S-CONTAINING HIGH-STRENGTH ULTRAFINE-GRAINED STEEL AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide steel having fine-grained ferrite and having high strength and excellent toughness and machinability. SOLUTION: Steel which has a structure composed of ferrite of≤10μm average grain size and at least one or more kinds among austenite, pearlite, cementite and martensite and contains 0.01 to 0.3% S (sulfur) is subjected to working of≥0.7 strain at a working temperature ranging from 550°C to (Ae1 point+50°C). COPYRIGHT: (C)2005,JPO&NCIPI