Microstructure and Deformation Characteristics of X80 High Deformability Pipeline Steel

2011 ◽  
Vol 299-300 ◽  
pp. 323-327 ◽  
Author(s):  
De Liang Meng ◽  
Yong Lin Kang ◽  
Shou Yong An ◽  
Dian Xiu Xia
Keyword(s):  
Pipeline Steel ◽  
Uniform Elongation ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
Lower Yield ◽  
On Line ◽  
Line Process ◽  
Three Stages ◽  
Two Stages ◽  
High Deformability

Two kinds of X80 high deformability pipeline steels have been processed by applying two-stage cooling process (TSC) and heat treatment on-line process (HOP). The microstructure of TSC steel and HOP steel are polygonal ferrite (PF) + quasi-polygonal ferrite (QF) + granular bainite (GB) multiphase and QF + GB+ martensite-austenite (M/A) multiphase respectively. In HOP steel, the volume of M/A is much more and the size is much larger than that in TSC steel. Some degenerated M/A constituents are also observed in HOP steel. The HOP steel has shown higher tensile strength, lower yield ratio and lower uniform elongation than TSC steel. The strain-nI (instantaneous n-value) curve of HOP steel could be divided into two stages and the TSC’s could be separated to three stages.

Microstructure and Mechanical Properties of X80/X100 High Deformability Pipeline Steel

2011 ◽  
Vol 399-401 ◽  
pp. 139-143
Author(s):  
Dian Xiu Xia ◽  
De Liang Meng ◽  
Shou Yong An ◽  
Yong Lin Kang
Keyword(s):  
Pipeline Steel ◽  
Large Strain ◽  
High Strength ◽  
Longitudinal Direction ◽  
Granular Bainite ◽  
Dual Phase ◽  
Cooling Process ◽  
Bainite Structure ◽  
Lath Bainite ◽  
High Deformability

In the present study, X80 and X100 grade high deformability pipeline steels have been processed by using TMCP and followed two-stage cooling process. The microstructures of the X80HD (HD, high deformability) and X100HD steels were both characterized by ferrite-bainite dual phase. The grains sizes of ferrite were mostly less than 5μm and the volume fractions were about 20~25% in X80HD and 10~15% in X100HD steel. The bainite structure in X80HD steel was granular bainite (GB); while in X100HD steel large amounts of lath bainite (LB) were also formed besides GB, and bainite grains were much finer. Ferrite-bainite dual phase microstructure has large strain hardenability that resulting high strength and high deformability combination. Both the steels exhibit high strength/toughness in transverse direction and high deformability in longitudinal direction. The X100HD steel with more volume of LB and less volume of PF has higher strength but lower deformability than that of X80HD steel.

SH-CCT of High-Strain Pipeline Steel X80

2012 ◽  
Vol 472-475 ◽  
pp. 1179-1182 ◽  
Author(s):  
Mei Juan Hu ◽  
Peng Wang ◽  
Wei Ping Lin ◽  
Xiao Yan Wang ◽  
Ling Kang Ji
Keyword(s):  
Phase Transformation ◽  
High Strain ◽  
Pipeline Steel ◽  
Hardness Measurement ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
Coarse Grain ◽  
Microstructure Observation ◽  
Transformation Curve ◽  
Gleeble 3500

Simulated heat affected zone continuous cooling transformation curve was measured by means of Gleeble 3500 thermal simulator. According to the results of microstructure observation and hardness measurement, influence of cooling rates on the microstructure and hardness in coarse grain zone of high-strain pipeline steel X80 was studied. The results illustrated that softening in coarse grain zone was ubiquitous problem for high-strain pipeline steel X80. There were mainly four types of phase transformation in coarse grain zone of high-strain pipeline steel X80. Polygonal ferrite(PF) and a small quantity of pearlite, granular bainite, bath bainite and bath martensite were obtained after different cooling time.

Microstructure and Mechanical Properties Analysis of X70 Pipeline Steel with Polygonal Ferrite Plus Granular Bainite Microstructure

2012 ◽  
Vol 161 ◽  
pp. 67-71 ◽  
Author(s):  
Zhan Zhan Zhang ◽  
Xiu Rong Zuo ◽  
Yue Yue Hu ◽  
Ru Tao Li ◽  
Zhi Ming Zhang
Keyword(s):  
Mechanical Properties ◽  
Pipeline Steel ◽  
High Strength ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
X70 Pipeline Steel ◽  
Microstructure And Mechanical Properties ◽  
Drop Weight ◽  
Bainite Microstructure ◽  
Strength And Toughness

Microstructure and mechanical properties of X70 pipeline steel with polygonal ferrite plus granular bainite were characterized using tensile tests, Charpy V-notch impact tests, drop weight tear tests, hardness tests and scanning electron microscopy. The results of experiment indicated that X70 pipeline steel with polygonal ferrite plus granular bainite showed an excellent combination of high strength and toughness. The base metal with polygonal ferrite plus granular bainite microstructure exhibited perfect mechanical properties in terms of the transverse yield ratio of 0.81, elongation of 46%, an impact energy of 335 J at -10 °C and a shear area of 90% at 0 °C in the drop weight tear test. The heat affected zone contained coarse grain zone and fine grain zone, which exhibited good low temperature toughness of 216 J at -10 °C. The weld metal primarily consisted of intragranularly nucleated acicular ferrites which led to the high strength and toughness.

Phase Transformation Behaviors of Nb-V-Ti Microalloyed Pipeline Steel X70

2013 ◽  
Vol 750-752 ◽  
pp. 380-384
Author(s):  
Yu Hui Wang ◽  
Ya Nan Zheng ◽  
Tian Sheng Wang ◽  
Bo Liao ◽  
Li Gang Liu
Keyword(s):  
Phase Transformation ◽  
Pipeline Steel ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Continuous Cooling Transformation Diagrams ◽  
Transformation Diagrams

The CCT (continuous cooling transformation) diagrams of the Nb-V-Ti without Mo containing microalloyed pipeline steel X70 were investigated. The microstructures observed in continuous cooled specimens are composed of P (pearlite), PF (polygonal ferrite), QF (quasi-polygonal ferrite), and GF (granular bainite ferrite). At low cooling rates between 0.1°C/s and 1°C/s, the microstructure of the steel consisted of banded ferrite and pearlite but higher cooling rates suppressed its formation.

Phase Transformation and Properties under Different Quenching Mediums of a X120 Pipeline Steel

2010 ◽  
Vol 152-153 ◽  
pp. 408-412
Author(s):  
Min Zhou ◽  
Lin Xiu Du ◽  
Xiang Hua Liu ◽  
Kai Zhang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Pipeline Steel ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
Micro Hardness ◽  
Transmission Electron ◽  
Cooling Velocity ◽  
Scanning Electron

The microstructure, CVN toughness and micro-hardness of an X120 pipeline steel were investigated by metalloscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) etc. It showed that the microstructure evolved from lathe martensite, lathe bainite to granular bainite and polygonal ferrite, the size of M-A islands increased. With cooling velocity increasing, the CVN toughness at -20 was fluctuating, and reaching its peak in the steel cooled in oil had the best toughness, while the steel cooled in furnace was brittle at -20 . With cooling velocity decreasing, the micro-hardness of the steel decreased, whereas, the micro-hardness of the steel cooled in furnace increased slightly.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

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