Technical field
[0001]
　The present invention relates to a wheel and, more particularly, to railway wheels for use in a railway vehicle.
BACKGROUND
[0002]
　The rail transport to higher efficiency, increased loading weight of the railcar, and, speed of railway vehicles has been underway. As a result, reduced and wear resistance of fatigue damage due to rolling contact with the rail have been studied.
[0003]
　Technique for increasing the wear resistance of railway wheels is proposed in JP-A-2012-107295 (Patent Document 1) and JP 2013-231212 (Patent Document 2).
[0004]
　Steel disclosed in Patent Document 1 wheel, in mass%, C: 0.65 ~ 0.84%, Si: 0.02 ~ 1.00%, Mn: 0.50 ~ 1.90%, Cr : 0.02 ~ 0.50%, V: 0.02 ~ 0.20%, and S: contains 0.04% or less, in Fn1 34 to 43 represented by the formula (1), and, Fn2 represented by the formula (2) is 25 or less, the balance being Fe and impurities. Here, equation (1) is a Fn1 = 2.7 + 29.5C + 2.9Si + 6.9Mn + 10.8Cr + 30.3Mo + 44.3V, equation (2) is, Fn2 = 0.76 × exp (0.05C) × exp ( 1.35Si) a × exp (0.38Mn) × exp (0.77Cr) × exp (3.0Mo) × exp (4.6V).
[0005]
　Wheels for railway vehicle disclosed in Patent Document 2, in mass%, C: 0.65 ~ 0.84%, Si: 0.4 ~ 1.0%, Mn: 0.50 ~ 1.40%, cr: 0.02 ~ 0.13%, S: 0.04% or less, and V: contains 0.02 to 0.12 percent, at Fn1 32 to 43 represented by the formula (1), and , Fn2 represented by the formula (2) is 25 or less, the balance being Fe and impurities. Here, equation (1) is a Fn1 = 2.7 + 29.5C + 2.9Si + 6.9Mn + 10.8Cr + 30.3Mo + 44.3V, equation (2) is, Fn2 = exp (0.76) × exp (0.05C) × is exp (1.35Si) × exp (0.38Mn) × exp (0.77Cr) × exp (3.0Mo) × exp (4.6V).
[0006]
　Patent Document 1 and Patent Document 2 described above, it is described that the wear resistance of railway wheels by satisfying the equation (1) is increased.
[0007]
　Incidentally, in rail transport, when the wheel mounted on the railway vehicle has been exposed to very severe corrosive environment, corrosion fatigue and it is expected that combined the corrosion fatigue may occur. The corrosion fatigue, a fatigue phenomenon that occurs by subjected to repeated stress in a corrosive environment. Specifically, when the plate portion of the railway wheels are exposed to a corrosive environment, corrosion pits are formed, it is expected that fatigue phenomena of the corrosion pits and starting points of cracking occurs. Accordingly, the wheel to be used in railway vehicle, corrosion fatigue characteristics are required.
[0008]
　Technique for increasing the corrosion resistance of the steel, WO 2012/056785 (Patent Document 3), WO 2013/111407 (Patent Document 4), and is proposed in JP 2008-274367 (Patent Document 5) ing.
[0009]
　Patent Document 3 disclosed surface hardening for machine structural steel is a mass%, C: 0.30 ~ 0.60%, Si: 0.02 ~ 2.0%, Mn: 0.35 ~ 1. 5%, Al: 0.001 ~ 0.5%, Cr: 0.05 ~ 2.0%, Sn: 0.001 ~ 1.0%, S: 0.0001 ~ 0.021%, N: 0 .0030 ~ 0.0055%, Ni: 0.01 ~ 2.0%, Cu: 0.01 ~ 2.0%, P: 0.030% or less, and O: 0.005% or less, the balance being Fe and unavoidable impurities, satisfying expressions (1) to (3). Here, equation (1) is, -0.19 ≦ 0.12 × Sn + Cu-0.1 × Ni ≦ 0.15, equation (2) is, 60 ≦ Mn / S ≦ 300, equation (3), is a Sn ≧ 0.2 × Cr.
[0010]
　Hardened steel disclosed in Patent Document 4, by mass%, C: 0.05 ~ 0.45%, Si: 0.01 ~ 1.0%, Mn: 0 super ~ 2.0%, Al: 0.001 ~ 0.06%, N: 0.002 ~ 0.03%, S: 0 ultra-0.1% P: 0 super ~ 0.05%, further Mo, V, Nb, Cu, Ni , Cr, and Sn at least one or more, and the balance has a component composition comprising Fe and unavoidable impurities, satisfying expressions (1) to (3). Here, equation (1) is, Re = (Ae / Ao) × 100 ≦ 30%, the formula (2) is, (Cmin, 1 / Co) ≧ 0.95, Formula (3), (Cmin, 2 is /Co)≧0.95. Macrostructure of hardened steel, cross-section, comprises a equiaxed region, and a columnar crystal region disposed around the equiaxed region.
[0011]
　Steel disclosed in Patent Document 5 volts, by mass%, C: 0.15 ~ 0.6%, Si: 0.05 ~ 0.5%, Mn and Cr: 0.5 in total 1-3. 5%, P: 0.05% or less, S: 0.03% or less, Cu: less than 0.3%, Ni: less than 1%, O: 0.01% or less, and Sn: 0.05 ~ 0. containing 50%, the balance being Fe and impurities. Furthermore, having the composition Cu / Sn ratio is 1 or less.
CITATION
Patent Document
[0012]
Patent Document 1: JP 2012-107295 Patent Publication
Patent Document 2: JP 2013-231212 Patent Publication
Patent Document 3: WO 2012/056785 Patent
Patent Document 4: WO 2013/111407 Patent
Patent Document 5: JP 2008-274367 JP
Summary of the Invention
Problems that the Invention is to Solve
[0013]
　In Patent Documents 3 to 5 described above, by containing Sn, has been described as corrosion resistance of the steel is increased. However, in Patent Documents 3 to 5 have not been studied in any way for the corrosion fatigue characteristics of railway wheels and railway wheels. Therefore, when using the technology of Patent Documents 3 to 5 in railway wheels, there is a case where the strength is insufficient or not adequate corrosion fatigue characteristics.
[0014]
　An object of the present invention is to provide a railway wheel which is excellent in corrosion fatigue characteristics.
Means for Solving the Problems
[0015]
　Railway wheels according to the present embodiment, by mass%, C: 0.65 ~ 0.80%, Si: 0.10 ~ 1.0%, Mn: 0.10 ~ 1.0%, P: 0. 030% or less, S: 0.030% or less, Cr: 0.05 ~ 0.20%, Sn: 0.005 ~ 0.50%, Al: 0.010 ~ 0.050%, N: 0.0020 ~ 0.015%, Cu: 0 ~ 0.20%, Ni: 0 ~ 0.20%, Mo: 0 ~ 0.20%, V: 0 ~ 0.20%, Nb: 0 ~ 0.030% and, Ti: 0 ~ 0.030%, containing, having a chemical composition the balance being Fe and impurities. Matrix organization of the plate portion of the railway wheels consists of perlite.
Effect of the invention
[0016]
　Railway wheels according to the present embodiment is excellent in corrosion fatigue characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017]
[1] Figure 1 is a diagram showing the relationship between the corrosion fatigue strength and Sn content.
FIG. 2 is a front view of the railway wheels.
FIG. 3 is a diagram showing a part of the side surface of the railway wheel.
[4] FIG. 4 is a front view of the corrosion fatigue test piece Ono-type rotating bending used in corrosion fatigue strength evaluation.
DESCRIPTION OF THE INVENTION
[0018]
　The present inventors, using the railway wheels having various chemical compositions and microstructure investigation and examined corrosion fatigue properties of railway wheels, and obtained the following findings.
[0019]
　If you want to maritime transport the railway wheels of the semi-finished state before painting in the marine, railway wheels is moisture (condensation), it is exposed to sea water, and airborne salt. At this time, there are cases where corrosion pits are generated railway wheels. In addition, railway wheel is used to after painting. Then, during use of the railway wheels, painting of the plate portion of the railway wheels are worn and peeling due to the collision of aging or foreign matter (stones) exposed material of steel, there are air quality (airborne salt when the case is exposed to be included), there are cases where corrosion pits are generated railway wheels. Due Such corrosion pits generated in the situation, the corrosion fatigue characteristics may be deteriorated.
[0020]
　To prevent corrosion fatigue of such railway wheels increases the corrosion resistance of steel in air or flying in salinity may be suppress the formation of deep corrosion pits serving as starting points of fatigue cracks. To increase the corrosion resistance of the steel is effective to stainless steel of a large amount to be contained Cr and Ni. However, the raw material cost is increased when the Cr is contained and Ni. Furthermore, productivity and strength is lowered. Cr is further in the high carbon steel used for railway wheels, to form a carbide. Therefore, it is difficult to ensure that contributes dissolved Cr content in the corrosion resistance. Accordingly, the steel containing a large amount of Cr and Ni are not suitable for railway wheels applications.
[0021]
　As described above, in order to enhance the corrosion fatigue characteristics, it is important to suppress the formation of deep corrosion pits in the plate portion of the railway wheels. It is contained the Sn in railway wheels, and corrosion under saltwater environment, and generation of corrosion pits can be suppressed. As a result, it is possible to improve the corrosion fatigue properties of the steel.
[0022]
　Figure 1 is a diagram showing the Sn content, the relationship between the corrosion fatigue strength. Figure 1 was obtained by the Examples below.
[0023]
　Referring to FIG. 1, be contained the Sn, corrosion fatigue strength of railway wheels is significantly enhanced. If Sn content is 0.005% or more, the corrosion fatigue strength becomes more 400 MPa, obtained railway wheels having excellent corrosion fatigue characteristics.
[0024]
　[Matrix Organization for]
　If matrix organization pearlite of the plate portion of the railway wheels, railway wheels having excellent toughness and ductility can be obtained. Sn is concentrated in the austenite grain boundaries. Steel made of a non-pearlite structures, such as martensite and bainite is present, the austenite grain boundaries. For this reason, it is easy to break along the prior austenite grain boundaries Sn was concentrated. As a result, toughness and ductility of the steel is lowered. If the steel of the matrix organization of pearlite, the prior austenite grain boundaries do not exist. Therefore, even if Sn is concentrated in the austenite grain boundaries before cooling, because the structure after cooling (perlite) are not present former Orth Night grain boundary does not occur breakage along the grain boundaries. Therefore, it is possible to suppress the deterioration of toughness and ductility of the steel.
[0025]
　Railway wheels according to the present embodiment has been completed based on the above findings, by mass%, C: 0.65 ~ 0.80%, Si: 0.10 ~ 1.0%, Mn: 0.10 ~ 1 .0%, P: 0.030% or less, S: 0.030% or less, Cr: 0.05 ~ 0.20%, Sn: 0.005 ~ 0.50%, Al: 0.010 ~ 0. 050%, N: 0.0020 ~ 0.015%, Cu: 0 ~ 0.20%, Ni: 0 ~ 0.20%, Mo: 0 ~ 0.20%, V: 0 ~ 0.20%, nb: 0 ~ 0.030%, and, Ti: 0 ~ 0.030%, containing, having a chemical composition the balance being Fe and impurities. Matrix organization of the plate portion of the railway wheels consists of perlite.
[0026]
　The chemical composition, in mass%, Cu: from 0.02 to 0.20%, and, Ni: may contain one or more selected from the group consisting of from 0.02 to 0.20%.
[0027]
　The chemical composition, by mass%, Mo: 0.005 ~ 0.20%, V: 0.005 ~ 0.20%, Nb: 0.010 ~ 0.030%, and, Ti: 0.010 ~ 0.030% or may contain one or more members selected from the group consisting of.
[0028]
　It described in detail below railway wheels of the present embodiment. "%" Related elements, unless otherwise specified, it means mass%.
[0029]
　[Chemical composition]
　The chemical composition of railway wheels of the present embodiment contains the following elements.
[0030]
　C: 0.65 ~ 0.80%
　carbon (C) increases the strength of the steel, improve the wear resistance and fatigue resistance. If the C content is too low, these effects can not be obtained. On the other hand, if the C content is too high, the strength of the steel becomes too high, the machinability of the finish machining is reduced. Therefore, C content is from 0.65 to 0.80%. The preferable lower limit of C content is 0.67%, more preferably 0.69%. The preferable upper limit of C content is 0.75%, more preferably 0.73%.
[0031]
　Si: 0.10 ~ 1.0%
　silicon (Si) increases the strength of steel. If Si content is too low, the effect can not be obtained. On the other hand, if the Si content is too high, the strength of the steel becomes too high, the machinability of the finish machining is reduced. Therefore, Si content is 0.10 to 1.0%. A preferable lower limit of Si content is 0.15%, more preferably 0.20%. The preferable upper limit of the Si content is 0.90%, more preferably 0.80%.
[0032]
　Mn: 0.10 ~ 1.0%
　manganese (Mn) increases the strength of the steel by refining the lamellar spacing of the pearlite structure. If the Mn content is too low, not this effect was obtained. On the other hand, if the Mn content is too high, the non-pearlite structures, such as martensite and bainite are produced, the yield in the machinability and railway wheels manufacturing process of the finish machining lowers. Therefore, Mn content is 0.10 to 1.0%. The preferable lower limit of the Mn content is 0.50%, more preferably from 0.55%. The preferable upper limit of the Mn content is 0.90%, more preferably 0.85%.
[0033]
　P: 0.030% or less
　Phosphorus (P) is an impurity. P lowers the toughness of the steel is segregated at the grain boundaries. Accordingly, P content is 0.030% or less. The preferable upper limit of the P content is 0.025%, more preferably 0.015%, still more preferably 0.012%. P content is preferably as small as possible.
[0034]
　S: 0.030% or less
　Sulfur (S) is inevitably contained. S enhances the machinability of the steel by forming a MnS. On the other hand, if the S content is too high, the formed coarse sulfide inclusions, the fatigue strength of the steel, the wheel characteristics such as toughness decreases. Thus, S content is 0.030% or less. The preferable upper limit of the S content is 0.025%, more preferably 0.012%, more preferably 0.010%. The preferable lower limit of the S content for improving the machinability is 0.008%.
[0035]
　Cr: 0.05 ~ 0.20%
　chromium (Cr) as well as Mn, a lamellar spacing of pearlite is miniaturized increase the strength of steel. If the Cr content is too low, the effect can not be obtained. On the other hand, if the Cr content is too high, the non-pearlite structures, such as martensite and bainite are produced, the yield of machinability and wheel manufacturing process of the finish machining is reduced. Therefore, Cr content is from 0.05 to 0.20%. A preferable lower limit of Cr content is 0.07%. The preferable upper limit of the Cr content is 0.18%, more preferably 0.16%.
[0036]
　Sn: 0.005 ~ 0.50%
　tin (Sn) increases the corrosion resistance of steel. Sn further suppressing the formation of corrosion pits serving as starting points of fatigue cracks, improve the corrosion fatigue characteristics of the wheel. If the Sn content is too low, these effects can not be obtained. On the other hand, if the Sn content is too high, and decreases the hot ductility of the steel, impairing the production of steel. Accordingly, Sn content is from 0.005 to 0.50%. The preferable lower limit of the Sn content is 0.15%, more preferably 0.20%. The preferable upper limit of the Sn content is 0.40%, more preferably 0.35%.
[0037]
　Al: 0.010 ~ 0.050%
　of aluminum (Al) also forms a stable nitride at high temperature range. Al nitrides suppresses the coarsening of austenite grains during heating for quenching as pinning particles, refining the structure of the steel. As a result, to improve the balance between the strength of the steel and toughness and ductility. Al is further an effective element for performing deoxidation of steel during refining. On the other hand, if the Al content is too high, toughness is reduced by generating a coarse inclusions. Therefore, Al content is 0.010 to 0.050%. A preferable lower limit of Al content is 0.015%, more preferably 0.020%. The preferable upper limit of Al content is 0.045%, more preferably 0.040%. Al content referred herein means the content of acid-soluble Al (sol. Al).
[0038]
　N: 0.0020 ~ 0.015%
　nitrogen (N) also forms a stable nitride at high temperature range. Nitrides suppresses the coarsening of austenite grains during heating for quenching as pinning particles, refining the structure of the steel. On the other hand, if the N content is too high, toughness is reduced by generating a coarse inclusions. Therefore, N content is 0.0020 to 0.015 percent. The preferable lower limit of the N content is 0.0030%. The preferable upper limit of the N content is 0.0080%, more preferably 0.0070%.
[0039]
　The remainder of the chemical composition of railway wheels according to this embodiment, consists of Fe and impurities. Here, the impurities, given to the manufacture of railway wheels industrially, ore as a raw material, scrap, or the like be those that are mixed from the manufacturing environment, affect the railway wheels of the embodiment It means what is allowed in the range not.
[0040]
　[For any element]
　railway wheels described above further, in place of part of Fe, may contain one or more selected from the group consisting of Cu and Ni. All of these elements are also optional element, increasing the strength of the steel by increasing the hardenability of steel.
[0041]
　Cu: 0 ~ 0.20%
　copper (Cu) is an optional element and may not be contained. If contained, Cu increases the strength of steel. However, if the Cu content is too high, and decreases the hot ductility of the steel, productivity is lowered. Therefore, Cu content is 0 to 0.20%. The preferable lower limit of Cu content is 0.02%, more preferably 0.04%. The preferable upper limit of Cu content is 0.15%, more preferably 0.13%.
[0042]
　Ni: 0 ~ 0.20%
　nickel (Ni) is an optional element and may not be contained. If contained, Ni increases the strength and toughness of the steel. However, if the Ni content is too high, the raw material cost becomes high. Therefore, Ni content is 0 to 0.20%. A preferable lower limit of Ni content is 0.02%, more preferably 0.04%. The preferable upper limit of the Ni content is 0.15%, more preferably 0.13%.
[0043]
　Railway wheels described above further instead of a part of Fe, Mo, V, Nb, and may contain one or more members selected from the group consisting of Ti. All of these elements are optional elements, increasing the strength of steel by refining the steel.
[0044]
　Mo: 0 ~ 0.20%
　of molybdenum (Mo) is an optional element and may not be contained. If contained, Mo increases the strength of steel by precipitation strengthening. Mo is further similar to the Mn and Cr, the lamellar spacing of the pearlite structure is miniaturized increase the strength of steel. However, if Mo content is too high, martensite and non pearlite generates such bainite, the yield in the machinability and wheel manufacturing process of the finish machining lowers. Therefore, Mo content is 0 to 0.20%. A preferable lower limit of Mo content is 0.005%, more preferably 0.008%. The preferable upper limit of the Mo content is 0.15%, more preferably 0.13%.
[0045]
　V: 0 ~ 0.20%
　vanadium (V) are optional elements may not be contained. If contained, V is, to form a fine carbide, the precipitation strengthening, enhancing the strength of steel. However, if the V content is too high, martensite and non pearlite generates such bainite, the yield in the machinability and wheel manufacturing process of the finish machining lowers. Therefore, V content is from 0 to 0.20%. The preferable lower limit of V content is 0.005%, more preferably 0.007%. The preferable upper limit of the V content is 0.15%, more preferably 0.13%.
[0046]
　Nb: 0 ~ 0.030%
　niobium (Nb) is an optional element and may not be contained. If contained, Nb forms nitrides and carbides of steel structure and miniaturized in a high temperature range, increasing the strength of steel. However, if the Nb content is too high, and decreases the hot ductility of the steel, the production of the continuous casting is reduced. Therefore, Nb content is 0 to 0.030%. The preferable lower limit of Nb content is 0.010%, more preferably 0.012%. The preferable upper limit of Nb content is 0.025%, more preferably 0.022%.
[0047]
　Ti: 0 ~ 0.030%
　titanium (Ti) is optional element and may not be contained. If contained, Ti forms nitrides and carbides of steel structure and miniaturized in a high temperature range, increasing the strength of steel. However, if the Ti content is too high, toughness of the steel is lowered. Therefore, Ti content is 0 to 0.030%. A preferable lower limit of the Ti content is 0.010%, more preferably 0.012%. The preferable upper limit of the Ti content is 0.025%, more preferably 0.022%.
[0048]
　About Matrix Organization
　Figure 2 is a front view of the railway wheels of the present embodiment, FIG. 3 is a cross-sectional view of the rim portion vicinity of the railway wheels of the present embodiment. Referring to FIGS. 2 and 3, railway wheels is provided with a rim 1, and the plate portion 2, and a boss portion 5. Rim 1 is disposed on the outer edge of railway wheels, comprising a tread 3 in contact with the rail. Boss portion 5 is formed in the center portion of the railway wheels. The center of the boss portion 5 are formed through holes, axles is pressed into the through hole.
[0049]
　The plate portion 2 is formed between the rim portion 1 and the boss portion 5, is connected to the rim portion 1 and the boss portion 5. The thickness of the plate portion 2 is less than the thickness and the thickness of the boss portion 5 of the rim 1.
[0050]
　Matrix structure of the plate portion 2 of the railway wheels of the present embodiment is composed of pearlite. In this specification, a matrix organization consisting of perlite in the matrix tissue of the plate portion 2, the area ratio of pearlite is meant that 95% or more.
[0051]
　If containing railway wheels Sn made of a non-pearlite structures, such as martensite and bainite, Sn is concentrated in the austenite grain boundaries, which lowers the mechanical properties of railway wheels. Specifically, toughness and ductility is decreased, easily cracked. If the matrix organization of railway wheels of the plate portion 2 is perlite, there is no prior austenite grain boundaries. Therefore, cracks hardly, it is possible to obtain a railway wheel which is excellent in corrosion fatigue characteristics.
[0052]
　In the matrix organization, hypereutectoid cementite decreases the toughness of the steel. Thus, the plate portion 2, the area ratio of the hypereutectoid cementite is preferably as low as.
[0053]
　Incidentally, the matrix structure of the rim 1 of the railway wheels, similar to the plate portion 2, made of perlite. That is, in the matrix tissue of the rim portion 1, the area ratio of pearlite is less than 95%. On the other hand, in the matrix tissue of the boss portion 5 of the railway wheels, the area ratio of pearlite is less than 85%, the area ratio of the pro-eutectoid ferrite is 15% or less.
[0054]
　Matrix organization is measured by the following methods. (In the plate portion 2, when the thickness of the plate portion 2 is defined as t, the t / 4 depth positions surface) railway wheels taking samples from. Of the samples taken of the surface, and the observation plane in the circumferential direction perpendicular to the plane of the plate portion 2. After polishing the observation surface, etched with a 3% nitric acid alcohol (nital corrosion solution). The etched observed surface was observed at 500-power optical microscope, to produce a photographic image of any five field.
[0055]
　In each field, pearlite, ferrite, bainite, each phase such as martensite, contrast for each different. Therefore, on the basis of the contrast, to identify the phases. Of the identified phase, the area of the perlite in each field of view ([mu] m 2 Request). The sum of the areas of perlite at all viewing, the ratio of total area of all field, defining the area ratio of pearlite and (%). A preferable lower limit of the area ratio of pearlite is 95%, more preferably 98%.
[0056]
　[Production Method]
　explaining an example of a method of manufacturing the railway wheels of the above.
[0057]
　Method of manufacturing a railway wheel of this embodiment, carried out with step (preparing step) of preparing a material, the process (molding process) for molding the railway wheels from the material, the heat treatment on the molded railway wheels and a step (heat treatment step) to. Hereinafter, the respective steps will be described.
[0058]
　[Preparation Step]
　using an electric furnace or a converter or the like, to produce a molten steel having the chemical composition described above. To produce the material by using a molten steel. For example, by continuous casting to produce a cast slab. Or by ingot casting method to produce an ingot. Against the billet or ingot, to implement the slabbing or hot forging to produce a billet as a material. Material may be a slab produced by continuous casting. The shape of the material is cylindrical is preferred.
[0059]
　Molding Step]
　using the prepared material, molding the intermediate article of railway wheels. Materials to the longitudinal cut in the direction perpendicular. And hot working in the direction perpendicular to the cutting plane, is formed into a disc shape. Moreover, in hot working, molding the intermediate article of railway wheels so that the wheels of the coarse shape. Hot working example, hot forging, a hot rolling and the like. Intermediate product because it has a shape of railway wheels, having a tread 3 and the flange portion 4.
[0060]
　[Heat treatment step]
　In the heat treatment step, carrying out the heat treatment on the molded intermediate product of railway wheels. Specifically, implementing a heat treatment on the tread 3 and the flange portion 4 of the high temperature after hot working the intermediate article. Hot working (hot forging or hot rolling) reheating the intermediate product after then (reheating), it may be performed subsequent heat treatment. Heat treatment step includes a quenching treatment. After quenching treatment, it may be subjected to a tempering process. Thus, in the tread 3 and the flange portion 4 of the rim 1, the lower layer of the outermost layer of the martensitic structure to the extent possible removal by cutting (hardened layer), it is possible to secure the hard pearlite structure.
[0061]
　In the quenching treatment can be applied to the tread surface hardening for example by the cooling water. Coolant quenching process, as long as the cooling speed suitable for the desired structure is obtained, but is not particularly limited. Cooling medium, for example, air, mist, brackish (spray), a salt bath or the like. Be applied tread quenching, the tread 3 and the flange portion 4 from the cooling rate is lower plate portion 2 tissue becomes perlite.
[0062]
　The intermediate article after quenching is carried tempering. Tempering suffices be performed at a known temperature and time. For example, the tempering temperature is 400 ~ 600 ° C., soaking time is 60 to 180 minutes.
[0063]
　The railway wheels manufactured by the above manufacturing steps, the plate portion 2, the area ratio of pearlite is 95% or more. Therefore, the wear amount of railway wheels is reduced. Furthermore, also it contains Sn, excellent workability, hard to break, it is possible to obtain a railway wheel which is excellent in corrosion fatigue characteristics.

The scope of the claims
[Requested item 1]
　By
　mass%,
　C: 0.65 ~
　0.80%, Si: 0.10 ~ 1.0%, Mn: 0.10
　~ 1.0%, P: 0.030% or
　less, S: 0.030 % or
　less,
　Cr:
　0.05 ~ 0.20%, Sn: 0.005 ~
　0.50%, Al: 0.010 ~ 0.050%, N: 0.0020 ~ 0.015%,
　Cu: 0
　0.20%
~,
　0 ~ 0.20%, Mo: 0 ~ 0.20%,
　V: 0 ~ 0.20%, Nb: 0 ~ 0.030%,
　and, Ti: 0 ~ 0. 030%, it contains,
　has a chemical composition the balance being Fe and impurities,
　a matrix structure of the plate portion is made of perlite, railway wheels.
[Requested item 2]
　A railway wheels according to claim
　1, Cu: 0.02 to 0.20%,
　and, Ni: train containing one or more selected from the group consisting of 0.02 to 0.20% use the wheels.
[Requested item 3]
　A railway wheels according to claim 1 or claim
　2,
　Mo: 0.005 ~
　0.20%, V: 0.005 ~ 0.20%, Nb: 0.010 ~ 0.030%,
　and, Ti: 0.010 ~ 0.030%, railway wheels comprising one or more members selected from the group consisting of