Adopting the heating modes of externally heating. the vacuum pit type annealing furnaces have heating elements, fire-resistant and heat preserving materials set inside their firepot. the workpiece are placed in the vacuum fire boxes, undergo the heat treatment process of bright quchening after the fire box being pumped to vacuum degreeand being set to coresponding temperature.

Using additional device, it's also possible to realize gas blackening & bluing, stress annealing, caobonization,jointcarbonization and nitrogenization & other heat treatment processes..