Cooling of long prods, esp. steel rods for reinforcing concrete - which are briefly water quenched on leaving hot rolling mill to increase their mechanical strength

摘要

The moving bars or rods are briefly quenched (I), and are then cooled (II) in free air, so all the cross-section undergoes a transformation at 575-630 deg.C. Quenching (I) pref. involves a high heat removal of 83-105 MJ/sq.m/hour/deg.K., obtd. by feeding the bar through two tubes sepd. by a water injector; in the first tube, the water flows in counter-current to the bar, but co-current in the second tube. The prod. is esp. low-alloy steel rod, 8-40mm. dia., contg. 0.08-0.12% C, and 0.5-1.0% Mn. The treatment used by the invention increases the Vickers hardness(HV), elastic limit(EL) and tensile strength(UTS) of the rods.