WO2024027264A1 - 一种具有高屈服强度的中等强度钢轨及其生产方法 - Google Patents

一种具有高屈服强度的中等强度钢轨及其生产方法 Download PDF

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Publication number
WO2024027264A1
WO2024027264A1 PCT/CN2023/093537 CN2023093537W WO2024027264A1 WO 2024027264 A1 WO2024027264 A1 WO 2024027264A1 CN 2023093537 W CN2023093537 W CN 2023093537W WO 2024027264 A1 WO2024027264 A1 WO 2024027264A1
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Prior art keywords
rail
strength
cooling
medium
high yield
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PCT/CN2023/093537
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English (en)
French (fr)
Inventor
李若曦
邓勇
杨大巍
袁俊
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攀钢集团攀枝花钢铁研究院有限公司
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Priority to AU2023319321A priority Critical patent/AU2023319321A1/en
Publication of WO2024027264A1 publication Critical patent/WO2024027264A1/zh

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Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/08—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling structural sections, i.e. work of special cross-section, e.g. angle steel
    • B21B1/085—Rail sections
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • 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
    • 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
    • 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
    • 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

Definitions

  • the invention relates to the field of rail production, specifically to a medium-strength rail with high yield strength and a production method thereof.
  • high-performance heat-treated pearlite rails are mainly used to improve the tensile strength and hardness of the rails through online or offline heat treatment to achieve Improve the wear resistance and contact fatigue resistance, but the existing medium-strength pearlite heat-treated rails rarely take into account the improvement of the rail's plastic deformation resistance brought by high yield strength and its fundamental reduction in the occurrence of surface contact fatigue damage.
  • high-strength heat-treated pearlite rails with high yield strength to take into account the reduced safety caused by issues such as increased wheel wear due to their excessive tensile strength and hardness when used on mixed passenger and freight lines.
  • Patent CN 106086622A "A heat treatment production method for rails for mixed passenger and freight railways and the resulting rails" discloses a rail for mixed passenger and freight transportation and its production method.
  • the chemical composition of the rail includes: C: 0.71 ⁇ 0.82 %, Si: 0.13 ⁇ 0.60%, Mn: 0.65 ⁇ 1.25%, Cr: 0.05 ⁇ 0.25%, P: ⁇ 0.020%, S: ⁇ 0.015%, Al: ⁇ 0.1%, the balance is Fe and inevitable impurities .
  • This patent uses an online heat treatment method to treat the rail head tread center, Both sides of the rail head and the center of the rail bottom undergo accelerated cooling, slow cooling and air cooling in sequence.
  • the opening cooling temperature of the accelerated cooling is 650-950°C, the cooling rate is 2.5-7°C/s, and the final cooling temperature is 400-630°C. °C, the cooling rate of the slow cooling is 0.1 ⁇ 1.5°C/s, and the final cooling temperature is 180-300°C.
  • the aluminum content in the rails described in this patent is relatively high, which can easily lead to rail core damage and fracture; and the production of this rail
  • the method requires accelerated cooling of the rail bottom, which requires high equipment and complicated production methods.
  • Patent CN 104988405A "A Rail for Mixed Use of Passengers and Freight and Its Production Method and Application” discloses a kind of rail for mixed use of passengers and freight and its preparation method.
  • the chemical composition of the rail includes: C: 0.71 ⁇ 0.78%, Si : 0.30 ⁇ 0.80%, Mn: 0.80 ⁇ 1.1%, Cr: 0.1 ⁇ 0.3%, V: 0.04 ⁇ 0.2%, P: ⁇ 0.020%, S: ⁇ 0.015%, the balance is Fe and inevitable impurities.
  • the rails adopt an online heat treatment method: the final rolled rails are rapidly cooled, and then the gauge corners are rapidly heated and insulated; the conditions for rapid cooling include: the opening cooling temperature is 800-880°C, and the cooling rate is 2-6°C.
  • the final cooling temperature is 430-470°C; the conditions for rapid heating and heat preservation include: raising the track angle temperature to 700-800°C at a heating rate of 3.0-4.0°C/s and keeping it warm for 2-4 minutes.
  • the rails described in this patent need to add high-priced alloy elements such as V, which is costly.
  • the rail head is heated multiple times during the rail production process. The production method is complicated, and the secondary heating has a greater impact on the performance stability of the rail head. It has a huge negative impact and seriously affects the safety performance of rail lines in service.
  • Patent CN 112301205A "A High Yield Ratio Pearlitic Rail Rail and its Preparation Method” discloses a high yield ratio pearlitic rail rail and its manufacturing method.
  • the composition of the rail is based on weight percentage: C: 0.70 ⁇ 0.85%, Si: 0.2 ⁇ 0.8%, Mn: 0.8 ⁇ 1.1%, Cr: 0.5 ⁇ 0.7%, Cu: 0.01 ⁇ 0.1%, Nb: 0.01 ⁇ 0.05%, P: ⁇ 0.020%, S: ⁇ 0.015%, Al ⁇ 0.005 %, the balance is Fe and inevitable impurities.
  • the rail uses an online heat treatment method.
  • the heat treatment is a multi-stage cooling process, and the rail is cooled from 850 to 950°C to room temperature at different cooling rates.
  • the rail described in this patent has a high yield strength, but its tensile strength exceeds 1300MPa, which can easily lead to rapid wheel wear when used on a low-axle load mixed passenger and freight line, which increases line maintenance costs.
  • the rail contains a large amount of Cr, Alloying elements such as Cu and Nb have high production costs and are difficult to promote production.
  • the purpose of the present invention is to provide a medium-strength rail with high yield strength and a production method thereof to meet the standard sound insulation and shock absorption requirements, with faster construction speed, stronger adhesion and lower cost. Lower and more stable sound insulation effect.
  • a medium-strength steel rail with high yield strength has: yield strength ⁇ 820MPa, tensile strength 1200-1300MPa, and elongation ⁇ 10%.
  • the microstructure of the rail head of the medium strength rail is full pearlite.
  • the surface hardness of the rail top surface of the medium-strength rail is 350-390HB, and the 10mm depth section hardness of the rail top surface and rail gauge corner is 35.5-41.0HRC.
  • the chemical composition of the rail should be: C: 0.65-0.85%, Si: 0.15-0.60%, Mn: 0.50-1.30%, Cr: 0.05-0.20%, P : ⁇ 0.020%, S: ⁇ 0.015%, the balance is Fe.
  • the invention also provides a production method based on medium-strength rails with high yield strength, which sequentially includes: converter smelting, LF furnace refining, RH vacuum treatment, continuous casting to obtain steel billet, rolling of steel billet, online heat treatment and processing.
  • in-line heat treatment includes:
  • the first stage of cooling cooling the rail after final rolling.
  • the cooling process includes accelerated cooling of the top surface of the rail, the two upper fillets of the rail head, the two sides of the rail head, and the two lower fillets of the rail head to the rail.
  • the top surface temperature is 630-750°C;
  • Second stage cooling Cool the rail after step a at a cooling rate of 3.0-6.0°C/s.
  • the rail top surface, the two upper fillets of the rail head, the two sides of the rail head, and the two lower fillets of the rail head are accelerated and cooled until the temperature of the rail top surface is 400-500°C;
  • step c Place the rail cooled in step c on the cooling bed, and air-cool the rail to room temperature.
  • the cooling medium used in the online heat treatment is at least one of water mist, compressed air, and a mixture of compressed air and water mist.
  • step a when the temperature of the rail top surface after final rolling is between 800-950°C, cooling care is performed.
  • the temperature in the cooling process, is lowered at a cooling rate of 1.0-3.0°C/s.
  • the cooling medium used in the online heat treatment is compressed air.
  • the invention adopts the method of controlling the chemical composition of the rail and the online heat treatment process, and can obtain a medium-strength rail with high yield strength without adding multiple alloy elements.
  • the yield strength is ⁇ 820MPa and the tensile strength is 1200-1300MPa. , elongation ⁇ 10%. Therefore, the medium-strength steel rail of the present invention can effectively reduce the probability of contact fatigue damage when used on mixed passenger and freight lines, can effectively improve the service performance and service life of the rail, and improve the safety of train operation.
  • this patent provides The production method of medium-strength rails with high yield strength is simple and easy to operate, which is conducive to its large-scale promotion and application in mixed passenger and freight lines.
  • the invention provides a medium-strength steel rail with high yield strength.
  • the medium-strength steel rail has high yield strength, with a yield strength of ⁇ 820MPa, a tensile strength of 1200-1300MPa, and an elongation of ⁇ 10%.
  • microstructure of the rail head of medium-strength rails is full pearlite.
  • the surface hardness of the rail top surface of medium-strength rails is 350-390HB, and the 10mm depth section hardness of the rail top surface and rail gauge angle is 35.5-41.0HRC.
  • the chemical composition of the rails in weight percentage should be: C: 0.65-0.85%, Si: 0.15-0.60%, Mn: 0.50-1.30%, Cr: 0.05-0.20 %, P: ⁇ 0.020%, S: ⁇ 0.015%, the balance is Fe and inevitable impurities.
  • the chemical composition of the rail in terms of weight percentage, is: C: 0.70-0.85%, Si: 0.30-0.60%, Mn: 0.95-1.25%, Cr: 0.05-0.20%, P: ⁇ 0.020%, S : ⁇ 0.015%, the balance is Fe and inevitable impurities.
  • C is the most important and cheapest element in pearlitic rails that enables the rails to obtain good comprehensive mechanical properties and promotes the transformation of pearlite.
  • the C content is ⁇ 0.65%, under the production process of the present invention, it is impossible to ensure that the rail has appropriate hardness and the anti-contact fatigue performance of the rail; when the C content is >0.85%, under the production process of the present invention, the rail's resistance to contact fatigue cannot be guaranteed.
  • the proportion of carbides is too high, the tensile strength is too high, and the strength index is excessive, which reduces the anti-contact fatigue performance of the rail during service and has an adverse effect on the safe use of the rail; therefore, the carbon content in the present invention is limited to 0.65-0.85%.
  • the main role of Si in steel is to inhibit the formation of cementite and serve as a solid solution strengthening element to increase the hardness of the ferrite matrix and improve the strength and hardness of the steel.
  • Si content is less than 0.15%, its solid solution content is low and the strengthening effect is not obvious.
  • abnormal structures such as martensite are prone to appear in the rails.
  • Si content is >0.60%, local segregation is likely to occur, which will reduce the toughness of the steel. Plasticity and weldability have a negative impact on the safe use of rails. Therefore, the Si content in the present invention is limited to 0.15-0.60%.
  • Mn is essential to improve the strength of ferrite and austenite in steel.
  • the Mn content is ⁇ 0.50%, it is difficult to increase the hardness of carbides and thereby increase the hardness of the steel; when the Mn content is >1.30%, it will coarsen the grain size and affect the structural changes of rail steel during the heat treatment process.
  • Mn has a significant impact on the diffusion of C in the steel, and abnormal structures such as bainite or martensite may be produced in the Mn segregation area, which also affects the welding performance of the rail. Therefore, the Mn content in the present invention is limited to 0.50-1.30%.
  • Cr can form a variety of carbides with carbon in steel; at the same time, Cr can Uniform carbide distribution in steel, reduce carbide size, and improve rail wear resistance.
  • the Cr content is ⁇ 0.05%, the hardness and proportion of the carbides formed are low; when the Cr content is >0.20%, the hardenability of the rail is too high, which can easily lead to the production of harmful bainite and martensite structures in the rail. While improving the mechanical properties of the rail, there is no guarantee that the rail will have a full pearlite structure. Therefore, the Cr content in the present invention is limited to 0.05-0.20%.
  • P and S are impurity elements that cannot be completely removed from rails. P will segregate at the grain boundaries of the rail structure, seriously reducing the toughness of the rail; S easily forms MnS inclusions in the steel, which is harmful to the wear resistance and contact fatigue resistance of the rail. Therefore, the P content in the present invention needs to be controlled below 0.020%; the S content needs to be controlled below 0.015%.
  • the invention also provides a production method for the above-mentioned medium-strength rail with high yield strength, which sequentially includes: converter smelting, LF furnace refining, RH vacuum treatment, continuous casting to obtain steel billet, rolling of steel billet, online heat treatment and processing.
  • the online heat treatment includes:
  • First stage cooling When the temperature of the rail top surface after final rolling is between 800-950°C, use a cooling rate of 1.0-3.0°C/s to round the rail top surface, rail head and rail head. The two side surfaces and the two lower corners of the rail head are subjected to accelerated cooling until the temperature of the rail top surface is 630-750°C;
  • the second stage of cooling use the cooling speed of 3.0-6.0°C/s to perform filleting on the top surface of the rail, the two upper corners of the rail head, the two sides of the rail head, and the two lower corners of the rail head after cooling in step a. Accelerate the cooling process until the rail top surface temperature is 400-500°C;
  • step c Place the rail cooled in step c on the cooling bed, and air-cool the rail to room temperature.
  • the cooling medium used in the online heat treatment of this patent is at least one of water mist, compressed air, and a mixture of compressed air and water mist.
  • the temperature of the rail head tread is 800-950°C
  • the rail has not yet started the pearlite phase transformation.
  • a lower cooling rate needs to be used to uniformly reduce the temperature of the rail.
  • the cooling rate needs to be controlled between 1.0-3.0°C/s;
  • the internal temperature of the rail head is in the range of 400-500°C.
  • the rail has completed the pearlite phase transformation process, and there is no obvious significance in continuing to accelerate cooling. It can be
  • the rails are air-cooled to room temperature for subsequent processing.
  • the complete production process of the production method of medium-strength rails with high yield strength of the present invention can be: using low-sulfur vanadium-containing molten steel, smelting through a converter or electric furnace, refining through LF, RH or VD vacuum treatment, and bloom protection continuous casting , billet heating furnace heating, high-pressure water descaling before billet rolling, universal rolling mill rolling, rail online heat treatment, step cooling bed room temperature air cooling, horizontal and vertical composite straightening, rail specification inspection, processing line treatment, surface inspection and Warehousing.
  • Examples 1-3 and Comparative Examples 1-3 correspond to the selection of rails with the following chemical compositions numbered 1-3.
  • the production process is the same as above, and the specific chemical compositions are shown in Table 1.
  • the balance is Fe and unavoidable impurities.
  • the yield strength, tensile strength, and elongation after break of the rail are tested in accordance with GB/T 228.1 "Tensile Test of Metal Materials Part 1: Room Temperature Test Method", and in accordance with GB/T 230.1 "Rockwell Hardness Test of Metal Materials Part 1".
  • Part 1: Test Method” Test the 10mm section hardness of the rail, and test the surface hardness of the top surface of the rail in accordance with GB/T 231.1 "Brickell Hardness Test of Metal Materials Part 1: Test Method”.
  • the tensile properties, rail top surface hardness, and 10mm position section hardness of Examples 1-3 and Comparative Examples 1-3 are shown in Table 3.
  • the rails obtained by the method of the present invention have high yield strength, with yield strength ⁇ 820MPa, tensile strength 1200-1300MPa, and elongation ⁇ 10%; while in the comparative example, the rails have yield strength, tensile strength, or microscopic A situation where the organization does not meet the requirements.

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Abstract

本发明属于钢轨生产领域，具体涉及一种具有高屈服强度的中等强度钢轨及其生产方法。本发明所述具有高屈服强度的中等强度钢轨，其具有：屈服强度≥820MPa，抗拉强度为1200-1300MPa，延伸率≥10％。本发明涉及的中等强度钢轨在不添加多种合金元素的情况下，通过在线热处理工艺设计获得了高屈服强度，能够有效降低在客货混运线路使用中的接触疲劳伤损出现几率，能够有效提升钢轨的服役性能和服役寿命，提高列车运行安全性，同时本专利提供的具有高屈服强度的中等强度钢轨生产方法简单、易操作，利于其在客货混运线路的大规模推广应用。

Description

一种具有高屈服强度的中等强度钢轨及其生产方法 技术领域
本发明涉及钢轨生产领域，具体是一种具有高屈服强度的中等强度钢轨及其生产方法。
背景技术
我国铁路正处于高速发展阶段，客运专用线路、重载货运线路增加幅度较大，但为了铁路领域的全方位发展，现有的客货混运线路也在进行升级改造工作，对于货运运输量、客运安全性、整体运营稳定性的要求都有所提升。这一趋势导致钢轨的剥离掉块等表面接触疲劳伤损情况加剧，严重影响钢轨的服役性能和服役寿命，难以保障铁路运输效率和安全。
目前国内外客货混运线路和货运专用线路为提升钢轨的服役性能和服役寿命，主要采用高性能热处理珠光体钢轨，通过在线或离线热处理的方式来提高钢轨的抗拉强度和硬度，以达到提高耐磨性能和抗接触疲劳性能，但现有的中等强度珠光体热处理钢轨鲜少考虑到高屈服强度带来的钢轨耐塑性变形能力的提升及其从根本上降低表面接触疲劳伤损出现的效果，而具有高屈服强度的高强度热处理珠光体钢轨又难以兼顾其过高的抗拉强度和硬度在应用于客货混运线路时会导致的车轮磨耗增加等问题带来的安全性降低。
专利CN 106086622A《一种客货混运铁路用钢轨的热处理生产方法以及所得钢轨》中公开了一种客货混运用钢轨及其生产方法，其钢轨化学成份按重量百分比包括：C:0.71～0.82％、Si:0.13～0.60％、Mn:0.65～1.25％、Cr:0.05～0.25％、P:≤0.020％、S:≤0.015％、Al:≤0.1％，余量为Fe和不可避免的杂质。该专利采用在线热处理方法，对钢轨的轨头踏面中心、 轨头两侧和轨底中心部位依次进行加速冷却、缓慢冷却和空冷，所述加速冷却的开冷温度为650-950℃，冷却速度为2.5～7℃/s，终冷温度为400-630℃，所述缓慢冷却的冷却速度为0.1～1.5℃/s，终冷温度为180-300℃，该专利所述钢轨中铝含量较高，容易导致钢轨核伤及断裂；且该钢轨的生产方法中需要对钢轨的轨底进行加速冷却，对于设备要求较高，生产方法复杂。
专利CN 104988405A《一种客货混运用钢轨及其生产方法和应用》中公开了一种客货混运用钢轨及其制备方法，其钢轨化学成份按重量百分比包括：C:0.71～0.78％、Si:0.30～0.80％、Mn:0.80～1.1％、Cr:0.1～0.3％、V:0.04～0.2％、P:≤0.020％、S:≤0.015％，余量为Fe和不可避免的杂质，该钢轨采用在线热处理方法：将终轧后的钢轨进行快速冷却，然后对轨距角部位进行快速加热和保温；快速冷却的条件包括：开冷温度为800-880℃，冷却速度为2-6℃/s，终冷温度为430-470℃；快速加热和保温的条件包括：以3.0-4.0℃/s的升温速度将轨距角温度升高至700-800℃并保温2-4min。该专利所述钢轨需要添加V等高价合金元素，成本较高，同时在钢轨生产过程中对钢轨轨头采用多次加热，生产方法复杂，且二次加热对于钢轨轨头的性能稳定性有较大负面影响，严重影响钢轨线路服役安全性能。
专利CN 112301205A《一种高屈强比珠光体钢轨及其制备方法》中公开了一种高屈强比珠光体钢轨及其制造方法，其钢轨的成分按重量百分比：C：0.70～0.85％、Si：0.2～0.8％、Mn：0.8～1.1％、Cr：0.5～0.7％、Cu：0.01～0.1％、Nb：0.01～0.05％、P：≤0.020％、S：≤0.015％、Al≤0.005％，余量为Fe和不可避免的杂质，该钢轨采用在线热处理方法，热处理为多阶段冷却工艺，以不同的冷却速度将钢轨从850～950℃冷却至室温。该专利所述钢轨具有较高的屈服强度，但其抗拉强度超过1300MPa，在低轴重客货混运线路使用中易导致车轮快速磨耗，提高线路维护成本，同时该钢轨中含有大量Cr、Cu、Nb等合金元素，生产成本较高，难以推广生产。
目前的热处理珠光体钢轨及其生产方法的相关专利中，大部分专利所公布的钢轨虽然具有较好的强度、硬度，但对钢轨屈服强度的研究较为粗 糙，屈服强度的提升主要由整体拉伸性能的提升带动，未考虑到钢轨低轴重线路应用过程中过高的抗拉强度反而导致服役安全性降低的情况出现，其得到的热处理珠光体钢轨仍无法完全满足客货混运线路升级改造后的性能需求，且化学成分体系、生产工艺均较为复杂，难以实现大规模应用。
发明内容
针对现有技术的缺陷和不足，本发明的目的在于提供一种具有高屈服强度的中等强度钢轨及其生产方法，以满足标准隔音减震要求，具有施工速度更快速，附着力更强，成本更低、隔音效果更稳定等优势。
为实现上述目的，本发明提供如下技术方案：
一种具有高屈服强度的中等强度钢轨，中等强度钢轨具有：屈服强度≥820MPa，抗拉强度为1200-1300MPa，延伸率≥10％。
在一个或多个实施方案中，中等强度钢轨的轨头显微组织为全珠光体。
在一个或多个实施方案中，中等强度钢轨的轨顶面的表面硬度为350-390HB，轨顶面及轨距角处10mm深度断面硬度为35.5-41.0HRC。
在一个或多个实施方案中，以重量百分比计，钢轨的化学成分应为：C:0.65-0.85％、Si:0.15-0.60％、Mn:0.50-1.30％、Cr:0.05-0.20％、P:≤0.020％、S:≤0.015％，余量为Fe。
本发明还提供一种基于具有高屈服强度的中等强度钢轨的生产方法，依次包括：转炉冶炼、LF炉精炼、RH真空处理、连铸获得钢坯、对钢坯进行轧制、在线热处理及加工。
在一个或多个实施方案中，在线热处理包括：
a、第一阶段冷却：将待终轧后钢轨进行冷却处理，冷却处理包括对钢轨轨顶面、轨头两上圆角、轨头两侧面、轨头两下圆角进行加速冷却处理至轨顶面温度为630-750℃；
b、第二阶段冷却：将经过步骤a冷却后的钢轨以3.0-6.0℃/s的冷却速 度对钢轨轨顶面、轨头两上圆角、轨头两侧面、轨头两下圆角进行加速冷却处理至轨顶面温度为400-500℃；
c、第三阶段冷却：将经过步骤c冷却后的钢轨放置在冷床上，将钢轨空冷至室温。
在一个或多个实施方案中，在线热处理所采用的冷却介质为水雾、压缩空气、压缩空气与水雾混合物中的至少一种。
在一个或多个实施方案中，步骤a中，待终轧后钢轨轨顶面温度在800-950℃之间时，进行冷却护理。
在一个或多个实施方案中，冷却处理中，以1.0-3.0℃/s的冷却速度降温。
在一个或多个实施方案中，在线热处理所采用的冷却介质压缩空气。
与现有技术相比，本发明的有益效果是：
本发明采用了控制钢轨化学成分和在线热处理工艺的方法，在无需添加多种合金元素的情况下即可获得具有高屈服强度的中等强度钢轨，其屈服强度≥820MPa，抗拉强度为1200-1300MPa，延伸率≥10％。由此，本发明的中等强度钢轨能够有效降低在客货混运线路使用中的接触疲劳伤损出现几率，能够有效提升钢轨的服役性能和服役寿命，提高列车运行安全性，同时本专利提供的具有高屈服强度的中等强度钢轨生产方法简单、易操作，利于其在客货混运线路的大规模推广应用。
具体实施方式
下面结合具体实施方式对本发明的技术方案作进一步详细地说明。
本发明提供了一种具有高屈服强度的中等强度钢轨，中等强度钢轨具有高屈服强度，其屈服强度≥820MPa，抗拉强度为1200-1300MPa，延伸率≥10％。
进一步的，中等强度钢轨的轨头显微组织为全珠光体。
进一步的，中等强度钢轨的轨顶面的表面硬度为350-390HB，轨顶面及轨距角处10mm深度断面硬度为35.5-41.0HRC。
进一步的，具有高屈服强度的中等强度钢轨，以重量百分比计，钢轨的化学成分应为：C:0.65-0.85％、Si:0.15-0.60％、Mn:0.50-1.30％、Cr:0.05-0.20％、P:≤0.020％、S:≤0.015％，余量为Fe和不可避免的杂质。
作为优选方案，钢轨的化学成分以重量百分比计，为：C:0.70-0.85％、Si:0.30-0.60％、Mn:0.95-1.25％、Cr:0.05-0.20％、P:≤0.020％、S:≤0.015％，余量为Fe和不可避免的杂质。以下详细说明本发明中钢轨主要化学元素含量的限定理由。
C是珠光体钢轨中使钢轨获得良好综合力学性能、促进珠光体转变的最重要、最廉价的元素。当C含量＜0.65％时，在本发明生产工艺下，无法保证钢轨具有合适的强硬度、无法保证钢轨的抗接触疲劳性能；当C含量＞0.85％时，在本发明生产工艺下，钢轨的碳化物比例过高，抗拉强度过、强度指标过剩，降低钢轨服役过程中的抗接触疲劳性能，对钢轨的安全使用有不利影响；因此，本发明中的碳含量限定在0.65-0.85％。
Si在钢中的主要作用是抑制渗碳体形成和作为固溶强化元素，提高铁素体基体硬度，改善钢的强度和硬度。当Si含量＜0.15％时，其固溶量偏低导致强化效果不明显，同时钢轨中易出现马氏体等异常组织；当Si含量＞0.60％时，易产生局部偏析，会降低钢的韧塑性和可焊性，对钢轨的安全使用有负面影响。因此，本发明中的Si含量限定在0.15-0.60％。
Mn是提高钢中铁素体和奥氏体强度所必不可少的。当Mn含量＜0.50％时，其难以达到增加碳化物硬度从而增加钢的强硬度的作用；当Mn含量＞1.30％时，其会粗化晶粒尺寸，影响热处理过程中钢轨钢的组织变化，明显降低钢的韧塑性；同时Mn在钢中对C的扩散影响显著，在Mn偏析区域有可能产生贝氏体或马氏体等异常组织，同时影响钢轨的焊接性能。因此，本发明中的Mn含量限定在0.50-1.30％。
Cr作为碳化物形成元素，与钢中的碳可形成多种碳化物；同时，Cr能 均匀钢中碳化物分布，减小碳化物尺寸，改善钢轨的耐磨性能。当Cr含量＜0.05％时，形成的碳化物硬度及比例较低；当Cr含量＞0.20％，钢轨的淬透性过高，易使钢轨生产有害的贝氏体和马氏体组织，在降低钢轨力学性能的同时，无法保证钢轨为全珠光体组织。因此，本发明中的Cr含量限定在0.05-0.20％。
P和S均为钢轨中无法完全除去的杂质元素。P会在钢轨组织晶界处偏聚，严重降低钢轨的韧性；S在钢中易形成MnS夹杂，对钢轨耐磨耗性能和耐接触疲劳性能有害。因此，本发明中的P含量需控制在0.020％以下；S含量需控制在0.015％以下。
本发明还提供了上述具有高屈服强度的中等强度钢轨的生产方法，依次包括：转炉冶炼、LF炉精炼、RH真空处理、连铸获得钢坯、对钢坯进行轧制、在线热处理及加工。
进一步的，上述具有高屈服强度的中等强度钢轨的生产方法，在线热处理包括：
a.第一阶段冷却：待终轧后钢轨轨顶面温度在800-950℃之间时，以1.0-3.0℃/s的冷却速度对钢轨轨顶面、轨头两上圆角、轨头两侧面、轨头两下圆角进行加速冷却处理至轨顶面温度为630-750℃；
b.第二阶段冷却：将经过步骤a冷却后的钢轨以3.0-6.0℃/s的冷却速度对钢轨轨顶面、轨头两上圆角、轨头两侧面、轨头两下圆角进行加速冷却处理至轨顶面温度为400-500℃；
c.第三阶段冷却：将经过步骤c冷却后的钢轨放置在冷床上，将钢轨空冷至室温。
进一步的，本专利在线热处理所采用的冷却介质为水雾、压缩空气、压缩空气与水雾混合物中的至少一种。
本发明的发明人经过大量研究发现：
①针对在线热处理工序第一阶段冷却：在钢轨轨头踏面温度为800-950℃ 时，钢轨尚未开始珠光体相变，为获得具有高屈服强度的钢轨，同时不过度提高钢轨的抗拉强度，需要采用较低的冷却速度使钢轨的温度均匀下降，为保证钢轨轨头温度均匀下降，需要将冷却速度控制在1.0-3.0℃/s之间；
②针对在线热处理工序第二阶段冷却：当钢轨轨头踏面温度经第一阶段冷却至630-750℃，钢轨已经开始发生珠光体相变，考虑到钢轨未加速冷却部位向轨头的热量传递，为获得具有高屈服强度的钢轨，需要采用更高的冷却速度，第二阶段冷却需要将冷却速度控制在3.0-6.0℃/s之间；
③针对第三阶段冷却：在前两个冷却阶段结束后，钢轨轨头内部温度处于400-500℃范围内，此时钢轨已完成珠光体相变过程，继续加速冷却已无明显意义，可将钢轨空冷至室温以进行后续工序处理。
本发明的具有高屈服强度的中等强度钢轨的生产方法的完整生产工艺可以为：采用低硫含钒钢水、经转炉或电炉进行冶炼、经LF精炼、RH或VD真空处理、大方坯保护连铸、钢坯加热炉加热、钢坯轧制前高压水除鳞、万能轧机轧制、钢轨在线热处理、步进式冷床室温空气冷却、平立复合矫直、钢轨规格检查、加工线处理、表面检查及入库。
以下将通过实施例对本发明进行详细描述，但本发明的范围不局限于此。
实施例1-3和对比例1-3对应选用以下编号1-3化学成分的钢轨，制作过程同上述内容，具体化学成分如表1所示。
表1
余量为Fe和不可避免的杂质。
实施例1-3对比例1-3热处理工艺参数如表2所示，实施例和对比例的 冶炼工艺和轧制工艺之间的差异是可以忽略不计的。
表2
本发明中按照GB/T 228.1《金属材料拉伸试验第1部分：室温试验方法》测试钢轨的屈服强度、抗拉强度、断后伸长率，按照GB/T 230.1《金属材料洛氏硬度试验第1部分：试验方法》测试钢轨的10mm位置断面硬度，按照GB/T 231.1《金属材料布氏硬度试验第1部分：试验方法》测试钢轨的轨顶面表面硬度。实施例1-3和对比例1-3的拉伸性能、轨顶面表面硬度、10mm位置断面硬度如表3所示。
表3

通过比较实施例和对比例可以看出，本发明所述的实施例在相同的化学成分和冶炼工艺下，轧制后钢轨的在线热处理方式的不同对钢轨的最终性能将产生显著影响，通过采用本发明所述的方法所获得的钢轨具有高屈服强度，其屈服强度≥820MPa，抗拉强度为1200-1300MPa，延伸率≥10％；而对比例中钢轨存在屈服强、抗拉强度或显微组织不满足要求的情况。
上面对本发明的较佳实施方式作了详细说明，但是本发明并不限于上述实施方式，在本领域的普通技术人员所具备的知识范围内，还可以在不脱离本发明宗旨的前提下做出各种变化。

Claims (10)

  1. 一种具有高屈服强度的中等强度钢轨，其特征在于，所述中等强度钢轨具有：屈服强度≥820MPa，抗拉强度为1200-1300MPa，延伸率≥10％。
  2. 根据权利要求1所述的具有高屈服强度的中等强度钢轨，其特征在于，所述中等强度钢轨的轨头显微组织为全珠光体。
  3. 根据权利要求1或2所述的具有高屈服强度的中等强度钢轨，其特征在于，所述中等强度钢轨的轨顶面的表面硬度为350-390HB，轨顶面及轨距角处10mm深度断面硬度为35.5-41.0HRC。
  4. 根据权利要求3所述的具有高屈服强度的中等强度钢轨，其特征在于，以重量百分比计，钢轨的化学成分应为：C:0.65-0.85％、Si:0.15-0.60％、Mn:0.50-1.30％、Cr:0.05-0.20％、P:≤0.020％、S:≤0.015％，余量为Fe。
  5. 一种具有高屈服强度的中等强度钢轨的生产方法，其特征在于，依次包括：转炉冶炼、LF炉精炼、RH真空处理、连铸获得钢坯、对钢坯进行轧制、在线热处理及加工。
  6. 根据权利要求5所述的生产方法，其特征在于，所述在线热处理包括：
    a、第一阶段冷却：将待终轧后钢轨进行冷却处理，所述冷却处理包括对钢轨轨顶面、轨头两上圆角、轨头两侧面、轨头两下圆角进行加速冷却处理至轨顶面温度为630-750℃；
    b、第二阶段冷却：将经过步骤a冷却后的钢轨以3.0-6.0℃/s的冷却速度对钢轨轨顶面、轨头两上圆角、轨头两侧面、轨头两下圆角进行加速冷却处理至轨顶面温度为400-500℃；
    c、第三阶段冷却：将经过步骤c冷却后的钢轨放置在冷床上，将钢轨空冷至室温。
  7. 根据权利要求6所述的生产方法，其特征在于，所述在线热处理所采用的冷却介质为水雾、压缩空气、压缩空气与水雾混合物中的至少一种。
  8. 根据权利要求6所述的生产方法，其特征在于，步骤a中，所述待终轧后钢轨轨顶面温度在800-950℃之间时，进行冷却护理。
  9. 根据权利要求6所述的生产方法，其特征在于，所述冷却处理中，以1.0-3.0℃/s的冷却速度降温。
  10. 根据权利要求6所述的生产方法，其特征在于，所述在线热处理所采用的冷却介质压缩空气。
PCT/CN2023/093537 2022-08-05 2023-05-11 一种具有高屈服强度的中等强度钢轨及其生产方法 WO2024027264A1 (zh)

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