Manufacture of pure iron powder by the electrolysis of fused salts

Summary A new method is described for preparing pure iron powder from pig iron and iron sponge by the electrolysis of fused salts at a temperature of 850–900°C. The article deals with the main variables and technical and economic parameters of the process, composition of the resulting iron powder, relative density of compacts produced at various compaction pressures, apparent density of the powder, and maximum magnetic permeability of Dynamaxalloys prepared on the base of pure iron obtained by the authors and on the base of other grades of iron.Translated from Poroshkovaya Metallurgiya, No. 6 (66), pp. 1–7, June, 1968.     

Production of powders of cast iron shavings and special features of production of components from these powders. III. Structure and strength of heat-treated alloys

Conclusions Quenching the specimens from 800°C does not lead to the redistribution of the carbide in the volume of the alloys of the iron-cast iron system. The most homogeneous structure of the alloys is formed only in quenching from 900°C. However, quenching from 1000°C increases the size of voids and causes supinating of the alloys, although their homogeneity increases.Heat treatment increases the tensile strength of the alloys which contain 10–50% of low-alloy cast iron. The alloys quenched from 800°C have the maximum strength after tempering of 300°C, whereas the alloys quenched from 900 and 1000°C with a maximum strength at tempering temperatures of 250 and 200°C, respectively.The highest hardness was recorded for the alloys after quenching from 900°C. All the alloys quenched from 800, 900, and 1000°C are characterized by sufficiently higher hardenability to a depth of 4mm.An increase of the tempering temperature of the alloys in the range 200–300°C reduces their impact toughness. This fact is not in agreement with the generally recognized interpretations. However, an increase of the cast iron content usually greatly reduces the KC value of the specimens, regardless of the quenching and tempering temperatures.Translated from Poroshkovaya Metallurgiya, No. 1(325), pp. 47–53, January, 1990.     

Investigation of the magnetic properties of strip made from iron powder

Conclusions Strip with a porosity of 25%, when sintered at a temperature of 1200°C in hydrogen with a dewpoint of –30°C, is refined with respect to carbon and oxygen. At the lower sintering temperatures of 1000 and 1100°C, the carbon content is reduced to 0.03–0.02%; the quantity of not easily reducible oxides remains unaltered.With regard to the kinetics of grain growth, nonporous strip made from iron powder may be classed with steels which are coarse-grained by their prehistory.Porosity substantially affects the value of coercivity. Each 2% of pores increases the coercivity approximately by 0.1 oersted.If temperatures of 1200°C and above, with holding times of 2–3 hr are used for presintering, and temperatures of 900–1000°C for the final heat treatment of the nonporous strip, the magnetic properties of the strip can satisfy the requirements of GOST 3836-47 for low-carbon, electrical engineering thin sheet steel.     

Manufacture of metallurgical semifinished products from carbonyl nickel powder. Part 1

Summary It has been established in principle that carbonyl nickel powder can be processed into rod and strip by the technique of plastic working of sintered billets, and an appropriate technological process has been developed. The powder is pressed isostatically under a pressure of 9 kg/mm² into cylindrical billets, which are then sintered in hydrogen with a dew point between –20 and –30°C at a temperature of 1350°C for 5 h. To obtain sheet, the cylindrical billets are forged over the temperature range 1200-900°C into bars, which are first subjected to surface milling or planing and then to hot and cold rolling into sheet and strip. The resulting strip has high mechanical properties. The yield of sound metal in the processing of the powder to strip is 85%.Further work is in progress on the use of pressed sheet bars, which may be expected to shorten and simplify the fabrication process and raise the yield of sound material to 95%.Translated from Poroshkovaya Metallurgiya, No. 4 (64), pp. 29–36, April, 1968.     

Temperature dependence of the strength of sintered TiB2-Fe composites

Conclusions A study was made of the effect of temperature in the range 20–1200°C on the transverse rupture strength of sintered TiB₂-Fe materials. It is shown that alloys of the TiB₂-Fe system surpass in high-temperature mechanical strength (>900°C) the standard hard metals.Translated from Poroshkovaya Metallurgiya, No. 7(235), pp. 94–97, July, 1982.     

Effect of degree of metallization,temperature, and presssing pressure on the electrical resistivity of powdered iron ore concentrates

Conclusions Increasing the degree of metallization of an iron ore concentrate from 0 to 80% decreases the ER of a mixture of the concentrate and carbon in the temperature range 600–750°C by a factor of about 200. A considerable influence on the ER of mixtures of the concentrate and carbon is exerted by temperature: On heating from 20 to 900°C their ER falls by almost two orders. The relative influence of pressing pressure on ER in the range 0–80 MPa is negligible. The results obtained can be utilized when choosing the parameters of an induction unit for the reduction heating of an ore-carbon mixture.Translated from Poroshkovaya Metallurgiya, No. 10(286), pp. 5–8, October 1986.     

Reduction and decarburization during the annealing of atomized cast iron powder with converted gas in brovary powder metallurgy factory industrial furnaces

Conclusions An investigation into kinetics of reduction-decarburization annealing in industrial reduction furnaces employing a converted gas (CO₂/CO = 0.41 and 7–9% H₂O) countercurrent has demonstrated that, to obtain satisfactory and stable results in a short time of annealing at 900–1000°C with an atomized cast iron powder of O/C ratio 1.9–2.2, the heating of the powder to the required annealing temperature should be performed at a rate not exceeding 9 deg C/min.Translated from Poroshkovaya Metallurgiya, No. 11(179), pp. 90–92, November, 1977.     

Effects of ultrasonic vibrations on the sintering of metal-powder materials

Conclusions The results are presented of an investigation into the sintering of copper-powder compacts under the influence of ultrasonic vibrations. Specimens were sintered at temperatures of 600–900°C, the duration of application of ultrasonic vibrations being 1–5 min. The mechanical properties of specimens sintered in this manner were found to be higher than those of specimens sintered by the conventional technique.Translated from Poroshkovaya Metallurgiya, No. 9(69), pp. 31–33, September, 1968.     

Effect of Manganese and Niobium and Rolling Conditions on the Properties of Low-Alloy Steel

A series of studies was conducted to determine the optimum manganese and niobium contents in steels alloyed with the system C–Mn–Nb. Researchers also wanted to find the starting and finishing temperatures for rolling on a 2800 mill that would be best in order to obtain the necessary mechanical properties when the metal is deformed in the austenite range with small reductions.The studies established the following:– a greater improvement in strength properties is obtained from an increase in the mass content of manganese if the carbon content is reduced (0.09–0.10%) rather than increased (0.12–0.13%);– other conditions being equal, an increase in the niobium content of the steel from 0.02–0.03% to 0.04–0.06% leads to a substantial increase in strength and toughness properties and a decrease in ductility;– it was established that in terms of its effect on the yield point, microalloying steel with 0.01% niobium is equivalent to alloying with 0.30–0.40% manganese;– the percentage of the tough B component in the fracture of IPG specimens of low-alloy steel with a niobium content of 0.02–0.03 mass % can be increased from 30 to 100% by decreasing the temperature of the slab after the second pass through the two-high stand from 1020 to 980°C. For steels with a higher niobium content (0.05–0.06%), the temperature of the metal when it enters the roughing stand can be increased to 1010–1040°C without adversely affecting the standard characteristic B (%);– a decrease in the finishing temperature is accompanied by an increase in the strength and toughness properties of the metal and a decrease in ductility. Reducing the finishing temperature to below 760°C makes it possible to increase strength properties but does not change impact toughness.     

Phase Equilibria in the Ni - Sc - Ti System in the Region TiNi - Ni - Sc1.13Ni At 900°C

Physicochemical analysis methods have been applied to TiNi - Ni - Sc_1.13Ni alloys at 900°C. It is shown that the phase interactions under these conditions are unaltered by comparison with those at subsolidus temperatures. The phase based on TiNi₃, which is the most thermally and thermodynamically stable, is in equilibrium with all the other phases in the TiNi - Ni - Sc_1.13Ni subsystem. The solubilities of the components in the phases based on Ti_{50– x} NiSc_x, TiNi₃, and the Laves phase are reduced at 900°C. The temperature of the polymorphic transformation in the phase based on ScNi₅ is raised by the dissolution of titanium in it to 930°C. An isothermal section is constructed of the phase diagram for the TiNi - Ni - Sc_1.13Ni subsystem together with two polysections.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 39–46, January–February, 2005.     

Reaction of cubic boron nitride with titanium iodides

Conclusions The reaction of cubic boron nitride with the gaseous phase of titanium iodides (process duration 0.25–2.0 h, total pressure of titanium iodides 100 Pa) results in the preferential formation of TIN in the temperature range 900–1200°K and of titanium nitride and titanium diboride at 1200–1300°K.Translated from Poroshkovaya Metallurgiya, No. 10(262), pp. 57–59, October, 1984.     

Conditions of formation of lanthanum and samarium nitrides

Conclusions An investigation was carried out into the kinetics of the reactions of solid lanthanum and samarium specimens with nitrogen and ammonia. On the basis of data obtained in the present and earlier studies an examination is made of the mechanism operative in the chemical reactions of rare-earth metal nitride formation in nitrogen and ammonia streams and of optimum conditions for the bulk synthesis of rare-earth metal nitrides. It has been established that synthesis in nitrogen enables lanthanum and samarium nitrides to form at temperatures closeto T_m of the metals, i.e., 900 and 1100°C, respectively. The nitration of solid metal specimens in an ammonia stream is accompanied by the formation of intermediate products — hydrides, whose thermal stability leads to a significant difference in the synthesis temperatures of lanthanum and samarium nitrides (600–700 and 1200°C, respectively).Deceased.Translated from Poroshkovaya Metallurgiya, No. 8(200), pp. 71–78, August, 1979.     

Magnetomechanical Properties of the Alloy Nd2Fe14B

We have studied the elastic and inelastic properties of the polycrystalline ferromagnet Nd₂Fe₁₄B in the temperature range 20–550 °C. We used the low-frequency (80 Hz) internal friction method to measure the Curie point of Nd₂Fe₁₄B. We observe an internal friction peak at T ≈ 280 °C. The nature of this peak is explained in terms of the magnetoelastic saturation concept.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 87–93, March–April, 2005.     

Reaction between carbon fibers and nickel through a zirconium nitride or titanium carbide diffusion barrier

Conclusions Carbon fibers in contact with nickel suffer a pronounced loss of strength at temperatures above 600°C as a result of surface attack by the nickel (at temperatures of 800–900°C and treatment times of 10–20 h) or recrystallization (during heating for more than l h at 1000°C). There is no unique correlation between fiber structure and strength. A zirconium nitride coating fails to prevent carbon fibers from reacting with nickel. A titanium carbide coating reduces, even at high temperatures, the strength loss experienced by carbon fibers by decreasing the rate of dissolution of the material of the fibers in nickel and by slowing down the fiber recrystallization process.Translated from Poroshkovaya Metallurgiya, No. 7(175), pp. 32–35, July, 1977.     

Dependence of the mechanical properties of a P/M nickel alloy on deformation temperature and rate

Conclusions At room temperature the strength of ZhS6 nickel alloy produced by the granule metallurgy method is 1.5 times higher and its plasticity 3–4 times higher than those of the same alloy produced by the standard casting process. The P/M alloy remains superior in strength to the cast alloy up to temperatures of the order of 750–800°C, above which the strength characteristics of the P/M alloy fall below the level of properties of the cast material. The deformation of the P/M alloy varies in character depending on testing temperature, and three types of specimen fracture are possible: brittle fracture without waist formation in the temperature range 20–700°C, fracture with waist formation at 700–1000°C, and plastic deformation along the whole specimen length above 1000°C. At temperatures of 1000–1150°C the P/M alloy exhibits superplasticity: At low rates of deformation its elongation attains several hundred percent when the load is about 0.1_0.2. The elongation of the specimen, load applied, and type of stress-strain diagram depend to a large extent on the rate of deformation: As the latter is decreased, _e sharply grows and the load diminishes.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 76–80, January, 1980.     

Electrical properties of high-temperature conducting powder MoSi2-SiC-Y2O3 materials

Conclusions We examined the concentration and temperature dependences of the specific electrical resistivity in the two- (MoSi₂-SiC) and three-phase (MoSi₂-SiC-Y₂O₃) systems in the temperature range 100–1800°C. In the two-phase system, the lowest TCR in heating to 1800°C was recorded for the materials with the mass content of SiC of 20–40%. The results show that the TCR of the two-phase materials of the MoSi₂-SiC system can be reduced by adding yttrium oxide to them.Translated from Poroshkovaya Metallurgiya, No. 6(306), pp. 83–85, June, 1988.     

Ionic conduction in BaxCe0.8Pr0.2O3-

[1]Iwahara H,Yajima T,Ushida H.Effect of ionic radii of dopants on mixed ionic conductions (H++O2) in BaCeO3-based electrolytes.SolidState Ionics,1994,70/71:267. [2]Taniguchi N,Yasumoto E,Nakagiri Y,Gamo T.Sensing properties of an oxygen sensor using BaCe0.8Gd0.2O3-a ceram-ics as electrolytes.J.Electrochem.Soc.,1998,145(5):1744. [3]de Arcllano-Lopez A R,Goretta K C,Park E T,Dorris S E,Balchandran U,Routbort J L.High-temperature deformation of a BaCe0.8Y0.2O3-y+Ni composite.J.Fur.Ceram.Soc.,2002,22:2555. [4]Ma G L,Shimura T,Iwahara H.Ionic conduction and non-stoichiometry in BaxCe0.90Y0.10O3-a.Solid State lonics,1998,110:103. [5]Ma G L,Matsumoto H,Iwahara H.Ionic conduction and non-stoichiometry in non-doped BaxCeO3-a.Solid State Ionics,1999,122:237. [6]Ma Guilin,Qiu Ligan,Chen Rong.Performance of the solid oxide fuel cell based on BaxCe0.8Sm0.2O3-a.Acta Chimica Sinica (in Chin.),2002,60(12):2135. [7]Ma G L,Qiu L G,Tao W H,Zhou L,Chen R.Ionic conduc-tion in BaxCe0.8Sm0.2O3-a solid electrolyte.J.Chin.Rare Earths Soc.(in Chin.),2003,21(2):236. [8]Qiu L G,Ma G L,Wen D J.Study on preparation and electri-cal properties of Ba1.03Ce0.8Eu0.2O3-a solid electrolyte.J.Rare Earths,2004,22(5):678. [9]Qiu L G,Ma G L,Wen D J.Ionic conduction in BaxCe0.8Er0.2O3-a.Solid State lonics,2004,166:69. [10]Wang M Y,Qin L G.Mixed conduction in BaCe0.8Pr0.2O3-a ceramic.Chin.J.Chem.Phys.,2008,21:286. [11]Bonanos N.Transport properties and conduction mechanism in high-temperature protonic conductots.Solid State Ionics,1992,53-56:967. [12]Ma G L,Shimura T,Iwahara H.Simultaneous doping with La3+ and y3+ for Ba2+-and Ce4+-sites in BaCeO3 and the ionic conduction.Solid State Ionics,1999,120:51. [13]Shima D,Halle S M.The influence of cation non-stoichiome-try on the properties of undoped and gadolinia-doped barium ceres.Solid State Ionics,1997,97:443.     

Choice of grade of ferric oxide and hot-pressing conditions for the preparation of high-permeability manganese-zinc ferrites

Conclusions In the formulation of new ferrite materials for magnetic head cores starting raw materials and conditions of preparation of ferrite powders must be chosen with regard to the conditions prevailing in the hot-pressing process. The differences in the properties of the two hot-pressed ferrite batches investigated are attributable to the difference in the activities of the ferric oxide grades used (MM2 and SP) in the solid-phase synthesis and sintering reactions. Use of grade MM2 ferric oxide in the preparation of ferrite powders and hot pressing and annealing under optimum conditions (psp = 40 MPa, T_hp = 1663°K, _ih = 2.4 ksec, T_ann = 1613°K and _ann = 7.2 ksec) enable specimens to be obtained combining high values of initial magnetic permeability (_in = 10,000) and density.Translated from Poroshkovaya Metallurgiya, No. 2(230), pp. 79–82, February, 1982.     

Some features of the sintering of nickel fibers extruded from viscose-base suspensions. Part I

Conclusions The sintering of fibers extruded from a viscose-base nickel powder suspension is characterized by volume changes whose intensity varies with temperature: At 200–400°C the fibers undergo densification under the action of capillary forces set up by liquid fractions of the polymer binder being removed during the latter's thermal destruction, the mechanism of the process being analogous to that of high-intensity drying; at 400–800°C the magnitude of shrinkage is independent of temperature because the carbon-metal skeletons of the fibers are stable in hydrogen. Local agglomeration of particles in the temperature range 600–800°C too has no effect on the magnitude of the volume changes of the fibers because of the discreteness of this process; at 800–1200°C the metallic phase sinters by a diffusion-viscous flow mechanism. To the characteristic temperature ranges of densification of fibers extruded froma viscose-base nickel powder suspension there correspond characteristic temperature ranges of polymer binder removal, which points to the existence of a relationship between these two processes.Translated from Poroshkovaya Metallurgiya, No. 6(210), pp. 28–32, June, 1980.     

Growth kinetics of a surface film during the annealing of a mixture of a metal powder and a decomposing oxide

Conclusions Equations have been derived describing the growth kinetics of surface films. Conditions have been determined under which surface films cease to be porous and become coherent. Values of the coefficient of oxygen diffusion in copper at a temperature of 850°C calculated using the equations proposed and experimental data are in good agreement with a value cited in the literature.Translated from Poroshkovaya Metallurgiya, No. 2(182), pp. 22–25, February, 1978.