1. Strain spring tempering solution
The strain spring tempering solution refers to applying a tensile stress equivalent to 20% to 40% of the tensile strength at both ends of the tempered steel wire. The steel wire causes a small amount of strain under the tension effect, and the dislocation line moves. At this time, the interstitial solute atoms ( C and N atoms) diffuse to the vicinity of the dislocation line by means of temperature, "pinning" the moving dislocation. The carbides dispersed and precipitated during the whole tempering process showed a large number of pinning points, which made the dislocation "pinning" more thorough and sufficient, improved the plastic deformation resistance of the steel wire, and improved the elastic reduction characteristics of the steel wire.
2. Induction spring heating solution
The induction spring has a fast heating speed, the surface of the steel wire is lightly oxidized, it is not easy to cause decarburization, and the grains are also refined. The strength and toughness and elastic reduction characteristics are very good, and the weight can be reduced by 10% to 20% under the condition that the various indicators of the spring are maintained at the original level. For spring steels containing vanadium and niobium, only a higher austenitizing temperature can be used to fully dissolve vanadium and niobium, and the actual effect of tempering secondary hardening can be obtained. Under the usual heating standard, the austenitizing temperature is too high, the grains of the steel wire are coarsened, and the surface oxidation and decarburization are also sharply increased, which seriously affects the fatigue life. When induction heating to 800 ~ 1000 ℃, the steel wire is not prone to decarburization, severe oxidation and grain coarsening. Therefore, induction heating can give full play to the advantages of spring steel containing vanadium and niobium.
