On the use of phosphor thermometry for temperature monitoring in manufacturing processes

In the metalworking industry, continuous monitoring and control of temperature is vital to enhance process efficiency, reduce wastage, and attain product reliability in high-value manufacturing processes. The capabilities of conventional techniques such as the use of thermocouples and infrared thermometry for measuring temperature in these processes are limited. For example, in forging processes, there may be a need for mechanical alteration of the die to accommodate thermocouples for die surface temperature measurements, and with infrared thermometry, knowledge of the emissivity of the surfaces of process components is required for accurate temperature measurements. Given that phosphor thermometry has not previously been used in manufacturing processes, here, we report its potential implementation using the phosphor Mg4FGeO6:Mn for measurements of die surface temperature in a forging press. First, with this phosphor, laboratory trials were conducted to describe the cyclic heating of a die by pre-heated billets, which is a process leading to thermal fatigue that requires monitoring in practical applications. Then, the phosphor thermometry technique was demonstrated for die temperature measurements on a 2100 tonne screw press at the Advanced Forming and Research Centre (AFRC). The results show that phosphor thermometry is a candidate technique that would potentially enable more accurate measurements not possible by other techniques in this manufacturing process.