CN112458359A - High-toughness high-purity turnout steel rail and preparation method thereof - Google Patents
High-toughness high-purity turnout steel rail and preparation method thereof Download PDFInfo
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- CN112458359A CN112458359A CN202011164320.2A CN202011164320A CN112458359A CN 112458359 A CN112458359 A CN 112458359A CN 202011164320 A CN202011164320 A CN 202011164320A CN 112458359 A CN112458359 A CN 112458359A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention belongs to the technical field of turnout steel rail production, and particularly relates to a high-toughness high-purity turnout steel rail and a preparation method thereof. The invention aims to solve the technical problem of providing a high-toughness high-purity turnout steel rail and a preparation method thereof. The steel rail comprises the following chemical components in percentage by weight: 0.70-0.82% of C, 0.1-0.6% of Si, 0.6-1.3% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, less than or equal to 0.20% of Cr, 0.007-0.015% of Nb, and the balance of Fe and inevitable impurities. The preparation method comprises the following steps: the molten iron in the furnace is subjected to converter smelting → small platform → LF refining → RH vacuum treatment → casting to obtain a billet → slow cooling of a slow cooling pit → austenite homogenization → rolling to obtain a steel rail → heat treatment in sequence. The method improves the toughness and the purity of the turnout steel rail, and greatly improves the contact fatigue resistance of the steel rail.
Description
Technical Field
The invention belongs to the technical field of turnout steel rail production, and particularly relates to a high-toughness high-purity turnout steel rail and a preparation method thereof.
Background
Turnouts, which are key components and core junctions for railway track connection and train guidance, must be fully updated and upgraded in a new railway transportation environment mainly characterized by high speed and heavy load, and the development of turnout rails, which are key base materials for manufacturing turnouts, is one of the primary tasks.
For the turnout for the high-speed railway, the quality of the turnout directly influences the running speed and the safety of the train. Aiming at the outstanding problems of 'insufficient conversion between a point rail and a point rail, large displacement, large conversion resistance' and the like existing in the process of manufacturing a turnout by a turnout rail, the urgent requirements of the development of high-speed railways in China on high-speed turnout steel rails are met, and the full development of the development work of the turnout steel rails is urgently needed.
For the turnout for the heavy haul railway, the transportation working conditions of large axle weight, high density and large transportation capacity of the heavy haul railway form extremely severe operation conditions of the turnout, and the abrasion and damage speed and degree of the turnout are far higher than those of the turnout with the same model of a common line, so that the turnout is frequently replaced. Frequent replacement of the turnout not only obviously increases the maintenance amount and the maintenance cost of railway departments, but also brings hidden dangers to the traffic safety. The service performance of the turnout is mainly determined by the performance of the turnout steel rail except the manufacturing process. At present, heavy-duty turnouts at home and abroad mainly adopt hot-rolled air-cooled supplies, and switch factories finish cutting, milling and heat treatment.
By adopting a secondary heating off-line heat treatment process, the depth of a hardened layer at the rail head part is shallow, the hardness is accelerated and reduced along with the increase of the depth, and the rail head part is easy to generate over-fast abrasion and contact fatigue damage in service; meanwhile, the turnout rail is bent in the heat treatment process, and the full-length straightness is difficult to ensure; but also obviously increases the energy consumption, reduces the turnout manufacturing efficiency and brings environmental pollution. Therefore, the development of high-performance turnout rails with higher obdurability, longer service life, energy conservation and environmental protection is urgent.
Switch rails, particularly switch rails, are usually machined to be extremely thin at the ends of the switch rails. To ensure the safety and durability of switch rails, switch rails generally require high toughness to resist the impact loads of the train. In order to ensure that the turnout steel rail has good toughness, the inside of the turnout steel rail needs higher purity and finer and more dispersedly distributed inclusion distribution form.
Therefore, the existing rolled common carbon turnout steel rail is difficult to meet the development requirements of domestic and foreign heavy-load lines, and a production method of the turnout steel rail with high toughness and high purity is urgently needed.
Disclosure of Invention
The invention aims to solve the technical problem of providing a turnout steel rail with high toughness and high purity and a preparation method thereof.
The invention adopts the technical scheme to solve the technical problems and provides a turnout steel rail with high toughness and high purity. The steel rail comprises the following chemical components in percentage by weight: 0.70-0.82% of C, 0.1-0.6% of Si, 0.6-1.3% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, less than or equal to 0.20% of Cr, 0.007-0.015% of NbS, and the balance of Fe and inevitable impurities.
The invention also provides a preparation method of the high-toughness high-purity turnout steel rail, which comprises the following steps: the molten iron fed into the furnace is sequentially subjected to converter smelting → a small platform → LF refining → RH vacuum treatment → casting to obtain a steel billet → slow cooling of a slow cooling pit → austenite homogenization → rolling to obtain a steel rail → heat treatment; after smelting in the converter, the mass content of C in the molten steel is 0.80-0.90%, Si is 0.30-0.40%, Mn is 0.85-0.95%, V is less than or equal to 0.05%, and Cr is less than or equal to 0.05%; and adding 0.007-0.015% of Nb into the molten steel in the RH vacuum treatment process.
Further, the mass content of S in the molten iron fed into the furnace is 0.008-0.012%.
Further, the temperature for homogenizing the austenite is 1000-1300 ℃, and the time is 200-500 min.
Further, in the rolling process, the billet is rolled at 1000-1200 ℃ and is rolled for 10-15 times; the final rolling temperature of the rolling is less than or equal to 950 ℃.
Further, the total deformation amount of the rolling process is 80-95%.
Further, the heat treatment is to cool the rolled steel rail in a heat treatment unit by using waste heat, wherein the temperature of the rolled steel rail entering the heat treatment unit is 700-800 ℃.
Further, in the heat treatment process, after the steel rail enters the heat treatment unit, cooling media are applied to the central parts of the rail head and the rail bottom of the steel rail at 500-900 ℃, wherein the central cooling speed of the rail head tread, the rail head and the rail bottom is 1.0-3.0 ℃/s.
Further, the cooling medium is compressed air or a mixture of water and air; when the cooling medium is a mixture of water and air, the compression ratio of the air to the water is less than or equal to 1: 3.
Further, in the heat treatment process, the final cooling temperature of the steel rail is 400-600 ℃.
Further, after the steel rail is subjected to heat treatment, the steel rail is naturally cooled to be below 100 ℃, and a vertical and horizontal straightening machine is adopted for straightening.
The invention has the beneficial effects that:
after smelting in a converter, the mass content of C in molten steel is improved to 0.80-0.90%, 0.007-0.015% of Nb is added into the molten steel in the RH vacuum treatment process, and the rolling and heat treatment process is combined, so that the prepared turnout steel rail has higher toughness and more dispersed and pure inclusions in steel compared with the traditional rolling common carbon heat treatment turnout steel rail, the A-type inclusions (manganese sulfide) of the turnout steel rail are less than or equal to 1.5 grade, the B-type inclusions (aluminum oxides) are less than or equal to 0.5 grade, the C-type inclusions (silicates) are less than or equal to 0.5 grade, the D-type inclusions (spherical oxides) are less than or equal to 0.5 grade, the impact toughness of a rail head is more than or equal to 30J, and the low-temperature fracture toughness is more than 37 MPa.m0.5. The method improves the toughness and the purity of the turnout steel rail, and greatly improves the contact fatigue resistance of the steel rail.
Detailed Description
Specifically, the invention provides a high-toughness high-purity turnout steel rail, which comprises the following chemical components in percentage by weight: 0.70-0.82% of C, 0.1-0.6% of Si, 0.6-1.3% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, less than or equal to 0.20% of Cr, 0.007-0.015% of NbS, and the balance of Fe and inevitable impurities.
The turnout steel rail has high purity, wherein A-type inclusions (manganese sulfide) in the steel rail are less than or equal to 1.5 grade, B-type inclusions (alumina) are less than or equal to 0.5 grade, C-type inclusions (silicate) are less than or equal to 0.5 grade, and D-type inclusions (spherical oxide) are less than or equal to 0.5 grade, and meanwhile, the steel rail has high toughness, the impact toughness of a rail head is more than or equal to 30J, and the low-temperature fracture toughness is more than 37 MPa.m0.5。
In particular, the invention also provides a preparation method of the high-toughness high-purity turnout steel rail. The method comprises the following steps:
the molten iron fed into the furnace is sequentially subjected to converter smelting → a small platform → LF refining → RH vacuum treatment → casting to obtain a steel billet → slow cooling of a slow cooling pit → austenite homogenization → rolling to obtain a steel rail → heat treatment; after smelting in the converter, the mass content of C in the molten steel is 0.80-0.90%, Si is 0.30-0.40%, Mn is 0.85-0.95%, V is less than or equal to 0.05%, and Cr is less than or equal to 0.05%; and adding 0.007-0.015% of Nb into the molten steel in the RH vacuum treatment process.
Nb has the functions of preventing grain growth, inhibiting deformation austenite recrystallization and generating obvious precipitation strengthening in steel. The Nb is thought to have no recrystallization prevention effect in medium-high carbon steel, so that Nb is mainly applied to low carbon steel, and 0.007-0.015% of Nb is creatively added into molten steel in the RH vacuum treatment process, so that the coarsening behavior of crystal grains can be obviously improved, and the toughness and plasticity of the steel rail can be improved.
In the invention, the temperature for homogenizing austenite is 1000-1300 ℃, and the time is 200-500 min, so that the diffusion process of the structure and the texture is fully completed, the structure is homogenized, and the inclusions are fully diffused.
In the rolling process, the billet is rolled at 1000-1200 ℃, and is rolled for 10-15 times, the total deformation in the rolling process is controlled to be 80-95 percent, austenite grains are further refined, and inclusions are elongated and thinned in the rolling process; in order to prevent the recrystallized grains from growing, refine and work harden, and control the finishing temperature of rolling to be less than or equal to 950 ℃.
In the heat treatment process, in order to ensure that the steel rail has sufficient time in a phase change area, the temperature of the steel rail entering a heat treatment unit is 700-800 ℃. The final cooling temperature for cooling the steel rail is 400-600 ℃, the final cooling temperature is too high, the requirement of a deep hardened layer cannot be fully reflected, the final cooling temperature is too low, a martensite structure is easy to appear, and steel is easy to pour after steel tapping.
The invention reduces the level of inclusions in the steel rail by a smelting process, improves the purity of steel quality, and ensures the toughness and plasticity and low-temperature fracture toughness of the steel rail. The invention uses the rolling waste heat to accelerate the cooling of the turnout steel rail, thereby improving the obdurability of the steel rail.
The present invention will be further illustrated by the following specific examples.
TABLE 1 examples and comparative examples molten steel composition control after converter smelting
TABLE 2 chemical composition/% of the rails of examples and comparative examples
TABLE 3 examples and comparative examples Austenitization and Cooling Process parameters
| Item | Soaking temperature/. degree.C | Soaking time/min | Entering accelerated cooling temperature/° C | Cooling final cooling temperature/. degree.C |
| Example 1 | 1000 | 200 | 700 | 400 |
| Example 2 | 1050 | 300 | 730 | 450 |
| Example 3 | 1150 | 400 | 760 | 500 |
| Example 4 | 1250 | 450 | 790 | 550 |
| Example 5 | 1300 | 500 | 800 | 600 |
| Comparative example 1 | 1150 | 400 | 760 | 500 |
| Comparative example 2 | 900 | 100 | 600 | 300 |
| Comparative example 3 | 1310 | 600 | 900 | 650 |
| Comparative example 4 | 1310 | 100 | 900 | 300 |
The comparative example in the present invention used the same continuous casting and rolling process as in the examples.
The non-metal ratings of the example and comparative rails were examined on both sides of the rail head according to standard requirements, and the test results are shown in table 4.
TABLE 4 evaluation grades of nonmetallic inclusions in inventive examples and comparative examples
The impact was taken on the rail head of each of the examples and comparative examples, and the test results are shown in Table 5.
TABLE 5 Rail head impact of inventive and comparative examples
Contact fatigue test specimens were taken from the rail heads of the examples and comparative examples, respectively, and the test results are shown in table 6.
TABLE 6 contact fatigue of rails of examples of the invention and comparative examples
Claims (9)
1. The high-toughness high-purity turnout steel rail is characterized in that: the chemical components by weight percentage are as follows: 0.70-0.82% of C, 0.1-0.6% of Si, 0.6-1.3% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, less than or equal to 0.20% of Cr, 0.007-0.015% of Nb, and the balance of Fe and inevitable impurities.
2. The method of making a high toughness, high purity switch rail of claim 1 wherein: the method comprises the following steps: the molten iron fed into the furnace is sequentially subjected to converter smelting → a small platform → LF refining → RH vacuum treatment → casting to obtain a steel billet → slow cooling of a slow cooling pit → austenite homogenization → rolling to obtain a steel rail → heat treatment; the mass content of C in the molten steel smelted by the converter is 0.80-0.90%, Si is 0.30-0.40%, Mn0.85-0.95%, V is less than or equal to 0.05%, and Cr is less than or equal to 0.05%; and adding 0.007-0.015% of Nb into the molten steel in the RH vacuum treatment process.
3. The method of manufacturing a high toughness and purity switch rail according to claim 2, wherein: the mass content of S in the molten iron entering the furnace is 0.008-0.012%.
4. A method of producing a high toughness and purity switch rail according to claim 2 or 3, wherein: the temperature for homogenizing the austenite is 1000-1300 ℃, and the time is 200-500 min.
5. A method for manufacturing a high-toughness high-purity turnout rail according to any one of claims 2 to 4, wherein: in the rolling process, the billet is rolled at 1000-1200 ℃ and is rolled for 10-15 times; the final rolling temperature of the rolling is less than or equal to 950 ℃.
6. A method for manufacturing a high-toughness high-purity turnout rail according to any one of claims 2 to 5, wherein: the total deformation amount in the rolling process is 80-95%.
7. A method for manufacturing a high-toughness high-purity turnout rail according to any one of claims 2 to 6, wherein: and in the heat treatment, the rolled steel rail enters a heat treatment unit for cooling by utilizing waste heat, and the temperature of the rolled steel rail entering the heat treatment unit is 700-800 ℃.
8. A method for manufacturing a high-toughness high-purity turnout rail according to any one of claims 2 to 7, wherein: in the heat treatment process, after the steel rail enters a heat treatment unit, cooling media are applied to the central parts of the rail head and the rail bottom of the steel rail at 500-900 ℃, wherein the central cooling speed of the rail head tread, the rail head and the rail bottom is 1.0-3.0 ℃/s.
9. A method for manufacturing a high-toughness high-purity turnout rail according to any one of claims 2 to 8, wherein: in the heat treatment process, the final cooling temperature of the steel rail is 400-600 ℃.
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| CN202011164320.2A CN112458359A (en) | 2020-10-27 | 2020-10-27 | High-toughness high-purity turnout steel rail and preparation method thereof |
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| CN202011164320.2A CN112458359A (en) | 2020-10-27 | 2020-10-27 | High-toughness high-purity turnout steel rail and preparation method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113981325A (en) * | 2021-11-03 | 2022-01-28 | 攀钢集团攀枝花钢铁研究院有限公司 | Medium-strength steel rail and production method thereof |
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2020
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113981325A (en) * | 2021-11-03 | 2022-01-28 | 攀钢集团攀枝花钢铁研究院有限公司 | Medium-strength steel rail and production method thereof |
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Application publication date: 20210309 |