Effect of Intermittent Water Spray Quenching on the Wear Resistance of Forged Grinding Balls Made of Steel 70SiMnCr

The efficiency of replacing traditional quenching in a bath by spray quenching to manufacture grinding balls ∅120 mm made of 70SiMnCr steel to reduce stresses and control the phase composition is investigated. A process of forging grinding balls with the use of water spray cooling is suggested, which ensures bainite transformation under isothermal conditions and formation of the specified structure. The W70A45W20 process, implemented at 200°C for 4.5 h, yields balls with a final volume hardness of 56 HRC and a toughness of 73 J. After this mode of heat treatment, the steel balls have a high wear resistance, and the main mechanism of their surface wear is plastic deformation and micro-cutting.