A spinning process for producing seamless steel tubes for bearing rings

Abstract

The application discloses a spinning process for producing seamless steel pipes for high-performance bearing rings, and comprises the following steps: design of a deformation tool and determination of deformation parameters, machining, installation, debugging and adjustment of the deformation tool and adjustment of the deformation parameters, and heating and rolling forming; compared with the prior art, the application adopts a torsion deformation device to twist the blank before rolling, so that the circumferential deformation of the blank during the rolling process is enhanced, and the organization grain is refined; meanwhile, the two rollers are set to rotate reversely during the rolling process, so that the processing of the seamless steel pipe is completed, the carbide in the seamless steel pipe is refined and uniformly distributed, and the production process is convenient to operate and control.

Description

Technical Field

[0001] This invention relates to the field of steel pipe manufacturing technology, specifically to a rotary rolling process for producing seamless steel pipes for bearing rings. Background Technology

[0002] Bearing rings are ring-shaped parts of radial rolling bearings with one or more raceways. Common high-performance bearings include wind power bearings, aerospace bearings, and mechanical bearings. These are all special bearings that are used in harsh environments, have high maintenance costs, require long service life, and some of them operate under ultra-high speed, high load, high temperature and other harsh conditions for a long time.

[0003] The bearing rings used in the aforementioned high-performance bearings have high requirements for their performance and structure. Traditional manufacturing technologies for bearing rings include forging and skew rolling piercing. The forging process involves: blanking—box furnace heating—upsetting—punching—expanding—pre-rolling—final rolling. Due to its inherent characteristics, this process limits the size of the blank produced per batch; punching is required during the process, resulting in low material utilization; and the numerous process steps lead to low production efficiency and high costs. The conventional skew rolling piercing process involves: box furnace heating—skew rolling piercing—blanking—final rolling. While it offers higher material utilization and production efficiency than forging, the limitations imposed by the roll shape on process parameters (feed angle β and rolling angle γ) do not significantly improve material performance, thus failing to meet the requirements of the aforementioned high-performance bearings in use.

[0004] Currently used high-performance bearing rings are generally manufactured from high-performance seamless steel tubes. These high-performance seamless steel tubes are currently manufactured using longitudinal rolling. For example, patent application CN202010260435.5 describes a method for producing rare-earth bearing seamless steel tubes using a Φ200mm round tube blank, including:

[0005] The billet is heated once, the seamless steel pipe is hot-rolled continuously, and the rolling process is rapid cooling.

[0006] in:

[0007] The total heating time for a single heating of the steel billet is ≥5.5 hours. The temperature of the preheating section is controlled at ≤800℃, the temperature of the heating section is 1100~1200℃, and the temperature of the soaking section is 1120~1150℃. The temperature is increased slowly during steelmaking to ensure uniform heating of the steel billet and reduce temperature difference. The temperature difference of the same steel billet should not exceed 50℃, but the heating time must be guaranteed. The air volume in the furnace should not be too large to maintain a slightly reducing flame.

[0008] During the billet rolling process, ensure a smooth surface without sharp edges to avoid scratches and dents on the rolled surface. Rolling must be done at a uniform speed, and the cooling water for the rolls must be controlled. Directly pouring cooling water onto the rolled workpiece is strictly prohibited. Bending billets cannot be straightened using a straightening machine. For hot continuous rolling of seamless steel pipes, the piercing speed is 400–450 rpm, the bite speed is 45–50%, and the piercing angle is 9.5–10.5°. The actual temperature of the steel pipe after sizing should be ≥800℃. Rapid cooling is required after rolling. To prevent the formation of network carbides during air cooling of the rolled steel pipe, the pipe is cooled to 700℃ at a rate of 8℃–13℃ / s after sizing and then slowly cooled in close rows on a cooling bed.

[0009] As is well known, microstructure determines performance, and the process of microstructure regulation mainly depends on deformation and subsequent heat treatment. Some non-tuned steels rely solely on deformation, and their microstructure is inherited. Therefore, obtaining the desired microstructure requires a reasonable deformation process. However, the seamless steel pipes in the aforementioned patent application are basically subjected to two-dimensional deformation during manufacturing, which has limited effect on the crushing and homogenization of carbides. Existing research results indicate that the more numerous, larger, and more unevenly distributed the carbides, the lower the fatigue life of the seamless steel pipe, resulting in a relatively low fatigue life for bearing rings processed from seamless steel pipes. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of this invention is to provide a spinning process for producing high-performance seamless steel tubes for bearing rings, so as to solve the problem that the large size and uneven distribution of carbides in the prepared seamless steel tubes lead to the low fatigue life of the seamless steel tubes.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a spinning process for producing seamless steel tubes for high-performance bearing rings, comprising the following steps:

[0012] The first step is the design of the deformation tool and the determination of its deformation parameters:

[0013] Finite element simulation was used to establish a finite element model of the seamless steel pipe rolling process, and the convergence condition was set as follows: the torsion angle at any point in the deformation zone is not less than 50°.

[0014] Determine the roll cone angle α, feed angle β, rolling angle γ, roll gap, and roll speed; if the torsion angle of the billet meets the convergence condition given the shape of the deformation tool and the deformation parameters, proceed to the next step; if not, repeat the previous steps until the forming condition is met.

[0015] The second step is the processing, installation, and debugging of the deformation tools;

[0016] Based on the conditions input in the first step when the convergence condition is met, design deformation tools and rolling angle and feed angle adjustment fixtures, and then complete the processing, installation and debugging of the rolls, rolling angle and feed angle adjustment fixtures;

[0017] The third step is to adjust the deformation parameters:

[0018] After the deformation tool is installed and debugged, adjust the feed angle β, rolling angle γ, roll gap and roll speed according to the optimal process parameters obtained in the first step.

[0019] Step 4: Heating and rolling to form the shape:

[0020] The heated billet is transferred from the heating furnace to the feed chute of the rolling mill within 10 seconds. The billet is twisted before rolling using a torsion deformation device in the feed chute. The billet after torsion deformation is then sent to the deformation zone between two rotating rolls in the same direction. The billet undergoes a forward spiral motion in the deformation zone until the deformation is completed. The billet completely leaves the deformation zone and the rolled tube is air-cooled to room temperature before isothermal annealing is completed.

[0021] Technical principle: Before the billet enters the rolling zone, a torsion deformation device is used to pre-twist the billet. Then, when the billet enters the rolling zone, the Mannesmann effect is used to achieve continuous local pressure-torsion composite deformation, so that the solid bar can be directly formed into a hollow tube without drilling. This achieves the effect of large deformation under small load, and the carbides in the hollow tube are uniformly and finely dispersed.

[0022] Furthermore, in the fourth step, the pre-rolling torsion angle is not less than 55°, the feed angle β is greater than 12°, the rolling angle γ is greater than 15°, the roll surface cone angle α is in the range of 2°-6°, and the roll speed is not less than 30 r / min.

[0023] Furthermore, the torsional deformation device in the fourth step includes torsional deformation components arranged at both ends along the conveying direction within the guide trough. Each torsional deformation component includes a worm gear reduction structure for inputting rotational power and a torsional gear driven to rotate by the worm gear reduction structure. A blank placement hole for inserting a blank is opened at the center of the torsional gear, and a blank fixing component is fitted on the torsional gear to fix the blank inserted into the blank placement hole. In use, the torsional gears in the two torsional deformation components rotate in opposite directions.

[0024] Furthermore, the billet fixing assembly includes multiple telescopic clamping structures fixedly mounted on the torsion gear, and the multiple telescopic clamping structures are arranged circumferentially on the outer side of the discharge end of the billet placement hole.

[0025] Furthermore, each of the telescopic clamping structures includes a blank fixing shaft and a connector that are slidably arranged on the torsion gear in its radial direction. One end of the blank fixing shaft is located on the discharge end side of the blank placement hole, and the other end is connected to the connector by a telescopic spring. A cam is also rotatably arranged on the torsion gear. The cam is located on the side of the connector to intermittently slide against the connector so that the connector intermittently moves toward the blank fixing shaft.

[0026] Furthermore, a guide ring is fixedly provided on the torsion gear. The guide ring is located outside the discharge end of the blank placement hole and is coaxially arranged with the blank placement hole. Multiple guide holes are opened on the side wall of the guide ring in a ring arrangement. The clamping ends of the blank fixing shafts in the multiple telescopic clamping structures pass through the multiple guide holes one by one.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] After optimizing parameters such as the roll cone angle α, feed angle β, rolling angle γ, roll gap, and roll speed, the forming conditions are met to enable efficient rolling. Before rolling, a torsion deformation device is used to torsion the billet to enhance the circumferential deformation of the billet during the rolling process, which promotes finer grain structure. At the same time, during the rolling process, two pre-set rolls rotate in the same direction to complete the processing of seamless steel pipes, which refines and evenly distributes the carbides in the seamless steel pipes. This production process is also easy to operate and control. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the rolling process of a roll according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of a torsional deformation component in one embodiment of the present invention;

[0032] Figure 4 for Figure 3 A schematic diagram of the telescopic clamping structure;

[0033] Figure 5 This is a diagram of the original microstructure of the billet in Example 1;

[0034] Figure 6 This is a diagram of the original carbides of the billet in Example 1;

[0035] Figure 7 This is a microstructure diagram of the seamless steel pipe after rolling in Example 1;

[0036] Figure 8 This is a carbide diagram of the seamless steel pipe after rolling in Example 1.

[0037] The reference numerals in the accompanying drawings include: 1. Roller; 2. Guide plate; 3. Top head; 4. Billet; 5. Worm gear; 6. Torsion gear; 7. Guide ring; 8. Billet placement hole; 9. Telescopic clamping structure; 10. Billet fixing shaft; 101. Connector; 102. Telescopic spring; 103. Cam; 104. Detailed Implementation

[0038] The present invention will be further described in detail below through specific embodiments:

[0039] A spinning process for producing seamless steel tubes for high-performance bearing rings includes the following steps:

[0040] The first step is the design of the deformation tool and the determination of its deformation parameters:

[0041] Finite element simulation was used to establish a finite element model of the seamless steel pipe rolling process, and the convergence condition was set as follows: the torsion angle at any point in the deformation zone is not less than 50°.

[0042] Determine the roll cone angle α, feed angle β, rolling angle γ, roll gap, and roll speed; if the torsion angle of the billet 4 meets the convergence condition after determining the shape of the deformation tool and the deformation parameters, proceed to the next step; if not, repeat the previous steps until the forming condition is met.

[0043] The second step is the processing, installation, and debugging of the deformation tools;

[0044] Based on the conditions input in the first step when the convergence condition is met, design deformation tools and rolling angle and feed angle adjustment fixtures, and then complete the processing, installation and debugging of roll 1, rolling angle and feed angle adjustment fixtures;

[0045] The third step is to adjust the deformation parameters:

[0046] After the deformation tool is installed and debugged, adjust the feed angle β, rolling angle γ, roll gap and roll speed according to the optimal process parameters obtained in the first step.

[0047] Step 4: Heating and rolling to form the shape:

[0048] The heated billet 4 is transferred from the heating furnace to the feed chute of the rolling mill within 10 seconds. The billet 4 is twisted before rolling using a torsion deformation device in the feed chute. The billet 4, after being twisted and deformed, is then sent to the deformation zone between two rotating rolls 1. The billet 4 undergoes a forward spiral motion in the deformation zone until the deformation is completed. The billet 4 completely leaves the deformation zone, and the rolled tube is air-cooled to room temperature before isothermal annealing is completed.

[0049] Specifically, the billet 4 is guided by the guide plate 2 in the deformation zone. The billet 4 is rolled into a tube by the spiral advance action in the deformation zone in conjunction with the action of the mandrel 3.

[0050] In the fourth step, the pre-rolling torsion angle is not less than 55°, the feed angle β is greater than 12°, the rolling angle γ is greater than 15°, the roll surface cone angle α is in the range of 2°-6°, and the roll speed is not less than 30 r / min.

[0051] The radial compression ratio of billet 4 during the rolling process in the deformation zone is not less than 8%. The radial compression ratio is the ratio of the difference between the original diameter of billet 4 before deformation and the roll gap to the original diameter, so as to increase the friction force of billet 4 during the biting process.

[0052] Example 1

[0053] Step S1, Design of the deformation tool and determination of deformation parameters:

[0054] A finite element model of seamless steel pipe rolling was established using finite element simulation, and the convergence condition was set as follows: the torsion angle at any point in the deformation zone is not less than 50°.

[0055] Determine the roll cone angle α, feed angle β, rolling angle γ, roll speed and roll gap; if the billet 4 meets the convergence condition under the adjustment parameters of the determined roll cone angle α, feed angle β, rolling angle γ, roll speed and roll gap, proceed to the next step; if the convergence condition is not met, repeat the first step until the convergence condition is met.

[0056] Step S2, machining and installation of the deformation tool:

[0057] Based on the optimal process parameters determined in the first step: pre-rolling torsion angle = 55°, rolling angle γ = 16°, feed angle β = 13°, roll surface cone angle α = 3°, roll gap = 70.4mm, roll speed = 35r / min, then complete the processing, installation and debugging of the pre-rolling roll 1, rolling angle and feed angle adjustment fixtures;

[0058] Step S3, Adjustment of deformation parameters:

[0059] Based on the optimal process parameters: pre-rolling torsion angle = 65°, rolling angle γ = 16°, feed angle β = 13°, roll gap = 70.4mm, roll speed = 35r / min, the installation and debugging of the deformation tooling were completed.

[0060] Step S4, heating and rolling to form:

[0061] The heated billet 4 is transferred from the heating furnace to the mill guide chute within 10 seconds. Then, the billet 4 is twisted before rolling using a pre-rolling torsion deformation device. The torsion-deformed billet 4 is then sent to the deformation zone between two co-rotating rolls 1 through the guide chute. With the help of the mandrel 3 arranged in the deformation zone, the billet 4 moves forward in a spiral motion in the deformation zone until the deformation is completed. The billet 4 is completely removed from the deformation zone and the rolled tube is air-cooled to room temperature.

[0062] Step S5, isothermal annealing:

[0063] The capillary tubes obtained in step S4 are placed in a box furnace and heated to 800°C for 2 hours. Then they are rapidly cooled to 710°C and held for 3 hours. Finally, they are removed from the furnace and air-cooled to room temperature.

[0064] In this embodiment, the billet 4 is tested, and its original microstructure is as follows: Figure 5 As shown, the average grain size is 85 μm; carbide surface scan Figure 6 As shown, the microstructure exhibits a chain-like distribution. The seamless steel pipe obtained using this invention was tested, and its microstructure grain diagram is shown below. Figure 7 The average grain size is 7.6 μm; its carbide scanning pattern is as follows. Figure 8 Carbides are broken and dispersed; and

[0065] The hardness of the rolled and annealed state is HV198.6.

[0066] Example 2

[0067] Based on Example 1, the torsional deformation device includes torsional deformation components arranged at both ends along the conveying direction in the guide trough. Each torsional deformation component includes a worm gear reduction structure for inputting rotational power and a torsional gear 7 driven to rotate by the worm gear reduction structure. A blank placement hole 9 for inserting a blank 4 is opened at the center of the torsional gear 7, and a blank fixing component is fitted on the torsional gear 7. The blank fixing component is used to fix the blank 4 inserted into the blank placement hole 9. In use, the torsional gears 7 in the two torsional deformation components rotate in opposite directions.

[0068] In this embodiment, the worm gear reduction structure consists of a meshing worm wheel 6 and a worm 5, with the worm wheel 6 meshing with a torsion gear 7. During use, both ends of the billet pass through the two billet placement holes 9 in the two torsion deformation assemblies, respectively. Both ends of the billet 4 are then fixed by the billet fixing assembly. A motor is connected to the transmission end of the worm 5 in each torsion deformation assembly. The motor drives the worm 5 to rotate, causing the worm wheel 6 to rotate, which in turn drives the torsion gear 7 to rotate. The two motors rotate in different directions, so that the two torsion gears 7 rotate in opposite directions, causing the two ends of the billet to rotate in different directions, resulting in torsion deformation of the billet 4. After the pre-torsion of the billet 4 is completed, the motors stop running, the billet fixing assembly disengages from the ends of the billet, and the pushing device in the rolling mill pushes the billet 4 into the rolling mill for rolling.

[0069] Specifically, in this embodiment, the billet fixing components all include multiple telescopic clamping structures 10 fixedly mounted on the torsion gear 7. The multiple telescopic clamping structures 10 are arranged circumferentially on the outer side of the discharge end of the billet placement hole 9. Specifically, the clamping and fixing state of the end of the billet is controlled by adjusting the telescopic extension of the multiple telescopic clamping structures 10, so that the billet 4 can stably complete the pre-torsion work and then smoothly enter the rolling mill for rolling under the push of the pushing device in the rolling mill.

[0070] Each telescopic clamping structure 10 includes a blank fixing shaft 101 and a connector 102 that are slidably arranged on the torsion gear 7 in its radial direction. One end of the blank fixing shaft 101 is located on the discharge end side of the blank placement hole 9, and the other end is connected to the connector 102 by a telescopic spring 103. A cam 104 is also rotatably arranged on the torsion gear 7. The cam 104 is located on the side of the connector 102 and slides against the connector 102.

[0071] When fixing the ends of the blank 4, rotate the cam 104 in each telescopic clamping structure 10 so that the cam 104 rotates from its closest point to the connector 102 to its furthest point to the connector 102. This causes the connector 102 to move closer to the blank fixing shaft 101. The connector 102, through the telescopic spring 103, moves the blank fixing shaft 101 closer to the central axis of the blank placement hole 9, thereby clamping and fixing the ends of the blank 4 inserted into the blank placement hole 9. The design of the telescopic spring 103 allows the blank fixing shaft 101 to move along its axial direction for adjustment, so that the blank fixing assembly can clamp and fix blanks 4 of different thicknesses. After the blank 4 has completed the pre-twist, the cam 104 rotates from its farthest edge to its closest edge to the connector 102, causing the blank fixing shaft 101 to move in the opposite direction to release the clamping and fixing of the blank 4. In this embodiment, the cam 104 can be driven to rotate by a motor.

[0072] Example 3

[0073] Based on embodiment 2, a guide ring 8 is fixedly installed on the torsion gear 7. The guide ring 8 is located outside the discharge end of the blank placement hole 9 and is coaxially arranged with the blank placement hole 9. Multiple guide holes are opened on the side wall of the guide ring 8 in a ring arrangement. The clamping ends of the blank fixing shaft 101 in the multiple telescopic clamping structures 10 pass through the multiple guide holes one by one.

[0074] By having multiple guide holes on the guide ring 8 correspond one-to-one with the clamping ends of the blank fixing shaft 101 in the multiple telescopic clamping structures 10, the installation stability of each telescopic clamping structure 10 can be improved. At the same time, the guide holes guide the movement of the corresponding blank fixing shaft 101, thereby improving the running accuracy of the blank fixing shaft 101.

[0075] In this embodiment, there are 6 telescopic clamping structures 10 and 6 guide holes.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A spinning process for producing seamless steel tubes for bearing rings, characterized in that, The process includes the following steps: Step 1: Design of the deformation tool and determination of deformation parameters: Using finite element simulation, a finite element model of the seamless steel pipe rolling process is established, setting the convergence condition as follows: the torsion angle at any point within the deformation zone is not less than 50°; the roll cone angle α, feed angle β, rolling angle γ, roll gap, and roll speed are determined; if the billet's torsion angle meets the convergence condition given the determined shape of the deformation tool and deformation parameters, proceed to the next step; otherwise, repeat the previous steps until the forming condition is met; Step 2: Processing, installation, and debugging of the deformation tool: Based on the conditions input in Step 1 when the convergence condition is met, the deformation tool and the rolling angle and feed angle adjustment fixtures are designed, and then the rolls and rolling angle are adjusted. The process includes processing, installation, and debugging of the feed angle adjustment fixture; the third step is the adjustment of deformation parameters: after the deformation tool is installed and debugged, the feed angle β, rolling angle γ, roll gap, and roll speed are adjusted according to the optimal process parameters obtained in the first step; the fourth step is heating and rolling: the heated billet is transferred from the heating furnace to the guide trough of the rolling mill and completed within 10 seconds. The billet is twisted before rolling using a torsion deformation device in the guide trough. The billet after torsion deformation is then sent to the deformation zone between two rolls rotating in the same direction. The billet undergoes a forward spiral motion in the deformation zone until the deformation is completed. The billet completely leaves the deformation zone and the rolled tube is air-cooled to room temperature, followed by isothermal annealing.

2. The spinning process for producing seamless steel tubes for bearing rings according to claim 1, characterized in that: In the fourth step, the pre-rolling torsion angle is not less than 55°, the feed angle β is greater than 12°, the rolling angle γ is greater than 15°, the roll surface cone angle α is in the range of 2°-6°, and the roll speed is not less than 30 r / min.

3. The spinning process for producing seamless steel tubes for bearing rings according to claim 1 or 2, characterized in that: The torsional deformation device in the fourth step includes torsional deformation components arranged at both ends of the guide trough along its conveying direction. Each torsional deformation component includes a worm gear reduction structure for inputting rotational power and a torsional gear driven to rotate by the worm gear reduction structure. A blank placement hole for inserting a blank is opened at the center of the torsional gear, and a blank fixing component is fitted on the torsional gear to fix the blank inserted into the blank placement hole. In use, the torsional gears in the two torsional deformation components rotate in opposite directions.

4. The spinning process for producing seamless steel tubes for bearing rings according to claim 3, characterized in that: The billet fixing assembly includes multiple telescopic clamping structures fixedly mounted on the torsion gear, and the multiple telescopic clamping structures are arranged circumferentially on the outside of the discharge end of the billet placement hole.

5. The spinning process for producing seamless steel tubes for bearing rings according to claim 4, characterized in that: Each of the telescopic clamping structures includes a blank fixing shaft and a connector that are slidably arranged on the torsion gear in its radial direction. One end of the blank fixing shaft is located on the discharge end side of the blank placement hole, and the other end is connected to the connector by a telescopic spring. A cam is also rotatably arranged on the torsion gear, and the cam is located on the side of the connector and slides against the connector.

6. The spinning process for producing seamless steel tubes for bearing rings according to claim 5, characterized in that: A guide ring is fixedly installed on the torsion gear. The guide ring is located outside the discharge end of the blank placement hole and is coaxially arranged with the blank placement hole. Multiple guide holes are opened on the side wall of the guide ring in a ring arrangement. The clamping ends of the blank fixing shafts in the multiple telescopic clamping structures pass through the multiple guide holes one by one.

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