Yang Feifei,Xu Haiwei,Hao Gen,et al.Effect of AlN and Zr Microalloying on Thermoplasticity and Grain Size of Carburized Gear Steel[J].Special Steel,2023,44(04):94-101.
Yang Feifei,Xu Haiwei,Hao Gen,et al.Effect of AlN and Zr Microalloying on Thermoplasticity and Grain Size of Carburized Gear Steel[J].Special Steel,2023,44(04):94-101. DOI: 10.20057/j.1003-8620.2023-00020.
Effect of AlN and Zr Microalloying on Thermoplasticity and Grain Size of Carburized Gear Steel
In the carburizing process of gear steel, AlN is often used to control the growth of austenite grains. however, the large amount of AlN precipitation will deteriorate its thermoplasticity and crack sensitivity, and AlN remelts during high temperature carburizing at 1 050 ℃, the pinning effect is weakened . By designing steel grades at different AlN concentration product ([%Al][%N]) and Zr microalloying, to study the effect of AlN and Zr microalloying on the growing behavior of thermoplastic and carburization grains of 20 Cr gear steel. The results show that: for 20Cr series gear steel, increasing the AlN concentration product will deteriorate the hot ductility and make the plastic trough (750-900 ℃) to move to the high temperature zone. However, the low AlN concentration product or Ostwald ripening phenomenon during carburizing process will weaken the grain boundary pinning effect of AlN. Therefore, it is more appropriate to control [%Al][%N] in steel at the lower limit between 2.9×10
-4
-5.1×10
-4
. In addition, the Zr in gear steel will preferentially precipitate coarse ZrN during the solidification process, resulting in a decrease in the amount of AlN precipitation and weakening the effect of pinning grain boundaries. Therefore, it is necessary to control the content of N elements to avoid the influence of coarse high temperature precipitation phase on AlN.
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