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The Effect of Initial Microstructure on Microstructure Evolution and Mechanical Properties of Intercritically Rolled Low‐Carbon Microalloyed Steel Plates
Author(s) -
Shen Xin-jun,
Li De-zhi,
Chen Jun,
Tang Shuai,
Wang Guo-dong
Publication year - 2019
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.201900237
Subject(s) - microstructure , materials science , charpy impact test , ferrite (magnet) , microalloyed steel , toughness , bainite , metallurgy , grain boundary , recrystallization (geology) , composite material , austenite , geology , paleontology
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.