HIGH STRENGTH AND TOUGHNESS SPRING STEEL WIRE HAVING EXCELLENT FATIGUE LIFE, SPRING FOR THE SAME AND METHOD FOR MANUFACTURING THEREOF

摘要

PURPOSE: A high-strength and high-toughness spring steel wire, a spring using the same and a manufacturing method thereof are provided to prevent the early fracture due to crystal grain coarsening according to boron addition. CONSTITUTION: A steel sheet is drawn to be a steel wire. The steel wire is heated to the temperature of 850-1000 degrees Celsius. The heated state maintains over one minute. The steel wire is formed in austenite. The steel wire formed into austenite is oil-cooled. The oil-cooled steel wire is tempered. The step that the steel wire is formed in austenite is performed to make the mean size of austenite crystal grains less than 15 micrometer.