Peculiarities of application of natural and man-caused materials for steel alloying and modifying

Considerable reserves of improvement of steel quality and reduction of costs of its production are concealed in a possibility of active and purposeful formation their structure and the properties by introduction into the melt modifiers, alloying and microalloying additives. Due to the task of decreasing costs, studies on alloying and modifying of metal by natural and man-caused materials are very actual. Thermodynamic regularities of steel alloying and modifying processes by natural and man-caused materials, including manganese ores of various structures, BOF vanadium slag, barium- strontium modifier, obtained from the complex ores containing barium and strontium considered. Possibilities of wide application of various structure manganese ores for steel alloying by manganese without use of standard manganese alloys as well as vanadium slag for microalloying by vanadium demonstrated. Metallurgical properties barium-strontium natural modifier obtained and the possible mechanism of the modifying impact of barium and strontium on quality of metal studied. It was determined, that the effect of modifying by barium can revealed in steels, deoxidized only by silicon, and for modifying by strontium or joint modifying by barium and strontium it is necessary to apply aluminum as deoxidizing agent. Industrial testing of the above-stated materials showed reliability of studies, accomplished at thermodynamic modeling and laboratory studies of calculations and conclusions. Recommendations on optimization of technologies of steel alloying and modifying made. It was proved that use of the materials of the study allows to improve technical and economic indices of the process of production of steels and to increase considerably quality of final steel products. Conclusions on significant expansion of natural and man-caused materials prospects worded.

Direct oxygen removal technique for recycling titanium using molten MgCl2salt

Deoxidation of Ti, or direct removal of O dissolved in metallic Ti, is known to be extremely difficult when Mg is used as the deoxidizing agent. This difficulty arises because the chemical potential of O2,pO2, under Mg/MgO equilibrium is high (approximately 10−41atm at 1200 K) and is equivalent to that of Ti containing ∼2 mass% O at 1200 K. Therefore, when deoxidizing Ti to the commercial level of high-grade pure Ti (below 0.05 mass% O) using an Mg reductant at 1200 K, the activity of the reaction product MgO (aMgO) must be decreased to below ∼0.025, which is difficult in practice. In this study, the removal of O in Ti in molten MgCl2salt using an electrochemical technique was examined at ∼1173 K with the objective of obtaining Ti containing less than 0.05 mass% O. Ti samples and graphite electrodes immersed in molten MgCl2served as the cathode and anode, respectively. A constant voltage was applied between the electrodes using an external DC source. Molten MgCl2was employed to produce the deoxidizing agent Mg and to facilitate deoxidation of Ti by decreasing the activity of the reaction product MgO. By applying a voltage of approximately 3.1 V between the electrodes, the chemical potential of Mg in the molten MgCl2was increased at the surface of the Ti cathode, and the Ti samples were deoxidized. The resulting O species, mainly formed O2−dissolved in the molten MgCl2, was removed from the molten salt by reacting with the C anode to form CO (or CO2) gas. Ti wires containing 0.12 mass% O were deoxidized to less than 0.02 mass% O. In some cases, the O concentration in the Ti samples was reduced to the level of 0.01 mass%, which cannot be accomplished using the conventional Kroll process. The possible application of this deoxidation technique to practical industrial recycling processes is discussed.