CN113930667A - Rail with good coupling of abrasion and rolling contact fatigue and production method thereof - Google Patents
Rail with good coupling of abrasion and rolling contact fatigue and production method thereof Download PDFInfo
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
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- 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
- C21D1/78—Combined heat-treatments not provided for above
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- 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
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- 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
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- 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
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- 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
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- 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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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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
- C22C38/18—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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- 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
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Abstract
The invention discloses a steel rail with good coupling of abrasion and rolling contact fatigue and a production method thereof, wherein the steel rail comprises the following chemical components in percentage by weight: 0.75-0.88%, Si: 0.60-0.80%, Mn: 0.90-1.30%, V: 0.08-0.15%, Cr: 0.15-0.30%, Nb: 0.02-0.08%, B: 0.004-0.008%, less than or equal to 0.025% of P, less than or equal to 0.025% of S, and the balance of Fe and inevitable impurities. The rail head is accelerated and cooled in stages, the cooling speed and the cooling time of each stage are reasonably distributed, and the pearlite interlayer spacing of the metallographic structure of the rail head is reasonably controlled, so that the development of rail abrasion and rolling contact fatigue can be well coupled, the comprehensive service performance and the service life of the rail are improved, and the production method is simple, strong in operability and easy to popularize and apply.
Description
Technical Field
The invention relates to the field of steel rail production, in particular to a steel rail with good coupling of abrasion and rolling contact fatigue and a production method thereof.
Background
The railway construction in China is in a rapid development period, along with the development of railways towards high speed and heavy load, the running speed, the load capacity and the running density of a train are obviously increased, the damage problem of steel rails becomes more obvious, the high-strength heat-treated steel rails can obviously improve the wear resistance and the contact fatigue resistance of the steel rails, and at present, steel rail manufacturers at home and abroad generally adopt an online heat treatment process to improve the strength and the hardness of the steel rails so as to improve the service performance of the steel rails.
Most railways in China are passenger-cargo mixed transportation lines, freight trains with large axle weights and passenger trains with small axle weights pass through the railways simultaneously, the speed and the axle weights of the trains change greatly, and the stress of wheel tracks is complex and changeable. The rail has different damage forms, but generally shows two kinds of damage, namely wear and rolling contact fatigue, and the rolling contact fatigue and the wear of the rail material have a mutual restriction and mutual competition relationship, namely when the strength and the hardness of the rail are low, the wear of the rail is serious, the rolling contact fatigue damage is generally slight, and the service life of the rail is short due to the high wear rate of the rail; when the strength and hardness of the steel rail are higher, the abrasion becomes slight, the generation and the expansion rate of the contact fatigue damage of the steel rail determine the service life of the steel rail, although the abrasion resistance is improved, the rolling contact fatigue damage develops faster and becomes a main failure mode, the service life of the steel rail is also influenced, particularly in a curve line of a passenger-cargo mixed transportation line, the wheel-rail acting force is larger, the mutual restriction and mutual competition relationship of the rolling contact fatigue and the abrasion is more obvious, and the comprehensive service life of the steel rail and the driving safety are seriously influenced.
Aiming at the problems of abrasion and rolling contact fatigue damage of the steel rail of the current passenger-cargo mixed transportation line and the potential safety hazard of driving brought therewith, the steel rail which can well couple the abrasion and the rolling contact fatigue is urgently needed, and the comprehensive use performance of the steel rail is improved.
Disclosure of Invention
The invention provides a rail with good coupling of abrasion and rolling contact fatigue and a production method thereof, aiming at the problems of abrasion and rolling contact fatigue damage of the prior steel rail of a mixed passenger and cargo transportation line.
In order to achieve the purpose, the invention designs a steel rail with good coupling of abrasion and rolling contact fatigue, which comprises the following chemical components in percentage by weight based on the total weight of the steel rail: 0.75-0.88%, Si: 0.60-0.80%, Mn: 0.90-1.30%, V: 0.08-0.15%, Cr: 0.15-0.30%, Nb: 0.02-0.08%, B: 0.004-0.008%, less than or equal to 0.025% of P, less than or equal to 0.025% of S, and the balance of Fe and inevitable impurities.
Further, the chemical components of the steel rail comprise, by weight: 0.76-0.86%, Si: 0.62-0.77%, Mn: 0.98-1.30%, V: 0.08-0.12%, Cr: 0.15-0.25%, Nb: 0.05-0.08%, B: 0.006-0.007%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, and the balance of Fe and inevitable impurities.
Furthermore, the metallographic structure of the steel rail is pearlite and a small amount of ferrite, the interlayer spacing of pearlite is 190nm, the tensile strength of the steel rail is more than or equal to 1250MPa, the elongation is 11-13%, and the brinell hardness of a tread of the rail head is 350 HB and 380 HB.
Still further, the chemical components of the steel rail comprise, by weight: 0.78%, Si: 0.70%, Mn: 1.26%, V: 0.08%, Cr: 0.18%, Nb: 0.08%, B: 0.008%, P: 0.013%, S: 0.007% and the balance of Fe and inevitable impurities.
The invention also provides a production method of the steel rail, which comprises eight steps of converter smelting, LF refining, vacuum treatment, continuous casting, casting blank heating, rolling, accelerated cooling and straightening to prepare the steel rail; the rolled steel rail is subjected to on-line accelerated cooling treatment, and in the cooling process,
the rolled steel rail stays on the roller way, when the surface temperature of the steel rail reaches 700-820 ℃, accelerated cooling is started, the whole cooling process is divided into 5 cooling stages, and the cooling speed of each stage is respectively as follows:
the cooling speed of the 1 st stage is 2-4 ℃/s, the cooling speed of the 2 nd stage is 3-5 ℃/s, the cooling speed of the 3 rd stage is 4-6 ℃/s, the cooling speed of the 4 th stage is 3-5 ℃/s, the cooling speed of the 5 th stage is 2-4 ℃/s, when the temperature of the rail head is reduced to 380 ℃ of 350-.
Preferably, in the cooling process, the cooling rate of each stage is respectively as follows:
the cooling speed of the 1 st stage is 2.5-3.5 ℃/s, the cooling speed of the 2 nd stage is 3.5-4.5 ℃/s, the cooling speed of the 3 rd stage is 4.5-5.5 ℃/s, the cooling speed of the 4 th stage is 3.5-4.5 ℃/s, the cooling speed of the 5 th stage is 2.5-3.5 ℃/s, when the temperature of the rail head is reduced to 360-370 ℃, the accelerated cooling is stopped, and finally the rail head is naturally cooled to the room temperature.
Preferably, in the cooling process, the accelerated cooling time of each stage is equal and is 10-15s, and the absolute value of the cooling speed difference between adjacent cooling stages is controlled within 2 ℃/s.
Preferably, the rail length is subjected to an accelerated cooling heat treatment, the rail head is accelerated to cool and the rail foot is also subjected to the same cooling rate, and when the rail head stops accelerated cooling, the rail foot stops cooling accordingly.
In the invention, the steel rail production method further comprises the following steps: the method comprises the following steps of converter smelting, LF refining, vacuum treatment, continuous casting, casting blank heating, rolling, accelerated cooling, straightening and the like, and the steps are not particularly limited and can be carried out according to a conventional steel rail production process method. For example, the casting process should be performed under full protection to prevent contact with air, the cast billet should be slowly cooled, the billet is heated by a walking beam furnace and is subjected to heat preservation, the billet is rolled by a universal rolling production line, and a horizontal and vertical composite straightening process is adopted.
In the present invention, the cooling medium for accelerated cooling and slow cooling is a cooling medium commonly used in the art, and includes, but is not limited to, water, polymer solution, oil, compressed air, water mist or oil mist mixture, and any substance capable of providing a uniform cooling flow field.
The principle of the raw materials and the process of the invention is as follows:
1. the action and mechanism of each alloy element in the invention are as follows:
c is a main element forming pearlite and carbide, and generally, as the content of C in steel increases, the strength and hardness of steel increase, and plasticity and toughness decrease. When the components are actually designed, the content range of C is determined according to specific technical requirements, the content of C is too low, the density of lamellar cementite in a pearlite structure cannot be ensured, the basic strength and hardness of the steel rail are insufficient, and the using effect is influenced; on the other hand, the C content is too high, which leads to too high rail hardness, accelerated fatigue crack propagation and reduced weldability, so that the C content is controlled within the range of 0.75-0.88 wt%.
Si, which is a main additive element of steel, is generally present in solid solution in ferrite and austenite to improve the strength of matrix structure, inhibit cementite formation in steel, promote ferrite transformation, and easily cause local segregation when the Si content in steel is gradually increased, and the Si content is controlled within the range of 0.60-0.80 wt%.
Mn is a solid solution strengthening element in steel, can improve the ferrite strength, is also a carbide forming element, can partially replace Fe atoms after entering a cementite, and improves the strength and the hardness of the steel. Meanwhile, Mn can also reduce the pearlite transformation temperature, so that the interlayer spacing of the pearlite plates is reduced. An increase in Mn content greatly reduces the weldability of the steel, coarsens the grain size, and increases the susceptibility to white spot formation and billet segregation. Therefore, the Mn content is controlled to be in the range of 0.9 to 1.3 wt%.
V is a precipitation strengthening element, so that the strength and the hardness of the steel rail are improved, but the toughness is greatly reduced while the strength and the hardness of the steel rail are further improved by increasing the content of V, and the content of V is controlled within the range of 0.08-0.15 weight percent.
Cr can form a replacement solid solution with alpha-Fe to play a role in solid solution strengthening, and meanwhile, Cr is a strong carbide forming element, so that the C curve of the steel is shifted to the right, the strength and the hardenability of the steel rail can be obviously improved, the interlayer spacing of pearlite pieces is obviously refined, but the plasticity and the toughness of the steel can be reduced by increasing the Cr content, and therefore, the Cr content is controlled within the range of 0.15-0.30 weight percent.
Nb is one of important microalloy elements in steel, the strength and toughness of the steel are improved mainly by grain refinement and precipitation strengthening, and the temper brittleness of the steel can be reduced, but the high-temperature thermoplasticity of the steel is reduced by excessively high Nb content, and billet hot cracking is easily caused, so the Nb content is controlled within the range of 0.02-0.08 wt%.
B can effectively delay austenite-pearlite transformation and improve hardenability, the hardenability of the steel rail can be obviously improved by adding a trace amount of B into the steel, and a refined pearlite structure is easier to obtain, but when the content of B is too high, the brittleness of the steel rail is easy to increase, the affinity of B and O, N is strong, and nonmetal inclusions are easy to form, so that the content of B is controlled within the range of 0.004-0.008 wt%.
P, S is considered to be a harmful residual element in steel, which can greatly increase the crack sensitivity of steel, increase the low-temperature brittle transition temperature of steel and reduce the low-temperature impact property of steel, therefore, on the premise of not affecting the performance of steel rails, the lower the P, S content is required to be, the better, and the level is controlled to be less than or equal to 0.025 wt% according to the related standard requirements of steel rails at present.
2. The reasons for selecting the above process parameters are as follows:
1) the basic principle of the steel rail online heat treatment process is mainly to perform accelerated cooling treatment on a rolled steel rail, increase the supercooling degree of austenite to pearlite transformation by utilizing the residual heat of the rolled steel rail to perform accelerated cooling, and obtain a pearlite structure which is finer than the interlayer spacing of a hot rolled steel rail plate, so that the strength and the hardness of the steel rail are improved, and the wear resistance is improved. However, after the pearlite lamellar spacing is too fine, the wear resistance of the steel rail is improved, microcracks on the surface layer of the steel rail due to plastic deformation cannot be timely removed, the microcracks are easy to continue to expand, contact fatigue damage is developed, and the service life of the steel rail is influenced. The rail head of the steel rail is mainly of a pearlite structure, and the spacing between pearlite lamella is a main factor determining the mechanical property of the rail head, so that the rail head pearlite lamella spacing is controlled within a certain range by adopting a staged accelerated cooling process, the abrasion and contact fatigue of the steel rail can reach a dynamic balance, namely the steel rail generates abrasion to a certain degree, the geometric relation between the wheel rail is not deteriorated, a fatigue layer on the surface can be removed in time, the development of contact fatigue cracks is inhibited, the rolling contact fatigue and the abrasion are controlled in a proper interval, the rolling contact fatigue and the abrasion can be reasonably matched, and the comprehensive performance of the steel rail can be best exerted.
2) In the heat treatment process of the rail head of the steel rail, pearlite phase transformation is not completed at one time, but the pearlite phase transformation is gradually carried out from the surface to the core part, when the accelerated cooling is started, the surface metal is rapidly cooled, and when the pearlite phase transformation temperature is reached, a pearlite layer is formed on the surface. The cooling speed of the stage 1 is 2-4 ℃/s, aiming at quickly taking away the heat of the rail head surface layer, quickly forming a stable refined pearlite layer, ensuring the surface tread hardness and laying a foundation for the subsequent heat treatment; after the phase transformation of the surface pearlite is finished, the undercooled austenite to be transformed in the interior needs to exchange heat with the outside through the pearlite layer, the cooling speed of a transformation interface of the pearlite and the austenite is lower than that of the surface, the depth of the pearlite layer is gradually increased along with the development of phase transformation towards the interior of a rail head, so that the cooling speed needs to be gradually increased, the cooling speed in the 2 nd stage is 3-5 ℃/s, the cooling speed in the 3 rd stage is 4-6 ℃/s, and the cooling speed is sequentially increased in order to ensure that the cooling speed is basically consistent and the phase transformation driving force of the pearlite tends to be consistent within a certain depth of the surface layer; in the later cooling stage, although the thickness of the pearlite layer is further increased to lengthen a heat dissipation channel to the outside, the heat storage area of the center of the rail head is also remarkably reduced, the total heat capacity is smaller, so that the cooling speed required for obtaining the pearlite structure with the equivalent interlamellar spacing is correspondingly reduced, the cooling speed in the 4 th stage is 3-5 ℃/s, the cooling speed in the 5 th stage is 2-4 ℃/s, the cooling speed is gradually reduced, and finally the pearlite structure with the proper interlamellar spacing is obtained on the rail head.
The invention has the beneficial effects that:
the rail head is accelerated and cooled in stages, the cooling speed and the cooling time of each stage are reasonably distributed, and the pearlite interlayer spacing of the metallographic structure of the rail head is reasonably controlled, so that the development of rail abrasion and rolling contact fatigue can be well coupled, the comprehensive service performance and the service life of the rail are improved, and the production method is simple, strong in operability and easy to popularize and apply.
Drawings
Figure 1 is a photograph of the pearlite interlaminar spacing of a rail according to the invention,
fig. 2 is a schematic diagram of a rail rolling contact wear test.
Detailed Description
The present invention is described in further detail below with reference to specific examples so as to be understood by those skilled in the art.
The steel rail with good coupling of abrasion and rolling contact fatigue comprises the following chemical components in percentage by weight based on the total weight of the steel rail: 0.75-0.88%, Si: 0.60-0.80%, Mn: 0.90-1.30%, V: 0.08-0.15%, Cr: 0.15-0.30%, Nb: 0.02-0.08%, B: 0.004-0.008%, less than or equal to 0.025% of P, less than or equal to 0.025% of S, and the balance of Fe and inevitable impurities.
Based on the formula, the smelting chemical components of the steel rails 1 to 4 are designed according to the formula shown in the table 1.
TABLE 1 chemical composition of the examples
Example 1
The method is carried out according to the conventional steel rail smelting and casting method, and the working procedures comprise converter smelting, LF refining, vacuum treatment and continuous casting. Wherein, the alkalinity of the converter slag is controlled to be 2.6-3.5; when molten steel is discharged about 1/4, alloy such as silicon, manganese, vanadium and the like and carburant are added along with the steel flow, and when the molten steel is discharged to 3/4, the alloy and the carburant are all added; the treatment time of the LF furnace is more than 35 min; RH vacuum degree is less than or equal to 90Pa, pure vacuum treatment time is not less than 20min, casting process is carried out under protection of the whole process to prevent contact with air, and cast steel billet is slowly cooled. Then, the method is carried out according to a conventional steel rail rolling method, the steel billet is sent into a walking beam heating furnace to be heated and heat-preserved, the heating temperature is 1200-1300 ℃, the heat-preservation time is 150-260min, the steel rail is rolled by a universal rolling mill, the initial rolling temperature is 1080-1150 ℃, and the final rolling temperature is 860-900 ℃. The steel rail is subjected to staged online heat treatment, the starting cooling temperature is 760 ℃, the whole rail head cooling process is divided into 5 stages, the cooling time of each stage is 12s, the cooling speed of the 1 st stage is 2.6 ℃/s, the cooling speed of the 2 nd stage is 3.8 ℃/s, the cooling speed of the 3 rd stage is 5 ℃/s, the cooling speed of the 4 th stage is 4.2 ℃/s, the cooling speed of the 5 th stage is 2.4 ℃/s, accelerated cooling is stopped when the temperature of the rail head is reduced to 360 ℃, the rail is naturally cooled to the room temperature, and finally, a vertical composite straightener is adopted to straighten the steel rail.
Example 2
The production method is carried out according to the production method of the example 1, except that the specific process of accelerated cooling after rolling comprises the following steps: the initial cooling temperature is 800 ℃, the whole rail head cooling process is divided into 5 stages, the cooling time of each stage is 10s, the cooling speed of the 1 st stage is 3.2 ℃/s, the cooling speed of the 2 nd stage is 4.0 ℃/s, the cooling speed of the 3 rd stage is 5.5 ℃/s, the cooling speed of the 4 th stage is 3.8 ℃/s, the cooling speed of the 5 th stage is 3.0 ℃/s, when the temperature of the rail head is reduced to 370 ℃, accelerated cooling is stopped, the rail head is naturally cooled to the room temperature, and finally, a vertical composite straightener is adopted to straighten the rail.
Example 3
The production method is carried out according to the production method of the example 1, except that the specific process of accelerated cooling after rolling comprises the following steps: the initial cooling temperature is 720 ℃, the whole rail head cooling process is divided into 5 stages, the cooling time of each stage is 15s, the cooling speed of the 1 st stage is 2.2 ℃/s, the cooling speed of the 2 nd stage is 3.6 ℃/s, the cooling speed of the 3 rd stage is 5.2 ℃/s, the cooling speed of the 4 th stage is 3.5 ℃/s, the cooling speed of the 5 th stage is 2.8 ℃/s, when the temperature of the rail head is reduced to 350 ℃, accelerated cooling is stopped, the rail head is naturally cooled to the room temperature, and finally, a vertical composite straightener is adopted to straighten the rail.
Example 4
The production method is carried out according to the production method of the example 1, except that the specific process of accelerated cooling after rolling comprises the following steps: the initial cooling temperature is 740 ℃, the whole rail head cooling process is divided into 5 stages, the cooling time of each stage is 13s, the cooling speed of the 1 st stage is 3.6 ℃/s, the cooling speed of the 2 nd stage is 4.5 ℃/s, the cooling speed of the 3 rd stage is 5.7 ℃/s, the cooling speed of the 4 th stage is 4.0 ℃/s, the cooling speed of the 5 th stage is 2.5 ℃/s, when the temperature of the rail head is reduced to 380 ℃, accelerated cooling is stopped, the rail head is naturally cooled to the room temperature, and finally, a vertical composite straightening machine is adopted to straighten the rail.
Comparative example 1
The chemical composition and production method of example 1 were followed, except that the specific process of accelerated cooling after rolling was: the cooling temperature is 730 ℃, the rail head is subjected to accelerated cooling at a constant cooling speed, the cooling time is 65s, the cooling speed is 2.0 ℃/s, when the temperature of the rail head is reduced to 350 ℃, the accelerated cooling is stopped, the rail head is naturally cooled to the room temperature, and finally, the steel rail is straightened by adopting a vertical composite straightening machine.
Comparative example 2
The chemical composition and production method of example 1 were followed, except that the specific process of accelerated cooling after rolling was: and (3) starting cooling at 750 ℃, performing accelerated cooling at a constant cooling speed on the rail head, wherein the cooling time is 52s, the cooling speed is 4.5 ℃/s, stopping accelerated cooling when the temperature of the rail head is reduced to 370 ℃, naturally cooling to room temperature, and finally straightening the steel rail by adopting a horizontal and vertical composite straightening machine.
The performance indexes of the steel rails of the examples and the comparative examples, such as tensile strength, tread hardness, metallographic structure and the like, are measured according to the method specified in the national railway industry standard TB/T2344-2012, and the results are shown in Table 2.
TABLE 2 comparison of mechanical properties of examples and comparative examples
In order to verify the comprehensive service performance of the steel rail obtained by the invention, an M-2000 rolling contact wear testing machine is adopted to carry out contact fatigue wear tests on the steel rails of the examples and the comparative examples under the same test conditions. The abrasion weight loss was measured by relative rolling of the cylindrical samples, and the schematic diagram of the test is shown in fig. 2. The upper samples were taken from the rail head areas of the examples and comparative examples, respectively, and the lower samples were wheel steels with a brinell hardness of 380 HB.
The test conditions were as follows:
sample size: the thickness is 8mm, the inner diameter is 10mm, and the outer diameter is 20 mm;
test load: 500N;
rotating speed: the upper sample is 180r/min, and the lower sample is 200 r/min;
slip ratio: 10 percent;
total number of revolutions of the counter mill: 5X 105Next, the process is carried out.
The contact fatigue wear test results are shown in table 3.
TABLE 3 contact fatigue wear test results of examples and comparative examples
| Macroscopic appearance of sample surface | Crack propagation depth to inside of rail head/mum | Weight loss on abrasion/g | |
| Example 1 | Slight fatigue cracking | 30.2 | 1.23 |
| Example 2 | Slight fatigue cracking | 33.5 | 1.05 |
| Example 3 | Slight fatigue cracking | 31.5 | 1.16 |
| Example 4 | Slight fatigue cracking | 34.9 | 1.27 |
| Comparative example 1 | Substantially free of cracks | 12.3 | 2.07 |
| Comparative example 2 | Obvious cracks with peeling off and chipping | 67.1 | 0.55 |
From the above table, it can be seen that: the steel rails obtained in the embodiments 1-4 have good mechanical properties and metallographic structures, the abrasion and contact fatigue of the steel rails show good coupling in a rolling contact abrasion test, and the abrasion weight loss amount, the appearance and the depth of fatigue cracks are controlled in a reasonable range; the rail of comparative example 1 has a large pearlite interlamellar spacing, low strength hardness, insignificant fatigue cracks, but significantly increased wear, and the rail of comparative example 2 has a small pearlite interlamellar spacing, high strength hardness, good wear control, but significantly increased fatigue cracks, and increased crack propagation depth. In contrast, the method of the present invention can achieve good coupling between wear and rolling contact fatigue and improve the comprehensive service life of the steel rail on the premise of ensuring the structure and mechanical properties of the heat-treated steel rail, wherein the steel rail obtained in example 3 has the best mechanical properties and metallographic structure.
Other parts not described in detail are prior art. Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and the embodiments are within the scope of the present invention.
Claims (8)
1. A rail with good coupling of abrasion and rolling contact fatigue is characterized in that: based on the total weight of the steel rail, the steel rail comprises the following chemical components in percentage by weight: 0.75-0.88%, Si: 0.60-0.80%, Mn: 0.90-1.30%, V: 0.08-0.15%, Cr: 0.15-0.30%, Nb: 0.02-0.08%, B: 0.004-0.008%, less than or equal to 0.025% of P, less than or equal to 0.025% of S, and the balance of Fe and inevitable impurities.
2. A rail having a good coupling of wear and rolling contact fatigue according to claim 1, wherein: the steel rail comprises the following chemical components in percentage by weight: 0.76-0.86%, Si: 0.62-0.77%, Mn: 0.98-1.30%, V: 0.08-0.12%, Cr: 0.15-0.25%, Nb: 0.05-0.08%, B: 0.006-0.007%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, and the balance of Fe and inevitable impurities.
3. A rail having a good coupling of wear and rolling contact fatigue according to claim 1, wherein: the metallographic structure of the steel rail is pearlite and a small amount of ferrite, the interlayer spacing of pearlite is 150-380 nm, the tensile strength of the steel rail is more than or equal to 1250MPa, the elongation is 11-13%, and the brinell hardness of a rail head tread is 350-380 HB.
4. A rail having good coupling of wear and rolling contact fatigue according to claim 1, 2 or 3, wherein: the steel rail comprises the following chemical components in percentage by weight: 0.78%, Si: 0.70%, Mn: 1.26%, V: 0.08%, Cr: 0.18%, Nb: 0.08%, B: 0.008%, P: 0.013%, S: 0.007% and the balance of Fe and inevitable impurities.
5. A method for producing a steel rail according to claim 1 or 2, which comprises eight steps of converter smelting, LF refining, vacuum treatment, continuous casting, billet heating, rolling, accelerated cooling and straightening to obtain the steel rail; the method is characterized in that: the rolled steel rail is subjected to on-line accelerated cooling treatment, and in the cooling process,
the rolled steel rail stays on the roller way, when the surface temperature of the steel rail reaches 700-820 ℃, accelerated cooling is started, the whole cooling process is divided into 5 cooling stages, and the cooling speed of each stage is respectively as follows:
the cooling speed of the 1 st stage is 2-4 ℃/s, the cooling speed of the 2 nd stage is 3-5 ℃/s, the cooling speed of the 3 rd stage is 4-6 ℃/s, the cooling speed of the 4 th stage is 3-5 ℃/s, the cooling speed of the 5 th stage is 2-4 ℃/s, when the temperature of the rail head is reduced to 380 ℃ of 350-.
6. A method for producing a steel rail according to claim 5, wherein: in the cooling process, the cooling speed of each stage is respectively as follows:
the cooling speed of the 1 st stage is 2.5-3.5 ℃/s, the cooling speed of the 2 nd stage is 3.5-4.5 ℃/s, the cooling speed of the 3 rd stage is 4.5-5.5 ℃/s, the cooling speed of the 4 th stage is 3.5-4.5 ℃/s, the cooling speed of the 5 th stage is 2.5-3.5 ℃/s, when the temperature of the rail head is reduced to 360-370 ℃, the accelerated cooling is stopped, and finally the rail head is naturally cooled to the room temperature.
7. A method for producing a steel rail according to claim 5 or 6, wherein: in the cooling process, the accelerated cooling time of each stage is equal and is 10-15s, and the absolute value of the cooling speed difference between adjacent cooling stages is controlled within 2 ℃/s.
8. A method for producing a steel rail according to claim 5 or 6, wherein: the rail is subjected to accelerated cooling heat treatment through the length, the same cooling speed is applied to the rail bottom while the rail head is subjected to accelerated cooling, and when the rail head stops being subjected to accelerated cooling, the rail bottom stops being cooled correspondingly.
Priority Applications (2)
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| CN202111033706.4A CN113930667B (en) | 2021-09-03 | 2021-09-03 | Rail with good coupling of abrasion and rolling contact fatigue and production method thereof |
| PCT/CN2022/096732 WO2023029630A1 (en) | 2021-09-03 | 2022-06-02 | Steel rail in which abrasion and rolling contact fatigue are well coupled and production method therefor |
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| CN202111033706.4A CN113930667B (en) | 2021-09-03 | 2021-09-03 | Rail with good coupling of abrasion and rolling contact fatigue and production method thereof |
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| CN114606377A (en) * | 2022-02-07 | 2022-06-10 | 包头钢铁（集团）有限责任公司 | Heat treatment method for removing ferrite net structure in steel rail |
| CN114672730A (en) * | 2022-03-18 | 2022-06-28 | 武汉钢铁有限公司 | Rolling contact fatigue resistant steel rail for passenger-cargo mixed transportation railway and production method thereof |
| WO2023029630A1 (en) * | 2021-09-03 | 2023-03-09 | 武汉钢铁有限公司 | Steel rail in which abrasion and rolling contact fatigue are well coupled and production method therefor |
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| CN113930667B (en) | 2022-11-01 |
| WO2023029630A1 (en) | 2023-03-09 |
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