Effect Of Amorphous Modification On Microstructure And Mechanical Properties Of Ultrahigh Carbon Steel

The ultrahigh carbon steel is a kind of Fe-based alloy materials containing 1.0-2.1wt.% carbon.It exhibits brittleness at the conventional casting solidification state due to the occurrence of coarse carbide network,which is the biggest obstacle for industry application.In this paper,the crystalline and amorphous rare earth-ferrosilicon-Na/K modifiers were used to modify an ultrahigh carbon steel containing 1.81 wt.% carbon,respectively.Based on the study of microstructure and mechanical properties of experimental steels under different modification conditions,the influence of amorphous modification on carbide precipitation morphology of ultrahigh carbon steel was investigated.The experimental results revealed that although the skeleton structure carbides were suppressed with crystalline modification,the continuous network carbides still exist,compared with direct coagulation steel.By contrast,the finer carbide blocks of the experimental steel modified with same composition of rare earth-ferrosilicon-Na/K modifier distributed homogeneously in the matrix,and the continuous network carbides were significantly suppressed.In addition,when the addition of the amorphous modifier reach to 0.2wt.%,the morphology and uniform distribution of granular carbide are better,the amorphous modified steel displayed tensile strength of 1182 MPa and impact toughness of 11 J/cm2 and the performance is of high engineering application value.Remarkably,the carbon content of the experimental steel designed in this paper has exceeded the upper limit of carbon content of general ultrahigh carbon steel,but the precipitation morphology of carbide can be effectively improved by modification with amorphous rare earth-ferrosilicon-Na/K modifier.The comparative analysis result of transverse and longitudinal microstructure of the steel test bar demonstrate that upon on modification with amorphous rare earth-ferrosilicon-Na/K modifier,the steel test bar obtain a nearly uniform structure of carbide precipitation morphology,and the level of uniform is better than the bar modification with same component crystalline modifier.