Annealing Incoloy Tubing
Research Objective
To anneal a continuous feed of incoloy stainless steel tubing at 2000°F in a protective atmosphere with a quick cool-down, to eliminate need for additional sandblasting operation.
Parts & Materials Description
Incoloy 840 stainless steel tubing, .310” diameter
Temperature Required
2000°F
Induction Heating Equipment
20 kW RF power supply, 11-turn helical induction coil with .8” O.D.
Operating Frequency
253 kHz
Heating Procedure
A specially-designed 11-turn helical induction coil was utilized to provide even heat to the stainless steel tubing. After initial tests were conducted to establish time-to-temperature and heating profiles, a length of tubing was placed on a PacSci carriage in a protective atmosphere of nitrogen. The carriage conveyed the tubing through the induction coil at a rate of 1.4 inches per second. The 20kW power supply and carriage were activated simultaneously. Optical sensors monitored the temperature of the steel tubing as it passed through the coil, and at 100 inches away from the coil. The power supply was turned off as the trailing end of the tube entered the coil.
Conclusion
Consistent, repeatable results were achieved with the 20kW power supply and a feed rate of 1.4 inches per second. The temperature of the steel tube reached 2000°F as it left the coil and cooled to 950° at a distance of 100 inches from the coil. Two or three water-cooled rollers could be utilized to reduce the cooling time as needed.
