WO2022004247A1 - Rail having excellent fatigue crack propagation resistance characteristics, and method for producing same - Google Patents
Rail having excellent fatigue crack propagation resistance characteristics, and method for producing same Download PDFInfo
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- WO2022004247A1 WO2022004247A1 PCT/JP2021/020871 JP2021020871W WO2022004247A1 WO 2022004247 A1 WO2022004247 A1 WO 2022004247A1 JP 2021020871 W JP2021020871 W JP 2021020871W WO 2022004247 A1 WO2022004247 A1 WO 2022004247A1
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 23
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 38
- 239000010959 steel Substances 0.000 claims abstract description 38
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 26
- 239000000463 material Substances 0.000 claims abstract description 24
- 239000000203 mixture Substances 0.000 claims abstract description 20
- 239000013256 coordination polymer Substances 0.000 claims abstract description 13
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 7
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 238000001816 cooling Methods 0.000 claims description 58
- 238000005098 hot rolling Methods 0.000 claims description 22
- 238000000034 method Methods 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 16
- 238000010438 heat treatment Methods 0.000 claims description 13
- 230000001133 acceleration Effects 0.000 claims description 2
- 238000012360 testing method Methods 0.000 description 36
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 26
- 229910001567 cementite Inorganic materials 0.000 description 23
- 238000005096 rolling process Methods 0.000 description 18
- 230000000694 effects Effects 0.000 description 11
- 229910001562 pearlite Inorganic materials 0.000 description 11
- 229910000734 martensite Inorganic materials 0.000 description 10
- 230000005496 eutectics Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 230000005855 radiation Effects 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 229910001563 bainite Inorganic materials 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
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- 238000005336 cracking Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
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- 239000006104 solid solution Substances 0.000 description 2
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- 239000002344 surface layer Substances 0.000 description 2
- 239000004365 Protease Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
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- 229910052721 tungsten Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
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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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- 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 a rail and a method for manufacturing the rail, and the present invention relates to a rail having improved fatigue crack propagation characteristics and a method for manufacturing the rail which can advantageously manufacture the rail.
- the high-axis heavy railway is a railway having a large load weight (for example, a load weight of about 150 tons or more) of one freight car such as a train or a freight car.
- Patent Document 1 and Patent Document 2 the C content is increased from 0.85% by mass to 1.20% by mass or less. Further, in Patent Document 3 and Patent Document 4, the C content is more than 0.85% by mass and 1.20% by mass or less, and the rail head is heat-treated. In these techniques, the wear resistance is improved by increasing the cementite fraction by increasing the C content.
- Patent Document 5 proposes a technique of suppressing the formation of proeutectoid cementite by adding Al and Si and improving fatigue damage resistance. Further, Patent Document 6 proposes a technique for reducing the fatigue crack propagation rate by controlling the lamellar spacing of pearlite within an appropriate range.
- the pro-eutectoid cementite structure may be formed depending on the combination of the components and the production conditions, and as a result, the fatigue crack propagation rate increases, so that the material control is sufficient. It's hard to say.
- the present invention has been made to advantageously solve the above-mentioned problems, and an object of the present invention is to provide a rail having excellent fatigue damage resistance, particularly fatigue crack propagation characteristics, together with a preferable manufacturing method thereof.
- the inventors have manufactured rails having different contents of C, Si, Mn and Cr, and have diligently investigated the structure and fatigue crack propagation characteristics.
- the parameter CP was derived from the component parameter X corresponding to the amount of pro-eutectoid cementite and the old austenite particle size RA. Then, they have found that by controlling the parameter CP within a predetermined range, excellent fatigue-resistant crack propagation characteristics can be obtained even if a large amount of pro-eutectoid cementite is present.
- the rails having excellent fatigue crack propagation characteristics according to the present invention developed to solve the above problems and realize the above objects have C: 0.80 to 1.30% by mass and Si: 0.10 to 1. Contains 20% by mass, Mn: 0.20 to 1.80% by mass, P: 0.035% by mass or less, S: 0.0005 to 0.012% by mass, Cr: 0.20 to 2.50% by mass.
- the balance has a component composition consisting of Fe and unavoidable impurities, and the CP represented by the following formula (1) is 2500 or less, where [% Y] is the content (mass%) of the element Y. ),
- RA is characterized by having an old austenite particle size ( ⁇ m).
- CP X / RA ... (1)
- X ⁇ (10 ⁇ [% C]) + ([% Si] / 12) + ([% Mn] / 24) + ([% Cr] / 21) ⁇ 5 ...
- the component composition is V: 0.30% by mass or less, Cu: 1.0% by mass or less, Ni: 1.0% by mass or less, Nb: 0.05% by mass or less, and Mo: 2.0% by mass. Containing at least one selected from the following, b.
- the component composition further includes Al: 0.07% by mass or less, W: 1.0% by mass or less, B: 0.005% by mass or less, Ti: 0.05% by mass or less, and Sb: 0.05% by mass. Containing at least one selected from the following, Etc. may be a more preferable solution.
- the method for manufacturing a rail having excellent fatigue-resistant crack propagation characteristics is to heat a steel material having any of the above component compositions to 1350 ° C. or lower.
- This is a method for manufacturing a rail by hot rolling after performing hot rolling, and is characterized by hot rolling so that the finishing temperature becomes 900 ° C. or higher.
- accelerated cooling is performed from 900 ° C. to 750 ° C. at a cooling rate in the range of 0.4 to 3 ° C./s.
- accelerated cooling from 750 ° C. to a cooling stop temperature of 400 to 600 ° C. at a cooling rate in the range of 1 to 10 ° C./s may be a more preferable solution.
- the rail and the manufacturing method thereof it is possible to stably manufacture a fatigue-resistant damage-resistant rail having excellent fatigue-resistant crack propagation characteristics, and it is possible to extend the life of rails for high-axis heavy railways and railways. It contributes to accident prevention and has an industrially beneficial effect. In addition, it is preferable to optimize the heat treatment conditions after hot rolling because the fatigue damage resistance can be improved.
- FIG. 1 It is a schematic diagram which shows the influence of the analytic cementite on the fatigue crack propagation rate, (a) shows the case where the former austenite grain size and the plastic region dimension are almost equal, and (b) is the former austenite particle diameter in the plastic region. The case where it is larger than the dimension is shown. It is a figure which shows the position where the test piece for observing the old austenite particle size was collected. It is a figure which shows the position where the fatigue crack propagation test piece was collected. It is a figure explaining the test piece shape used for the fatigue crack propagation test, (a) shows the front view, (b) shows the side view, (c) shows the notch part enlarged front view. It is a figure explaining the shape of the test piece used for the fatigue-resistant damage test, (a) shows the side view, and (b) shows the front view. It is a figure which shows the position where the fatigue-resistant damage test piece was collected.
- C 0.80 to 1.30%
- C is an essential element for ensuring the strength of the pearlite structure, that is, the fatigue damage resistance. However, if it is less than 0.80%, it is difficult to obtain excellent fatigue-resistant crack propagation characteristics. On the other hand, if it exceeds 1.30%, a large amount of proeutectoid cementite is generated at the austenite grain boundaries during cooling after hot rolling, which causes an increase in the fatigue crack propagation rate. Although the proeutectoid cementite is present even when it is 1.30% or less, its influence can be avoided by controlling the old austenite particle size based on the relational expression described later. Therefore, the C content is in the range of 0.80 to 1.30%. The upper limit of the C content is preferably 1.00%, more preferably 0.90%.
- Si 0.10 to 1.20%
- Si contributes to a decrease in the fatigue crack propagation rate by increasing the pearlite equilibrium transformation temperature and making the lamellar interval finer. Therefore, 0.10% or more is required, but if it exceeds 1.20%, the weldability deteriorates due to the high bonding force of Si with oxygen. Further, since Si has an action of moving the eutectic point to the low C side, excessive addition promotes the formation of eutectic cementite and causes an increase in the fatigue crack propagation rate. Therefore, the Si content is in the range of 0.10 to 1.20%.
- the lower limit of the Si content is preferably 0.20%
- the upper limit of the Si content is preferably 0.80%, and even more preferably 0.60%.
- Mn 0.20 to 1.80% Mn contributes to a decrease in the fatigue crack propagation rate by lowering the pearlite transformation temperature and making the lamellar interval finer. However, if the Mn content is less than 0.20%, a sufficient effect cannot be obtained. On the other hand, when the Mn content exceeds 1.80%, a martensite structure is likely to be formed, and the material is likely to be deteriorated due to hardening or embrittlement during heat treatment and welding of the rail. Further, since Mn has an action of moving the eutectic point to the low C side, excessive addition promotes the formation of eutectic cementite and causes an increase in the fatigue crack propagation rate. Therefore, the Mn content is in the range of 0.20 to 1.80%. The lower limit of the Mn content is preferably 0.30%, the upper limit of the Mn content is preferably 1.00%, and even more preferably 0.60%.
- the P content is 0.035% or less. It is preferably 0.020% or less.
- the lower limit of the P content is not particularly limited and may be 0%, but industrially, it is usually more than 0%. It should be noted that excessively reducing the P content leads to an increase in refining cost, and therefore, from the viewpoint of economic efficiency, it is preferable to set the P content to 0.001% or more.
- S 0.0005 to 0.012% S is mainly present in steel in the form of A-based inclusions (those that undergo viscous deformation due to processing), but when the content exceeds 0.012%, the amount of these inclusions increases remarkably, and at the same time, it is coarse. Since inclusions are generated, the cleanliness of the steel material deteriorates. Further, if the S content is less than 0.0005%, the refining cost will increase. Therefore, the S content is in the range of 0.0005 to 0.012%. The upper limit of the S content is preferably 0.010%, more preferably 0.008%.
- the Cr content is in the range of 0.20 to 2.50%.
- the lower limit of the Cr content is preferably 0.40%, more preferably 0.50%, and the upper limit of the Cr content is preferably 1.50%, further preferably 1.00%.
- each element is not sufficient for each element to simply satisfy the above range, and it is derived from the component parameter X corresponding to the amount of proeutectoid cementite represented by the following equation (2) and the former austenite particle size RA. It is important to control the CP value represented by the following equation (1) to 2500 or less.
- CP X / RA ...
- X ⁇ (10 ⁇ [% C]) + ([% Si] / 12) + ([% Mn] / 24) + ([% Cr] / 21) ⁇ 5 ... (2)
- [% Y] content of element Y (mass%)
- RA Old austenite particle size ( ⁇ m) Represents.
- the brittle fracture of the proactive cementite 24 at the tip of the fatigue crack 23 causes the increase in the fatigue crack propagation rate 26. I got the finding that it is.
- the particle size of the old austenite, which is the formation site of the structure according to the amount of proactive cementite produced, the frequency of encounters between the plastic region 22 formed at the tip of the fatigue crack and the proactive cementite is reduced. It was found that brittle crack growth can be suppressed.
- the austenite grains 21 are sufficiently coarsened to be larger than the size of the plastic region 22 at the crack tip. This makes it possible to control the CP value to 2500 or less. As a result, the above-mentioned effect of suppressing the fatigue crack propagation rate can be stably obtained.
- the CP value is preferably 2000 or less.
- the component composition of the rail used in the present invention may be any one or both of at least one selected from the following group A and at least one selected from group B below. It may be contained in.
- V 0.30% or less V forms a carbonitride in the steel and disperses and precipitates in the substrate, improving the wear resistance of the steel.
- the content exceeds 0.30%, the processability deteriorates and the manufacturing cost increases.
- the alloy cost increases, so that the cost of the internal high hardness type rail increases. Therefore, V is preferably contained up to 0.30%.
- V is preferably contained in an amount of 0.001% or more.
- the upper limit of the V content is more preferably 0.15%.
- Cu 1.0% or less
- Cu is an element that can further increase the strength of steel by solid solution strengthening like Cr. However, if the content exceeds 1.0%, Cu cracking is likely to occur. Therefore, when Cu is contained in the component composition, the Cu content is preferably 1.0% or less.
- the lower limit of the Cu content is more preferably 0.005%, and the upper limit of the Cu content is more preferably 0.5%.
- Ni 1.0% or less
- Ni is an element that can increase the strength of steel without deteriorating ductility. Further, since Cu cracking can be suppressed by compound addition with Cu, it is desirable that Ni is also contained when Cu is contained in the component composition. However, when the Ni content exceeds 1.0%, the hardenability of the steel is further increased, the amount of martensite and bainite produced is increased, and the wear resistance and the fatigue damage resistance tend to be lowered. Therefore, when Ni is contained, the Ni content is preferably 1.0% or less.
- the lower limit of the Ni content is more preferably 0.005%, and the upper limit of the Ni content is more preferably 0.5%.
- Nb 0.05% or less Nb is combined with C in steel and precipitated as carbide during hot rolling for forming a rail and after hot rolling, and effectively acts on the miniaturization of pearlite colony size.
- wear resistance, fatigue damage resistance, and ductility are greatly improved, which greatly contributes to extending the life of the internal high hardness type rail.
- Nb content exceeds 0.05%, the effect of improving wear resistance and fatigue damage resistance is saturated, and an effect commensurate with the increase in content cannot be obtained. Therefore, Nb may be contained with the upper limit of its content being 0.05%. If the Nb content is less than 0.001%, it is difficult to obtain a sufficient effect on extending the life of the rail. Therefore, when Nb is contained, the Nb content is preferably 0.001% or more. The upper limit of the Nb content is more preferably 0.03%.
- Mo 2.0% or less Mo is an element that can further increase the strength of steel by solid solution strengthening. Further, since Mo has an action of moving the eutectic point to the high C side, it also has an action of suppressing the formation of eutectic cementite. However, if it exceeds 2.0%, the amount of bainite generated in the steel increases and the wear resistance deteriorates. Therefore, when the component composition of the rail contains Mo, the Mo content is preferably 2.0% or less. The lower limit of the Mo content is more preferably 0.005%, and the upper limit of the Mo content is more preferably 1.0%.
- Al 0.07% or less
- Al is an element that can be added as a deoxidizing agent.
- the Al content is preferably 0.07% or less.
- the lower limit of the Al content is not particularly limited, but is preferably 0.001% or more for deoxidation.
- the upper limit of the Al content is more preferably 0.03%.
- W 1.0% or less W is precipitated as carbide during and after hot rolling for forming into a rail shape, and the strength and ductility of the rail are improved by strengthening the precipitation.
- the W content exceeds 1.0%, martensite is formed in the steel, and as a result, the ductility is lowered. Therefore, when W is added, the W content is preferably 1.0% or less.
- the lower limit of the W content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the above-mentioned action of improving strength and ductility.
- the lower limit of the W content is more preferably 0.005%, and the upper limit of the W content is more preferably 0.5%.
- B 0.005% or less B is precipitated as nitride in steel during and after hot rolling for forming into a rail shape, and the strength and ductility of the steel are improved by precipitation strengthening.
- the B content exceeds 0.005%, martensite is formed, and as a result, the ductility of the steel is lowered. Therefore, when B is contained, the B content is preferably 0.005% or less.
- the lower limit of the B content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the above-mentioned action of improving strength and ductility.
- the upper limit of the B content is more preferably 0.003%.
- Ti 0.05% or less Ti precipitates in steel as carbides, nitrides or carbonitrides during and after hot rolling to form a rail shape, and the strength and ductility of the steel are enhanced by precipitation strengthening. Improve. However, if the Ti content exceeds 0.05%, coarse carbides, nitrides or carbonitrides are formed, resulting in a decrease in steel ductility. Therefore, when Ti is contained, the Ti content is preferably 0.05% or less.
- the lower limit of the Ti content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the above-mentioned action of improving strength and ductility. The lower limit of the Ti content is more preferably 0.005%, and the upper limit of the Ti content is more preferably 0.03%.
- Sb 0.05% or less Sb has a remarkable effect of preventing decarburization of the steel during the reheating when the rail steel material is reheated in a heating furnace before hot rolling.
- the Sb content is preferably 0.05% or less.
- the lower limit of the Sb content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the effect of reducing the decarburized layer.
- the lower limit of the Sb content is more preferably 0.005%, and the upper limit of the Sb content is more preferably 0.03%.
- the composition of the steel material used as the material for the rail of the present invention contains the above components, the balance Fe, and unavoidable impurities.
- a rail that contains other trace component elements in place of a part of the balance Fe in the composition according to the present invention within a range that does not substantially affect the action and effect of the present invention also belongs to the present invention.
- examples of the unavoidable impurities include N, O, etc., and N can be allowed up to 0.008% and O can be allowed up to 0.004%.
- the structure other than pearlite in the microstructure of the rail according to the present invention is not particularly limited. If the total area ratio is 5% or less, the fatigue crack propagation characteristics are not significantly affected, so that other tissues are allowed to be present. Examples of the other structures include ferrite, proeutectoid cementite, bainite and martensite.
- the rail of the present invention can be manufactured by sequentially applying the following treatments (1) to (3) to a steel material having the above-mentioned composition.
- (1) Hot rolling (2) Primary cooling
- Secondary cooling The steel material used as the rail material can be manufactured by any method, but in general, the steel material is manufactured by casting, especially continuous casting. Is preferable.
- the hot rolling method is not particularly limited and is performed by any method. be able to.
- Heating temperature 1350 ° C. or lower
- the heating temperature must be 1350 ° C. or lower. If the heating temperature exceeds the upper limit, the steel material may be partially melted due to excessive temperature rise, and defects may occur inside the rail.
- the lower limit of the heating temperature is not particularly limited, but is preferably 1150 ° C. or higher in order to reduce the deformation resistance during rolling.
- Rolling finish temperature 900 ° C or higher
- the rolling finish temperature in the above hot rolling is lower than 900 ° C, rolling is performed in the austenite low temperature range, and not only processing strain is introduced into the austenite crystal grains but also austenite is introduced. The elongation of the crystal grains becomes remarkable. Increasing the austenite grain boundary area increases the nucleation sites of proeutectoid cementite, resulting in a decrease in fatigue-resistant crack propagation characteristics. Therefore, the rolling finish temperature is set to 900 ° C. or higher.
- the upper limit of the rolling finish temperature is not particularly limited, but if the old austenite particle size becomes extremely coarse, the ductility and toughness will decrease, so the temperature is preferably 1050 ° C. or lower.
- the rolling finish temperature referred to here is the temperature of the side surface of the rail head on the entry side of the final rolling mill, and can be measured by a radiation thermometer.
- the upper limit of the average cooling rate of the primary cooling is preferably 3 ° C / s, more preferably 2 ° C / s.
- the average cooling rate of the secondary cooling is preferably in the range of 1 to 10 ° C./s.
- the upper limit of the average cooling rate of the secondary cooling is more preferably 5 ° C./s.
- the temperature for determining the average cooling rate is the surface temperature of the side surface of the rail head, and can be measured by a radiation thermometer.
- the cooling stop temperature at the time of secondary cooling is the temperature measured by a radiation thermometer after the acceleration cooling stop (before reheating) on the side surface of the rail head.
- the present invention is not limited by the following examples, and can be appropriately modified within a range that can be adapted to the gist of the present invention, all of which are included in the technical scope of the present invention. Will be.
- the steel material having the composition shown in Table 1 was hot-rolled under the conditions shown in Table 2 and accelerated cooling after the hot-rolling to produce a rail material. Accelerated cooling was performed only on the rail head, and after cooling was stopped, it was allowed to cool.
- the rolling finish temperature in Table 2 is a value obtained by measuring the temperature of the surface of the side surface of the rail head on the entry side of the final rolling mill with a radiation thermometer as the rolling finish temperature.
- the cooling stop temperature in Table 2 the value measured by the radiation thermometer for the temperature of the surface layer on the side surface of the rail head when the cooling of the secondary cooling is stopped is shown as the cooling stop temperature.
- the cooling rate was defined as the cooling rate (° C./s) by converting the temperature change from the start of cooling to the stop of cooling per unit time (seconds) for the primary cooling and the secondary cooling.
- the obtained rails were evaluated for the old austenite particle size RA , fatigue crack propagation characteristics, and fatigue damage resistance. Each evaluation content will be described in detail below.
- ⁇ Old austenite particle size RA > After cutting the tip of the rail after hot finish rolling, the cut material was immediately water-cooled. With respect to the obtained water-cooled material, a test piece for microstructure observation was taken from the rolling longitudinal direction at a depth of 5 mm from the surface of the rail head 1 shown in FIG. The obtained test piece was subjected to ⁇ -grain etching after mirror polishing, and a cross-sectional observation of 200 times was performed using an optical microscope.
- the old austenite particle size RA was evaluated by measuring the particle size of 400 or more by tracing work using image analysis software and calculating the average value.
- FIG. 4A and 4B are schematic views showing an example of a test piece, FIG. 4A shows a front view, FIG. 4B shows a side view, and FIG. 4C shows an enlarged front view of a notch portion.
- the crack propagation characteristics were evaluated. When the value of da / dN was 8.0 ⁇ 10-8 or less, it was evaluated as having the fatigue crack propagation suppressing performance.
- ⁇ Fatigue damage resistance> Regarding fatigue damage resistance, it is most desirable to actually lay the rail and evaluate it, but it takes a long time to test. Therefore, we used a Nishihara-type wear tester that can evaluate fatigue resistance in a short time.
- a round bar having a diameter of 32 mm was taken from the head of an ordinary rail described in JIS standard E1101: 2012. Then, the round bar was heat-treated so that the Vickers hardness (load 98N) was Hv390 and the structure became a tempered martensite structure, and then the round bar was processed into a cylinder having a diameter of 30 mm and used for the test. As shown in FIG. 6, the Nishihara-type wear test piece 17 was collected from the fatigue-resistant damage test piece collecting section 14 on the surface layer of the rail head 1. The arrows in FIG. 5A indicate the rotation directions of the Nishihara-type wear test piece 17 and the wheel test piece 18, respectively.
- the test environment is oil lubrication conditions, contact pressure: 1.8 GPa, slip rate: -20%, rotation speed: 600 rpm (wheel test piece is 750 rpm), and observe the surface of the test piece every 2.5 x 10 4 times.
- the number of revolutions at the time when a crack of 0.5 mm or more was generated was defined as the fatigue damage life. If this value is 8 ⁇ 10 5 times or more, it is determined that there is fatigue damage resistance.
- Table 2 also shows the results of the above survey.
- Test results of rail materials produced by the manufacturing method heatating temperature, rolling finish temperature
- compatible steel satisfying the composition of the present invention and CP of 2500 or less (Test No. 1 to No. 1 in Table 2).
- the fatigue crack propagation rate of 20, ) Satisfied with the fatigue crack propagation rate da / dN (m / cycle) of 8.0 ⁇ 10-8 or less at ⁇ K 20 MPa ⁇ m 1/2.
- the test No. 1 in which the primary cooling and secondary cooling conditions are in a suitable range.
- the fatigue crack propagation speed da / dN (m / cycle) was 8.0 ⁇ 10-8 or less, and the fatigue damage life was 8 ⁇ 10 5 times or more.
- CP was used in the comparative example (test Nos. 21 to 28 and 30 in Table 2) in which the component composition of the rail material did not satisfy the conditions of the present invention or was not applied to the production method within the scope of the present invention. It exceeded 2500 and the fatigue crack propagation velocity da / dN (m / cycle) exceeded 8.0 ⁇ 10-8 , or the fatigue damage life was less than 8 ⁇ 10 5 times.
- the heating temperature was too high, so that a part of the steel material melted during heating. For this reason, it was not possible to perform rolling because there was a concern about breakage during rolling, and it was not possible to evaluate the characteristics.
- the rail and the manufacturing method thereof according to the present invention it is possible to stably manufacture a fatigue-resistant damage-resistant rail having excellent fatigue-resistant crack propagation characteristics, and it is possible to extend the life of rails for high-axis heavy railways and railways. It contributes to accident prevention and has an industrially beneficial effect.
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Abstract
Description
特許文献1~4に記載の技術のように、単にC含有量を0.85質量%超え1.20質量%以下にすると、熱処理条件によっては初析セメンタイト組織が生成し、また脆いパーライト層状組織のセメンタイト層の量が増加するため、耐疲労損傷性の向上は見込めない。また、特許文献5に記載の技術では、Alの添加により疲労損傷の起点となる酸化物が生成するため、特に疲労き裂の発生を抑制することが困難であった。さらに、特許文献6に記載の技術では、成分と製造条件の組み合わせによっては初析セメンタイト組織が生成する場合があり、結果として疲労き裂伝播速度が増加してしまうため、材質制御が十分であるとは言い難い。 However, the above-mentioned conventional technique still has the following problems to be solved.
When the C content is simply more than 0.85% by mass and 1.20% by mass or less as in the techniques described in
CP=X/RA ・・・(1)
X={(10×[%C])+([%Si]/12)+([%Mn]/24)+([%Cr]/21)}5 ・・・(2) The rails having excellent fatigue crack propagation characteristics according to the present invention developed to solve the above problems and realize the above objects have C: 0.80 to 1.30% by mass and Si: 0.10 to 1. Contains 20% by mass, Mn: 0.20 to 1.80% by mass, P: 0.035% by mass or less, S: 0.0005 to 0.012% by mass, Cr: 0.20 to 2.50% by mass. However, the balance has a component composition consisting of Fe and unavoidable impurities, and the CP represented by the following formula (1) is 2500 or less, where [% Y] is the content (mass%) of the element Y. ), And RA is characterized by having an old austenite particle size (μm).
CP = X / RA ... (1)
X = {(10 × [% C]) + ([% Si] / 12) + ([% Mn] / 24) + ([% Cr] / 21)} 5 ... (2)
a.前記成分組成が、さらに、V:0.30質量%以下、Cu:1.0質量%以下、Ni:1.0質量%以下、Nb:0.05質量%以下およびMo:2.0質量%以下から選ばれる少なくとも1種を含有すること、
b.前記成分組成が、さらに、Al:0.07質量%以下、W:1.0質量%以下、B:0.005質量%以下、Ti:0.05質量%以下およびSb:0.05質量%以下から選ばれる少なくとも1種を含有すること、
などがより好ましい解決手段になり得るものと考えられる。 Regarding the rail having excellent fatigue crack propagation characteristics according to the present invention,
a. Further, the component composition is V: 0.30% by mass or less, Cu: 1.0% by mass or less, Ni: 1.0% by mass or less, Nb: 0.05% by mass or less, and Mo: 2.0% by mass. Containing at least one selected from the following,
b. The component composition further includes Al: 0.07% by mass or less, W: 1.0% by mass or less, B: 0.005% by mass or less, Ti: 0.05% by mass or less, and Sb: 0.05% by mass. Containing at least one selected from the following,
Etc. may be a more preferable solution.
加えて、熱間圧延後の熱処理条件を適正化することで対疲労損傷性を向上させることができるので好ましい。 According to the rail and the manufacturing method thereof according to the present invention, it is possible to stably manufacture a fatigue-resistant damage-resistant rail having excellent fatigue-resistant crack propagation characteristics, and it is possible to extend the life of rails for high-axis heavy railways and railways. It contributes to accident prevention and has an industrially beneficial effect.
In addition, it is preferable to optimize the heat treatment conditions after hot rolling because the fatigue damage resistance can be improved.
Cはパーライト組織の強度すなわち耐疲労損傷性を確保するための必須元素である。しかし、0.80%未満では優れた耐疲労き裂伝播特性を得ることが難しい。また、1.30%を超えると、熱間圧延後の冷却中に多量の初析セメンタイトがオーステナイト粒界に生成し、疲労き裂伝播速度の増加を招く。なお、初析セメンタイトは1.30%以下の場合にも存在するが、後述の関係式に基づき、旧オーステナイト粒径を制御することで、その影響を回避することができる。したがって、C含有量は0.80~1.30%の範囲とする。なお、C含有量の上限は1.00%が好ましく、0.90%がさらに好ましい。 C: 0.80 to 1.30%
C is an essential element for ensuring the strength of the pearlite structure, that is, the fatigue damage resistance. However, if it is less than 0.80%, it is difficult to obtain excellent fatigue-resistant crack propagation characteristics. On the other hand, if it exceeds 1.30%, a large amount of proeutectoid cementite is generated at the austenite grain boundaries during cooling after hot rolling, which causes an increase in the fatigue crack propagation rate. Although the proeutectoid cementite is present even when it is 1.30% or less, its influence can be avoided by controlling the old austenite particle size based on the relational expression described later. Therefore, the C content is in the range of 0.80 to 1.30%. The upper limit of the C content is preferably 1.00%, more preferably 0.90%.
Siは、脱酸剤としての効果に加え、パーライト平衡変態温度を上昇させ、ラメラー間隔を細かくすることにより、疲労き裂伝播速度の低下に寄与する。そのため0.10%以上必要であるが、1.20%を超えるとSiの有する高い酸素との結合力のため、溶接性が劣化する。さらに、Siは、共析点を低C側へ移動させる作用を有するため、過度の添加は初析セメンタイトの生成を助長し、疲労き裂伝播速度の増加を招く。したがって、Si含有量は0.10~1.20%の範囲とする。なお、Si含有量の下限は0.20%が好ましく、Si含有量の上限は0.80%が好ましく、0.60%がさらに好ましい。 Si: 0.10 to 1.20%
In addition to its effect as a deoxidizing agent, Si contributes to a decrease in the fatigue crack propagation rate by increasing the pearlite equilibrium transformation temperature and making the lamellar interval finer. Therefore, 0.10% or more is required, but if it exceeds 1.20%, the weldability deteriorates due to the high bonding force of Si with oxygen. Further, since Si has an action of moving the eutectic point to the low C side, excessive addition promotes the formation of eutectic cementite and causes an increase in the fatigue crack propagation rate. Therefore, the Si content is in the range of 0.10 to 1.20%. The lower limit of the Si content is preferably 0.20%, the upper limit of the Si content is preferably 0.80%, and even more preferably 0.60%.
Mnは、パーライト変態温度を低下させてラメラー間隔を細かくすることにより、疲労き裂伝播速度の低下に寄与する。しかしながら、Mn含有量が0.20%未満では、十分な効果が得られない。一方、Mn含有量が1.80%を超えるとマルテンサイト組織を生じ易く、レールの熱処理時および溶接時に硬化や脆化を生じ材質が劣化し易い。さらに、Mnは、共析点を低C側へ移動させる作用を有するため、過度の添加は初析セメンタイトの生成を助長し、疲労き裂伝播速度の増加を招く。したがって、Mn含有量は0.20~1.80%の範囲とする。なお、Mn含有量の下限は0.30%が好ましく、Mn含有量の上限は1.00%が好ましく、0.60%がさらに好ましい。 Mn: 0.20 to 1.80%
Mn contributes to a decrease in the fatigue crack propagation rate by lowering the pearlite transformation temperature and making the lamellar interval finer. However, if the Mn content is less than 0.20%, a sufficient effect cannot be obtained. On the other hand, when the Mn content exceeds 1.80%, a martensite structure is likely to be formed, and the material is likely to be deteriorated due to hardening or embrittlement during heat treatment and welding of the rail. Further, since Mn has an action of moving the eutectic point to the low C side, excessive addition promotes the formation of eutectic cementite and causes an increase in the fatigue crack propagation rate. Therefore, the Mn content is in the range of 0.20 to 1.80%. The lower limit of the Mn content is preferably 0.30%, the upper limit of the Mn content is preferably 1.00%, and even more preferably 0.60%.
0.035%を超えるPの含有は延性を劣化する。したがって、P含有量は0.035%以下とする。好ましくは0.020%以下である。一方、P含有量の下限は特に限定されず0%であってもよいが、工業的には0%超となるのが通例である。なお、P含有量を過度に低下させることは、精錬コストの増加を招くため、経済性の観点からは、P含有量を0.001%以上とすることが好ましい。 P: 0.035% or less The content of P exceeding 0.035% deteriorates ductility. Therefore, the P content is 0.035% or less. It is preferably 0.020% or less. On the other hand, the lower limit of the P content is not particularly limited and may be 0%, but industrially, it is usually more than 0%. It should be noted that excessively reducing the P content leads to an increase in refining cost, and therefore, from the viewpoint of economic efficiency, it is preferable to set the P content to 0.001% or more.
Sは、主にA系介在物の形態(加工によって粘性変形をうけるもの)で鋼中に存在するが、その含有量が0.012%を超えるとこの介在物量が著しく増加し、同時に粗大な介在物を生成するため、鋼材の清浄性が悪化する。また、S含有量を0.0005%未満にすると、精錬コストの増加を招く。したがって、S含有量は0.0005~0.012%の範囲とする。なお、S含有量の上限は0.010%が好ましく、0.008%がさらに好ましい。 S: 0.0005 to 0.012%
S is mainly present in steel in the form of A-based inclusions (those that undergo viscous deformation due to processing), but when the content exceeds 0.012%, the amount of these inclusions increases remarkably, and at the same time, it is coarse. Since inclusions are generated, the cleanliness of the steel material deteriorates. Further, if the S content is less than 0.0005%, the refining cost will increase. Therefore, the S content is in the range of 0.0005 to 0.012%. The upper limit of the S content is preferably 0.010%, more preferably 0.008%.
Crは、パーライト平衡変態温度を上昇させ、ラメラー間隔を細かくすることにより、疲労き裂伝播速度の低下に寄与する。しかし、Cr含有量が0.20%未満では、疲労き裂進展を十分に抑制することができず、一方、Cr含有量が2.50%を超えると鋼の焼入れ性が高くなり、マルテンサイトが生成し易くなる。また、マルテンサイトが生成しない条件で製造した場合、旧オーステナイト粒界に初析セメンタイトが生成する。そのため、疲労き裂伝播速度が増加する。したがって、Cr含有量は0.20~2.50%の範囲とする。なお、Cr含有量の下限は0.40%が好ましく、0.50%がさらに好ましく、Cr含有量の上限は1.50%が好ましく、1.00%がさらに好ましい。 Cr: 0.20 to 2.50%
Cr contributes to a decrease in the fatigue crack propagation rate by increasing the pearlite equilibrium transformation temperature and making the lamellar spacing finer. However, if the Cr content is less than 0.20%, fatigue crack growth cannot be sufficiently suppressed, while if the Cr content exceeds 2.50%, the hardenability of steel becomes high and martensite. Is easy to generate. Further, when manufactured under the condition that martensite is not formed, proeutectoid cementite is formed at the old austenite grain boundaries. Therefore, the fatigue crack propagation rate increases. Therefore, the Cr content is in the range of 0.20 to 2.50%. The lower limit of the Cr content is preferably 0.40%, more preferably 0.50%, and the upper limit of the Cr content is preferably 1.50%, further preferably 1.00%.
CP=X/RA ・・・(1)
X={(10×[%C])+([%Si]/12)+([%Mn]/24)+([%Cr]/21)}5 ・・・(2)
ただし、[%Y]:元素Yの含有量(質量%)、
RA :旧オーステナイト粒径(μm)
を表す。 Furthermore, in the present invention, it is not sufficient for each element to simply satisfy the above range, and it is derived from the component parameter X corresponding to the amount of proeutectoid cementite represented by the following equation (2) and the former austenite particle size RA. It is important to control the CP value represented by the following equation (1) to 2500 or less.
CP = X / RA ... (1)
X = {(10 × [% C]) + ([% Si] / 12) + ([% Mn] / 24) + ([% Cr] / 21)} 5 ... (2)
However, [% Y]: content of element Y (mass%),
RA : Old austenite particle size (μm)
Represents.
A群:V:0.30%以下、Cu:1.0%以下、Ni:1.0%以下、Nb:0.05%以下およびMo:2.0%以下
B群:Al:0.07%以下、W:1.0%以下、B:0.005%以下、Ti:0.05%以下およびSb:0.05%以下 In addition to the components described above, the component composition of the rail used in the present invention may be any one or both of at least one selected from the following group A and at least one selected from group B below. It may be contained in.
Group A: V: 0.30% or less, Cu: 1.0% or less, Ni: 1.0% or less, Nb: 0.05% or less and Mo: 2.0% or less Group B: Al: 0.07 % Or less, W: 1.0% or less, B: 0.005% or less, Ti: 0.05% or less and Sb: 0.05% or less
V:0.30%以下
Vは、鋼中で炭窒化物を形成して基地中へ分散析出し、鋼の耐摩耗性を向上させる。しかし、その含有量が、0.30%を超えると、加工性が劣化し、製造コストが増加する。また、V含有量が0.30%を超えると、合金コストが増加するため、内部高硬度型レールのコストが増加する。したがって、Vは、0.30%を上限として含有することが好ましい。なお、上記の耐摩耗性を向上させる効果を発現させるためには、Vは0.001%以上で含有されることが好ましい。なお、V含有量の上限は0.15%がより好ましい。 Hereinafter, the reason for specifying the content of the elements belonging to the above groups A and B will be described.
V: 0.30% or less V forms a carbonitride in the steel and disperses and precipitates in the substrate, improving the wear resistance of the steel. However, if the content exceeds 0.30%, the processability deteriorates and the manufacturing cost increases. Further, when the V content exceeds 0.30%, the alloy cost increases, so that the cost of the internal high hardness type rail increases. Therefore, V is preferably contained up to 0.30%. In addition, in order to exhibit the above-mentioned effect of improving wear resistance, V is preferably contained in an amount of 0.001% or more. The upper limit of the V content is more preferably 0.15%.
Cuは、Crと同様に固溶強化により鋼の更なる高強度化を図ることができる元素である。ただし、その含有量が1.0%を超えるとCu割れが生じ易くなる。したがって、成分組成にCuを含有する場合は、Cu含有量は1.0%以下とすることが好ましい。なお、Cu含有量の下限は0.005%がより好ましく、Cu含有量の上限は0.5%がより好ましい。 Cu: 1.0% or less Cu is an element that can further increase the strength of steel by solid solution strengthening like Cr. However, if the content exceeds 1.0%, Cu cracking is likely to occur. Therefore, when Cu is contained in the component composition, the Cu content is preferably 1.0% or less. The lower limit of the Cu content is more preferably 0.005%, and the upper limit of the Cu content is more preferably 0.5%.
Niは、延性を劣化することなく鋼の高強度化を図ることができる元素である。また、Cuと複合添加することによりCu割れを抑制することができるため、成分組成にCuを含有する場合にはNiも含有することが望ましい。ただし、Ni含有量が1.0%を超えると、鋼の焼入れ性がより上昇し、マルテンサイトやベイナイトの生成量が多くなり、耐摩耗性と耐疲労損傷性が低下しがちとなる。したがって、Niを含有する場合は、Ni含有量は1.0%以下とすることが好ましい。なお、Ni含有量の下限は0.005%がより好ましく、Ni含有量の上限は0.5%がより好ましい。 Ni: 1.0% or less Ni is an element that can increase the strength of steel without deteriorating ductility. Further, since Cu cracking can be suppressed by compound addition with Cu, it is desirable that Ni is also contained when Cu is contained in the component composition. However, when the Ni content exceeds 1.0%, the hardenability of the steel is further increased, the amount of martensite and bainite produced is increased, and the wear resistance and the fatigue damage resistance tend to be lowered. Therefore, when Ni is contained, the Ni content is preferably 1.0% or less. The lower limit of the Ni content is more preferably 0.005%, and the upper limit of the Ni content is more preferably 0.5%.
Nbは、レールを成形するための熱間圧延中および熱間圧延後に、鋼中のCと結び付いて炭化物として析出し、パーライトコロニーサイズの微細化に有効に作用する。その結果、耐摩耗性や耐疲労損傷性、延性を大きく向上させ、内部高硬度型レールの長寿命化に大きく寄与する。ただし、Nb含有量が0.05%を超えても、耐摩耗性や耐疲労損傷性の向上効果が飽和し、含有量上昇に見合う効果が得られない。したがって、Nbは、その含有量の上限を0.05%として含有されていてもよい。なお、Nb含有量が0.001%未満では、上記のレールの長寿命化に対して十分な効果が得られにくい。したがって、Nbを含有する場合は、Nb含有量は0.001%以上であることが好ましい。なお、Nb含有量の上限は0.03%がより好ましい。 Nb: 0.05% or less Nb is combined with C in steel and precipitated as carbide during hot rolling for forming a rail and after hot rolling, and effectively acts on the miniaturization of pearlite colony size. As a result, wear resistance, fatigue damage resistance, and ductility are greatly improved, which greatly contributes to extending the life of the internal high hardness type rail. However, even if the Nb content exceeds 0.05%, the effect of improving wear resistance and fatigue damage resistance is saturated, and an effect commensurate with the increase in content cannot be obtained. Therefore, Nb may be contained with the upper limit of its content being 0.05%. If the Nb content is less than 0.001%, it is difficult to obtain a sufficient effect on extending the life of the rail. Therefore, when Nb is contained, the Nb content is preferably 0.001% or more. The upper limit of the Nb content is more preferably 0.03%.
Moは、固溶強化によりさらなる鋼の高強度化を図ることができる元素である。また、Moは、共析点を高C側へ移動させる作用を有するため、初析セメンタイトの生成を抑制する作用も有する。ただし、2.0%を超えると、鋼中に生ずるベイナイト量が多くなり、耐摩耗性が低下する。したがって、レールの成分組成がMoを含有する場合は、Mo含有量は2.0%以下とすることが好ましい。なお、Mo含有量の下限は0.005%がより好ましく、Mo含有量の上限は1.0%がより好ましい。 Mo: 2.0% or less Mo is an element that can further increase the strength of steel by solid solution strengthening. Further, since Mo has an action of moving the eutectic point to the high C side, it also has an action of suppressing the formation of eutectic cementite. However, if it exceeds 2.0%, the amount of bainite generated in the steel increases and the wear resistance deteriorates. Therefore, when the component composition of the rail contains Mo, the Mo content is preferably 2.0% or less. The lower limit of the Mo content is more preferably 0.005%, and the upper limit of the Mo content is more preferably 1.0%.
Alは、脱酸剤として添加することができる元素である。しかし、Al含有量が0.07%を超えると、Alの有する高い酸素との結合力のため、鋼中に酸化物系介在物が多量に生成し、その結果、鋼の延性が低下する。そのため、Al含有量は0.07%以下とすることが好ましい。一方、Al含有量の下限は特に限定されないが、脱酸のためには0.001%以上とすることが好ましい。なお、Al含有量の上限は0.03%がより好ましい。 Al: 0.07% or less Al is an element that can be added as a deoxidizing agent. However, when the Al content exceeds 0.07%, a large amount of oxide-based inclusions are generated in the steel due to the high binding force of Al with oxygen, and as a result, the ductility of the steel is lowered. Therefore, the Al content is preferably 0.07% or less. On the other hand, the lower limit of the Al content is not particularly limited, but is preferably 0.001% or more for deoxidation. The upper limit of the Al content is more preferably 0.03%.
Wは、レール形状への成形を行う熱間圧延中および熱間圧延後に炭化物として析出し、析出強化によりレールの強度や延性を向上させる。しかし、W含有量が1.0%を超えると鋼中にマルテンサイトが生成し、その結果、延性が低下する。そのため、Wを添加する場合、W含有量を1.0%以下とすることが好ましい。一方、W含有量の下限は特に限定されないが、上記の強度や延性を向上させる作用を発現させるためには0.001%以上とすることが好ましい。なお、W含有量の下限は0.005%がより好ましく、W含有量の上限は0.5%がより好ましい。 W: 1.0% or less W is precipitated as carbide during and after hot rolling for forming into a rail shape, and the strength and ductility of the rail are improved by strengthening the precipitation. However, when the W content exceeds 1.0%, martensite is formed in the steel, and as a result, the ductility is lowered. Therefore, when W is added, the W content is preferably 1.0% or less. On the other hand, the lower limit of the W content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the above-mentioned action of improving strength and ductility. The lower limit of the W content is more preferably 0.005%, and the upper limit of the W content is more preferably 0.5%.
Bは、レール形状への成形を行う熱間圧延中および熱間圧延後に、鋼中で窒化物として析出し、析出強化により鋼の強度や延性を向上させる。しかし、B含有量が0.005%を超えるとマルテンサイトが生成し、その結果、鋼の延性が低下する。そのため、Bを含有する場合、B含有量を0.005%以下とすることが好ましい。一方、B含有量の下限は特に限定されないが、上記の強度や延性を向上させる作用を発現させるためには0.001%以上とすることが好ましい。なお、B含有量の上限は0.003%がより好ましい。 B: 0.005% or less B is precipitated as nitride in steel during and after hot rolling for forming into a rail shape, and the strength and ductility of the steel are improved by precipitation strengthening. However, if the B content exceeds 0.005%, martensite is formed, and as a result, the ductility of the steel is lowered. Therefore, when B is contained, the B content is preferably 0.005% or less. On the other hand, the lower limit of the B content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the above-mentioned action of improving strength and ductility. The upper limit of the B content is more preferably 0.003%.
Tiは、レール形状への成形を行う熱間圧延中および熱間圧延後に炭化物、窒化物あるいは炭窒化物として鋼中で析出し、析出強化により鋼の強度や延性を向上させる。しかし、Ti含有量が0.05%を超えると粗大な炭化物、窒化物あるいは炭窒化物が生成し、その結果、鋼の延性が低下する。そのため、Tiを含有する場合、Ti含有量を0.05%以下とすることが好ましい。一方、Ti含有量の下限は特に限定されないが、上記の強度や延性を向上させる作用を発現させるためには0.001%以上とすることが好ましい。なお、Ti含有量の下限は0.005%がより好ましく、Ti含有量の上限は0.03%がより好ましい。 Ti: 0.05% or less Ti precipitates in steel as carbides, nitrides or carbonitrides during and after hot rolling to form a rail shape, and the strength and ductility of the steel are enhanced by precipitation strengthening. Improve. However, if the Ti content exceeds 0.05%, coarse carbides, nitrides or carbonitrides are formed, resulting in a decrease in steel ductility. Therefore, when Ti is contained, the Ti content is preferably 0.05% or less. On the other hand, the lower limit of the Ti content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the above-mentioned action of improving strength and ductility. The lower limit of the Ti content is more preferably 0.005%, and the upper limit of the Ti content is more preferably 0.03%.
Sbは、熱間圧延前にレール鋼素材を加熱炉で再加熱する際に、その再加熱中の鋼の脱炭を防止するという顕著な効果を有する。しかし、Sb含有量が0.05%を超えると、鋼の延性および靭性に悪影響を及ぼすため、Sbを含有する場合、Sb含有量を0.05%以下とすることが好ましい。一方、Sb含有量の下限は特に限定されないが、脱炭層を軽減する効果を発現させるためには0.001%以上とすることが好ましい。なお、Sb含有量の下限は0.005%がより好ましく、Sb含有量の上限は0.03%がより好ましい。 Sb: 0.05% or less Sb has a remarkable effect of preventing decarburization of the steel during the reheating when the rail steel material is reheated in a heating furnace before hot rolling. However, if the Sb content exceeds 0.05%, the ductility and toughness of the steel are adversely affected. Therefore, when the Sb is contained, the Sb content is preferably 0.05% or less. On the other hand, the lower limit of the Sb content is not particularly limited, but it is preferably 0.001% or more in order to exhibit the effect of reducing the decarburized layer. The lower limit of the Sb content is more preferably 0.005%, and the upper limit of the Sb content is more preferably 0.03%.
(1)熱間圧延
(2)一次冷却
(3)二次冷却
レール素材として用いる鋼素材は任意の方法で製造できるが、一般的には、鋳造、特に連続鋳造により前記鋼素材を製造することが好ましい。 Next, the rail manufacturing method according to the present invention described above will be described. The rail of the present invention can be manufactured by sequentially applying the following treatments (1) to (3) to a steel material having the above-mentioned composition.
(1) Hot rolling (2) Primary cooling (3) Secondary cooling The steel material used as the rail material can be manufactured by any method, but in general, the steel material is manufactured by casting, especially continuous casting. Is preferable.
まず、前記鋼素材を熱間圧延してレール形状とする。本発明では、前記熱間圧延における圧延仕上げ温度を制御することにより最終的に得られるレールの旧オーステナイト粒径をコントロールできるため、前記熱間圧延の方法は特に限定されず、任意の方法で行うことができる。
加熱温度:1350℃以下
熱間圧延に先立って施す鋼素材の加熱において、加熱温度は1350℃以下とする必要がある。加熱温度が上限超えでは、過度の昇温によって鋼素材が部分的に溶融し、レール内部に欠陥が発生するおそれがある。一方、加熱温度の下限については特に制限は無いが、圧延時の変形抵抗を低減するため、1150℃以上とすることが好ましい。 (1) Hot rolling First, the steel material is hot-rolled to form a rail shape. In the present invention, since the old austenite grain size of the rail finally obtained can be controlled by controlling the rolling finish temperature in the hot rolling, the hot rolling method is not particularly limited and is performed by any method. be able to.
Heating temperature: 1350 ° C. or lower In heating the steel material to be applied prior to hot rolling, the heating temperature must be 1350 ° C. or lower. If the heating temperature exceeds the upper limit, the steel material may be partially melted due to excessive temperature rise, and defects may occur inside the rail. On the other hand, the lower limit of the heating temperature is not particularly limited, but is preferably 1150 ° C. or higher in order to reduce the deformation resistance during rolling.
上記熱間圧延における圧延仕上げ温度が900℃より低い場合、オーステナイト低温域にて圧延が行われることになり、オーステナイト結晶粒に加工歪が導入されるだけでなく、オーステナイト結晶粒の伸長が顕著となる。オーステナイト粒界面積の増加により初析セメンタイトの核生成サイトが増加し、その結果、耐疲労き裂伝播特性が低下する。そのため、圧延仕上げ温度は900℃以上とする。一方、圧延仕上げ温度の上限については特に制限は無いが、旧オーステナイト粒径が極端に粗大化すると、延性や靭性が低下してしまうため、1050℃以下にすることが好ましい。なお、ここでいう圧延仕上げ温度は、最終圧延ミル入側におけるレール頭部側面の温度であり、放射温度計で測定可能である。 Rolling finish temperature: 900 ° C or higher When the rolling finish temperature in the above hot rolling is lower than 900 ° C, rolling is performed in the austenite low temperature range, and not only processing strain is introduced into the austenite crystal grains but also austenite is introduced. The elongation of the crystal grains becomes remarkable. Increasing the austenite grain boundary area increases the nucleation sites of proeutectoid cementite, resulting in a decrease in fatigue-resistant crack propagation characteristics. Therefore, the rolling finish temperature is set to 900 ° C. or higher. On the other hand, the upper limit of the rolling finish temperature is not particularly limited, but if the old austenite particle size becomes extremely coarse, the ductility and toughness will decrease, so the temperature is preferably 1050 ° C. or lower. The rolling finish temperature referred to here is the temperature of the side surface of the rail head on the entry side of the final rolling mill, and can be measured by a radiation thermometer.
900℃から750℃までの平均冷却速度:0.4~3℃/s
次に、加速冷却を行う。その際、一次冷却として、初析セメンタイトの生成温度域である900℃から750℃における平均冷却速度が0.4℃/s未満であると、初析セメンタイト量が増加する。そのため、初析セメンタイト組織に割れが発生しやすくなり、レールの耐疲労損傷性が低下するおそれがある。したがって、前記一次冷却の平均冷却速度の下限は0.4℃/sとすることが好ましく、0.7℃/sがより好ましい。一方、前記一次冷却の平均冷却速度が3℃/sを超える場合は、マルテンサイト組織が生成し、延性や耐疲労損傷性が低下するおそれがある。そのため、前記一次冷却の平均冷却速度の上限は3℃/sとすることが好ましく、2℃/sがより好ましい。 (2) Primary cooling Average cooling rate from 900 ° C to 750 ° C: 0.4 to 3 ° C / s
Next, accelerated cooling is performed. At that time, as the primary cooling, if the average cooling rate in the temperature range of 900 ° C. to 750 ° C., which is the temperature range for producing the proeutectoid cementite, is less than 0.4 ° C./s, the amount of the proeutectoid cementite increases. Therefore, cracks are likely to occur in the proactive cementite structure, which may reduce the fatigue damage resistance of the rail. Therefore, the lower limit of the average cooling rate of the primary cooling is preferably 0.4 ° C./s, more preferably 0.7 ° C./s. On the other hand, when the average cooling rate of the primary cooling exceeds 3 ° C./s, a martensite structure may be formed, and ductility and fatigue damage resistance may decrease. Therefore, the upper limit of the average cooling rate of the primary cooling is preferably 3 ° C / s, more preferably 2 ° C / s.
750℃から400~600℃の温度域までの平均冷却速度:1~10℃/s
上記一次冷却の停止後、二次冷却を行う。二次冷却開始温度である750℃から400~600℃の温度域にある二次冷却の冷却停止温度までの平均冷却速度が1℃/s未満であると、パーライト組織のラメラー間隔が粗くなる。そのため、パーライト組織の硬度が低下して、レールの耐疲労損傷性が低下するおそれがある。加えて、低温域での冷却時間が増大するため生産性が低下し、レールの製造コストが増加するおそれがある。一方、前記二次冷却の平均冷却速度が10℃/sを超える場合は、マルテンサイト組織が生成し、延性や耐疲労損傷性が低下するおそれがある。そのため、前記二次冷却の平均冷却速度は1~10℃/sの範囲とすることが好ましい。なお、前記二次冷却の平均冷却速度の上限は、5℃/sがより好ましい。 (3) Secondary cooling Average cooling rate from 750 ° C to 400 to 600 ° C: 1 to 10 ° C / s
After the primary cooling is stopped, the secondary cooling is performed. When the average cooling rate from the secondary cooling start temperature of 750 ° C. to the cooling stop temperature of the secondary cooling in the temperature range of 400 to 600 ° C. is less than 1 ° C./s, the lamellar spacing of the pearlite structure becomes coarse. Therefore, the hardness of the pearlite structure may decrease, and the fatigue damage resistance of the rail may decrease. In addition, the increased cooling time in the low temperature region may reduce productivity and increase rail manufacturing costs. On the other hand, if the average cooling rate of the secondary cooling exceeds 10 ° C./s, a martensite structure may be formed, and ductility and fatigue damage resistance may decrease. Therefore, the average cooling rate of the secondary cooling is preferably in the range of 1 to 10 ° C./s. The upper limit of the average cooling rate of the secondary cooling is more preferably 5 ° C./s.
<旧オーステナイト粒径RA>
熱間仕上げ圧延後のレール先端部を切断後、該切断材に対して直ちに水冷処理を施した。得られた水冷材に対し、図2に示すレール頭部1の表面から5mm深さ位置の圧延長手方向より、組織観察用の試験片を採取した。得られた試験片に対し、鏡面研磨後γ粒エッチングを施し、光学顕微鏡を用いて200倍の断面観察を行った。旧オーステナイト粒径RAは画像解析ソフトを用いたトレース作業により400個以上の粒径を測定し、その平均値を求めることで評価した。 The obtained rails were evaluated for the old austenite particle size RA , fatigue crack propagation characteristics, and fatigue damage resistance. Each evaluation content will be described in detail below.
<Old austenite particle size RA >
After cutting the tip of the rail after hot finish rolling, the cut material was immediately water-cooled. With respect to the obtained water-cooled material, a test piece for microstructure observation was taken from the rolling longitudinal direction at a depth of 5 mm from the surface of the
図3に示すレール頭頂部とゲージコーナー(GC)部の2箇所から、疲労き裂伝播試験片を採取し、疲労き裂伝播試験を行った。図4は試験片の一例を示す模式図であり、図4(a)は正面図を、図4(b)は側面図を、図4(c)はノッチ部拡大正面図を示す。図4において、試験片は例えば幅W=20mm、高さH=100mm、厚さB=5mmの板状のものであって、高さHの中央H/2部分の一方の幅端にノッチ部が形成されている。ノッチ部の長さL=2mm、幅C=0.2mmであって、ノッチ部の端部は曲率R=0.1mmに形成されている。応力比(R比=最小応力/最大応力)は0.1とし、応力拡大係数ΔK=20MPa・m1/2における、疲労き裂伝播速度da/dN(m/cycle)を測定し、耐疲労亀裂伝播特性を評価した。da/dNの値が8.0×10-8以下であれば、疲労き裂伝播抑止性能があると評価した。 <Fatigue crack propagation characteristics>
Fatigue crack propagation test pieces were collected from two locations, the top of the rail and the gauge corner (GC) shown in FIG. 3, and the fatigue crack propagation test was performed. 4A and 4B are schematic views showing an example of a test piece, FIG. 4A shows a front view, FIG. 4B shows a side view, and FIG. 4C shows an enlarged front view of a notch portion. In FIG. 4, the test piece is, for example, a plate having a width W = 20 mm, a height H = 100 mm, and a thickness B = 5 mm, and has a notch at one width end of the central H / 2 portion of the height H. Is formed. The notch portion has a length L = 2 mm and a width C = 0.2 mm, and the end portion of the notch portion is formed with a curvature R = 0.1 mm. The stress ratio (R ratio = minimum stress / maximum stress) is 0.1, and the fatigue crack propagation velocity da / dN (m / cycle) at the stress intensity factor ΔK = 20 MPa · m 1/2 is measured to withstand fatigue. The crack propagation characteristics were evaluated. When the value of da / dN was 8.0 × 10-8 or less, it was evaluated as having the fatigue crack propagation suppressing performance.
耐疲労損傷性に関しては、レールを実際に敷設して評価するのが最も望ましいが、それでは試験に長時間を要する。そこで、短時間で耐疲労損傷性を評価することができる西原式摩耗試験機を用いた。ここでは、実際のレールと車輪の接触条件をシミュレートした比較試験により耐疲労損傷性を評価した。具体的には、接触面を曲率半径R=15mmの曲面としてレール頭部1から直径30mmの西原式摩耗試験片17を採取し、図5に示すように車輪試験片18と接触させて回転させて試験を行なった。車輪試験片18は、まず、JIS規格E1101:2012に記載の普通レールの頭部から直径32mmの丸棒を採取した。そして、その丸棒に、ビッカース硬さ(荷重98N)がHv390であり、組織が焼戻しマルテンサイト組織となるように熱処理を行った後、直径30mmの円柱状に加工し試験に供した。なお、西原式摩耗試験片17は図6に示すようにレール頭部1の表層の耐疲労損傷試験片採取部14から採取した。図5(a)中の矢印は、それぞれ西原式摩耗試験片17と車輪試験片18の回転方向を示す。試験環境は油潤滑条件とし、接触圧力:1.8GPa、滑り率:-20%、回転速度:600rpm(車輪試験片は750rpm)で、2.5×104回毎に試験片表面を観察し、0.5mm以上の亀裂が発生した時点での回転数をもって、疲労損傷寿命とした。この数値が8×105回以上であれば耐疲労損傷性があると判定した。 <Fatigue damage resistance>
Regarding fatigue damage resistance, it is most desirable to actually lay the rail and evaluate it, but it takes a long time to test. Therefore, we used a Nishihara-type wear tester that can evaluate fatigue resistance in a short time. Here, the fatigue damage resistance was evaluated by a comparative test simulating the actual contact conditions between the rail and the wheel. Specifically, the Nishihara-type
11 旧オーステナイト粒径観察用試験片採取部
12 ゲージコーナー(GC)部
13 頭頂部
14 耐疲労損傷試験片採取部
15 疲労き裂伝播試験片
16 ノッチ部
17 西原式摩耗試験片
18 タイヤ試験片
21 旧オーステナイト粒
22 塑性域
23 疲労き裂
24 初析セメンタイト
25 へき開破壊
26 疲労き裂伝播速度増加
27 疲労き裂伝播速度低下
RA 旧オーステナイト粒径
RP 塑性域寸法 1
Claims (5)
- C:0.80~1.30質量%、Si:0.10~1.20質量%、Mn:0.20~1.80質量%、P:0.035質量%以下、S:0.0005~0.012質量%、Cr:0.20~2.50質量%を含有し、残部がFeおよび不可避的不純物からなる成分組成を有し、下記(1)式で表されるCPが2500以下であることを特徴とする耐疲労き裂伝播特性に優れるレール。
CP=X/RA ・・・(1)
X={(10×[%C])+([%Si]/12)+([%Mn]/24)+([%Cr]/21)}5 ・・・(2)
ただし、[%Y]:元素Yの含有量(質量%)、
RA :旧オーステナイト粒径(μm)
を表す。 C: 0.80 to 1.30% by mass, Si: 0.10 to 1.20% by mass, Mn: 0.20 to 1.80% by mass, P: 0.035% by mass or less, S: 0.0005 It contains ~ 0.012% by mass, Cr: 0.20 ~ 2.50% by mass, has a component composition in which the balance is composed of Fe and unavoidable impurities, and has a CP represented by the following formula (1) of 2500 or less. A rail with excellent fatigue crack propagation characteristics.
CP = X / RA ... (1)
X = {(10 × [% C]) + ([% Si] / 12) + ([% Mn] / 24) + ([% Cr] / 21)} 5 ... (2)
However, [% Y]: content of element Y (mass%),
RA : Old austenite particle size (μm)
Represents. - 前記成分組成が、さらに、V:0.30質量%以下、Cu:1.0質量%以下、Ni:1.0質量%以下、Nb:0.05質量%以下およびMo:2.0質量%以下から選ばれる少なくとも1種を含有することを特徴とする請求項1に記載の耐疲労き裂伝播特性に優れるレール。 Further, the component composition is V: 0.30% by mass or less, Cu: 1.0% by mass or less, Ni: 1.0% by mass or less, Nb: 0.05% by mass or less, and Mo: 2.0% by mass. The rail having excellent fatigue crack propagation characteristics according to claim 1, which contains at least one selected from the following.
- 前記成分組成が、さらに、Al:0.07質量%以下、W:1.0質量%以下、B:0.005質量%以下、Ti:0.05質量%以下およびSb:0.05質量%以下から選ばれる少なくとも1種を含有することを特徴とする請求項1または2に記載の耐疲労き裂伝播特性に優れるレール。 The component composition further includes Al: 0.07% by mass or less, W: 1.0% by mass or less, B: 0.005% by mass or less, Ti: 0.05% by mass or less, and Sb: 0.05% by mass. The rail having excellent fatigue crack propagation characteristics according to claim 1 or 2, which contains at least one selected from the following.
- 請求項1から3のいずれか1項に記載の成分組成を有する鋼素材に、1350℃以下の加熱を施した後、熱間圧延を施してレールを製造する方法であって、仕上げ温度が900℃以上となるように熱間圧延することを特徴とする耐疲労き裂伝播特性に優れるレールの製造方法。 A method for manufacturing a rail by heating a steel material having the component composition according to any one of claims 1 to 3 to 1350 ° C. or lower and then hot rolling to produce a rail, wherein the finishing temperature is 900. A method for manufacturing a rail having excellent fatigue-resistant crack propagation characteristics, which is characterized by hot rolling to a temperature of ℃ or higher.
- 前記熱間圧延後、900℃から750℃までを0.4~3℃/sの範囲の冷却速度で加速冷却し、750℃から400~600℃の冷却停止温度までを1~10℃/sの範囲の冷却速度で加速冷却することを特徴とする請求項4に記載の耐疲労き裂伝播特性に優れるレールの製造方法。 After the hot rolling, acceleration cooling is performed from 900 ° C. to 750 ° C. at a cooling rate in the range of 0.4 to 3 ° C./s, and cooling stop temperature from 750 ° C. to 400 to 600 ° C. is 1 to 10 ° C./s. The method for manufacturing a rail having excellent fatigue crack propagation characteristics according to claim 4, wherein the rail is accelerated and cooled at a cooling rate in the range of.
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CN202180044681.XA CN115917019A (en) | 2020-06-29 | 2021-06-01 | Rail having excellent fatigue crack propagation resistance and method for manufacturing same |
JP2021545917A JP7173366B2 (en) | 2020-06-29 | 2021-06-01 | RAIL EXCELLENT IN FATIGUE CRACK PROPAGATION RESISTANCE AND PRODUCTION METHOD THEREOF |
US18/008,203 US20230279517A1 (en) | 2020-06-29 | 2021-06-01 | Rail having excellent fatigue crack propagation resistance characteristics, and method of producing same |
CA3186612A CA3186612A1 (en) | 2020-06-29 | 2021-06-01 | Rail having excellent fatigue crack propagation resistance characteristics, and method for producing same |
BR112022025557A BR112022025557A2 (en) | 2020-06-29 | 2021-06-01 | RAIL THAT HAS EXCELLENT CHARACTERISTICS OF RESISTANCE TO THE PROPAGATION OF FATIGUE CRACKING AND MANUFACTURING METHOD |
KR1020227038956A KR20220160695A (en) | 2020-06-29 | 2021-06-01 | Rail with excellent fatigue crack propagation characteristics and its manufacturing method |
AU2021302317A AU2021302317B2 (en) | 2020-06-29 | 2021-06-01 | Rail having excellent fatigue crack propagation resistance characteristics, and method for producing same |
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JPH08109439A (en) | 1994-10-07 | 1996-04-30 | Nippon Steel Corp | Highly wear resistant rail with pearlitic metallic structure |
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WO2019189686A1 (en) * | 2018-03-30 | 2019-10-03 | Jfeスチール株式会社 | Rail and method for manufacturing same |
US20200017943A1 (en) * | 2018-07-10 | 2020-01-16 | Voestalpine Schienen Gmbh | Track part made of a hypereutectoid steel |
WO2020067520A1 (en) * | 2018-09-28 | 2020-04-02 | 日本製鉄株式会社 | Railway wheel |
-
2021
- 2021-06-01 JP JP2021545917A patent/JP7173366B2/en active Active
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- 2021-06-01 EP EP21834151.9A patent/EP4174191A1/en active Pending
- 2021-06-01 CN CN202180044681.XA patent/CN115917019A/en active Pending
- 2021-06-01 KR KR1020227038956A patent/KR20220160695A/en not_active Application Discontinuation
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JPH08109439A (en) | 1994-10-07 | 1996-04-30 | Nippon Steel Corp | Highly wear resistant rail with pearlitic metallic structure |
JPH08144016A (en) | 1994-11-15 | 1996-06-04 | Nippon Steel Corp | Highly wear resisting pearlitic rail |
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US20200017943A1 (en) * | 2018-07-10 | 2020-01-16 | Voestalpine Schienen Gmbh | Track part made of a hypereutectoid steel |
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JP7522984B1 (en) | 2023-03-24 | 2024-07-26 | Jfeスチール株式会社 | Rail and manufacturing method thereof |
JP7522985B1 (en) | 2023-03-24 | 2024-07-26 | Jfeスチール株式会社 | Rail and manufacturing method thereof |
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CN115917019A (en) | 2023-04-04 |
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AU2021302317A1 (en) | 2023-01-19 |
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