Study on Continuous Cooling Phase Transition of 12Cr1MoV Pearlite Heat-resistant Steel

Abstract

The continuous cooling transformation of 12Cr1MoV perlitic heat-resistant steel was studied by means of ther⁃ mal 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 fer⁃ rite， 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.

Keywords

• 12cr1mov steel； cooling rate； cct curve； microstructure