In this work, the effects of mould pre-heating temperatures and hot isostatic pressing （HIPping） process on the microstructural characteristics and mechanical properties, including static tensile and damage- toleran...In this work, the effects of mould pre-heating temperatures and hot isostatic pressing （HIPping） process on the microstructural characteristics and mechanical properties, including static tensile and damage- tolerance properties of large thin-wall cylindrical Ti-6Al-4V casting, have been studied. The experimental results show that with the increasing mould pre-heating temperature from 673 to 873 K, the casting mi- crostructures change from a mixture of Widmanstatten and colony microstructure to a primary colony. The centre of the thick wall section has relatively coarse microstructure than the edge and thin section. Lower mould pre-heating temperature brings about more porosities. HIPping process, which not only reduces the casting pores effectively but also increases the prior β grain boundary cohesion and coars- ens the microstructure, is essential to improving the ductility of the casting. Due to the oxygen contamination and finer microstructure on the surface, micro-hardness profiles on the cross section present a decreas- ing tendency from the surface to inner. The thickness of the reaction layers for the different mould pre-heating temperatures is nearly the same （-450 μm）. On the whole, the tensile strength and micro- hardness decrease with increasing mould pre-heating temperature from 673 to 873 K. However, the fracture toughness and fatigue crack growth resistance of the castings increase with increasing mould pre- heating temperature.展开更多
The integrated process of steelmaking,continuous casting,and hot rolling(SM-CC-HR)covers the entire process from refining liquid steel to manufacturing semi-finished steel products.lts batch planning and scheduling ar...The integrated process of steelmaking,continuous casting,and hot rolling(SM-CC-HR)covers the entire process from refining liquid steel to manufacturing semi-finished steel products.lts batch planning and scheduling are connected to the production contract plan at the upper level and the production process contro at the lower level,which is the key to achieving eficient and full process steel manufacturing.Batch planning determines the location of the slabs to be produced in the converter,ladle,continuous casting machine,and hot roling mill by combining production orders,process standards,and production conditions.Production scheduling,guided by batch planning,combines production performance indicators,process constraints,etc..to determine the equipment selection and start-stop times of speciic production units at each process.The synergy of the two aims to optimize production profitability,energy consumption,efficiency,etc.,through rational decisions,ensuring the efficiency and flexibility of the steel production process.However,due to the traditional"divide and conguer"management mode and the influence of many uncertain factors,it is dificult to ensure the flexible balance between the demand and capacity,as well as a reasonable matching of logistics and resources among the production processes that operate independently.Considering the uncertain environment and the integration of SM-CC-HR,this paper summarizes the research status of previous scholars from three aspects:mathematical modeling,model optimization,and algorithm optimization based on the Lagrangian framework.lt discusses the research status of batch planning and scheduling methods for SM-CC HR production based on the Lagrangian relaxation framework,analyzes the problems existing in current research,and points out the main research directions and important research contents in the future,in order to promote the research and application of batch planning and scheduling problems for SM-CC-HR under uncertain environments.展开更多
基金financial support from the COLTS programme (Programme No. FP7-AAT-2010-RTD-CHINA)
文摘In this work, the effects of mould pre-heating temperatures and hot isostatic pressing （HIPping） process on the microstructural characteristics and mechanical properties, including static tensile and damage- tolerance properties of large thin-wall cylindrical Ti-6Al-4V casting, have been studied. The experimental results show that with the increasing mould pre-heating temperature from 673 to 873 K, the casting mi- crostructures change from a mixture of Widmanstatten and colony microstructure to a primary colony. The centre of the thick wall section has relatively coarse microstructure than the edge and thin section. Lower mould pre-heating temperature brings about more porosities. HIPping process, which not only reduces the casting pores effectively but also increases the prior β grain boundary cohesion and coars- ens the microstructure, is essential to improving the ductility of the casting. Due to the oxygen contamination and finer microstructure on the surface, micro-hardness profiles on the cross section present a decreas- ing tendency from the surface to inner. The thickness of the reaction layers for the different mould pre-heating temperatures is nearly the same （-450 μm）. On the whole, the tensile strength and micro- hardness decrease with increasing mould pre-heating temperature from 673 to 873 K. However, the fracture toughness and fatigue crack growth resistance of the castings increase with increasing mould pre- heating temperature.
基金supported by the National Natural Science Foundation of China(No.92367106)Natural Science Foundation of Hebei Province of China(No.F2023501006)supported by the Belarusian Republican Foundation for Fundamental Research(No.Ф23РНФ-017).
文摘The integrated process of steelmaking,continuous casting,and hot rolling(SM-CC-HR)covers the entire process from refining liquid steel to manufacturing semi-finished steel products.lts batch planning and scheduling are connected to the production contract plan at the upper level and the production process contro at the lower level,which is the key to achieving eficient and full process steel manufacturing.Batch planning determines the location of the slabs to be produced in the converter,ladle,continuous casting machine,and hot roling mill by combining production orders,process standards,and production conditions.Production scheduling,guided by batch planning,combines production performance indicators,process constraints,etc..to determine the equipment selection and start-stop times of speciic production units at each process.The synergy of the two aims to optimize production profitability,energy consumption,efficiency,etc.,through rational decisions,ensuring the efficiency and flexibility of the steel production process.However,due to the traditional"divide and conguer"management mode and the influence of many uncertain factors,it is dificult to ensure the flexible balance between the demand and capacity,as well as a reasonable matching of logistics and resources among the production processes that operate independently.Considering the uncertain environment and the integration of SM-CC-HR,this paper summarizes the research status of previous scholars from three aspects:mathematical modeling,model optimization,and algorithm optimization based on the Lagrangian framework.lt discusses the research status of batch planning and scheduling methods for SM-CC HR production based on the Lagrangian relaxation framework,analyzes the problems existing in current research,and points out the main research directions and important research contents in the future,in order to promote the research and application of batch planning and scheduling problems for SM-CC-HR under uncertain environments.
