Method for heat treating a railway wheel

Abstract

This invention discloses a heat treatment method for train wheels, comprising the steps of: S1, heating the wheel; S2, water-quenching the wheel; and S3, tempering the wheel. In step S2, a composite nozzle is used, with a first nozzle region, a second nozzle region, and a third nozzle region sequentially arranged on the composite nozzle. The first nozzle region is equipped with a first nozzle for spraying air onto the wheel tread surface, the second nozzle region is equipped with a second nozzle for spraying water mist onto the wheel tread surface, and the third nozzle region is equipped with a third nozzle for spraying cooling water onto the wheel tread surface. This heat treatment method for train wheels utilizes a composite nozzle during quenching to reduce the near-surface cooling rate of the wheel tread surface. By employing compressed air and appropriately adjusting the flow rate of cooling water (small / large flow), the rapid cooling of the near-surface layer of the rim is reduced, effectively increasing the cooling rate of the internal matrix. This results in a more uniform microstructure in the radial direction of the wheel rim, achieving a uniform transformation of the internal microstructure and reducing the hardness gradient.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology for train wheels. Specifically, this invention relates to a heat treatment method for train wheels. Background Technology

[0002] With increasing demands for train ride comfort and safety, higher requirements have been placed on the radial hardness gradient of train wheel rim sections. High-speed train wheels require two radial cross-sections to be taken, with a 10mm interval below the tread and a 20mm interval in the rim height direction for hardness testing. The hardness difference at the same depth should not exceed 20 HBW. Two quarter-circumferential cross-sections are also taken circumferentially, with a 10mm depth interval for measurement. The hardness difference at the same depth should not exceed 20 HB.

[0003]

[0004] As can be seen from the table above, the requirements for hardness uniformity vary among different standards. Currently, the hardness uniformity requirements for high-speed trains in China are the most stringent, with the actual requirement being 30 HBW based on historical data.

[0005] Currently, the heat treatment methods for train wheels mainly include two types of quenching: tread and immersion. The temperature difference near the surface of the tread is large, which leads to rapid cooling of the near-surface layer and the formation of a rapid cooling layer. The large amount of water spraying does not contribute much to the internal cooling rate, resulting in a lower internal cooling rate. At a lower cooling rate, the spacing between pearlite lamellars is large, which in turn leads to a large hardness difference, making it difficult for train wheels to meet the requirements of a low hardness gradient.

[0006] The aim is to provide an improved heat treatment method for train wheels, particularly regarding how to homogenize the microstructure of the wheel rim in the radial direction, achieve a uniform transformation of the internal microstructure of the rim, and reduce the hardness gradient. Summary of the Invention

[0007] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a heat treatment method for train wheels, the purpose of which is to achieve uniform microstructure in the radial direction of the wheel rim, realize a uniform transformation of the internal microstructure of the rim, and reduce the hardness gradient.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a heat treatment method for train wheels, comprising the following steps:

[0009] S1. Heating the wheels;

[0010] S2. Water quenching is performed on the wheels;

[0011] S3. Temper the wheels;

[0012] In step S2, a composite nozzle is used, which is provided with a first nozzle area, a second nozzle area and a third nozzle area in sequence. The first nozzle area is provided with a first nozzle for spraying air onto the wheel tread, the second nozzle area is provided with a second nozzle for spraying water mist onto the wheel tread, and the third nozzle area is provided with a third nozzle for spraying cooling water onto the wheel tread.

[0013] The water flow rate of the second nozzle is less than that of the third nozzle.

[0014] The water flow rate of the second nozzle is 3.0-4.9 L / min, and the water flow rate of the third nozzle is 15-20 L / min.

[0015] The air pressure of the first nozzle is 40-60 Pa.

[0016] The air outlet angle of the first nozzle is 90°.

[0017] The water outlet angles of the second nozzle and the third nozzle are 55° to 80°.

[0018] In step S2, six composite nozzles are used, the wheel is located on the quenching platform, and all composite nozzles are evenly distributed along the circumference of the quenching platform.

[0019] In step S1, the wheel is heated to 840-860°C and then kept at that temperature for 2.0-3.0 hours.

[0020] In step S2, the time for water quenching the wheel is 300 seconds.

[0021] In step S3, the tempering temperature is set to 460–500°C.

[0022] The heat treatment method for train wheels of the present invention uses a composite nozzle during quenching to reduce the cooling rate of the wheel tread near the surface. By using compressed air and appropriate adjustment of small / large flow rate cooling water, the degree of rapid cooling of the rim near the surface is reduced, effectively increasing the cooling rate of the internal matrix, making the structure of the wheel rim uniform in the radial direction, realizing the uniform transformation of the internal structure of the rim, and reducing the hardness gradient. Attached Figure Description

[0023] This manual includes the following figures, which illustrate the following:

[0024] Figure 1 This is a schematic diagram of the composite nozzle structure;

[0025] The diagram is marked as follows:

[0026] 1. First nozzle; 2. Second nozzle; 3. Third nozzle; 4. First nozzle area; 5. Second nozzle area; 6. Third nozzle area. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0028] It should be noted that in the following embodiments, the terms "first," "second," and "third" do not represent an absolute distinction in structure and / or function, nor do they represent the order of execution; they are merely for the convenience of description.

[0029] This invention provides a heat treatment method for train wheels, comprising the following steps:

[0030] S1. Heating the wheels;

[0031] S2. Water quenching is performed on the wheels;

[0032] S3. Temper the wheels.

[0033] Specifically, this invention mainly addresses the problem of excessive radial hardness gradient in the cross-section of wheel rims. By designing a novel conformal quenching nozzle, the cooling rate near the surface of the wheel tread is reduced. By utilizing compressed air and appropriately adjusting the flow rate of cooling water (small / large flow), the rapid cooling of the near-surface layer of the rim is reduced, effectively increasing the cooling rate of the internal matrix. This results in a more uniform microstructure in the radial direction of the wheel rim, achieving a uniform transformation of the internal microstructure and reducing the hardness gradient.

[0034] In step S2 above, a composite nozzle is used, such as... Figure 1 As shown, the composite nozzle head is sequentially configured with a first nozzle area, a second nozzle area, and a third nozzle area, with the second nozzle area located between the first and third nozzle areas. The first nozzle area contains multiple first nozzles for spraying air onto the wheel tread. The second nozzle area contains multiple second nozzles for spraying water mist onto the wheel tread, with the cooling water from the second nozzles being atomized. The third nozzle area contains multiple third nozzles for spraying cooling water onto the wheel tread.

[0035] Preferably, the water flow rate of the second nozzle is less than that of the third nozzle. The water flow rate of the second nozzle is 3.0-4.9 L / min, and for example, it can be 3.2 L / min, 3.4 L / min, 3.5 L / min, 3.6 L / min, 4.0 L / min, 4.2 L / min, 4.4 L / min, 4.6 L / min, or 4.8 L / min. The water flow rate of the third nozzle is 15-20 L / min, and for example, it can be 16 L / min, 17 L / min, 18 L / min, or 19 L / min. By selecting different nozzles and water flows, the cooling rate inside the wheel can be adjusted.

[0036] Preferably, the air pressure of the first nozzle is 40-60 Pa. For example, the air pressure of the first nozzle can be 42 Pa, 44 Pa, 46 Pa, 48 Pa, 50 Pa, 52 Pa, 54 Pa, 56 Pa, 58 Pa, or 59 Pa. By selecting different air pressures, slow cooling of the surface metal can be achieved, reducing the occurrence of abnormal structures.

[0037] Preferably, the air outlet angle of the first nozzle is 90°, and the airflow injected by the first nozzle onto the wheel tread is horizontal and perpendicular to the wheel tread. By vertically blowing compressed air onto the wheel tread, the difference in cooling rate between the extremely thin metal of the tread and water cooling is reduced.

[0038] Preferably, the water outlet angle of the second nozzle is 55° to 80°. For example, the water outlet angle of the second nozzle is 56°, 60°, 64°, 68°, 70°, 74°, 76°, or 78°. By selecting a low-flow nozzle angle, the cooling rate of the surface metal can be adjusted.

[0039] Preferably, the water outlet angle of the third nozzle is 55° to 80°. For example, the water outlet angle of the third nozzle is 56°, 60°, 64°, 68°, 70°, 74°, 76°, or 78°. By selecting the angle of the high-flow nozzle, the cooling rate of the internal metal can be adjusted.

[0040] Preferably, in step S2 above, six composite nozzles are used. The wheel is located on the quenching platform with the wheel axis being a vertical line. All composite nozzles are evenly distributed along the circumference of the quenching platform, that is, all composite nozzles are evenly distributed circumferentially on the outer side of the wheel to ensure that the wheel tread can be completely covered when the wheel rotates.

[0041] In this embodiment of the invention, to ensure that the cross-sectional hardness gradient meets the technical requirements, a heat treatment process scheme was designed based on parameters such as the required hardness value, rim thickness, heat transfer coefficient, and temperature. The process involves setting the quenching compressed air time T1, the small-flow water spraying time T2, and the large-flow water spraying time T3 according to the thickness of the wheel rim, covering the entire wheel rim. Simultaneously, the wheel rotates, allowing the rim area to gradually cool and achieve the required gradient.

[0042] In step S2 above, the time for each composite nozzle to spray water onto the wheel for quenching is T = T1 + T2 + T3. Specifically, the time for the first nozzle in the first nozzle area to spray air onto the wheel tread is T1, which air-cools the wheel; then the time for the second nozzle in the second nozzle area to spray water mist onto the wheel tread is T2, which atomizes and cools the wheel; and finally, the time for the third nozzle in the third nozzle area to spray cooling water onto the wheel tread is T3, which water-cools the wheel.

[0043] In step S2 above, the time T1 for the first nozzle to spray air onto the wheel tread is T1 = θ1 * D1 * α 空 (C0-C1) / v1, the time T2 for the second nozzle to spray water mist onto the wheel tread surface is T2 = θ2 * D2 * α 水 (C1-C2) / v2, the time T3 for the third nozzle to spray cooling water onto the wheel tread is T3 = θ3 * D3 * α 水 (C2-C3) / v3.

[0044] Where: θ 1、 θ 2、 θ3 is a conversion factor related to hardenability, D1, D2, and D3 are the target thicknesses of the rim metal that need to be cooled, and α 空 α 水 The heat transfer coefficient is given by v1, the air velocity of the first nozzle spraying air onto the wheel tread is given by v2, the water mist velocity of the second nozzle spraying water onto the wheel tread is given by v3, and the cooling water velocity of the third nozzle spraying water onto the wheel tread is given by v3. C0 is the initial temperature, and C1, C2, and C3 are the target temperatures that the wheel needs to reach for cooling.

[0045] Preferably, in step S2 above, the time for water quenching the wheel is 300s, wherein the time T1 for the first nozzle in the first nozzle area to spray air onto the wheel tread is 50s, for air cooling of the wheel; then the time T2 for the second nozzle in the second nozzle area to spray water mist onto the wheel tread is 80s, for the first water cooling of the wheel; finally, the time T3 for the third nozzle in the third nozzle area to spray cooling water onto the wheel tread is 170s, for the second water cooling of the wheel.

[0046] In step S1 above, the wheel is heated to 840-860°C, then kept at that temperature for 2.0-3.0 hours, and then the wheel is taken out of the furnace and quenched.

[0047] In step S3 above, the tempering temperature is set to 460-500℃, and then held at that temperature for 4 hours.

[0048] Example 1:

[0049] In this embodiment, wheel #1 is heat-treated according to the settings in Table 1.

[0050] In step S1, the wheel is heated to 840-860℃, held at that temperature for 2.5 hours, and then quenched after being taken out of the furnace.

[0051] In step S2, the tread surface quenching time is 300s (of which, the air cooling time is 50s, the atomization time is 80s, and the water cooling time is 170s);

[0052] In step S3, the tempering temperature is 480℃ and the holding time is 4h.

[0053] Mechanical performance tests were conducted on wheel #1, and the results are shown in Table 2. The tensile strength of the rim meets the standard requirements, the hardness gradient of the tread section is 12HB, the radial hardness range is 16HB, and the circumferential hardness range is 10HB.

[0054] Example 2:

[0055] In this embodiment, the No. 2 wheel is heat-treated according to the settings in Table 1.

[0056] In step S1, the wheel is heated to 840-860℃, held at that temperature for 2.5 hours, and then quenched after being taken out of the furnace.

[0057] In step S2, the tread surface quenching time is 300s (of which, the air cooling time is 60s, the atomization time is 70s, and the water cooling time is 160s);

[0058] In step S3, the tempering temperature is 480℃ and the holding time is 4h.

[0059] Mechanical performance tests were conducted on wheel #2, and the results are shown in Table 2. The tensile strength of the rim meets the standard requirements, the hardness gradient of the tread section is 10HB, the radial hardness range is 15HB, and the circumferential hardness range is 11HB.

[0060] Table 1 Heat treatment process parameters for the experimental wheels

[0061]

[0062] Table 2 Mechanical properties of the test wheel

[0063]

[0064] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method of heat treating a railway wheel, characterized in that, Including the following steps: S1. Heating the wheels; S2. Water quenching is performed on the wheels; S3. Temper the wheels; In step S2, a composite nozzle is used, which is provided with a first nozzle area, a second nozzle area and a third nozzle area in sequence. The first nozzle area is provided with a first nozzle for spraying air onto the wheel tread, the second nozzle area is provided with a second nozzle for spraying water mist onto the wheel tread, and the third nozzle area is provided with a third nozzle for spraying cooling water onto the wheel tread.

2. The method of heat treating a train wheel of claim 1, wherein, The water flow rate of the second nozzle is less than that of the third nozzle.

3. The method of heat treating a train wheel of claim 2, wherein, The water flow rate of the second nozzle is 3.0-4.9 L / min, and the water flow rate of the third nozzle is 15-20 L / min.

4. The method of heat treating a railroad wheel of any of claims 1 to 3, wherein, The air pressure of the first nozzle is 40-60 Pa.

5. The method of heat treating a railroad wheel of any of claims 1 to 3, wherein, The air outlet angle of the first nozzle is 90°.

6. The method of heat treating a railroad wheel of any one of claims 1 to 3, wherein The water outlet angles of the second nozzle and the third nozzle are 55° to 80°.

7. The method of heat treating a railroad wheel of any of claims 1 to 3, wherein, In step S2, six composite nozzles are used, the wheel is located on the quenching platform, and all composite nozzles are evenly distributed along the circumference of the quenching platform.

8. The method of heat treating a railroad wheel of any of claims 1 to 7, wherein, In step S1, the wheel is heated to 840-860°C and then kept at that temperature for 2.0-3.0 hours.

9. The heat treatment method for train wheels according to any one of claims 1 to 7, characterized in that, In step S2, the time for water quenching the wheel is 300 seconds.

10. The heat treatment method for train wheels according to any one of claims 1 to 7, characterized in that, In step S3, the tempering temperature is set to 460–500°C.

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