Grinding media steel balls are used in the mineral processing of ore to extract precious metals, particularly in copper and gold industries. Ore particles must go through the communition process: > grinding -> fine grinding -> ultra-fine grinding. Ores are ground down to required sizes to liberate precious metals from gangue materials, prior to subsequent concentration processes. Grinding or communition is carried out in mills, partially filled with steel balls or rods commonly referred to as grinding media.Mills require continuous refilling with new balls as the old ones wear out. Choice and consumption of grinding media is related primarily to the volume of ore processed and ore characteristics (abrasiveness, particle size and specific energy input).
SAG Mills: 4” – 6” (100mm-150mm) forged-steel balls are recommended. Cast balls are not suitable because the outer crust is hard (typically in excess of Brinell hardness 450). Cast balls cannot sustain the high impact of SAG mill crushing forces and are recommended for cement grinding, and ultra-fine wet regrinding operations instead. Ball Mills: 1”-4” (25mm-100mm) forged-steel balls are recommended
Factors used to determine grinding ball-quality operational use include: Frictional forces between liners and balls. Abrasiveness of feed material. Impact forces in the mill. Susceptibility to corrosion – especially in wet processes. Simulations have shown that in certain instances: The use of forged-steel balls, compared to low-density cast-steel balls, increases throughput by 2% – 4%. Specific energy consumption is reduced by up to 3.5% (at constant feed/product size). Forged-steel grinding balls achieve a considerably better result in comparison for tests with other grinding media such as cylpebs, boulpebs, or high-chromium-cast balls, taking into account the total cost-calculation of the mill process. Studies of SAG Mills performance show that poor quality cast balls with porosity result in the production of a significant excess mass of steel scats in the SAG mill. If such balls are being used in a milling operation, consider using higher quality balls; they offer more economic viability. Worn out balls can be a source of iron, especially if the rate of wear is too high. This could result in the formation of iron sulphides, which may affect downstream metallurgical processes. Reduced wear rates are essential.
In comminution, high wear rates of grinding media represent very high production costs, and must be minimised by proper selection of materials, especially those for balls. Ideally the wear rates should be less than 1kg/ton. Marked balls tests can be performed to check the abrasive wear rates of particular balls.
Grinding media is not a commodity and thus selection should be done with the core basis of improving grinding performance, improving efficiency, attainment of lowest sustainable cost and maximize mill availability For Quality control-A full chemical analysis, hardness profile and micro-structure, can play an integral role in selecting cost effective grinding media balls. This should also be complemented with a good quality control program to ensure consistency in the supply chain. YANTAI HUMON assists mining executives in cutting costs without cutting corners! We assist mining companies by offering the full range of grinding media . Grinding media represents a large portion of your total grinding cost and has a significant impact on your OPEX .