The thickness of the steel plate of the X80 grade spiral welded pipe is not up to 18.4mm. It is necessary to study the alloy design, rolling and cooling process parameters and their effects on the microstructure and properties of pipeline steel.
Generally speaking, the physical metallurgical process and phenomena of the hot rolling process are different from those of the plate rolling. The design ideas and processes of the X80 hot rolled coil pipe steel also have their own characteristics. First of all, in order to ensure the low temperature impact toughness of DWTT performance, the content of C in 0.07% (mass fraction), however in the composition range, the change of C content requires understanding of the impact of yield strength; research shows that low C2Mn2Nb+ pipeline steel with Mo, can reduce the temperature change in temperature, low cooling speed are acicular ferrite and bainite, but it is necessary to determine the optimum content of Mo through the industrial rolling test and further clarify the role of Mo; of course, influence of hot rolling process on Microstructure and mechanical properties should also be revealed through the industrial test, finally obtain process factors affecting the microstructure and properties of high performance pipeline.
Increasing the content of C can affect the quantity and morphology of MA Island, and the small and dispersed MA island can be obtained by cooling control. In the low carbon range, the increase of C content is not the main cause of yield strength. Adding the mass fraction of 0.19% to, the strength of X80 can be achieved by adjusting the finishing process. In addition, the addition of Mo is beneficial to the dynamic recrystallization during the finishing process of Mo. Hot rolled plate finishing rolling temperature should be controlled at 960 DEG C, at the same time to control the amount of pressure, to prevent excessive strain accumulation, can prevent the occurrence of static and dynamic recrystallization, realize the steady accumulation of mean flow stress, ensure X80 strength, toughness and DWTT performance requirements.