In the cooling of a steel railway car wheel having relatively thick hub and tread portions and a relatively thin plate portion, it is important that undue stresses are not set up in the plate portion and, simultaneously, that the tread is hardened for good wear qualities while the hub is kept soft for easy machinability. These objectives are achieved by providing a conveyor having suspended thereover, at spaced intervals, non-metallic insulating disks having a diameter approximately equal to or slightly larger than the wheel hub diameter, moving the wheels in intermittent steps along the conveyor so that the wheels stop for a predetermined period of time directly under successive disks until the hubs have cooled from a temperature of about 1,700* F. to below the critical transformation temperature which is about 1,200* F., the other portions of the wheels having cooled at a faster rate.