When the round steel heated to 1200 degrees passes through the conveyor belt, which brand and model of photoelectric switch should be used to detect it?

One is to use an infrared photodiode, like the receiving diode of a TV remote control. In addition, pyroelectric sensors can also be used, which are not sensitive to fixed temperatures and are extremely sensitive to dynamic infrared-emitting objects. The above two are very important for on-site debugging. You can adjust them once and leave them alone for several years.