This specification covers general purpose carbon steel spring wire intended for springs not subjected to severe repeated stress. Other quality wire, such as music spring wire or valve spring quality wire, should be used where freedom from surface defects and decarburization are required to insure maximum fatigue life for springs operating under repetitive stress.

The mechanical properties of type I wire are obtained by heat treatment. Springs formed from type I wire are used without further heat treatment, except for suitable low-temperature treatment to relieve residual stresses caused by coiling. Springs formed from type I wire can generally be held to closer dimensional tolerances than springs formed from type II wire.

The mechanical properties of type II wire are obtained by cold working. Springs formed from type II wire are used without further heat treatment, except for suitable low-temperature treatment to relieve residual stresses caused by coiling.

Type III wire is a soft, spheroidized annealed wire used where springs must be formed of soft wire. Type III, condition A, wire is generally suitable for more severe deformation than type III, condition B, wire. Springs should be heattreated to specified mechanical properties after forming. The composition of type III is the same as type I.