Study On The Effect Of Modification Used Amorphous Modifier In A Ultrahigh Carbon Steel

The ultrahigh carbon steel is a kind of iron and steel material with carbon content between high carbon steel and cast iron.It is easy to occur eutectic transformation to form coarse eutectic ledeburite in general solidification process duo to the high carbon content,resulting in the brittleness of materials.It has become the key to ensure the practical application in engineering of ultrahigh carbon steel that how to inhibit the precipitation of coarse eutectic ledeburite and refine matrixstructure.Inthispaper,theultrahighcarbonsteelcontaining Fe-1.85C-0.34Si-1.55Cr-0.45Al-0.60 Mn was modified with modifiers in different thermodynamic states.The influence of different modification on the solidification process of ultrahigh carbon steel was revealed by analyzing the phase composition,microstructure and mechanical properties of samples treated with different modifiers and comparing with that of non-modified ones,so as to explore a way to effectively improve the microstructure and toughness of materials by controlling solidification process.The results of microstructure observation showed that compared with the unmodified samples,the skeletal matrix is weakened with 0.3wt.%crystalline modification,the coarse eutectic ledeburite was broken and appeared to be isolated island or blocky,but the precipitation of eutectic ledeburite was not completely inhibited.However,the microstructure of material was obviously refined and the precipitation of eutectic ledeburite was effectively inhibited by the amorphous modification.When the amount of amorphous modifier was0.2wt.%,the formation of eutectic ledeburite was completely inhibited,and the secondary carbides distributed uniformly in the matrix as regular fine particles.The mechanical properties test results showed that the tensile strength of material with the addition amount of 0.2wt.%amorphous modification reacheed 1340MPa,which is much higher than that of unmodified experimental steel,and increased by 27.62%compared with that of crystalline modification.The impact toughness value reached 11.5J/cm~2,far higher than unmodified experimental steel,and compared with crystalline modification material increased by 43.75%.Amorphous modifier works through the metamorphic mechanism,while the crystalline modifiers works through the mechanism of inoculation,the former modified effect is better than the latter.