正火过程中V--N微合金化钢的第二相行为

采用物理化学相分析、高分辨透射电镜等手段研究V-N微合金化钢在正火过程中第二相行为,并进行相应的理论计算,讨论该行为对材料性能产生的影响.正火加热保温过程中,V-N钢有约32.9%的V( C,N)未溶解,阻止奥氏体晶粒长大.在正火冷却过程中,未溶解的V( C,N)诱导晶内铁素体形核,细化铁素体晶粒,而溶解的V( C,N)重新析出,起到析出强化作用. V( C,N)析出相行为的变化导致材料力学性能的改变.与热轧态V-N钢相比,正火态V-N钢细晶强化贡献值增加31 MPa,而析出强化贡献值减少45 MPa.

Precipitation behavior of V--N microalloyed steel at the normalizing process

The precipitation behavior of V-N microalloyed steel at the normalizing process was studied by physicochemical phase analysis and high resolution transmission electron microscopy. The effect of this precipitation behavior on the mechanical properties of the steel was discussed by theoretical calculations. At soaking of the normalizing process, 32. 9% of V(C,N) precipitations keep undissolved into austenite, and they prevent austenite from growing up. At the subsequent cooling process, the undissolved V( C,N) precipitations induce intra-granular ferrite nucleating, which can refine ferrite grains; besides, the dissolved V( C,N) precipitations re-precipitate and play the role of precipitation strengthening. Compared with the hot-rolled steel, the normalized steel gains a 31 MPa increment in grain-refined strengthening but a 45 MPa decrease in precipitation strengthening.