JP6285201B2 - Spheroidal graphite cast iron for locomotive control wheel and locomotive control wheel - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a locomotive control device used in a premises such as a steel mill and a spheroidal graphite cast iron for a locomotive control device. In this specification, the “local locomotive” means a locomotive that travels at a low speed of approximately 27 km / h or less, and is used for transporting raw materials, products, and the like in a steelworks or the like. Is a member that constitutes a part of a brake device equipped in a railway vehicle and finally generates a braking force against the wheel, and is pressed against the tread of the target wheel to generate the braking force by friction. It means a tread controller.

  Conventionally, ordinary cast iron in which flake graphite is dispersed in a layered base structure (layer structure of ferrite and cementite) made of pure iron and carbide called pearlite has been used as a material for a control wheel for a railway vehicle. This normal cast iron control device (ordinary cast iron control device) has a stable coefficient of friction even under wet conditions, and because the graphite in the structure exhibits a lubricating effect on the friction surface, there is an adverse effect on the tread surface of the wheel. It has the feature of few.

  However, the ordinary cast iron brake has a problem that the friction coefficient with respect to the speed is greatly reduced, the braking distance in the high speed range becomes long, the wear tends to wear, and the life is short. For this reason, synthetic brakes made by mixing graphite, special metal powders, fibrous materials, etc. with phenolic resin, and pressurizing and heating are used for high-speed vehicles. For limited express vehicles, sintered alloy control elements in which compounding materials such as iron powder, copper powder, graphite, and metal oxide are uniformly mixed and sintered after pressure forming have been put into practical use.

  And in cast iron brakes, special cast irons such as high manganese cast iron and chromium alloy cast iron, which have improved wear resistance compared to ordinary cast iron, have come to be used.

Patent Document 1 discloses a restrictor made of special cast iron (special cast iron restrictor). The special cast iron brake disclosed in Patent Document 1 is C: 2.7 to 3.3% (in this specification, “%” for chemical components means “mass%” unless otherwise specified), Si : 1.2-2.2%, Mn: 0.5-1.0%, P: 0.1-0.4%, S: 0.05-0.15%, Cu: 0.5-1 0.5%, Cr: 1.0 to 2.0%, Mo: 0.2 to 0.6%, and a chemical component consisting of the balance Fe. The special cast iron brake disclosed in Patent Document 1 relates to a brake used in a high pressing pressure condition (high load condition) such as a locomotive among rail cars, and Cr is 1.0 to 2 The wear resistance is improved by precipitating cementite (Fe ₃ C), which is a hard phase, in the matrix structure by containing 0.0%.

  Unlike ordinary locomotives, on-site locomotives used in steelworks are used to transport heavy items (raw materials, products, etc.) of around 1000 tons, and are generally used for 24 hours and are frequently used. There is a feature. The weight of the local locomotive is, for example, a driving maintenance weight of 60 t, an empty vehicle weight of 58.5 t, and a maximum driving speed of 30 km / h. Since this local locomotive is not as heavily loaded as the locomotive brake disclosed in Patent Document 1, the Cr content is 0.25% than the special cast iron disclosed in Patent Document 1. A special cast iron brake with a reduced Mn content of about 1.07% is used.

Japanese Patent Publication No. 1-19462

  However, Cr is expensive and difficult to recycle due to environmental problems. For this reason, there is a demand for a control wheel for a locomotive made of general cast iron to which Cr is not added or increased, and has wear resistance equal to or higher than that of a special cast iron control wheel.

  It is an object of the present invention to provide a locomotive control device having a wear resistance equal to or higher than that of a special cast iron control device currently used without adding or increasing Cr, and a spherical shape for a locomotive control device. It is to provide graphite cast iron.

  As a result of intensive studies to solve the above problems, the present inventors have obtained the following new findings A to C and completed the present invention.

  (A) Since it is said that the wear resistance in cast iron material is improved with the increase in hardness, the hardness of the restrictor is reduced by increasing the hardness of the restrictor and reducing the particle size of the spheroidal graphite cast iron. Although it was thought that the wear resistance could be improved, if the particle size of the spherical graphite is reduced and the Brinell hardness is increased, the wear resistance is unexpectedly lowered. Further, if the particle size of the spherical graphite is reduced to the same level and a difference in Brinell hardness is provided, the higher the Brinell hardness, the better the wear resistance.

  (B) When the number of spherical graphite particles is reduced and the average particle size of the spherical graphite is thereby increased, the lubricating effect on the friction surface is improved, and cracking or peeling of the base structure starting from the spherical graphite can be reduced. . That is, from observation of the cross section of the wearer's wear surface, the spherical graphite immediately below the wear surface undergoes plastic deformation, and cracks are generated and propagated from the tip of the deformed spherical graphite, resulting in delamination wear of the surface layer structure. . In spheroidal graphite cast iron with a small average particle size of spheroidal graphite, fine structure peeling occurs on the wear surface, and the number of spheroidal graphite particles that become the starting point of cracks is large, so the amount of wear increases because many cracks occur. I think that. On the other hand, in spheroidal graphite cast iron having a large average particle diameter of spheroidal graphite, fine structure peeling on the worn surface is not observed, and cracks are hardly generated. In addition, if the average particle diameter of the spherical graphite is large, the number of graphite grains that are the starting point of cracks is also reduced, so that the occurrence of cracks is reduced and the amount of wear is considered to be reduced. Further, if the base structure is made of ferrite having an area ratio of 5% or less and the remainder is a sorbite structure and the Brinell hardness is in an appropriate range, it is possible to improve wear resistance and reduce the attacking property to the tread of the wheel. . As a result, it is possible to obtain a locomotive brake device having wear resistance equal to or higher than that of a special cast iron brake wheel currently used without adding or increasing Cr.

  (C) It is not necessary to add or increase the amount of Cr, but it is acceptable to contain an amount that does not hinder cost and recyclability.

  (D) In order to reduce the number of particles of spheroidal graphite and thereby increase the average particle size of spheroidal graphite, as a spheronizing agent used in the production of spheroidal graphite cast iron, for example, no rare earth such as La or Ce is contained. A spheroidizing agent may be used. Since rare earth becomes a nucleus when spherical graphite is formed, the use of a spheroidizing agent that does not contain rare earth reduces the number of spherical graphite particles and thereby increases the average particle diameter. be able to.

The present invention is listed below.
(1) By mass%, C: 3.6 to 4.0%, Si: 2.35 to 2.95%, Mn: 0.55 to 0.60%, P: 0.05% or less, S: 0.02% or less, Cu: 0.30 to 0.37%, Mg: 0.025 to 0.050%, the chemical composition comprising the balance Fe and impurities, and the average particle size of the spherical graphite is 55.3 number of grains of spherical graphite with it μm or 99.7μm or less 24.6 pieces / mm ² or more and 59.9 pieces / mm ² or less, the base structure area ratio of 5% or less of ferrite and the balance being sorbite structure And spheroidal graphite cast iron for locomotive control wheels, characterized by having mechanical properties of Brinell hardness of 280 to 320 HBW 10/3000/30.

  (2) Spheroidal graphite cast iron for locomotive control wheel described in (1), wherein the chemical component is mass% and has Cr: 0.07% or less.

  (3) A locomotive wheel restrictor comprising the spheroidal graphite cast iron for a locomotive wheel restrictor described in the item (1) or (2).

In the spheroidal graphite cast iron for locomotive control wheels and the locomotive control wheel according to the present invention, the average particle diameter of spheroidal graphite is 55.3 μm or more and 99.7 μm or less , and the number of spheroidal graphite particles is 24.6 / It has a base structure having a ferrite structure of mm ² or more and 59.9 pieces / mm ² or less, an area ratio of 5% or less, and a remainder having a sorbite structure, and a Brinell hardness of 280 to 320 HBW 10/3000/30. Therefore, it has a wear resistance equal to or higher than that of the current locomotive control device and the spheroidal graphite cast iron for the locomotive control device without adding or increasing the amount of Cr. Therefore, according to the present invention, while maintaining the wear resistance equivalent to or better than the current locomotive control wheel locomotive and the spheroidal graphite cast iron for the locomotive control wheel, the locomotive control is low in cost and excellent in recyclability. Spheroidal graphite cast iron for a wheel and locomotive control wheel can be provided.

Fig.1 (a) is explanatory drawing which shows typically the testing machine (table testing machine) of a bench test, and FIG.1 (b) is a two-plane figure of the test piece of a bench test. FIG. 2 is an explanatory view showing a simplified locomotive used in an actual machine test, FIG. 2 (a) is a side view, and FIG. 2 (b) is a plan perspective view showing the arrangement of the control members in the preliminary test. FIG. 2C is a perspective plan view showing the arrangement of the control members in this test. FIG. 3 is a side view conceptually showing the arrangement of the control members with respect to the wheels. FIGS. 4A and 4B are explanatory views showing the control device used in the actual machine test. FIG. 4A is a perspective view and FIG. 4B is a side view. FIG. 5 is an explanatory view showing a method for measuring the wear amount of the brake element. FIG. 6 is a graph showing the change over time of the measurement results of the wear amount of the control wheel of the present invention and the control wheel of the conventional example.

  The chemical composition, metal structure, mechanical properties, and manufacturing method of the locomotive brake and the spheroidal graphite cast iron for the locomotive brake according to the present invention will be described sequentially. In the following description, the case where the locomotive is the above-described local locomotive is taken as an example.

1. Chemical component The chemical component is generally used in spheroidal graphite cast iron and has the following actions. In the present invention, this action is obtained and various performances (wear resistance, In order to make the material balanced in terms of thermal cracking, strength, toughness, wheel wear, temperature rise, braking distance, etc., the content of each component is limited as listed below.

(C: 3.6-4.0%)
As the C content increases, the fluidity of the molten metal increases. However, if the C content exceeds 4.0%, the wear resistance decreases, and if the C content is less than 3.6%, the shrinkage of the cast iron is large. And lead to cracks and shrinkage. For this reason, C content shall be 3.6% or more and 4.0% or less. The C content is more preferably 3.7% or more, and more preferably 3.9% or less.

(Si: 2.35 to 2.95%)
Si is an important element for graphitizing carbon. When the Si content is 2.35% or more, the acid resistance and heat resistance are improved, and the thermal expansion coefficient is increased. However, if the Si content exceeds 2.95%, ferrite is generated and the wear resistance is lowered. For this reason, Si content shall be 2.35% or more and 2.95% or less. The Si content is more preferably 2.4% or more.

(Mn: 0.55 to 0.60%)
When Mn is contained in an amount of 0.55% or more, the strength is improved by solid solution strengthening and the thermal expansion coefficient is increased. However, if the Mn content exceeds 0.60%, the generation of heat spots may be promoted on the tread surface (friction surface) of the wheel. For this reason, Mn content shall be 0.55% or more and 0.60% or less.

(P: 0.05% or less)
When the P content exceeds 0.05%, a ternary eutectic structure (steadite) of Fe, C, and P is formed, the fluidity of the molten metal is slightly improved, and the strength and wear resistance are also improved. Decrease brittleness and increase brittleness. Therefore, the P content is 0.05% or less.

(S: 0.02% or less)
If the S content exceeds 0.02%, the machinability and wear resistance are slightly improved, but the fluidity of the molten metal is deteriorated in order to increase the freezing point of cast iron. For this reason, S content shall be 0.02% or less.

(Cu: 0.30 to 0.37%)
When the Cu content is 0.30% or more, the strength and hardness increase, but when the Cu content exceeds 0.37%, the elongation decreases. For this reason, Cu content shall be 0.30% or more and 0.37% or less.

(Mg: 0.025 to 0.050%)
Mg is added to the molten metal as a chemical component contained in the spheroidizing agent used in the production of spheroidal graphite cast iron. When the Mg content is less than 0.025%, poor spheroidization occurs, and when the Mg content exceeds 0.050%, abnormal graphite and excessive slag are induced, which is the target in any case. Spherical graphite cannot be obtained. By containing Mg in an amount of 0.025% to 0.050%, the spheroidization of graphite is promoted. From the same viewpoint, the Mg content is more preferably 0.03% or more.

(Cr: 0.07% or less)
Cr is an optional element in the present invention, and may be included in the above range that does not cause a problem in cost, and particularly in the above range that does not impair recyclability due to environmental problems. Wear resistance is improved by containing Cr.

In addition, in order to improve hardenability, you may contain Ni or Mo 0.8% or less.
The balance other than the above is Fe and impurities.

2. Metal structure: average particle diameter of spherical graphite: 55 μm or more, number of particles of spherical graphite is 60 pieces / mm ² or less, base structure: ferrite with an area ratio of 5% or less, and the remainder is a sorbite structure. As described above, the larger the value, the better the lubrication effect on the friction surface and the higher the wear resistance. In order to ensure the wear resistance equivalent to or better than the current on-site locomotive control wheel and the spheroidal graphite cast iron for the on-site locomotive control wheel, it should be 55 μm or more. The upper limit of the average particle diameter of the spherical graphite is not particularly limited, but in order to obtain a uniform lubricating effect over the entire friction surface, it is desirable that graphite having the same particle diameter be uniformly distributed as much as possible. It is desirable that

If the number of spheroidal graphite particles is too small, the effect of preventing adhesion due to graphite lubrication is reduced, so that it is preferably 40 particles / mm ² or more, and in order to obtain the desired wear resistance, it is 60 particles / mm ² or less. is there. In addition, the value calculated | required by the method mentioned later is used for the number of particles of spherical graphite.

  In order to suppress the number of particles of spheroidal graphite and increase the average particle size of spheroidal graphite as described above, as a spheronizing agent used in the production of spheroidal graphite cast iron, for example, a rare earth such as La or Ce is contained. A spheroidizing agent (for example, trade name OGL-6H (manufactured by Osaka Special Alloy Co., Ltd.)) may be used.

  Since rare earth becomes a nucleus when spherical graphite is formed, by using a spheroidizing agent that does not contain rare earth, it is possible to reduce the number of spherical graphite particles and thereby increase the average particle diameter of spherical graphite. it can. In addition, the standard value of brand name OGL-6H (made by Osaka Special Alloy Co., Ltd.) is mass%, Si: 44.0 to 48.0%, Mg: 6.0 to 6.50%, Ca: 2. 70 to 3.30%, Fe: Bal with a particle size of 3 to 25 mm.

  In order to achieve the Brinell hardness described later, the base structure is made to have a ferrite with an area ratio of 5% or less by quenching and tempering, and the remainder to a sorbite structure (eutectoid structure made of ferrite base and fine cementite). When the area ratio of ferrite exceeds 5%, the hardness decreases, and the desired Brinell hardness described later cannot be achieved.

  In the present invention, the measurement of the average particle diameter and the number of particles of spherical graphite, the specification of the base structure and the measurement of the area ratio of ferrite are all performed by the following methods.

(2-1) Sample preparation Water-resistant paper is used as a tissue observation sample, and rough observation of the observation surface is performed in the order of # 400, # 800, and # 1200. Finally, mirror finishing is performed by buffing using alumina abrasive grains.

(2-2) Tissue photography The organization photographs were taken five times at a magnification of 100 times the surface texture before and after corrosion. Corrosion is performed for 5 seconds, and a nital solution (ethanol plus 5% nitric acid) is used as the corrosion solution.

(2-3) Image analysis (2-3-1) Number of graphite particles (pieces / mm ² )
A photograph of the structure before corrosion is taken into the image processing software, and the number of spherical graphite is counted by discriminating the spherical graphite and the matrix structure. At this time, particles of 15 μm or less are excluded, and half of the spherical graphite on the edge of the image is counted. The number of spherical graphite counted is divided by the area of the entire image, and the number of graphite particles is calculated. In this procedure, five tissue photographs are measured, and an average value for five times is calculated.

(2-3-2) Average particle size of graphite (μm)
The diameter of the circumscribed circle of the spherical graphite counted when calculating the number of graphite particles is measured, and the average particle diameter is calculated from each structure photograph. Measurement of five tissue photographs is performed according to the above procedure, and an average value for five times is calculated.

(2-3-3) Ferrite area ratio (%)
Takes a texture photograph after corrosion into image analysis software and discriminates spherical graphite + sorbite or pearlite. The area of ferrite is calculated by subtracting the area of spherical graphite + sorbite or pearlite from the area of the entire image. Spherical graphite is discriminated from the structure photograph before corrosion, and the area of the spherical graphite is subtracted from the area of the entire image to calculate the area of the base tissue. The ferrite area ratio is calculated by dividing the ferrite area by the area of the base structure. Measurement of five tissue photographs is performed according to the above procedure, and an average value for five times is calculated.

3. Mechanical properties Since the Brinell hardness of the wheel is about 350 to 360 HBW 10/3000/30, if the Brinell hardness of the control exceeds 320 HBW 10/3000/30, the wheel may be damaged and 280 HBW 10/3000/30 If it falls below, the amount of wear of the control will increase. For this reason, the Brinell hardness of a control is made 280-320HBW10 / 3000/30. In the present invention, the Brinell hardness is measured based on JIS Z2243.

  The range in which the Brinell hardness is 280 to 320 HBW 10/3000/30 in the control device is a range from the surface layer of the control device to a depth position of at least 15 mm at the time of shipment.

The tensile strength is desirably 850 to 900 N / m ² or more, and the elongation is desirably 1 to 8% or more. Tensile strength and elongation are measured based on JIS Z2241.

4). Manufacturing Method The on-site locomotive control device according to the present invention is preferably manufactured by the following manufacturing method.

  If necessary, pig iron for spheroidal graphite cast iron is blended with the iron scrap, which is a raw material, so as to have the above-described chemical components. The purpose of blending pig iron is to increase the number of high-strength steel to which Mn is added as iron scrap in recent years, so that this is diluted to obtain spheroidal graphite cast iron having the above composition.

  Next, by adding a spheroidizing agent that does not contain a rare earth such as La or Ce to the molten metal, and adjusting the Mg content to 0.025% or more and 0.050% or less, the above-described chemical components are adjusted. Let the molten metal have.

  And after casting this molten metal into the mold of a control locomotive for a local locomotive, it is heated to a temperature of 850 to 900 ° C., held at a temperature according to the thickness, and then rapidly cooled in water or oil to form a structure. By subjecting the austenite (γ) phase to martensite transformation without causing pearlite transformation, followed by quenching and tempering by reheating to 500 to 600 ° C. and then air cooling or furnace cooling, Is 5% or less and the balance is a sorbite structure, and the Brinell hardness is 280 to 320 HBW 10/3000/30.

  After that, the necessary locomotive processing (cutting processing, etc.) is performed to manufacture the on-site locomotive control device according to the present invention.

A bench test conducted to confirm the effect of the present invention will be described.
FIG. 1A is an explanatory diagram schematically showing the bench test machine 10, and FIG. 1B is a two-side view of the test piece 13 of the bench test.

As shown in FIG. 1 (a), the bench tester 10 is a mechanism for directly pressing the test piece 13 against a steel wheel 12 (293HBW10 / 3000/30) having a diameter of 280 mm using a weight 11 in accordance with the principle of leverage. The wheel 12 is rotated at a predetermined speed (27 km / h) for 60 seconds, and at the same time as the motor switch is stopped, the test piece 13 is attached to the wheel 12 in the inertial running state by the inertial force of the flywheel. Press with a surface pressure of 1 Mpa. The surface pressure was calculated as {weight weight (100 kg) × gravity acceleration (9.8 m / s ² ) × l ₁ / l ₂ } / contact surface area (about 30 mm × 30 mm) ≈1.1 MPa.

  As shown in FIG. 1 (b), the test piece 13 includes a specimen (example of the present invention) that satisfies all of the chemical composition, metal structure, and mechanical properties of the spheroidal graphite cast iron for locomotive control wheels according to the present invention. The locomotive body of the locomotive body (conventional example) and a specimen (comparative example) in which any one of the chemical composition, metal structure and mechanical properties deviates from the spheroidal graphite cast iron for locomotive body wheel according to the present invention. A 30 mm × 28 mm rectangular parallelepiped is cut out and machined so that the contact surface with the wheel 12 has the same curvature as the wheel 12. However, in order to familiarize the contact surface between the wheel 12 and the test piece 13 before the test, surface acclimation under test conditions is performed until the contact surface between the test piece 13 and the wheel 12 reaches 80% or more.

  At this time, since both the wheel 12 and the test piece 13 are heated to high temperatures due to frictional heat, the test is repeated after sufficiently cooling.

In the actual bench test, the “weight reduction amount (g)” and “time to wheel stop (s)” of the test piece 13 are measured every time. The above measurement is repeated 20 times, and the average value of 20 times is calculated as “wear weight (g)” and “braking time (s)”, and “wear volume (mm ³ )” and “braking distance ( m) ”and“ specific wear (mm ² / N) ”. And abrasion resistance is evaluated by the relative comparison of the calculated specific wear amount. Here, the arm length of the bench test machine is l ₁ = l ₂ , and the braking load is 980 N from the surface pressure (1.1 Mpa) when the test piece 13 is pressed against the wheel 12. The initial speed of the brake is 7.5 m / s because the wheel 12 is rotated at a predetermined speed (27 km / h). The specific gravity of the test piece, conventional example 7.16 g / mm ^3, the present invention examples and comparative examples was 7.15 g / mm ^3.

The results of the bench test are summarized in Table 1. In Table 1, “Evaluation” has a threshold value of 1.4 × 10 4 because the smallest specific wear amount among the test pieces 13 cut out from the conventional example was 1.41 × 10 ⁻⁷ mm ² / N. ^-7 mm ² / N, specific wear amount of 1.4 × 10 ⁻⁷ mm ² / N or less is “◯”, and over 1.4 × 10 ⁻⁷ mm ² / N is “×” It was.

  No. in Table 1 As shown in Nos. 1 to 23, when all the conditions specified in the present invention are satisfied, good abrasion resistance can be obtained. As shown in 24-41, it is understood that the wear resistance is unsatisfactory unless the conditions defined in the present invention are satisfied.

  On-site locomotives used on the premises of steelworks are equipped with the on-site locomotive control device according to the present invention (example of the present invention) and the current on-site locomotive control device (conventional example), and are used for normal transportation. An actual machine test (main test) running as the work was performed, and the amount of wear of the control wheel (the thickness of the control wheel) was measured once a month for four months.

  Prior to this test, in order to confirm the effect of the difference in the average particle diameter, the number of grains and the Brinell hardness of the spherical graphite on the wear resistance, the average particle diameter, the number of grains and the Brinell hardness of the spherical graphite were determined. An actual machine test (preliminary test) in which a control device outside the scope of the present invention (Comparative Examples A and B) is manufactured, and Comparative Examples A and B and the conventional example are mounted on a local locomotive and travels according to a normal transportation operation. The amount of wear (thickness of the control wheel) of Comparative Examples A and B and the conventional example was measured at a rate of once per month for 3 months.

Details of the main test and the preliminary test will be described below.
(1) Chemical constituents Table 2 summarizes the chemical constituents of the inventive examples and conventional examples in this test. In addition, Cr contained in the examples of the present invention is not positively added, but is derived from impurities inevitably contained in the raw material (iron scrap). The chemical components of Comparative Examples A and B in the preliminary test are the same as the chemical components of the present invention example shown in Table 2, and the chemical components of the conventional example in the preliminary test are the chemical components of the conventional example in the main test shown in Table 2. Is the same.

  The present invention example in this test, the conventional example and comparative examples A and B in the preliminary test and the conventional example also measure the average particle diameter and number of particles of spherical graphite, specify the base structure and measure the ferrite area ratio as in item 2. This was done by tissue observation and image analysis. Brinell hardness was measured based on JIS Z2243, and tensile strength and elongation were measured based on JIS Z2241.

(2) Manufacture of locomotive control wheel locomotive iron scrap was mixed with raw iron scrap so as to have the composition shown in Table 2, and was manufactured by a normal manufacturing method of spheroidal graphite cast iron. Further, as a spheronizing agent, for example, a spheronizing agent containing no rare earth such as La or Ce (trade name OGL-6H, manufactured by Osaka Special Alloy Co., Ltd.) was used. By using this spheroidizing agent, the number of spherical graphite particles was reduced and the average particle size was increased accordingly.

  In addition, after casting, it is heated to a temperature of 850 to 900 ° C., held at a temperature according to the thickness, and then rapidly cooled in water or oil to make the structure martensite without undergoing pearlite transformation from the austenite (γ) phase. After the transformation was performed, quenching and tempering by reheating to 500 to 600 ° C. and then air cooling or furnace cooling were performed, so that the base structure had a ferrite area ratio of 5% or less and the balance was a sorbite structure.

  In Comparative Examples A and B, the inoculant was added in a different amount together with the above spheroidizing agent to increase the number of spherical graphite particles, thereby reducing the particle size. In addition, quenching and tempering were performed so that the base organization became a sorbite organization.

(3) Preliminary test conditions FIGS. 2A and 2B are explanatory views showing the on-site locomotive 1 used in the actual machine test in a simplified manner, FIG. 2A is a side view, and FIG. 2B is a control R1 in the preliminary test. , R2, R3, R4, R5, R6, R7, R8 and L1, L2, L3, L4, L5, L6, L7, L8 are shown in a plan perspective view, and FIG. It is a plane perspective view which shows collectively arrangement | positioning of the control elements R1, R2, R3, R4 and L1, L2, L3, L4 in this test.

  FIG. 3 is a side view conceptually showing the arrangement of the restrictors L5 and L6 with respect to the wheel 4 in FIG.

  The diameters of the wheels 2 to 9 of the local locomotive 1 are 860 mm, and as shown in FIG. 3, the control members R1, R2, R3, R4, R5, R6, R7, R8 and L1, L2, L3 L4, L5, L6, L7, and L8 are arranged with respect to one wheel so that four wheels of each of right (R) and left (L) are sandwiched at intervals of about 180 °.

  FIGS. 4A and 4B are explanatory views showing the control R1 used in the actual machine test, in which FIG. 4A is a perspective view and FIG. 4B is a side view.

  The shape of the restrictor is as shown in FIG. 4 (a) and FIG. 4 (b) as an example of the restrictor R1, and its total length A is the restrictor R1, R2, R3, R4, R5, R6, R7. , R8 and L1, L2, L3, L4, L5, L6, L7, and L8 are 350 mm.

  First, the wear resistance of cast iron materials is said to improve as the hardness increases. By increasing the hardness of the brake and reducing the particle size of the spherical graphite, the wear resistance of the brake is reduced. 4 comparative examples A and B having the metal structure (average particle diameter, number of grains and matrix structure of spherical graphite) and mechanical properties (Brinell hardness) shown in Table 3 based on the assumption that Each was manufactured, and a preliminary test was performed by comparison with a conventional example. Measurement of the average particle diameter and the number of particles of the spherical graphite, and specification of the base structure were performed by structural observation and image processing similar to those in Item 2, and Brinell hardness was measured based on JIS Z2243.

  In the preliminary test, as shown in FIG. 2B, the front two wheels are arranged by combining Comparative Example A or Comparative Example B and the conventional example as a pair, and the rear two wheels are combined with the same material as a pair. Arranged. That is, in FIG. 2B, the control members L1, L3, R7 and R8 are the comparative example A, the control members R2, R4, L5 and L6 are the comparative example B, and the control members R1, L2, R3 and L4 , R5, R6, L7 and L8 are conventional examples. In FIG. 2B, Comparative Example A is painted black and Comparative Example B is hatched to distinguish Comparative Example A, Comparative Example B, and Conventional Example.

  The monthly mileage (km) of each month during the three months, which is the preliminary test period, was 1st month: not measured, 2nd month: 2290.7 km, 3rd month: 2281.9 km.

Other test conditions are as follows.
(A) Kinetic energy: about 9200kJ (when loaded with 1000t)
(B) Pusher pressing force: about 1 MPa
(C) Brake initial speed: 15 km / h
(D) Number of tests: The number of tests is not possible due to actual equipment. It is roughly proportional to the distance traveled.

(4) Evaluation method The wear amounts of the control members R1 to R8 and L1 to L8 were measured in the following manner to evaluate the wear resistance.

FIG. 5 is an explanatory view showing a method for measuring the wear amount of the brake rings R1 to R8 and L1 to L8.
Before starting the preliminary test, mark 45mm from the friction surface (working surface) of the control wheels R1 to R8 and L1 to L8, and the thickness from the mark to the friction surface at the upper, middle, and lower points at the time of measurement. Was measured, and the average value of the upper, middle, and lower three locations was taken, and the amount of decrease from the initial value was taken as the wear amount.

(5) Preliminary test results Table 4 summarizes the measurement results of the wear amounts of Comparative Examples A and B and the conventional example. In Table 4, the comparative example B of the restrictor R2 and the conventional example of the restrictor R3 show clear uneven wear on the friction surface at the measurement point in the first month, and an accurate thickness measurement is possible. Because it was not, it was excluded from the measurement target, replaced with the conventional example, and the preliminary test was continued. Similarly, Comparative Example A of the restrictor R7 was excluded from the measurement target because clear frictional wear was observed on the friction surface at the measurement point in the third month.

  As shown in Table 4, there was no significant difference in the amount of wear between Comparative Examples A and B and the conventional example, but the conventional example with the largest particle size of spherical graphite and the lowest Brinell hardness was the most worn amount. When Comparative Examples A and B having a smaller Brinell hardness than that of the conventional example are compared, Comparative Example A having a larger spherical graphite particle size and a higher Brinell hardness has a smaller wear amount than Comparative Example B. became.

(6) Main test conditions The present invention example is based on the result of the preliminary test, and the diameter of the spheroidal graphite cast iron for a local locomotive control wheel is increased by reducing the number of spheroidal graphite particles. In order to increase the Brinell hardness within a range not exceeding the thickness, a spheroidizing agent not containing a rare earth was used to perform quenching and tempering after casting.

  In this test, as shown in FIG. 2 (c), the present invention example and the conventional example were paired and arranged for one wheel. That is, in FIG. 2C, the control members R1, R3, L2, and L4 are examples of the present invention, and the control members R2, R4, L1, and L3 are conventional examples. In FIG. 2 (c), the control members R1, R3, L2, and L4 of the present invention are hatched to distinguish them from the conventional control members R2, R4, L1, and L3.

  The monthly mileage (km) of each month during the 4 months of this test period is as follows: 1st month: 1454.2 km, 2nd month: 1286.2 km, 3rd month: 1288.6 km, 4th month: 1522. It was 5 km.

Other test conditions are the same as in the preliminary test as follows.
(E) Kinetic energy: about 9200kJ (when loaded with 1000t)
(F) Control wheel pressing force: about 1 MPa
(G) Brake initial speed: 15 km / h
(H) Number of tests: Measurement is not possible due to actual equipment. It is roughly proportional to the distance traveled.

(7) Evaluation method Abrasion resistance was evaluated by the same evaluation method as the preliminary test evaluation method described above.

  In addition, the amount of wear of the wheel was measured, and the control members R1 to R4, L1 to L4 and the appearances 4 and 5 of the wheel were observed to confirm the presence or absence of cracks or cracks. Further, thermolabels were attached to the control members R1 to R4 and L1 to L4, and the degree of temperature increase was measured.

(8) Results of this test Table 5 summarizes the measurement results of the wear amounts of the control members R1, R3, L2 and L4 of the present invention and the conventional control devices R2, R4, L1 and L3 of the present invention. Is shown graphically in FIG.

  In the graph of FIG. 6, the control wheels R1, R3, L2 and L4 of the present invention and the conventional control wheels R2, R4, L1 and L3 arranged in combination as a pair are plotted with the same kind of marks. The plots of the control wheels R1, R3, L2 and L4 of the invention example are connected by a solid line, and the plots of the control wheels R2, R4, L1 and L3 of the conventional example are connected by a broken line.

  When comparing the thicknesses of the control wheels R1, R3, L2 and L4 of the present invention and the conventional control wheels R2, R4, L1 and L3 arranged in combination as a pair, the graphs of Table 5 and FIG. As shown, in any of the wheels, the remaining thicknesses of the restrictors R1, R3, L2 and L4 of the present invention are thicker than the remaining thicknesses of the conventional restrictors R2, R4, L1 and L3. The control members R1, R3, L2 and L4 were confirmed to have wear resistance equal to or higher than that of the conventional control members R2, R4, L1 and L3.

  In addition, the control members R1, R3, L2 and L4 of the present invention after this test have no cracks or cracks, and there are no practical problems with thermal cracks, strength, and toughness. It was confirmed that the influence (the amount of wear of the wheel) of the above is comparable to that of the conventional control wheels R2, R4, L1 and L3, and there is no problem. Furthermore, the temperature rise was all about 120 ° C., and there was no problem. Although the braking distance was not measured, there was no problem because it was the same as the normal driving feeling.

1 Local locomotive (locomotive)
2-9 Wheel 4 Wheel

Claims (3)

In mass%, C: 3.6 to 4.0%, Si: 2.35 to 2.95%, Mn: 0.55 to 0.60%, P: 0.05% or less, S: 0.02 % Or less, Cu: 0.30 to 0.37%, Mg: 0.025 to 0.050%, the chemical component consisting of the balance Fe and impurities, and the average particle size of the spherical graphite is 55.3 μm or more and 99 And having a base structure in which the number of spheroidal graphite particles is 24.6 pieces / mm ² or more and 59.9 pieces / mm ² or less, the area ratio is 5% or less, and the balance is a sorbite structure. Spheroidal graphite cast iron for locomotive control wheels, characterized by having mechanical properties of Brinell hardness of 280 to 320 HBW 10/3000/30.   The spheroidal graphite cast iron for a locomotive control wheel according to claim 1, wherein the chemical component has a mass% of Cr: 0.07% or less.   A locomotive wheel restrictor comprising the spheroidal graphite cast iron for a locomotive wheel restrictor according to claim 1 or 2.

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