Elucidating the Influence Mechanism of Vanadium Addition on Dendritic Structure and Precipitated Phase of 30Cr15Mo1N Ingot During Pressurized Solidification

By analyzing element segregation and dendritic growth kinetics in combination with microstructure observation and thermodynamic calculation, the influence mechanism of vanadium addition on the dendritic structure and precipitated phase in 30Cr15Mo1N ingots was elucidated. With vanadium addition, the carbonitride types in 30Cr15Mo1N ingots include lamellar M23(C,N)6, globular M2(C,N), and blocky M(C,N). The as-cast structure of the 30Cr15Mo1N ingot is divided into two parts: the dendritic structure, which is mainly composed of martensite and residual austenite, and the interdendritic region, which is primarily composed of precipitated phases like proeutectoid ferrite and carbonitrides. On the one hand, increasing the vanadium content can reduce the amount of martensite and residual austenite in the ingot by suppressing the growth of dendrites and reducing the size of dendrites. On the other hand, the amount of proeutectoid ferrite in the 30Cr15Mo1N ingots increased with an increase in vanadium content and distance from the center due to element segregation in the residual molten steel of the interdendritic region. Under the combined effect of element segregation in the interdendritic region and restricted dendritic growth, the size of carbonitrides showed an increasing trend with increasing the vanadium content.