PRODUCTION OF SOFTENED MEDIUM CARBON STEEL WIRE ROD OR LOW-ALLOY HIGH-TOUGHNESS STEEL WIRE ROD

摘要

PURPOSE:To eliminate the need for softening annealing of a secondary operation stage by cooling a wire rod down to a specific temp. range after the end of hot rolling, then coiling the wire, allowing the coil to cool down to a specific temp., enclosing the coil with a heat insulating cover and subjecting the coil to slow cooling down to a specific temp. CONSTITUTION:The wire rod is cooled down to 750-900 deg.C after the end of the hot rolling and is immediately coiled and the coil is allowed to cool until the temp. in the outside circumferential part of the coil attains 525-700 deg.C at the time of producing the wire rod by hot rolling a billet of a medium carbon steel or low-alloy steel. The entire part of the coil is then enclosed wit the heat insulating cover to heat up the outside circumference of the coil by recuperation. The coil is held as it is in the slow cooling state until the temp. on the outside circumference of the coil falls down to 600 deg.C. The time before the end of the treatment is prolonged and the thickness of scale increases if the temp. exceeds 900 deg.C. On the other hand, the coiling is difficult and the generation of martensite tends to arise if the temp. is below 750 deg.C. The effect of shortening the slow cooling time is low if the outside circumferential temp. of the coil when allowed to cool exceeds 700 deg.C. The above-mentioned if said temp. is below 525 deg.C. The softening is not attainable if the cooling temp. in the cover is =600 deg.C.