Is the rounder the cast steel shot the better?

　　Answer: No.

　　In the process of granulating to obtain steel shot, molten steel is cooled from liquid to solid state, and shrinks during the cooling process. This shrinkage is carried out in a free state, and there is no riser like casting castings to reduce the volume after shrinkage. Part of the molten steel is replenished, so elliptical particles with concave surface appear. This kind of particles has undergone sufficient shrinkage, and the shape is not round but the structure is dense. It is dense and has internal defects such as shrinkage porosity and shrinkage cavities. From the effect of use, the rounder the steel shot is not the better. Steel shot is usually used in the field of cleaning, and the cleaning efficiency of steel shot with high roundness is lower than that of steel shot with shrinkage. Throwing energy E=1/2mv2, the roundness is poor, the shrinkage is good, and the structure is dense, so the same volume, the mass m is large, the impact energy is high, and it is not easy to break; on the contrary, the roundness of the steel shot is good, the structure is not dense, and the particles Small mass, low kinetic energy, and easy to break. On the market, the reason why most of the cast steel shot has good roundness and poor quality is due to the limited production conditions of the manufacturer, the small diameter of the granulation tank (8-14 meters), and the small drop from the centrifugal disc to the water surface (0.2-1 meters). ), that is, the width and height of the workshop are not enough to ensure that the liquid steel pellets formed by centrifugal molding have sufficient cooling and shrinking time, instantly enter the water, the surface is cooled, and the roundness is good, but the interior has not been solidified, resulting in shrinkage porosity and many shrinkage holes. The shot breakage rate is high. Only when the diameter of the granulation tank is greater than 20 meters and the forming drop is greater than 2 meters, can the steel shot be fully shrunk.