The Effects of Nb Carbo-Nitride Precipitation Conditions on Abnormal Grain Growth in Nb Added Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4167-4172 ◽  
Author(s):  
Toshio Murakami ◽  
Hitoshi Hatano ◽  
Yosuke Shindo ◽  
Mutsuhiro Nagahama ◽  
Hiroshi Yaguchi
Keyword(s):  
Grain Growth ◽  
Ostwald Ripening ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Pinning Force ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Ripening Rate ◽  
Grain Growth Behavior ◽  
Nitride Precipitation

In order to investigate the effects of Nb carbo-nitride precipitation conditions on abnormal grain growth behavior during high temperature carburizing, size of Nb carbo-nitride precipitates was controlled by precipitation treatment at 1173-1273K for 0.6-54ks, and the specimens were quasi-carburized at 1323K. Abnormal grain growth was enhanced when the size of Nb precipitates was fine or coarse, so there is a suitable size range in Nb precipitates to suppress abnormal grain growth. The reason why abnormal grain growth was enhanced is the lack of pinning force as the conventional theory proposed by Hillert or Gladman; however, it cannot be explained by this theory that small precipitates promote abnormal grain growth. It is considered that Ostwald ripening rate of precipitates is also an important factor in controlling abnormal grain growth in addition to the amount and size of precipitates and austenite grain size, which were parameters in the Gladman‘s theory on abnormal grain growth behavior.

scholarly journals Precipitation Criterion for Inhibiting Austenite Grain Coarsening during Carburization of Al-Containing 20Cr Gear Steels

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 504
Author(s):  
Huasong Liu ◽  
Yannan Dong ◽  
Hongguang Zheng ◽  
Xiangchun Liu ◽  
Peng Lan ◽  
...  
Keyword(s):  
Grain Growth ◽  
Abnormal Grain Growth ◽  
Grain Structure ◽  
Pinning Force ◽  
Grain Coarsening ◽  
Zener Pinning ◽  
Austenite Grain ◽  
Composition Optimization ◽  
Gear Steels ◽  
Grain Growth Behavior

AlN precipitates are frequently adopted to pin the austenite grain boundaries for the high-temperature carburization of special gear steels. For these steels, the grain coarsening criterion in the carburizing process is required when encountering the composition optimization for the crack-sensitive steels. In this work, the quantitative influence of the Al and N content on the grain size after carburization is studied through pseudocarburizing experiments based on 20Cr steel. According to the grain structure feature and the kinetic theory, the abnormal grain growth is demonstrated as the mode of austenite grain coarsening in carburization. The AlN precipitate, which provides the dominant pinning force, is ripened in this process and the particle size can be estimated by the Lifshitz−Slyosov−Wagner theory. Both the mass fraction and the pinning strength of AlN precipitate show significant influence on the grain growth behavior with the critical values indicating the grain coarsening. These criteria correspond to the conditions of abnormal grain growth when bearing the Zener pinning, which has been analyzed by the multiple phase-field simulation. Accordingly, the models to predict the austenite grain coarsening in carburization were constructed. The prediction is validated by the additional experiments, resulting in accuracies of 92% and 75% for the two models, respectively. Finally, one of the models is applied to optimize the Al and N contents of commercial steel.

Thermal Simulation Study of CGHAZ Austenite Grain Growth Behavior of X80 Pipeline Steel

2014 ◽  
Vol 941-944 ◽  
pp. 146-149
Author(s):  
Xiang Dong Huo ◽  
Feng Dong ◽  
Lie Jun Li
Keyword(s):  
Grain Growth ◽  
Ostwald Ripening ◽  
Pipeline Steel ◽  
Welding Process ◽  
Thermal Simulation ◽  
X80 Pipeline Steel ◽  
Tem Analysis ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Grain Growth Behavior

The effect of peak temperature on austenite grain size was investigated by using thermal simulation and OM, TEM analysis. Grains grow slowly below 1250°C, and dramatically grow up as the temperature exceeds 1350°C. The primary precipitates in X80 pipeline steel are TiN and NbC, TiN particles cannot absolutely dissolve in steel during holding for 2s at 1300°C.Although TiN particles exist in steel, they cannot hinder grain growth of CGHAZ during welding process. The phenomenon can be explained by Ostwald Ripening mechanism.

Effect of Nb and V on Austenite Grain Growth Behavior of the Cr-Mo-V Steel for Brake Discs

2018 ◽  
Vol 37 (9-10) ◽  
pp. 899-907
Author(s):  
Dan Wu ◽  
Fuming Wang ◽  
Jin Cheng ◽  
Changrong Li
Keyword(s):  
Grain Growth ◽  
Bearing Steel ◽  
Growth Behavior ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Transmission Electron ◽  
Brake Discs ◽  
Rapid Dissolution ◽  
Grain Growth Behavior ◽  
Austenite Grain Growth

AbstractIn order to improve the performance of the steel for brake discs, including strength, toughness and thermal fatigue resistance, Nb and V are added to the steel. The effect of Nb and V on austenite grain growth behavior of the Cr-Mo-V steel for brake discs was studied by analyzing the phase equilibria as well as the microstructures. The precipitation behaviors of precipitates were also investigated based on transmission electron microscopy and energy-dispersive spectroscopy. The results showed that V-rich M8C7 and NbC particles existed at the experimental temperatures. The abnormal grain growth in Nb-free steels was affected by the partial dissolution and coarsening of M8C7 particles. With increasing V content, the grains were refined, but the mixed grain phenomenon became more serious. There were many small NbC particles in Nb-bearing steel, so the grains were effectively refined. Furthermore, a prediction model, which calculates the austenite grain size considering precipitate pinning effect, was established, and the model was well consistent with the actual situation in the Nb-bearing steel up to 1,100 °C. The grains of the Nb-free steels were sensitive to the increments of temperature and time due to the rapid dissolution or coarsening of M8C7 particles.

scholarly journals Effect of Cold-Deformation on Austenite Grain Growth Behavior in Solution-Treated Low Alloy Steel

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1004 ◽  
Author(s):  
Xianguang Zhang ◽  
Kiyotaka Matsuura ◽  
Munekazu Ohno
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Grain Growth ◽  
Cold Deformation ◽  
Growth Behavior ◽  
Low Alloy Steel ◽  
Solution Treated ◽  
Austenite Grain ◽  
Grain Growth Behavior ◽  
Austenite Grain Growth

The occurrence of abnormal grain growth (AGG) of austenite during annealing is a serious problem in steels with carbide and/or nitride particles, which should be avoided from a viewpoint of mechanical properties. The effects of cold deformation prior to annealing on the occurrence of AGG have been investigated. It was found that the temperature range of the occurrence of AGG is shifted toward a low temperature region by cold deformation, and that the shift increases with the increase of the reduction ratio. The lowered AGG occurrence temperature is attributed to the fine and near-equilibrium AlN particles that are precipitated in the cold-deformed steel, which is readily dissolved during annealing. In contrast, coarse and non-equilibrium AlN particles precipitated in the undeformed steel, which is resistant to dissolution during annealing.

scholarly journals Austenite Grain Growth Behavior of AISI 4140 Alloy Steel

2013 ◽  
Vol 5 ◽  
pp. 762890 ◽  
Author(s):  
Lin Wang ◽  
Dongsheng Qian ◽  
Jun Guo ◽  
Yan Pan
Keyword(s):  
Grain Growth ◽  
Alloy Steel ◽  
Growth Behavior ◽  
Austenite Grain ◽  
Aisi 4140 ◽  
Grain Growth Behavior ◽  
Austenite Grain Growth
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