Dissertation is devoted to determination of regularities of processes of metal
melting, transferring and crystallization at ESR in conditions of effect of external constant
and impulse longitudinal magnetic fields and development of technical recommendations
on their application for melting of titanium alloys.
The peculiarities of melting of the consumable electrode, the nature of formation
and detachment of electrode metal droplets and their movement in the slag pool at ESR
under the conditions of external magnetic fields are investigated by mean of physical
modeling. The experiments were carried out according to different schemes using
alternating, direct and modulated melting current under the action of an external constant
or pulsed longitudinal magnetic field.
As a result of these experiments it was found that under the influence of a
longitudinal magnetic field torroidal hydrodynamic flows in the slag pool are transformed
into horizontal rotation around its axis, which leads to deformation of the free surface of
the slag pool and the interface slag-metal pools. The amount of deformation of the pool
free surface depends on the speed of its rotation.
By means of the physical modeling a number of laws was established. In particular,
use of longitudinal magnetic field induction of 0.2...0.35 Tesla leads to a decrease in the
frequency of detachment of electrode metal (by 20...30%), a decrease in their average
weight (up to 10...50%), an increase in their trajectories of movement (up to 30...160%)
and the period of passing through slag pool (from 0,2...0,25 to 0,4... 0,8 s), as well as to
the dispersal of places where they fall on the mirror of the liquid metal pool.
The main results of physical modeling were tested in the conditions of real ESR on
the modernized equipment for melting under the action of longitudinal magnetic fields. It
was experimentally established that the longitudinal magnetic field induction of 0.2 Tesla
leads to a decrease in the melting current (by up to 20%) and an increase in the amplitude
of its oscillations, without direct change in other parameters of the process. If an impulse
magnetic field is used, the reduction of the melting current has a cyclic nature, and the
value of its reduction depends on the induction and the duration of its impulses and can be
up to 70...80%.
By means of analysis of the electric modes of the ESR under the influence of an
external longitudinal magnetic field induction of 0,2...0,28 Tesla it was established that the
frequency of the electrode metal droplet detachment increases by 18...62 %, and the
electrode melting rate - by 3...6 %. At the same time, the average diameter of metal
droplets decreases by 5...16%, and their mass by 13...41%.
It was been experimentally established that the longitudinal magnetic fields at ESR
lead to essential refinement of macrostructure of titanium ingots with simultaneous
deterioration of the quality of their lateral surface. The optimum values of induction of
direct and impulse longitudinal magnetic fields, which ensure the maximum disorientation
and macrostructure refinement of ingots of diameter 70...140 mm with minimal
deterioration in the quality of their surface and the absence of internal defects. It was
found that for the direct magnetic field such induction range is B=0,12...0,22 Tesla, and
for the pulse one - B=0,18...0,3 Tesla with the duration of pulses timp=0,9...2,5 s, and
pauses - tp = 6...15 s.
The temperature dependence of electrical conductivity, viscosity and solidification
interval of salt compositions based on CaF2 was investigated. On their basis the salt, threecomponent
flux of CaF2 - SrCl2 - Na3AlF6 system for ESR of titanium was developed.
Technological recommendations on equipment, materials, regimes for ESR of ingots
of titanium alloys in longitudinal magnetic fields were developed.
The pilot ingots of titanium alloys VT-6, TS6 and OT-4 were obtained by ESR
method in the external magnetic field. It was found that the chemical composition of
alloys fully meets the requirements of current standards. The ingot metal is characterized
by high chemical and physical homogeneity. The characteristics of the strength of the test
samples correspond to the typical values for these alloys, and the characteristics of
ductility and impact elasticity exceed on average by 10...25%.
