The Innovations in the Superalloys Metallurgy
Abstract
Review of modern technologies and furnaces for vacuum induction melting (VIM), vacuum arc remelting (VAR) and electroslag remelting (ESR) is presented. The world special metallurgy development ways are shown. The first direction is a development of technologies of melting and remelting, furnaces, and control systems for: ensuring of high metal quality, yield increasing, and decreasing of costs. The second direction is creation of new inexpensive technologies of special steel and alloys for “not flying” units with the aim to significantly reduce production expenses, at enough level quality maintenance. Advantages of the new generation furnaces, including VIM, VAR, and ESR in controlled atmosphere are shown.
I. Advantages of innovative vacuum induction furnaces.
The lower volume of vacuum chamber permits to: increase an effectiveness of vacuum pump system; decrease amount of deleterious impurities vapor above the melt; decrease pumpdown time; decrease argon consumption.
The long tundish allows arranging dams and ceramic filters for rough and fine metal cleaning from slag and non-metallic phases.
The three phase inductor permits to increase a degassing effectiveness and a controllability of the process (as a melt heat is independent from stirring and vice versa).
II. VAR: control systems advancement is the main direction of investigations.
Imperfections of current VAR controllers: lack of opportunity of smooth control of melt rate (because of nonlinear character of function of melt rate vs current value); the controller response delay on shot periods of arc disturbances (glow conditions) which leads to defects in ingots. But the last shortcoming is true except Lasmet VAR controller. Its advantage is reall stabilization of mass melt rate in shot periods of high arc disturbances (glow conditions).
III. ESR – remelting under controlled atmosphere is the mainstream.
Variants of protective gases: dry air, argon, nitrogen.
Advantages in comparison with ordinary ESR: 1) lower levels in ingots: hydrogen, after remelt under dry air, or nitrogen; hydrogen and nitrogen, after remelt under argon; 2) Al, Ti, Si losses decrease, under argon; the possibility of ESR of Al and Ti alloyed steels and alloys.
Russian metallurgical science potentials for modernization of technologies and control systems are also presented.
References:
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