once during the study period. In a multivariable analysis, experiencing parental heavy drinking remained independently associated with non-fatal overdose (adjusted odds ratio: 1.69; 95% confidence interval: 1.07–2.66) after adjustment for a range of socio-demographic and drug using confounders.These findings suggest long-term negative impacts of parental heavy drinking, on subsequent risk taking or other mechanisms associated with overdose. Current overdose prevention efforts may benefit from the evaluation of life course vulnerabilities that may be amenable to earlier interventions.

鉄系焼結材料の強度評価

The tensile strength of sintered iron and alloyed iron compacts have been analyzed statistically by using three types of iron powders produced by different process. The results obtained were summarized as follows:(1) The tensile strength of all sintered iron compacts were scattered according to the normal distribution curves in spite of difference in material and the sintered density.(2) Sintered iron compacts produced by fine powder showed the highest tensile strength. The coefficient of variation in tensile strength had a tendency to become high as the iron powder particle size is increasing and the density of sintered compact is decreasing.(3) The tensile strength and its coefficient of variation in sintered compacts produced by blended iron powder were similar to those of compacts produced by single powder.(4) The coefficient of variation in tensile strength of sintered alloyed iron compacts was increased with addition of Cu, while the addition of Ni had slightly influence on the coefficient of variation.

Detection of gases in closed pores of incompletely densified copper and iron compacts : H. Ito, K. Hayashi (University of Tokyo, Tokyo, Japan)

Detection of gases in closed pores of incompletely densified copper and iron compacts : H. Ito, K. Hayashi (University of Tokyo, Tokyo, Japan)

電磁成形法による鉄圧粉体の衝撃圧縮

Electromagnetic forming has been used for plastic deformation technology of metal materials. In this paper, shock compaction of iron powder compacts by electromagnetic forming was attempted to investigate a possibility of the electromagnetic pressure sintering. An iron compact was put into a solenoid coil and a strong pulse current was passed through the coil, then the compact was compressed by electromagnetic pressure. But, the compact was broken to pieces by the strong electromagnetic filed. The destruction was caused by poor electric conductivity and low toughness of the compact. Accordingly, the compact was pre-sintered in a vacuum furnace to improve its electric conductivity and toughness. The electromagnetic forming of the pre-sintered compact increased the relative density. Therefore the processing may be applicable to powder pressure sintering.

鉄焼結体への銅溶浸による溶浸一般式の検討

鉄焼結体への銅溶浸による溶浸一般式の検討

ＨＩＰ処理した鉄系焼結材料の疲労き裂進展に及ぼす組織の影響

Fatigue crack growth of the sintered ferrous materials by HIP has been investigated taking the microstructures and the pattern of fractured surfaces into account.The results obtained are summarized as follows:(1) In the case of constant stress ratio, the fatigue crack growth rate(da/dN) of sintered materials by HIP with diffusion alloyed powder had a tendency to become slower than that of sintered materials by HIP with prealloyed and mixed elemental powders under the same stress intensity factor range(ΔK). The material constant value (m) in da/dN=C(ΔK)m was found in the range of 3.8 to 5.3, which was the same as that of wrought materials. Sintered iron compacts showed higher da/dN and m values than those of sintered materials by HIP.(2) The ΔKth(da/dN<10-9m/cycle) of sintered iron compacts was higher than that of sintered materials by HIP. The influence of stress ratio was recognized with the relationship between da/dN and ΔK of any sintered materials by HIP.(3) Fatigure crack grew preferentially in the ferrites as forming the slip bands close together. The behavior of fatigue crack growth was distinctly dependent on the microstructures, the cracks propageted linearly through the pearlites, and the cracks penetrated through or bypassed the cementites.(4) The fractured surface reflected the local intergranular fracture in the region of low crack growth rate(da/dN<10-9m/cycle). On the other hand, the striation like pattern was mainly observed in the region of high crack growth rate(da/dN=10-7-10-9m/cycle). As the stress ratio was increased, unevenness of the fractured surface was more distinguished.

Kinetics and Mechanisms of Re-oxiation of Freshly Reduced Iron Compacts.

Hematite compacts were isothermally reduced with hydrogen at 973-1273 K. The reduction was carried out up to 90-95% reduction degree using thermogravimetric technique. The reduced products were subjected to re-oxidation in dry air. The rates of re-oxidation at 473-1073 K as a function of time was studied. Microscopic examination, and porosimetric measurements were used to elucidate the kinetics and mechanisms of reduction and re-oxidation. During reduction of iron oxide, the rate was increased with temperature and the structure of sponge iron produced was temperature dependent. Three transition temperatures were identified during re-oxidation. Reoxidation at the initial stages was controlled by interfacial chemical reaction whereas at both the intermediate and later stages, solid-state diffusion was the rate controlling step.

Flow compaction of iron powder with controlled particle size distribution: S. Takahashi, T. Nakagawa (University of Tokyo, Tokyo, Japan)

Flow compaction of iron powder with controlled particle size distribution: S. Takahashi, T. Nakagawa (University of Tokyo, Tokyo, Japan)

Efficient sinter hardening of low alloy iron powder compacts in a belt furnace: D. Warga, C. Lindberg (Hoganas AB, Hoganas, Sweden)

Efficient sinter hardening of low alloy iron powder compacts in a belt furnace: D. Warga, C. Lindberg (Hoganas AB, Hoganas, Sweden)

Changes in pore structure of sintered iron compacts of diffusion in of alloy elements: T.-W. Lim and K. Hayashi (University of Tokyo, Tokyo, Japan), J Japan Inst of Metals, Vol 56, No 7, 1992, 828–832. (In Japanese)

Changes in pore structure of sintered iron compacts of diffusion in of alloy elements: T.-W. Lim and K. Hayashi (University of Tokyo, Tokyo, Japan), J Japan Inst of Metals, Vol 56, No 7, 1992, 828–832. (In Japanese)