... fillers, mould inserts, dies and gauges for PVC extrusions, screws and barrels for extruders, moulds for automotive, food, medical and optical industry ... for 3 hours;Furnace cooling.Stress relieving: To be carried out after machining and before the final heat treatment,-Heating ... to600-650°C , for 2 hours ;Hardening ;-preheating to 600-700° ...