Prediction On Microstructure And Properties Of Hot-rolling Pipeline Steel

Along with the incessant development of the world economy, petroleum and gas pipeline transportation get more and more people's attention. Composition of Pipeline steel's microstructure has important influence to material service life and performance. In order to save manpower and physical resource, technology of microstructure and properties forecast has good application.The establishment of microstructure and properties forecast model is based on metallurgical physics theory on hot rolling process. Including austenitic recrystallization model, austenitic to ferrite phase transition model, ferrite grain size forecast model and microstructure, mechanical properties of corresponding relation model.Influence of deformation process on austenitic recrystallization was researched. Through the recrystallization kinetics theory, established mathematical model of austenite static and dynamic recrystallization on hot rolling process and established austenite grain model. With the increase of the deformation, the dynamic recrystallization scores are constantly increasing. With the extension of heat preservation time after deformation, static recrystallization scores increase continuously. Deformation determines recrystallization score when it has same deformation temperature and heat preservation time. Deformation in the materials produced more distortion and can increase the recrystallization driving. Only deformation is higher the critical deformation can the dynamic recrystallization be occurred. Deformation temperature and the deformation velocity will affect critical deformation, and thereby affect the dynamic recrystallization.Deformation, deformation temperature, deformation velocity and breaks after deformation have important influence on recrystallization grains grown. Small deformation in high temperature is easy to cause incomplete recrystallization and bulky and uneven grain. It is hard to eliminate them in subsequent rolling process.According to the above mathematical model, it can calculate final ferrite grain size after rolling cooling. As the increase of cooling speed, the amount of polygon ferrite reduces and the amount of acicular ferrite increases. Grain size is further refinement. The final microstructure and the degree of ferrite grain refinement determine the mechanics properties of steel.Computer program has been compiled to simulate austenite recrystallization scores, recrystallization grain size, ferrite grain size and the relative content and final mechanical properties. Simulation and experimental results are almost the same, and the model can be used to guide practical production.