The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE a...The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE and niobium and adjusting the content of C, Si and Mn in steel. At the same time, the abrasion resistance, contact fatigue and fatigue property of BNbRE rail steel are excellent. It also shows that RE in rail steel has the functions of purifying steel, modifying inclusion and micro alloy action effect. The improved steel making process enhances the quality of molten steel. Although the content of RE is low, excellent properties of BNbRE rail steel are achieved.展开更多
Rail/wheel contact fatigue of NbRE rail, Nb rail and U74 rail was investigated using contact fatigue tester. Microstructure and morphology as well as microhardness in the fatigue profiles were analyzed by scanning ele...Rail/wheel contact fatigue of NbRE rail, Nb rail and U74 rail was investigated using contact fatigue tester. Microstructure and morphology as well as microhardness in the fatigue profiles were analyzed by scanning electron microscope and Vickers hardness respectively. The experimental results show that rare earths are able to delay the initiation and the propagation of fatigue cracks and postpone the surface shelling or spalling, even more, to reduce the crack propagation angle and the crack propagation depth in steady stab as well as the plastic deformation area, and to improve work-hardening of the rail steel.展开更多
A compared investigation was made on the microstructure and mechanical properties of continuous casting square blanks of BNbRE and U71Mn heavy rail steels having eutectoid composition. The variation of solidified stru...A compared investigation was made on the microstructure and mechanical properties of continuous casting square blanks of BNbRE and U71Mn heavy rail steels having eutectoid composition. The variation of solidified structure of the square blanks was demonstrated by measuring hardness. The observation to the structure and inclusions in the head, waist and base of the hot-rolled rails of the test steels were carried out with optical microscope and SEM. It is found that the casting blanks of both tested steels compose of three areas with constant hardness and three hardness varying areas, and there is considerable P-eutectic structure in the blank of the U71Mn steel. The distribution of the inclusions in the UT1Mn steel rail is mainly oxides in both rail head and rail base, and is mainly MnS in the waist of the rail. There has strong effect of the addition of rare earth elements on them. The discussion on these results was made.展开更多
Submerged entry nozzle(SEN)clogging is a major problem affecting the production quality of rare earth steel,and finding a suitable refractory outlet can significantly reduce production costs.To explore the relationshi...Submerged entry nozzle(SEN)clogging is a major problem affecting the production quality of rare earth steel,and finding a suitable refractory outlet can significantly reduce production costs.To explore the relationship between refractory composition and interface interaction,unprotected coated Al_(2)O_(3)–MgO refractories and SiO2-coated Al_(2)O_(3)–MgO refractories were added to rare earth high-carbon heavy rail steel under laboratory conditions,and the Al_(2)O_(3)–MgO refractory was found to be more suitable.The results show that,from the epoxy resin side to the refractory side,the contour of the refractory interface reaction layer can be divided into two main layers:an iron-rich reaction layer and an iron-poor reaction layer.Calculations based on the spherical model suggest that the adhesion force is proportional to the size of the refractory particles and inclusions,and the same result applies to the surface tension.Controlling the inclusions at a smaller size has a specific effect on alleviating the erosion of refractories.Combined with the erosion mechanism of Al_(2)O_(3)–MgO refractories,the interface reaction mechanism between Al_(2)O_(3)–MgO refractories and molten steel was proposed,which provides ideas for solving SEN clogging.展开更多
The mechanisms of RE in clean BNbRE steel were studied by means of experimental measurement, microstructural observation and theoretical analysis. For BNbRE steel, the state and the content of RE were measured, and th...The mechanisms of RE in clean BNbRE steel were studied by means of experimental measurement, microstructural observation and theoretical analysis. For BNbRE steel, the state and the content of RE were measured, and the effects and the mechanisms of RE on sulfide inclusions, microstructure and properties of steel were determined. On the condition of increasing the cleanliness of steel, the mechanisms of RE in steel were changed to certain degree. Small amount of RE has the effect of cleaning, modifying inclusions and alloying in clean steel, too. With increasing the cleanliness of BNbRE steel, addition of RE should be decreased properly. Under experimental conditions, the optimum addition of RE is -0.01 % (mass fraction) for clean BNbRE steel, while RE can evidently improve plasticity and impact toughness of BNbRE steel.展开更多
The internal frictions of the specimens in the waist centre of the commercial BNb and BNbRE rails, which were left in air for two years, were measured. It is found that there is an obvious Snoek-Kê-Koester (SKK...The internal frictions of the specimens in the waist centre of the commercial BNb and BNbRE rails, which were left in air for two years, were measured. It is found that there is an obvious Snoek-Kê-Koester (SKK) peak in both steels, and still exists a measurable deformation-enhanced Shock peak(DESP) in the specimens of the BNbRE steel. The internal frictions in the deformed specimens of the both steel rails were also measured. Unlike the case of the tread specimens showing a decrease of SKK damping due to deformation, the SKK damping of the rail waist specimens increases after deformation; and the specimens containing rare earth(RE) show more noticeable damping increase than those without RE. The results of the internal friction measured during ascending and descending temperature under 700℃ show that there is a high temperature damping which can be completely disappeared during descending temperature for both steels.展开更多
The mechanisms of La in heavy rail steel were studied by means of experimental measurements, microstructure observation and theoretical analysis in the present work. For heavy rail steel, the state and the content of ...The mechanisms of La in heavy rail steel were studied by means of experimental measurements, microstructure observation and theoretical analysis in the present work. For heavy rail steel, the state and the content of La were measured, and the mechanisms and the effects of La on sulfide inclusions, microstracture and properties of steel were determined. Strip-like sulfides disappear in heavy rail steel with La/(O+S)〉3.50, which is shown that the metallurgical function of modifying sulfide inclusions has been achieved by La. La can fine the grain size of the austenite in heavy rail steel. Under the experimental condition, the plasticity and the impacting toughness of heavy rail steel with 0.005wt% La can evidently be improved.展开更多
The text determines the hot plasticity of CC blank for heavy rail between BNbRE and BNbRE(V) under 1300~850 ℃ by using Gleeble 1500D. It also makes comparative analysis of the microstructure and fracture of the tens...The text determines the hot plasticity of CC blank for heavy rail between BNbRE and BNbRE(V) under 1300~850 ℃ by using Gleeble 1500D. It also makes comparative analysis of the microstructure and fracture of the tensile specimens by scanning electronic microscope. The result indicates that hot plasticity is almost zero when temperature is between 1200~1300 ℃. While hot plasticity of BNbRE(V) is better than BNbRE between 975~1200 ℃. Plasticity decreases with the reducing temperature from 975 ℃. Hot plasticity of BNbRE(V) reaches the minimum because of the precipitation of vanadium in the specimens reaches the maximum at 850 ℃.Vanadium largely affects the plasticity of steel in brittle temperature region Ⅲ and the embrittlement extends to lower temperature.展开更多
In the present study, heavy rail steel was prepared by the process of vacuum induction furnace smelting, forge work and rolling. Effects of Rare earths (RE) on microstructure and mechanical properties of heavy rail st...In the present study, heavy rail steel was prepared by the process of vacuum induction furnace smelting, forge work and rolling. Effects of Rare earths (RE) on microstructure and mechanical properties of heavy rail steel were systematically investigated by metallographic microscope, SEM, integrated mechanical testing machine, impact tester and so on. Metallographic analysis shows that, a few of RE can evidently delay the growth of austenite grain and fine pearlite. When the RE content is 0.016%, both annealing and normalizing pearlite laminae distances reach the minimum which is 115 nm (annealing) and 104nm (normalizing), respectively. But when the RE content reaches 0.133%, the annealing and normalizing pearlite laminae distance is respectively increased by 40% and 13%. Mechanical properties tests show that, a few of RE has not notable effect on the strength, but both plasticity and ductility can be improved obviously. When the RE content is 0.016%, both plasticity and ductility reach maximum. The maximum of elongation and reduction of area is 13.3% and 29.0%, respectively. However, when the RE content reaches 0.133%, the strength, plasticity and ductility are decreased. Especially, the low temperature (-40 ℃) and room temperature (20 ℃) ballistic work is respectively decreased by 9% and 24.8%.展开更多
文摘The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel ( σ b≥980 MPa, δ 5≥8%) can be improved by adding RE and niobium and adjusting the content of C, Si and Mn in steel. At the same time, the abrasion resistance, contact fatigue and fatigue property of BNbRE rail steel are excellent. It also shows that RE in rail steel has the functions of purifying steel, modifying inclusion and micro alloy action effect. The improved steel making process enhances the quality of molten steel. Although the content of RE is low, excellent properties of BNbRE rail steel are achieved.
文摘Rail/wheel contact fatigue of NbRE rail, Nb rail and U74 rail was investigated using contact fatigue tester. Microstructure and morphology as well as microhardness in the fatigue profiles were analyzed by scanning electron microscope and Vickers hardness respectively. The experimental results show that rare earths are able to delay the initiation and the propagation of fatigue cracks and postpone the surface shelling or spalling, even more, to reduce the crack propagation angle and the crack propagation depth in steady stab as well as the plastic deformation area, and to improve work-hardening of the rail steel.
文摘A compared investigation was made on the microstructure and mechanical properties of continuous casting square blanks of BNbRE and U71Mn heavy rail steels having eutectoid composition. The variation of solidified structure of the square blanks was demonstrated by measuring hardness. The observation to the structure and inclusions in the head, waist and base of the hot-rolled rails of the test steels were carried out with optical microscope and SEM. It is found that the casting blanks of both tested steels compose of three areas with constant hardness and three hardness varying areas, and there is considerable P-eutectic structure in the blank of the U71Mn steel. The distribution of the inclusions in the UT1Mn steel rail is mainly oxides in both rail head and rail base, and is mainly MnS in the waist of the rail. There has strong effect of the addition of rare earth elements on them. The discussion on these results was made.
基金the State Key Laboratory of Rare Earth Resources Research and Comprehensive Utilization of Baiyun Obo for the open project(Grant No.2022(Kehe)00281)the Central Government Guidance Local Science and Technology Development Fund Project(Grant No.2022ZY0124)for supporting this worksupported by the National Natural Science Foundation of China(Grant No.52074179).
文摘Submerged entry nozzle(SEN)clogging is a major problem affecting the production quality of rare earth steel,and finding a suitable refractory outlet can significantly reduce production costs.To explore the relationship between refractory composition and interface interaction,unprotected coated Al_(2)O_(3)–MgO refractories and SiO2-coated Al_(2)O_(3)–MgO refractories were added to rare earth high-carbon heavy rail steel under laboratory conditions,and the Al_(2)O_(3)–MgO refractory was found to be more suitable.The results show that,from the epoxy resin side to the refractory side,the contour of the refractory interface reaction layer can be divided into two main layers:an iron-rich reaction layer and an iron-poor reaction layer.Calculations based on the spherical model suggest that the adhesion force is proportional to the size of the refractory particles and inclusions,and the same result applies to the surface tension.Controlling the inclusions at a smaller size has a specific effect on alleviating the erosion of refractories.Combined with the erosion mechanism of Al_(2)O_(3)–MgO refractories,the interface reaction mechanism between Al_(2)O_(3)–MgO refractories and molten steel was proposed,which provides ideas for solving SEN clogging.
基金Project supported bythe National Natural Science Fundation of China (50374029)
文摘The mechanisms of RE in clean BNbRE steel were studied by means of experimental measurement, microstructural observation and theoretical analysis. For BNbRE steel, the state and the content of RE were measured, and the effects and the mechanisms of RE on sulfide inclusions, microstructure and properties of steel were determined. On the condition of increasing the cleanliness of steel, the mechanisms of RE in steel were changed to certain degree. Small amount of RE has the effect of cleaning, modifying inclusions and alloying in clean steel, too. With increasing the cleanliness of BNbRE steel, addition of RE should be decreased properly. Under experimental conditions, the optimum addition of RE is -0.01 % (mass fraction) for clean BNbRE steel, while RE can evidently improve plasticity and impact toughness of BNbRE steel.
基金Project supported bythe Ministry of National Science and Technique (2002BA315A-5-1-2)
文摘The internal frictions of the specimens in the waist centre of the commercial BNb and BNbRE rails, which were left in air for two years, were measured. It is found that there is an obvious Snoek-Kê-Koester (SKK) peak in both steels, and still exists a measurable deformation-enhanced Shock peak(DESP) in the specimens of the BNbRE steel. The internal frictions in the deformed specimens of the both steel rails were also measured. Unlike the case of the tread specimens showing a decrease of SKK damping due to deformation, the SKK damping of the rail waist specimens increases after deformation; and the specimens containing rare earth(RE) show more noticeable damping increase than those without RE. The results of the internal friction measured during ascending and descending temperature under 700℃ show that there is a high temperature damping which can be completely disappeared during descending temperature for both steels.
基金supported by the National Natural Science Foundation of China(No.50374029)and(No.50204005).
文摘The mechanisms of La in heavy rail steel were studied by means of experimental measurements, microstructure observation and theoretical analysis in the present work. For heavy rail steel, the state and the content of La were measured, and the mechanisms and the effects of La on sulfide inclusions, microstracture and properties of steel were determined. Strip-like sulfides disappear in heavy rail steel with La/(O+S)〉3.50, which is shown that the metallurgical function of modifying sulfide inclusions has been achieved by La. La can fine the grain size of the austenite in heavy rail steel. Under the experimental condition, the plasticity and the impacting toughness of heavy rail steel with 0.005wt% La can evidently be improved.
文摘The text determines the hot plasticity of CC blank for heavy rail between BNbRE and BNbRE(V) under 1300~850 ℃ by using Gleeble 1500D. It also makes comparative analysis of the microstructure and fracture of the tensile specimens by scanning electronic microscope. The result indicates that hot plasticity is almost zero when temperature is between 1200~1300 ℃. While hot plasticity of BNbRE(V) is better than BNbRE between 975~1200 ℃. Plasticity decreases with the reducing temperature from 975 ℃. Hot plasticity of BNbRE(V) reaches the minimum because of the precipitation of vanadium in the specimens reaches the maximum at 850 ℃.Vanadium largely affects the plasticity of steel in brittle temperature region Ⅲ and the embrittlement extends to lower temperature.
基金National Science and Technology Ministry (2006BAB02B03, 2006BAE03A04)Key Project of Chinese Ministry of Education (109048)Special Fund for Basic Scientific Research of Central Colleges (N090402017)
文摘In the present study, heavy rail steel was prepared by the process of vacuum induction furnace smelting, forge work and rolling. Effects of Rare earths (RE) on microstructure and mechanical properties of heavy rail steel were systematically investigated by metallographic microscope, SEM, integrated mechanical testing machine, impact tester and so on. Metallographic analysis shows that, a few of RE can evidently delay the growth of austenite grain and fine pearlite. When the RE content is 0.016%, both annealing and normalizing pearlite laminae distances reach the minimum which is 115 nm (annealing) and 104nm (normalizing), respectively. But when the RE content reaches 0.133%, the annealing and normalizing pearlite laminae distance is respectively increased by 40% and 13%. Mechanical properties tests show that, a few of RE has not notable effect on the strength, but both plasticity and ductility can be improved obviously. When the RE content is 0.016%, both plasticity and ductility reach maximum. The maximum of elongation and reduction of area is 13.3% and 29.0%, respectively. However, when the RE content reaches 0.133%, the strength, plasticity and ductility are decreased. Especially, the low temperature (-40 ℃) and room temperature (20 ℃) ballistic work is respectively decreased by 9% and 24.8%.