Influence of Delay Accelerated Cooling on the Microstructure and Property of X100 Pipeline Steel

Relationship between microstructure and properties for X100 pipeline steel after delay accelerated cooling(DAC)was investigated through thermal simulation,mechanical property test and microscopic analysis method.The results show that(B+F)dual-phase microstructure can be obtained by DAC.With the increase of starting cooling temperature,the content of bainite increases and the content of ferrite decreases,leading to the increase of yield strength and the reduction of plasticity of the steel.When starting cooling temperature is 530℃,lower yield ratio,higher uniform elongation and higher strain hardening exponent of the steel can be achieved,which meet the technical requirements to high deformation pipeline steel. Bainite with fine lath and ferrite with high dislocation density can be acquired through DAC,which endow the steel with higher strength-toughness and good deformability.