Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition...Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition. A new mold slag with low melting point and low basicity was proposed. The initial slag （the base mold slag） and two corresponding mold slags sampled after 8 min and 15 min were investigated, and the changes of mold slag composition and properties of molten slag were discussed. The results showed that the slag quickly changed in chemical composition to a slag that contained a small quantity of silica and a larger quantity of alumina, and the basieity increased obviously; the heat flux density through the slag film decreased slightly compared with the slag film at 0 min, 8 min and 15 min; the mold slag used for nonmagnetic steel was precipitated as CaF2 crystals. The casting experi- ment shows that the slab has good surface quality without longitudinal face cracks and slag inclusions; the Al2O3 content in the molten slag pool increased with time at the beginning stage, and it can approach equilibrium state after about 600 s.展开更多
The regularities of atmospheric corrosion of A3 steel deposited with different amount of NaCl exposed to the air containing 1ppm SO2 at 80%RH and 25℃ were studied in laboratory. NaCl can accelerate the corrosion of A...The regularities of atmospheric corrosion of A3 steel deposited with different amount of NaCl exposed to the air containing 1ppm SO2 at 80%RH and 25℃ were studied in laboratory. NaCl can accelerate the corrosion of A3 steel obviously under such condition. The relationship between the weight loss of A3 steel and the amount of NaCl deposition can be well described by using a quadratic function. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products. In the absence of NaCl, FeSO4 · xH2O is the dominant corrosion products, while Fe3O4, FeSO4·H2O, β-FeOOH and γ-FeOOH dominate in the presence of NaCl.展开更多
The morphology,microstructure and decomposition behavior of M2C carbides in high speed steels with different chemical compositions have been investigated by scanning electron microscopy,transmission electron microscop...The morphology,microstructure and decomposition behavior of M2C carbides in high speed steels with different chemical compositions have been investigated by scanning electron microscopy,transmission electron microscopy,electron backscatter diffraction and X-ray diffraction.The results show that the morphology and substructure of M2C carbides are very sensitive to chemical compositions of high speed steels.M2C carbides present the plate-like shape in tungsten-molybdenum steel and present the polycrystal orientation in the eutectic cell.In contrast,they show the fibrous shape in molybdenum-base steel and exhibit the monocrystal orientation.Plate-like and fibrous M2C carbides are both metastable and decompose into M6 C together with MC at high temperatures.MC nucleates inside the plate-like M2C while it is formed at the fibrous M2C/matrix interface during the decomposition process.Such differences are expected to arise from different compositions of plate-like and fibrous M2C carbides.展开更多
基金Item Sponsored by National Natural Science Foundation of China(50874125)
文摘Because of the addition of significant quantities of aluminum and manganese, the great challenge of casting 20Mn23Al nonmagnetic steel is to design a mold slag that is chemically compatible with this steel composition. A new mold slag with low melting point and low basicity was proposed. The initial slag （the base mold slag） and two corresponding mold slags sampled after 8 min and 15 min were investigated, and the changes of mold slag composition and properties of molten slag were discussed. The results showed that the slag quickly changed in chemical composition to a slag that contained a small quantity of silica and a larger quantity of alumina, and the basieity increased obviously; the heat flux density through the slag film decreased slightly compared with the slag film at 0 min, 8 min and 15 min; the mold slag used for nonmagnetic steel was precipitated as CaF2 crystals. The casting experi- ment shows that the slab has good surface quality without longitudinal face cracks and slag inclusions; the Al2O3 content in the molten slag pool increased with time at the beginning stage, and it can approach equilibrium state after about 600 s.
基金This work was financially supported by the National Natural Science Foundation of China (Project No. 59899144). The authors are grateful to Ms Wang for English diction.
文摘The regularities of atmospheric corrosion of A3 steel deposited with different amount of NaCl exposed to the air containing 1ppm SO2 at 80%RH and 25℃ were studied in laboratory. NaCl can accelerate the corrosion of A3 steel obviously under such condition. The relationship between the weight loss of A3 steel and the amount of NaCl deposition can be well described by using a quadratic function. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products. In the absence of NaCl, FeSO4 · xH2O is the dominant corrosion products, while Fe3O4, FeSO4·H2O, β-FeOOH and γ-FeOOH dominate in the presence of NaCl.
基金funded by National Natural Science Foundation of China(51301038,51371050)Industry-Academia-Research Program of Jiangsu Province of China(BY2014127-03)+2 种基金Natural Science Foundation of Jiangsu Province of China(BK20141306)Key Research Program of Jiangsu Province of China(BE2016154)Jiangsu Province Key Laboratory of High-end Structural Materials of China(hsm1404)
文摘The morphology,microstructure and decomposition behavior of M2C carbides in high speed steels with different chemical compositions have been investigated by scanning electron microscopy,transmission electron microscopy,electron backscatter diffraction and X-ray diffraction.The results show that the morphology and substructure of M2C carbides are very sensitive to chemical compositions of high speed steels.M2C carbides present the plate-like shape in tungsten-molybdenum steel and present the polycrystal orientation in the eutectic cell.In contrast,they show the fibrous shape in molybdenum-base steel and exhibit the monocrystal orientation.Plate-like and fibrous M2C carbides are both metastable and decompose into M6 C together with MC at high temperatures.MC nucleates inside the plate-like M2C while it is formed at the fibrous M2C/matrix interface during the decomposition process.Such differences are expected to arise from different compositions of plate-like and fibrous M2C carbides.
