Abstract : It is known that the weld metal mechanical properties of quenched and tempered steels are dependent upon cooling rate, which is presently indirectly controlled by specification of heat input. A method to directly control weld metal cooling rate would result in more consistency in achieving required mechanical properties. In the present investigation the use of commercial infrared sensing equipment was explored as a means of real-time monitoring of weld metal cooling rate. Infrared equipment has a distinct advantage over other temperature detecting systems in that it requires no physical contact with the work, thus affording a minimum amount of interference with the welding process, and is therefore a potentially useful detector for an adaptive feedback welding control system based on cooling rate. It was found that infrared thermography appears to offer considerable promise for welding control by providing weld metal cooling rates which are: (1) reproducible, (2) sensitive to variations in welding conditions, and (3) relatable to cooling rates as measured by plunged thermocouples. (Author)