Patent ID: 6200395
Filing Date: 2001-03-13
Classification: C21D,C22C

Abstract:
A free-machining steel composition consisting essentially of, in weight percent, carbon up to about 0.25, copper up to about 0.5, manganese from about 0.01 to about 2, oxygen from about 0.003 to about 0.03, sulfur from about 0.002 to about 0.8, MEA, and a balance of iron and incidental impurities, wherein the MEA is selected from the group consisting of tin from about 0.04 to about 0.08, arsenic from 0.03 to about 0.13, antimony from about 0.015 to about 0.055, and combinations thereof, and wherein a ratio of the manganese to the sulfur is from about 2.9 to about 3.4, and wherein a total of the sulfur plus the MEA plus the copper is no more than about 0.9 weight percent, the composition being characterized by a microstructure having a concentration of the MEA at ferrite grain boundaries in an amount of at least about ten times the bulk MEA content of the steel.