1.Characteristics of wear resistant steel ball
The composite wear-resistant casting steel ball has excellent comprehensive properties such as high strength, strong toughness and fatigue resistance. The steel ball is made of manganese, silicon and nickel as phase change elements. After compound inoculation and special heat treatment process, the high performance duplex bainiteis formed. When the initial surface hardness is HRC (50-52) and the impact toughness is greater than 22j / cm2, the surface hardness of the steel ball will increase continuously during the grinding process, which will greatly improve the wear resistance of the steel ball. In addition, the spheroidal graphite in the steel ball makes its weight lighter than that of the ordinary casting steel ball, and the mill load is reduced, which plays a certain role in energy saving.
2.Determination of initial ball
According to the feed particle size of the mill, the diameter of the test steel ball is determined to be 150 mm. It is used in the No.2 series 5522 semi autogenous mill in the grinding section of the concentrator. The initial ball loading is 20 tons, and the supplementary amount of the steel ball during the test is 200 g / T (into the grinding capacity); the 180 mm forged steel ball is still used in the 1 series. The local process is checked every month, and the abrasion, ore discharge fineness, overflow fineness of classifier and fineness and grade of iron concentrate are compared. The test lasts for 2 months.
3.Test data and analysis
During the test, the comparison of steel ball wear and concentrate grade indexes; local process inspection indexes: semi autogenous mill discharge fineness, classifier overflow fineness, fine powder fineness; the crushing and out of roundness of φ 150 mm steel ball. It can be seen that the grinding grades of the two series are the same during the test. The grade of the refined powder of the 2 series is 0.68% higher than that of the 1 series. The wear of the forged steel ball with the diameter of 180 mm and the casting steel ball with the diameter of 150 mm are 279 g / T and 204 g / T respectively. The unit consumption and unit cost of steel ball with diameter of 150 mm are reduced by 26.88% and 22.75% respectively.
According to the data, the grade of refined powder in series 2 is 0.68% higher than that in series 1, and the wear of forged steel ball with diameter of 180 mm and cast steel ball with diameter of 150 mm are 279 g / T and 204 g / T respectively. The ore discharge, classifier overflow and fineness of the 2 series of φ 5522 semi autogenous mills are 6.34%, 5.29% and 3.43% higher than those of the 1 series, and the production capacity of the 2 series-200 mesh is 0.1 T / (M3 · h) higher than that of the 1 series. The results show that the use of 150 mm steel ball is more suitable for improving the grinding discharge fineness and – 200 mesh production capacity of semi autogenous mill, and the fineness and grade of fine powder are also improved. The diameter of the steel ball with diameter of 180 mm is too large to fully play the role of grinding, and the wear of steel ball itself is fast.
It can be seen that the average crushing and out of roundness rates of the φ 150 mm multiphase wear-resistant casting steel ball are 1.17% and 4.43% respectively, both of which meet the test requirements.