Heat treatment characteristics of the typical spring

Depending on the size of the spring forming and heat treatment methods are also different. Cold forming spring diameter smaller or thinner thickness spring shall generally be cold drawn spring wire or cold-rolled steel spring. Wire available 60, 70, 65 mn, T7A, T8A and T9A steel. According to GB/T4357 - 1989, carbon spring steel wire is divided into three groups of B, C, D. Group B tensile strength in 1080 ~ 2800 mpa, used for general low stress spring and other USES; The tensile strength of group C in 1270 ~ 3140 MPa, used for medium stress spring; Group D tensile strength in 1520 ~ 3240 MPa, used in high stress on the spring. In the same group, the wire diameter is small, the higher the strength. Cold forming spring wire according to the different manufacturing process can be divided into three categories. 1) lead bath isothermal deal with the production process of cold drawn steel wire main characteristic is that the steel wire in the process of cold drawn after certain rapid isothermal cooling process, and then cold pulling into the required size. T8A steel, for example, first the normalized steel pickling, after three times of cold drawing, the total drawing amount was 50%, and then wire to 3. The speed of 5 m/min through the heating furnace, heating to 890 ~ 920 ℃ austenitizing temperature, lead bath in 500 ~ 550 ℃ isothermal decomposition into sorbite in the organization, and then via multiple drawing to diameter you need. This kind of steel wire is 60, 70, 65 mn mainly brand, the highest strength can reach more than 3000 MPa, and high plasticity. With such wire cold coil spring, only need to get rid of stress under the 200 ~ 300 ℃ tempering, to eliminate stress and the spring setting. Motorcycle suspension spring phi. 6. 0 x phi 35 x 280, material is lead bath quenching tempering 55 sicra wire winding, by 250 ℃ x 2 h after forming low temperature annealing, using the strength of 1680 mpa, is about 46 - hardness 48HRC。 (2) this kind of oil quenching tempering steel wire steel wire is refers to the size of the cold drawn to the provisions of, after oil quenching and tempering. The tensile strength of steel wire as lead bath isothermal treatment cold-drawn steel wire, but its performance is more uniform, smaller range of strength, widely used in the manufacture of all kinds of mechanical power valve spring. This kind of steel after cold rolled into spring, also just for eliminating stress tempering, need not be obtained with quenching tempering. Such as vehicles of plunger spring, feed on the needle valve spring, etc. , material 65 mn steel. After oil quenching tempering treatment of steel wire, diameter of 0. 8 to 1. 5 mm, both in cold lap can produce cold work hardening, high strength, must be to eliminate stress tempering, is 200 ~ 250 ℃ for 1 h. For the 70 steel torsion spring and tension spring, need to be the end of the rolling processing, so also the second tempering. The first 200 ~ 250 ℃ by 1 h; The second tempering temperature 180 ~ 200 ℃ by 1 h air cooling. Must be properly to stress tempering temperature. Temperature is too low, not fully eliminate stress; Temperature is too high, due to the softening action of tempering, lower the tensile strength and elastic limit. Table 1 for several kinds of steel wire after cold coil spring to stress tempering temperature range, time, generally is 30 ~ 60 min, time is too long also cannot make performance improvements. (3) annealing state supply alloy spring steel wire made of the steel wire springs need quenching tempering treatment, can achieve the required mechanical performance. This kind of steel wire has 50 crva wire, 55 simnb 60 si2mn steel wire and steel wire, etc. Hot forming spring spring wire diameter or spring steel plate thickness