Process,Microstructure and Properties of Thick X80 Pipeline Steel Produced by Hot Continuous Rolling

The microstructure, precipitates and mechanical properties of thick X80 pipeline steel produced by hot continuous rolling of Masteel were studied.The result shows that through reasonable composition design and rolling process, the microstructures of thick X80 pipeline steel produced by hot continuous rolling are uniform and reasonable, its precipitates are fine dispersion.The precipitates consist of Nb, V, Ti, they can be divided into two types based on their shape, one is (Ti、Nb) (C、N) in which Ti plays the main role, its main function is preventing austenite growth;another one is (Nb、Ti) C in which Nb plays the main role, its main function is precipitation strength.Under the circumstance of making full use of fine-grained strength, dislocation and sub-boundary strength, precipitation strength, the thick X80 pipeline steel has excellent mechanical properties:The yield strength is 580 MPa, the ratio of yield to strength is proper;the impact energy and shear area are respectively 290 J, 100% at-20 ℃, the DWTT shear area is 100% at-15 ℃.All the performance meet the demand of the second West-East Gas Transmission.