The French surface finishing company Winoa Abrasives have introduced two innovative products in their range of peening media that are targeted at a number of markets, including springs. Their Hard Resilient Shot (HRS) combines a very high hardness range (700-780 HV) with high toughness and impact resistance, making it ideally suitable for peening high strength spring materials used in suspension applications – leaf springs, coil springs, torsion bars, stabilisers, etc. The company claim that, not only does the HRS media have a longer service life than standard shot, but it is also possible to achieve the same peening intensity - in terms of Almen values - using lower blasting velocities, leading to considerable peening cost reductions. Their Ultra-Fine Shot (UFS) is, as the name suggests, very small diameter (50-150 µm), and is intended for duplex peening operations, such as are applied to engine valve springs. According to the company, this high-carbon media has very high hardness (770-900 HV) and has a long life/low consumption, so is very cost effective in comparison to the fine non-metallic media that is commonly used for the second-stage of duplex peening operations.
A technical article relating to these two materials appeared in the May 2013 edition of the magazine Metal Finishing News, and copies are available from IST - contact Margaret O’Malley for details (E-Mail; Margaret@ist.org.uk).