Central shrinkage crack is a common defect encountered in steel ingot casting. It is necessary to limit the degree of crack in case of further propagation in forging. A 234-t steel ingot was dissected to check the int...Central shrinkage crack is a common defect encountered in steel ingot casting. It is necessary to limit the degree of crack in case of further propagation in forging. A 234-t steel ingot was dissected to check the internal quality, and a central shrinkage crack band of 1,400 mm in height and 120 mm in width, was found at a distance of 450 mm under the riser bottom line. Then, thermo-mechanical simulation using an elasto-viscoplastic finite-element model was conducted to analyze the stress-strain evolution during ingot solidification. A new criterion considering mush mechanical property in the brittle temperature range as well as shrinkage porosity was used to identify the shrinkage crack potential, where the degree of shrinkage porosity is regarded as a probability factor using a modified sigmoid function. Different casting processes, such as pouring speed, mould preheating and riser insulation, were optimized with the simulation model. The results show that fast pouring, proper mould preheating and good riser insulation can alleviate shrinkage crack potential in the ingot center.展开更多
Agriculture is the foundation of social development.Under the pressure of population growth,natural disasters,environmental pollution,climate change,and food safety,the interdisciplinary"new agriculture"is b...Agriculture is the foundation of social development.Under the pressure of population growth,natural disasters,environmental pollution,climate change,and food safety,the interdisciplinary"new agriculture"is becoming an important trend of modern agriculture.In fact,new agriculture is not only the foundation of great health and new energy sources,but is also the cornerstone of national food security,energy security,and biosafety.Hydrogen agronomy focuses mainly on the mechanism of hydrogen gas(H2)biology effects in agriculture,and provides a theoretical foundation for the practice of hydrogen agriculture,a component of the new agriculture.Previous research on the biological effects of H2 focused chiefly on medicine.The mechanism of selective antioxidant is the main theoretical basis of hydrogen medicine.Subsequent experiments have demonstrated that H2 can regulate the growth and development of plant crops,edible fungus,and livestock,and enhance the tolerance of these agriculturally important organisms against abiotic and biotic stresses.Even more importantly,H2 can regulate the growth and development of crops by changing the soil microbial community composition and structure.Use of H2 can also improve the nutritional value and postharvest quality of agricultural products.Researchers have also shown that the biological functions of molecular hydrogen are mediated by modulating reactive oxygen species(ROS),nitric oxide(NO),and carbon monoxide(CO)signaling cascades in plants and microbes.This review summarizes and clarifies the history of hydrogen agronomy and describes recent progress in the field.We also argue that emerging hydrogen agriculture will be an important direction in the new agriculture.Further,we discuss several scientific problems in hydrogen agronomy,and suggest that the future of hydrogen agronomy depends on contributions by multiple disciplines.Important future research directions of hydrogen agronomy include hydrogen agriculture in special environments,such as islands,reefs,aircraft,and outer space.展开更多
基金supported by the NSFC-Liaoning Joint Fund(U1508215)the project to strengthen industrial development at the grass-roots level of MIIT China(TC160A310/21)
文摘Central shrinkage crack is a common defect encountered in steel ingot casting. It is necessary to limit the degree of crack in case of further propagation in forging. A 234-t steel ingot was dissected to check the internal quality, and a central shrinkage crack band of 1,400 mm in height and 120 mm in width, was found at a distance of 450 mm under the riser bottom line. Then, thermo-mechanical simulation using an elasto-viscoplastic finite-element model was conducted to analyze the stress-strain evolution during ingot solidification. A new criterion considering mush mechanical property in the brittle temperature range as well as shrinkage porosity was used to identify the shrinkage crack potential, where the degree of shrinkage porosity is regarded as a probability factor using a modified sigmoid function. Different casting processes, such as pouring speed, mould preheating and riser insulation, were optimized with the simulation model. The results show that fast pouring, proper mould preheating and good riser insulation can alleviate shrinkage crack potential in the ingot center.
基金the National Natural Science Foundation of China(No.31972396)the Foshan Agriculture Science and Technology Project(Foshan City Budget,No.140,2019)the Funding from Center of Hydrogen Science,Shanghai Jiao Tong University,China。
文摘Agriculture is the foundation of social development.Under the pressure of population growth,natural disasters,environmental pollution,climate change,and food safety,the interdisciplinary"new agriculture"is becoming an important trend of modern agriculture.In fact,new agriculture is not only the foundation of great health and new energy sources,but is also the cornerstone of national food security,energy security,and biosafety.Hydrogen agronomy focuses mainly on the mechanism of hydrogen gas(H2)biology effects in agriculture,and provides a theoretical foundation for the practice of hydrogen agriculture,a component of the new agriculture.Previous research on the biological effects of H2 focused chiefly on medicine.The mechanism of selective antioxidant is the main theoretical basis of hydrogen medicine.Subsequent experiments have demonstrated that H2 can regulate the growth and development of plant crops,edible fungus,and livestock,and enhance the tolerance of these agriculturally important organisms against abiotic and biotic stresses.Even more importantly,H2 can regulate the growth and development of crops by changing the soil microbial community composition and structure.Use of H2 can also improve the nutritional value and postharvest quality of agricultural products.Researchers have also shown that the biological functions of molecular hydrogen are mediated by modulating reactive oxygen species(ROS),nitric oxide(NO),and carbon monoxide(CO)signaling cascades in plants and microbes.This review summarizes and clarifies the history of hydrogen agronomy and describes recent progress in the field.We also argue that emerging hydrogen agriculture will be an important direction in the new agriculture.Further,we discuss several scientific problems in hydrogen agronomy,and suggest that the future of hydrogen agronomy depends on contributions by multiple disciplines.Important future research directions of hydrogen agronomy include hydrogen agriculture in special environments,such as islands,reefs,aircraft,and outer space.
