Abstract

The Electroslag Remelting (ESR) is an alternative to vacuum processes. This method is characterized by relative simplicity of equipment, flexibility of technological parameters, and high quality and low production costs of obtained metal.

Presence of chamber and controlled atmosphere creates the favorable conditions for effective refining, modification, and alloying of metals and alloys due to using of active components (calcium, rare-earth elements and other) during the remelting process. At same time, no doubt, all of this has the influence on all complexes of physical-chemical, electrical and thermal processes of remelting. Thus, the additions of metallic component (calcium in particular) in ESR slag cause the considerable changes of electric regime of remelting. In turn, it has the influence on velocity of melting of consumable electrode, power balance of process and forming of remelted ingot.

Presence in ESR slag of metallic calcium with high vapor pressure provides the series of very essential corrections of physical nature of heat evolutions during ESR. In near-electrode zone with maximal temperature, the evaporation of calcium is probable. In result of this the usual resistive regime of melting is disturbed and arc is formed. Arc discharge "blow" the calcium vapors from the near-electrode zone to the furnace atmosphere. After condensation they are forming together with vapors and droplets of slag to the "crown" on the of electrode and crucible. After that the arc regime changes to resistive regime and cycles may repeats again. Evaporated from interface surface "gas-slag" and blowed from near-electrode zone calcium later partially returns in reaction zone in result of "crown" submelting. Naturally, such cyclic changes worsen the stability of electric regime and may cause the decreasing of quality of ingot surface, its macro- and microstructure. Development of these effects is clearly connected with concentration of calcium in slag and increases with its growth. Thus, when calcium content in slag reaches the concentration more than 15% wt, process fully transforms to arc regime. Therefore taking into account necessity to reach the main goal of ESR- to obtain the high-quality ingots from metals with high reaction ability, advisably to support in slag the optimal calcium concentrations, close to limiting (equilibrium).