A production process of seamless steel pipe for high-performance bearing ring

Abstract

The application discloses a production process of a high-performance seamless steel pipe for bearing rings, which 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 the PTR rotary rolling technology at the temperature of the two-phase region to effectively break the size of carbides in the steel, refine the grain size, and make the carbides uniformly distributed in the steel, thereby significantly improving the strength and toughness of the seamless steel pipe and the fatigue life, and the low-temperature rolling can control the secondary growth of the carbides in the cooling process after the rolling. The PTR process avoids the effect of the traditional forging and pressing which needs multiple passes of repeated deformation to refine the carbides and the grains.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe production, and in particular to a production process of a seamless steel pipe for high-performance bearing rings. Background Art

[0002] Bearing rings are annular parts of centripetal rolling bearings with one or more raceways. Common high-performance bearings such as wind power bearings, aviation bearings, mechanical bearings, etc. are special bearings with harsh operating environments, high maintenance costs, and require a long service life. In addition, some bearings work for a long time under ultra-high speed, high load, high temperature and other harsh working conditions.

[0003] The bearing rings used in the above-mentioned high-performance bearings have relatively high requirements for their performance and structure, and the traditional production technology of bearing rings is forging and cross-rolling and piercing. Among them, the forging process is as follows: blanking - box furnace heating - upsetting - punching - hole expansion - pre-rolling - final rolling. Due to its own characteristics, this process has limited size of blanks produced in a single production; punching is required in the middle of the process, and the material utilization rate is relatively low; there are many process steps, and the production efficiency is low; the process cost is relatively high. The ordinary cross-rolling and piercing process is as follows: box furnace heating - cross-rolling and piercing - blanking - final rolling. Compared with forging, the material utilization rate is high and the production efficiency is also high. However, due to the restrictions of the roller shape on the process parameters (feed angle β and rolling angle γ), the material performance is not significantly improved, and it still cannot meet the needs of the above-mentioned high-performance bearings during use.

[0004] The high-performance bearing rings currently used are generally made from high-performance seamless steel pipes as raw materials. High-performance seamless steel pipes are currently made by longitudinal rolling. For example, the patent application document with application number CN202010260435.5 introduces a method for producing rare earth bearing seamless steel pipes using Φ200mm round tube billets, including:

[0005] The steel billet is heated once, the seamless steel pipe is hot rolled continuously, and the steel pipe is quickly cooled after rolling;

[0006] in:

[0007] The total heating time 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 slowly increased during steel burning to ensure uniform heating temperature of the steel billet and reduce temperature difference. The temperature difference of the same steel billet shall not be greater than 50℃, but the steel burning time must be guaranteed; the air volume in the furnace cannot be too large, and a slightly reducing flame must be maintained.

[0008] During the billet rolling process, ensure that the steel billet is smooth and has no sharp edges to avoid scratches and bumps on the surface of the rolled piece; the rolling speed must be uniform, and the cooling water of the rolls must be controlled to prevent the cooling water from being poured directly onto the rolled piece. The bent steel of the rolled piece cannot be straightened by a straightener; for hot continuous rolling of seamless steel pipes, the piercing speed is 400-450rpm, the bite speed is 45-50%, and the piercing angle is 9.5-10.5°; the actual temperature of the steel pipe after sizing is ≥800℃; rapid cooling after rolling is required. In order to prevent the appearance of network carbides during air cooling of the rolled steel pipe, the steel pipe is cooled to 700℃ at a cooling rate of 8℃-13℃ / s after sizing and then slowly cooled on a cooling bed.

[0009] However, the seamless steel pipes in the above patent application documents are basically two-dimensionally deformed during the manufacturing process, and have limited effect on the crushing and homogenization of carbides. Existing research results show that if the number of carbides is too large, the larger the size, and the more uneven the distribution, the lower the fatigue life of the seamless steel pipe, and thus the fatigue life of the bearing rings processed from the seamless steel pipe is also relatively low. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a production process for seamless steel pipes for high-performance bearing rings, so as to solve the problem in the prior art that the carbides in the prepared seamless steel pipes are large in size and unevenly distributed, resulting in a low fatigue life of the seamless steel pipes.

[0011] To achieve the above-mentioned object, the present invention adopts the following technical solution: A production process for a seamless steel pipe for a high-performance bearing ring, comprising the following steps:

[0012] The first step is to design the deformation tool and determine the deformation parameters:

[0013] Finite element simulation was used to establish a finite element model of the seamless steel pipe rolling process, and the forming conditions were set as follows: the circumferential torsion angle at any point in the deformation zone was not less than 50°, and the forging ratio during deformation was not less than 6;

[0014] Determine the shapes of the roll and plug, the roll radius, the roll taper angle α, the feed angle β, the rolling angle γ, the roll distance, and the plug extension; if the circumferential torsion angle and forging ratio of the blank meet the forming conditions after determining the deformation tool shape and deformation parameters, proceed to the next step; if not, repeat the previous steps until the forming conditions are met;

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

[0016] Based on the conditions input when the forming conditions are met in the first step, the deformation tool is designed and the processing, installation and commissioning of the roller and the plug are completed; the feed angle β, rolling angle γ, roller pitch and plug extension are adjusted according to the optimal process parameters obtained in the first step;

[0017] The third step is heating and rolling:

[0018] The billet is placed in a heating furnace and rapidly heated to about 840-880℃, then heated to 1150-1200℃ at a heating rate of 10℃ / min-15℃ / min, kept warm for 90-100min and then taken out of the furnace. It is then cooled to 950℃-1000℃ at a rate of 3℃ / min-8℃ / min. The billet is then sent to the guide trough of the rolling mill and enters the deformation zone to be pierced and rolled into a pipe by radial rolling combined with rotation. Finally, it is cooled to room temperature and isothermal annealing is performed.

[0019] Technical principle: When the billet enters the rolling zone, the Mannesmann effect is utilized to apply strong rotation during radial rolling. Relying on continuous local compression and torsion composite deformation, the effect of small load and large deformation is achieved, and the carbides in the seamless steel pipe are evenly and finely dispersed, which greatly improves the fatigue life of the seamless steel pipe, thereby extending the life of the prepared bearing rings and making them more reliable.

[0020] Furthermore, the roller curvature radius is not less than 700 mm.

[0021] Furthermore, the feed angle β is greater than 12°, the rolling angle γ is greater than 15°, the roller speed is not less than 25 r / min, and the radial compression rate of the billet during rolling in the deformation zone is not less than 12%.

[0022] Furthermore, the roller is a double-tapered roller with a curved surface, and the roller surface cone angle of the roller is 2°-8°.

[0023] Furthermore, the deformation zone is located between two rotating rollers and is pierced and rolled in cooperation with a rotating plug.

[0024] Furthermore, the active end of the plug is conical, and the forward extension of the plug is 20mm-50mm.

[0025] Furthermore, during the rolling process, the deformation speed is 0.35 m / s-0.55 m / s.

[0026] Furthermore, in the deformation zone, the blank undergoes compression-torsion composite deformation at any position during the deformation process, and the circumferential torsion angle is greater than 60°.

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

[0028] After the forming conditions are met by optimizing the parameters such as the roller surface radius, roller surface cone angle α, feed angle β and rolling angle, the processing is carried out in combination with reasonable rolling conditions, so that the forging ratio during deformation is not less than 6 and the circumferential torsion angle is not less than 50°. The grain size of the material in the prepared seamless steel pipe is 9μm, the carbide size should be 0.3-0.8μm, and the carbide distribution is uniform; at the same time, this production process is easy to operate and control. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0030] Figure 2 This is a schematic diagram of the roller rolling principle of an embodiment of the present invention;

[0031] Figure 3 This is the original organization diagram of the blank in Example 1;

[0032] Figure 4 This is the original carbide diagram of the blank in Example 1;

[0033] Figure 5 This is the organizational diagram of the seamless steel pipe after rolling in Example 1;

[0034] Figure 6 is the carbide diagram of the rolled seamless steel pipe in Example 1;

[0035] Figure 7 This is the original organization diagram of the blank in Example 2;

[0036] Figure 8 This is the original carbide diagram of the blank in Example 2;

[0037] Figure 9 This is the organizational diagram of the seamless steel pipe after rolling in Example 2;

[0038] Figure 10 This is the carbide diagram of the rolled seamless steel pipe in Example 2.

[0039] The reference numerals in the drawings of the specification include: roller 1, plug 2, blank 3, feed angle 4, and rolling angle 5. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below through specific embodiments:

[0041] A production process for a seamless steel pipe for a high-performance bearing ring comprises the following steps:

[0042] The first step is to design the deformation tool and determine the deformation parameters:

[0043] The finite element model of the seamless steel pipe rolling process is established by using finite element simulation, and the forming conditions are set as follows: the circumferential torsion angle of any point in the deformation zone is not less than 50°, and the forging ratio in the deformation is not less than 6;

[0044] The shape of the roll and the top head, the roll surface radius, the roll surface taper angle α, the feed angle β, the rolling angle γ, the roll gap and the protruding amount of the top head are determined; if the circumferential torsion angle and the forging ratio of the blank meet the forming conditions under the conditions of determining the shape of the deformation tool and the deformation parameters, the next step is performed, if not, repeat the previous step until the forming conditions are met;

[0045] The roll surface radius is not less than 700 mm, the feed angle β is greater than 12°, the rolling angle γ is greater than 15°, the roll speed is not less than 25 r / min, and the radial compression rate of the blank in the rolling process in the deformation zone is not less than 12%;

[0046] The roll is a double-tapered roll with a curved surface, and the roll surface taper angle is 2°-8°;

[0047] The acting end of the top head is conical, and the protruding amount of the top head is 20 mm-50 mm;

[0048] The second step is the processing, installation and adjustment of the deformation tool and the adjustment of the deformation parameters:

[0049] According to the conditions input when the forming conditions are met in the first step, the deformation tool is designed and the processing, installation and adjustment of the roll and the top head are completed; the feed angle β, the rolling angle γ, the roll gap, and the protruding amount of the top head are adjusted according to the optimal process parameters obtained in the first step;

[0050] The third step is heating and rolling forming:

[0051] The blank is placed in a heating furnace and quickly heated to about 840-880℃, then heated to 1150-1200℃ at a heating rate of 10℃ / min-15℃ / min, and then kept for 90-100 min before being taken out of the furnace, then cooled to 950℃-1000℃ at a rate of 3℃ / min-8℃ / min, then the blank is sent to the guide groove of the rolling mill and enters the deformation zone to form a pipe by radial rolling combined with rotation, the deformation speed is 0.35 m / s-0.55 m / s, and finally cooled to room temperature and isothermally annealed.

[0052] In the deformation zone, the blank is subjected to compression and torsion deformation at any position in the deformation process.

[0053] The present invention utilizes two-phase temperature rolling combined with PTR spinning technology to effectively break down carbides in the steel, refine grain size, and evenly distribute carbides throughout the steel, significantly improving the strength, toughness, and fatigue life of seamless steel pipes. Furthermore, low-temperature rolling controls the secondary growth of carbides during the post-rolling cooling process. The PTR process avoids the multiple, repeated deformations required by traditional forging to refine carbides and grains.

[0054] Example 1

[0055] Step S1, deformation tool design and deformation parameter determination:

[0056] Finite element simulation was used to establish a finite element model for seamless steel pipe rolling. The forming conditions were set as follows: the circumferential torsion angle at any point in the deformation zone was not less than 50°, and the forging ratio during deformation was not less than 6.

[0057] Determine the shapes of the roll and plug, the roll radius, the roll taper angle α, the feed angle β, the rolling angle γ, the roll distance, and the plug extension; if the circumferential torsion angle and forging ratio of the blank meet the forming conditions after determining the deformation tool shape and deformation parameters, proceed to the next step; if not, repeat the previous steps until the forming conditions are met;

[0058] The main deformation parameters are bearing steel GCr15, with a diameter of 90mm and a length of 600mm. The radius of the single-sided curved roller is 848mm, the feed angle is 14°, the rolling angle is 17°, and the radial compression rate of a single rolling is 18%.

[0059] Step S2, processing and installation of deformation tools:

[0060] According to the optimal process parameters determined in the first step: the torsion angle is 50°, the forging ratio in deformation is 6, the rolling angle γ = 17°, the feed angle β = 14°, the roller surface taper angle α = 3°, the roller gap = 72mm, the roller surface radius R = 848mm, and the head extension is 25mm. Then, the design, processing, and installation of the roller, the head, and the rolling angle and feed angle adjustment tooling are completed;

[0061] Step S3, adjustment of deformation parameters:

[0062] According to the optimal process parameters: rolling angle γ = 17°, feed angle β = 14°, roller distance = 72mm, and the head extension is 25mm, the deformation tooling is installed and debugged;

[0063] Step S4, heating and rolling forming:

[0064] The billet is placed in a heating furnace and rapidly heated to 850°C, then heated to 1150°C at a heating rate of 15°C / min, then kept in the heating furnace for 90 minutes, removed from the furnace, and cooled to 1000°C at a rate of 5°C / min. It is then transferred to the guide trough of the rolling mill, through which the billet is sent to the deformation zone between two co-rotating rolls at a deformation rate of 0.4m / s. The billet undergoes a forward spiral motion in the deformation zone, and at the same time, the solid bar is rolled into a tube under the action of the rotating mandrel until the deformation is completed and the billet is completely out of the deformation zone. The rolled tube is then air-cooled to room temperature.

[0065] Step S5, isothermal annealing treatment:

[0066] After heating to 810℃ in a box furnace, keep it warm for 120min, then cool it to 710℃ at a rate of 15℃ / min and put it into the furnace to keep it warm for 3h, then cool it to 650℃ at a rate of 1℃ / s, and finally take it out of the furnace and air cool it to room temperature.

[0067] Based on the above examples, the original organization such as Figure 3 As shown, the average grain size is 80μm; carbide Figure 4 As shown in the figure, the hardness distribution is in a network shape, and the carbides are segregated. The hardness distribution of the whole sample varies greatly. Figure 5 Schematic diagram of the grains of the seamless steel pipe processed by the present invention. Figure 6 The carbide scanning photo of the grain diagram of the seamless steel pipe processed by the present invention shows that the average grain size is 9.8 μm, and the carbides are broken and dispersed; the hardness after annealing after rolling is 201 HV, and the hardness of the entire sample is uniformly distributed.

[0068] Example 2

[0069] Step S1, deformation tool design and deformation parameter determination:

[0070] Finite element simulation was used to establish a finite element model for seamless steel pipe rolling. The forming conditions were set as follows: the circumferential torsion angle at any point in the deformation zone was not less than 60°, and the forging ratio during deformation was not less than 7.

[0071] Determine the roll and plug shape, roll radius, roll taper angle α, feed angle β, rolling angle γ, roll distance, and plug extension. If the blank's circumferential torsion angle and forging ratio meet the forming conditions after determining the deformation tool shape and deformation parameters, proceed to the next step. If not, repeat the previous steps until the forming conditions are met.

[0072] The main deformation parameters are 8Cr4Mo4V bearing steel, with a diameter of 80mm and a length of 500mm. The radius of the single-sided curved roller is 945mm, the feed angle is 12°, the rolling angle is 18°, and the radial compression rate of a single rolling is 15%.

[0073] Step S2: Processing, installation and debugging of deformation tools:

[0074] According to the optimal process parameters determined in the first step: torsion angle of 60°, forging ratio of 7 during deformation, rolling angle γ = 18°, feed angle β = 16°, roller taper angle α = 3.5°, roller pitch = 71.2mm, roller radius R = 945mm, and plug extension of 20mm, the design, processing, and installation of the roller, plug, rolling angle, and feed angle adjustment tooling were completed.

[0075] Step S3: Adjustment of deformation parameters: According to the optimal process parameters: rolling angle γ = 18°, feed angle β = 12°, roller distance = 71.2 mm, complete the installation and commissioning of the deformation tooling;

[0076] Step S4, heating and rolling forming:

[0077] The billet is placed in a heating furnace and rapidly heated to about 850°C, then heated to 1150°C at a heating rate of 10°C / min, then kept in the heating furnace for 90 minutes, removed from the furnace, and cooled to 1000°C at a rate of 3°C / min. It is then transferred to the guide trough of the rolling mill, and the billet is sent to the deformation zone between two co-rotating rolls through the guide trough at a deformation speed of 0.35m / s. The billet undergoes a forward spiral motion in the deformation zone, and at the same time, the solid bar is rolled into a tube under the action of the rotating mandrel until the deformation is completed and the billet is completely out of the deformation zone. The rolled tube is then air-cooled to room temperature.

[0078] Step S5, isothermal annealing treatment:

[0079] After heating to 780℃ in a box furnace, keep it warm for 30 minutes, then cool it to 690℃ at a rate of 12℃ / min and put it into the furnace to keep it warm for 2 hours, then cool it to 650℃ at a rate of 1.5℃ / s, and finally take it out of the furnace and air cool it to room temperature.

[0080] Based on the above examples, the original organization such as Figure 7 As shown, the average grain size is 80μm; carbide Figure 8 As shown, it is distributed in a chain shape. Figure 9 Schematic diagram of the grains of the seamless steel pipe processed by the present invention. Figure 10 The carbide scanning photo of the grain diagram of the seamless steel pipe processed by the present invention shows that the average grain size is 8 μm, and the carbides are broken and dispersed; the hardness after annealing after rolling is 240 HV, and the hardness of the entire sample is uniformly distributed.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A production process for seamless steel pipes for high-performance bearing rings, characterized in that: The following steps are involved: The first step is to design the deformation tool and determine the deformation parameters: Finite element simulation was used to establish a finite element model of the seamless steel pipe rolling process, and the forming conditions were set as follows: the circumferential torsion angle at any point in the deformation zone was not less than 50°, and the forging ratio during deformation was not less than 6; Determine the shapes of the roll and plug, the roll radius, the roll taper angle α, the feed angle β, the rolling angle γ, the roll distance, and the plug extension; if the circumferential torsion angle and forging ratio of the blank meet the forming conditions after determining the deformation tool shape and deformation parameters, proceed to the next step; if not, repeat the previous steps until the forming conditions are met; The second step is the processing, installation and debugging of deformation tools and the adjustment of deformation parameters: Based on the conditions input when the forming conditions are met in the first step, the deformation tool is designed and the processing, installation and commissioning of the roller and the plug are completed; the feed angle β, rolling angle γ, roller pitch and plug extension are adjusted according to the optimal process parameters obtained in the first step; The third step is heating and rolling: The billet is placed in a heating furnace and rapidly heated to 840-880℃, then heated to 1150-1200℃ at a heating rate of 10℃ / min-15℃ / min, kept warm for 90-100min and then taken out of the furnace. It is then cooled to 950℃-1000℃ at a rate of 3℃ / min-8℃ / min. The billet is then sent to the guide trough of the rolling mill and enters the deformation zone to be pierced and rolled into a pipe by radial rolling combined with rotation. Finally, it is cooled to room temperature and isothermal annealing is performed.

2. The production process of a high-performance seamless steel pipe for bearing rings according to claim 1, characterized in that: The roller curved surface radius is not less than 700 mm.

3. The production process of a high-performance seamless steel pipe for bearing rings according to claim 1, characterized in that: The feed angle β is greater than 12°, the rolling angle γ is greater than 15°, the roller speed is not less than 25 r / min, and the radial compression rate of the blank is not less than 12% during the rolling process in the deformation zone.

4. The production process of a high-performance seamless steel pipe for bearing rings according to claim 1, characterized in that: The roller is a double-cone roller with a curved surface, and the roller surface cone angle of the roller is 2°-8°.

5. The production process of a seamless steel pipe for high-performance bearing rings according to claim 1, characterized in that: The deformation zone is located between two rotating rollers and is used for piercing and rolling in conjunction with the rotating plug.

6. The production process of a high-performance seamless steel pipe for bearing rings according to claim 5, characterized in that: The active end of the plug is conical, and the forward extension of the plug is 20mm-50mm.

7. The production process of a seamless steel pipe for high-performance bearing rings according to claim 1, characterized in that: During the rolling process, the deformation speed is 0.35m / s-0.55m / s.

8. The production process of a high-performance seamless steel pipe for bearing rings according to claim 1, characterized in that: In the deformation zone, the blank is subjected to compression-torsion composite deformation at any position during the deformation process, and the circumferential torsion angle is greater than 60°.

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