Abstract: Effects of quenching from 840 ℃ to 1000 ℃ and tempering from 300 ℃ to 600 ℃ on microstructure and mechanical properties of the high carbon and high silicon SWRS96Si steel were studied. The results show that the undissolved carbides dissolve gradually, the acicular martensite coarsens and the amount of retained austenite increases gradually with the increase of quenching temperature. When the quenching temperature is greater than or equal to 920 ℃, the amount of retained austenite is 21%-23%. During tempering, the retained austenite decomposes from 300 ℃ to 400 ℃, the martensite decomposition and the nucleation and growth of cementite occur during tempering from 400 ℃ to 466 ℃. When the SWRS96Si steel is quenched from 840 ℃ to 960 ℃ and tempered at 480 ℃, with the increase of quenching temperature, the percentage reduction of area of the steel decreases from 32% to 24%, while the strength increases from 1569 MPa to 1968 MPa. When quenched at 920 ℃ and tempered from 300 ℃ to 600 ℃, with the increase of tempering temperature, the twin martensite in the microstructure gradually decomposes into cementite and ferrite, the hardness of the steel reduces from 61 HRC to 42 HRC gradually, while the impact absorbed energy at room temperature increases from 1.6 J to 9.5 J.

Key words: high carbon steel, quenching and tempering, martensite, retained austenite, mechanical properties