Shot Peening

 

Shot Peening is the single most effective method for improving the fatigue performance of springs; it is an essential manufacturing process for many applications in which springs are subjected to high cyclic stresses for prolonged periods.  A detailed process specification is critically important if the optimum performance is to be achieved.

Process parameters are: -

Shot size must be appropriate for the section size of the springs. 

Shot type is usually rounded ferrous shot of high hardness (i.e. conditioned cut wire or cast steel) or glass beads.  There can be a problem with ferrous dust residue remaining on the surface of springs made from corrosion resistant materials such as stainless steels, nickel alloys or copper alloys, hence the use of non-ferrous peening media.

Almen arc rise is the main process control parameter.  It is an indication of the intensity of the blast and is measured using either A, N or C type Almen strips depending on the energy of the shot stream.  The value specified should be the arc rise achieved when all the surface of the spring has been covered (known as saturation).

IST undertakes shot peening using two different types of peening machines:

Tilghman Wheelabrator (using 0.60 mm cut wire shot)

Two Airblast machines (one designated for glass bead work and one for steel shot up-to 0.30 mm).

IST’s shot peening service is backed by many years of practical experience and supported by our extensive technical research. The process is carried out within the scope of our ISO 9001: 2008 quality accreditation.

For more information contact Paul Batty (paul@ist.org.uk).

 


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