This final installment of the Abrasive Blasting Media series will discuss the merits of using both Steel Shot and Steel Grit for blasting. Both of these media types are produced from scrap steel which is melted, modified and then solidified into a generally round shape (Shot) or angular particles (Grit).
Steel Shot produces a very smooth finish on the surface of metals. The rounded shape does not strip a surface very effectively but rather peens the surface to produce a clean, smooth and (sometimes) polished finish. The smaller the shot the better the polish but the less aggressive the peening operation. The peening action of the shot is also used to impart compressive strength or hardening to metals.
Steel Grit is used when aggressive stripping action is required. Steel is softer than Aluminum Oxide so will not fracture as easily but the higher density produces a forceful blasting process. Smaller sizes and softer formulations of grit are used when lighter cutting is required while larger sizes and harder steel formulations will maintain the particle angularity and a high strip rate.
Since both Steel Shot and Steel Grit have a high bulk density of about 250 pounds per cubic foot, special or modified equipment is necessary to blast these media using air pressure alone. Steel is often used in wheel blast operations where the media is propelled by a wheel using controlled force.