Precipitation of Carbonitride containing Ti,Ni,V and Effect of Rare Earths in Alloy Steel
Author of the article:ZHANG Yangyang;PENG Jun;ZHANG Fang;CHANG Hongtao;WANG Yongbin;LIU Lixia
Author's Workplace：School of Materials and Metallurgy,Inner Mongolia University of Science and Technology,Baotou 014010,China;Inner Mongolia Key Laboratory of Advanced Ceramic Materials and Devices,Baotou 014010,China
Key Words：alloy steel the second phase precipitation rare earth
Abstract：With the development of industrial production,the properties of alloy steels have higher requirements. The properties of steel can be improved by adding a certain amount of Nb,V,Ti and other microalloying elements. The lower contents of N and C in Nb,V and Ti alloy steels are easy to precipitate fine second-phase carbonitrides,which can effectively refine the grain size and produce precipitation strengthening. Under the condition of high nitrogen,irregular large size nitride precipitates from steel deteriorate the properties of steel. VN precipitated by proper amount of nitrogen can promote the nucleation of intracrystalline acicular ferrite and improve the toughness at low temperature. The VC and Nb C precipitated from grain boundary can inhibit the grain growth,but the high content of Nb and C in steel will lead to the precipitation of tens of microns of long strip carbides along grain boundary and reduce the grain boundary-related properties. Rare earth atoms in solid solution are segregated at grain boundaries,which reduces the segregated precipitation of alloying elements at grain boundaries. The rare earth elements transform the magnesia-alumina spinel,which can be used as the core of carbide nucleation,into the rare earth compound,which can not be used as the core of carbide nucleation,effectively reducing the number of large size carbides. Rare earth inhibits the precipitation of niobium carbide at high temperature,but helps the precipitation of small size carbide at low temperature. The rare earth spheroidizes the irregular shape of carbide,reduces the stress concentration at the sharp corners,and effectively enhances the beneficial effect of the second phase carbide in the alloy steel on the steel properties.
