STEEL WIRE FOR SPRING HAVING EXCELLENT LOW TEMPERATURE FATIGUE STRENGTH AND METHOD OF MANUFACTURING THE SAME

摘要

The present invention relates to steel wire for a spring having excellent low-temperature fatigue strength and a manufacturing method thereof. An embodiment of the present invention provides steel wire for a spring having excellent low-temperature fatigue strength, containing, by weight percentages: 0.40-0.70% of carbon (C); 1.0-2.5% of silicon (Si); 11-25% of manganese (Mn); 0.3-1.0% of chrome (Cr); 1.0-2.0% of aluminum (Al); 0.020 or less percent of phosphorous (P); 0.020 or less percent of sulfur (S); and remnant Fe and other inevitable impurities. The C, Mn, Si, and Al satisfy the relational equation of 19 C x Mn x Si x Al 25, where C, Mn, Si and Al, respectively, refer to a value showing the content of each element by weight percentage. The microstructure of the present invention includes austenite with 95 or more area percentage, and primary and secondary variant twins are formed in the austenite crystalline grains.