Production process for improving conductivity of U75V steel rail for subway

Abstract

The invention discloses a production process for improving the conductivity of a U75V steel rail for a subway, which comprises the following steps: a smelting process: adopting aluminum-free deoxidation alloying in vacuum smelting, and protecting vacuum in the whole process of smelting; rolling process; a heat treatment process: heating to 200 DEG C, preserving heat for 40 minutes, and then air-cooling to room temperature; the U75V steel rail comprises the following chemical components in percentage by mass: 0.71-0.75% of C; 0.50 to 0.60 percent of Si; 0.75 to 0.85 percent of Mn; 0.00 to 0.15% of Cr; 0.10 to 0.15% of Cu; 0.00 to 0.10 percent of Ni; less than or equal to 0.03% of V; less than or equal to 0.015% of P; s is less than or equal to 0.010%; and the balance of Fe and impurities. The invention aims to obtain the steel rail with good strength and toughness and low resistivity, so that the steel rail can be applied to subway traffic facilities with complex underground working conditions, and the index of stray current of the subway steel rail to traffic danger is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a production process for improving the conductivity of U75V rails for subways. Background Art

[0002] Subway is a mode of transportation that was born with the economic development and the emergence of metropolises to meet the daily travel needs of urban residents. During the operation of the locomotive, the stray current leaking through the rails can cause electrochemical corrosion of the metal structure of the subway system itself. The corrosion of stray current seriously affects the safe operation of the subway and the normal travel of people. Most subway construction in my country is not synchronized with urban construction and lags behind urban construction facilities. After the subway is completed and put into operation, the stray current will inevitably cause serious corrosion damage to the old underground pipeline steel and steel bars.

[0003] Due to various reasons, such as the fact that in order to save costs during subway construction, some subway stray current protection devices were not actually installed and no installation location was reserved; the stray current online monitoring system of some subway systems cannot fully monitor the leakage of actual stray currents; some protection devices have short service life and poor effect, etc., which makes the subway stray current hazards still serious. In order to meet the needs of the subway rail market and prevent the electrochemical corrosion of buildings around the underground track from causing fracture and collapse accidents, it is very necessary to develop subway rails with low resistance, high tensile strength and tread hardness.

[0004] However, most of my country's subway construction procurement standards are based on the rail material in the industry TB / T2344. Patent CN106978567B discloses a stray current prevention material, but this material does not belong to the material in the industry standard, and the production is heat treated, resulting in increased production economic costs. Therefore, based on the current demand for high-strength, low-resistance rails for subways, this patent has developed a U75V rail with excellent performance and low resistance, which has very important production and economic significance. Summary of the invention

[0005] The purpose of the present invention is to provide a production process for improving the conductivity of U75V rails for subways. According to Ohm's law and the electric power theorem and in combination with actual subway working conditions, the resistance of the rail material is reduced, stray current is reduced and the rail potential is reduced; a rail with good strength and toughness and low resistivity is obtained, so that it can be applied to subway transportation facilities with complex underground working conditions, reduce the traffic hazard index of subway rail stray current, and reduce electrochemical corrosion to underground building facilities.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention discloses a production process for improving the conductivity of U75V rails for subways, comprising:

[0008] Smelting process: 25kg medium frequency vacuum induction furnace smelting → electric induction heating furnace heating steel ingot → pilot small rolling mill rolling → air cooling; vacuum smelting adopts aluminum-free deoxidation alloying, and the whole process of smelting protects vacuum;

[0009] Rolling process: 25kg cylindrical steel ingot → heating → rolling on pilot small rolling mill → air cooling → heat treatment; ingot heating and insulation temperature is 1230℃; furnace temperature is not less than 1100℃, rolling temperature is 950℃-1050℃, and final rolling temperature is 890℃-950℃; heat treatment process: heating at 200℃ and insulation for 40 minutes, then air cooling to room temperature;

[0010] The chemical composition of the U75V rail is as follows: C 0.71-0.75%; Si 0.50-0.60%; Mn 0.75-0.85%; Cr 0.00-0.15%; Cu 0.10-0.15%; Ni 0.00-0.10%; V≤0.03%; P≤0.015%; S≤0.010%; the rest is Fe and impurities, with a total mass fraction of 100%.

[0011] Furthermore, the chemical composition of the U75V rail by mass percentage is: C 0.72%; Si 0.52%; Mn 0.78%; Cr 0.12%; Cu 0.11%; Ni 0.08%; P 0.012%; S 0.004%; the rest is Fe and impurities, with a total mass fraction of 100%.

[0012] Furthermore, the chemical composition of the U75V rail is as follows: C 0.73%, Si 0.50%, Mn 0.79%, Cr 0.13%, Cu 0.10%, Ni 0.09%, P 0.010%, S 0.006%, and the rest is Fe and impurities, with a total mass fraction of 100%.

[0013] Furthermore, the chemical composition of the U75V rail by mass percentage is: C 0.71%; Si 0.52%; Mn 0.77%; Cr 0.13%; Cu 0.12%; Ni 0.07%; P 0.010%; S 0.002%; the rest is Fe and impurities, with a total mass fraction of 100%.

[0014] Furthermore, the chemical composition of the U75V rail by mass percentage is: C 0.72%; Si 0.53%; Mn 0.78%; Cr 0.11%; Cu 0.11%; Ni 0.08%; P 0.009%; S 0.007%; the rest is Fe and impurities, with a total mass fraction of 100%.

[0015] Furthermore, the chemical composition of the U75V rail by mass percentage is: C 0.73%; Si 0.53%; Mn 0.76%; Cr 0.11%; Cu 0.13%; Ni 0.06%; P 0.012%; S 0.002%; the rest is Fe and impurities, with a total mass fraction of 100%.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are:

[0017] The present invention reduces the resistivity of the rail by reducing the elements C, P, and S, and adds alloy elements such as Cu, Cr, and Cu to improve the strength and hardness of the rail. The material sample after rolling is further heat-treated to make the internal structure of the material more uniform, eliminate the temperature cooling stress after rolling, and improve the tensile strength, hardness, toughness and conductivity of the rail material. The rail material produced by the present invention has low resistance and good tensile strength and tread hardness. The low-resistance subway U75V rail material of the present invention has a unique alloy design, is suitable for large-scale production, and has good promotion value. DETAILED DESCRIPTION

[0018] A production process for improving the conductivity of U75V rails for subways:

[0019] The smelting production process of steel is: The pilot smelting production process of steel is: 25kg medium frequency vacuum induction furnace smelting → electric induction heating furnace heating steel ingot → pilot small rolling mill rolling → air cooling. Vacuum smelting adopts aluminum-free deoxidation alloying. The chemical composition of each embodiment is shown in Table 1.

[0020] Table 1 Composition of each embodiment (mass percentage / %)

[0021]

[0022] The rolling process is as follows: the pilot test research process of the rail material is as follows: 25kg cylindrical steel ingot → heating → rolling with a pilot small rolling mill → air cooling → heat treatment simulation experiment. The heating and insulation temperature of the steel ingot is 1230℃; the furnace temperature is not less than 1100℃, the rolling temperature is 950℃-1050℃, and the final rolling temperature is 890℃-950℃. The heat treatment experiment of the rail is carried out considering the electrical conductivity, the internal structure of the material and the effect after the cooling process. Heat treatment process system: heating at 200℃ and keeping warm for 40 minutes, then air cooling to room temperature.

[0023] Steel sample performance: The tensile sample specifications are: diameter d0 = 10mm, gauge length Lo = 5do. Random sampling of tread hardness on the rolled material, 5 test points, Brinell hardness test, calculate the average value, the test temperature is 20℃ ± 5℃. The resistivity is measured with a multimeter, the experimental sample size is 60cm×15cm×20cm (length×width×thickness), and the measured value is converted to per kilometer

[0024] 60kg / m rail resistance. The experimental results are shown in Table 2.

[0025] Table 2 Mechanical properties of each embodiment

[0026]

[0027]

[0028] It can be seen from Table 2 that each embodiment has good strength, hardness and mechanical properties. The rails produced by the embodiments meet the U75V standard component quality requirements. The material has good electrical conductivity and reduces corrosion caused by line stray current.

[0029] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A production process for improving the conductivity of U75V rails for subways, characterized in that: include: Smelting process: 25kg medium frequency vacuum induction furnace smelting → electric induction heating furnace heating steel ingot → pilot small rolling mill rolling → air cooling; vacuum smelting adopts aluminum-free deoxidation alloying, and the whole process of smelting protects vacuum; Rolling process: 25kg cylindrical steel ingot → heating → rolling on pilot small rolling mill → air cooling → heat treatment; ingot heating and insulation temperature is 1230℃; furnace temperature is not less than 1100℃, rolling temperature is 950℃-1050℃, and final rolling temperature is 890℃-950℃; heat treatment process: heating at 200℃ and insulation for 40 minutes, then air cooling to room temperature; The chemical composition of the U75V rail is as follows: C 0.71-0.75%; Si 0.50-0.60%; Mn 0.75-0.85%; Cr 0.00-0.15%; Cu 0.10-0.15%; Ni 0.00-0.10%; V≤0.03%; P≤0.015%; S≤0.010%; the rest is Fe and impurities, with a total mass fraction of 100%.

2. The process for improving the conductivity of U75V rails for subways according to claim 1, characterized in that: The chemical composition of the U75V rail is as follows: C 0.72%, Si 0.52%, Mn 0.78%, Cr 0.12%, Cu 0.11%, Ni 0.08%, P 0.012%, S 0.004%; the rest is Fe and impurities, with a total mass fraction of 100%.

3. The production process for improving the conductivity of U75V rails for subways according to claim 1, characterized in that: The chemical composition of the U75V rail is as follows: C 0.73%, Si 0.50%, Mn 0.79%, Cr 0.13%, Cu 0.10%, Ni 0.09%, P 0.010%, S 0.006%; the rest is Fe and impurities, with a total mass fraction of 100%.

4. The production process for improving the conductivity of U75V rails for subways according to claim 1, characterized in that: The chemical composition of the U75V rail is as follows: C 0.71%, Si 0.52%, Mn 0.77%, Cr 0.13%, Cu 0.12%, Ni 0.07%, P 0.010%, S 0.002%; the rest is Fe and impurities, with a total mass fraction of 100%.

5. The production process for improving the conductivity of U75V rails for subways according to claim 1 is characterized in that: The chemical composition of the U75V rail is as follows: C 0.72%, Si 0.53%, Mn 0.78%, Cr 0.11%, Cu 0.11%, Ni 0.08%, P 0.009%, S 0.007%; the rest is Fe and impurities, with a total mass fraction of 100%.

6. The production process for improving the conductivity of U75V rails for subways according to claim 1, characterized in that: The chemical composition of the U75V rail is as follows: C 0.73%, Si 0.53%, Mn 0.76%, Cr 0.11%, Cu 0.13%, Ni 0.06%, P 0.012%, S 0.002%; the rest is Fe and impurities, with a total mass fraction of 100%.

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