Conduct the temperature uniformity survey (TUS) on the furnaces each week. Be sure to remember to conduct the TUS anytime that a repair has been completed on the furnace. This includes:
- Door seal replacement
- Element repair (or replacement of a gas burner)
- Refractory repairs
- Thermocouple replacement
- Air-circulation system repairs
Remember to place the thermocouple as close to the workpiece or load without the thermocouple interfering with the loading and unloading of the load or individual component. Also, be sure that you re-place a thermocouple with the same type of thermocouple as the one that is being replaced.
It is a very simple (but necessary) occurrence that the outside temperature of the component begins to heat, with the core of the component coming up to the process component temperature.
The general rule for estimating the desired soaking time for the component is one minute per inch of maximum cross section at the desired setpoint temperature.
Vacuum furnace temperature uniformity survey (Courtesy of VVS, a Division of Thermal Innovation Technology, Inc.)
As can be seen, the subject of temperature measurement and temperature uniformity is vital to the success of the heat-treatment process for both ferrous and nonferrous metals. It is a critical item of concern for aerospace applications since we are venturing into the realm of space travel. Heat treatment and metallurgical processing demand temperature measurement and uniformity accuracy.