The principle of forming steel ball hardness is different.
Hot-rolled ball is through the unique quenching process to make hot steel ball cooling rapidly, so that the austenite in the microstructure of metal into a very wear-resistant martensite structure, so it is through quenching the hardness, its hardness can reach 63~65HRC.
The casting ball mainly relies on adding a quantitative alloying element chromium (CR) to make the steel ball produce certain hardness and wear resistance, the higher the content of CR, the better the hardness and wear resistance of the ball, but the higher the cost of the steel ball; At present, CR content in domestic high chromium ball is generally 8~12% and hardness is 55~59HRC ; The latest introduction of a high alloy casting ball with CR content up to 18%, but also add a small amount of tungsten (W) and molybdenum (MO) and other rare metals, hardness of 60~62HRC, good wear resistance, but high production costs, ton sales price of more than 14000 yuan.
Density is different.
The hot rolled ball is used as the production raw material for the hot rolling of the billet, and the hot rolling ball is also extruded through the roll forming process, so the density of the hot rolled ball is generally more than 7.85g/cm3 above.
Foundry Ball because of the use of the traditional sand casting process, so the internal and surface of steel balls will inevitably produce pores and sand, there are also casting waste edge, so the density of the general in 7.75G/CM3 below.