There are two types of current national and industrial recommended standards for carbon spring steel wire
1. Cold drawn spring steel wire
One is cold deformation strengthening steel wire, also known as cold drawn spring steel wire.
The cold drawn carbon spring steel wire is first quenched with lead to obtain sorbite structure, and then the surface is phosphated. The steel wire is drawn to the finished product size with a large reduction rate. The steel wire structure is fibrous, with high tensile strength and elastic limit, and good bending and torsion properties. Cold drawn spring steel wire has high dimensional accuracy, smooth surface, no oxidation and decarburization defects, stable fatigue life, and is the most widely used spring steel wire.
2. Oil quenched tempered steel wire
Another type of carbon spring steel wire is martensitic strengthening steel wire, also known as oil quenching and tempering steel wire.
Carbon steel wire can obtain good comprehensive mechanical properties by quenching and tempering. When the steel wire specification is small (φ ≤ 2.0 mm), the strength indexes of oil quenched and tempered steel wire are lower than those of cold drawn steel wire after sorbite treatment. When the size of steel wire is large (φ ≥ 6.0 mm), sorbitic steel wire can not obtain the required strength index by using large reduction ratio. However, oil quenched and tempered steel wire can obtain higher performance than cold drawn steel wire as long as it is fully quenched.
Under the same tensile strength, martensite reinforced steel wire has higher elastic limit than cold deformation strengthened steel wire. The microstructure of cold drawn steel wire is fibrous with obvious anisotropy. The microstructure of oil quenched and tempered steel wire is homogeneous tempered martensite, which is almost isotropic.
At the same time, the relaxation resistance of oil quenched and tempered steel wire is better than that of cold drawn steel wire, and the service temperature (150-190 ℃) is also higher than that of cold drawn steel wire (≤ 120 ℃). In recent years, medium and large size oil quenched and tempered steel wire will replace cold drawn steel wire.