How to configure the steel ball of the gold ball mill?

01Specification and quantity of the steel ball

Generally, the diameter of the steel ball is between Φ20mm and Φ125mm. Among them, the diameter of the small steel ball is generally Φ40mm and a 60mm, the diameter of the medium steel ball is generally 80mm, and the diameter of the large steel ball is Φ100mm or Φ120mm. The diameter of the super large steel ball is Φ130mm-150mm.

Theoretically, when the filling amount of steel ball in the ball mill is 40%, the ball mill can obtain the ideal output. But in the actual production, the filling rate of the steel ball in the ball mill is mostly about 35%, that is, the volume of the steel ball in the gold ball mill is kept slightly below the horizontal centerline of the ball mill.

02Material of the steel ball

As the "consumable" in the grinding operation, the wear degree of the steel ball is different due to the different material. At present, the mainstream steel balls of the gold ball mill on the market mainly include casting steel balls and forged steel balls.

Casting steel ball

Casting steel balls are mainly low chromium casting steel ball, medium chromium casting steel ball and high chromium casting steel ball, whose hardness, impact value and breakage rate are related to the metallographic structure of steel. The higher the chromium content, the better the wear resistance of the steel ball.

Forged steel ball

Forged steel gold ball mills mainly include low carbon alloy steel ball, medium carbon alloy steel ball, high manganese steel ball, rare earth chromium molybdenum alloy steel ball. The impact toughness of the forged steel ball is large, not easy to deform, but the crushing rate is low.

In general, the casting steel balls are suitable for the dry grinding and the forged steel balls are suitable for the wet grinding.

03Ratio of the steel ball

Different sizes of the steel ball have the different proportion.

When first enabled, the gold ball mill needs the large, medium and small steel ball for matching, and the steel mill ball for the first time should be added to 80% of the amount limit that the ball mill manufacturer of ball mill suggests. Because the gears of the ball mill need mesh after the installation, and the processing capacity of the ball mill is increased gradually, then the ball mill operator needs to observe the condition of gear meshing in two or three days. If all is going well, the ball mill operator can open the hole cover to add the remaining 20% of steel ball.

Usually, the small steel balls are used only in the first addition. When the ball mill is running normally, there will be reasonable friction between the steel ball and the steel ball, the steel ball and the ore, the steel ball and the lining plate of the ball mill, which makes the wear increase. The large steel ball is ground into small, and the medium steel ball is ground into the small steel ball, so there is no need to add the small steel ball under normal circumstances. However, if the particle size of the useful mineral does not realize the monomer separation, and the grinding fineness of the ball mill cannot meet the separation requirements (especially the flotation separation requirements), the appropriate amount of small steel balls can be added into the gold ball mill.

In addition, the ball mill steel ball is constantly worn in the operation, the ball mill operator must regularly make up the steel ball and maintain the load filling rate of the steel ball and reasonable ratio.

04Grading of the steel ball

Determine the grading scheme of the steel ball usually starts from the first warehouse (namely the coarse crushing warehouse). For the multi-bin ball mill, the grading of the first bin is particularly important. According to the cross-gradation principle, the minimum diameter of the steel ball in the previous bin determines the maximum diameter of the steel ball in the next bin. It can be seen that the grading of the steel ball in the first warehouse actually dominates the grading of the steel ball in the other warehouses.

At present, there are two common grading methods for the first warehouse of the ball mill: one is the widely used multi-level grading method, and another is the secondary grading method.

Multi-level grading method

Multi-level grading method is a traditional grading method of the steel ball. Adopting 4-5 different specifications of steel balls for grading. The specific steps are as follows:

◆ The upper limit of the ball diameter is determined according to the upper limit of particle size of the grinding material. The average diameter of the steel ball is determined according to the average particle size of the grinding material.

◆ If the grain size of the grinding material changes greatly, it is advisable to choose the various specifications of steel ball.

◆ The composition proportion of each specification steel ball is set according to the proportioned principle of "small at both ends and large in the middle" for the grinding body and the distribution characteristics of material size,.

◆ Calculate the average ball diameter of the mixed steel ball, and compare with the original average ball diameter of the steel ball, add the steel ball according to the proportion of the ball size. If the deviation is large, it is necessary to set the composition proportion of various steel balls and rematch the balls until the deviation is small.

Secondary grading method

The secondary grading method means to only select two different diameters of ball mill steel balls for grading. The diameter of the large steel ball depends on the particle size of the grinding material, and the diameter of the small steel ball depends on the size of the space between the large steel balls.

Usually, the diameter of small steel ball should be 13%-33% of the diameter of large steel ball. Generally, the small steel ball accounted for 3%-5% of the mass of large steel ball, and the incorporation amount of small steel ball shouldn’t affect the filling rate of large steel ball in principle.

These are the main aspects of the steel ball involved in the grinding process: specifications and quantity, material, ratio and grading. For the concentrator, the selection and application of the steel ball involve many technical problems, it is suggested that the mine owners carefully analyze their own actual situation, determine the suitable steel ball for the concentrator through consulting the professional gold ball mill manufacturers, thus avoiding the unnecessary economic losses.