Myshegian V. Theory and practice of electron-beam melting and processing of molybdenum concentrate ingots into semi-finished products

Musheghyan V.O. Theory and practice of electron-beam melting and processing of molybdenum concentrate ingots into semi-finished products - Manuscript. Thesis for the doctor of technical sciences degree by specialty 05.16.02 "Ferrous and non-ferrous metals and special alloys." STC E.O. Paton Welding Institute of the NAS of Ukraine, 2013. Thesis deals with the important scientific and technical problem of obtaining high-quality ingots and semi-finished products of molybdenum concentrate of primary processing due to refining and influence on the solidification of ingots in electron-beam furnaces. The technology of electron beam melting of ingots of alloys based on molybdenum was developed. Melting was performed in electron-beam unit MV-1, specially designed for refractory metals and their alloys. Low and medium alloyed molybdenum ingots were obtained with traditional EBCH and using peripheral heating mold. The influence of the modes on the structure of the ingots, the brittleness threshold temperature and mechanical properties of the metal were studied. A series of numerical experiments to determine the optimum conditions of molybdenum smelting ingots were carried out. Through (complex) pipe technology from EBCH molybdenum ingots was developed that reduces the cost of production, including through the full implementation by enterprises of Ukraine. Through technology of molybdenum rods production from pressed powder briquettes of low recycling was developed. The technology includes electron-beam melting with cold hearth as well as stepped rolling mill. Obtained ingots with a diameter of 70 ... 100 mm had been adapted to the rolling diameter of 18 mm. The chemical composition, structure and properties of the molybdenum rods were explored. A high level of mechanical properties of a material rod was achieved: tensile strength 700 MPa, elongation - more than 20%. It is shown that the quality of the bars corresponds to the requirements of the standards for hot-rolled bars and molybdenum grades MЧ and МЧВП. Keywords: molybdenum, electron beam melting, peripheral heating, cold brittleness threshold, ingot, grain size, refining, rolling.