Stainless Wire Operating Temperatures

Operating temperatures for the 300 series are typically 400-450 degrees.

If higher operating temperatures are required, we suggest 17-7PH (550-

600 degrees)

Have even higher temperature requirements? Go with superalloys such as Inconel X750 or Inconel 600.

Temper

Stainless wire is drawn from the annealed state. Annealing is a process where the wire is transformed during heat treat.

• After annealing, wire is considered soft in the tensile range of 80-120,000 PSI. The wire is then drawn to a particular size

• During the drawing process, the wire hardens due to cold work and gains strength

How it works – Example: A mill would like to result in wire .040” diameter in the spring temper condition. In order to achieve the diameter and desired temper, each finish size of material has a specific drawing process. This process may have to be adjusted slightly depending on the exact chemistry of the material involved. The goal is to meet the diameter tolerance per the ASTM A313

Typical Process for Tempering:

The manufacturing mill would start with a larger diameter wire than desired in the soft or annealed condition

It would then be drawn through a series of dies to reduce the diameter but will gain strength during the reduction process. However, it can only be drawn so far before becoming too hard or brittle

In this example let’s say we draw the .250” to .100”. The material is now cold worked (drawing process) and at .100” becomes very hard, too hard to draw any further or it will become brittle. But we still need to get it down to .040”

At .100” in the hard state we must again anneal to soften. During the annealing process the wire will be cleaned before annealing. Pre-coating will be put on after annealing

After the annealing process is completed the material is again soft at .100”, pre-coated, and now ready to draw down to .040. Now the wire is drawn again through a series of dies, reducing it a little through each die (reduction in area) until it gets to its finished size of .040”. At that point, it will be within its tensile strength requirement and be ready to sell to spring customers

Passivating Treatment

Corrosion properties of stainless steel are attributable to a very thin, invisible oxide film that completely covers the surfaces of the parts and prevents corrosion from taking place. Passivation removes any surface contamination, usually iron so that this film layer is not interrupted.

• Passivation enhances the formation of the oxide film for maximum corrosion resistance

• Passivation removes metallic and non-metallic coatings

• How it works – done by immersing the parts in a nitric acid solution, normally for 30 minutes

Stress Relief

The process of heating material to a suitable temperature, holding long enough to reduce residual stresses and then cooling slowly enough to minimize the development of new residual stresses.

Often suggested for stainless finished parts such as springs after the coiling process

How it works – During the spring coiling process, additional stresses are introduced into the wire. Heat treatment post coiling relieves the stress

Suggested Stress Relief:

o 300 Series = 700 degrees for one hour

17- 7PH = 900 degrees for one hour