Method for improving online service performance of U71Mn high-speed steel rail

Abstract

The invention discloses a method for improving online service performance of a U71Mn high-speed steel rail. The method comprises the steps that steel rails with different performances are selected according to application scenes, and components of the steel rails are precisely controlled; the precise control over the components of the steel rail comprises the specific operation steps that during steel rail smelting, only 0.8-1.5 kg / t of low-aluminum silicon calcium barium is added for pre-deoxidation in the converter tapping process, LF refining reducing slag is made for sufficient deoxidation, RH vacuum refining continues for deep deoxidation, when the oxygen content in steel is reduced to 10 ppm or below, alloy is added according to the steel grade component requirement, and before continuous casting is started, the steel rail is subjected to continuous casting, and the steel rail is subjected to continuous casting. And standing for 50-60 minutes on a bale rotary table. By means of the method, the online service life of the U71Mn high-speed steel rail can be effectively prolonged, the online quality problem of the steel rail is solved, and the rail replacing frequency is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for improving the on-line service performance of a U71Mn high-speed rail. Background Art

[0002] With the implementation of my country's railway power strategy, the railway industry has developed rapidly, especially the 350km / h high-speed train, as a beautiful business card of the country, is becoming more and more the best choice for people to travel. Rails, as the main load-bearing components of trains, are the most critical factor for the safe and efficient operation of trains. However, in the actual service process, due to the performance fluctuations of high-speed rails and poor wheel-rail relationship, some lines are forced to slow down and change rails, seriously affecting the safety of train operation. In addition, China State Railway Group Co., Ltd. has adjusted the online service life requirements of rails from the original throughput must be greater than 700 million tons to a throughput of more than 1 billion tons. All of the above aspects have put forward extremely high requirements on the quality of rails and online service.

[0003] The patent application with application number CN202110947223.9 provides a method for processing rails with a long service life, which increases the online service life of the rails by shot peening different parts of the rails; the patent application with publication number CN202010194557.9 provides a method for optimizing the profile design of high-speed railway rails, which improves the online service life by optimizing the design of the rail section. The above two existing technologies both reprocess the rails or change the cross-sectional parameters to improve the online service life, rather than improving the performance of the rail base material and / or its use, so they are not the best choice. Summary of the invention

[0004] The present invention aims to provide a method for improving the on-line service performance of U71Mn high-speed rails.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows: A method for improving the online service performance of a U71Mn high-speed rail comprises selecting rails with different performances according to application scenarios and precisely controlling the composition of the rails.

[0006] Furthermore, the present invention selects rails with different performances according to the application scenarios, specifically: if laid in a straight section, select rails with a tensile strength of 880-950Mpa, a cross-sectional elongation of 10.2%-10.8%, a rail head tread hardness of 260-280HBW, and a rail tread decarburization layer depth of ≤0.2mm, and grind the rail tread before operation to further reduce the decarburization layer depth to ≤0.1mm; if laid in a curved section, select rails with a tensile strength of 951-980Mpa, a cross-sectional elongation of 10.9%-11.3%, a rail head tread hardness of 281-295HBW, and a rail tread decarburization layer depth of ≤0.1mm, and grind the rail tread before operation to further reduce the decarburization layer depth to ≤0.05mm.

[0007] Furthermore, the present invention selects rails with different performances according to the application scenario. At the intersection of a straight line and a curve, considering that the stress is more complicated than that of a straight line segment and simpler than that of a curved line, if the straight line segment rail is used directly, the service life will be reduced, and if the curved line segment rail is used, there will be a problem of excess performance. Therefore, segmented control is adopted; that is, for the part close to the straight line segment, the rail is selected according to the requirements for straight line rails; for the part close to the curved line segment, the rail is selected according to the requirements for curved line rails.

[0008] Furthermore, for the rails laid on the straight section, the carbon, silicon and manganese contents are controlled to be: C 0.71-0.72%, Si 0.33-0.35%, and Mn 0.95-0.97%.

[0009] Furthermore, for the rails laid on the curved section, the carbon, silicon and manganese contents are controlled to be: C 0.73-0.74%, Si 0.38-0.40%, Mn 0.99-1.01%.

[0010] Furthermore, the specific operation of the precise control of the rail composition described in the present invention is: during the smelting of the rail, only 0.8-1.5 kg / t of low-aluminum silicon calcium barium is added in the converter steelmaking process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, RH vacuum refining continues deep deoxidation, and when the oxygen content in the steel is reduced to below 10 ppm, alloy is added according to the steel grade composition requirements, and before continuous casting, the ladle is left standing on the turntable for 50-60 minutes to achieve precise control of the composition.

[0011] Furthermore, the method for improving the online service performance of U71Mn high-speed rails of the present invention further includes controlling different train speeds according to the running sections, specifically: the running speed of the train in the straight section is greater than 160km / h, and the running speed of the train in the curved section is less than 160km / h.

[0012] The inventive principle of the technical solution of the present invention is: The tensile strength of U71Mn high-speed rail is above 880MPa, the cross-sectional elongation is above 10%, the rail head and tread hardness is 260-300HB, and the operating curve radius is above 3500 meters; however, in the actual service life of the rail, affected by the hardness of the rail base material itself, the decarburization layer, the relationship between the rail and the wheel, etc., the online service life of the rail will fluctuate greatly. The reduction of service life will seriously affect train safety and will also greatly increase operating costs.

[0013] In response to the above problems, through a large amount of data research, it was found that the fundamental reason for the decline in the online service life of U71Mn rails is that the rail performance was not differentiated according to the stress characteristics of the straight section and the curved section when the rails were laid. In the straight section, the rails are evenly stressed, and the axle weight of the high-speed train is small, so the wear is small; in the curved section, the stress is complex, and the rails are prone to defects such as peeling or flash. Therefore, it is necessary to differentiate the selection of rails according to the stress conditions of the straight section and the curved section, and through the innovation of the smelting process, the precise control of the rail performance can be achieved to improve the online service life of the U71Mn rails.

[0014] Heavy rail steel is a high-carbon steel, and it is very difficult to achieve precise control of its composition. Due to the fluctuation of oxygen content in molten steel, the C content of the finished product usually fluctuates by more than 0.03%, the Si content fluctuates by more than 0.05%, and the Mn content fluctuates by more than 0.05%, which is not conducive to achieving precise control of rail performance. The present invention abandons the previous operation process of alloying during the converter steel-making process and fine-tuning the steel plate composition during the refining process, and chooses to add only 0.8-1.5kg / t of low-aluminum silicon calcium barium for pre-deoxidation during the converter steel-making process, LF refining to make reducing slag for full deoxidation, and RH vacuum refining to continue deep deoxidation. When the oxygen content in the steel is reduced to below 10ppm, alloys are added according to the steel grade composition requirements, and before continuous casting, the steel is left standing on the ladle turntable for 50-60 minutes to achieve precise control of the composition.

[0015] The beneficial effects of adopting the above technical solution are: Compared with conventional unified production, the present invention takes a unique approach. By systematically analyzing the line characteristics and the online service status of the rails, a control strategy for special performance rails is formulated, and a separate production and special matching control approach is implemented in production, thereby achieving a steady increase in the online service life of the rails.

[0016] The method of the present invention can be applied on a large scale in the production and service of rails, can effectively improve the online service life of U71Mn high-speed rails, reduce online quality problems of rails and the number of rail changes, is easy to operate, has stable effects, and has good social and economic benefits. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example 1

[0018] The application scenario of the rails in this embodiment is a straight section of a key national railway line. When smelting the rails, only 0.8 kg / t of low-aluminum silicon calcium barium is added during the converter steelmaking process for pre-deoxidation, LF refining is used to make reducing slag for full deoxidation, and RH vacuum refining is used to continue deep deoxidation. When the oxygen content in the steel is reduced to 10 ppm, alloys are added according to the steel grade composition requirements, and the steel is allowed to stand on the ladle turntable for 50 minutes before continuous casting. The C content of the final finished rail is 0.71-0.72%, the Si content is 0.33-0.34%, and the Mn content is 0.96-0.97%, corresponding to a rail tensile strength of 885-948 MPa, a cross-sectional elongation of 10.5%-10.7%, a rail head tread hardness of 263-279 HBW, and a rail tread decarburization layer depth of 0.18 mm.

[0019] The train runs at a speed of 200 km / h on this straight section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.08 mm. After 250 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 2

[0020] The application scenario of the rail in this embodiment is a straight section of a key national railway line. When smelting the rail, only 1.0 kg / t of low-aluminum silicon calcium barium is added in the converter steel-making process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10 ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, it is allowed to stand on the ladle turntable for 55 minutes before continuous casting. The final finished rail has a C content of 0.71-0.72%, a Si content of 0.34-0.35%, and a Mn content of 0.96-0.97%, corresponding to a rail tensile strength of 880-945 MPa, a cross-sectional elongation of 10.2%-10.8%, a rail head tread hardness of 260-280 HBW, and a rail tread decarburization layer depth of 0.19 mm.

[0021] The train runs at a speed of 250 km / h on this straight section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.09 mm. After 290 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 3

[0022] The application scenario of the rails in this embodiment is a straight section of a key national railway line. When smelting the rails, only 1.2 kg / t of low-aluminum silicon calcium barium is added in the converter steel-making process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10 ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, the steel is left standing on the ladle turntable for 60 minutes before continuous casting. The final finished rail has a C content of 0.72-0.73%, a Si content of 0.33-0.35%, and a Mn content of 0.95-0.97%, corresponding to a rail tensile strength of 885-950 MPa, a cross-sectional elongation of 10.2%-10.6%, a rail head tread hardness of 260-275 HBW, and a rail tread decarburization layer depth of 0.15 mm.

[0023] The train runs at a speed of 200 km / h on this straight section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.07 mm. After 350 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 4

[0024] The application scenario of the rails in this embodiment is a straight section of a key national railway line. When smelting the rails, only 1.5 kg / t of low-aluminum silicon calcium barium is added in the converter steel-making process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10 ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, the steel is left to stand on the ladle turntable for 58 minutes before continuous casting. The final finished rail has a C content of 0.71-0.73%, a Si content of 0.34-0.35%, and a Mn content of 0.96-0.97%, corresponding to a rail tensile strength of 880-945 MPa, a cross-sectional elongation of 10.5%-10.8%, a rail head tread hardness of 271-280 HBW, and a rail tread decarburization layer depth of 0.20 mm.

[0025] The train runs at a speed of 250 km / h on this straight section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.10 mm. After 250 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 5

[0026] The application scenario of the rails in this embodiment is a curved section of a key national railway line with a curve radius of 3500 meters. When smelting the rails, only 1.3kg / t of low-aluminum silicon calcium barium is added in the converter steel-making process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, it is left to stand on the ladle turntable for 54 minutes before continuous casting. The final finished rail has a C content of 0.73-0.74%, a Si content of 0.38-0.39%, and a Mn content of 0.99-1.01%, corresponding to a rail tensile strength of 951-975Mpa, a cross-sectional elongation of 10.9%-11.1%, a rail head tread hardness of 281-290HBW, and a rail tread decarburization layer depth of 0.10mm.

[0027] The train runs at a speed of 160 km / h on this curved section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.05 mm. After 250 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 6

[0028] The application scenario of the rails in this embodiment is a curved section of a key national railway line with a curve radius of 5500 meters. When smelting the rails, only 1.5kg / t of low-aluminum silicon calcium barium is added in the converter steelmaking process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, the steel is left standing on the ladle turntable for 50 minutes before continuous casting. The final finished rail has a C content of 0.74-0.75%, a Si content of 0.39-0.40%, and a Mn content of 1.00-1.01%, corresponding to a rail tensile strength of 958-980Mpa, a cross-sectional elongation of 11.1%-11.3%, a rail head tread hardness of 285-295HBW, and a rail tread decarburization layer depth of 0.09mm.

[0029] The train runs at a speed of 120 km / h on this curved section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.04 mm. After 280 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 7

[0030] The application scenario of the rails in this embodiment is a curved section of a key national railway line with a curve radius of 7000 meters. When smelting the rails, only 1.5kg / t of low-aluminum silicon calcium barium is added for pre-deoxidation during the converter steelmaking process, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, it is allowed to stand on the ladle turntable for 55 minutes before continuous casting. The final finished rail has a C content of 0.73-0.74%, a Si content of 0.38-0.40%, and a Mn content of 0.99-1.01%, corresponding to a rail tensile strength of 951-975Mpa, a cross-sectional elongation of 10.9%-11.2%, a rail head tread hardness of 285-295HBW, and a rail tread decarburization layer depth of 0.08mm.

[0031] The train runs at a speed of 120 km / h on this curved section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.04 mm. After 260 million tons of rails have been in service, the wear is normal and the overall quality is good. Example 8

[0032] The application scenario of the rails in this embodiment is a curved section of a key national railway line with a curve radius of 8500 meters. When smelting the rails, only 1.0kg / t of low-aluminum silicon calcium barium is added in the converter steel-making process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, and RH vacuum refining continues deep deoxidation. When the oxygen content in the steel is reduced to 10ppm, alloy is added according to the steel grade composition requirements. After the alloy is added, it is allowed to stand on the ladle turntable for 60 minutes before continuous casting. The final finished rail has a C content of 0.73-0.74%, a Si content of 0.38-0.40%, and a Mn content of 0.99-1.01%, corresponding to a rail tensile strength of 956-980Mpa, a cross-sectional elongation of 10.9%-11.1%, a rail head tread hardness of 288-295HBW, and a rail tread decarburization layer depth of 0.09mm.

[0033] The train runs at a speed of 100 km / h on this curved section. The rail tread is polished before running, and the depth of the decarburized layer is further controlled to 0.04 mm. After 270 million tons of rails have been in service, the wear is normal and the overall quality is good.

[0034] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for improving the online service performance of U71Mn high-speed rail, characterized in that: The method includes selecting rails with different performances according to application scenarios, and precisely controlling the composition of the rails.

2. A method for improving the online service performance of U71Mn high-speed rail according to claim 1, characterized in that: The rails with different performances are selected according to the application scenarios, specifically: if laid in a straight section, select rails with a tensile strength of 880-950Mpa, a cross-sectional elongation of 10.2%-10.8%, a rail head tread hardness of 260-280HBW, and a rail tread decarburization layer depth of ≤0.2mm; if laid in a curved section, select rails with a tensile strength of 951-980Mpa, a cross-sectional elongation of 10.9%-11.3%, a rail head tread hardness of 281-295HBW, and a rail tread decarburization layer depth of ≤0.1mm.

3. A method for improving the online service performance of U71Mn high-speed rail according to claim 2, characterized in that: For rails laid on straight sections, the rail treads are ground before operation to further reduce the depth of the decarburization layer to ≤0.1mm; for rails laid on curved sections, the rail treads are ground before operation to further reduce the depth of the decarburization layer to ≤0.05mm.

4. A method for improving the online service performance of U71Mn high-speed rail according to claim 2 or 3, characterized in that: For rails laid in straight sections, the carbon, silicon and manganese contents are controlled as follows: C 0.71-0.72%, Si 0.33-0.35%, and Mn0.95-0.97%.

5. A method for improving the online service performance of U71Mn high-speed rail according to claim 2 or 3, characterized in that: For rails laid on curved sections, the carbon, silicon and manganese contents are controlled to: C 0.73-0.74%, Si 0.38-0.40%, Mn0.99-1.01%.

6. The method for improving the online service performance of U71Mn high-speed rail according to claim 1, characterized in that: The rails with different performances are selected according to the application scenarios. At the intersection of a straight line and a curve, the rails are selected according to the requirements for straight line rails near the straight line section; and the rails are selected according to the requirements for curved line rails near the curved line section.

7. The method for improving the online service performance of U71Mn high-speed rail according to claim 1, characterized in that: The specific operation of the precise control of the rail composition is as follows: during rail smelting, only 0.8-1.5 kg / t of low aluminum silicon calcium barium is added during the converter steelmaking process for pre-deoxidation, LF refining makes reducing slag for full deoxidation, RH vacuum refining continues deep deoxidation, and when the oxygen content in the steel drops below 10 ppm, alloys are added according to the steel grade composition requirements, and before continuous casting begins, the steel is left standing on the ladle turntable for 50-60 minutes.

8. The method for improving the online service performance of U71Mn high-speed rail according to claim 1, characterized in that: The method further includes controlling different train speeds according to the running sections, specifically: the train running speed in the straight section is >160km / h, and the train running speed in the curved section is ≤160km / h.