The grinding ball is manufactured by the Algerian Foundries (ALFET – Tiaret). It is used by the cement industry to transform the rock into fine, used in the cement manufacture. This product undergoes very frequent wear. This wear occurs in various forms (abrasion wear and impact wear) and each has a varying impact on this product life. Abrasion wear is the result of friction between many surfaces (rock, crusher shielding and balls between them), between which a sliding contact occurs, and causes a metal wrenching and a mechanical disintegration of these surfaces. The impact wear is the result of the shock between these surfaces (rock, crusher shielding and balls) and the ball that hits these surfaces from multiple angles, causes their disintegration. Generally, wear resistance improves when hardness increases and a very hard material is more resistant to wear because it less risk to seize in presence of particles abrasive and it opposes their penetration in its surface layer. Wear is estimated, in this work, by the mass loss of the heat-treated balls. A correlation between the hardness and abrasive wear of the balls is established in this work.
Mechanical properties, wear resistance and impact resistance of a high-alloy chromium cast iron used in the fabrication of grinding balls have been studied. A rank of tempering heat treatments under several temperatures 500°C, 525°C, 550°C and 575°C was performed after austenitized at 1050°C. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) techniques have been used to characterize the microstructures and identify the phases. The wear balls tests were conducted in a rotating drum with a velocity 0.5 r/s. The tribological tests were carried out by evaluated a weight loss as function time. The measurement of the rebound resilience was determined by Charpy impact tests. The results of XRD showed the presence of the martensite, carbides type M7C3 and M2C for all tempering heat treated. The hardness of the sample increased after the tempering and reach nearly 65 HRC at 1050°C. In another hand, it decreased after the tempering treatment it could be explained by precipitation of the carbides type M2C.
The effects of tempering treatments on the service life of grinding balls were analyzed. The relationship between hardness, abrasive wear, and microstructure HCWCI was determined. The role played by matrix and carbides in improving the hardness and wear resistance was investigated.High chromium white cast iron (HCWCI) is used in mining, crushing plants, as mill liners, and in the manufacture of grinding balls. The grinding ball is the essential element in fine fragmentation. It must have an excellent life to counter extreme wear and impact conditions that it undergoes. Hence it is important to improve its mechanical properties. This study aims to find the effect of tempering temperature on microstructure, hardness, and abrasive wear of High Chromium White Cast Iron used in the manufacture of grinding balls. In this study, the balls in high chromium white cast iron with 12 to 17% Cr, of 50mm and 70mm in diameter were austenitized at 950°C for 45 min and 55 min for the balls of 50 and 70mm then were quenched in forced air. The balls were tempered at 250°C, 400°C, and 600°C for 120 min and 180 min for both diameters 50 and 70mm respectively, and cooled in the furnace. The results showed that tempering practiced at 250°C and 400°C gives an excellent hardness than balls austenitized at 950°C. It is about 60 HRC and it drops to less than 50 HRC for the tempering at 600°C. This tempering causes a significant mass loss (short life) but tempering at 250°C and 400°C decreases this loss by up to 1.6%. The results of XRD showed the presence of the martensite and carbides type M 7 C 3 after tempering at 250°C and a ferritic matrix after tempering at 600°C.
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