Abstract: Effect of niobium (Nb) microalloying on the microstructure and properties of quasi-bainite wear-resistant cast steel with low carbon (about 0.26%) and different niobium content was analyzed by means of thermal expansion tester, scanning electron microscope, tensile and impact test and wear test. The results show that the addition of Nb promotes the growth of the quasi-bainite and the prior austenite grains decrease from 120.81 μm to 87.65 μm when Nb content increases from zero to 0.062%, and the average grain size is reduced by 27.4%. Meanwhile, the addition of Nb caused a decrease in wear rate of the steel, and the hardness is also decreased, but the impact absorbed energy, lateral expansion value, yield strength, tensile strength and reduction of area are all increased. When Nb content is 0.024%, the wear rate reaches the lowest value of 0.104%, and the wear resistance is the best, moreover, the comprehensive mechanical properties are also the best with hardness of 420.4 HV0.1, impact absorbed energy of 42.6 J, side expansion value of 67%, yield strength of 826 MPa, tensile strength of 1326 MPa and percentage reduction of area of 7.7%, while the content of retained austenite is relatively high at 8.4%.

Key words: niobium microalloying, quasi-bainite, wear-resistant cast steel, microstructure, mechanical properties