A seamless steel pipe and a method for producing the same
By segmented heating and optimized process parameters, the problem of inner layer thickness during heating of steel billets with a diameter of ∮460mm and above was solved, achieving high-quality production of seamless steel pipes. The temperature difference between the inner and outer layers was controlled within a reasonable range, ensuring that the inner surface of the steel pipe was smooth and defect-free.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DAYE SPECIAL STEEL CO LTD
- Filing Date
- 2023-06-16
- Publication Date
- 2026-07-21
AI Technical Summary
In the existing technology, when steel billets with a diameter of ∮460mm or larger are rapidly heated using an annular heating furnace, an inner layer of laps will be formed on the inner surface of the steel pipe. This is mainly due to the large temperature difference between the inner and outer layers during heating, which leads to uneven thermal stress and may cause cracks and inner layer defects.
The steel billet is heated in sections using a ring furnace, including a low-temperature heating section, an enhanced heating section, and a soaking section. The temperature of the low-temperature heating section is controlled at 600℃-1000℃, and the heating rate is 80-100℃/h. The heating time and temperature difference are optimized and controlled within 28℃. Combined with the piercing and rolling processes, an ASSEL three-roll rolling mill is used, and the piercing and rolling parameters are adjusted to reduce the temperature difference between the inner and outer layers.
The temperature difference between the inner and outer layers of large-sized round billets was effectively controlled, avoiding the phenomenon of inner layer overlap, improving the production qualification rate of seamless steel pipes to 100%, and ensuring the quality of the inner surface of the steel pipes.
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Figure CN116871327B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metal processing technology, and specifically relates to a seamless steel pipe and its production method. Background Technology
[0002] The billet diameter range required for steel pipe production by the 460 mill is: ∮270mm, ∮330mm, ∮390mm, ∮460mm, and ∮500mm. The number and output of mills producing seamless steel pipes from round billets with diameters of ∮460mm and above are continuously increasing, indicating a significant market demand for large-diameter seamless steel pipes. Currently, the 460 mill employs a rapid heating method for the round billets before rolling, meaning the billets are heated at a constant maximum rate from the moment they enter the furnace until they exit the furnace at the process temperature.
[0003] However, this heating method has significant drawbacks for round billets with a diameter of 460mm or larger. When using a ring furnace for rapid heating to produce steel pipes from large-diameter round billets (460mm or larger), severe internal scale (or flaking) appears on the inner surface of the steel pipes. Internal scale is a common quality defect on the inner surface of steel pipes. Simply put, it means that there are raised metal pieces on the inner surface that are connected to the substrate, resulting in an irregular, unevenly raised metal scale.
[0004] Therefore, it is particularly important to develop a process that eliminates the phenomenon of inner lap scale on the inner surface of seamless steel pipes when using round billets with a diameter of 460mm or larger. Summary of the Invention
[0005] This invention provides a seamless steel pipe and its production method, the purpose of which is to solve the problem of inner scale formation in steel pipes when steel billets with a diameter of ∮460mm or larger are rapidly heated using an annular heating furnace in the prior art.
[0006] The inventors discovered that when steel billets with a diameter of ∮460mm or larger are rapidly heated using a ring-shaped furnace, a layer of excess steel may form inside the billet. This is likely because the temperature distribution along the cross-section is uneven during billet heating, with the surface temperature higher than the inner layer. This difference in thermal expansion between the inner and outer layers generates thermal stress (also known as temperature stress) between them. The faster the heating rate, the larger the billet diameter, and the lower the thermal conductivity of the steel, the greater the resulting thermal stress. Especially in the low-temperature range, excessively rapid heating can create significant thermal stress in the billet. When this thermal stress exceeds the metal's strength at that temperature, it can lead to cracking defects. Furthermore, the piercing stress during the piercing process may also cause an inner layer of excess steel.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] In a first aspect, the present invention provides a method for producing seamless steel pipes, which uses round steel billets as raw materials and sequentially includes a heating process, a piercing process, a rolling process, and a diameter reduction process.
[0009] The heating process includes: heating the steel billet in an annular heating furnace, wherein the steel billet sequentially passes through a low-temperature heating section, an enhanced heating section, and a soaking section of the annular heating furnace;
[0010] The temperature of the low-temperature heating section is 600℃-1000℃ (e.g., 700℃, 800℃).
[0011] The heating rate of the steel billet in the low-temperature heating section is 80-100℃ / h (e.g., 85℃ / h, 90℃ / h, 95℃ / h), the heating time of the steel billet in the low-temperature heating section is ≥300 minutes, and the diameter of the steel billet is ≥460mm.
[0012] In the above production method, as a preferred embodiment, the diameter of the steel billet is 460mm and 500mm.
[0013] In the above production method, as a preferred embodiment, the temperature difference between the inner and outer layers of the steel billet after heating in the low-temperature heating section is controlled within 28°C.
[0014] In this invention, the inner temperature of the billet refers to the temperature at the center of the billet, and the outer temperature refers to the temperature of the outer surface layer of the billet.
[0015] In the above production method, as a preferred embodiment, the temperature of the steel billet entering the annular heating furnace is ≤300℃.
[0016] In the above production method, as a preferred embodiment, the low-temperature heating section includes a preheating section, a first heating zone, and a second heating zone; the temperature of the preheating section is 600-700℃, the temperature of the first heating zone is 900℃, and the total residence time of the steel billet in the preheating section and the first heating zone is ≥225 minutes. The temperature of the second heating zone is 1000℃, and the residence time of the steel billet in the second heating zone is ≥75 minutes.
[0017] In the above production method, as a preferred embodiment, the temperature of the enhanced heating section is 1080℃-1250℃, and the total time the billet stays in the enhanced heating section is ≥150 minutes; the temperature of the soaking section is 1250℃, and the total time the billet stays in the soaking section is ≥200 minutes.
[0018] More preferably, the enhanced heating section includes heating zone three, heating zone four, and heating zone five, and the soaking section includes soaking zone one and soaking zone two. The temperature of heating zone three is 1080°C, and the billet stays in heating zone three for ≥75 minutes. The temperature of heating zone four is 1180°C, and the billet stays in heating zone four for ≥75 minutes. The temperature of heating zone five, soaking zone one, and soaking zone two is 1250°C, and the total stay time of the billet in heating zone five, soaking zone one, and soaking zone two is ≥240 minutes.
[0019] In this invention, the existing process is adjusted by increasing the residence time of the steel billet in the preheating section, heating zone one, and heating zone two, so that the temperature difference between the inside and outside of the large billet is controlled to be small during heating. As a result, after the steel billet enters the high-temperature zone, the thermal conductivity increases with the increase of the heating temperature, so that the temperature difference between the inside and outside of the steel billet does not change much.
[0020] In the above production method, as a preferred embodiment, the pressure of the low-temperature heating section is 10-22 Pa.
[0021] In the above production method, as a preferred embodiment, the perforation process is carried out using a perforation machine;
[0022] The process parameters of the perforating machine are controlled as follows: total reduction is 7-15% (e.g., 8%, 9%, 10%, 11%, 12%, 13%, 14%), top reduction is 4-7% (e.g., 5%, 6%), and advance angle is 8-15° (e.g., 9°, 11°, 12°, 13°, 14°).
[0023] And / or, the diameter of the capillary tube obtained by the perforation process is 460-520mm, and the wall thickness is 50-120mm;
[0024] And / or, the temperature of the perforation process is 1150-1180℃.
[0025] In this invention, the formula for calculating the total reduction of the piercing mill is (bill diameter - roll gap) / billet diameter × 100%, and the formula for calculating the top reduction of the piercing mill is (bill diameter - top extension × 0.12223 - roll gap) / billet diameter × 100%.
[0026] In this invention, the billet diameter refers to the diameter of the steel billet before heating.
[0027] In the above production method, as a preferred embodiment, the tube rolling process is carried out using an ASSEL three-roll tube rolling mill.
[0028] And / or, the temperature of the tube rolling process is 1000-1150℃.
[0029] In this invention, the diameter reduction process is to process the rough tube obtained from the tube rolling process into the size required by the customer.
[0030] Secondly, the present invention also provides a seamless steel pipe, which is prepared by the above-described production method.
[0031] In the above-mentioned seamless steel pipe, as a preferred embodiment, the outer diameter of the seamless steel pipe is 426-495mm and the wall thickness is 35-70mm.
[0032] In the above-mentioned seamless steel pipe, as a preferred embodiment, the seamless steel pipe has a yield strength ≥450MPa and a tensile strength ≥700MPa.
[0033] The method of this invention is applicable to the production of seamless steel pipes made of 27SiMn and 30CrMnSi materials.
[0034] Compared with the prior art, the present invention has at least one of the following beneficial effects:
[0035] 1. This invention provides a method for producing seamless steel pipes, using round steel billets as raw materials, and sequentially including a heating process, a piercing process, a rolling process, and a diameter reduction process; wherein, the heating process includes: heating the steel billet in an annular heating furnace, the steel billet sequentially passing through a low-temperature heating section, an intensified heating section, and a soaking section of the annular heating furnace; wherein, the temperature of the low-temperature heating section is 600℃-1000℃, the heating rate of the steel billet in the low-temperature heating section is 80-100℃ / h, the heating time of the low-temperature heating section is ≥300 minutes, and the diameter of the steel billet is ≥460mm. For round steel billets with a diameter of 460mm and above, preheating in a low-temperature zone and sufficient heating time are used to avoid the problem of large temperature differences between the inner and outer layers and harmful stress in the steel billet caused by excessively rapid heating and a short low-temperature section.
[0036] 2. The production method of this invention can ensure that the temperature difference between the inner and outer layers of large-sized round billets is controlled within a reasonable range, and the temperature difference can be guaranteed to be within 28°C. No inner patina appears on the inner surface of the pierced steel pipe. This eliminates the quality problems caused by improper heating of round billets with a diameter of 460mm or more.
[0037] 3. The seamless steel pipe prepared by the method of the present invention has a pass rate of up to 100%. Attached Figure Description
[0038] Figure 1 This is a schematic diagram of the heating process for large-diameter round billets in Example 1 and Comparative Example 1. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0040] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.
[0041] The endpoints and any values of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.
[0042] In this invention, unless otherwise specified and / or stated, all numerical values relating to component amounts are expressed as "parts by weight or weight percentages". Process parameters in the following examples that do not specify particular conditions are generally performed under conventional conditions.
[0043] In the embodiments and comparative examples of this application, the chemical composition (wt%) of the round steel billet is as follows:
[0044] C: 0.32, Si: 1.10, Mn: 1.00, P: ≤0.015, S: ≤0.008, Cr: 1.05, Mo: ≤0.05, Ni: ≤0.05, Cu: ≤0.05, V: ≤0.05, W: ≤0.05, Nb: ≤0.01, N: 0.0080, balance Fe.
[0045] Example 1
[0046] This embodiment provides a method for producing seamless steel pipes, using a circular steel billet with a diameter of 460mm as raw material, and sequentially including a heating process, a piercing process, a rolling process, and a diameter reduction process, wherein...
[0047] The heating process uses a ring-shaped heating furnace, which includes a low-temperature heating section, an enhanced heating section, and a homogenization section.
[0048] The temperature of the round steel billet entering the annular heating furnace is ≤300℃.
[0049] like Figure 1 As shown, the maximum temperature of the low-temperature heating section is 1000 °C, the heating rate of the steel billet in the low-temperature heating section is 80 °C / h, and the heating time in the low-temperature heating section is 300 minutes. After preheating in the low-temperature heating section, the temperature difference between the inner and outer layers of the steel billet is 28 °C. The pressure in the low-temperature heating section is 10 - 20 Pa.
[0050] In the low-temperature heating section, the temperature of the preheating section is 600 °C, the temperature of heating zone 1 is 900 °C, and the temperature of heating zone 2 is 1000 °C. The residence time of the steel billet in the preheating section is 120 minutes, the residence time in heating zone 1 is 90 minutes, and the residence time in heating zone 2 is 90 minutes.
[0051] In the enhanced heating section, the temperature of heating zone 3 is 1100 °C, the temperature of heating zone 4 is 1200 °C. The residence time of the steel billet in heating zone 3 is 75 minutes, and the residence time in heating zone 4 is 75 minutes.
[0052] In the enhanced heating section, the temperature of heating zone 5 is 1250 °C. In the soaking section, the temperature of soaking zone 1 is 1250 °C, and the temperature of soaking zone 2 is 1250 °C. The total residence time of the steel billet in heating zone 5, soaking zone 1, and soaking zone 2 is 240 minutes.
[0053] For the piercing process, a piercing mill is used. The total reduction of the piercing mill is 7.6%, the reduction before piercing is 6.7%, and the forward angle is 10°. The parameters of the piercing mill are as follows: roll pitch of the piercing mill: 425 mm, distance between piercing guide plates: 455 mm, diameter of the plug: 422 mm, length of the plug: 830 mm, and extension: 35 mm. The temperature of the piercing process is 1150 °C - 1180 °C. The diameter of the hollow billet obtained from the piercing process is 540 mm, and the wall thickness is 51 mm.
[0054] For the tube rolling process, an Assel three-roll tube rolling mill is used. The parameters of the tube rolling mill are as follows: throat diameter (roll pitch) of the tube rolling mill: 500 mm, mandrel: 416 mm. The temperature of the tube rolling process is 1000 °C - 1150 °C.
[0055] The outer diameter of the seamless steel pipe obtained by the production method of this embodiment is 495 mm, and the wall thickness is 45 mm.
[0056] For the seamless steel pipe of this embodiment, yield strength and tensile strength tests are carried out. The test method for yield strength is to intercept a steel pipe specimen with a specimen bar diameter of 25 mm, and it is measured that the yield strength of the seamless steel pipe of this embodiment ≥ 450 MPa. The test method for tensile strength is to intercept a steel pipe specimen with a specimen bar diameter of 25 mm, and it is measured that the tensile strength of the seamless steel pipe of this embodiment ≥ 700 MPa.
[0057] Judging from the finally obtained seamless steel pipe, no internal double skin phenomenon appears. The seamless steel pipes produced in multiple batches are 100% qualified.
[0058] Example 2
[0059] This embodiment provides a method for producing seamless steel pipes, using a circular steel billet with a diameter of 500mm as raw material, and sequentially including a heating process, a piercing process, a rolling process, and a diameter reduction process, wherein...
[0060] The heating process uses a ring-shaped heating furnace, which includes a low-temperature heating section, an enhanced heating section, and a homogenization section.
[0061] The temperature of the round steel billet entering the annular heating furnace is ≤300℃.
[0062] The highest temperature in the low-temperature heating section is 1000℃, the heating rate of the steel billet in the low-temperature heating section is 80℃ / h, and the heating time in the low-temperature heating section is 300 minutes. After preheating in the low-temperature heating section, the temperature difference between the inner and outer layers of the steel billet is 28℃. The pressure in the low-temperature heating section is 10-20 Pa.
[0063] The temperature of the preheating section in the low-temperature heating zone is 600℃, the temperature of heating zone one is 900℃, and the temperature of heating zone two is 1000℃. The residence time of the billet in the preheating section is 120 minutes, the residence time in heating zone one is 90 minutes, and the residence time in heating zone two is 90 minutes.
[0064] The temperature in the enhanced heating section is 1100℃ in heating zone 3 and 1200℃ in heating zone 4. The billet stays in heating zone 3 for 75 minutes and in heating zone 4 for 75 minutes.
[0065] The temperature of heating zone 5 in the enhanced heating section is 1250℃, the temperature of heating zone 1 in the soaking section is 1250℃, the temperature of heating zone 2 in the soaking section is 1250℃, and the total residence time of the billet in heating zone 5, soaking zone 1 and soaking zone 2 is 240 minutes.
[0066] The piercing process uses a piercing machine with a total reduction of 7.8%, a top reduction of 6.6%, and a forward angle of 9°. The piercing machine parameters are: roller spacing: 461mm, guide plate spacing: 495mm, mandrel diameter: 417mm, mandrel length: 830mm, and mandrel extension: 55mm. The piercing temperature is 1150℃-1180℃. The resulting tube has a diameter of 565mm and a wall thickness of 65mm.
[0067] The tube rolling process uses an ASSEL three-roll tube rolling mill. The mill parameters are as follows: tube rolling mill throat diameter (roll gap): 535mm, mandrel: 416mm. The temperature of the tube rolling process is 1000℃-1150℃.
[0068] The outer diameter of the seamless steel pipe obtained by the production method of this embodiment is 520 mm, and the wall thickness is 60 mm.
[0069] For the seamless steel pipe of this embodiment, yield strength and tensile strength tests are carried out. The test methods for yield strength and tensile strength are the same as those in Embodiment 1. It is measured that the yield strength of the seamless steel pipe of this embodiment is ≥ 450 MPa, and the tensile strength of the seamless steel pipe of this embodiment is ≥ 700 Mpa.
[0070] From the finally obtained seamless steel pipe, no internal double skin phenomenon appears. The seamless steel pipes produced in multiple batches are 100% qualified.
[0071] Embodiment 3
[0072] This embodiment provides a production method for seamless steel pipes. Using a round billet with a diameter of 460 mm as the raw material, it successively includes a heating process, a piercing process, a rolling process, and a reducing process. Among them,
[0073] The heating process is carried out using a ring heating furnace, which includes a low-temperature heating section, a strengthening heating section, and a soaking section.
[0074] The temperature of the round billet entering the ring heating furnace is ≤ 300 °C.
[0075] The maximum temperature of the low-temperature heating section is 900 °C. The heating rate of the billet in the low-temperature heating section is 80 °C / h, and the heating time in the low-temperature heating section is 300 minutes. After preheating in the low-temperature heating section, the temperature difference between the inner and outer layers of the billet is 28 °C. The pressure in the low-temperature heating section is 10 - 20 Pa.
[0076] The temperature of the preheating section in the low-temperature heating section is 600 °C, the temperature of heating zone 1 is 850 °C, and the temperature of heating zone 2 is 900 °C. The residence time of the billet in the preheating section is 120 minutes, the residence time in heating zone 1 is 90 minutes, and the residence time in heating zone 2 is 90 minutes.
[0077] In the strengthening heating section, the temperature of heating zone 3 is 1000 °C, and the temperature of heating zone 4 is 1200 °C. The residence time of the billet in heating zone 3 is 75 minutes, and the residence time in heating zone 4 is 75 minutes.
[0078] In the strengthening heating section, the temperature of heating zone 5 is 1250 °C, the temperature of soaking zone 1 in the soaking section is 1250 °C, and the temperature of soaking zone 2 is 1250 °C. The total residence time of the billet in heating zone 5, soaking zone 1, and soaking zone 2 is 240 minutes.
[0079] For the piercing process, a piercing mill is used. The total reduction of the piercing mill is 10.9%, the reduction before piercing is 6.0%, the forward angle is 10°. Parameters of the piercing mill: the roll pitch of the piercing mill is 410 mm, the distance between the guide plates of the piercing mill is 455 mm, the diameter of the plug is 377 mm, the length of the plug is 745 mm, and the elongation is 185 mm. The temperature of the piercing process is 1150°C - 1180°C. The diameter of the tube blank obtained from the piercing process is 500 mm, and the wall thickness is 50 mm.
[0080] For the tube rolling process, an Assel three-roll tube rolling mill is used. The parameters of the tube rolling mill are as follows: the throat diameter (roll pitch) of the tube rolling mill is 451 mm, and the mandrel is 375 mm. The temperature of the tube rolling process is 1000°C - 1150°C.
[0081] The outer diameter of the seamless steel tube obtained by using the production method of this embodiment is 450 mm, and the wall thickness is 40 mm.
[0082] For the seamless steel tube of this embodiment, yield strength and tensile strength tests are carried out. The test methods for yield strength and tensile strength are the same as those in Embodiment 1. It is measured that the yield strength of the seamless steel tube of this embodiment is ≥450 MPa, and the tensile strength of the seamless steel tube of this embodiment is ≥700 Mpa.
[0083] Judging from the finally obtained seamless steel tube, no internal double skin phenomenon appears. The seamless steel tubes produced in multiple batches are 100% qualified.
[0084] Comparative Example 1
[0085] This comparative example provides a production method of seamless steel tube. Using a round billet with a diameter of 460 mm as the raw material, it successively includes a heating process, a piercing process, a rolling process, and a reducing process. Among them,
[0086] For the heating process, a ring heating furnace is used for heating. The ring heating furnace includes a preheating section, a low-temperature heating section, a strengthening heating section, and a soaking section.
[0087] The temperature of the round billet entering the ring heating furnace is ≤300°C.
[0088] As Figure 1 shown, the highest temperature of the low-temperature heating section is 1050°C, the heating rate of the billet in the low-temperature heating section is 120°C / h, and the heating time in the low-temperature heating section is 200 minutes. After preheating in the low-temperature heating section, the temperature difference between the inner and outer layers of the billet is 50 - 100°C. The pressure in the low-temperature heating section is 10 - 22 Pa.
[0089] In the low-temperature heating section, the temperature of the preheating section is 600°C, the temperature of heating zone 1 is 950°C, and the temperature of heating zone 2 is 1050°C. The residence time of the steel billet in the preheating section is 80 minutes, the residence time in heating zone 1 is 60 minutes, and the residence time in heating zone 2 is 60 minutes.
[0090] In the enhanced heating section, the temperature of heating zone 3 is 1260°C, and the temperature of heating zone 4 is 1280°C. The residence time of the steel billet in heating zone 3 is 60 minutes, and the residence time in heating zone 4 is 60 minutes.
[0091] In the enhanced heating section, the temperature of heating zone 5 is 1280°C. In the soaking section, the temperature of soaking zone 1 is 1280°C, and the temperature of soaking zone 2 is 1280°C. The total residence time of the steel billet in heating zone 5, soaking zone 1, and soaking zone 2 is 180 minutes.
[0092] The piercing process uses a piercing mill. The total reduction of the piercing mill is 7.6%, the reduction before piercing is 6.7%, and the forward angle is 10°. The parameters of the piercing mill are as follows: roll pitch of the piercing mill: 425 mm, distance between piercing guides: 455 mm, diameter of the plug: 422 mm, length of the plug: 830 mm, and plug extension: 35 mm. The temperature of the piercing process is 1150°C - 1180°C. The diameter of the hollow shell obtained from the piercing process is 540 mm, and the wall thickness is 51 mm.
[0093] The tube rolling process uses an Assel three-roll tube rolling mill. The parameters of the tube rolling mill are as follows: throat diameter (roll pitch) of the tube rolling mill: 500 mm, mandrel: 416 mm. The temperature of the tube rolling process is 1000°C - 1150°C.
[0094] The outer diameter of the seamless steel pipe obtained by using the production method of this comparative example is 495 mm, and the wall thickness is 45 mm. For the seamless steel pipe of this comparative example, yield strength and tensile strength tests are carried out. The test methods for yield strength and tensile strength are the same as those in Example 1. It is measured that the yield strength of the seamless steel pipe of this comparative example ≥ 450 MPa, and it is measured that the tensile strength of the seamless steel pipe of this comparative example ≥ 700 Mpa.
[0095] Judging from the finally obtained seamless steel pipe, internal double skin phenomenon appears. 30% of the seamless steel pipes produced in multiple batches are qualified.
[0096] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are within the scope of protection of the pending claims of the present invention.
Claims
1. A method for producing seamless steel pipes, characterized in that, Using round steel billets as raw materials, the process includes heating, piercing, rolling, and diameter reduction in sequence. The heating process includes: heating the steel billet in an annular heating furnace, wherein the steel billet sequentially passes through a low-temperature heating section, an enhanced heating section, and a soaking section of the annular heating furnace; The temperature of the low-temperature heating section is 600℃-1000℃. The heating rate of the steel billet in the low-temperature heating section is 80-100℃ / h, the heating time in the low-temperature heating section is ≥300 minutes, and the diameter of the steel billet is ≥460mm. The temperature difference between the inner and outer layers of the steel billet after heating in the low-temperature heating section is controlled within 28℃. The low-temperature heating section includes a preheating section, a heating zone one, and a heating zone two; The seamless steel pipe is made of 27SiMn or 30CrMnSi. The temperature of the preheating section is 600-700℃, the temperature of the first heating zone is 900℃, and the total residence time of the steel billet in the preheating section and the first heating zone is ≥225 minutes; the temperature of the second heating zone is 1000℃, and the residence time of the steel billet in the second heating zone is ≥75 minutes.
2. The production method according to claim 1, characterized in that, The diameter of the steel billet is 460mm or 500mm; And / or, the temperature of the steel billet entering the annular furnace is ≤300℃.
3. The production method according to claim 1, characterized in that, The pressure in the low-temperature heating section is 10-22 Pa.
4. The production method according to claim 1, characterized in that, The temperature of the enhanced heating section is 1080℃-1250℃, and the total time the billet stays in the enhanced heating section is ≥150 minutes; the temperature of the soaking section is 1250℃, and the total time the billet stays in the soaking section is ≥200 minutes.
5. The production method according to claim 4, characterized in that, The enhanced heating section includes heating zone three, heating zone four, and heating zone five. The soaking zone includes soaking zone one and soaking zone two. The temperature of heating zone three is 1080℃, and the billet stays in heating zone three for ≥75 minutes. The temperature of heating zone four is 1180℃, and the billet stays in heating zone four for ≥75 minutes. The temperature of heating zone five, soaking zone one, and soaking zone two is 1250℃, and the total stay time of the billet in heating zone five, soaking zone one, and soaking zone two is ≥240 minutes.
6. The production method according to claim 1, characterized in that, The perforation process is performed using a perforation machine; The process parameters of the piercing machine are controlled as follows: total reduction is 7-15%, top reduction is 4-7%, and advance angle is 8-15°. And / or, the diameter of the capillary tube obtained by the perforation process is 460-520mm, and the wall thickness is 50-120mm; And / or, the temperature of the perforation process is 1150-1180℃.
7. The production method according to claim 1, characterized in that, The tube rolling process is performed using an Assel three-roll tube rolling mill. And / or, the temperature of the tube rolling process is 1000-1150℃.
8. A seamless steel pipe prepared by the production method according to any one of claims 1-7.
9. The seamless steel pipe according to claim 8, characterized in that, The seamless steel pipe has an outer diameter of 426-495mm and a wall thickness of 35-70mm; And / or, the seamless steel pipe has a yield strength ≥450MPa and a tensile strength ≥700MPa.