L&L Special Furnace Co. Inc. manufactured and supplied a high-uniformity box furnace, which will be used for hydrogen annealing, for an industry leader that manufactures aerospace and medical supplies for a worldwide client base. The primary purpose of the furnace is to evenly heat to an internal stabilized temperature of 1750°F. The furnace is held at this temperature for a predetermined amount of time and is then cooled using an external Venturi cooling system. The furnace control system is driven by a Honeywell HC900 control system with touch screen. This computer-based control system includes a CPU and operator interface with Ethernet capabilities.
The furnace is first loaded with product in a work envelope of 17 inches wide x 17 inches high x 25 inches deep. It is purged with 10 volume changes of nitrogen or until the oxygen level is below 1% and is then capable of introducing hydrogen up to 100%. The dew point of the hydrogen entering the furnace is -40°F or better due to the use of all-stainless-steel lines. The furnace is divided into six zones, each with independent PID loops. The thermocouples are type K, allowing for consistent operation at 1750°F.