PURPOSE: To manufacture a wire rod having a cementite spheroidal structure, which is excellent in its cold forgeability, by adjusting a working heat treatment condition of a hot rolling process of the wire rod, and its following cooling condition.
CONSTITUTION: In a hot rolling process of a wire rod, roll working whose reduction of area is ≥20% by cumulative screw-down, and whose rolling speed is ≥0.25m/sec is executed, within a range in which a wire rod temperature is ≥A1 transformation point -30°C and ≤A3 transformation point -20°C, and subsequently, a wire rod having a spheroidal structure is obtained by cooling it at a cooling speed being ≤2.0°C/sec, extending from a working temperature to 640°C. Also, the wire rod is subjected to rolling or wire drawing under the same working heat treatment conditions as above, and is cooled by the same conditions as above, by which a wire rod having a spheroidal structure is obtained. In said treatment process, when the working heat treatment conditions are limited within said range, it is attained to finely disperse the spheroidal structure nucleus, and flocculation and spheroidization of cementite are quickened by the following slow cooling.
SATOU HIROSHI
MURAKAMI MASAAKI
NINOMIYA TAKASHI
| JPS583919A | 1983-01-10 |