Microstructure and properties of low carbon CuNiCrMnMo steel after heat treatment

A low carbon CuNiCrMnMo steel was designed and the microstructure and mechanical properties of the test steel processed by three different heat treatment conditions(oil quenching tempering,water quenching tempering as well as direct quenching after rolling tempering)were investigated.The Rp0.2 of 668 MPa,Rm of 721 MPa,and impact absorbed energy(KV2)of 138 J at-60 ℃ were achieved by oil quenching and tempering at 600 ℃ for 1 h,while the Rp0.2 of 668 MPa,Rm of 721 MPa and KV2 of 216 J at-80 ℃ were achieved by water quenching and tempering at 650 ℃ for 1 h.As expected,the best combination of strength and low temperature toughness was obtained in the direct quenched and tempered samples with the Rp0.2 of 700 MPa,Rmof 764 MPa and KV2 of 182 J even at-80 ℃.