PRODUCTION OF HOT ROLLED CARBON STEEL WIRE ROD HAVING HIGH STRENGTH AND HIGH DUCTILITY

PURPOSE:To improve strength and ductility by conveying, in an unconcentrical ring state, a hot rolled carbon steel wire rod finished at specific high temp., holding it at high temp., and subjecting it to cooling down to specific temp. by means of air-water mist spray and then to controlled cooling by means of warm water. CONSTITUTION:A hot rolled carbon steel wire rod 1 rolled at 980-1100 deg.C by a finish rolling mill 2 is coiled by a coiler 3 at the same temp. This wire rod 1 is moved onto a roller conveyer 4 and held at high temp. for 3-15sec via a heat holding cover 5 while being conveyed in an unconcentrical ring state, by which crystalline grains are grown. Subsequently, the wire rod 1 is passed through an air-water mist spray 6 and cooled down to 850-750 deg.C in 5-17sec. At this time, it is preferable to regulate an air-water mist 10 so that the wire rod 1 can be conveyed while controlling the temp. difference between the central part of the coil and both ends to a value in the range of 0 to 40 deg.C. Subsequently, the wire rod 1 is passed through a warm water tank 12 and subjected to controlled cooling by means of warm water 11 in the range between 80 deg.C and boiled state, by which pearlite transformation is done over the whole length. By this method, the hot rolled carbon steel wire rod having high strength and high ductility can be obtained.