The steel balls of ball mill can be considered as the "main force" of grinding, and their quality and ratio are directly related to the efficiency of the equipment and even the whole production line, so they are valued by many users. This article introduces the specifications, ratio and material of ball mill steel balls for your reference.
I. Steel ball specifications
Usually, the diameter of ball mill steel balls is between Φ20mm and Φ125mm (such as 40mm and 60mm for small balls, 80mm for medium balls, and 100mm or 120mm for large balls), and the diameter of steel balls used in super large ball mill is Φ130mm to Φ150mm, etc.
2、Steel ball proportioning matters
Under normal circumstances, there is no need to add small balls when grinding ore in ball mill, because the reasonable friction between steel ball and steel ball, steel ball and ore, steel ball and ball mill liner during normal operation of ball mill will increase the abrasion and make the big ball grinding small and medium ball grinding to small ball.
The proportion of steel balls of different sizes is also different, but when the ball mill is enabled, it needs large, medium and small balls for proportioning, and the addition should be made in accordance with 80% of the installed ball volume given by the manufacturer, because after the ball mill is installed, the ball mill size gears need to mesh, and the processing volume is also to be gradually increased, and after two or three days of normal continuous operation of the ball mill, check the size gear meshing situation, and when everything is normal, the ball mill will be opened to the hole cover for the second time. Open the ball mill inlet hole cover for the second time to add the remaining 20% steel balls.
3、Steel ball grading scheme
To develop the ball mill steel ball grading scheme, usually start from one bin (i.e. coarse crushing bin). For multi-bin mills, the steel ball grading of the first bin is particularly important, according to the general principle of cross-grading, that is, the small ball diameter of the previous bin determines the large ball diameter of the next bin, and so on, the first bin actually dominates the grading of all other bins.
At present, there are two representative grading methods in one bin of ball mill: one is the application of common multi-stage grading method, and the other is the secondary grading method.
(1) Multi-stage ball allocation method
This is a traditional ball-matching method, which usually uses 4-5 kinds of steel balls of different specifications for grading, and the specific steps are as follows:
① Determine the large ball diameter according to the large particle size of the material to be ground; determine the average ball diameter according to the average particle size of the material to be ground.
② Determine the number of steel ball grades. If the size of the material to be ground varies greatly, it is advisable to choose a variety of specifications, and vice versa, it is possible to choose a few less.
③According to the principle of "small at both ends and large in the middle" of the grinding body and the characteristics of the particle size distribution of the material, set the composition ratio of each specification of steel balls.
④Calculate the average ball diameter of the mixed steel balls, and compare with the average ball diameter of the original steel balls, add steel balls according to the ratio of steel ball size, if the deviation between the two is large, it is necessary to set a new composition ratio of various steel balls, re-allocation of balls until the deviation between the two is small.
(2) Secondary ball allocation method
Only two kinds of steel balls with different diameters are used for grading. The diameter of the large ball depends on the size of the material to be ground, and the diameter of the small ball depends on the size of the space between the large balls. According to the relevant information, the diameter of the small ball should be 13%-33% of the diameter of the large ball, the general small ball accounts for 3%-5% of the mass of the large ball, and in principle should ensure that the amount of small ball admixture should not affect the filling rate of the large ball.
4, steel ball material analysis
(1) high manganese steel: the material of ball mill steel ball toughness, good technology, low price, its main feature is that under the action of large impact or contact stress, the surface layer will quickly produce process hardening, its process hardening index is 5-7 times higher than other materials, wear resistance has been greatly improved.
(2) Low carbon alloy steel balls: ball mill steel balls made of low carbon alloy have good toughness and low price, and under the same working conditions, their service life is more than 1 times higher than that of low chromium cast balls.
(3) High chromium cast iron: a wear-resistant material with excellent anti-wear performance, but low toughness, easy to brittle broken and expensive in the process of use.
(4) High carbon high manganese alloy steel: the ball mill steel balls under this material are mainly alloy structural steel containing chromium, molybdenum and other elements, with high hardness and good toughness, and under the same working conditions, its service life is more than 1 times higher than that of high manganese steel balls.
The ratio and quality of steel balls are crucial to the ball mill, if you have any questions in this regard also welcome to leave a message to discuss with us.