The continuous cooling transformation of 12Cr1MoV perlitic heat-resistant steel was studied by means of thermal expansion tester, laser confocal microscope, microhardness tester and scanning electron microscope, the continuous cooling transformation (CCT) curve of experimental steel was drawn, and the effect of cooling rate on the microstructure evolution of phase transformation during cooling process was analyzed. The results show that four transition regions of ferrite, pearlite, bainite and martensite will appear in the CCT curves of 12Cr1MoV steel at the cooling rates between 0.5 ℃/s and 30 ℃/s. At the cooling rates between 0.5 ℃/s and 1 ℃/s, and the transformation products are composed of ferrite and pearlite. At the cooling rates between 1.5 ℃/s and 10 ℃/s, and the transition products are mainly composed of upper bainite and ferrite. At the cooling rates between 10 ℃/s and 20 ℃/s, and the transition products are mainly the mixed structure of upper bainite, lower bainite and martensite. At the cooling rate of 30 ℃/s, the transition product is mainly martensite. The transition structure of undercooled austenite appears upper bainite at the cooling rates between 1.5 ℃/s and 20 ℃/s. The appearance of upper bainite in the structure leads to a decrease in the mechanical properties of the steel, which is prone to crack formation and propagation. Based on the above research results, measures to reduce the cooling rate of 12Cr1MoV steel continuous casting billets and hot rolling lines are proposed to reduce the upper bainite structure The surface cracks of the bars are effectively controlled after adjustment.
Harada N , Takuma M , Tsujikawa M , et al . Effects of V addition on improvement of heat shock resistance and wear resistance of Ni-Cr-Mo cast steel brake disc [J]. Wear , 2013 , 302 ( 1-2 ): 1444 - 1452 .
Li Z Q , Han J M , Li W J , et al . Low cycle fatigue behavior of Cr-Mo-V low alloy steel used for railway brake discs [J]. Materials & Design (1980-2015), 2014 , 56 : 146 - 157 .
Azuma M , Fujita N , Takahashi M , et al . Modelling upper and lower bainite trasformation in steels [J]. ISIJ International , 2005 , 45 ( 2 ): 221 - 228 .
Enomoto M . Partition of carbon and alloying elements during the growth of ferrous bainite [J]. Scripta Materialia , 2002 , 47 ( 3 ): 145 - 149 .
Fang H S , Yang J B , Yang Z G , et al . The mechanism of bainite transformation in steels [J]. Scripta Materialia , 2002 , 47 ( 3 ): 157 - 162 .
Craven A J , He K , Garvie L A J , et al . Complex heterogeneous precipitation in titanium-niobium microalloyed Al-killed HSLA steels-I. (Ti, Nb)(C, N) particles [J]. Acta Materialia , 2000 , 48 ( 15 ): 3857 - 3868 .
Craven A J , He K , Garvie L A J , et al . Complex heterogeneous precipitation in titanium-niobium microalloyed Al-killed HSLA steels-II. Non-titanium based particles [J]. Acta Materialia , 2000 , 48 ( 15 ): 3869 - 3878 .
Pawlak K , Białobrzeska B , Konat Ł . The influence of austenitizing temperature on prior austenite grain size and resistance to abrasion wear of selected low-alloy boron steel [J]. Archives of Civil and Mechanical Engineering , 2016 , 16 ( 4 ): 913 - 926 .
Lee S J , Park J S , Lee Y K . Effect of austenite grain size on the transformation kinetics of upper and lower bainite in a low-alloy steel [J]. Scripta Materialia , 2008 , 59 ( 1 ): 87 - 90 .
徐洲 , 赵连城 . 金属固态相变原理 [M]. 北京 : 科学出版社 , 2004 .
Huang J , Xu Z . Effect of dynamically recrystallized austenite on the martensite start temperature of martensitic transformation [J]. Materials Science and Engineering: A , 2006 , 438-440 : 254 - 257 .
García-Junceda A , Capdevila C , Caballero F G , et al . Dependence of martensite start temperature on fine austenite grain size [J]. Scripta Materialia , 2008 , 58 ( 2 ): 134 - 137 .
Zhang C L , Cai D Y , Wang Y H , et al . Effects of deformation and Mo, Nb, V, Ti on continuous cooling transformation in Cu-P-Cr-Ni-Mo weathering steels [J]. Materials Characterization , 2008 , 59 ( 11 ): 1638 - 1642 .