How to Choose A Liner and Ball for A Ball Mill
There is no doubt that the liner and the grinding ball are in a cooperative relationship. They and the material together form a three-body abrasive wear. But what’s so good? It should be said that borrowing the concept of “basic hole system” or “basic shaft system” in mechanical design is the best understanding. As far as the ball mill is concerned, the influence of the lining plate on production is much greater than that of the grinding ball, so it should be “made of substrates”. Therefore, in the selection of the liner and the grinding ball, the first thing to decide is the liner. The service life of the liner must be more than two overhaul periods, and as far as possible, no maintenance is required. Priority is given to those liners with good reliability and high degree of wear resistance. For example: combined self-fixing high-chromium cast iron liners, the service life of coal mills in power plants can reach 20 years, the service life of cement mills is 10 years, and almost no maintenance is required.
The alloy steel lining in dual-medium quenching has a service life of more than 8 years in the coal mill of the power plant, about 3 years in the cement mill, and about 10 months in the iron ore.
Even the dual-medium-quenched low-chromium alloy steel lining can be used for more than 6 years in coal mills in power plants, about 2 years in cement mills, and more than 8 months in iron ore mills.
The hardness of the liner and the grinding ball should be above HRC50. This is mainly because the hardness of the hard phase in the abrasive is 6 ~ 7 on the Mohs scale. It is estimated to be close to HRC60. In theory, the hardness of the grinding medium is greater than or equal to eight percent of the hardness of the abrasive. Ten has the ideal anti-wear effect.
The grinding ball is easy to choose after the lining board is decided. As long as the service life of the lining board guarantees two overhaul periods, it should be advocated that the best wear resistance of the grinding ball is preferred. If the liner and the grinding ball can be changed for 10 years, it is of course ideal. One principle: reduce costs, reduce labor intensity, and increase the operating rate of ball mills.
Under the premise of “substrate-made”, grinding balls are allowed to have a hardness higher than HRC by 3 to 5 HRC. This is for high-manganese steel liners that should be eliminated, and it is fundamentally different from the popular concept.
Strategy of Choosing a Grinding Ball
- The material of high manganese steel and the traditional ball mill liner are not suitable. The epoch-making design of the combination self-retaining liner has great advantages, completely solves the problems of broken bolts and powder leakage, and reduces the maintenance volume by more than 98%. ;
- The combined liner can make full use of the quenching hardness of various high-hardness materials to make it exhibit the most ideal anti-wear performance.
- In the dry process, power plants and cement plants should preferentially choose dual-medium quenched medium and low chromium alloy steel liners or high chromium cast iron and high chromium cast steel liners, and choose high hardness high chromium cast iron grinding balls. Double-medium quenched medium and low chromium alloy steel has good economic benefits; in the mining wet process, from the economic point of view, high and medium carbon alloy steel linings or Cr10 ~ Cr20 series lower carbon cast iron are preferred. Liner and high hardness low chromium alloy grinding balls. However, grinding balls with a diameter greater than 110mm should be considered using high carbon alloy steel forging balls.
- The matching of the liner and the grinding ball should be from the viewpoint of “substrate system”. Under the premise that the service life of the liner is guaranteed for two overhaul periods, the wear resistance of the grinding ball should be the best. The hardness of the liner should be greater than HRC50, the hardness of the chromium-molybdenum alloy cast grinding ball should be greater than HRC52, and the hardness of the forged alloy steel grinding ball should be greater than HRC55. Generally, the abrasive ball with the best abrasion resistance is selected as much as possible.
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