The hardness of steel shot directly affects cleaning efficiency, surface roughness, workpiece deformation, micro-crack risk and shot peening strengthening effect. It must be selected properly according to the workpiece material, thickness, surface requirements and processing purpose.
1. Hardness Grades & Basic Characteristics (HRC)
1.Low Hardness: 30–40 HRC (HV 300–400)Moderate impact force, no easy damage to workpieces, long service life; lower cleaning efficiency and relatively higher roughness.
2.Medium Hardness: 40–50 HRC (HV 400–500)Balanced performance with high versatility; ideal for both cleaning and surface strengthening with controllable roughness.
3.High Hardness: 50–60 HRC (HV 500–600)Strong impact force, fast cleaning and low roughness; may cause deformation or micro-cracks on soft materials with higher consumption.
4.Ultra-high Hardness: ≥60 HRCFor aviation and high-strength strengthening applications; outstanding strengthening effect but high brittleness, only for high-hardness workpieces.
2. Hardness Requirements by Workpiece Material
1.Soft Metals (Aluminum, Aluminum Alloy, Copper, Magnesium Alloy)Required hardness: 25–35 HRCAvoid indentation, deformation and metal contamination; only for removing oxide film and oil stains.
2.Mild Carbon Steel & Ordinary SteelRequired hardness: 35–45 HRC; 35–40 HRC for thin platesBalance rust removal efficiency and anti-deformation performance.
3.High-carbon Steel, Alloy Steel & CastingsRequired hardness: 45–55 HRC; 50–58 HRC for strengthening partsRemove heavy rust and burrs, and improve fatigue resistance.
4.High-strength Steel, Stainless SteelRequired hardness: 50–60 HRCQuickly remove thick scale and heavy rust for anti-corrosion coating.
3. Hardness Requirements by Processing Purpose
1.Rust & Scale Removal: 45–55 HRC
2.Shot Peening & Surface Strengthening: 40–58 HRC
3.Fine Cleaning & Matt Surface Finishing: 35–45 HRC
4.Thin & Precision Workpieces: 25–35 HRC
4. Key Notes
1.The hardness of steel shot shall be 5–10 HRC lower than the workpiece hardness to prevent surface damage.
2.Hardness tolerance shall be controlled within ±3 HRC to ensure uniform surface treatment.
3.Match particle size with hardness for optimal treatment results.
4.Excessively high hardness shot will cause micro-cracks on soft workpieces.
