Transient molten steel flow in a slab continuous casting mold has been calculated using large eddy simulation, considering heat transfer and solidification. The transport of bubbles in the liquid pool of the solidifie...Transient molten steel flow in a slab continuous casting mold has been calculated using large eddy simulation, considering heat transfer and solidification. The transport of bubbles in the liquid pool of the solidified shell has been considered according to the dispersed phase model. A mathematical model has been used to evaluate the influence of bubble size, casting speed, and adsorption of nonmetallic inclusions on bubble removal and bubble distribution within the solidified shell in the mold. The results show that the ratio of bubbles floating to the top surface decreases with increasing casting speed and decreasing bubble diameter. Nonmetallic inclusion adsorption has a weak effect on the bubble.展开更多
A plate＇s internal quality is very critical, especially for boilers and high-pressure vessels. The ultrasonic test （UT） is the main type of non-destructive flaw detection for heavy plates, which is important becaus...A plate＇s internal quality is very critical, especially for boilers and high-pressure vessels. The ultrasonic test （UT） is the main type of non-destructive flaw detection for heavy plates, which is important because one of the main reasons for plate defects is ultrasonic flaws. This study, based on Baosteel＇ s practical experience in the manufacture of heavy plates, elucidates the cause of defect formation by analyzing ultrasonic flaw testing maps and using special equipment, such as the scanning electron microscope, electron probe and the optical microscope. The author puts forward the following improvement measures： ① Ultrasonic flaws are caused by central porosity and segregation,[H] bubbles and inclusion in slabs.②Ultrasonic flaws are more likely to occur in the bottom and top of slabs rather than the other positions in the casting sequence. It is clear that one-quarter of the inner camber＇ s thickness is accumulated inclusion.③It is clear that overheating in the tundish and the flow of the casting mould have an effect on ultrasonic flaws caused by inclusions.④Soft reduction improves central porosity and segregation,which decreases the number of ultrasonic flaws in the plate.展开更多
文摘Transient molten steel flow in a slab continuous casting mold has been calculated using large eddy simulation, considering heat transfer and solidification. The transport of bubbles in the liquid pool of the solidified shell has been considered according to the dispersed phase model. A mathematical model has been used to evaluate the influence of bubble size, casting speed, and adsorption of nonmetallic inclusions on bubble removal and bubble distribution within the solidified shell in the mold. The results show that the ratio of bubbles floating to the top surface decreases with increasing casting speed and decreasing bubble diameter. Nonmetallic inclusion adsorption has a weak effect on the bubble.
文摘A plate＇s internal quality is very critical, especially for boilers and high-pressure vessels. The ultrasonic test （UT） is the main type of non-destructive flaw detection for heavy plates, which is important because one of the main reasons for plate defects is ultrasonic flaws. This study, based on Baosteel＇ s practical experience in the manufacture of heavy plates, elucidates the cause of defect formation by analyzing ultrasonic flaw testing maps and using special equipment, such as the scanning electron microscope, electron probe and the optical microscope. The author puts forward the following improvement measures： ① Ultrasonic flaws are caused by central porosity and segregation,[H] bubbles and inclusion in slabs.②Ultrasonic flaws are more likely to occur in the bottom and top of slabs rather than the other positions in the casting sequence. It is clear that one-quarter of the inner camber＇ s thickness is accumulated inclusion.③It is clear that overheating in the tundish and the flow of the casting mould have an effect on ultrasonic flaws caused by inclusions.④Soft reduction improves central porosity and segregation,which decreases the number of ultrasonic flaws in the plate.
