The effect of micro alloying elements (vanadium, titanium) additions on the austenite grain growth behavior in medium carbon steel containing nitrogen

Abstract

The austenite grain growth behavior of microalloying elements free steel (nitrogen steel) and micro alloyed steel (V−N steel and V−Ti−N steel) was investigated. The equilibrium dissolving behavior of precipitates was calculated by thermodynamic software and the morphology was observed by tunneling electron microscope. Moreover, grain growth kinetics was analyzed through theoretical calculation. Results show that the austenite grain size of V−N steel and V−Ti−N steel are significantly refined by the undissolved precipitates compared to nitrogen steel. Due to higher dissolving temperature of (vanadium, titanium)(carbon, nitrogen), the austenite grain of V−Ti−N steel keeps fine and increases slowly from 900 °C to 1250 °C. The difference of activation energy between V−N steel and V−Ti−N steel was supposed to come from the effect of different kinds of precipitates on the austenite grain growth. Compared to the vanadium rich (vanadium, titanium)(carbon, nitrogen), the titanium rich (vanadium, titanium)(carbon, nitrogen) is larger and more stable in view of its existence at higher temperature. The decrease of pinning forces can be attributed to the decrease of volume fraction and increase of radius of (vanadium, titanium)(carbon, nitrogen). Compared with critical grain sizes, the larger experimental grain sizes lead to grain growth from 900 °C to 1250 °C.

Effect of Zr on austenite grains growth behaviour of high strength Ti microalloyed low carbon steel

“…Therefore, the Arrhenius equation can be used to represent the relationship between austenite grains growth, reheating temperature, and holding time. 13,14 where, D is the average grain size, μm; A is the rate constant; Q is the surface activation energy of grain boundary diffusion, J/mol; T is the heating temperature, K; t is the holding time, s; R is the gas constant, 8.314 J/(mol K) and n is the time index.…”

“…Therefore, the Arrhenius equation can be used to represent the relationship between austenite grains growth, reheating temperature, and holding time. 13,14…”

Simulation and Microstructural Analysis of Twin-Induced Plasticity Steel Cylinder Deep Drawing

“…To take full advantage of the TWIP effect, the strength of the SFE must be adjusted to an appropriate value. In the study of low-carbon high-manganese steel, it has been found that adding an appropriate amount of an alloying element, such as Si, generally reduces the SFE of austenite [ 9 , 10 ] and imparts it with extremely high ductility (60–80%), enhanced strength (600–1000 MPa), and an improved strain-hardening rate and energy absorption capacity [ 11 , 12 , 13 ]. Additionally, Si also stabilizes austenite through solid solution strengthening [ 14 , 15 , 16 ].…”