rolling door spring steel strip is also called hardened and tempered steel strip,which is made of a unique process through controlling heating and cooling with the furnace.it can be used to increase the toughness of the steel strip,what is more, this process can make the properties of these hardened and tempered steel strip are high strength,and hardness and good toughness and abrasion resistance at the same time.therefore,it is better used in various application field,such as rolling shutter spring,rolling door springs,band springs,flat springs.