摘要
This paper reports the effect of cooling rate on the microstructure and hardness of a kind of medium carbon steel microalloyed with two levels of V content （0.15% and 0.28%） after hot deformation by using single compression tests on a Gleeble-3800 thermal simulator. The results show that cooling rate has a significant effect on the microstructure and hardness of the tested steels. Both the fraction of pearlite and hardness increase with increasing cooling rate, whereas a further increase of the cooling rate above a critical value promotes the formation of acicular ferrite （AF）, and thus leads to a decrease of hardness mainly owing to the decrease of pearlite fraction and replacing it by AF and the less effective precipita- tion strengthening. Increasing V content results in a significant increase of hardness, and this tendency enhances with increasing cooling rate until the formation of AF. Furthermore, increasing V content also significantly enhances the formation of AF structure at a lower cooling rate. The results also suggest that by controlling microstructure, especially the precipitation of fine V（C,N） particles through adjusting post- forging cooling, the strengthening and gradient function in one hot-forging part could be obtained.
This paper reports the effect of cooling rate on the microstructure and hardness of a kind of medium carbon steel microalloyed with two levels of V content （0.15% and 0.28%） after hot deformation by using single compression tests on a Gleeble-3800 thermal simulator. The results show that cooling rate has a significant effect on the microstructure and hardness of the tested steels. Both the fraction of pearlite and hardness increase with increasing cooling rate, whereas a further increase of the cooling rate above a critical value promotes the formation of acicular ferrite （AF）, and thus leads to a decrease of hardness mainly owing to the decrease of pearlite fraction and replacing it by AF and the less effective precipita- tion strengthening. Increasing V content results in a significant increase of hardness, and this tendency enhances with increasing cooling rate until the formation of AF. Furthermore, increasing V content also significantly enhances the formation of AF structure at a lower cooling rate. The results also suggest that by controlling microstructure, especially the precipitation of fine V（C,N） particles through adjusting post- forging cooling, the strengthening and gradient function in one hot-forging part could be obtained.
基金
financially supported by the National HighTechnology Research&Development Program of China(No.2013AA031605)
