CN113789473B - High-strength wear-resistant steel rail for small-radius curve of high-speed railway and production method thereof - Google Patents
High-strength wear-resistant steel rail for small-radius curve of high-speed railway 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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- 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
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
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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
- 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
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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
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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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
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01B—PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS
- E01B5/00—Rails; Guard rails; Distance-keeping means for them
- E01B5/02—Rails
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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 relates to a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway, which comprises the following chemical components in percentage by weight: c: 0.55 to 0.82 percent, Si: 0.12-0.62%, Mn: 0.60% -1.60%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, Cr: 0.01 to 0.15 percent of the total weight of the alloy, less than or equal to 0.20 percent of Mo, Ni and Cu, and the balance of Fe and inevitable impurities; the steel rail structure is composed of fine pearlite and trace ferrite, and the pearlite lamellar spacing of the rail head is 80-100 nm. According to the invention, a high-strength high-toughness wear-resistant steel rail which is excellent in wear resistance and contact fatigue resistance and suitable for high-speed small-radius curve laying is produced by optimizing the design of conventional alloy elements, optimizing the rolling temperature, controlling the rolling in a recrystallization region, carrying out online heat treatment by utilizing the residual temperature of the steel rail after rolling and other technical means.
Description
Technical Field
The invention relates to the technical field of heavy rails, in particular to a 60kg/m grade high-strength wear-resistant steel rail for a high-speed railway trunk line small-radius curve section (the radius is less than 300 meters) with the speed per hour exceeding 250 kilometers and a production method thereof.
Background
With the rapid development of economy, safe, high-speed and efficient railway traffic brings convenience to people's trip, wherein the high-speed railway gradually becomes one of the favorite vehicles of people. The steel rail is used as a key part for guiding the train to run and transmitting the wheel load to the track bed, and the quality of the steel rail directly influences the operation efficiency, the driving speed and the driving safety of the line. In recent years, China's high-speed railways have undergone a historical period of development, high-speed railway systems with the speed of tens of thousands of kilometers per hour of 250km and 350km have been built, and an eight-transverse eight-longitudinal' high-speed railway network is basically formed. As the axle weight of a high-speed train is light (generally 11-15t), and the strength grade of the steel rail is required to be designed at a low grade due to safety considerations, 880MPa grade U71Mn hot rolled steel rail is commonly used previously. However, in recent years, due to the fact that the train has high running density and high running speed, the rail has very high abrasion speed at a small-radius curve, the service life of the rail is greatly shortened, the replacement frequency of the rail is increased, and the running efficiency of the high-speed train is influenced. After comprehensive evaluation, the method also provides the method that the steel rail with higher strength is paved at the small-radius curve to solve the problem of serious well grinding of the steel rail.
In order to solve the serious problem of the abrasion of the small-radius curve section steel rail and the problem of rolling contact fatigue stripping and block falling caused by abrasion, a plurality of measures are proposed at home and abroad: firstly, in the United states, Canada and other places in North America, the three sections of circular arcs at the gauge angle are optimized into four sections of circular arcs, so that the contact stress of the wheel rail is smaller, and the serious problem of small radius curve abrasion is reduced; and the second is the 60N steel rail with a new rail head profile which is researched and designed in order to improve the contact relation of the rails, reduce the contact stress of the rails and improve the dynamic performance of the vehicle, as proposed in the '60N steel rail profile design and experimental research' published by Zhouqing leap, Zhanghua and the like. Practical application shows that the method has good effect in high-speed straight line and large-radius curve segments, while the method has unobvious effect in small-radius curve segments and still has serious abrasion.
In recent years, expert scholars have conducted studies on reinforcement of a rail base, and have achieved certain effects by solving the above problems by improving hardness and strength, but all have certain problems. For example, the Chinese patent with the publication number of CN104195433B discloses a pearlite steel rail with high strength and toughness and a production method thereof: design C with the following chemical composition: 0.75% -0.84%, Si: 0.30% -0.80%, Mn: 0.50% -1.50%, V: 0.04% -0.12%, Ti: 0.004-0.02 percent, and satisfies that V +10Ti is more than or equal to 0.10 percent and less than or equal to 0.25 percent, N is less than or equal to 30ppm, P is less than or equal to 0.020 percent, S is less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities, and the high-strength and high-toughness pearlitic steel rail is obtained through heat treatment; however, a large amount of V, Ti microalloy elements are added into the steel rail, so that the production cost is greatly improved, and meanwhile, the tensile strength is less than 1120MPa, so that the requirement on the strength of the small-radius curve steel rail cannot be met.
Chinese patent application publication No. CN110607488A discloses "an on-line heat-treated steel rail for high-speed railway and manufacturing method thereof", which adopts the following chemical components to design C: 0.68-0.78%, Si: 0.30-0.58%, Mn: 0.50% -0.80%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, Cr: 0.10-0.40%, V: 0.02-0.05%, and the balance of Fe and inevitable impurities. However, the manufacturing method does not describe the cooling position of the rail and the air injection position of the nozzle, which is particularly easy to cause uneven cooling of the rail and great fluctuation of strength and hardness; meanwhile, the steel rail is cooled at a large cooling speed on the surface layer, which shows that the rail web is also cooled quickly, so that a large amount of martensite abnormal structures are generated in the rail web area.
The Chinese patent with the publication number of CN105063490B discloses a steel rail for a high-speed railway and a production method thereof: the steel rail contains 0.63-0.73 wt% of carbon, 0.1-0.5 wt% of silicon, 0.7-1.2 wt% of manganese, 0.05-0.3 wt% of chromium, less than 0.04 wt% of vanadium, less than 0.025 wt% of phosphorus, less than 0.025 wt% of sulfur and 96.98-98.52 wt% of iron, and is obtained by heat treatment to have high strength, high wear resistance and high contact fatigue resistance; but the tensile strength of the steel rail exceeds 1300MPa, belongs to the strength grade of heavy-duty railway steel rails, is obviously not suitable for high-speed railways, and although the steel rail has good wear resistance, the contact fatigue resistance is suddenly reduced due to the overhigh wear resistance at the small-radius curve part of the high-speed railway, and the steel rail has serious risks of serious stripping and chipping and crack initiation.
Chinese patent with publication No. CN107675083B discloses a strong and tough pearlite steel rail and its manufacturing method: the chemical components of C0.70-0.87%, Si 0.15-0.45%, Mn 0.60-1.00%, Cr 0.10-0.40%, at least one of V, Nb and Ti, V0.02-0.10% when V is contained, Ti 0.001-0.030% when Ti is contained, Nb 0.005-0.08% when Nb is contained, and the balance of Fe and inevitable impurities are designed; and heat treatment is carried out to obtain the pearlite steel rail with high toughness. However, a large amount of V, Ti and Nb microalloy elements are added in the technical scheme, so that the production cost is greatly improved. Meanwhile, the tensile strength exceeds 1249MPa, belongs to the strength grade of heavy-duty railway steel rails, and is not suitable for high-speed railways.
The Chinese patent with the publication number of CN101921950B discloses a steel rail for high-speed and quasi-high-speed railways: the high-speed steel rail is prepared by designing chemical components of 0.40-0.64% of C, 0.10-1.00% of Si, 0.30-1.50% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, less than or equal to 0.005% of Al, more than 0 and less than or equal to 0.05% of rare earth elements, more than 0 and less than or equal to 0.20% of at least one of V, Cr and Ti in total, and the balance of Fe and inevitable impurities, and carrying out heat treatment to obtain the high-speed steel rail. However, the tensile strength of the steel rail obtained by the method is less than 1000MPa, the steel rail is not suitable for a small-radius curve section, a large amount of microalloy noble metal elements are added, and the cost is obviously increased.
In order to solve the problems, the contradiction that the wear resistance and the rolling contact fatigue strength of the small-radius curve steel rail of the high-speed railway cannot be obtained simultaneously is balanced, the toughness and the wear resistance of the steel rail are improved, and the service life is prolonged; the invention realizes technical breakthrough on the basis of a large number of tests, and produces the high-strength and high-toughness wear-resistant steel rail with excellent wear resistance and excellent contact fatigue resistance through a reasonable heat treatment process on the premise of not adding expensive micro-alloy elements by optimizing component design, and the steel rail is suitable for being laid on a small-radius curve segment, so that a high-speed train can run stably, quickly and safely, and the service life of the steel rail is obviously prolonged; and the steel rail has higher cost performance and good application prospect.
Disclosure of Invention
The invention provides a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway and a production method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway comprises the following chemical components in percentage by weight: c: 0.55-0.82%, Si: 0.12-0.62%, Mn: 0.60% -1.60%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, Cr: 0.01 to 0.15 percent of the total weight of the alloy, less than or equal to 0.20 percent of Mo, Ni and Cu, and the balance of Fe and inevitable impurities; the steel rail structure is composed of pearlite and ferrite, wherein the volume fraction of the pearlite is not less than 98%, the volume fraction of the ferrite is not more than 2%, and rail head pearlite is fine pearlite with the interlamellar spacing of 80-100 nm.
A production method of a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway comprises the following steps:
(1) smelting, refining and continuous casting;
(2) heating a casting blank; stacking and slowly cooling the casting blanks to room temperature, then charging into a furnace and heating, wherein the heating temperature is 1250-1300 ℃, and the heat preservation time is 2-4 hours; ensuring that the casting blank is always in a reducing atmosphere in the heating process;
(3) rolling a steel rail; carrying out three-stage rolling after descaling the casting blank by using high-pressure water; the rolling temperature of the first stage after cogging is 1190-1250 ℃, the temperature of a rolled piece discharged from a rolling mill is controlled to be 1080-1150 ℃, and the reduction rate of the section of the rolled piece is 30-50%; rolling in the second stage, wherein the temperature of the rolled piece exiting the rolling mill is 1000-1050 ℃, and the reduction rate of the section of the rolled piece is 40-65%; the temperature of rolled pieces entering the last rolling mill in the third stage is 940-980 ℃, the finishing temperature is 885-920 ℃, and the reduction rate of the section of the rolled pieces is 15-35%;
(4) performing waste heat treatment on the rolled steel rail; adopting a normalizing treatment mode, specifically: cooling the rail head to the final cooling temperature of 670-700 ℃ through water mist, then enabling the rail head to enter a heat treatment unit, cooling the rail head to the final cooling temperature of 440-470 ℃ at the cooling speed of 3-8 ℃/s through the cooperation of water vapor and compressed air, and blowing the centers of the rail web and the rail bottom with compressed air or water vapor at the cooling speed of 0.5-1 ℃/s all the time in the process that the steel rail enters the heat treatment unit, so as to ensure that the temperature of the steel rail is not higher than 510 ℃; air cooling to room temperature after normalizing treatment;
(5) the heat treated steel rail is straightened by horizontal and vertical compound, subjected to ultrasonic flaw detection, sized, inspected and warehoused.
In the step (1), molten iron is subjected to desulfurization pretreatment, smelted by using a converter or an electric furnace, and ferrosilicon is deoxidized; adding lime into LF refining for further desulfurization, wherein the refining time is 20-30 minutes; and then RH vacuum degassing treatment or VD vacuum degassing treatment is adopted, and the vacuum treatment time is 30-40 minutes.
And during LF refining, the addition amount of lime is 4-5 kg per ton of steel.
In the step (1), the continuous casting blank is a large-section casting blank with the section size of 280-320 mm multiplied by 380-410 mm.
And (4) rolling the steel rail by adopting a three-stand rolling mill, a five-stand rolling mill or a seven-stand rolling mill in the step (3).
The tensile strength Rm of the steel rail is 1140-1195 MPa, the yield strength Rp0.2 is 701-727 MPa, and the elongation A is more than or equal to 12.5 percent; rail head surface hardnessThe degree is 365-395 HB, and A of each hardness line of the cross section of the rail head 1 、B 1 、C 1 、D 1 、E 1 Point hardness is not less than 37HRC, A of each hardness line of the cross section of the rail head 5 、B 4 、C 4 、D 3 、E 3 The point hardness is more than or equal to 35 HRC; impact absorption energy AK of normal temperature impact test U2 Not less than 41J, when the crack strength factor Deltak is 10MPam 1/2 When the crack propagation rate da/dN is 1.5-2.0, and when the crack strength factor Deltak is 13.5MPam 1/2 The crack propagation rate da/dN is 6 to 10.5.
The steel rail is 60kg/m steel rail.
Compared with the prior art, the invention has the beneficial effects that:
1) the method has the following two characteristics in the aspects of chemical composition design and alloy element selection:
firstly, the alloy cost is reduced; according to the invention, high-cost microalloying elements niobium, vanadium and titanium are not added, the total content of added molybdenum, nickel and copper is not more than 0.2%, and the recrystallized and rolled extremely refined grains are selected through component design and process optimization, so that the performance loss caused by low alloy content is compensated, and the production cost is greatly reduced; in addition, the molybdenum, the nickel and the copper are added in the invention, so that a large amount of high-density distortion areas are introduced when the recrystallization areas are subjected to large deformation, the toughness and the plasticity and the comprehensive performance of the steel rail are high, and the technical limitation that the performance is improved by increasing the alloy content in one way is broken through;
secondly, the maximum function of chemical components in the recrystallization rolling process is exerted; by means of fine grain strengthening, dislocation and substructure strengthening, the recrystallization temperature range is obviously increased by reasonably adding carbon, silicon and manganese elements, rolling in a recrystallization zone is ensured, a large number of high-density distortion zones can be introduced during rolling in the recrystallization zone, so that the toughness and plasticity of the steel rail matrix are greatly improved, and the strength is properly increased;
2) on the basis of reasonable design of chemical components, an online heat treatment process, namely a steel rail post-rolling waste heat treatment process is introduced, on the basis of recrystallization rolling refined grains, the growth of tissue austenite grains is continued in a rapid cooling mode, the grains are further refined, a pearlite structure with a fine structure is obtained, and the steel rail has excellent toughness;
3) through the organic combination of alloying element addition, recrystallization rolling and heat treatment processes, the steel rail obtains high strength and toughness and high wear resistance suitable for a high-speed curve section under the condition of low alloy, the structure performance meets the use requirement, and the aim of reducing the cost of alloy is achieved through a process optimization mode;
5) the on-line heat treatment process fully realizes the effective matching of water mist, compressed air and water vapor, breaks the unicity and limitation of the prior art and ensures that the steel rail structure has stable performance.
6) By chemical composition design and the combined action of smelting and rolling, the recrystallization temperature range is successfully widened, the large deformation rolling in a recrystallization zone is realized, the steel rail tissue is obviously refined, and the industrial production is easy to realize; meanwhile, the crystal grains are further refined by matching with an online heat treatment process, and the high-strength, high-toughness, wear-resistant and anti-stripping pearlitic steel rail suitable for high-speed small-radius curves is obtained; the steel rail structure is composed of fine pearlite and micro ferrite; a GPM-30 rolling contact fatigue test bed is adopted to carry out friction wear and contact fatigue tests, and after 25 ten thousand total wear tests, the wear of the steel rail is 0.8573-0.9897 g, and the number of stripped blocks is 0.
Drawings
FIG. 1 is a metallographic structure photograph of a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway according to the present invention.
FIG. 2 is a schematic representation of the cross-sectional hardness of the rail of the present invention.
Detailed Description
The invention relates to a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway, which comprises the following chemical components in percentage by weight: c: 0.55 to 0.82 percent, Si: 0.12-0.62%, Mn: 0.60% -1.60%, P: less than or equal to 0.025 percent, S: less than or equal to 0.015 percent, Cr: 0.01 to 0.15 percent of the total weight of the alloy, less than or equal to 0.20 percent of Mo, Ni and Cu, and the balance of Fe and inevitable impurities; the steel rail structure is composed of pearlite and ferrite (shown in figure 1), wherein the volume fraction of the pearlite is more than or equal to 98%, the volume fraction of the ferrite is less than or equal to 2%, and rail head pearlite is fine pearlite with the interlamellar spacing of 80-100 nm.
A production method of a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway comprises the following steps:
(1) smelting, refining and continuous casting;
(2) heating a casting blank; stacking and slowly cooling the casting blanks to room temperature, then charging and heating, wherein the heating temperature is 1250-1300 ℃, and the heat preservation time is 2-4 hours; ensuring that the casting blank is always in a reducing atmosphere in the heating process;
(3) rolling a steel rail; carrying out three-stage rolling after descaling the casting blank by using high-pressure water; the rolling temperature of the first stage after cogging is 1190-1250 ℃, the temperature of a rolled piece taken out of a rolling mill is controlled to be 1080-1150 ℃, and the reduction rate of the section of the rolled piece is 30-50%; rolling in the second stage, wherein the temperature of the rolled piece exiting the rolling mill is 1000-1050 ℃, and the reduction rate of the section of the rolled piece is 40-65%; the temperature of rolled pieces entering the last rolling mill in the third stage is 940-980 ℃, the finishing temperature is 885-920 ℃, and the reduction rate of the section of the rolled pieces is 15-35%;
(4) performing waste heat treatment on the rolled steel rail; adopting a normalizing treatment mode, specifically: cooling the rail head to the final cooling temperature of 670-700 ℃ through water mist, then enabling the rail head to enter a heat treatment unit, cooling the rail head to the final cooling temperature of 440-470 ℃ at the cooling speed of 3-8 ℃/s through the cooperation of water vapor and compressed air, and blowing the centers of the rail web and the rail bottom with compressed air or water vapor at the cooling speed of 0.5-1 ℃/s all the time in the process that the steel rail enters the heat treatment unit, so as to ensure that the temperature of the steel rail is not higher than 510 ℃; air cooling to room temperature after normalizing treatment;
(5) the heat treated steel rail is straightened by horizontal and vertical compound, subjected to ultrasonic flaw detection, sized, inspected and warehoused.
In the step (1), molten iron is subjected to desulfurization pretreatment, smelted by using a converter or an electric furnace, and ferrosilicon is deoxidized; adding lime into LF refining for further desulfurization, wherein the refining time is 20-30 minutes; and then RH vacuum degassing treatment or VD vacuum degassing treatment is adopted, and the vacuum treatment time is 30-40 minutes.
And during LF refining, the addition amount of lime is 4-5 kg per ton of steel.
In the step (1), the continuous casting blank is a large-section casting blank with the section size of 280-320 mm multiplied by 380-410 mm.
And (4) rolling the steel rail by adopting a three-stand rolling mill, a five-stand rolling mill or a seven-stand rolling mill in the step (3).
The tensile strength Rm of the steel rail is 1140-1195 MPa, the yield strength Rp0.2 is 701-727 MPa, and the elongation A is more than or equal to 12.5 percent; the surface hardness of the rail head is 365-395 HB, and as shown in figure 2, A of each hardness line of the cross section of the rail head 1 、B 1 、C 1 、D 1 、E 1 Point hardness is not less than 37HRC, A of each hardness line of the cross section of the rail head 5 、B 4 、C 4 、D 3 、E 3 The point hardness is more than or equal to 35 HRC; impact absorption energy AK of normal temperature impact test U2 Not less than 41J, when the crack strength factor Deltak is 10MPam 1/2 When the crack propagation rate da/dN is 1.5-2.0, and when the crack strength factor Deltak is 13.5MPam 1/2 The crack propagation rate da/dN is 6 to 10.5.
The steel rail is 60kg/m steel rail.
The technical advancement of the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway and the production method thereof is as follows: firstly, the wear resistance of the steel rail is improved, so that the steel rail has good matching of wear resistance and contact fatigue resistance in a small-radius curve; secondly, the component design adopts a C-Si-Mn system, and micro-alloy elements of niobium, vanadium and titanium are not added, so that the alloy cost is reduced; thirdly, optimizing the design of the rolling process and proposing rolling in a recrystallization zone; performing on-line heat treatment by using the residual heat of the rolled steel rail, further refining crystal grains, controlling the interval between pearlite lamellae of the structure to be 80-100 nanometers, improving the strength and the hardness of the steel rail, ensuring the toughness to be improved, and meeting the performance requirements of a small-radius curve section of a high-speed railway on the steel rail structure; fifthly, the method adopts the waste heat treatment after the steel rail is rolled, also called on-line heat treatment, and the steel rail obtained by the method is also called on-line heat treatment.
The invention relates to a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway, which comprises the following chemical components in percentage by weight:
c is the most basic element of the steel matrix strengthening type, and is mainly used for ensuring the strength and the hardness of the matrix, and for the steel rail disclosed by the invention, when the content of C is lower than 0.55%, other alloy elements cannot make up the defects of strength and hardness, and simultaneously, the hardenability and the hardenability are poor, so that the steel rail has too low strength and hardness, and the wear resistance is remarkably reduced; when the content of C is higher than 0.82 percent, the hardenability and the hardenability are too high by the process of the invention, and a martensite abnormal structure is easy to generate. Therefore, the content of C is 0.55-0.82%.
Si is a main deoxidizing element and a strength-improving solid solution strengthening element, and the Si mainly serves as the solid solution strengthening element existing in ferrite and austenite to improve the strength of the structure, improve the toughness and contribute to improving the recrystallization interval and recrystallization rolling; if the Si content is less than 0.12%, the solid solution strengthening effect cannot be provided, and if the Si content is more than 0.62%, the toughness and plasticity of the rail are reduced, and the transverse performance of the rail is deteriorated. Therefore, the Si content is selected to be 0.12-0.62%.
Mn is a phase-change type strengthening element with the highest cost performance and is a carbide forming element, and can partially replace Fe atoms after entering a cementite to increase the hardness of the carbide; under the condition of no microalloy, Mn can well improve the hardenability and the hardenability in the heat treatment process and increase the strength of the steel rail. Researches show that when the content of manganese is lower than 0.60%, the manganese can not be matched with the heat treatment process, and even the hardness of the steel rail can be reduced; when the manganese content is more than 1.60%, hardenability is too strong, and a martensitic abnormal structure is easily generated. Therefore, the Mn content is 0.60-1.60% in the invention.
P is a harmful element of the steel rail, and is easy to cause segregation. On the premise of ensuring the steelmaking conditions, the steelmaking cost and the like, the P content is required to be less than or equal to 0.025 percent.
S is a harmful element of the steel rail, is easy to form non-metal inclusion MnS to cause quality defect, and is also a main element generating hot brittleness in the hot rolling process, so the lower the S content is, the better the S content is on the premise of ensuring that unnecessary cost is not increased, and the S content is required to be less than or equal to 0.015 percent.
Cr is used as a medium carbide forming element, can uniformly distribute carbides in steel, reduce the size of the carbides and improve the wear resistance of the steel rail. When the chromium content is less than 0.01%, carbide distribution cannot be made uniform; when the chromium content is more than 0.15%, the toughness of the rail is significantly reduced. Therefore, the Cr content is selected to be 0.01-0.15%.
The main functions of the elements Mo, Ni and Cu in the invention are to enlarge the austenite region, promote the recrystallization temperature range, reduce the growth trend of recrystallized grains and achieve the purpose of fine grains of the steel rail to strengthen toughness and plasticity. However, the sum of Mo, Ni and Cu elements is not more than 0.20%, and if not, the above effects are not achieved, and the comprehensive performance of the rail is deteriorated. Therefore, Mo, Ni and Cu are selected to be less than or equal to 0.20 percent.
On the basis of the above component design, in order to realize the purpose of the invention, the high-strength and high-toughness steel rail is produced by matching with a specific smelting process, a heating process, a rolling process and a heat treatment process; the rolling process is the first means for refining the steel rail structure, namely the controlled rolling of a recrystallization zone of the steel rail; the second means of the invention is to refine the crystal grains again through the heat treatment process to obtain the high-strength and high-toughness steel rail; the combination of the two is the technical core of the invention. The whole process design of the invention is tightly combined with the component design, effectively realizes the purpose of improving the obdurability of the steel rail under the conventional element condition, ensures that the comprehensive performance of the steel rail is excellent, solves the problem of poor wear resistance of the steel rail paved on a small-radius curve section of a high-speed railway at present, and simultaneously obviously reduces the alloy cost. The production process and the effect are as follows:
(1) smelting, refining and continuous casting: the molten iron is subjected to desulfurization pretreatment, smelted by a converter or an electric furnace, and the ferrosilicon is deoxidized; performing LF refining to further remove sulfur and protect alloy components, wherein the addition amount of lime is 4-5 kg per ton of steel, and the aim is to ensure that the sulfur content is reduced to below 0.015 percent; the refining time is 20-30 minutes, so that the slag is fully floated, the molten steel is purer, the components are finer, and the quality is improved; and then carrying out vacuum degassing, wherein RH vacuum degassing treatment or VD vacuum degassing treatment can be selected, and the vacuum treatment time is 30-40 minutes, so that the hydrogen content is not more than 1.5ppm (hydrogen induced cracking is reduced), the oxygen content is not more than 20ppm (the content and the size of oxide impurities are reduced), and the final components are finely adjusted to be within the target range of the invention. The beneficial effects of the invention can be realized only by the above treatment mode, and the high-speed steel rail with high toughness, plasticity and contact fatigue resistance can be produced by matching with the subsequent process. And finally, continuously casting to obtain a large-section casting blank with the section size of 280-320 mm multiplied by 380-410 mm, so as to realize large-square-blank large-reduction rolling, ensure that the compression ratio is not less than 9:1 when rolling the steel rail and ensure that the steel rail with the structure performance meeting the requirements can be rolled.
(2) Heating a casting blank: the casting blanks need to be stacked and slowly cooled to room temperature, and hot charging and hot conveying are strictly forbidden, so that microcracks on the surfaces and corners of the casting blanks are reduced, the surface quality is ensured, and the surface quality and the internal quality of the rolled steel rail meet the requirements of high-speed steel rails. Charging the cold casting blank into a furnace for heating, wherein the heating temperature is 1250-1300 ℃, the heat preservation time is 2-4 hours, and the heating mode is selected to provide temperature guarantee for subsequent rolling in a recrystallization zone; the oxidation of casting blank can cause the decarbonization layer of the steel rail to exceed 0.1mm, in order to ensure that the decarbonization layer of the rolled steel rail is not more than 0.1mm, the oxidation of the casting blank is reduced by selecting the mode of brushing the coating on the casting blank in the heating process, or the oxidation of the casting blank is reduced by selecting the mode of strictly configuring furnace gas (selecting one or two of natural gas and air gas), or the two modes are adopted to reduce the oxidation of the casting blank.
(3) Rolling steel rails: and descaling the casting blank by high-pressure water, and rolling the casting blank into a steel rail by adopting a three-stand rolling mill, a five-stand rolling mill or a seven-stand rolling mill. The first rolling temperature after cogging is 1190-1250 ℃, the temperature of a rolled piece out of a rolling mill is controlled to be 1080-1150 ℃ after multi-pass (preferably 5 passes) high reduction rolling, and meanwhile, the section reduction rate of the rolled piece is 30-50%, so that a large amount of dislocation is formed in the rolled blank, and a nucleation point is created for subsequent austenite recrystallization nucleation; most importantly, the temperature is an optimal temperature area for changing the form of the manganese sulfide of the heavy rail on the basis of the chemical composition design, the slender manganese sulfide is broken through dislocation climbing in rolling to form a spindle-shaped fine shape, the internal quality of the steel rail is obviously improved, and the method is also one of innovative technologies in the rolling link. The temperature of a rolled piece entering a rolling mill is not controlled during secondary rolling, but the temperature of the rolled piece exiting the rolling mill after multi-pass rolling (preferably 3 passes) is ensured to be 1000-1050 ℃, and meanwhile, the section reduction rate of the rolled piece is 40-65%; the dislocation of the steel rail which is rolled again under large pressure is complicated, and energy is further accumulated; the rolled piece enters the last rolling mill at 940-980 ℃ to be rolled into a steel rail, meanwhile, the section reduction rate of the rolled piece is 15-35%, and the final rolling temperature is 885-920 ℃. The rolling of the last-frame rolling mill is ensured to be started at the temperature of 930-980 ℃, and the temperature interval is the austenite recrystallization zone of the steel rail, which is the technical core and the second innovation of the rolling process; during recrystallization, austenite forms large-area recrystallization nucleation on dislocation accumulated in the previous period, and enters final rolling when the austenite does not grow in time, so that recrystallization grains are completely crushed and refined, and austenite grains are obviously refined; after the process, the finishing rolling temperature is controlled to be 885-920 ℃, namely a recrystallization temperature interval is avoided, crystal grains do not grow up and smoothly enter a phase transformation area to form pearlite and micro ferrite with fine tissues. And finally, the steel rail structure is composed of fine pearlite and micro ferrite, wherein the volume fraction of the pearlite is more than or equal to 98%, the volume fraction of the ferrite is less than or equal to 2%, and the pearlite lamellar spacing of the rail head is 80-100 nanometers.
(4) Performing heat treatment on the rolled steel rail after heat treatment (namely on-line heat treatment of the steel rail): the invention adopts a heat treatment unit, the heat treatment mode is 'steel rail normalizing', namely compressed air, water mist and water vapor are used as cooling media to cool the steel rail, and nozzles are adopted to spray the cooling media to the railhead tread, the railhead fillet, the two sides of the railhead to the lower jaw, the rail web center and the rail bottom center of the steel rail, so as to ensure uniform cooling. The rail head tread, the rail head fillet and the positions from the two sides of the rail head to the lower jaw are cooled by matching air and water mist, and the aim is to refine crystal grains so that the rail head achieves the strength and hardness required by the invention. The rail web and the rail bottom adopt a wind spraying mode, and the purpose is to prevent the rail head from self tempering and softening caused by overhigh temperature at other positions except the rail head of the steel rail from returning to the rail head. The specific cooling process is as follows: the rail head of the rolled steel rail is cooled to the final cooling temperature of 670-700 ℃ through water mist, then the rail head enters a heat treatment unit, the rail head is cooled to the final cooling temperature of 440-470 ℃ at the speed of 3-8 ℃/s in a water vapor and compressed air matching mode, and the center of the rail web and the rail bottom is always blown by compressed air or water vapor at the cooling speed of 0.5-1 ℃/s in the process of entering the heat treatment unit, so that the temperature return of the steel rail is not more than 510 ℃. After heat treatment, the rail is air cooled to room temperature.
(5) The steel rail after heat treatment is straightened by horizontal and vertical compounding, subjected to ultrasonic flaw detection, sized, inspected and warehoused.
The friction wear test and the contact fatigue test of the steel rail specifically comprise the following steps: adopting a GPM-30 rolling contact fatigue test bed, wherein the shape and the size of a sample are as follows: the test piece is an annular test piece with the thickness of 10mm, the outer diameter of 60mm and the inner diameter of 30mm, wherein the test piece for the friction wear test is a smooth surface, and a groove with the height of 5mm is arranged in the center of the surface of the test piece for the rolling contact fatigue test; test load: 1000 KN; slip: 5 percent; material of the opposite grinding sample: wheel steel with the hardness of 320-340 HB; rotation rate: 220 revolutions per minute; total number of wear cycles: 25 ten thousand times. The fatigue crack growth rate test was performed according to the TB/T2344-2012 standard.
The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples.
[ examples ] A
The chemical components, production process parameters, mechanical properties, wear and contact fatigue test results, crack propagation rates and other values of the steel rails of the examples and comparative examples are shown in tables 1 to 5:
TABLE 1 chemical composition of rails
TABLE 2 refining Process parameters
TABLE 3 heating and Rolling Process parameters
TABLE 4 Online Heat treatment (post-Rolling residual Heat treatment) Process parameters
TABLE 5 mechanical Properties, texture composition, crack propagation Rate, abrasion, contact fatigue resistance of the rails
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (7)
1. A production method of a high-strength wear-resistant steel rail for a small-radius curve of a high-speed railway is characterized in that the steel rail comprises the following chemical components in percentage by weight: c: 0.55-0.58%, Si: 0.12-0.62%, Mn: 1.54% -1.60%, P: less than or equal to 0.025%, S: less than or equal to 0.015 percent, Cr: 0.01-0.15%, Mo + Ni + Cu: 0.005-0.018%, and the balance of Fe and inevitable impurities; the steel rail structure is composed of pearlite and ferrite, wherein the volume fraction of the pearlite is more than or equal to 98%, the volume fraction of the ferrite is less than or equal to 2%, and rail head pearlite is fine pearlite with the interlamellar spacing of 80-100 nm;
the production process of the steel rail comprises the following steps:
(1) smelting, refining and continuous casting;
(2) heating a casting blank; stacking and slowly cooling the casting blanks to room temperature, then charging and heating, wherein the heating temperature is 1250-1300 ℃, and the heat preservation time is 2-4 hours; ensuring that the casting blank is always in a reducing atmosphere in the heating process;
(3) rolling a steel rail; carrying out three-stage rolling after descaling the casting blank by using high-pressure water; the rolling temperature of the first stage after cogging is 1190-1250 ℃, the temperature of a rolled piece taken out of a rolling mill is controlled to be 1080-1150 ℃, and the reduction rate of the section of the rolled piece is 30-50%; rolling in the second stage, wherein the temperature of the rolled piece exiting the rolling mill is 1000-1050 ℃, and the reduction rate of the section of the rolled piece is 40-65%; the temperature of rolled pieces entering the last rolling mill in the third stage is 940-980 ℃, the finishing temperature is 885-920 ℃, and the reduction rate of the section of the rolled pieces is 15-35%;
(4) performing waste heat treatment on the rolled steel rail; adopting a normalizing treatment mode, specifically: cooling the rail head to the final cooling temperature of 670-700 ℃ through water mist, then enabling the rail head to enter a heat treatment unit, cooling the rail head to the final cooling temperature of 440-470 ℃ at the cooling speed of 3-8 ℃/s through the cooperation of water vapor and compressed air, and blowing the centers of the rail web and the rail bottom with compressed air or water vapor at the cooling speed of 0.5-1 ℃/s all the time in the process that the steel rail enters the heat treatment unit, so as to ensure that the temperature of the steel rail is not higher than 510 ℃; air cooling to room temperature after normalizing treatment;
(5) the heat treated steel rail is straightened by horizontal and vertical compound, subjected to ultrasonic flaw detection, sized, inspected and warehoused.
2. The production method of the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway according to claim 1, wherein in the step (1), molten iron is subjected to desulfurization pretreatment, smelted by using a converter or an electric furnace, and subjected to ferrosilicon deoxidation; adding lime into LF refining for further desulfurization, wherein the refining time is 20-30 minutes; and then RH vacuum degassing treatment or VD vacuum degassing treatment is adopted, and the vacuum treatment time is 30-40 minutes.
3. The production method of the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway according to claim 2, wherein the addition amount of lime is 4-5 kg/ton of steel during LF refining.
4. The production method of the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway according to claim 1, wherein in the step (1), the casting blank after continuous casting is a large-section casting blank with the section size of 280-320 mm x 380-410 mm.
5. The method for producing the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway according to claim 1, wherein in the step (3), the steel rail is rolled by a three-stand rolling mill, a five-stand rolling mill or a seven-stand rolling mill.
6. The production method of the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway according to claim 1, wherein the steel rail has the tensile strength Rm of 1140-1195 MPa, the yield strength Rp0.2 of 701-727 MPa and the elongation A of more than or equal to 12.5%; the surface hardness of the rail head is 365-395 HB, the hardness of points A1, B1, C1, D1 and E1 of each hardness line of the cross section of the rail head is more than or equal to 37HRC, and the hardness of points A5, B4, C4, D3 and E3 of each hardness line of the cross section of the rail head is more than or equal to 35 HRC; the impact absorption energy AKU2 of the normal temperature impact test is more than or equal to 41J, and when the crack strength factor delta k =10MPam 1/2 When the crack propagation rate da/dN = 1.5-2.0, and when the crack strength factor Δ k =13.5MPam 1/2 The crack propagation rate da/dN = 6-10.5.
7. The method for producing the high-strength wear-resistant steel rail for the small-radius curve of the high-speed railway according to claim 1, wherein the steel rail is a 60kg/m steel rail.
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| CN101921950B (en) * | 2010-09-02 | 2011-12-14 | 攀钢集团有限公司 | Steel rail used for high-speed and quasi-high speed railways and manufacturing method thereof |
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