The Effect of Initial Microstructure on Microstructure Evolution and Mechanical Properties of Intercritically Rolled Low‐Carbon Microalloyed Steel Plates

Abstract

Steel plates rolled in the intercritical region have ultrafine and elongated‐grained microstructures, and excellent toughness. The effect of the initial microstructure on microstructure evolution and the mechanical properties of intercritically rolled (IR) low‐carbon microalloyed steel plates is investigated herein. Coarse‐grained initial microstructure mainly containing lath bainite and fine‐grained initial microstructure mainly containing quasi‐polygonal ferrite are produced by austenitization treatments at different temperatures. The results show that the coarse‐grained initial microstructure restrains continuous dynamic recrystallization during intercritical rolling, which leads to a less fraction of high‐angle grain boundaries (HAGBs). However, initial microstructure has little influence on the average size of ferrite grains surrounded by HAGBs. Moreover, coarse‐grained initial microstructure results in a relatively higher strength improving about 15 MPa due to the lower fraction of HAGBs. Fine‐grained initial microstructure is beneficial to the Charpy impact toughness such that the upper shelf energy is improved from 108 to 118 J, and low‐temperature toughness is also enhanced. However, the effect of the initial microstructure on the microstructure and mechanical properties of IR rolled steel plates is not great, which indicates that coarse‐grained initial microstructure can also be used to develop this kind of steel plates with excellent toughness.

The Role of Splitting Phenomenon under Fracture of Low-Carbon Microalloyed X80 Pipeline Steels during Multiple Charpy Impact Tests

“…The investigation of low-temperature impact fracture appearances in thermo-mechanically controlled processed steels shows that, along with ductile dimpled regions and splits, brittle tilted fracture regions could appear [21][22][23][24]. The latter phenomenon is beyond the scope of this study.…”

The Effect of Cooling Rate on the Microstructure Evolution and Mechanical Properties of Ti-Microalloyed Steel Plates

“…Besides microalloying, the thermomechanical controlled processing (TCMP) technique has also been proposed and studied extensively. Wang and his group at Northeastern University studied the effect of TMCP parameters, including hot-rolling temperature [2,3], cooling rate [3], and finish cooling temperature [4][5][6], on the mechanical properties of medium thickness microalloyed steel plates. Nishioka published a review describing the metallurgical aspects of the microalloying in steel, and discussing the advantages of TMCP, for example, in terms of weldability, which is reduced upon alloying [7].…”

“…1 S represents the surface of the steel plate 2. M represents the center thickness of the steel plate.…”

Synergistic Investigations of Post‐Deformation Annealing and Initial Microstructure on the Mechanical Properties of High Strength Low Alloy (HSLA)‐100 Steel

“…[17] The initial microstructure not only has an effective role on the mechanical properties but also plays a crucial role in recrystallization kinetics. The effects of tempering temperature, [18,19] rolling reduction, [20,21] microalloying elements, [22] tempering time, [23,24] heating rate, [25] initial microstructure, [26][27][28] and other deformation modes [29] have been studied so far, and the main focus has been on the obtained grain sizes. Indeed, the aforementioned studies investigated the factors that influence the recrystallization kinetics.…”