Electrolytic Iron Powder Research Articles

SOME ECONOMIC FACTORS IN THE PRODUCTION OF SINTERED FERROUS COMPONENTS

The economics of producing sintered ferrous components depends to a large extent upon the characteristics of the basic iron powder. To satisfy design specifications in respect of mechanical properties, sintered materials usually need to be more highly alloyed than the cast and wrought materials against which they compete, so that the cost of materials has tobe carefully balanced against the properties required in the finished component.The evaluation of some factors for electrolytic, atomized, and sponge iron powders is outlined. The results indicate that the cheaper powders are economically more advantageous, since with materials of comparable density the properties of those based upon electrolytic iron are not sufficiently superior to compensate for their higher cost.Attempts to obtain better properties with cheaper powders by pressing to high density met with unexpected failure, except when the powders were treated in hydrogen before compaction.

Linear shrinkage of metal powder compacts during sintering

The influence exerted by various factors (particle size, particle size distribution, ultrafine powder addition, sintering temperature, etc.) on the linear shrinkage ratio during sintering was examined. Electrolytic, atomized, and ultrafine copper powders, as well as electrolytic iron powder, were used.

Studies on the Flash Resistance Sintering of Metallic Powders

Experimental studies were made on the flash resistance sintering of iron powder. The influences of electric charging and processing conditions on the mechanical properties of sintered compacts were studied. The results obtained are as follows.(1) In order to obtain high density products, pressure more than 1 ton/cm2 and correct sintering time are necessary.(2) The density and tensile strength of the sintered compacts from electrolytic iron powder are higher than those of compacts from Hoganas iron powder.(3) The finer the particle size of the iron powder used, the denser the structure of the sintered compacts obtained. Among the compacts blended in various weight ratios of coarse to fine iron powders, the compact blended with same weight of powders showed the highest sintered density.(4) To get the sintered products with high density and uniform structure, acute angle and high projection on the sample are prohibited.(5) Application of thin refractory metal plates between the electrode and the metal powder is effective to obtain high density sintered products.(6) On the apparent density and tensile strength of the sintered compacts, the influence of the input power is greater than that of sintering atmosphere.

The laws governing the formation of electrolytic iron powders (E)

1. Electrolytic iron powders may be formed either above or below the limiting current. 2. Powders are formed below the limiting current as a result of trivalent iron hydrooxide occurring in the epielectrode layer. 3. Adding ascorbic acid to the solution prevents the formation of powder-like deposits by preventing the oxidation of bivalent iron ions.

Continuous Production of Iron Strip from Metal Powder

A continuous method of producing iron strip from powder has been developed. Iron powder directly conversed to green strip by roll compacting, and which was continuously sintered, hot rolled and cooled in hydrogen atmosphere and coiled up. The effects of various continuous powder rolling factors, such as the sintering temperature, roll speed, and hot rolling lood on the properties of hot rolled strip were investigated with Husquvarna Star electrolytic iron powder and Höganäs sponge iron powder.In general, with increasing the sintering temperature and hot rolling lood the physical and mechanical properties of iron strip by powder rolling were improved, whereas the effect of roll speed was different, depending upon the sinterability of iron powder. These properties obtained were considerably well for the powder metallurgical product, although the sintering time was short. According to the repeated hot rolling or annealing and cold rolling, the pro. perties of the iron strip were equal to those of the conventional iron strip, especially the one made from Husquvarna Star iron powder showed superior magnetic properties.

Kinetics of reduction of iron oxide with carbon monoxide and hydrogen

AbstractThis investigation was undertaken to determine the rate controlling step in the reduction of iron oxides with hydrogen and carbon monoxide. For the reduction of porous hematite pellets, and bars it was found that the reduction rate is controlled by the counterdiffusion of reactant gas and product gas between the reaction zone and the main gas stream.The reduction specimens were spheres ranging in size from 1.5‐ to 4.4‐cm. diameter and 5.1‐ by 7.6‐cm. bars either 0.69 or 1.24 cm. thick. They were prepared from electrolytic iron powder, partially oxidized in a rotary kiln. The final oxidation of the specimens to hematite was accomplished by firing them at 1,149°C. in an oxidizing atmosphere. The bulk density was 3.5 g./cc. The specific surface area was 0.08 sq.m./g. and the void faction was 0.31. The oxide specimens were reduced in streams of pure hydrogen or carbon monoxide at temperatures between 700° and 1,200°C. The reduction was followed by measuring the sample weight during the reaction. Reduction rates were studied at system pressures of 1 and 2 at.The samples reduced step by step, to magnetite, to wüstite, and finally to iron. A shell of reduction, clearly visible in sections of partially reduced specimens, moved concentrically into the core of the samples. Ahead of the receding interface the specimens were known to be pervious to the reactant gases. This led to the conclusion that the gas composition at the interface was in equilibrium with the oxide phases present.Except for the removal of the last portions of oxygen at the lower reduction temperatures, the course of the reduction followed Fick's first law of diffusion. Values of the diffusion co‐efficients, determined from the experimental data, were in close agreement with values predicted from empirical equations. Varying the total pressure of the system had no effect on the rate of reduction, which is consistent with the equations developed from Fick's law for the diffusion‐controlled reaction under investigation.It is speculated that the retarding of the reduction reaction at the lower reduction temperatures is due to the entrapment of oxide inside shells of iron, which are impervious to the reducing gas. Reduction of the trapped oxide then proceeds by solid state diffusion in a manner proposed by Edström (6).

Electrolytic Iron Powder from a Caustic Soda Solution

Conditions for electrolytic deposition of iron powder from a slurry of iron III oxide in caustic soda solutions were investigated. The variables that influence the deposition the most were temperature (90°C), caustic soda concentration (600–800 g/l), and low current densities. Results from pilot‐plant studies were in good agreement with laboratory findings. Several photomicrographs of the deposits are included. Physical and chemical properties of the powders are listed. Results show that a ductile, dendritic deposit was obtained that could be ground up easily. The size of the dendrites was influenced greatly by conditions of deposition. Particle size distribution, particle shape, ductility, flow rate, purity, and compactability of several powders were examined. Tensile strength and elongation of sintered compacts were also studied.

Electrolytic Iron Powders—Production and Properties

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鉄粉焼結体の研究（第3報）成形圧力の相違が焼結体に及ぼす影響について

The crushed electrolytic iron powders were passed through a 325-mesh sieve, and annealed at 750° in H2. Then, these powders were pressed at 0∼20 t/cm2 and sintered at 350∼1450° for 2\frac12 hrs in H2. The same measurements as those in the 1st report were carried out with respect to the specimens thus obtained. The experimental results are summarized as follows:—(1) The stages of the sintering temperature may be classified into three groups such as “450∼750°”, “800∼1250°” and “above 1350°”. (2) At the first sintering stage, the increase of tensile strength is due to the remarkable increase of the bond between particles with rising temperatures and increasing pressures. (3) At the second sintering stage, the increase of elongation is due to the remarkable increase of the assimilation between particles with rising temperatures and increasing pressures. (4) At the third sintering stage, the properties of the sintered compacts approach to those of the molten iron, because of the marked increase of the grain-growth between crystal grains. Furthermore, it is noted the tensile strengths and the elongations of the sintered iron compacts pressed at over 12\frac12 t/cm2 and sintered at 1300∼1400° suddenly decrease and their fractured sections glitter.