Process Applications of Springs

In addition, the forming process and heat treatment process of spring steel wire shall also be taken into consideration. Both cold-drawn spring steel wire and oil-quenched and tempered spring steel wire are used to wind springs directly in their supplied state, and the formed springs can be put into service directly after stress relief treatment. The tensile strength of cold-drawn spring steel wire is slightly higher than that of oil-quenched and tempered steel wire. Large-size cold-drawn steel wire has excessive elastic force, making spring winding difficult. Therefore, the commonly used size of cold-drawn spring steel wire is generally less than 8.0 mm, while that of oil-quenched and tempered steel wire is generally less than 13.0 mm. In practice, spring steel wire in lightly drawn condition is mostly selected for springs with a diameter of 13.0 mm, which are cold-drawn and wound into shape before quenching and tempering for use. Steel wires with a diameter of over 15.0 mm are mostly processed into springs by hot winding technology.

Carbon spring steel is a widely used and high-consumption category among spring steels. It contains 0.60% to 0.90% carbon and 0.3% to 1.20% manganese without any other alloying elements added, leading to relatively low application costs. Through appropriate processing or heat treatment, carbon spring steel wire can achieve high tensile strength, sufficient toughness and excellent fatigue life. However, as steel wires must be manufactured in compliance with standards, finished steel wires are required to maintain not only a high elastic limit and favorable toughness indicators, but also a satisfactory fatigue limit and spring fatigue life. For this reason, stricter requirements are imposed on the steel’s purity, content of non-metallic inclusions and gases, ferrite content and surface decarburization degree.

Tension and compression springs are mostly mass-produced with a wide variety of sizes, and they can be applied after minor modifications. If only a small quantity is needed and strict requirements on spring performance are not demanded, such springs are easily available on the market yet carry a high unit price.

In contrast, users requiring springs for exclusive mechanical components mostly place custom orders with professional spring manufacturers. Those lacking independent design capabilities may also pay extra fees to request manufacturers to conduct trial production.

In recent years, the industry has adopted CNC computer-controlled or mechanical spring forming machines to realize automatic and labor-saving production with relatively stable product quality. Driven by increasingly stringent quality requirements under ISO and international standards, nearly all spring manufacturers are capable of providing test report data covering spring performance characteristics.