Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. Accor...Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. According to the real condition of 40 t ladle in steel-making plant of Baosteel Special Steel Company, previous works show that the key factors affecting the ladle free-opening rate of high aluminum steel in continuous casting are：sand material, accessories baking, ladle nozzle cleaning, the process and amount of adding sand, and the rate of argon stirring during refining. Therefore, improving the ladle filler sand quality, baking all of the raw materials, controlling the addition of ladle filler sand, cleaning the ladle nozzle, and optimizing argon stirring during the refining process can resolve the problem of a low ladle free-opening rate of high aluminum steel caused by the long ladle time of liquid steel.展开更多
Based on a series of related investigations, a mechanism for the formation of longitudinal surface cracks on a continuous casting slab of high-carbon steel was investigated. High-temperature tensile tests performed on...Based on a series of related investigations, a mechanism for the formation of longitudinal surface cracks on a continuous casting slab of high-carbon steel was investigated. High-temperature tensile tests performed on slab samples,metallographic and scanning electron microscopy studies, as well as heat flux and shell thickness in continuous casting predicted on the basis of a mathematical model were conducted. The results showed that high- carbon steel exhibited a much lower liquidus temperature and a wider brittle temperature range immediately after solidification compared with those of low-carbon steel. Concentrations of elements K and Na, which are contained in the mold fluxes, were not observed in the cracks during this study. The calculated results showed that the heat flux and the shell thickness were uneven along the mold width and that the shell was thinner and close to the center line of the slab surface. The longitudinal cracks were observed in situ using confocal laser scanning microscopy, to first occur close to the solidification front,where the ductility was extremely low;in addition ,the shell growth was slower than in other regions, which led to a thinner shell and depressed shrinkage owing to a lack of lubrication by the mold fluxes below the meniscus. Furthermore, the pouring temperature of high-carbon steel is - 100 ~C lower than that of low-carbon steel,so the formation of a stable liquid flux near the meniscus within a short time at the beginning of casting is difficult. The amounts of liquid slag film and crystalline slag film were insufficient to provide adequate lubrication between the shell and the mold, which resulted in greater friction force that induced or aggravated cracks. Therefore, the homogeneity of mold fluxes and initial solidification in the mold should be improved to reduce the concentration of slab surface defects.展开更多
In this study, metallographic analysis and nanoindentation characterization were used to analyze the properties and microstructures of as-cast nitrogen alloyed 27Cr-7Ni-4Mo super duplex stainless steel （super-DSS）. ...In this study, metallographic analysis and nanoindentation characterization were used to analyze the properties and microstructures of as-cast nitrogen alloyed 27Cr-7Ni-4Mo super duplex stainless steel （super-DSS）. The as-cast microstructure of the super-DSS was characterized by its ferrite and island-like austenite phases. During the solution annealing process, the austenite volume percentage of the steel decreased gradually with increased annealing temperature. As a main element, the chromium content in the ferritic and austenitic phases elevated slightly at first then decreased with increased annealing temperature. The chromium partition coefficient in the steel varied by around 1.0. The contents of nickel, another main alloy element, also increased in the ferritic and austenitic phases with increased annealing temperature, as did the nickel partition coefficient in the steel, which tended to be close to 1.0. The nanoindentation characterization results indicate that the hardness of the austenite phase is slightly greater than that of the ferrite phase. They were similar to each other within a certain temperature range from 1 050 ℃ to 1 100℃. This temperature range was consistent with the temperature range in which the content ratio of the two phases was close to 1： 1. We found the Young＇ s modulus of the ferrite phase to be greater than that of the austenite phase. With increased annealing temperature, the Young＇ s modulus of the ferrite phase decreased while that of the austenite phase remained almost unchanged.展开更多
采用传统化学酸洗工艺处理线材,环保运营成本高,作为替代的抛丸表面清理工艺近年来得到快速的发展和应用。介绍抛丸除锈设备工作原理、方式、结构及特点,并对常用单线抛丸设备的结构、工艺参数和处理后线材表面质量进行分析。以7.0 mm...采用传统化学酸洗工艺处理线材,环保运营成本高,作为替代的抛丸表面清理工艺近年来得到快速的发展和应用。介绍抛丸除锈设备工作原理、方式、结构及特点,并对常用单线抛丸设备的结构、工艺参数和处理后线材表面质量进行分析。以7.0 mm SUM24L快削钢为例,经单线抛丸的线材表面均匀一致,粗糙度Ra14.10,氧化物的残留为A Sa2.5~3,符合线材产品拉拔加工要求。抛丸工艺技术为线材生产线实现在线探伤、热处理、连续拉拔等全工序、全流程连续生产线的整合创造了条件。展开更多
文摘Steel 20Mn23AlV is a type of high aluminum steel with a very low ladle free-opening rate. The aluminum composition of 20Mn23AlV ranges from 1.6% to 2.45% ,which is significantly higher than other types of steel. According to the real condition of 40 t ladle in steel-making plant of Baosteel Special Steel Company, previous works show that the key factors affecting the ladle free-opening rate of high aluminum steel in continuous casting are：sand material, accessories baking, ladle nozzle cleaning, the process and amount of adding sand, and the rate of argon stirring during refining. Therefore, improving the ladle filler sand quality, baking all of the raw materials, controlling the addition of ladle filler sand, cleaning the ladle nozzle, and optimizing argon stirring during the refining process can resolve the problem of a low ladle free-opening rate of high aluminum steel caused by the long ladle time of liquid steel.
文摘Based on a series of related investigations, a mechanism for the formation of longitudinal surface cracks on a continuous casting slab of high-carbon steel was investigated. High-temperature tensile tests performed on slab samples,metallographic and scanning electron microscopy studies, as well as heat flux and shell thickness in continuous casting predicted on the basis of a mathematical model were conducted. The results showed that high- carbon steel exhibited a much lower liquidus temperature and a wider brittle temperature range immediately after solidification compared with those of low-carbon steel. Concentrations of elements K and Na, which are contained in the mold fluxes, were not observed in the cracks during this study. The calculated results showed that the heat flux and the shell thickness were uneven along the mold width and that the shell was thinner and close to the center line of the slab surface. The longitudinal cracks were observed in situ using confocal laser scanning microscopy, to first occur close to the solidification front,where the ductility was extremely low;in addition ,the shell growth was slower than in other regions, which led to a thinner shell and depressed shrinkage owing to a lack of lubrication by the mold fluxes below the meniscus. Furthermore, the pouring temperature of high-carbon steel is - 100 ~C lower than that of low-carbon steel,so the formation of a stable liquid flux near the meniscus within a short time at the beginning of casting is difficult. The amounts of liquid slag film and crystalline slag film were insufficient to provide adequate lubrication between the shell and the mold, which resulted in greater friction force that induced or aggravated cracks. Therefore, the homogeneity of mold fluxes and initial solidification in the mold should be improved to reduce the concentration of slab surface defects.
文摘In this study, metallographic analysis and nanoindentation characterization were used to analyze the properties and microstructures of as-cast nitrogen alloyed 27Cr-7Ni-4Mo super duplex stainless steel （super-DSS）. The as-cast microstructure of the super-DSS was characterized by its ferrite and island-like austenite phases. During the solution annealing process, the austenite volume percentage of the steel decreased gradually with increased annealing temperature. As a main element, the chromium content in the ferritic and austenitic phases elevated slightly at first then decreased with increased annealing temperature. The chromium partition coefficient in the steel varied by around 1.0. The contents of nickel, another main alloy element, also increased in the ferritic and austenitic phases with increased annealing temperature, as did the nickel partition coefficient in the steel, which tended to be close to 1.0. The nanoindentation characterization results indicate that the hardness of the austenite phase is slightly greater than that of the ferrite phase. They were similar to each other within a certain temperature range from 1 050 ℃ to 1 100℃. This temperature range was consistent with the temperature range in which the content ratio of the two phases was close to 1： 1. We found the Young＇ s modulus of the ferrite phase to be greater than that of the austenite phase. With increased annealing temperature, the Young＇ s modulus of the ferrite phase decreased while that of the austenite phase remained almost unchanged.
文摘采用传统化学酸洗工艺处理线材,环保运营成本高,作为替代的抛丸表面清理工艺近年来得到快速的发展和应用。介绍抛丸除锈设备工作原理、方式、结构及特点,并对常用单线抛丸设备的结构、工艺参数和处理后线材表面质量进行分析。以7.0 mm SUM24L快削钢为例,经单线抛丸的线材表面均匀一致,粗糙度Ra14.10,氧化物的残留为A Sa2.5~3,符合线材产品拉拔加工要求。抛丸工艺技术为线材生产线实现在线探伤、热处理、连续拉拔等全工序、全流程连续生产线的整合创造了条件。
