Development and application of Cr25 high chromium cast iron grinding ball (1)
Sun Tingxiang, Li Maohua, China Building Materials Equipment Corporation (100831)
High chromium cast iron grinding ball is widely used in building materials, metallurgy, mining, electric power, and other industries. After 20 years of development, we have basically finished grinding ball, more salary for material and some products have been able to earn 1:3 foreign exchange. But compared with the advanced international level, our country, high-chromium cast iron grinding ball, whether research or products are relatively backward, this mainly, the product’s performance, the variety is relatively single. The high chromium cast iron grinding balls made in America, Japan, Denmark, and Germany have formed a series of series, and the products are serialized. As far as the material of high chromium cast iron grinding ball is concerned, the content of chromium in the products of these countries can be anywhere from L2% to 36%, and the content of chromium in high chromium cast iron grinding ball of our country is 12% to 15%. Most of them are produced by hand. This high chromium cast iron grinding ball is used in dry, water, mud, production can, but used in the wet, operation, the effect is very poor. This is mainly due to the high chromium cast iron microstructure, medium carbide, formed between the Matrix structure, micro, and battery. High chromium cast iron grinding ball resistance, poor corrosion resistance, seriously reduced wear resistance.
To improve the corrosion resistance of high chromium cast iron grinding balls, give full play to their excellent wear resistance, and manufacture high quality grinding balls, China’s building materials industry, mainly based on Beijing Cement Machinery General Factory, with reference to advanced overseas experience, Cr25 grinding ball has been developed, and its application effect is good.
1.Effect of chromium content on wear and corrosion resistance of high chromium cast iron grinding ball
In wet grinding of raw materials, the grinding balls are not only subjected to impact fatigue and Abrasive wear but also to slurry corrosion, which will aggravate the wear and tear and promote the corrosion, so that the weight of the grinding balls in wet production far exceeds that in dry production, the weight loss of the ball mill in the center of the mill. High-chromium cast iron corrosion resistance, high-chromium cast iron grinding ball excellent, and excellent wear resistance will appear if it can effectively improve.
1.1 Corrosion Resistance of chromium and high chromium cast iron grinding ball
High Chromium cast iron, grinding ball corrosion wear, the main pharynx, is the carbide electrode, potential more elevated than the Matrix, the matrix corrosion of the carbide, the role of support, significantly weakened. High Chromium Cast Iron Matrix can be quickly passivated by adding a large amount of Chromium to improve the Matrix’s corrosion resistance and avoid the exfoliation of carbides.
N/8 Law: The increase of chromium content, high chromium cast iron, corrosion resistance, is not a gradual change, but in the chromium and iron atoms, the ratio reached 1/8,2/8, …, N/8 mutation occurred, so that the corrosion rate significantly decreased
1.2 Wear Resistance of chromium and high chromium cast iron grinding balls
The wear resistance of high chromium cast iron grinding ball mainly depends on carbide content in Matrix; the more carbide, the higher hardness, the better wear resistance.
Marafray formula for the amount of CRYSTALLINE CARBIDE IN HIGH CHROMIUM CAST IRON:
M7C3(％ )：12：33(C％ )+0．55(Cr％ )-15．2
When the carbon content is the same, the amount of carbonization of CR25 is significantly higher than Cr l5. With the increase of Cr/C, the hardness of eutectic carbide also increases. But the toughness decline, grinding ball easy to break, is again, the production of CR25 grinding ball. Cr l5 grinding ball technology is more complicated, the degree of massive, one of the reasons.