Research On Flow Stress And Microstructure And Properties Of X80Pipeline Steel During Dual Phase Deformation

Pipeline transportation has the characteristics of economic, safe and uninterrupted.X80pipeline steel is the preferred steel in pipeline engineering of natural gas, petroleum,coal slurry and so on. The analysis and research of the X80pipeline steel has become oneof hot topics in the study and production of the pipeline steel at present. At the same time,our country’s steel industry under the glory of high productivity, high pollution, highenergy consumption, unreasonable product structure, low quality are hindering thedevelopment of Chinese iron and steel industry and leading to a slow growth, low profitcondition. Thus, searching for a low energy consumption, low cost production mode toenhance competitiveness is always a development direction of the iron and steel industry.Reducing the rolling temperature as one of the ‘Energy Saving and Pollution Reduction’production mode is always the focus in recent research.This paper takes X80pipeline steel as the research object, and investigates thecharacteristics of flow stress of X80pipeline steel in dual phase region of deformation,establishes the mathematical model of flow stress in dual phase region deformation. At thesame time, the microstructure and properties of materials after the deformation of the dualphase region is studied in this paper, finally provides reference for X80pipeline steelrolled in the dual phase region.First of all, the phase equilibrium temperature model, phase incubation period model,actual transformation temperature model, isothermal transformation kinetics model andcontinuous cooling transformation model was established by KRC model, Lange theoryand Cahn theory. By the calculation, the phase equilibrium temperature is868℃, and thephase transition temperature is827℃.Next, the thermal expansion experiment, deformation in dual phase regionexperiment and deformation in austenite zone experiment are carried out on Gleeble-3500thermo-mechanical simulator. The accuracy of thermodynamics of phase transformationand phase transformation kinetics is verified. At the same time, the influential factor ofphase transition on flow stress is introduced after analyze the characteristics of flow stress in dual phase deformation. And then, the phase transformation kinetics model is combinedto establish a flow stress model in dual phase deformation. The calculated values arecompared with measured values, shows that the model has a high precision, and applicableto the dual phase deformation.At last, based on the hardness test and micro tensile test on the specimens whichdeformed in dual phase, combing with microstructure and the tensile fracture morphology,analyzes the characteristics of microstructure and mechanical properties of deformation indual phase region. Finally, this paper put forward the optimal process route in dual phasedeformation. Compared with X80conventional deformation in austenite, demonstrates thefeasibility of deformation in dual phase region.