Grinding costs account for 30-50% of the total cost of ore processing and are a major operating cost in mining production. Approximately 50% of the grinding costs are due to the consumption of steel balls and liners. Based on a large amount of production practice data and cost research, the cost of steel ball media loss reaches 40-45% of the grinding cost. With the booming mining economy and the sharp increase in ore processing volume, cost control of consumables such as steel ball media has become a key factor affecting the profit of individual ore body development. Gangnuo New Materials Co., Ltd. has a case, A ball mill with a processing capacity of only 150t/h reduced its annual steel ball usage by nearly 20% and saved nearly 1 million yuan in steel ball costs through reasonable addition of steel balls and control of steel ball filling rate. Therefore, controlling steel ball consumption is crucial!

The consumption mechanism of steel ball media mainly includes: abrasive wear, impact wear and corrosive wear. The operating environment in the mill has a significant impact on the consumption of steel balls, including slurry potential, dissolved oxygen concentration, slurry PH and ore particle size distribution, mainly divided into mill characteristic factors, slurry factors, abrasive properties factors, and steel ball attribute factors.

1. Influence of mill factors

As the inner diameter of the mill increases, the height of the steel ball rises, the impact force increases, and the impact wear of the steel ball increases; while the higher the mill speed, the stronger the abrasive effect on the steel ball in the mill; the higher the steel ball filling rate in the mill, the greater the abrasion between the steel balls, greatly increasing the steel ball consumption per unit ore grinding. At this moment, improving the wear resistance of steel balls is the key, and Gangnuo will help you achieve it.

2. Influence of slurry factors

Gangnuo company's research and development of special steel balls, in production practice, it is found that, As the PH value of the slurry increases, its corrosion intensity on the steel ball decreases. We adjusted the slurry PH value from 6.0 to 12.0, and the steel ball consumption decreased by 48.72%, The economic benefits are significant, and it also meets the requirement of controlling the PH value of flotation in alkaline conditions, without affecting the subsequent selection operation.

3. Influence of ore properties factors

The crushing and grinding operation of ore is mainly caused by the impact and abrasion of steel balls. As the hardness of ore increases, the corrosion rate of steel balls increases. When the hardness of ore is higher than that of steel balls, the corrosion rate of steel balls with different hardness is very high; as the ore particle size increases, the abrasion rate of steel balls increases.

4. Influence of steel ball attribute factors

4.1 Influence of steel ball diameter

The larger the diameter of the steel ball, the greater the impact potential energy, and the greater the impact wear on the steel ball. Therefore, there is a rule that the wear of large steel balls is large and the wear of small steel balls is small. Some people even summarize the relationship between energy consumption and steel ball consumption in grinding. When steel consumption is high, energy consumption is also high, Generally, steel consumption is 0.035-0.175kg/kW·h, The unit energy consumption of large-diameter steel balls is higher than that of small-diameter steel balls.

4.2 Influence of steel ball shape

In mining grinding operations, most mills use steel balls as grinding media, and a small amount of steel rods are used. The steel consumption of steel rods is higher than that of steel balls. In recent years, short cylindrical grinding media, especially Capsule-shaped steel segments, not only have better grinding effect than steel balls, but also have significantly lower steel consumption, saving about 10%-15%. Gangnuo's rolled capsule-shaped steel segments have been used in many mines with obvious effects, and the over-grinding phenomenon has been alleviated.

4.3 Influence of steel ball hardness

The wear of steel balls in the mill is mainly impact plastic deformation wear and cutting abrasive wear, so the grinding steel balls are required to have high toughness and impact fatigue resistance, and have appropriate hardness on this basis. However, the increase in the hardness of steel ball materials will inevitably lead to an increase in brittleness, which will promote the increase in the breakage rate. How to achieve coordination between the two has become the direction of steel ball material research and development. The hardness of steel balls is not the higher the better, and excessive hardness of steel balls will also be detrimental to grinding. The main reasons are: firstly, the steel balls rebound severely, causing some energy loss during rebound, so the energy of the steel balls is not used more for crushing, thus affecting the energy conversion efficiency of the crushing process; secondly, when the hardness of the steel balls is too high, the sliding is severe when the balls contact each other, and the ore particles between the balls cannot be effectively engaged, weakening the grinding effect of the ore particles. These problems have been effectively solved by Gangnuo.

Mainstream method for steel ball quality testing—drop ball test

The drop ball test of steel balls was first proposed by the US Bureau of Mines, and later became the internationally unified standard method for testing and evaluating the crushing resistance of steel balls, which can effectively evaluate the fatigue resistance, toughness and wear resistance of steel balls. The steel ball is dropped and impacted on the ground steel plate or steel ball at a certain height until the steel ball is broken. The standard for single steel ball cyclic drop test is more than 5000 times without breakage, which is judged as qualified.

Currently, the world's tallest steel ball drop test machine is built in Gangnuo New Materials Co., Ltd. Each batch of steel balls produced by the company must be sampled and tested by a 16-meter ultra-high drop ball test machine. Only when a single ball continuously falls more than 20,000 times without falling off, deformation, or breakage can the batch of steel balls pass the acceptance and leave the factory.

World's tallest steel ball drop test machine

(Height from right to left is 12 meters, 10 meters, 16 meters, 10 meters)

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