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Welcome to MIZHI
For consultation/feedback, please call the service hotline: +86-136 8495 9862 Email:cennia@szmizhi.com
HeavyDuty Surface Cleaning and Descaling
In industries such as construction, shipbuilding, and oil and gas, where large steel structures require aggressive cleaning to remove rust, paint, or mill scale, hardened steel shot with HRC 60–65 is the standard choice. These highhardness shots deliver the impact energy needed to dislodge thick deposits while withstanding the repeated collisions with hard surfaces. For example, cleaning a rusted offshore oil platform requires shot that can penetrate layers of corrosion without deforming—hardened SAE S550 (2.8–3.4 mm) shot, with its combination of size and hardness, excels in this role, reducing cleaning time by 30% compared to softer alternatives.
Shot Peening for Fatigue Resistance
Shot peening relies on controlled impact to create compressive stress layers in metal components, enhancing their resistance to fatigue failure. The hardness of the shot must be carefully matched to the workpiece material to avoid overpeening or surface damage. For peening highstrength alloys like 4340 steel (used in aircraft landing gear), hardened shot with HRC 58–62 is ideal, as it balances penetration depth with surface integrity. In contrast, peening softer materials such as aluminum (used in automotive wheels) requires slightly lower hardness (HRC 55–58) to prevent surface indentation while still achieving the desired compressive stress.
Foundry and Casting Applications
Foundries use steel shot to clean castings and remove sand from mold cavities, a process that demands both abrasiveness and durability. Cast iron castings, with their high hardness, require hardened shot (HRC 60–63) to efficiently dislodge sand and scale. For example, cleaning engine blocks in an automotive foundry using hardened SAE S330 (1.7–2.1 mm) shot reduces shot consumption by 40% compared to nonhardened shot, as the particles maintain their shape through thousands of impacts. For aluminum castings, which are softer, shot with HRC 55–60 is preferred to avoid damaging the casting’s surface while still achieving thorough cleaning.
Automotive Coating Preparation
Preparing automotive body panels for painting requires a shot that can create a uniform surface profile without embedding contaminants. Hardened shot with HRC 58–60, such as SAE S170 (1.1–1.4 mm), is ideal here: its spherical shape ensures consistent surface roughness (Ra 2–4 μm), promoting paint adhesion, while its hardness prevents deformation that could lead to uneven texture. Unlike nonhardened shot, which may flatten and create “smearing” on the panel surface, hardened shot maintains its integrity, reducing the need for postblast sanding and improving paint finish quality.
Maximizing Durability: Handling, Recycling, and Maintenance
Even the hardest steel shot will degrade over time, but proper handling and maintenance can extend its lifespan significantly. Contamination control is critical: mixing hardened shot with nonhardened or worn particles can accelerate wear, as softer particles act as abrasives against harder ones. Regular screening using vibrating sieves or magnetic separators removes fines and nonhardened debris, ensuring that only viable shot remains in the system.
Recycling practices also impact durability. Hardened steel shot can be recycled 10–15 times (compared to 3–5 times for nonhardened shot) before its size falls below the usable range. However, each recycling cycle introduces minor wear, so monitoring particle size distribution is essential. For example, SAE S330 shot that has worn down to SAE S230 (1.0–1.4 mm) may still be usable for less demanding applications, such as cleaning small machinery parts, maximizing material utilization.
Equipment maintenance plays a complementary role. Wheel blast machines, which propel shot at high velocities, must be calibrated to avoid excessive friction between shot particles and machine components. Worn impellers or liners can create uneven particle trajectories, increasing collisions between shot particles and accelerating wear. Regular inspection and replacement of these components, combined with proper blast pressure settings, ensure that hardened shot is used efficiently, minimizing unnecessary degradation.