The dissertation is devoted to the study of thermophysical and metallurgical laws during the intensification of the technology of plasma-induction growing of large profiled tungsten single crystals, the establishment of the influence of the main technological parameters and modes of the plasma-induction process on their structure formation, as well as the development of a pilot-industrial technology with high productivity and economic efficiency of production single crystals.
It was been established that under conditions of increased intensification of the process, while providing the power of induction heating at the level of the basic technology, an increase in the dynamic effect of the plasma arc on the thermal field of the single crystal is observed. A decrease in the temperature gradient directly in the near zone of the liquid-crystal phase transition boundary was achieved by increasing the temperature in the upper region of the ingot by increasing the heat input from the induction heating source.
It was established by means of mathematical modeling that, at the level of heating of the induction energy source, at which the temperature of the build-up plane is 2273, 2773, 3273 K,, it is possible to obtain an increase in the intensification of the process by 3, 8 and 18 times at the speeds of the plasma energy source 60, 160, 360 mm/min, respectively, with the provision of the characteristics of the thermal field close to the basic level, and allows you to obtain a reduction in electricity consumption, which is 50%, 56% and 64%, or 80, 94 and 104 kW×h/kg in comparison with the basic technology.
In the study of the structural perfection of the obtained large profiled tungsten single crystals, it was found that with an increase in the intensification of the process in the range from 17 to 70 mm / min, subgrains are refined with a uniform (gradientless) distribution of the density of the dislocation pattern. It is shown that at the corresponding velocities of the plasma heating source, the ingot is a single-crystal body, the crystallographic orientation of which corresponds to the orientation of the seed crystal, with the provision of misorientation of low-angle boundaries, which do not exceed 2 deg and lie within the permissible values for metal single crystals.
On the basis of the studies carried out, a technology has been developed for growing large profiled single crystals of tungsten in the form of plates in the process of plasma induction zone melting, which provides high performance and economic efficiency with the provision of a monocrystalline structure of tungsten ingots.
