Steel grit has appropriate hardness, fast cleaning speed, and good resilience. The products with internal corners or complex shapes can be cleaned uniformly and quickly, shortening the processing time, increasing the throughput, improving production efficiency, saving energy and reducing production costs . Chemical composition is the most basic index of steel shot steel grit, it will determine the microstructure of steel shot steel grit and the effect of subsequent heat treatment. The carbon (C) content should be moderate. Silicon (Si) manganese (Mn) can improve the strength and hardness of the steel shot, and it should be as high as possible (not less than 0.8%). Sulfur (S) and phosphorus (P) are harmful elements, which can easily cause brittleness of the steel shot, leading to premature cracking. It should be as low as possible.
Standard for high-quality steel shot steel grit: it can apply more kinetic energy to the work surface, effectively play a role of cleaning and strengthening, has a sufficiently long fatigue life, and reduces consumption in use. If or the steel grit is too soft, the cleaning speed of the steel shot will be slowed down and work efficiency will be reduced. During shot peening, too soft steel shots cannot produce suitable residual stresses, and the forces of low hardness shots cannot be compensated by increasing the impact time. If the hardness is too high, it will produce an undesired surface morphology, increase the crushing probability of the projectile, make the consumption too high, and cause greater wear to the equipment and increase equipment maintenance costs. Therefore, proper hardness is also critical.
The microstructure of the steel shot (sand) must be able to resist deformation and reduce energy loss and fatigue life when acting on the work surface. Tempered martensite is the most fatigue resistant. In addition, fragile carbides must be reduced in the microstructure and microstructure, otherwise the steel shot (sand) will be prematurely broken and the amount of use will be increased. Steel shots (sand) must contain as few physical defects as possible that can cause abrasive rupture. Because of the production process used, steel shots (sand) always have certain physical defects. There must be corresponding procedures in production to control and reduce the proportion of defective particles.