The propertes and microtnicture of high-speed axle steel DZ1 and DZ2 with Ni contents 0. 20%

0. 80% and 1. 20% are studied by using metalloraphic microscope and SEM etc. The results show that with Ni content increasing from 0. 20% to 1. 20%

the tensile strength and yield strength of the steel increases respectively from 710 MPa to 759 MPa and from 535 MPa to 608 MPa； the impact toughness of steel at 20 ℃ and -40 ℃. impact toughness is inproved

especially at -40 ℃

the transvese impact energy of steel increases from 87 J of 0. 20% Ni contents to 136 J of 1. 20% Ni contentsand the longitudinal impact energy of steel increases from 94 J to 179 J； the temperature of steel's tough-brittle transition decreases from -30℃ to - 100 ℃. The high-speed railway axle steel structure of 3 kinds of composition is Bainite + tempered martensite structure

and the bainite volume increases with the increase of Ni content

and steel microstructure became finer and more uniform after the increase of Ni content.