Study On Defects And Influencing Factors Of Large-sized Flat Titanium Ingot Melted By Electron Beam Cold Hearth Furnace

The capacity of Electron Beam Cold Hearth Furnace at reducing high-density inclusions, solving the segregation and inhomogeneity of organization far exceed three times vacuum consumable arc melting, has become advanced technology of high-quality titanium ingot, get wide range of applications in the titanium industry. Because of the Electron Beam Cold Hearth Furnace infancy, not yet fully grasp the core technology of cooling bed furnace melting large-sized titanium ingot, some defects exist in ingot and its influencing factors have not been studied. Therefore, this paper use large-scale electron beam cold hearth melting furnace introduced from foreign in Yunnan Titanium companies to melt large-sized flat titanium ingot (8000mm×1050mm×210mm) for the study, by the melting of different process parameters on the flat ingot macroscopic defects and influence of segregation, and to explore its flat ingot defect formation mechanism, and its subsequent impact study the microstructure and properties of hot rolled coil, and obtain the following results:Titanium flat ingot melted by electron beam cooling bed furnace has major macroscopic defects,crack, pinhole, inclusions, cold shuts, and condensing hanging folds, of which crack, pinhole more difficult to remove, for affect the quality of most flat ingot significant. Scanning frequency is responsible for scanning the electron gun crystallizer smaller, the more the melt an area accepts the electron beam energy, resulting in crystallization of the melt surface is greater the temperature difference, crack tendency to increase in the melt crystallization process, flat ingot more prone to cracking. Improved flat ingot pulling ingot melting speed, so that the solidification speed, resulting in liquid titanium impurity gas generated too late to escape while remaining in the flat ingot to form pores, the greater the speed of pulling the ingot, the more the generation of pinhole. In this experiment, the electron gun scanning frequency of 11 Hz, ingot pulling speed 16.8mm/min for flat ingot surface quality obtained best.The elements segregation in flat titanium ingot relate to scanning electron gun power-, responsible for scanning electron gun crystallizer assigned crystallizer melt surface scanning power than the irrational, the surface temperature of the melt will cause uneven and local overheating, resulting in with the increase of the average temperature difference between the melt surface, flat ingot Fe, lower O content and segregation, the more serious the transverse direction. When the electron gun to melt the mold surface scan power distribution ratio of 32%,28%,40%, the average temperature difference between the minimum melt surface, flat titanium ingot Fe, O elements minimum degree of segregation.Macroscopic defects of Flat ingot lead to flash, scarring and pits and other defects in its subsequent HRC; and segregation affect the balance of mechanical properties in hot rolled coil. This paper is the in-depth study of the our country in terms of the electron beam cooling bed furnace melting large-sized flat ingot, the above findings to formulate reasonable smelting process parameters on the flat ingot defects awareness and control, and electron beam cooling bed furnace production of titanium and titanium alloys Research has guiding significance for the future electron beam cold hearth melting technology also has reference value.