Since the early development of the vacuum furnace, engineers and thermal experts have continually tried to improve the insulating characteristics of the furnace hot zone. Several materials have been used for different applications with varying success. However, all designs must still deal with the heat losses penetrating through the insulation materials and the need to minimize these losses. This is especially important today with the continual escalation of electrical power cost.
This paper will review the different types of hot zone insulation materials used, the projected losses of the different designs, the impact relating to furnace cycle heating rates and cycle times, and the projected cost advantages of one design over another.