Double torsion springs are generally made of cold-rolled steel or forged blanks, which can meet the fatigue life requirements of strict load and load loss under static load. impact load or dynamic cyclic load. According to the specifications and materials of different bolt pre-tightening force. as the bolt pre-tightening force compensation, the high-temperature spring in the effective working area. the relationship between pressure and stroke is linear, and the compensation force will increase as the bolt pre-tightening force increases, Achieve the effect of preloading. The following are some requirements for the manufacture of double torsion springs: 1. High temperature springs should be treated with high pressure； The treatment method can be loaded at a pressure level once. can be maintained for more than 12 hours, or maintained for a short period of time, and the pressure level is not less than 5 times. The pressure is not less than 2 times Pf = 0.75 h. The treated double torsion spring free height HO should meet the required size and keep the condition stable. According to the test, during the pulverization process, the high temperature spring cone height h will be reduced by more than 20%, so the design of the punching die must be expanded according to h Specific needs.