Standard and application of spring steel wire

Table 6 GJB 1497-92 specification for special purpose carbon spring steel wire
Note: ① the tensile strength difference between the two ends of each coil of steel wire shall not be greater than 100MPa.
② When the steel wire is twisted, there shall be no visible crack and delamination within the specified torsion times.
③ The steel wire shall not be broken or broken after winding 1-5 turns around the mandrel. The diameter of the mandrel is equal to the diameter of the wire.

(5) Yb / t5103-93 oil quenched tempered carbon spring steel wire
Oil quenched and tempered steel wire shall be produced to the size of finished product, and then oil quenched and tempered steel wire shall be delivered with tempered martensitic structure. Microstructure uniformity is an important index to determine the properties of oil quenched and tempered steel wire. Due to the limited hardenability of carbon spring steel wire, the core of too large steel wire can not be completely transformed into martensite after quenching and tempering. Therefore, the standard stipulates that the supply diameter of oil quenched tempered carbon spring steel wire is less than 12.0 mm.

Compared with cold drawn carbon spring steel wire, the tensile strength and elastic limit of oil quenched tempered steel wire with diameter ≤ 2.0 mm are lower than that of cold drawn steel wire. However, it is impossible to obtain high tensile strength by drawing with large reduction ratio after sorbite treatment of large size steel wire (Φ≥ 6.0 mm). However, as long as oil quenched and tempered steel wire is completely quenched, it can obtain higher tensile strength than cold drawn steel wire. Even under the same tensile strength, the elastic limit of oil quenched tempered steel wire is higher than that of cold drawn steel wire.

The anisotropy of cold drawn spring steel wire is obvious, while that of oil quenched and tempered steel wire is almost the same. The fatigue life and stress relaxation resistance of oil quenched and tempered steel wire are much better than that of cold drawn steel wire, the working temperature is higher (150 ~ 170 ℃), and the creep resistance is better. In addition, oil quenched and tempered steel wire has good straightness, and the steel wire is elastic and straight after opening coil, and has better formability when winding spring. Therefore, large size oil quenched and tempered carbon spring steel wire almost replaced cold drawn carbon spring steel wire in developed countries.

(6) Yb / t5102-93 oil quenched tempered carbon spring steel wire for valves
The relationship between Yb / t5102-93 and Yb / t5103-93 is equivalent to that of GB / t4358-1995 and GB / t4357-89. The former is used to make dynamic spring, and the latter is a general standard, which is mainly used to make static spring. Because the dynamic oil quenching and tempering spring has more strict requirements on the structure uniformity and the hardenability of carbon steel is limited, Yb / t5102 has smaller supply specification (diameter ≤ 6.0 mm).
The service range and quality control requirements of oil quenched and tempered carbon steel wire for valves are basically equivalent to group G of GB / t4358-1995, which will not be repeated here.

2.2 standards, application scope and process characteristics of alloy spring steel wire
There are three types of alloy spring steel wire in China: alloy spring steel wire, oil quenched and tempered silicon manganese spring steel wire, and oil quenched and tempered chromium silicon alloy spring steel wire for valve. According to the current use situation of alloy spring in developed countries, the proportion of oil quenched and tempered steel wire is increasing. According to Japanese industrial standard (JIS), all alloy spring steel wires are supplied in oil quenching and tempering state.
(1) GB / t5218-1999 alloy spring steel wire

The standard combines the original gb5218-85 “silicon manganese spring steel wire”, gb5219-85 “chromium vanadium spring steel wire” and gb5221-85 “chromium silicon spring steel wire” into one standard.
The standard is applicable to the production of alloy spring steel wire for high and medium stress spring. The steel wire wound spring can only be used after quenching and tempering after forming.
The standard lists three grades of 60Si2MnA, 50CrVA and 55CrSiA, and stipulates that other grades of steel wire can be supplied according to the requirements of the demander.

The steel wire is generally delivered in cold drawn condition. The tensile strength σ B ≤ 1035mpa and Hb ≤ 302 are inspected for the finished steel wire with diameter ≤ 5.0mm, which is equivalent to the light drawing state. In the production of medium and large specifications (Ф > 8.0), the cold drawing reduction rate of finished products shall not exceed 25%, and the surface reduction rate of small steel wire (Ф ≤ 5.0) shall not exceed 30%. The steel wire delivered in annealed state is too soft, so it is easy to produce dead bending. When winding the spring, the spring shape is not good and the pitch is uneven. When the reduction ratio of cold drawing is too large, the steel wire is too hard, and the rebound is large when the spring is wrapped, so the forming of the thick spring is difficult. Therefore, it is most suitable to supply the steel wire directly wrapped with spring in light drawing state. For the customers who need cold working (such as flattening, rolling into special cross-section, etc.) when the steel wire is purchased, the annealed steel wire shall be recommended for delivery.

In order to ensure the performance of the winding spring, the finished steel wire shall be wound for 6 turns on the mandrel with the diameter less than or equal to 5.0 mm, and shall not be broken or broken.
Decarburization and surface defects seriously reduce the fatigue life of spring, which must be strictly controlled. In particular, 60Si2MnA and 55CrSi have high silicon content and are easy to decarburize during annealing. Low temperature and long time annealing process is recommended for spheroidizing annealing and recrystallization annealing of semi-finished products. As mentioned above, for springs with high fatigue life requirements, polished steel wire must be selected, but it is necessary to distinguish between annealing polishing and cold drawing polishing. When 50CrV soft steel wire is polished, the grinding debris is easy to adhere to the steel wire surface and form irregular small white spots. Therefore, cold drawing polishing process should be adopted as far as possible to reduce the “white spots” on the surface.

Under the condition of surface quality assurance, the inclusion content becomes the most important factor affecting the fatigue life. Therefore, the standard stipulates that non-metallic inclusions and graphite carbon inspection can be added when the demander has requirements.