Effect of silicon on the rate of de-sulphurization of liquid Fe-S alloys by argon-hydrogen at 1550°C

Abstract

The passivation of copper anodes due to precipitation of copper sulfate on the anode surface was investigated as a function of electrolyte composition and temperature, and of anode composition. The slime layer present on the anode surface was shown to be the primary factor in causing passivation by inhibiting the diffusion of copper ions. Factors such as temperature, free acid level, Ni²⁺ and Cu²⁺ ion levels were also important in so far as they affected the mass transfer characteristics of Cu²⁺ ions and the solubility of copper sulfate.

Résumé

La passivation des anodes de cuivre due à la précipitation du sulfate de cuivre sur la surface de l'anode a été étudiée en fonction de la composition et la température de l'électrolyte et aussi en fonction de la composition de l'anode. Nous avons montré que la couche d'impuretés présente sur la surface de l'anode est la cause première de la passivation car elle empêche la diffusion des ions cuivre. D'autres facteurs tels que la température, le niveau d'acide libre, le niveau d'ions Ni²⁺ et Cu² sont également importants en ce qu'ils affectent les caractéristiques de transport de matière des ions Cu²⁺ et la solubilitédu sulfate de cuivre.     

Production of thick steel sheet for high-pressure equipment operating at temperatures from 450°C to–50°C

The industrial production of low-carbon microalloyed steel plates (thickness 150–200 mm) on the NLMK Dansteel 420 reversible rolling mill is considered. Such plates are intended for operation at temperatures between–50 and +450°C in high-pressure equipment. The technologies used for steel casting and thick-sheet production ensure stable strength over the whole sheet thickness at 20–450°C, with satisfactory impact strength between +40 and–50°C. The research results are used in certification on the basis of TUV Pressure Equipment Directive (PED) DGR 2014/68/EU and the AD2000 directive regarding the production of rolled P355N, P355NH, P355NL1, and P355NL2 steel sheet of thickness up to 200 mm.     

Solubility of silver in the K–KCl melt at 850°C

The solubility of silver in K–KCl melts at 850°C is studied in varying the potassium content from 0 to 100 mol %. It is shown that the solubility linearly increases as the alkali metal content increases; the solubility of silver in potassium melt is 6.0 mol %.     

Effect of the phase composition on the properties of a complex magnesium alloy at temperatures from –70 to +300°C

The phase composition and the structural evolution of an Mg–Zn–Zr alloy containing REM are studied in comparison with the commercial MA14 alloy. It is found that the phases formed with REM exhibit high thermal stability. An equiaxial and fine-grained structure and a favorable morphology of the phases provide a high level of the properties of the new alloy with respect to the properties of the commercial MA14 alloy over the wide temperature range from –70 to +300°C.     

Effect of Melting Process on the Microstructure and Mechanical Properties of Fe–7 wt% Al Alloy

This article presents the effect of melting process on chemical composition, microstructure and mechanical properties of Fe–7 wt% Al alloy. The alloy ingot was prepared by air induction melting (AIM), air induction melting with flux cover (AIMFC) and vacuum induction melting (VIM) and cast into 50 mm diameter split cast iron mould. These cast ingots were hot-forged and hot-rolled at 1,373 K to 2 mm thick sheet. Hot-rolled alloys were characterized with respect to chemical composition, microstructure and mechanical properties. Ingots produced by AIM, AIMFC and VIM were free from gas porosity, however AIM ingots exhibited higher concentration of hydrogen as compared to AIMFC and VIM. The recovery of aluminium as well as reduction of oxygen during AIM is very poor as compared to AIMFC and VIM. AIMFC ingots exhibit low level of sulphur as compared to AIM and VIM ingots. The alloys produced by AIMFC and VIM exhibited superior tensile ductility compared to the alloys produced by AIM. The tensile properties of alloys produced by AIMFC are comparable to the alloys produced by VIM.     

Effect of Speed on the Tribological Behavior of Fe–Cu–C Based Self Lubricating Composite

In this work, the effect of different speeds on the tribological properties of sintered iron–copper–graphite (Fe–Cu–C) based self lubricating composites have been studied. Fe–Cu–C based self-lubricating composites were prepared by powder metallurgical compaction and sintering method. CaF₂, a solid lubricant in weight percentages of 0, 3, 6, 9 and 12 was added to the base matrix consisting of Fe-2Cu-0.8C. The fabricated samples were tested for friction and wear at a constant load of 10 N and three different speeds of 0.5, 5 and 10 m/s. The surface properties of unworn and worn surfaces were analyzed using optical and scanning electron microscope. The friction and wear test of the composites exhibited decrease in coefficient of friction and increase in wear loss with the increase in speed. The results also revealed different trends in the friction behavior of the developed composites at low (0.5 m/s) and high speeds(5 and 10 m/s). However, at all test speeds, COF of samples with 3, 6 and 9 wt.% was less than the base matrix, and wear loss of 3 wt.% CaF₂ sample was the lowest at all speeds. Ploughing, adhesive and delamination wear were the dominant wear mechanism as revealed by SEM. Based upon the findings, the developed material could be used for low and high speed antifriction applications.     

C-Ni and Al-C-Ni phase diagrams and thermodynamic properties of C in the alloys from 1550 °C to 2300 °C

The C-Ni and Al-C-Ni phase diagrams were determined by chemical analysis of alloys saturated with carbon within sealed graphite crucibles. The solubility of carbon in nickel over the temperature range 1550 °C to 2300 °C is given by log (at. pct C)=2.0376−1874.68/T, where T is temperature in kelvin. Isothermal sections for the ternary system were determined at intervals of 150 °C over the range of temperatures investigated. The univariant points on the 1700 °C, 1850 °C, and 2000 °C isotherms were determined by metallographic examination of rapidly cooled alloys to be about 67.2Al-1.1C-31.7Ni, 70.3Al-2.3C-27.4Ni, and 82.5Al-7.0C-10.5Ni, respectively, where all concentrations are in atomic percent. Graphite, Al₄C₃ (decomposition temperature 2156 °C), and AlNi (decomposition temperature 1638 °C) were the only solid phases observed within the temperature range investigated. The excess partial Gibbs energy for dissolved C, , in liquid Al-C-Ni solutions in equilibrium with C, as calculated from the experimental solubilities and thermodynamic data on Al-Ni, is

Section of the isothermal tetrahedron of the Al-Cu-Mg-Zr phase diagram at 490°C

The phase equilibria in the Al-Cu-Mg-Zr system at 490°C have been studied for Al-rich alloys with 0.3% Zr and from 0 to 10% Cu or Mg. The (Al) solid solution is found to be in equilibrium with only binary θ(CuAl₂) and ZrAl₃ and ternary S (CuMgAl₂) phases of the ternary Al-Cu-Mg system. The section of the isothermal tetrahedron of the Al-Cu-Mg-Zr phase diagram at 490°C, which corresponds to 0.3% Zr and up to 10% Cu or Mg, is constructed.     

Thermodynamics of Calcium Ferrite Slags at 1200 and 1300°

Abstract

Oxygen isobars and liquidus isotherms of the system CaO-FeO-Fe₂O₃ at 1200 and 1300°C were determined by quenching samples equilibrated with CO₂–CO mixtures, The iron liquidus and the melt coexisting with two solids were carefully examined in terms of their composition as well as the equilibrium oxygen partial pressures, p _o2 . At 1200°C, p _o2 was 10^?7.70 atm when the slag coexisted with magnetite and dicalcium ferrite, At 1300°C, the melt region extends to the CaO–Fe₂O₃ join, where p _o2 was 10^?0.68 atm (air) or higher. Within the range of p _o2 from one order above that at iron saturation to 10^?4 atm, the slag composition, p _o2 , and the temperature T are related by the equation:

log (Fe^{+ + +} /Fe^{+ +} ) ? 0.170logp _O2 + 0.018 (wt% CaO) + 5500/T ? 2.52.

Activities of CaO(s), FeO(l), and Fe₃O₄ (S) in the slag were calculated from the p _o2 data by combining the available thermal data and/or by Gibbs-Duhem equation.

Résumé

Les isobares d'oxygene et les isothermes du liquidus du systeme CaO–FeO–Fe₂O₃ à 1200 et 1300°C ont été déterminées en trempant des échantillons équilibrés avec des mélanges CO₂–CO. Le liquidus du fer et le mélange coexistant avec deux solides ont été soigneusement étudiés en terme de composition et de pression partielle d'oxygène à l'équilibre, p _o2 . A 1200°C, p _o2 était de 10^?7.7 atm quand la scorie était en équilibre avec la magnétite et la ferrite de dicalcium. A 1300°C, le domaine du liquide s'étend jusqu'au joint CaO–Fe₂O₃ où p _o2 valait 10^?0.68 atm (air) ou plus. A l'intérieur du domaine de p _o2 qui s'étend d'un ordre au dessus de celle à la saturation en fer jusqu'à 10^?4 atm, la composition de la scorie, p _o2 et la température T sont reliées par l'équation:

log(Fe³⁺/Fe²⁺) ? 0.170logp _o2 + 0.018(pd %CaO) + 5500/T ? 2.52.

Les activités de CaO(s), FeO(l) et Fe₃O₄(S) dans la scorie ont été calculées a partir des valeurs de p _o2 en combinant les données thermodynamiques disponibles et/ou l'équation de Gibbs-Duhem.     

Effect of P,B4C,and (Ti,Cr)C Additives on the Kinetics of High-Temperature Oxidation of Chromium Carbide Alloys at 1000°C

We have used the thermogravimetric method to study the effect of B₄C, (Ti, Cr)C, and phosphorus additives on the kinetics of oxidation of chromium carbide alloys of the type 85% Cr₃C₂ 15% Ni (KKhN15) and 85% Cr₃C₂ 15% (Ni P) (KKhNF15), in air under isothermal heating conditions at 1000°C from 0 to 5 h. We have established that the alloys are characterized by insignificant increase in mass in the initial oxidation period (3 h), after which the degree of oxidation increases somewhat. The nature of the oxidation kinetics for KKhNF15 alloys, containing 0.016-0.64% B₄C, varies from some mass increase in the initial period (20 min) to later mass loss in connection with formation of CO, CO₂ and rapid evaporation of boron anhydride B₂O₃. The maximum resistance to oxidation is exhibited by alloys of the type KKhN15 and KKhNF15, the mass increase of which is 0.128-0.256 mg/cm² after 5 h of heating at 1000°C.     

Effect of FeNiCrBSiC–MeB2 Material Composition on the Oxidation Behavior at High Temperatures

Powder Metallurgy and Metal Ceramics - The effect of TiB2 and CrB2 additives on the oxidation behavior of composites made of the NiCrBSiC and FeNiCrBSiC self-fluxing alloys has been studied in air...     

Crystallographic and morphological characteristics of oxidation growth pits in wustite grown at 1200 °C

In situ oxidation of polycrystalline iron at 1200 °C and atm has revealed symmetrical square growth pits in the wustite scale. The pit walls are nominally oriented with the {110} planes of the wustite lattice but are dissociated into macro- and microledges consisting of {100}-type planes. Such growth pits intrude into the wustite scale at the gas/oxide interface, and at the oxide/metal interface small oxide nodules intrude into the metal. After sufficiently long oxidation times at 1200 °C, rate control should shift from oxidant arrival to cation volume diffusion, and pits are then destabilized and a planar morphology is achieved.     

Acidophilic bioleaching: A Review on the Process and Effect of Organic–inorganic Reagents and Materials on its Efficiency

Bio-hydrometallurgical applications have been receiving more attention globally for processing of several metal bearing wastes. Developments in bioleaching enable this technique to be utilized as an alternative process for extraction of metals (ex-copper, gold, etc.) from complex ores or even concentrates, consequently solving several environmental issues. Organic and inorganic reagents or additives used during the process have been seen to affect the leaching efficiency of microbes for metal dissolution. The present review discusses the influence of certain organic–inorganic reagents and other materials or additives on the growth, oxidation activity, and bioleaching efficiency of acidophiles on metal dissolution.     

Interaction of sintered aluminum nitride with the KF-AlF3 melt at 700–800°C

Interaction kinetics of the aluminum nitride-based sintered composite material with the potassium cryolite melt with the cryolite ratio KO = 1.3 at 700–800°C is investigated by the continuous weighing method. It is established that the composite is almost unaffected by the melt at t = 700°C. The corrosion rate increases as the temperature increases. The material interacts with the molten salt through its oxidation stage by oxygen dissolved in the melt. This is also accompanied by the dissolution of oxygen-containing impurities that are initially present in the material. No interaction of sintered aluminum nitride with the melt under study was observed in the absence of the oxidant and with the concentration of alumina dissolved in cryolite close to saturation.