A heat treatment process applied to the guide pad of tilting-pad sliding bearing

Abstract

The application discloses a heat treatment process applied to a tilting-pad sliding bearing guide pad and belongs to the technical field of heat treatment, and the technical solution points are as follows: S1, cleaning the shielding tool and the pad, loading the pad into the shielding tool and then placing the shielding tool in an ion nitriding furnace, closing the furnace cover, vacuumizing and pressure-keeping leak detection; S2, after detection, low-flow N2+H2 is introduced into the ion nitriding furnace, low-voltage glow is started, and the trace oxide film on the surface of the pad is removed by ion sputtering; S3, temperature rising in the ion nitriding furnace, the temperature of the workpiece is raised, after reaching the set temperature, nitriding and heat preservation are carried out; S4, after the heat preservation is finished, the gas source and the glow power are closed, vacuum slow cooling is carried out to below 200 DEG C, and then high-purity nitrogen is filled to normal pressure; S5, the furnace cover of the ion nitriding furnace is opened, and the shielding tool and the pad are taken out. The application can carry out local nitriding on the guide pad, improve the hardness of the guide pad back support point area, thereby reducing the fretting wear of the guide pad back support point area, and improving the service life and reliability of the bearing.

Description

Technical Field

[0001] This application belongs to the field of heat treatment technology, and in particular relates to a heat treatment process for the guide pad of a tilting pad sliding bearing. Background Technology

[0002] Radial tilting pad bearings are mainly used in high-speed gearboxes, high-speed compressors, high-speed motors, steam turbines, generators, expanders, high-speed pumps, turbochargers, and aero engines. The tilting pads are installed in the inner bore of the bearing housing through limiting holes on the bearing end cap. The back of the tilting pad and the inner bore of the bearing housing typically make line or point contact, with the inner and outer cylinders forming a line. The radius of the back of the tilting pad is smaller than the radius of the inner bore of the bearing housing, allowing the tilting pad to swing freely during operation according to changes in speed, load, and bearing temperature. This creates a wedge-shaped gap, generates hydrodynamic oil film pressure, and enables the bearing to bear load.

[0003] Currently, the contact between the guide bearing back and the bearing body bore is mostly line and point, resulting in high contact stress. Coupled with alternating loads, fretting wear is prone to occur in the contact area of ​​the guide bearing back. To improve the service life and reliability of the bearing, it is necessary to increase the hardness of the support area of ​​the back of the bearing. Summary of the Invention

[0004] The purpose of this application is to address the aforementioned technical problems by providing a heat treatment process for the guide pads of tilting pad bearings. This process enables localized nitriding on the guide pads, increasing the hardness of the back support area of ​​the guide pads, thereby reducing fretting wear in the back support area of ​​the guide pads and improving the service life and reliability of the bearings.

[0005] This application provides a heat treatment process for the guide pad of a tilting pad sliding bearing, the specific steps of which include: S1. Clean the shielding fixture and tiles, put the tiles into the shielding fixture, place the shielding fixture in the ion nitriding furnace, close the furnace cover, evacuate to ≤8Pa and hold pressure to check for leaks. S2. After the pressure drop test is qualified, a low flow rate of N2+H2 is introduced into the ion nitriding furnace, and the low voltage is used to start the ignition. The trace oxide film on the surface of the tile is removed by ion sputtering. S3, the workpiece temperature is raised to 515℃-525℃ in the ion nitriding furnace. After reaching the set temperature, nitriding is carried out and the holding time is 8-10 hours. S4. After the heat preservation is completed, turn off the gas source and glow discharge power supply, vacuum cool slowly to below 200°C, and then fill with high-purity nitrogen to atmospheric pressure. S5, open the furnace cover of the ion nitriding furnace, take out the shielding fixture, and remove the tile from the shielding fixture.

[0006] After cleaning, the shielding fixture and the tile are assembled and placed in an ion nitriding furnace. The ion nitriding furnace performs localized nitriding on the outer arc surface of the tile. The shielding fixture covers the rest of the tile. After completing the above heat treatment process, a localized high-hardness area is formed on the outer arc surface of the tile, corresponding to the area where the tile and the bearing body abut against each other. This further improves the crush resistance and plastic indentation resistance of the tile at the fulcrum position. Moreover, localized nitriding can maintain the overall high toughness of the tile. When it encounters impact or instantaneous overload, the tile is less likely to develop micro-cracks, thus improving the service life of the tile.

[0007] Furthermore, the furnace heating in step S3 includes: In the first stage of heating, the temperature inside the furnace is slowly increased to 300℃ at a rate of 100-120℃ / h and held for 30 minutes. The second stage involves raising the temperature inside the furnace to 520°C, thus raising the temperature of the tiles to 520°C.

[0008] Furthermore, during the second stage of heating, when the tile temperature is greater than or equal to 515℃, the duty cycle is locked and the power is no longer increased. Then, the temperature of one side of the tile is detected every 30 minutes. When the temperature rise rate is >3℃ / 30min, the output duty cycle is slowly reduced by 1-2%. When the temperature rise rate is <1℃ / 30min, the duty cycle is increased by 1-2%. When the tile temperature is greater than or equal to 518℃ and the temperature rise rate is <2℃ / 30min, the PID closed loop is switched.

[0009] Furthermore, in step S2, H2:N2 = 3:1-4:1.

[0010] By adding a small amount of hydrogen, the oxide film on the workpiece surface is cleaned by ion sputtering, the surface is activated, and nitrogen diffusion is promoted.

[0011] Furthermore, the shielding fixture includes: The base assembly is provided with two support blocks, and each support block is provided with an abutment surface; The inner arc sleeve is placed between the two support blocks; An upper cover is placed on the upper side of the base assembly, and the upper cover is provided with an opening slot; A retaining sleeve assembly is placed on the upper cover and fits into the opening slot; Several temperature sensors are provided and mounted on the support block.

[0012] Furthermore, the support block includes: The insertion slot is located at the bottom of the side wall of the two support blocks that are close to each other; The connector is installed and connected to the support block by fasteners, and the connector is also installed and connected to the inner arc sleeve.

[0013] Furthermore, the retaining sleeve assembly includes: The first side guard corresponds to the side of the tile and is placed on the outer side of the upper cover; The first adjusting member is connected to the first side stop and is located on the inner side of the upper cover; The second side guard, corresponding to the outer arc surface of the tile, has an inclined surface and is placed on the inner side of the upper cover; The second adjusting member is connected to the second side stop and is located on the inner side of the upper cover; The first adjusting bolt is installed on the inner side of the upper cover and corresponds to the first adjusting component and the second adjusting component, respectively.

[0014] Furthermore, the base assembly includes: Support columns are placed at both ends of the support block and threadedly connected to the support block, and the support columns abut against the inner surface of the upper cover.

[0015] Furthermore, the inner arc sleeve includes: The heat exchange tube abuts against the inner arc sleeve, and the heat exchange tube is connected to a cold source.

[0016] The beneficial effects of this application are: 1. By using shielding fixtures and an ion nitriding furnace, the tile can be locally nitrided on the outer arc surface, thereby increasing the hardness of the area on the tile located at the fulcrum.

[0017] 2. The first and second stages of heating stabilize the temperature of the tiles in the ion nitriding furnace and prevent overheating.

[0018] 3. The non-nitrided area of ​​the tile is shielded by the shielding fixture. The base assembly is used to support the tile, with the outer arc surface of the tile facing upward. The inner arc sleeve improves the shielding effect on the inner arc surface of the tile. The upper cover can be opened to facilitate the placement and removal of the tile on the shielding fixture.

[0019] 4. The support columns and baffle assembly can be adjusted according to the size of the tile and the upward movement of the tile, thereby adjusting the range of the nitriding area. Attached Figure Description

[0020] Figure 1 This is a flowchart of the heat treatment process of this application; Figure 2 This is a schematic diagram of the shielding fixture of this application; Figure 3 This is a schematic diagram of the base assembly of this application; Figure 4 This is a schematic diagram of the structure of the upper cover of this application; Figure 5 This is a partial cross-sectional view of the upper cover of this application; In the attached figures, the following labels are used: 100, shielding fixture; 110, base assembly; 111, support block; 112, abutment surface; 113, insertion slot; 120, inner arc sleeve; 130, upper cover; 131, opening slot; 140, baffle assembly; 141, first side baffle; 142, second side baffle; 143, first adjusting component; 144, second adjusting component; 145, inclined surface; 146, first adjusting bolt; 200, temperature sensor; 300, insertion socket; 400, support column; 500, heat exchange tube. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0022] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0023] The embodiments of this application are described in detail below with reference to the accompanying drawings, through specific examples and application scenarios.

[0024] Example 1:

[0025] like Figure 1 As shown in the embodiment of this application, a heat treatment process for the guide pad of a tilting pad sliding bearing is provided, and the specific steps include: S1. Clean the shielding fixture 100 and the tile, put the tile into the shielding fixture 100, place the shielding fixture 100 in the ion nitriding furnace, close the furnace cover, evacuate to ≤8Pa and hold pressure to check for leaks. S2. After the pressure drop test is qualified, a low flow rate of N2+H2 is introduced into the ion nitriding furnace, and the low voltage is used to start the ignition. The trace oxide film on the surface of the tile is removed by ion sputtering. S3, the workpiece temperature is raised to 515℃-525℃ in the ion nitriding furnace. After reaching the set temperature, nitriding is carried out and the holding time is 8-10 hours. S4. After the heat preservation is completed, turn off the gas source and glow discharge power supply, vacuum cool slowly to below 200°C, and then fill with high-purity nitrogen to atmospheric pressure. S5, open the furnace cover of the ion nitriding furnace, take out the shielding fixture 100, and remove the tile from the shielding fixture 100.

[0026] Furthermore, the furnace heating in step S3 includes: In the first stage of heating, the temperature inside the furnace is slowly increased to 300℃ at a rate of 100-120℃ / h and held for 30 minutes. The second stage involves raising the temperature inside the furnace to 520°C, thus raising the temperature of the tiles to 520°C.

[0027] Furthermore, during the second stage of heating, when the tile temperature is greater than or equal to 515℃, the duty cycle is locked and the power is no longer increased. Then, the temperature of one side of the tile is detected every 30 minutes. When the temperature rise rate is >3℃ / 30min, the output duty cycle is slowly reduced by 1-2%. When the temperature rise rate is <1℃ / 30min, the duty cycle is increased by 1-2%. When the tile temperature is greater than or equal to 518℃ and the temperature rise rate is <2℃ / 30min, the PID closed loop is switched.

[0028] Furthermore, in step S2, H2:N2 = 3:1-4:1.

[0029] After cleaning, the shielding fixture 100 and the tile are assembled and placed into an ion nitriding furnace. The ion nitriding furnace performs localized nitriding on the outer arc surface of the tile. The shielding fixture 100 shields the rest of the tile. After completing the above heat treatment process, a localized high-hardness area is formed on the outer arc surface of the tile, corresponding to the area where the tile and the bearing body abut against each other. This further improves the crush resistance and plastic indentation resistance of the tile at the fulcrum position. Localized nitriding can also maintain the overall high toughness of the tile. When encountering impact or instantaneous overload, the tile is less likely to develop micro-cracks, thus improving the service life of the tile.

[0030] During the nitriding and tempering heat treatment process, the temperature inside the ion nitriding furnace is divided into two stages: a first stage of heating and a second stage of heating. This ensures that the temperature of the tiles rises evenly and stably, preventing excessive temperature differences and avoiding thermal stress distortion. At the same time, it can control the stable temperature rise of the tiles to 520℃, preventing overheating and maintaining the quality of the tiles.

[0031] Using the above method, the control temperature of the tile is set to 520℃. When the tile temperature rises to close to 520℃, it is fine-tuned to make the tile temperature regulation more stable. Through PID closed-loop control, the tile temperature can be kept at 520℃ with stable small fluctuations, further improving the stability of the tile temperature.

[0032] By adding a small amount of hydrogen, the oxide film on the workpiece surface is cleaned by ion sputtering, the surface is activated, and nitrogen diffusion is promoted.

[0033] Example 2:

[0034] like Figure 2 , Figure 3 , Figure 4 As shown, this application embodiment provides a heat treatment process for the guide pad of a tilting pad sliding bearing. In addition to the above-mentioned technical features, the shielding fixture 100 further includes: The base assembly 110 is provided with two support blocks 111, and each support block 111 is provided with an abutment surface 112. The inner arc sleeve 120 is placed between the two support blocks 111; The upper cover 130 is placed on the upper side of the base assembly 110, and the upper cover 130 is provided with an opening slot 131; A retainer assembly 140 is placed on the upper cover 130 and is adapted to the opening slot 131; Temperature sensors 200 are provided in several units and are mounted on support block 111.

[0035] The base assembly 110 consists of two support blocks 111 for bearing the weight of the tile. The tile's arc length is typically 60°, and the contact surfaces 112 of the two support blocks 111 are at a 60° angle to each other, allowing them to support the tile. The support blocks 111 allow the outer arc surface of the tile to face upwards, and the inner arc sleeve 120 is fitted onto the inner arc surface of the tile to shield it. The upper cover 130 covers the tile and support blocks 111 from the upper side of the base assembly 110, exposing the back of the tile through the opening slot 131. Nitriding is performed on the tile, and the gap between the opening groove 131 and the tile is further controlled by the sleeve assembly 140, which improves the shielding stability of the upper cover 130. Temperature sensors 200 are installed on the support blocks 111 of the base assembly 110 by bolts and other fasteners. The temperature sensors 200 are used to detect the temperature of the tile, which further improves the temperature detection accuracy of the tile. The above structure allows the outer arc surface of the tile to face upward and only expose part of it for nitriding, thereby improving the hardness of the support area on the back of the tile.

[0036] The shielding fixture 100 is made entirely of 304 stainless steel. The inner arc sleeve 120 and the upper cover 130 are made of sheet metal, and their dimensions are mainly determined according to the size of the tile.

[0037] Furthermore, the support block 111 includes: The insertion slot 113 is located at the bottom of the side wall of the two support blocks 111 that are close to each other; The plug-in socket 300 is connected to the support block 111 by fasteners, and the plug-in socket 300 is also connected to the inner arc sleeve 120.

[0038] The insertion slot 113 is placed on the support block 111. After the insertion seat 300 mates with the insertion slot 113, it is connected by fasteners, thereby connecting the insertion seat 300 and the support block 111 and improving the structural stability of the base assembly 110. The insertion seat 300 has an inner groove on its lower side, which can be used to install the insertion seat 300 and fasteners such as bolts. The insertion depth of the insertion seat 300 into the insertion slot 113 varies, which allows the base assembly 110 to be adjusted for different tiles. The distance between the two support blocks 111 is determined by the inner arc sleeve 120, which is clamped between the two support blocks 111. The inner arc sleeve 120 is connected to the insertion seat 300 by fasteners such as bolts. The base assembly 110 is made of solid stainless steel, which facilitates stable support of the tiles. Moreover, the adjustment between the support blocks 111 can accommodate more tile sizes, improve the utilization rate of the base assembly 110, and further reduce production costs.

[0039] Example 3:

[0040] like Figure 4 , Figure 5 As shown, this application embodiment provides a heat treatment process for the guide pad of a tilting pad sliding bearing. In addition to the above-mentioned technical features, the retaining sleeve assembly 140 further includes: The first side guard 141 corresponds to the side of the tile and is placed on the outer side of the upper cover 130. The first adjusting member 143 is connected to the first side stop 141, and the first adjusting member 143 is located on the inner side of the upper cover 130. The second side baffle 142 corresponds to the outer arc surface of the tile. The second side baffle 142 is provided with a slope 145 and is placed on the inner side of the upper cover 130. The second adjusting member 144 is connected to the second side stop 142, and the second adjusting member 144 is located on the inner side of the upper cover 130; The first adjusting bolt 146 is installed on the inner side of the upper cover 130 and corresponds to the first adjusting member 143 and the second adjusting member 144 respectively.

[0041] The first side block 141 is welded or integrally connected to the first adjusting member 143, and the second side block 142 is welded or integrally connected to the second adjusting member 144. The first side block 141 and the second side block 142 are placed on the upper cover 130, and the first adjusting member 143 and the second adjusting member 144 are moved on the corresponding first adjusting bolt 146. When the first side block 141 and the second side block 142 are adjusted to the required position, the corresponding first adjusting member 143 or the second adjusting member 144 is clamped and fixed by two nuts installed on the same first adjusting bolt 146, which further improves the installation structure stability of the sleeve assembly 140 and improves the shielding effect on the shielding area of ​​the tile. The second side block 142 can be adapted to the outer arc surface of the tile through the inclined surface 145.

[0042] Example 4:

[0043] like Figure 2 , Figure 3 As shown, this application embodiment provides a heat treatment process for the guide pad of a tilting pad sliding bearing. In addition to the above-mentioned technical features, the base assembly 110 further includes: Support columns 400 are placed at both ends of support blocks 111 and are threadedly connected to support blocks 111. The support columns 400 abut against the inner side of the upper cover 130.

[0044] The support column 400 has a threaded portion that is threadedly connected to the support block 111. The support column 400 can be adjusted. When the upper cover 130 is placed on the base assembly 110, the support column 400 abuts against the upper cover 130, allowing the upper cover 130 to be placed on the base assembly 110. By adjusting the support column 400 and the retaining sleeve assembly 140, the range of the nitriding area of ​​the tile can be adjusted.

[0045] Example 5:

[0046] like Figure 2 , Figure 3 As shown, this application embodiment provides a heat treatment process for the guide shell of a tilting pad sliding bearing. In addition to the above-mentioned technical features, the inner arc sleeve 120 further includes: The heat exchange tube 500 abuts against the inner arc sleeve 120, and the heat exchange tube 500 is connected to a cold source.

[0047] The heat exchange tube 500 abuts against the lower side of the inner arc sleeve 120 and is connected by welding or bolts or other fasteners. The heat exchange tube 500 is connected to a cold source, such as air, water or oil. The heat exchange tube 500 exchanges heat to keep the inner arc surface of the guide tile at a temperature below 240°C. When the inner arc surface of the guide tile is not yet covered with bearing alloy, the heat exchange tube 500 reduces the temperature of the inner arc surface of the guide tile, so that the inner arc surface of the guide tile is less affected by nitriding. When the inner arc surface of the guide tile is covered with bearing alloy, the melting point of the bearing alloy is 240-370°C. The heat exchange tube 500 can prevent the bearing alloy on the inner arc surface of the guide tile from melting.

[0048] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0049] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A heat treatment process for the guide pad of a tilting pad sliding bearing, characterized in that, The specific steps include: S1, clean the shielding fixture (100) and the tile, put the tile into the shielding fixture (100), place the shielding fixture (100) in the ion nitriding furnace, close the furnace cover, evacuate to ≤8Pa and pressurize to check for leaks; S2. After the pressure drop test is qualified, a low flow rate of N2+H2 is introduced into the ion nitriding furnace, and the low voltage is used to start the ignition. The trace oxide film on the surface of the tile is removed by ion sputtering. S3, the workpiece temperature is raised to 515℃-525℃ in the ion nitriding furnace. After reaching the set temperature, nitriding is carried out and the holding time is 8-10 hours. S4. After the heat preservation is completed, turn off the gas source and glow discharge power supply, vacuum cool slowly to below 200°C, and then fill with high-purity nitrogen to atmospheric pressure. S5, open the furnace cover of the ion nitriding furnace, take out the shielding fixture (100), and remove the tile from the shielding fixture (100).

2. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 1, characterized in that, The furnace heating in step S3 includes: In the first stage of heating, the temperature inside the furnace is slowly increased to 300℃ at a rate of 100-120℃ / h and held for 30 minutes. The second stage involves raising the temperature inside the furnace to 520°C, thus raising the temperature of the tiles to 520°C.

3. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 2, characterized in that, In the second stage of heating, when the tile temperature is greater than or equal to 515℃, the duty cycle is locked and the power is no longer increased. Then, the temperature of one side of the tile is detected every 30 minutes. When the temperature rise rate is >3℃ / 30min, the output duty cycle is slowly reduced by 1-2%. When the temperature rise rate is <1℃ / 30min, the duty cycle is increased by 1-2%. When the tile temperature is greater than or equal to 518℃ and the temperature rise rate is <2℃ / 30min, the PID closed loop is switched.

4. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 3, characterized in that, In step S2, H2:N2 = 3:1-4:

1.

5. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 1, characterized in that, The shielding fixture (100) includes: The base assembly (110) is provided with two support blocks (111), and the support blocks (111) are provided with abutment surfaces (112). The inner arc sleeve (120) is placed between the two support blocks (111); The upper cover (130) is placed on the upper side of the base assembly (110), and the upper cover (130) is provided with an opening slot (131). A retainer assembly (140) is placed on the upper cover (130) and adapted to the opening slot (131); Temperature sensors (200) are provided in several units and mounted on a support block (111).

6. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 5, characterized in that, The support block (111) includes: The insertion slot (113) is located at the bottom of the side wall of the two support blocks (111) that are close to each other; The plug-in socket (300) is connected to the support block (111) by fasteners and is also connected to the inner arc sleeve (120).

7. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 5, characterized in that, The retaining sleeve assembly (140) includes: The first side guard (141) corresponds to the side of the tile and is placed on the outer side of the upper cover (130); The first adjusting member (143) is connected to the first side stop (141), and the first adjusting member (143) is placed on the inner side of the upper cover (130); The second side guard (142) corresponds to the outer arc surface of the tile. The second side guard (142) is provided with a slope (145) and is placed on the inner side of the upper cover (130). The second adjusting member (144) is connected to the second side stop (142), and the second adjusting member (144) is located on the inner side of the upper cover (130); The first adjusting bolt (146) is installed on the inner side of the upper cover (130) and corresponds to the first adjusting member (143) and the second adjusting member (144) respectively.

8. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 5, characterized in that, The base assembly (110) includes: The support column (400) is placed at both ends of the support block (111) and threadedly connected to the support block (111). The support column (400) abuts against the inner side of the upper cover (130).

9. The heat treatment process for the guide pad of a tilting pad sliding bearing according to claim 5, characterized in that, The inner arc sleeve (120) includes: The heat exchange tube (500) abuts against the inner arc sleeve (120), and the heat exchange tube (500) is connected to a cold source.

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