抄録
The relationship of tempering temperature with wear resistance and residual stress of 25% Cr cast iron was studied. Abrasion tests were carried out with test pieces tempered at different temperatures. The results show that abrasion tend to increase with the increase in tempering temperature. The increase was especially remarkable when the tempering temperature exceeded 700K. The amount of sand erosion, however, was not noticeably affected by the tempering temperature, remaining at about the same value. Abrasion considered changing with the change in material hardness, whereas, sand erosion do with the change in the amount of carbide in the material. Residual stress after tempering was analyzed with castings of 30mm in diameter. The residual stress generated in the course of air hardening treatment decreased with the increase in the tempering temperature, but, started to increase after showing a minimum value at around 700K. The generation of residual stress is considered due to the cooling after heating and decomposition of the retained austenite over 700K, despite the stress relief effect by heating. Consequently, for reducing residual stress without losing wear resistance, tempering at 700K is recommended.
