L&L Special Furnace Co. Inc. received an order for two atmosphere-controlled retort box furnaces. They will be used for debindering ceramic composite matrix (CMC) parts, powder-metal processing and hot isostatic processing (HIP). The main function of the furnaces is to remove all organics and other materials used in the product prior to placing in a high-fire vacuum chamber. The debindering process is extremely important and allows for a finished product that is very strong and light. The furnaces have a work zone measuring 23 inches wide x 23 inches high x 36 inches deep. They have a single zone of control with a temperature gradient of ±20°F at 1100°F (595°C) using four zones of temperature control with biasing to balance any temperature gradients.
The parts are heated to 1220°F (660°C) in a retort chamber that is pressurized with nitrogen. The byproducts of the outgassing part are directed by pressure and flow out the rear of the furnace. The parts are then heated in a vacuum furnace to temperatures in excess of 2300°F (1260°C). The result is a component that is stronger and lighter than titanium.
The furnaces are constructed of low-mass insulating firebrick, which allows for quicker cool-down times. They are controlled by a Eurotherm program control with over-temperature protection. There is also a programmable flow panel to control the nitrogen flow throughout the process.