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The Influence of Hot Charging Conditions on Microstructure and Precipitation of High Strength Nb–Ti Complex Microalloyed Steels
Author(s) -
Luo Yanzhao,
Zhang Jiongming,
Xiao Chao,
Song Wei,
Wang Shunxi
Publication year - 2012
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.201200111
Subject(s) - microstructure , materials science , bainite , microalloyed steel , transmission electron microscopy , lath , metallurgy , precipitation , ferrite (magnet) , grain boundary , composite material , martensite , austenite , nanotechnology , physics , meteorology
A comprehensive microstructure analyses were conducted for hot charging processed Nb, Ti microalloyed steel, especially focusing on the evolution of microstructure and precipitation behavior. Hot charging process was simulated in the laboratory in the current research. Precipitation and microstructure in Ti–Nb microalloyed HSLA steels were investigated in different hot charging temperature conditions using transmission electron microscope (TEM), optical microscopy, analytical transmission electron microscopy, and energy dispersive spectroscopy (EDS). The results showed that the microstructure consists of fine and homogeneous lath bainite at 1000°C, lath bainite and granular bainite at 900°C. As the hot charging temperature decreased, there appeared a small fraction of proeutectoid ferrite along grain boundary at 800°C. The grain sizes in hot charging are coarse compared with that of 700°C due to the phase transformation didn't occur. The chemical composition of complex carbonitrides changes from Ti rich to Ti–Nb uniform with decreasing temperature.