WO2009047926A1 - Rail en acier perlitique à dureté interne élevée dont la résistance à l'usure, à la rupture par fatigue et à la fracture retardée sont excellentes ainsi que son procédé de fabrication - Google Patents

Rail en acier perlitique à dureté interne élevée dont la résistance à l'usure, à la rupture par fatigue et à la fracture retardée sont excellentes ainsi que son procédé de fabrication Download PDF

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Publication number
WO2009047926A1
WO2009047926A1 PCT/JP2008/056273 JP2008056273W WO2009047926A1 WO 2009047926 A1 WO2009047926 A1 WO 2009047926A1 JP 2008056273 W JP2008056273 W JP 2008056273W WO 2009047926 A1 WO2009047926 A1 WO 2009047926A1
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Prior art keywords
content
mass
resistance
rail
less
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PCT/JP2008/056273
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English (en)
Japanese (ja)
Inventor
Minoru Honjo
Tatsumi Kimura
Shinichi Suzuki
Kimihiro Nishimura
Nobuo Shikanai
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Jfe Steel Corporation
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Application filed by Jfe Steel Corporation filed Critical Jfe Steel Corporation
Priority to CN2008800203846A priority Critical patent/CN101743334B/zh
Priority to EP08739390.6A priority patent/EP2196552B1/fr
Priority to CA2687438A priority patent/CA2687438C/fr
Priority to US12/663,866 priority patent/US20100186857A1/en
Priority to AU2008310503A priority patent/AU2008310503B2/en
Publication of WO2009047926A1 publication Critical patent/WO2009047926A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • 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
    • C21D2221/00—Treating localised areas of an article
    • 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
    • C21D2221/00—Treating localised areas of an article
    • C21D2221/02—Edge parts

Definitions

  • the present invention relates to an internal high hardness type pearlitic rail excellent in wear resistance and rolling contact fatigue (RCF) resistance, and a manufacturing method thereof. Is under severe high-axis load conditions, such as overseas mining railways with heavy weight of freight car and high curve lines.
  • the present invention relates to a high-hardness pearlite steel rail with excellent wear resistance, fatigue damage resistance and delayed fracture property that achieves a longer operating life of the rail used, and a method for manufacturing the same. ⁇ ⁇
  • High-axle load railway which mainly transports mineral ore
  • the load applied to the axle of the freight car is much higher than that of the passenger car.
  • the use environment of the rail is also harsh.
  • steels having a pearlitic structure are mainly used for rails used in such an environment from the viewpoint of a significant concern of wear resistance.
  • High-axle heavy rail means trains and Railway wagons are heavy (loading capacity per freight car is about 150 tons or more, for example).
  • Japanese Patent Laid-Open No. 2002-69585 proposes a technique for suppressing the formation of pro-eutectoid cementite by adding Al and Si and improving the fatigue damage resistance.
  • Japanese Patent Application Laid-Open No. 10-195601 discloses that the rail at the depth of at least 20 thighs starting from the corner of the head and the top of the head is HV370 or more. The service life is improved. Further, in JP 2003-293086, by controlling a pearlite block, the hardness of at least a depth of 20 mm starting from the rail head corner and head surface is Hv300 to 500 In this way, the service life of the rail is improved. However, the higher the strength of the rail, the longer the delay and the higher the risk of breakage. JP-A 8-109439, JP-A 8-144016, JP-A 8-246100, JP-A 8-246101 JP, JP 2002-69585, JP 10-195601, JP
  • Japanese Patent No. 3648192 and Japanese Patent Laid-Open No. 5-287450 disclose techniques for preventing delayed fracture of pearlite steel rails (hereinafter referred to as pearlite steel rails).
  • pearlite steel rails a technique for improving delayed fracture resistance is disclosed.
  • this technology is applied to rails, there is a problem that the manufacturing cost of the rails increases due to the strong wire drawing.
  • JP 2000-328190, JP 6-279928, JP 3323272, and JP 6-279929 are intended to improve the toughness and ductility of the rail. In addition, it controls the form and amount of A inclusions.
  • Japanese Patent Application Laid-Open No. 2000-328190, JP 6-279928, JP 3323272, and JP 6-279929 are intended to improve the toughness and ductility of the rail. In addition, it controls the form and amount of A inclusions.
  • the size of the A-type inclusions is set to 0.1 to 20 ⁇ m, and the number of A-type inclusions is controlled to 25 to 11,000 per square 2 Improve toughness and ductility. Therefore, this technique does not always provide good delayed fracture resistance.
  • the [% V] / [% N] value calculated from the V content [% V] and the N content [% N] is maintained within an appropriate range, and the hardenability index (hereinafter referred to as DI) ) And carbon equivalent (hereinafter referred to as C eq ) to increase the hardness within a range of at least 25 mm from the rail head surface, wear resistance, fatigue damage It provides an internal high-hardness pearlite steel rail with excellent durability and delayed fracture resistance, along with its preference and manufacturing method. Disclosure of the invention
  • the inventors manufactured a perlite steel rail with varying contents of Si, Mn, Cr, V, and N.
  • the [% Mn] / [% Cr] value calculated from the Mn content [% Mn] and the Cr content [% Cr] should be 0.3 or more and less than 1.0 and [% V] / [ % N]
  • lamellar spacing of the parlite layer hereinafter also simply referred to as lamellar
  • the internal hardness of the rail head defined by the hardness in the range, was Hv380 or more and less than Hv480, and the wear resistance, fatigue damage resistance, and delayed fracture resistance were improved.
  • the hardenability index (ie, DI value) is within the range of 5.6 to 8.6, and the carbon equivalent (ie, C e J) is within the range of 1.04 to 1.27.
  • the [% Si] + [% Mn] + [% Cr] value calculated from the Mn content [% Mn], Cr content [% Cr], and Si content [% Si] is 1.55-2. It was found that the effect of improving the wear resistance and fatigue damage resistance can be stably maintained by setting it within the range of 50. The present invention has been made based on these findings.
  • C 0.73 to 0.85 mass%
  • Si 0.5 to 0.75 mass.
  • N Mn 0.3 to 1.0 mass 0 I P: 0.035 mass 0/0 less
  • S from .0005 to 0.012 wt%
  • Cr 0.2 to 1.3 mass 0 I
  • V from 0.005 to .12 weight 0 I
  • N from 0.0015 to .0060
  • Weight containing 0/0 has the balance consisting of Fe and unavoidable impurities, [% Mn] Z [% Cr] value as [% Cr] the Cr content was Mn content and [% Mn] is 0.3 to 1.0, and V content is [% V], N content is [% N], and [% V] / [% N] value is 8.0 to 30.0, at least from the surface of the rail head Internal hardened pearlite steel with excellent wear resistance, fatigue damage resistance and delayed fracture resistance, whose internal hardness of the rail head defined by Vickers hardness in the range of 25mra depth is Hv380 or
  • the C content of the above composition is [% C]
  • the Si content is [% Si]
  • the Mn content is [% Mn]
  • the soot content is [% P]
  • S content is [% S]
  • Cr content is [% Cr]
  • V content is [% V]
  • the DI value calculated by the following formula (1) is 5.6 to 8.6.
  • C eq value force S 1.04 to 1.27 calculated by the following equation (2) is preferable.
  • the Si content of the above composition is [% Si]
  • the Mn content is [% Mn]
  • the Cr content is [% Cr]
  • the [% Si] + [% Mn] + [% Cr] value is It is preferable to satisfy the range of 1.55 to 2.50.
  • the lamellar spacing of the pearlite layer in the range of a depth of at least 25 mm from the surface layer of the Lenore head is preferably 0.04 to 0.15 / z m.
  • the present invention also hot-rolls the steel material having the above-described composition into a rail shape so that the rolling finishing temperature is 850 to 950 ° C., and then continues the rail head surface from a temperature equal to or higher than the pearlite transformation start temperature. 1.
  • This is a method for manufacturing high-hardness pearlite steel rails with excellent wear resistance, fatigue damage resistance and delayed fracture resistance, with accelerated cooling to 400-650 ° C at a cooling rate of 2-5 ° C / sec. .
  • Fig. 1A and Fig. 1B are diagrams showing the Nishihara-type wear test piece for evaluating wear resistance.
  • Fig. 1A is a plan view and Fig. 1B is a side view.
  • Figure 2 A cross-sectional view of the rail head showing the sampling position of the Nishihara-type wear test piece.
  • Fig. 3A and Fig. 3B are diagrams showing the Nishihara-type wear test piece for evaluating fatigue damage resistance.
  • Fig. 3A is a plan view and Fig. 3B is a side view.
  • Fig. 4 is a cross-sectional view of the rail head showing the sampling position of the S SRT (Slow Strain Rate technique) test piece.
  • Fig. 5 Cross-sectional view showing the dimensional shape of the SSRT test piece.
  • Fig. 6 is a graph showing the relationship between [% V] Z [% N] value and the margin for improving delayed fracture susceptibility.
  • C forms cementite in the parlite structure and is an indispensable element for ensuring wear resistance.
  • wear resistance improves.
  • it is less than 0.73% by mass, it is difficult to obtain excellent wear resistance as compared with the conventional heat treated pearlite steel rail.
  • the C content is 0.73 to 0.85% by mass. More preferably, 0.75 to 0.85 mass. / 0 .
  • Si needs to be 0.5% by mass or more as a deoxidant and a strengthening element for the pearlite structure, but if it exceeds 0.75% by mass, the weldability is poor due to the high bonding strength of Si with oxygen. Turn into.
  • the Si content is 0.5 to 0.75 mass%. More preferably, it is 0.5 to 0.70% by mass.
  • Mn contributes to increasing the strength and ductility of internal hardened perlite steel rails by lowering the parrite transformation temperature and reducing the lamellar spacing, but excessive addition reduces the equilibrium transformation temperature of the parlite. As a result, it is an element that reduces the degree of supercooling and coarsens the lamellar spacing. If the amount is less than 3% by mass, a sufficient effect cannot be obtained. If the amount exceeds 1.0% by mass, a martensite structure is easily formed, and the material is easily deteriorated due to hardening and embrittlement during heat treatment and welding. In addition, even if a pearlite structure is formed, the equilibrium transformation temperature decreases, leading to coarse lamellar spacing. Therefore, the Mn content is 0.3 to 1.0% by mass. More preferably, it is 0.3-0.8 mass%.
  • the P content exceeds 0.035%, ductility deteriorates. Therefore, the P content is 0.035% by mass or less. More preferably, it is 0.020 mass% or less.
  • S is present in steel materials mainly in the form of A-based inclusions.
  • the content exceeds 0.012 mass%, the amount of inclusions increases remarkably, and at the same time, coarse inclusions are generated. Turn into.
  • the content is less than 0.0005 mass%, the steelmaking cost increases. Te the month, S content is set to 0.0005 to 0.012 mass 0/0. More preferably, it is 0.0005 to 0.008 mass%.
  • the Cr is an element that raises the pearlite equilibrium transformation temperature and contributes to the refinement of the lamellar spacing, while at the same time providing higher strength through solid solution strengthening.
  • the amount is less than 0.2% by mass, sufficient internal hardness cannot be obtained.
  • the Cr content is 0.2 to 1.3% by mass.
  • it is 0.3-1.3 mass%. More preferably, it is 0.5-1.3 mass%.
  • V forms a carbonitride and disperses and precipitates in the matrix, improving wear resistance and delayed fracture resistance. However, if it is less than 0.005% by mass, the effect is small. As the cost of gold increases, the cost of internal hardened perlite copper rails increases. Therefore, V amount is 0.005-0.12 mass. / 0 . More preferably, it is 0.012-0.10 mass%.
  • N forms nitrides and disperses and precipitates in the matrix, improving wear resistance and delayed fracture resistance, but less than 0.0015% by mass is less effective, while 0.0060% by mass. If it exceeds / 0 , coarse nitrides will be formed in the internal hardened perlite copper rail, resulting in reduced fatigue damage resistance and delayed fracture resistance. Therefore, the N content is 0.0015 to 0.0060 mass%. More preferably, it is 0.0030-0.0060 mass%. [% Mn] Z [% Cr]: 0.3 or more and less than 1.0:
  • Mn and Cr are elements added to increase the hardness of the internal high-hardness pearlite steel rail.
  • the units of [% Mn] and [% Cr] are both mass%. If the value of [% Mn] / [% Cr] is less than 0.3, the amount of Cr added is large, and because of the high hardenability of Cr, martensite is formed on the surface layer of the internal hardened pearlite copper rail. It is easy to generate.
  • the value of [% Mn] / [% Cr] is 1.0 or more, the amount of Mn added increases and the surface layer of the internal high-hardness type pearlite steel rail is similarly used due to the high hardenability of Mn. This makes it easier to generate martensite.
  • the value of [% Mn] no [% Cr] is set to 0.3 or more and less than 1.0 to prevent martensite formation on the surface layer.
  • the internal hardness of the rail head (the hardness in the range of at least 25 mm depth from the head surface layer of the internal high hardness type pearlite steel rail) can be controlled within the range described later. Therefore, the value of [% Mn] / [% Cr] is 0.3 or more and less than 1.0. Preferably it is 0.3 or more and 0.9 or less.
  • V and N are important elements that form V-based nitrides that serve as hydrogen trap sites.
  • the amount of addition must be controlled in order to form V-based nitrides.
  • [% V] and units [% N] are both mass 0/0. If the value of [% V] / [% N] is less than 8.0, the formation of V-based nitrides is not sufficient, the hydrogen trap size is reduced, and a significant improvement in delayed fracture resistance is expected. Can not. Also, if the value of [% V] / [% N] exceeds 30.0, the amount of V will increase and the alloy cost will increase, so the cost of internal hardened single light steel rail will be reduced. Not only increased, but also greatly improved delayed fracture resistance I can't expect it. Therefore, the value of [% V] / [% N] is 8.0 to 30 ⁇ 0. More preferably, it is 8.0-22.0.
  • Internal hardness of the rail head (hardness in the depth range of at least 25mm from the top surface of the internal hardened pearlitic steel rail head): Hv380 or more, but less than Hv480:
  • the internal hardness of the rail head is less than Hv380, the wear resistance decreases, and the service life of the internal high hardness type single copper copper rail decreases.
  • the Hv is 480 or more, martensite is generated, and the fatigue damage resistance of the internal hardened pearlite steel rail is lowered. Therefore, the internal hardness of the rail head is Hv380 or more and less than Hv480.
  • the definition of the internal hardness of the rail head is set to a range of at least 25 mm depth from the top surface of the internal high-hardness pearlitic steel rail.
  • this range includes a depth of less than 25 mm, This is because the wear resistance of the internal high-hardness pearlite steel rail decreases as it enters the inside from the surface layer of the rail head, and the service life is shortened. More preferably, the internal hardness of the rail head is more than Hv390 and less than Hv480.
  • DI values are C content [% C], Si content [% Si], Mn content [% Mn], P content [% P], S content [% S], The Cr content is [% Cr] and the V content is [% V].
  • [% C], [% Si ], [% n], [% P], [% S], [% Cr], units of [% V] are both mass 0/0.
  • This DI value represents hardenability and is used as an index for judging the quality of hardenability.
  • martensite is applied to the surface layer of the internal high-hardness type steel steel rail. It is preferable to use it as an index for suppressing the generation of rhinoceros and to achieve the target value of the internal hardness of the rail head, and keep it within a suitable range. If the DI value is less than 5.6, the desired internal hardness can be obtained, but it will be close to the lower limit of the target hardness range, so further improvement in wear resistance, fatigue damage resistance, and delayed fracture resistance cannot be expected. .
  • the DI value is preferably 5.6 to 8.6. More preferably, it is 5.6 to 8.2.
  • C eq value is C content [% C], Si content [% Si], Mn content [% Mn], Cr content [% Cr], V content [% V] As a value calculated by the following equation (2).
  • the units of [% C], [% Si], [% Mn], [% Cr], and [% V] are all mass%.
  • C eq [% C] + ([% Si] / ll) + ([% Mn] / 7) + ([% Cr] /5.8) + [% V] ⁇ ⁇ ⁇
  • This C eq value is the force used to estimate the maximum hardness and weldability that can be obtained from the composition ratio of the alloy components.
  • martensite is generated on the surface layer of the internal high-hardness type steel steel rail. It is preferable to use it as an index for achieving the target value of the internal hardness of the rail head and to keep it within a suitable range. If the C eq value is less than 1.04, the desired internal hardness can be obtained, but it will be close to the lower limit of the target hardness range, so further improvement in wear resistance and fatigue damage resistance cannot be expected.
  • C eq value is preferably you to the 1.04 to 1.27. More preferably, it is 1.04-1.20. [% Si] + [% Mn] + [% Cr]: 1.55-2.50:
  • the [% Si] + [% n] + [% Cr] value is preferably 1.55 to 2.50. More preferably, it is 1.55-2.30% by mass.
  • the units of [% Si], [% Mn], and [% Cr] are all mass%.
  • Cu 1.0 mass% or less
  • Ni 1.0 mass% or less
  • Nb 0.001 to 0.05 mass.
  • Mo One or more selected from 0.5% by mass or less may be added as necessary.
  • Cu like Cr, is an element for further strengthening by solid solution strengthening. In order to obtain the effect, addition of Cu of 0.005% by mass or more is preferable. However, Cu cracking tends to occur when the content exceeds 1.0% by mass. Therefore, when adding Cu, the amount of Cu is preferably 1.0% by mass or less. More preferably, it is 0.005 to 0.5 mass%.
  • Ni 1.0 mass% or less:
  • Ni is an element for increasing the strength without deteriorating the ductility.
  • addition of 0.005% by mass or more is preferable.
  • 1.0 mass. / Addition exceeding 0 increases hardenability and martensite As a result, wear resistance and fatigue damage resistance tend to decrease. Therefore, when adding Ni, the amount of Ni is preferably 1.0% by mass or less. Further preferred ⁇ details, 0.005 0.5 wt 0/0.
  • Nb binds to C in copper and precipitates as carbide during and after rolling, and effectively acts to reduce the size of the pearlite colony.
  • the wear resistance, fatigue damage resistance, and ductility are greatly improved, greatly contributing to the extension of the service life of internal hardened pearlite steel rails.
  • addition of 0.001% by mass or more is preferable.
  • the Nb content is less than 0.001% by mass, sufficient effects cannot be obtained.
  • Even if added over 0.05% by mass the effect of improving wear resistance and fatigue damage resistance is saturated, and an effect commensurate with the amount added cannot be obtained. Therefore, when Nb is added, the Nb content is preferably 0.001 0.05 mass%. More preferably, it is 0.001 0.03% by mass.
  • Mo is an element for further strengthening by solid solution strengthening. In order to obtain the effect, addition of 0.005% by mass or more is preferable. However, if it exceeds 0.5 mass%, a bainitic structure tends to be formed, and the wear resistance tends to decrease. Therefore, when Mo is added, the amount of Mo is preferably 0.5% by mass or less. More preferably, it is 0.005 0.3% by mass.
  • the improvement of these characteristics will be insufficient, so it is preferable to set it to 0.15 // m or less. If the lamellar spacing is set to less than 0.04 / zm, the hardenability is improved and a finer method is used. In this case, martensite is easily generated on the surface layer and fatigue damage resistance is caused. Adversely affects sex. Therefore, it is preferable that the thickness is 0.04 ⁇ m or more.
  • a pearlite steel rail that contains other trace component elements within a range that does not substantially affect the function and effect of the present invention instead of a part of the remaining Fe in the composition according to the present invention is also disclosed in the present invention.
  • impurities include P, 0, and the like, and P can be allowed to be 0.035 mass% as described above.
  • O is 0.004 mass. / 0 is acceptable.
  • Ti mixed as impurities can be tolerated up to 0.0 0 10%.
  • T i. Forms an oxide and causes a decrease in fatigue damage resistance, which is a basic characteristic of the rail, and therefore it is preferable to control it to 0.0 0 10%.
  • the internal high-hardness pearlite copper rail of the present invention is obtained by hot-rolling a steel material having the composition according to the present invention into a rail shape so that the rolling finishing temperature is 850 to 950 ° C. Head from temperature above pearlite transformation starting temperature 1.2-5. It is preferred to manufacture by slack quenching from 400 to 650 ° C at a cooling rate of C / sec. Roll finishing temperature: 850 to 950 ° C, accelerated cooling rate: 1.2 to 5 ° C / sec Cooling stop temperature: 400 to 650 ° C The reason is as follows. Rolling finishing temperature: 850 ⁇ 950 ° C:
  • the rolling finish temperature should be 850 to 950 ° C Cooling rate from temperature above pearlite transformation start temperature: 1.2 to 5 ° C / sec: Cooling rate is 1.2 If it is less than ° C / sec, the pearlite transformation start temperature will rise, the lamellar spacing of the pearlite layer will become coarse, and the wear resistance and fatigue damage resistance will be significantly reduced, while the cooling rate will be 5 ° C / sec.
  • the cooling rate should be in the range of 1.2 to 5 ° C / sec. More preferably, it is 1.2 to 4.6 ° C./second
  • the perlite transformation start temperature varies depending on the cooling rate, but in the present invention, it is the equilibrium transformation temperature). > In the component range of the present invention, cooling in this range from 720 ° C or higher. The rejection speed may be adopted. Cooling stop temperature: 400-650 ° C:
  • the cooling stop temperature in order to obtain a homogeneous pallite structure at a cooling rate of 1.2 to 5 ° C / sec, is 70 ° C above the equilibrium transformation temperature. It is preferable to secure a temperature lower than about a certain degree. However, if the cooling stop temperature is less than 400 ° C, the cooling time will increase, leading to an increase in the cost of internal hardened pearlite steel rails. Therefore, the cooling stop temperature should be 400-650 ° C. More preferably, it is 450-650 degreeC. Next, we will explain how to measure or evaluate the wear resistance, fatigue damage resistance, delayed fracture resistance, internal hardness of the rail head, and lamella spacing.
  • the contact angle between the actual internal high-hardness pearlite steel lenore and the wheel using the Nishihara type rolling contact test machine that can evaluate the wear resistance in a short time. Evaluation is based on a comparative test that simulates one cow (condition of rail and wheel contact). Take a Nishihara-style wear test piece 1 with an outer diameter of 30 mm from the rail head and rotate it in contact with the tire test piece 2 as shown in Fig. 1. The arrows in Fig. 1 indicate the rotation directions of the Nishihara-type wear test piece 1 and the tire test piece 2, respectively.
  • a round bar of 32mm ⁇ was taken from the head of the ordinary rail described in JIS E 1101, and heat-treated so that the Vickers hardness (load 98N) was HV390 and the structure was tempered martensite structure.
  • the shape shown in Fig. 1 was processed into a tire test piece.
  • the Nishihara-type wear test piece 1 is collected from two places on the rail head 3 as shown in Fig.2. What is taken from the surface layer of the rail head 3 is a Nishihara type wear test piece La shall be taken from the inside, and the Nishihara style wear test specimen shall be lb.
  • the center in the longitudinal direction of the Nishihara-type wear test specimen lb collected from the inside of the rail head 3 is located at a depth of 24 to 26 (average value 25 mm) from the upper surface of the rail head 3.
  • the test environment is dry and contact pressure is 1.4Gpa, slip ratio-10%, rotation speed is 675rpm (tire test piece is 750rpm) Measure the amount of wear.
  • the heat-treated perlite steel rail is adopted as the standard steel when comparing the amount of wear, and it is judged that the wear resistance has been improved when the wear is 10% or less than this standard steel.
  • the allowance for improving wear resistance was calculated as ⁇ (amount of wear of reference material ⁇ amount of wear of test material) I (amount of wear of reference material) ⁇ X 100.
  • the contact surface is a curved surface with a radius of curvature of 15 mm and a Nishihara-type wear test piece 1 with a diameter of 30 is taken from the rail head and rotated by contacting with the tire test piece 2 as shown in Fig. 3. Test.
  • the arrows in Fig. 3 indicate the rotation directions of the Nishihara-type wear test piece 1 and the tire test piece 2, respectively.
  • Nishihara-type wear test piece 1 is collected from two places on rail head 3. Since the position where the Nishihara-type wear test piece 1 is taken and the tire test piece are the same as described above, the description thereof is omitted.
  • the test environment is oil lubrication, contact pressure: 2.2 Gpa, slip rate: -20%, rotational speed: 600 rpm (tire test piece is 750 rpm), and the surface of the test piece is observed every 25,000 times. 0
  • the number of rotations at the time when 5 or more cracks occur is the fatigue damage life.
  • a heat-treated perlite steel rail is used as a reference steel for comparing the fatigue damage life, and this reference copper material also has fatigue damage resistance when the fatigue damage time is longer than 10%. Judged as improved.
  • the fatigue damage improvement allowance is calculated by ⁇ (number of rotations until the fatigue damage of the test material-number of rotations until the fatigue damage of the reference material) I (number of rotations until the damage of the reference material occurs) ⁇ X 100 I put it out. (Delayed fracture resistance)
  • an S SRT (Slow Strain Rate Technique) test piece 4 is sampled from the upper surface of the rail head 3 around 25.4 mm.
  • the dimensions and shape of SSRT test piece 4 are as shown in Fig. 5.
  • ⁇ (three triangle mark) finish except for screw section and R section, parallel part is polished to # 600 (Emery paper).
  • This S S RT test piece is attached to the test equipment, and the strain rate (strain)
  • the delayed fracture sensitivity improvement allowance is ⁇ (delayed fracture susceptibility of the test material-delayed fracture susceptibility of the reference material) I (Reference material delayed fracture susceptibility) Calculated by X 100. '
  • a steel material having the composition shown in Table 1 was rolled and cooled under the conditions shown in Table 2 to produce a pearlite steel rail. Cooling was performed only on the rail head, and after cooling stopped, it was allowed to cool. This pearlite steel rail was evaluated for Vickers hardness, lamellar spacing, wear resistance, fatigue damage resistance and delayed fracture resistance. The results are shown in Table 3.
  • the rolling finish temperature in Table 2 is the finish rolling temperature measured by the radiation thermometer measured on the surface of the rail head side surface on the entry side of the final rolling mill.
  • the cooling stop temperature is the cooling stop temperature obtained by measuring the temperature of the rail head side surface layer on the exit side of the cooling facility with a radiation thermometer. The cooling rate was defined as the time change in temperature from the start to the end of cooling.
  • the [% Mn] / [% Cr] value is set to 0.3 or more and less than 1.0
  • the [% V] / [% N] value is set to 8.000.0. It can be seen that at least 25 range from the surface layer of the rail head is Hv380 or more and less than Hv480, wear resistance and fatigue damage resistance are improved, and powerful delayed fracture resistance is improved by 10% or more. On the other hand, even when the [% V] / [% N] value exceeds 30, as in 1-F and 1-1, no significant improvement in delayed fracture resistance is observed. I understand that
  • the steel material having the composition shown in Table 4 was rolled and cooled under the conditions shown in Table 5 to produce a pearlite steel rail. Cooling was performed only on the rail head and after cooling stopped. As with Example 1, this perlite copper rail was evaluated for Vickers hardness, lamellar spacing, wear resistance, fatigue damage resistance, and delayed fracture resistance. The results are shown in Table 6. '
  • the addition amount of Si, Mn, Cr, V, and N was optimized, such as 2-B to 2-L, 2-V to 2-X, and [% Mn] / [% Cr] A value of 0 ⁇ 3 or more and less than 1.0, [% V] / [% ⁇ ] A value selected from 8.0 to 30.0, and one selected from Cu, Ni, Nb, and Mo It can also be seen that the wear resistance, fatigue damage resistance, and delayed fracture resistance are improved by adding two or more components within the appropriate ranges. Also, in the examples of the invention, DI values from 5.6 to 8.6 and Ce ⁇ 1 values from 1.04 to 1.27, such as 2-B to 2-H and 2-V to 2-X. It can be seen that the wear resistance and fatigue damage resistance are improved by controlling to 2–I to 2–L. Furthermore, it can be seen that fatigue resistance is reduced when Ti is added, as in 2-U.
  • a pearlite steel rail having wear resistance, fatigue damage resistance, and delayed fracture resistance that is far superior to conventional pearlite steel rails. It contributes to extending the life of railway steel steel rails and preventing railway accidents, and has industrially beneficial effects.
  • Industrial applicability it becomes possible to stably manufacture a pearlite steel rail having much higher wear resistance, fatigue damage resistance and delayed fracture resistance than conventional pearlite steel rails. This contributes to longer life of pearlitic steel rails for axle load railways and prevention of railway accidents, and has beneficial industrial effects.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatment Of Steel (AREA)
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Abstract

L'invention porte sur un rail en acier perlitique à dureté interne élevée dont la résistance à l'usure, à la rupture par fatigue et à la fracture retardée sont excellentes ainsi que sur son procédé approprié de fabrication. De façon spécifique, l'invention porte sur un rail en acier perlitique contenant en masse C : 0,73 à 0,85 %, Si : 0,5 à 0,75 %, Mn : 0,3 à 1,0 %, P : 0,035 % ou au-dessous, S : 0,0005 à 0,012 %, Cr : 0,2 à 1,3 %, V : 0,005 à 0,12 % et N : 0,0015 à 0,0060 %, le complément consistant en Fe et les impuretés inévitables, et ayant un rapport [%Mn]/[%Cr] de 0,3 ou au-dessus et au-dessous de 1,0 (dans lequel [%Mn] représente la teneur en Mn et [%Cr] représente la teneur en Cr) et un rapport [%V]/[%N] de 8,0 à 30,0 (dans lequel [%V] représente la teneur en V et [%N] représente la teneur en N) et dont le champignon de rail présente une dureté interne de Hv380 ou au-dessus et au-dessous de Hv480 en termes de dureté Vickers (Hv) dans une plage de profondeur d'au moins 25 mm à partir de la surface du champignon de rail.
PCT/JP2008/056273 2007-10-10 2008-03-25 Rail en acier perlitique à dureté interne élevée dont la résistance à l'usure, à la rupture par fatigue et à la fracture retardée sont excellentes ainsi que son procédé de fabrication WO2009047926A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
CN2008800203846A CN101743334B (zh) 2007-10-10 2008-03-25 耐磨损性、耐疲劳损伤性及耐延迟断裂性优良的内部高硬度型珠光体钢轨及其制造方法
EP08739390.6A EP2196552B1 (fr) 2007-10-10 2008-03-25 Rail en acier perlitique à dureté interne élevée dont la résistance à l'usure, à la rupture par fatigue et à la fracture retardée sont excellentes ainsi que son procédé de fabrication
CA2687438A CA2687438C (fr) 2007-10-10 2008-03-25 Rail en acier perlitique a durete interne elevee dont la resistance a l'usure, a la rupture par fatigue et a la fracture retardee sont excellentes ainsi que son procede de fabrication
US12/663,866 US20100186857A1 (en) 2007-10-10 2008-03-25 Internal high hardness type pearlitic rail with excellent wear resistance, rolling contact fatigue resistance, and delayed fracture property and method for producing same
AU2008310503A AU2008310503B2 (en) 2007-10-10 2008-03-25 Internal high hardness type pearlitic rail with excellent wear resistance, rolling contact fatigue resistance, and delayed fracture property and method for producing same

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JP2007-264826 2007-10-10
JP2007264826 2007-10-10

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US8241442B2 (en) 2009-12-14 2012-08-14 Arcelormittal Investigacion Y Desarrollo, S.L. Method of making a hypereutectoid, head-hardened steel rail
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JP6288262B2 (ja) * 2014-05-29 2018-03-07 新日鐵住金株式会社 レールおよびその製造方法
WO2015190088A1 (fr) * 2014-06-11 2015-12-17 Ｊｆｅスチール株式会社 Roue pour wagon de chemin de fer et procédé de fabrication de roue pour wagon de chemin de fer
CN104060187B (zh) * 2014-07-14 2016-08-17 攀钢集团攀枝花钢铁研究院有限公司 耐腐蚀性的微合金化钢和钢轨及其制备方法
CN104213037A (zh) * 2014-09-07 2014-12-17 钢铁研究总院 一种高氮珠光体钢
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CN104988405B (zh) * 2015-07-23 2017-03-08 攀钢集团攀枝花钢铁研究院有限公司 一种客货混运用钢轨及其生产方法和应用
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JP5292875B2 (ja) 2013-09-18
CN101743334A (zh) 2010-06-16
CN101743334B (zh) 2012-04-04
CA2687438C (fr) 2012-12-18
EP2196552A1 (fr) 2010-06-16
EP2196552A4 (fr) 2015-12-23
AU2008310503A1 (en) 2009-04-16
EP2196552B1 (fr) 2017-05-10
CA2687438A1 (fr) 2009-04-16
JP2009108396A (ja) 2009-05-21
AU2008310503B2 (en) 2010-12-09

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