At present, the grinding balls widely used at home and abroad are mostly high-carbon high-alloy foundry grinding balls and high-carbon low-alloy forged grinding balls (or foundry grinding balls), in the dry process of thermal power plants, cement industry, etc. Use high and low chrome cast iron balls. In the wet process of mining, high-carbon low-alloy grinding balls are often used.
There are many types of grinding balls in the country. Due to the defects of the market, the use of grinding balls is not determined according to the process benefits, and the randomness is very large. The main varieties are chromium-based high-alloy cast irons. Such as: Cr8, Cr12, Cr15, Cr18, Cr24, Cr26, etc., low chromium cast iron such as: Cr2 and martensitic ductile iron. Martensitic ductile iron and low-chromium cast iron are of the same grade in terms of wear resistance, and their differences are in the production process. The high-alloy cast iron has excellent anti-wear properties. The higher the alloy, the better the anti-wear performance and the good economic benefits. Some people have misunderstood that the application of high-chromium ball cement mill is good, but the power plant is not suitable. In fact, domestic thermal power plants have a good record of using a large number of high-chromium balls, such as: Wuxi, Yueyang, Xingtai, Hengyang, Zouxian, Matou, etc. After the power plant uses high-chromium balls and no longer wants to use other balls, high-chromium cast iron grinding balls are rapidly spreading in power plants. In the dry grinding process of power plants, cement plants and other dry grinding processes, the ton wear of high-chromium balls is only 15~50 grams. The use of high-chromium balls not only saves costs, reduces worker labor, reduces mechanical and electrical consumption, but also reduces waste of resources. It should be unknowingly said: high-chromium balls can be called environmentally-friendly grinding balls and green grinding balls.
The varieties of forged balls and rolled balls are mainly high carbon chromium molybdenum alloys and medium and low carbon manganese alloys. The process of forging ball and rolling ball is simple, the manufacturing cost is low, and the economic benefit is considered. The wet process of mine type generally adopts low-chromium alloy grinding ball, and its wear in iron ore, copper ore and molybdenum ore is generally 500-700 grams. Increasing the hardness of low chromium alloy balls is the most effective way to reduce wear. We have increased the hardness of low-chromium balls to about HRC55, and its wear in copper mines is around 550 grams. Due to the production process, the quality of the forged ball should be slightly better than the rolling ball.
If the diameter is greater than 110mm, it is recommended to use high carbon chromium molybdenum low alloy forged ball, mainly considering that the crushing rate of large diameter cast ball may be higher. The carbon content of the forged ball is generally about 1%, and the chromium content is less than 2%. The hardness of low-chromium cast balls should generally be around HRC48. The hardness of low-chromium cast iron balls should be increased as much as possible to improve economic efficiency. The hardness of the low chromium cast iron ball produced by the author's company and the Indian manufacturer is as high as HRC55, and the difference between the core and the surface hardness is very small. The diameter of the grinding ball in a thermal power plant is generally not greater than 60 mm. Cement and mines should be graded according to the diameter of the mill, the surface shape of the liner and the particle size of the feed. There is only one grading principle: to reduce the diameter of the grinding ball as much as possible, because the ball mill is a grinding machine, and if it relies on it to bear the breaking effect, even if it is only a small part, it is very inappropriate.
Under the premise of material selection, the grading of the grinding ball is very important. The ideal grinding ball grading plus the ideal lining surface shape allows the mill to achieve maximum efficiency. The correct choice of material is the fundamental guarantee for the ideal grinding ball grading, the ideal lining surface shape to maintain the best state for a long time.