The tensile strength of cold drawn spring steel wire is slightly higher than that of oil tempered steel wire. The large specification of cold drawn steel wire elastic force is too large, winding the spring is very difficult, so the cold drawn spring steel wire application specification is generally less than 8.0mm, oil quenching tempered steel wire application specification is generally less than 13.0mm. In fact, the diameter of 13.0mm spring is used to light tension spring steel wire, cold drawing wound made into shape and then quenched and tempered. Steel wire with diameter above 15.0mm is mostly made by heating winding process.

If the zinc coating is good, but in 3% nitric acid when the light, the coating has dark shadow, passivation occurs when the film is brown, may be caused by foreign metal impurities such as copper or lead in the galvanizing liquid. When problems occur in the process of galvanizing large coil galvanized wire, the temperature and current density are checked first, and then the content of zinc and sodium hydroxide in the plating solution is measured and adjusted through the analysis of the plating solution. Whether DPE content is low can be determined by hull cell test.

VFR-25:

What Is FRP Grating?