Patented Cold Drawn Spring Steel Wire

Patented Cold Drawn Wire

wire drawn to size by cold deformation of a starting material that has been subjected to a thermal treatment of patenting

Spring Wire Grades

The grade of spring wire used depends on the stress level and the nature of the duty. Where springs are subjected to static stresses or infrequent dynamic loading, a wire grade for static duty (S) shall be used. In the other cases with frequent or predominantly dynamic loading and where small coiling ratios or severe bending radius is required, a wire grade for dynamic duty (D) shall be used. Depending on the stress level, spring wire is manufactured in three tensile strength grades: low, medium and high.

Chemical composition

Manufacture Process

wire drawn to size by cold deformation of a starting material that has been subjected to a thermal treatment of patenting, giving structure suitable for subsequent rolling or drawing.

HEAT TREATMENT consisting of AUSTENITIZING followed by COOLING under conditions suitable for producing the appropriate structures for subsequent wire-drawing or rolling. The medium in which the PATENTING takes place should be specified, for example air, lead bath etc.

Drawing condition

All cold drawn spring wire is commonly shaped by drawing. A distinction as to the method of drawing can be

made between:

 dry drawn (d): drawn through pulverized lubricants such as soap, stearates or similar substances;

 paste drawn (ps): drawn through very viscous greases of mineral oil base, tallow, synthetic waxes or

similar substances;

 grey bright (gr): drawn through rape oil, thin-bodied mineral oils or similar substances;

 wet drawn (w): drawn through aqueous emulsions of greases or oil emulsions;

 liquor finished (l): drawn through aqueous solutions with or without addition of metal salts.

Form of delivery

The wire shall be delivered in unit packages of a coil (singles, carriers or formers), spools, spoolless cores or as straight lengths. Unless otherwise agreed at the time of ordering, the form of delivery will be coils; straight lengths shall be supplied in bundles.

Coating and surface finish

The spring wire may be supplied phosphate coated (ph) either dry drawn or wet drawn, copper coated (cu), zinc (Z) or zinc/aluminium (ZA) coated.

Other coatings, considered as special, can be agreed between the purchaser and the supplier. If no specific surface finish is specified, the type of finish shall be at the manufacturers discretion. In addition the wire can be ordered with an oiled surface for all surface finishes.

Surface treatment

The surface for spring wire generally has a coating for facilitating wire drawing and spring forming.

Exceptionally the material will be uncoated. Common surface coatings are:

 bright (b): without any special coating: standard borax coating or lime-coating may be applied;

 phosphate coated (ph): the wire has been treated in a solution to form a metal-phosphate layer on the

surface;

 reddish (rd): the surface is covered with a thin copper, generally a conversion coating;

 copper plated (cu): the surface is covered with a (uniform) thick copper coating;

 galvanised (Z): the surface is covered with a zinc coating;

 zinc/aluminium coated (ZA): the surface is covered with a Zn 95/Al 5 coating;

 yellow coated (y): this applies only to liquor finished products whereby a mixture of tin salts and copper

salts are added at the liquor finishing;

 white (liquor finished) (wh): this applies to liquor finished products whereby tin salts are added for liquor

finishing

Surface quality

The surface of the wire shall be smooth and as free as possible from grooves, tears, rust and other surface defects, which have a noticeable adverse effect on the application of the wire.

In the case of zinc or zinc/aluminium coated spring wire the amount of zinc or zinc/aluminium on the wire surface shall satisfy the minimum values specified

Out of roundness

The difference between the maximum and minimum diameter of the wire at the same cross section shall not be more than 50 % of the total permissible deviation specified

Test inspection

Chemical composition

Tensile test

Surface defects

Decarburization

Zinc and zinc/aluminium coating

Adherence of coating

Coiling test

Torsion test

Wrapping test

Bend test