The AISI (American Iron and Steel Institute) and SAE (Society of Automotive Engineers) have an assignment system that uses a four- or five-digit number to identify steel alloys. The first two digits refer to the major alloying elements present. The last two or three digits refer to the .
a. percent of iron present in the material
b. forming temperature of the material
c. density of the material
d. percent of carbon present in the material