Effect of fast cooling process on microstructure and toughness of heat affected zone in high strength pipeline steel X120

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.

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New bainite kinetics of high strength low alloy steel in fast cooling process

Journal of Iron and Steel Research International ◽

10.1016/s1006-706x(17)30032-8 ◽

2017 ◽

Vol 24 (2) ◽

pp. 229-233 ◽

Cited By ~ 3

Author(s):

Xuan-wei Lei ◽

Ji-hua Huang ◽

Shu-hai Chen ◽

Xing-ke Zhao

Keyword(s):

Alloy Steel ◽

High Strength ◽

Low Alloy Steel ◽

Cooling Process ◽

Fast Cooling ◽

Kinetics Of

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Influence of Cooling Rate on the Microstructures and Properties of Q550

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.117-119.1705 ◽

2011 ◽

Vol 117-119 ◽

pp. 1705-1707

Author(s):

Fan Li ◽

Hai Long Yi ◽

Zhen Yu Liu ◽

Guo Dong Wang

Keyword(s):

High Strength ◽

Strengthening Mechanisms ◽

Cooling Process ◽

Bainite Transformation ◽

Good Strength ◽

Ultra Fast Cooling ◽

Fast Cooling ◽

Cooling Technology ◽

Conventional Cooling ◽

Strength And Toughness

A Q550 high strength steel was selected at two different cooling rates through ultra-fast cooling process, and its microstructures and strengthening mechanisms were analyzed. The results show the bainite transformation temperature of the steel decreased with the increasing of cooling rate.The ultra-fast cooling process can improve the performance of Q550 compared with the conventional cooling process, and the yield strength, tensile strength and elongation are 600MPa, 755MPa and 19%, and - 20 °Cimpact energy is 253J, and good strength and toughness are obtained under ultra-fast cooling process. The microstructure of this steel is bainite and good strength and toughness are caused by the refinement of bainite and fine precipitates. Ultra-fast cooling technology improves the strength and toughness of this steel effectively.

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Influence of Cooling Rate on the Microstructures and Properties of a Nb-Ti-Mo Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.14 ◽

2012 ◽

Vol 152-154 ◽

pp. 14-17

Author(s):

Hai Long Yi ◽

Yang Xu ◽

Zhen Yu Liu ◽

Guo Dong Wang

Keyword(s):

Tensile Strength ◽

Cooling Rate ◽

High Strength ◽

Strengthening Mechanisms ◽

Micro Hardness ◽

Cooling Process ◽

Ultra Fast Cooling ◽

Fast Cooling ◽

Cooling Technology ◽

Strength And Toughness

A Nb-Ti-Mo high strength steel was selected at two different cooling rates through ultra-fast cooling process, and its microstructures and strengthening mechanisms were analyzed. The results show the size of ferrite was decreased and the amount of bainite and micro-hardness were increased with increasing of cooling rate through thermal simulation. The UFC technology can improve the yield and tensile strength 25MPa and 35MPa, respectively, compared with conventional TMCP. The microstructure of this steel is mainly ferrite and good strength and toughness are caused by the refinement of ferrite and fine precipitates. Ultra-fast cooling technology improves the strength and toughness of this steel effectively.

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