Investigation of the effect of different heat treatment conditions applied to high chrome white cast iron on mechanical properties

Çemaş Casting Industry is the only manufacturer in Turkey that produces by casting method in the production of grinding balls/silpeps used in the cement and mining industry. The balls produced in the company are in the high chromium white cast iron class, and it is aimed to reduce the raw material cost by reducing the chromium content in this material and not to reduce the wear resistance compared to the high chromium balls. In the current heat treatment process, the whole surface of the ball cannot be cooled homogeneously, since the ball is cooled with air after the heat treatment. This causes non-homogeneous abrasion and plastic deformation of the ball in the cement mill. This study was aimed to develop the heat treatment process for non-homogeneous wear. For homogeneous cooling on the ball surface, the oil quenching process was carried out. Raw material costs have been reduced as the Cr ratio has been reduced. Experiments were carried out on Ø 90 mm diameter balls, which are the most commonly used balls with 17-19% Cr content used in cement mills. When the iron-chromium phase diagrams were examined, it was predicted that the same hardness and microstructure would be obtained by reducing the amount of Cr from 18% by weight to 9-12%. In this study, the chromium ratio was reduced from 17-19% to 9-12%, and both air and oil quenching studies were carried out and the wear rates were compared. It has been tried to obtain a material with the same wear resistance by working lower carbon ratio than the existing productions, since the reduction of the chromium ratio will cause the decrease of the wear-resistant carbide phases in the material and the increase of the martensite ratio. Raw material costs have been reduced by reducing the % Cr ratio. When we look at the details of the study, the main aim is to obtain low Cr balls with the same hardness (Min. 58 HRc) and microstructure (Min. 70% Martensite) with 17-19% Cr balls in current mass production. Afterwards, the wear performances of high Cr and low Chromium balls were compared. Improvements in homogeneous wear, microstructure and hardness properties were investigated by reducing the amount of chromium on one hand and homogeneously cooling in the designed oil cooling facility on the other. In the prototype drum, the balls were cycled depending on time and the same or less wear amount was compared with the existing ball.