Research on Impact Fracture and Microstructure of 40Cr Steel under Different Tempering Conditions

As one of the quenched and tempered steels, 40Cr steel is often used to manufacture the shaft in heavy-duty trucks. To adjust the working environment of the heavy-duty machines, 40Cr steel should have high impact property. In this study, different tempering cooling mediums were treated as critical influence on improving impact property of the steel. After heated under 520°C tempering temperature, the samples of 40Cr were cooled in air, oil and water, respectively. The experiments were carried out through charpy impact, metallographical and SEM analysis. The results has shown that 40Cr steel of high impact property and fine microstructure can be obtained when water is used for the tempering cooling medium.