Institute for Structure Materials

Beijing, China

Institute for Structure Materials

Beijing, China

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Tan F.-L.,Kunming University of Science and Technology | Tan F.-L.,Institute for Structure Materials | Liu Q.-Y.,Institute for Structure Materials | Jia S.-J.,Institute for Structure Materials | Lei T.,Kunming Metallurgy College
Journal of Iron and Steel Research | Year: 2012

The CCT behaviors of two bearing Nb polygonal ferrite-bainite high strength and high-deformability pipeline steels were studied in undeformed condition, The static CCT curves were constructed. The static CCT curves, microstructures and microhardness of two experimental steels were compared. It was found that micro-structures of these steels contain polygonal ferrite, pearlite, bainite as cooling rate from 0. 027 8 to 42. 5 °C · s-1; Addition of Nb in the steel retards polygonal ferrite and granular bainite transformation, suppresses ferrite growth and refine ferrite grain, makes transformation line of bainite right shift, narrows the range of cooling rate of ferrite transformation, raises start temperature of ferrite and banite transformation) ferrite transformation zone is narrowed and the bainite transformation zone is expanded with increasing of Nb.


Tan F.-L.,Kunming University of Science and Technology | Tan F.-L.,Institute for Structure Materials | Liu Q.-Y.,Institute for Structure Materials | Lei T.,Kunming Metallurgy College | And 3 more authors.
Journal of Iron and Steel Research International | Year: 2013

In order to ensure the safety of long-distance oil and natural gas transmission pipeline installed in seismic and/or permafrost region, high strength pipeline steel with excellent deformability has been developed. The ferrite and bainite dual phase pipeline steel is a very important kind of high deformability pipeline steel. Polygonal ferrite is a key microstructure in ferrite and bainite dual phase deformability pipeline steel. Ferrite evolution during isothermal process at 700 °C after 50% deformation at 800 °C was conducted by using a Gleeble-3800 thermal simulator, and microstructure was characterized by using an optical microscope, a scanning electron microscope and a transmission electron microscope. There are two types of ferrite, ferrite with high density dislocation and ferrite with a little dislocation. There is about 7% (volume percent) deformation induced ferrite (DIF) for compression of 50% at 800 °C and strain rate of 1 s-1. During the isothermal process at 700 °C, with the holding time increasing, ferrite volume percent, ferrite grain number and average ferrite grain size increase. As the holding time is prolonged, dislocation recovery occurs in DIF. There are secondary phases in ferrite when the holding time is too long, and secondary phases and dislocation formation in dislocation pinning. © 2013 Central Iron and Steel Research Institute.


Pei Y.-H.,Institute for Structure Materials | Chen Q.-A.,Institute for Structure Materials | Tang G.-B.,Institute for Structure Materials | Peng Y.,Institute for Structure Materials
Kang T'ieh/Iron and Steel (Peking) | Year: 2010

The high temperature microstructure of grain oriented silicon steel at 850-1300°C was studied by using optical microscope and scanning electron microscope. The influences of alloy elements and temperature on austenite volume fraction and the distribution of alloy elements in austenite and ferrite were investigated. The results show that the temperature range for high temperature microstructure with maximum volume fraction of austenite phase in the grain oriented silicon steel of different chemical compositions is about 1100-1200°C, and the temperature for the maximum volume fraction of austenite phase increases with the increase of the content of austenite-stabilizing elements. There is an approximate linear relationship between the carbon content and austenite volume fraction in grain oriented silicon steel at high temperature.

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