Method for improving abrasion resistance of impact type rotating wheel

Abstract

The invention discloses a method for improving the abrasion resistance of an impact type rotating wheel, and relates to the technical field of production and manufacturing of impact type rotating wheels. Comprising the following steps: S1, milling an easy-to-abrade area on the impact type rotating wheel to form a filling area; s2, high-strength abrasion-resistant martensitic stainless steel is used as a filling material to be filled in the filling area, and laser cladding is carried out; s3, the laser cladding position is machined to be consistent with the molded line of the impact type rotating wheel; s4, the machined rotating wheel is subjected to aging treatment at the temperature lower than the austenite transformation initial temperature (Ac1); and S5, the surface of the impact type rotating wheel subjected to aging treatment is polished to be smooth. The surface strength, hardness and abrasion resistance of the impact type rotating wheel can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of production and manufacturing of impact wheels, in particular to a method for improving the abrasion resistance of impact wheels. Background Art

[0002] The impact runner is subjected to the cyclic impact of high-speed water flow during operation, and wear and cavitation are the two main material loss mechanisms. Due to the large kinetic energy and impact force of the impact runner, the surface of the runner usually produces wear lines along the direction of the water flow during service, especially for runners serving in waters with heavy sediment content, the wear of the flow surface is more serious. In addition to wear, cavitation is also the main form of failure of the impact runner profile. When the water flows through different areas of the flow surface, its fluid pressure will change significantly. When the high-pressure water flows through the flow surface area with low pressure, a cavitation effect is generated, forming a large number of bubbles in the water flow. When it flows through the high-pressure area again, the bubbles are annihilated, and a local high-pressure jet is generated to impact the runner flow surface. Under the repeated impact of the high-pressure jet water, the surface of the runner will be fatigued and form honeycomb-shaped cavitation pits. Usually, the wear and cavitation of the impact runner are carried out simultaneously, and the surface abrasion speed of the runner is accelerated sharply under the superposition of the two mechanisms. When the impact wheel surface is severely abraded, it will affect the force of the water flow, and thus affect the mechanical stability of the generator set; when the wheel abrasion is too severe, it may even threaten the safety of the wheel structure, thus creating a safety hazard.

[0003] At present, as the design capacity of single-unit impulse hydropower units continues to increase, the impact load on the impulse runner during service is also increasing. Correspondingly, the wear and cavitation problems of the impulse runner are becoming more and more serious. Nowadays, if martensitic stainless steel is still used to manufacture the impulse runner, it can no longer meet the wear resistance requirements of large-capacity units during service.

[0004] Therefore, it is necessary to design a solution to improve the wear resistance of the impact wheel. Summary of the invention

[0005] The purpose of the present invention is to provide a method for improving the wear resistance of an impact wheel in view of the above-mentioned problems, which can effectively improve the surface strength, hardness and wear resistance of the impact wheel.

[0006] The technical solution adopted by the present invention is as follows: A method for improving the abrasion resistance of an impact wheel comprises the following steps:

[0007] S1: Milling the easily abrasive area on the impact wheel to form a filling area;

[0008] S2: high-strength and wear-resistant martensitic stainless steel is used as the filling material in the filling area and laser cladding is performed;

[0009] S3: Process the laser cladding position to be consistent with the profile of the impact wheel;

[0010] S4: performing aging treatment on the processed wheel at a temperature lower than the initial temperature of austenite transformation (Ac1);

[0011] S5: Grind the aged impact wheel surface until it is smooth.

[0012] Furthermore, in step S1 , it is necessary to determine the easily abraded area on the impact wheel.

[0013] Furthermore, when determining the easily eroded area, the easily eroded area on the model is theoretically calculated based on the model of the impact wheel, and the easily eroded area is marked on the impact wheel entity according to the location of the easily eroded area on the model.

[0014] Furthermore, the number of the easily-eroded regions is four.

[0015] Further, in step S2, the composition of the high-strength and wear-resistant martensitic stainless steel includes the following elements in percentage by mass:

[0016] C (0-0.03%); Cr (11.5%-14.0%); Ni (7.5%-9.5%); Cu (1.0%-2.5%); Nb (0.3%-0.6%); Ti (0.5%-1.4%); Mo (0.1%-0.3%); Mn (0.1%-0.3%); Si (0.1%-0.3%); Al (0.1%-0.3%); P (0-0.04%); S (0-0.03%); O (0-0.04%); N (0-0.04%); the rest are Fe and unavoidable impurity elements.

[0017] Furthermore, in step S2, the power of laser cladding is 15000W.

[0018] Further, in step S2, the laser cladding rate is 600 mm / min.

[0019] Furthermore, in step S2, the overlap rate of laser cladding is 50%.

[0020] Further, in step S4, the aging treatment temperature is 460°C to 520°C, the aging time is 3h to 4h, and the cooling method is air cooling.

[0021] Further, in step S5, during grinding, the surface of the impact wheel is deemed to be smooth after reaching the designed roughness.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. By laser cladding the wear-resistant alloy material in the abrasion-prone area of ​​the wheel, and by aging treatment, the surface laser cladding layer is precipitated with dispersed nano-precipitation phase (Al2Cu and Ni3Al), which can significantly increase the surface strength, hardness and wear resistance of the impact wheel, thereby making the impact wheel meet the wear resistance performance requirements;

[0024] 2. Strengthening alloy elements such as Ti and Nb are added to the wear-resistant alloy powder of the present invention, thereby improving the hardness and wear resistance of the material; in addition, the elements such as Cu, Al, Ni, etc. contained are easy to form a nanoparticle reinforcement phase, thereby further improving the strength and surface wear resistance of the component. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0026] Figure 1 This is the distribution diagram of the wear-prone area of ​​the flow surface of the impact wheel;

[0027] Figure 2 The size and schematic diagram of the erosion test sample;

[0028] Figure 3 This is the process diagram of the erosion experiment (45° angle erosion);

[0029] Figure 4 This is a diagram of the erosion experiment process (90° angle erosion). DETAILED DESCRIPTION

[0030] In the description of this specification, it should be noted that if the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of this specification is usually placed when used. It is only for the convenience of describing this specification and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this specification.

[0031] In addition, if the terms "horizontal" or "vertical" appear in the description of this specification, it does not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of this specification, it should also be noted that, unless otherwise clearly stipulated and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be a connection between the internal parts of two elements.

[0033] A method for improving the abrasion resistance of an impact wheel comprises the following steps:

[0034] S1: According to the model of the impact wheel, the easily abraded area on the model is theoretically calculated, and according to the location of the easily abraded area on the model, the easily abraded area is marked on the impact wheel entity to complete the determination of the easily abraded area on the impact wheel; the easily abraded area on the impact wheel is milled to form a filling area.

[0035] It should be noted that the number of easily eroded areas is 4. The morphology and position distribution of the easily eroded areas of the impact wheel are shown in Figure 1 As shown, the details are as follows:

[0036] (1) The water fountain notch and water cutting edge area is characterized by wear at the notch;

[0037] (2) The water-cutting edge area is characterized by inward-directed wave-like erosion;

[0038] (3) The area near the water outlet at the root of the water bucket is characterized by directional pitting, raindrop erosion and cavitation;

[0039] (4) The upper part of the water bucket, near the water outlet, is characterized by scaly erosion that matches the flow direction.

[0040] S2: High-strength and wear-resistant martensitic stainless steel is used as the filling material to fill the four filling areas and perform laser cladding; the laser cladding power is 15000W, the speed is 600mm / min, and the overlap rate is 50%; and wherein:

[0041] The composition of high-strength and wear-resistant martensitic stainless steel includes the following elements in mass percentage:

[0042] C (0-0.03%); Cr (11.5%-14.0%); Ni (7.5%-9.5%); Cu (1.0%-2.5%); Nb (0.3%-0.6%); Ti (0.5%-1.4%); Mo (0.1%-0.3%); Mn (0.1%-0.3%); Si (0.1%-0.3%); Al (0.1%-0.3%); P (0-0.04%); S (0-0.03%); O (0-0.04%); N (0-0.04%); the rest are Fe and unavoidable impurity elements; preferably, C: 0.02%; Cr: 12.5%; Ni: 8.6%; Cu: 1.5%; Nb: 0.5%; Ti i: 0.8%; Mo: 0.23%; Mn: 0.24%; Si: 0.27%; Al: 0.15%; P: 0.009%; S: 0.005%; O: 0.023%; N: 0.007%, of which P, S, N are impurity elements and the rest is Fe.

[0043] S3: Process the laser cladding position to be consistent with the profile of the impact wheel.

[0044] S4: performing aging treatment on the processed wheel at a temperature lower than the initial austenite transformation temperature (Ac1); the aging treatment temperature is 460°C to 520°C, the aging time is 3h to 4h, and the cooling method is air cooling; the preferred aging treatment temperature is 480°C and the holding time is 4h.

[0045] S5: The impact wheel surface after aging treatment is polished until it is smooth. During polishing, the impact wheel surface is considered smooth when it reaches the designed roughness.

[0046] In this embodiment, a flat plate component is used for laser cladding, aging treatment and wear resistance test; the flat plate component after laser cladding and aging treatment is machined and polished to prepare an erosion test sample. The schematic diagram of the erosion test sample size is shown in FIG. Figure 2 As shown; and the erosion test samples were subjected to erosion test.

[0047] Specifically, the thickness of the cladding layer formed by laser cladding is 2.5 mm. In order to compare the wear resistance of the conventional runner material that has not been subjected to laser cladding and aging treatment, according to Figure 2The same impact patterns were prepared with the same sample size, one type was the sample after laser cladding and aging treatment, and the other type was the substrate without laser cladding and aging treatment. The erosion test equipment used was the equipment developed by the Institute of Metal Research, Chinese Academy of Sciences. The erosion test relies on the high-speed scouring of sand-containing water flow, so it involves important parameters such as sand content, sand hardness, sand particle size, water flow velocity, and scouring angle. According to the actual working conditions of the impact wheel, 400-mesh quartz sand (about 38 microns) was selected for the sediment of the sand-containing water flow in the experiment; the water flow velocity on the scouring surface was 65.5m / s, and the scouring angle was based on the difference in impact angles at different positions on the flow surface of the impact wheel. Two groups of typical scouring angles of 45° and 90° were selected (such as Figure 3 and Figure 4 The erosion time of each sample was 8 hours.

[0048] The commonly used method in the industry to characterize the anti-abrasion properties of the sample is the weighing method, that is, the sample is ultrasonically cleaned and blown dry before the test, and the mass is recorded. After the test is completed, the sample is cleaned and blown dry, and weighed again. The relative wear resistance of the sample is described by the mass difference before and after the test. The erosion and wear test results of the sample after laser cladding and aging treatment and the substrate without laser cladding and aging treatment are shown in Tables 1 and 2.

[0049] Table 1 Erosion test results of samples after laser cladding and aging treatment

[0050]

[0051] Table 2 Erosion test results of substrate samples

[0052]

[0053] It can be seen from Table 1 and Table 2 that the erosion resistance test results at 45° and 90° show that the wear resistance of the samples after laser cladding and aging treatment is 1.32 times and 1.91 times that of the substrate, and the erosion resistance of the cladding layer is higher than that of the substrate without laser cladding and aging treatment, indicating that the "ploughing" and "micro-cutting" behaviors of the impact particles have a more significant effect on the low hardness substrate; at an attack angle of 90°, the wear resistance of the cladding layer and the substrate is more different, because there is no speed and force component during 90° erosion, so the high hardness and super wear resistance of the cladding layer can be better utilized.

[0054] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for improving the abrasion resistance of an impact wheel, characterized in that: The following steps are involved: S1: Milling the easily abrasive area on the impact wheel to form a filling area; S2: high-strength and wear-resistant martensitic stainless steel is used as the filling material in the filling area and laser cladding is performed; S3: Process the laser cladding position to be consistent with the profile of the impact wheel; S4: performing aging treatment on the processed wheel at a temperature lower than the initial temperature of austenite transformation (Ac1); S5: Grind the aged impact wheel surface until it is smooth.

2. The method according to claim 1, characterized in that: In step S1, it is necessary to determine the easily eroded area on the impact wheel.

3. The method according to claim 2, characterized in that: When determining the easily abraded area, the easily abraded area on the model is theoretically calculated based on the model of the impact wheel, and the easily abraded area is marked on the impact wheel entity according to the location of the easily abraded area on the model.

4. The method according to claim 3, characterized in that: The number of easily eroded areas is four.

5. The method according to claim 1, characterized in that: In step S2, the composition of the high-strength and wear-resistant martensitic stainless steel includes the following elements in mass percentage: C (0-0.03%); Cr (11.5%-14.0%); Ni (7.5%-9.5%); Cu (1.0%-2.5%); Nb (0.3%-0.6%); Ti (0.5%-1.4%); Mo (0.1%-0.3%); Mn (0.1%-0.3%); Si (0.1%-0.3%); Al (0.1%-0.3%); P (0-0.04%); S (0-0.03%); O (0-0.04%); N (0-0.04%); the rest are Fe and unavoidable impurity elements.

6. The method according to claim 1, characterized in that: In step S2, the power of laser cladding is 15000W.

7. The method according to claim 1, characterized in that: In step S2, the laser cladding rate is 600 mm / min.

8. The method according to claim 1, characterized in that: In step S2, the overlap rate of laser cladding is 50%.

9. The method according to claim 1, characterized in that: In step S4, the aging treatment temperature is 460°C to 520°C, the aging time is 3h to 4h, and the cooling method is air cooling.

10. The method according to claim 1, characterized in that: In step S5, during grinding, the surface of the impact wheel is deemed smooth after reaching the designed roughness.

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