Accurate, Responsive Melt Rate Control During Vacuum Arc. Remelting

摘要

Vacuum arc remelting (VAR) is an industrial metallurgical process widely used throughout the specialty metals industry to cast large alloy ingots. Part of the VAR control problem consists of adjusting arc current to control electrode melt rate, which also depends on the electrode temperature distribution. Because the temperature distribution responds very slowly (1-4 hours depending on size and material) to changes in melt power, the melt rate response is history dependent and highly nonlinear. The situation is complicated farther because measurement of the electrode temperature distribution is not practical. To solve the problem of accurate, responsive melt rate control, a low order, electrode melting model has been developed and incorporated into a VAR process controller. Data from laboratory and industrial tests show that the goal of responsive, accurate melt rate control has been achieved, even when melting under highly dynamic process conditions.