The axial single-pass high temperature compression test of a hot-rolled extra-large heavy H-beam steel continuous casting billet (Q420 steel) under different deformation conditions through the Gleeble-1500D thermomech...The axial single-pass high temperature compression test of a hot-rolled extra-large heavy H-beam steel continuous casting billet (Q420 steel) under different deformation conditions through the Gleeble-1500D thermomechanical simulator was carried out. The modified Johnson–Cook model and the Arrhenius model based on strain-compensated of Q420 steel were established. The latter can more accurately reflect the flow behavior of Q420 steel. For the simulation of thermal compression, dynamic recrystallization (DRX) correlation models were developed and imported into DEFORM-3D software. According to simulation results, high temperatures and low strain rates are conducive to DRX. Due to the uneven distribution of equivalent strain and temperature in different parts of the same section, DRX volume fraction and grain size are unevenly distributed. At the center, the DRX volume fraction is the largest and the grain size is the smallest. The upper and lower edges are vice versa, and the left and right edges are centered. Optical microscopy and electron backscatter diffraction characterization methods were used to study the hot compression microstructure under different deformation conditions. As the deformation amount increases, complete DRX is gradually reached. The original austenite grain gradually becomes smaller. Local average misorientation decreases with the progression of DRX but increases with the amount of deformation after completion of DRX. As the temperature increases and the rate decreases, low angle grain boundaries and medium angle grain boundaries gradually decrease, and high angle grain boundaries gradually increase, indicating that dislocation decreases gradually, DRX grains increase gradually, and martensitic multilayer structure is obvious. As austenite grain size increases, the length of martensite lath increases, and the number of martensite blocks decreases.展开更多
The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-...The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.展开更多
基金supported by Topic 3 of the 14th Five-Year National Key Research and Development Plan:Prediction and Control Technology for Hot Rolling Shape-Performance Integration of Ultra Large Size H-beam Steel(Project No.2021YFB3401003).
文摘The axial single-pass high temperature compression test of a hot-rolled extra-large heavy H-beam steel continuous casting billet (Q420 steel) under different deformation conditions through the Gleeble-1500D thermomechanical simulator was carried out. The modified Johnson–Cook model and the Arrhenius model based on strain-compensated of Q420 steel were established. The latter can more accurately reflect the flow behavior of Q420 steel. For the simulation of thermal compression, dynamic recrystallization (DRX) correlation models were developed and imported into DEFORM-3D software. According to simulation results, high temperatures and low strain rates are conducive to DRX. Due to the uneven distribution of equivalent strain and temperature in different parts of the same section, DRX volume fraction and grain size are unevenly distributed. At the center, the DRX volume fraction is the largest and the grain size is the smallest. The upper and lower edges are vice versa, and the left and right edges are centered. Optical microscopy and electron backscatter diffraction characterization methods were used to study the hot compression microstructure under different deformation conditions. As the deformation amount increases, complete DRX is gradually reached. The original austenite grain gradually becomes smaller. Local average misorientation decreases with the progression of DRX but increases with the amount of deformation after completion of DRX. As the temperature increases and the rate decreases, low angle grain boundaries and medium angle grain boundaries gradually decrease, and high angle grain boundaries gradually increase, indicating that dislocation decreases gradually, DRX grains increase gradually, and martensitic multilayer structure is obvious. As austenite grain size increases, the length of martensite lath increases, and the number of martensite blocks decreases.
基金Funded by the "11th Five" National Science and Technology Support Project(No.2006BAE03A13)
文摘The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.
