Study On Austenite Nucleation And Growth Behavior Of 30Cr1Mo1V HP-IP Rotor Material

HP-IP rotor materials of 30Cr1Mo1 V was heated to different temperature region,the aim of which was to study the phenomenon of heredity in microstructure and the growth behavior of grain of 30Cr1Mo1 V.In order to reveal the nucleation and growth behavior of austenite grain,coarse and non-equilibrium microstructure in 30Cr1Mo1 V and 30Cr2Ni4 MoV rotor steel were reheated to the temperature of two-phase region and above in this paper.The austenite nucleation and growth behavior of the two rotor materials in the temperature region of Ac1~Ac3 and above Ac3 were observed and analyzed.By analyzing and concluding the austenite growth behavior when 30Cr1Mo1 V material was reheated to temperature above Ac3,the austenite growth model in high temperature was conducted.At the same time,the sub-zero treatment was applied to the heating process of 30Cr1Mo1 V material to investigate if it can refine austenite grain and if it can reduce the degree of mischcrystal.The effect of sub-zero treatment on austenite nucleation and growth behavior of 30Cr1Mo1 V rotor material were realized.All the results have certain guidance functions for real application.The specific results in this paper are as followings:1.The addition of alloying elements can affect the degree of recrystallization of ? phase in 30Cr1Mo1 V and 30Cr2Ni4 MoV rotor materials,which also have influence on the nucleation mechanism and orientation of new-formed austenite.The austenite of 30Cr1Mo1 V rotor material mainly form with globular crystal nucleuses And with larger contents of Ni elements,the retarding effect on recrystallization of ? phase and austenite nucleation temperature is extremely higher for 30Cr2Ni4 MoV rotor material.There also will be more retained austenite grains in 30Cr2Ni4 MoV after high temperature quenching in contrast to 30Cr1Mo1 V rotor steel.It should be noted that acicular crystal nucleuses mainly depend on the retain austenite grains to nucleate.As a consequence,acicular crystal nucleuses occur between the laths of ? phase firstly in the reheating process for 30Cr2Ni4 MoV low pressure steel.2.Not only the formation and growth of acicular crystal nucleuses can generate heredity in microstructure,but the globular crystal nucleuses also have an effect upon it in the process of reheating the coarse and non-equilibrium microstructure to austenization.But for the 30Cr1Mo1 V and 30Cr2Ni4 MoV different materials,whose contents of alloy elements are different,the effect of globular crystal nucleuses on the degree of heredity in microstructure is entirely different.There are more Ni element,the degree of heredity in microstructure is more seriously.3.When the coarse and non-equilibrium microstructure of 30Cr1Mo1 V steel is reheated to temperature above Ac3 a bit,the size of austenite grain has no obvious change and the grains form with a certain specific orientation.When the reheating temperature is up to above 1000?,the size of austenite become larger and larger with increasing temperature: the average austenite grain size increases slowly when the reheating temperature is 1000?~1100?;when the temperature is 1100?~1125?,the austenite grain grows sharply;the size of austenite grain keep constant basically if the reheating temperature become higher.In the condition that the reheating temperature is constant,austenite grain grows quickly in a short holding time.With the holding time increasing,the growth rate of austenite grain reduces to a constant value gradually.However,in the case that the reheating temperature is above 1100? and the holding time is 20 h,austenite grain is still growing.On the basis of above analysis,the Beck model and the austenite growth model of 30Cr1Mo1 V steel in isothermal and non-isothermal condition of 30Cr1Mo1 V steel when its coarse and non-equilibrium microstructure is reheated to the high temperature region were established.4.Sub-zero treatment can accelerate the transformation of ? phase to ? phase in the process of the non-equilibrium microstructure reheated to austenite,which leads to prior nucleation and complete austenization in the two-phase temperature region of Ac1 to Ac3.When the reheating temperature is below 1000 ?,the austenite grain is refined with sub-zero treatment.Moreover,the degree of mischcrystal decreases by applying sub-zero treatment.Nevertheless,the size of austenite grain and the degree of mischcrystal increase with the increasing temperature when reheating to above 1000 ?.