Controlling heat treating furnaces

A method of controlling the metallurgical properties of low emissivity coils of multiple wraps of aluminum sheet material in a batch type furnace to effect desired metallurgical properties in the wraps of the coils, said wraps forming an uneven, non-planar edge, the method comprising:

• applying a spot of heat resistant material of a constant, known emissivity that is substantially unity to the uneven edge of each coil and in a manner that does not penetrate into the wraps of the coils, and leaves inner portions of the uneven edge behind the spots uncoated with the heat resistant material,
• placing the coils within the furnace,
• heating the atmosphere within the furnace,
• aiming infrared sensors at said spots through sight tubes from locations remote from the coil edges and spots, and at an angle that views only the material of said spots to sense the temperatures thereof,
• cooling the sight tubes and a flange of each tube located within the furnace,
• using the temperatures sensed by the sensors to raise the temperature of the atmosphere within the furnace and thereby raise the coils to a temperature that will begin the process of metallurgically changing the properties of the coils, and
• thereafter continuing to use said temperature to complete the process of metallurgically changing the properties of the coils by controlling the temperature of the furnace until the masses of the coils have the desired metallurgical properties.

Apparatus for controlling the metallurgical properties of low emissivity coils of multiple wraps of aluminum material in a batch type furnace to effect desired metallurgical properties in the wraps of the coils, said wraps forming an uneven, non-planar edge surface, the apparatus comprising:

• at least one infrared sensor,
• at least one sight tube located in a wall of the furnace such that one end of the tube is located within the furnace while the other end is located outside of the furnace, said sensor being located in the tube adjacent the outside end thereof and thus remote from the coils, and disposed at an angle that permits the sensor to view only a spot of heat resistant material having a constant, known emissivity that is substantially unity located on a portion of the non-planar edge of the coil,
• a flange located adjacent the end of the sight tube located within the furnace,
• said tube and flange having hollow walls for conducting a coolant therethrough,
• means for controlling the temperature within the furnace, and
• means for electrically connecting the infrared sensor to said means for controlling furnace temperature.