YU Hao
,
KANG Yonglin
,
ZHAO Zhengzhi
,
SUN Hao
钢铁研究学报(英文版)
The morphology of manganese sulfide formed during thin slab continuous casting process in lowcarbon steel produced by compact strip production (CSP) technique was investigated. Using transmission electron microscopy analysis, it was seen that a majority of manganese sulfides precipitated at austenite grain boundaries, the morphologies of which were spherical or close to the spherical shape and the size of MnS precipitates ranged from 30 nm to 100 nm. A mathematical model of the manganese sulfide precipitation in this process was developed based on classical nucleation theory. Under the given conditions, the starting and finishing precipitation temperatures of MnS in the continuous casting thin slab of the studied lowcarbon steel are 1 189 ℃ and 1 171 ℃, respectively, and the average diameter of MnS precipitates is about 48 nm within this precipitation temperature range. The influences of chemical components and thermomechanical processing conditions on the precipitation behavior of MnS in the same process were also discussed.
关键词:
morphology;thin slab continuous casting;precipitation kinetics;compact strip production;TEM
ZHANG Jiming
,
SUN Weihua
,
SUN Hao
钢铁研究学报(英文版)
A new ultrahigh strength pipeline steel with high yield strength and high impact toughness was fabricated in this work, and mechanical properties and microstructure of the steel were investigated in this paper. The steel exhibited outstanding mechanical properties with yield strength levels of up to 951MPa and Tensile strength levels up to 1023MPa. The sharp notch-toughness with absorbed energy values of 227J/cm2 at Temperatures of -30℃ and %shear of up to 95% in drop weight tear test (DWTT) at temperatures of -20℃ were achieved. It was found that microstructure of the steel comprises a majority of low carbon lath bainite with different sublaths and sub-sublaths, meanwhile there is a high density of dislocation between laths and the dispersed film-like martensite-austenite (M-A) constituents. Most of the precipitates in this steel are duplex type containing Nb and Ti with characterized morphology of cap. The precipitation size is a few to a few tens nanometers.
关键词:
pipeline steel;mechanical properties;lath bainite;precipitate
