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WO2024202406A1 - Rail et son procédé de fabrication - Google Patents

Rail et son procédé de fabrication Download PDF

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Publication number
WO2024202406A1
WO2024202406A1 PCT/JP2024/001011 JP2024001011W WO2024202406A1 WO 2024202406 A1 WO2024202406 A1 WO 2024202406A1 JP 2024001011 W JP2024001011 W JP 2024001011W WO 2024202406 A1 WO2024202406 A1 WO 2024202406A1
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Prior art keywords
rail
less
content
cooling
mpa
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Japanese (ja)
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稔 本庄
佳祐 安藤
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JFE Steel Corp
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JFE Steel Corp
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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
    • 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
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to rails and their manufacturing methods.
  • rail transport is highly efficient and environmentally friendly, so there has been active effort to increase transport capacity by increasing operating speeds, increasing freight car loads, and congesting timetables.
  • the number of wheels passing over the rails is also increasing, and repeated tensile and compressive stresses are being applied to the rails, causing them to break from the bottom, and the frequency of rail replacement is gradually increasing, becoming a problem. For this reason, there is a growing demand for rail steel that is less susceptible to breakage from the bottom.
  • Patent Document 1 discloses a steel rail with a pearlite structure containing 0.65 to 1.40% C, in which at least a portion of the area extending from the bottom surface to a depth of 10 mm contains 200 or more pearlite blocks with grain sizes of 1 to 15 ⁇ m per 0.2 mm2 of an examination area.
  • Patent Document 2 discloses a rail in which the rail head is accelerated-cooled from the austenite region after rolling, while the rail bottom is accelerated-cooled between 800 and 450°C at a cooling rate of 1 to 5°C/sec, resulting in an average pearlite hardness at the rail bottom of HB 320 or more.
  • Patent Document 3 discloses a rail that contains, by mass, 0.65-1.20% C, 0.05-2.00% Si, 0.05-2.00% Mn, with the remainder being Fe and unavoidable impurities, with 97% or more of the head and bottom surfaces being pearlite structures, with the surface hardness of the pearlite structure being in the range of Hv320-500, the maximum surface roughness being 180 ⁇ m or less, and the ratio of the surface hardness to the maximum surface roughness being 3.5 or more.
  • JP 2006-57127 A Japanese Patent Application Laid-Open No. 1-139724 International Publication No. 2011/021582
  • the rails in Patent Documents 1 to 3 mentioned above can control the structure of the rail bottom and increase the strength of the rail bottom, but this alone does not sufficiently suppress the occurrence of cracks in the rail bottom or control the resistance to fracture when a mechanical load is applied if the rail bottom has cracks, and there is a risk of breakage from the rail bottom.
  • the present invention has been made to solve this problem, and provides a rail, together with a manufacturing method thereof, that can prevent breakage from the bottom of the rail by controlling the component composition of the rail and controlling the 0.2% yield strength and fracture toughness values of the rail bottom within respective prescribed ranges, thereby preventing cracks from occurring at the bottom of the rail and increasing resistance to cracks.
  • the gist and configuration of the present invention are as follows. [1] In mass%, C: 0.60% or more but less than 0.90% Si: 0.10-1.20%, Mn: 0.10-1.50%, Cr: 0.05-2.00%, Al: 0.0002-0.005%, P: 0-0.035%, S: 0-0.020%, V: 0-0.30%, Cu: 0-1.0%, Ni: 0-1.0%, Nb: 0-0.05%, Mo: 0-0.5%, B: 0 to 0.0050%, Ti: 0-0.01%, Mg: 0-0.01%, Ca: 0-0.02%, W: 0-0.10%, Sb: 0-0.05%, Sn: 0 to 0.05%, and Cobalt: 0-1.0% The balance is Fe and unavoidable impurities.
  • the 0.2% proof stress of the rail bottom is more than 500 MPa and less than 1,100 MPa, and the fracture toughness of the rail bottom at -20°C is 26.0 MPa m1 /2 or more. rail.
  • the composition of the components is, in mass% V: 0.001 to 0.30%, Cu: 0.001-1.0%, Ni: 0.001-1.0%, Nb: 0.001-0.05%, Mo: 0.001-0.5%, B: 0.0001-0.0050%, Ti: 0.001-0.01%, Mg: 0.0005-0.01%, Ca: 0.0005-0.02%, W: 0.001-0.10%, Sb: 0.001-0.05%, Sn: 0.001 to 0.05%, and Cobalt: 0.001-1.0% Contains one or more selected from the group consisting of [1] Rail.
  • a method for manufacturing a rail according to [1] or [2] A method for manufacturing a rail, comprising the steps of hot rolling a steel bloom having the chemical composition as defined in [1] or [2], and then cooling the bottom center of the rail from a cooling start point T1 to a cooling end point T2 at an average cooling rate of 0.4°C/sec or more and 6.0°C/sec or less, wherein T1 is a temperature in the range of 650°C or more and 800°C or less, and T2 is a temperature in the range of 400°C or more and 600°C or less.
  • the 0.2% proof stress of the rail bottom and the fatigue crack propagation rate when the stress intensity factor range ⁇ K at the rail bottom is 15 MPa m 1/2 are values measured by the method described in the examples.
  • the present invention can provide a rail that can suppress the occurrence of cracks at the rail bottom, and if the rail bottom has a crack, can increase resistance to destruction when a mechanical load is applied, thereby suppressing breakage from the rail bottom, together with a manufacturing method thereof.
  • FIG. FIG. 2 is a diagram showing the cross-sectional area and thickness of the bottom of the rail.
  • FIG. 2 is a diagram showing the positions at which tensile test specimens were taken.
  • FIG. 1 is a diagram showing dimensions of a tensile test specimen.
  • FIG. 2 is a diagram showing the positions at which fracture toughness test pieces were taken.
  • FIG. 1 is a diagram showing the dimensions of a fracture toughness test specimen.
  • C 0.60% or more and less than 0.90%
  • C is an essential element for forming cementite in pearlite structure and ensuring 0.2% proof stress, and the 0.2% proof stress improves with increasing content. If the C content is less than 0.60%, it is difficult to obtain excellent 0.2% proof stress and fracture toughness. Therefore, the C content is set to 0.60% or more, preferably 0.63% or more, and more preferably 0.70% or more. If it is 0.90% or more, proeutectoid cementite is formed at the austenite grain boundary during transformation after hot rolling, and the toughness of the rail against fracture decreases, resulting in a significant decrease in fracture toughness. Therefore, the C content is set to less than 0.90%, preferably 0.89% or less, and more preferably 0.85% or less.
  • Si 0.10-1.20%
  • Silicon is a deoxidizing agent and a strengthening element for pearlite structure, and in order to obtain the effect sufficiently, 0.10% or more is necessary.
  • the silicon content is preferably 0.15% or more, more preferably 0.20% or more. If the silicon content exceeds 1.20%, martensite structure is easily generated, and the 0.2% proof stress increases, and the oxide of silicon also increases, so the fracture toughness value decreases.
  • the silicon content is 1.20% or less, preferably 1.10% or less, and more preferably 1.00% or less.
  • Mn 0.10-1.50%
  • Mn is an element that strengthens the pearlite structure, and in order to fully obtain its effect, 0.10% or more is necessary.
  • the Mn content is preferably 0.20% or more, and more preferably 0.30% or more. If the Mn content exceeds 1.50%, the high hardenability of Mn makes it easier for martensite structure to form, and the 0.2% proof stress increases excessively, and the fracture toughness value may decrease. Therefore, the Mn content is set to 1.50% or less, preferably 1.40% or less, and more preferably 1.30% or less.
  • the P content is set to 0.035% or less, and preferably 0.020% or less. There is no particular lower limit for the P content, and it may be 0%, but to set it to less than 0.001% would necessitate an increase in steelmaking costs, so the P content may be set to 0.001% or more.
  • S is an element that exists in steel mainly in the form of A-type inclusions, but if the S content exceeds 0.020%, the amount of these inclusions increases significantly and at the same time coarse inclusions are generated, which deteriorates the cleanliness of the rail steel and reduces the fracture toughness value of the rail. Therefore, the S content is set to 0.020% or less, preferably 0.015% or less, and more preferably 0.010% or less.
  • the lower limit of the S content is not particularly limited and may be 0%, but since a content of less than 0.0005% would necessitate an increase in steelmaking costs, the S content may be set to 0.0005% or more.
  • Cr 0.05% or more and 2.00% or less Cr is an element that increases the pearlite equilibrium transformation temperature and contributes to refinement of lamellar spacing. At the same time, by including Cr, it is possible to further increase the 0.2% proof stress by solid solution strengthening. If the Cr content is less than 0.05%, sufficient 0.2% proof stress cannot be obtained, so the Cr content is set to 0.05% or more, preferably 0.10% or more, and more preferably 0.15% or more. If the Cr content exceeds 2.00%, the hardenability increases and martensite structure is easily formed, so that the 0.2% proof stress increases and the fracture toughness value decreases. Therefore, the Cr content is set to 2.00% or less, preferably 1.60% or less, and more preferably 1.40% or less.
  • Al 0.0002-0.005%
  • Al is a deoxidizer and strengthens the pearlite structure, and 0.0002% or more is necessary to fully obtain this effect. If the Al content exceeds 0.005%, the 0.2% proof stress increases and the amount of Al oxide increases, decreasing the fracture toughness value. Therefore, the Al content is set to 0.0002-0.005%.
  • the component composition of the rail of the present invention may contain, in addition to the above basic components, one or more components selected from the following: V: 0-0.30%, Cu: 0-1.0%, Ni: 0-1.0%, Nb: 0-0.05%, Mo: 0-0.5%, B: 0-0.0050%, Ti: 0-0.01%, Mg: 0-0.01%, Ca: 0-0.02%, W: 0-0.10%, Sb: 0-0.05%, Sn: 0-0.05 %, and Co: 0 to 1.0%.
  • V 0-0.30%
  • Cu 0-1.0%
  • Ni: 0-1.0% Ni: 0-1.0%
  • Nb 0-0.05%
  • Mo 0-0.5%
  • B 0-0.0050%
  • Ti 0-0.01%
  • Mg 0-0.01%
  • Ca 0-0.02%
  • W 0-0.10%
  • Sb 0-0.05%
  • Sn 0-0.05 %
  • Co 0 to 1.0%.
  • V 0.001 to 0.30%
  • V is an element that forms carbonitrides in steel, disperses and precipitates in the matrix, and improves the fracture toughness value through the improvement of the 0.2% proof stress. This effect is exhibited when the V content is 0.001% or more, so when V is contained, the V content is preferably 0.001% or more, and more preferably 0.005% or more. On the other hand, when the V content exceeds 0.30%, the 0.2% proof stress increases excessively, and the fracture toughness value may decrease. In addition, the alloy cost increases, and the cost of the rail steel increases. Therefore, when V is contained, the V content is preferably 0.30% or less, and more preferably 0.29% or less.
  • Cu 0.001-1.0% Like Cr, Cu is an element that can further increase strength through solid solution strengthening. If the Cu content is less than 0.001%, the effect is small, while if it exceeds 1.0%, Cu cracking is likely to occur. Therefore, if Cu is contained, the Cu content is preferably 0.001 to 1.0%.
  • Ni 0.001-1.0%
  • Ni is an element that can increase strength without deteriorating ductility. In addition, when added in combination with Cu, it suppresses Cu cracking, so it is desirable to add Ni when Cu is added. If the Ni content is less than 0.001%, the effect is small, while if it exceeds 1.0%, the hardenability increases, martensite is formed, and the fracture toughness value tends to decrease. Therefore, if Ni is added, the Ni content is preferably 0.001 to 1.0%.
  • Nb 0.001-0.05%
  • Nb is an element that combines with C in steel to precipitate as carbides during and after rolling, improving the 0.2% yield strength and thereby improving the fracture toughness value, but if the Nb content is less than 0.001%, the effect is small, while if it is contained in excess of 0.05%, no effect commensurate with the content can be obtained. Therefore, when Nb is contained, the Nb content is preferably 0.001 to 0.05%.
  • Mo 0.001-0.5%
  • Mo is an element that can further increase strength through solid solution strengthening, but if it is less than 0.001%, this effect is small, while if it exceeds 0.5%, the hardenability increases, martensite is formed, and the fracture toughness value tends to decrease. Therefore, if Mo is contained, the Mo content is preferably 0.001 to 0.5%.
  • B 0.0001-0.0050%
  • B is an element that precipitates as a nitride and can further increase the strength of rails through precipitation strengthening. If the B content is less than 0.0001%, the effect is small, while if it exceeds 0.0050%, it leads to an increase in alloy costs. Therefore, if B is contained, the B content is preferably 0.0001 to 0.0050%.
  • Ti 0.001-0.01%
  • Ti is an element that precipitates as carbide, nitride, or carbonitride, and can further increase the strength of rails through precipitation strengthening. If the Ti content is less than 0.001%, the effect is small, while if it exceeds 0.01%, it leads to an increase in alloy costs. Therefore, if Ti is contained, the Ti content is preferably 0.001 to 0.01%.
  • Mg 0.0005-0.01%
  • Mg is an element that can combine with oxygen to precipitate MgO, thereby further increasing strength. If the Mg content is less than 0.0005%, the effect is small, while if it exceeds 0.01%, the increase in MgO tends to cause a decrease in fracture toughness. Therefore, if Mg is added, the Mg content is preferably 0.0005 to 0.01%.
  • Ca 0.0005-0.02%
  • Ca is an element that can combine with oxygen to precipitate CaO, thereby further increasing strength. If the Ca content is less than 0.0005%, the effect is small, while if it exceeds 0.02%, the increase in CaO makes it easier for fracture toughness to occur. Therefore, if Ca is added, the Ca content is preferably 0.0005 to 0.02%.
  • W 0.001 to 0.10%
  • W is an element that precipitates as carbides and can further increase the strength of rails through precipitation strengthening. If the W content is less than 0.001%, the effect is small, while if it exceeds 0.10%, it leads to an increase in alloy costs. Therefore, if W is added, the W content is preferably 0.001 to 0.10%.
  • Sb 0.001-0.05%
  • Sb is an element that has a remarkable effect of preventing decarburization of steel during reheating of rail steel pieces in a heating furnace before hot rolling. If the Sb content exceeds 0.05%, it adversely affects the ductility and toughness of steel, so if Sb is contained, the Sb content is preferably 0.05% or less. On the other hand, if Sb is contained, the Sb content is preferably 0.001% or more in order to exert the effect of reducing the decarburized layer.
  • Sn 0.001-0.05%
  • Sn is an element that has a remarkable effect of preventing decarburization of steel during reheating of rail steel pieces in a heating furnace before hot rolling. If the Sn content exceeds 0.05%, it adversely affects the ductility and toughness of the steel, so if Sn is contained, the Sn content is preferably 0.05% or less. On the other hand, if Sn is contained, the Sn content is preferably 0.001% or more in order to exert the effect of reducing the decarburized layer.
  • Co 0.001-1.0%
  • Co is an element that can increase the pearlite equilibrium transformation temperature and refine the lamellar spacing, thereby further increasing the strength of the steel. Co also has the effect of suppressing the precipitation of proeutectoid cementite. If the Co content exceeds 1.0%, martensite is formed in the steel, resulting in a decrease in ductility. From these points of view, when the composition contains Co, the Co content is preferably 1.0% or less. There is no particular limit to the lower limit of the Co content, but it is preferably 0.001% or more in order to increase the strength. A more preferable range of the Co content is 0.001 to 0.5%.
  • the balance of the above essential and optional components consists of Fe and unavoidable impurities.
  • unavoidable impurities include N and O, with N being permitted up to 0.008% and O being permitted up to 0.004%.
  • impurities other than N and O may be unavoidably mixed into the steel depending on the conditions of the raw materials, materials, manufacturing equipment, etc. Examples of raw materials include iron ore, reduced iron, and scrap. The above impurities are permitted to be mixed in as long as they do not impede the objectives of the present invention.
  • impurities other than N and O include Pb, Zr, Bi, Zn, Se, As, Te, Tl, Cd, Hf, Ag, Hg, Ga, Ge, REM, etc.
  • the microstructure of the rail of the present invention is pearlite at an area ratio of 95% or more at the bottom of the rail.
  • the remaining structure other than pearlite is permissible as long as the total area ratio is 5% or less since it does not significantly affect the characteristics of the present invention. Examples of the remaining structure include ferrite and bainite.
  • the microstructure can be identified by the method described in the Examples.
  • the rail of the present invention has a 0.2% yield strength in the range of more than 500 MPa and less than 1100 MPa. If the 0.2% yield strength is 500 MPa or less, cracks are likely to occur at the rail bottom due to stress generated in the rail when a wheel passes over it, because resistance to cracks is weak. On the other hand, if the 0.2% yield strength is 1100 MPa or more, the strength of the rail bottom becomes high, so that the sensitivity to cracks after crack occurrence increases, and the rail is more likely to break. Therefore, the 0.2% yield strength of the rail bottom is made to be more than 500 MPa, preferably 501 MPa or more, and more preferably 570 MPa or more. The 0.2% yield strength of the rail bottom is made to be less than 1100 MPa, preferably 1099 MPa or less, and more preferably 1060 MPa or less.
  • the rail of the present invention has a fracture toughness value at -20°C of 26 MPa m 1/2 or more.
  • the fracture toughness value is the resistance to fracture when a mechanical load is applied to the rail bottom when the rail bottom has a crack. If the value is less than 26 MPa m 1/2 , the resistance to fracture is small, and the rail is particularly likely to break under assumed conditions of use, including use in cold regions. Therefore, the fracture toughness value at the rail bottom is 26 MPa m 1/2 or more, preferably 27 Pa m 1/2 or more. There is no particular upper limit to the fracture toughness value, but it can be, for example, 50 Pa m 1/2 or less.
  • the fracture toughness value is set to a value at -20°C in consideration of use in cold regions.
  • the shape of the rail in the present invention is not particularly limited, and may be any shape described in JIS E 1101:2001, BS EN13674-1:2011, American Railway Engineering and Maintenance-of-Way Association (AREMA), or the like.
  • AREMA American Railway Engineering and Maintenance-of-Way Association
  • the manufacturing method of the rail of the present invention will be described.
  • the rail of the present invention can be manufactured by hot rolling a steel bloom having the above-mentioned composition, and then cooling the center of the bottom of the rail at an average cooling rate of 0.4°C/sec to 6.0°C/sec from the cooling start point T1 to the cooling end point T2 .
  • the cooling start point T1 is at a temperature in the range of 650°C to 800°C.
  • the cooling start point T1 and the cooling stop point T2 are surface temperatures at the center of the bottom of the rail measured with a radiation thermometer, and the average cooling rate is the difference between the cooling start point T1 and the cooling stop point T2 at the center of the bottom divided by the time required for cooling.
  • the blooms used as rail materials have the above-mentioned rail composition and can be produced by any method. They can be produced by casting, particularly continuous casting. For example, steel can be smelted in a converter or electric furnace, and if necessary, secondary refining such as degassing is performed to adjust the composition of the steel to the above range, and the smelted steel can then be continuously cast into a bloom.
  • the slab can be heated to 1200°C to 1350°C in a heating furnace and then hot rolled.
  • hot rolling can be performed using a breakdown rolling mill, a rough rolling mill, and a finishing rolling mill.
  • the austenite grains that have become coarse due to heating can be refined by rolling in the recrystallization temperature range and recrystallization, or the structure after pearlite transformation can be refined by introducing strain in the non-recrystallization temperature range.
  • the rolling end temperature of the bottom (foot) part during hot rolling is 800°C or higher and 1000°C or lower.
  • the hot rolling is preferably carried out at a temperature of 1050° C. or less so that the area reduction rate of the bottom part is 11% or more, more preferably 13% or more.
  • the area reduction rate can be 20% or less, preferably 18% or less.
  • S0 is the cross-sectional area of the bottom part when the temperature drops to 1050°C or less
  • S1 is the cross-sectional area of the bottom part after finish rolling.
  • the reduction rate (thickness reduction rate) in the thickness direction of the bottom is the same as or larger than the cross-sectional area reduction rate of the pass.
  • the finish rolling here refers to one final rolling pass of rolling performed with a final rolling groove of one final rolling mill.
  • the thickness reduction rate at the center of the bottom is set to 15% or more. This allows a large shear strain to be introduced into the bottom, which can further promote the refinement of the structure after pearlite transformation, and can effectively increase the toughness of the back surface of the bottom.
  • the groove so that the width dimension of the bottom is expanded in this finish rolling, rolling with a relatively large thickness reduction rate compared to the cross-sectional area reduction rate can be stably performed.
  • the cross-sectional area of the bottom of the rail is the area of the shaded portion marked with S in the cross-sectional view of the rail in Figure 2, and the thickness of the bottom of the rail is the height marked with H in the same figure.
  • accelerated cooling is performed at a predetermined average cooling rate for the center of the bottom portion of the rail.
  • the cooling start point T1 of the accelerated cooling is a temperature in the range of 650°C to 800°C. If the cooling start point is less than 650°C, the pearlite transformation temperature increases and the 0.2% proof stress decreases. On the other hand, if cooling is performed from above 800°C, martensite tends to form at the bottom of the rail, and the 0.2% proof stress increases, tending to decrease the fracture toughness value. For this reason, the cooling start point is set to 650°C to 800°C.
  • the cooling stop point T2 is a temperature in the range of 400°C to 600°C. If the cooling stop point is less than 400°C, cooling will continue even after the pearlite transformation is complete, which increases the cooling time and reduces productivity. On the other hand, if the cooling stop point is more than 600°C, cooling will be stopped before the pearlite transformation is complete, which will result in a decrease in 0.2% yield strength. Therefore, the cooling stop point is set to 400°C to 600°C.
  • the average cooling rate from the cooling start point T1 to the cooling end point T2 is 0.4°C/sec or more and 6.0°C/sec or less. If the average cooling rate is less than 0.4°C/sec, the 0.2% proof stress of the rail bottom decreases, resulting in a decrease in fracture toughness value. On the other hand, if the average cooling rate exceeds 6.0°C/sec, the 0.2% proof stress of the rail bottom increases, resulting in a decrease in fracture toughness value. Therefore, it is preferable that the average cooling rate during accelerated cooling is 0.4°C/sec or more and 6.0°C/sec or less, and 0.9°C/sec or more and less than 3.0°C/sec.
  • the accelerated cooling method is not particularly limited, and can be, for example, a cooling method using online heat treatment equipment.
  • the cooling medium is not particularly limited, and can be one or more selected from air, spray water, mist, etc., but it is preferable to use air.
  • the base (foot) may be accelerated cooled by air to control the average cooling rate of the center of the base, while other parts of the rail (e.g., rail head, etc.) may be allowed to cool naturally or may be accelerated cooled in the same manner as the base (foot).
  • the rail material may be subjected to known treatments, for example, cold roller straightening.
  • a steel slab having the chemical composition shown in Table 1 was heated to 1250°C and then hot rolled into a rail shape (60 kg rail as specified in JIS E 1101:2001) at the finishing rolling temperature shown in Table 2.
  • the area reduction rate of the bottom portion during rolling at 1050°C or less and the thickness reduction rate of the bottom center portion during finish rolling, which is the final rolling pass, were set to satisfy the values shown in Table 2.
  • the rail thus obtained was then transported to an online heat treatment facility, where the center of the bottom of the rail was cooled under the cooling conditions shown in Table 2.
  • the cooling was performed by injecting air using an air injector.
  • the rail was then transferred to a cooling bed and allowed to cool to room temperature.
  • the cooling start point and cooling stop point in Table 2 are the surface temperatures at the corresponding positions measured using a two-dimensional radiation thermometer that can measure the temperature distribution at the center of the bottom of the rail, and the average cooling rate is the average cooling rate between these temperatures.
  • Test pieces according to ASTM E1820-09 were taken from the rail positions shown in Figure 5. The shape of the test pieces is shown in Figure 6. The test pieces were subjected to testing at a test temperature of -20°C using a Shimadzu 250KN autograph testing machine according to ASTM E1820-09 to determine the fracture toughness value.
  • ⁇ Drop weight test> A 1500mm long rail was taken from the manufactured rail, and a hole with a diameter of 1.0mm and a depth of 1.0mm was drilled in the center of the bottom of the rail, 750mm from the end, and a drop weight test was carried out with the rail head facing up and a weight dropped from a height of 300mm. All other test conditions were in accordance with JIS E1101. The drop weight test was used to check for the presence or absence of rail breakage, and rails without breakage were judged to be in good condition.
  • the present invention can provide a rail that can suppress the occurrence of cracks at the rail bottom, and, if the rail bottom has a crack, can increase resistance to destruction when a mechanical load is applied, thereby suppressing breakage from the rail bottom, together with a manufacturing method thereof, and is highly useful industrially.

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Abstract

L'invention concerne un rail capable de supprimer la rupture d'une partie inférieure de rail. Ledit rail a une composition de composant contenant, en termes de % en masse, 0,60 % ou plus et moins de 0,90 % de C, 0,10 à 1,20 % de Si, 0,10 à 1,50 % de Mn, 0,05 à 2,00 % de Cr, 0,0002 à 0,005 % d'Al, 0 à 0,035 % de P, 0 à 0,020 % de S, 0 à 0,30 % de V, 0 à 1,0 % de Cu, 0 à 1,0 % de Ni, 0 à 0,05 % de Nb, 0 à 0,5 % de Mo, 0 à 0,0050 % de B, 0 à 0,01 % de Ti, 0 à 0,01 % de Mg, 0 à 0,02 % de Ca, 0 à 0,10 % de W, 0 à 0,05 % de Sb, 0 à 0,05 % de Sn, et 0 à 1,0 % de Co, le reste étant du Fe et des impuretés inévitables, la limite d'élasticité à 0,2 % d'une partie inférieure de rail étant supérieure à 500 MPa et inférieure à 1 100 MPa, et la ténacité à la rupture à -20 °C de la partie inférieure de rail étant de 26,0 MPa m1/2 ou plus.
PCT/JP2024/001011 2023-03-24 2024-01-16 Rail et son procédé de fabrication Pending WO2024202406A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014157252A1 (fr) * 2013-03-27 2014-10-02 Ｊｆｅスチール株式会社 Rail en perlite et procédé permettant de fabriquer un rail en perlite
WO2016047076A1 (fr) * 2014-09-22 2016-03-31 Ｊｆｅスチール株式会社 Procédé de fabrication de rail et appareil de fabrication de rail
WO2016117692A1 (fr) * 2015-01-23 2016-07-28 新日鐵住金株式会社 Rail
WO2018168969A1 (fr) * 2017-03-15 2018-09-20 Ｊｆｅスチール株式会社 Dispositif de refroidissement et procédé de fabrication d'un rail
CN112239831A (zh) * 2020-10-19 2021-01-19 攀钢集团攀枝花钢铁研究院有限公司 高韧高寒铁路钢轨及其生产方法
CN114855082A (zh) * 2022-04-26 2022-08-05 包头钢铁（集团）有限责任公司 一种稀土元素提高热轧u75v钢轨低温韧性制造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014157252A1 (fr) * 2013-03-27 2014-10-02 Ｊｆｅスチール株式会社 Rail en perlite et procédé permettant de fabriquer un rail en perlite
WO2016047076A1 (fr) * 2014-09-22 2016-03-31 Ｊｆｅスチール株式会社 Procédé de fabrication de rail et appareil de fabrication de rail
WO2016117692A1 (fr) * 2015-01-23 2016-07-28 新日鐵住金株式会社 Rail
WO2018168969A1 (fr) * 2017-03-15 2018-09-20 Ｊｆｅスチール株式会社 Dispositif de refroidissement et procédé de fabrication d'un rail
CN112239831A (zh) * 2020-10-19 2021-01-19 攀钢集团攀枝花钢铁研究院有限公司 高韧高寒铁路钢轨及其生产方法
CN114855082A (zh) * 2022-04-26 2022-08-05 包头钢铁（集团）有限责任公司 一种稀土元素提高热轧u75v钢轨低温韧性制造方法

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