Roundness Screening of Steel Shot: A Key Process Ensuring Surface Treatment Quality

Steel Shot serves as a core abrasive for metal surface derusting, strengthening and polishing. Its roundness and particle size uniformity directly determine the blasting effect, workpiece quality and service life of equipment.Roundness screening is a critical purification step in both steel shot production and recycling. It ensures stable abrasive performance by accurately separating qualified round shots from deformed, broken and irregular particles.

After being cut and rounded in a rounding machine, steel wires may still contain deformed shots such as cylindrical, beveled and elongated particles (with a length-diameter ratio greater than 2). The roundness separator achieves sorting based on physical differences: as the inclined belt runs, round steel shots have low friction and roll down quickly, while irregular shots, with larger contact area and higher friction, are carried upward by the belt for separation. Multi-layer vibrating screens are then used to grade shots by aperture (e.g., 0.4–3.0mm), removing broken shots, dust and over-sized particles. Standards stipulate that the roundness of finished steel shots shall be no less than 90%, with total deformed shots below 10%.

Roundness screening delivers remarkable value: high-roundness steel shots ensure uniform impact, avoiding workpiece scratches and uneven roughness, and improving surface finish and strengthening consistency. It reduces wear on blasting machine impellers and guard plates caused by irregular shots, extending equipment life and lowering energy consumption. During recycling, timely removal of broken shots maintains concentrated particle size (screen passing rate ≥95%) and stable cleaning efficiency.

Modern technologies integrate roundness sorting, vibrating screening and air separation for automatic and precise sorting. High-quality steel shots must meet dual standards of roundness and particle size. As a key quality control step, roundness screening optimizes surface treatment effects and reduces overall costs, making it indispensable in foundry, steel structure, shipbuilding and other industries.