Hardened and tempered spring steel for rolling shutter

SPECIFICATION

Carbon : 0.75 - 0.85 %
Manganese : 0.60 - 0.90 %
Silicon : 0.35% Max
Sulphur : 0.04% Max
Phosphorus : 0.4% Max
Hardness : 45-48 HRC
Tensile Strength : 145-160 kg/mm2