Hot-rolled seamless steel pipe and wall thickness controllable machining process thereof

Abstract

The invention provides a hot-rolled seamless steel pipe and a wall thickness controllable processing technology thereof, and aims to solve the problem that the wall thickness of a steel pipe is difficult to accurately control in the prior art. Real-time monitoring and control over the wall thickness of the steel pipe are achieved, so that the wall thickness precision is remarkably improved, raw material components of the seamless steel pipe comprise C, Si, Mn, P, S, Cr, Mo, Ni and Fe, the wall thickness range of the seamless steel pipe is 5-20 mm, and the preparation technology comprises the steps of raw material proportioning, vacuum smelting, mold cylinder preheating and coating treatment, wall thickness laser measurement, rotating speed regulation and control forming, annealing, forced cooling treatment and the like. Through 300-600 times of high-frequency wall thickness measurement per second, the wall thickness uniformity and precision of the steel pipe in the whole production process are ensured in combination with rotating speed regulation and forced cooling, and finally the product quality and economic benefits are improved.

Description

Technical Field

[0001] The invention relates to a hot-rolled seamless steel pipe and a wall thickness controllable processing technology thereof. Background Art

[0002] The traditional hot-rolled seamless steel pipe manufacturing process mainly relies on the control of the raw material composition ratio, rolling temperature and cooling method. However, with the wide application of seamless steel pipes in petrochemical, energy, machinery manufacturing and other fields, the requirements for wall thickness accuracy, material uniformity and corrosion resistance are getting higher and higher.

[0003] In the existing process, although the wall thickness can be controlled to a certain extent by adjusting the chemical composition of the steel and the rolling conditions, it is impossible to effectively and accurately control the change of wall thickness in the whole process. Especially in the hot rolling and cooling process, the wall thickness may have a large deviation, affecting the final performance of the steel pipe. In addition, the cooling rate adjustment in the traditional process is not fine enough, resulting in uneven surface hardness and internal structure of the steel pipe, which is easy to cause defects such as micro cracks.

[0004] Therefore, there is an urgent need for a hot-rolled seamless steel pipe and a processing technology thereof that can accurately control the wall thickness of the steel pipe, so as to accurately control the wall thickness variation of the seamless steel pipe. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the above prior art and provide a hot-rolled seamless steel pipe and a wall thickness controllable processing technology thereof. By adopting a laser interference wall thickness measurement module, a cooling control system, a die drum speed control method and an optimized raw material ratio, the process can monitor and control the wall thickness change of the steel pipe in real time during the manufacturing process, thereby improving the wall thickness accuracy of the steel pipe. The following is a specific solution:

[0006] In one aspect, the present invention provides a hot-rolled seamless steel pipe, wherein the raw material components of the seamless steel pipe are arranged in the following weight percentage: C: 0.05%-0.25%, Si: 0.10%-0.50%, Mn: 0.30%-1.20%, P: ≤0.030%, S: ≤0.030%, Cr: 0.40%-1.10%, Mo: 0.10%-0.30%, Ni: 0.10%-0.40%, and the rest are Fe and unavoidable impurities, and the wall thickness of the seamless steel pipe is 5-20 mm.

[0007] On the other hand, the present invention also provides a wall thickness controllable processing technology for hot-rolled seamless steel pipes, wherein the raw material components of the seamless steel pipe are proportioned in weight percentage as follows: C: 0.05%-0.25%, Si: 0.10%-0.50%, Mn: 0.30%-1.20%, P: ≤0.030%, S: ≤0.030%, Cr: 0.40%-1.10%, Mo: 0.10%-0.30%, Ni: 0.10%-0.40%, and the rest is Fe and unavoidable impurities. The preparation method thereof comprises the following steps: (1) the raw material components are proportioned according to the raw material components, and the raw materials are placed in a vacuum arc furnace. During the smelting process, the temperature is gradually increased to 1640-1660°C and maintained for at least 25 minutes, and a preliminary alloy liquid is obtained after slag removal treatment. ; (2) preheating the mold barrel, the preheating temperature is controlled at 290-310°C, spraying a layer of zircon powder coating on the mold barrel, controlling the mold barrel rotation speed at 75-90 times the acceleration of gravity, injecting the preliminary alloy liquid into the mold barrel, and the casting temperature is 1500-1600°C; (3) collecting the wall thickness data of the steel billet in real time through the laser interference wall thickness measurement module, and the measurement frequency reaches 300-600 times per second; (4) controlling the rotation speed of the mold barrel according to the measurement result of the laser interference wall thickness measurement module, and demolding and drawing the tube to obtain the steel pipe after casting; (5) annealing the steel pipe, the annealing temperature is controlled between 900°C and 1000°C, and the insulation time is 20-30 minutes; (6) cooling is carried out by forced air cooling with a cooling rate of 30°C / s, and pickling and phosphating are carried out after cooling to room temperature.

[0008] Furthermore, in the step (1), the pressure in the vacuum arc furnace is controlled below 0.001Pa. During the smelting process, the slag content of the preliminary alloy liquid obtained by slag removal is less than 0.01%. When smelting in the vacuum arc furnace, the reason for controlling the furnace pressure to below 0.001Pa is to reduce the impurity inclusion phenomenon caused by the residual oxygen, nitrogen or other gases during the alloy smelting process. Under low pressure conditions, the influence of these harmful gases on the molten alloy is effectively suppressed, and the generation of oxides, sulfides and other inclusions in the steel is avoided. Especially when alloy elements with higher purity requirements such as Cr and Mo are present, this low-pressure smelting environment is particularly important. At the same time, the slag content is controlled to be less than 0.01%, which improves the purity of the material, reduces the composition fluctuation, ensures that the mechanical properties and corrosion resistance of the steel pipe are uniform, and meets the high quality requirements of seamless steel pipes used in harsh environments.

[0009] Furthermore, in the step (2), the thickness of the zircon powder coating is 2-3 mm, the pressure during coating spraying is maintained at 0.9 MPa, and the speed of injecting the preliminary alloy liquid into the mold barrel is 30-40 kg / s. The thickness of the zircon powder coating and the coating spraying pressure directly affect the interface quality between the mold barrel surface and the alloy liquid. The thickness of the zircon powder coating is controlled at 2-3 mm to ensure that the mold barrel will not be deformed or cracked due to thermal shock while maintaining sufficient thermal isolation effect. The high melting point and excellent thermal conductivity of zircon powder help to avoid uneven solidification of the alloy liquid on the mold barrel wall. At the same time, the spraying pressure is maintained at 0.9 MPa to ensure the adhesion and uniform distribution of the coating, and to avoid local condensation or microscopic defects during alloy liquid pouring due to uneven coating. In addition, the speed of injecting the alloy liquid into the mold barrel is 30-40 kg / s, which optimizes the fluidity of the liquid alloy and balances the turbulence and cooling effects generated during the pouring process, thereby ensuring uniform molding during the pouring process and reducing defects such as bubbles or uneven solidification.

[0010] Furthermore, during the annealing process, the laser interference wall thickness measurement module will be used to monitor the change in pipe wall thickness, so that the wall thickness deviation does not exceed ±0.03mm. During the annealing process, wall thickness control is one of the key steps to determine the final quality of the seamless steel pipe. The laser interference wall thickness measurement module can monitor the change in pipe wall thickness in real time, and can accurately adjust the temperature distribution and crystal structure transformation of the material during the annealing process, so as to control the wall thickness deviation of the steel pipe within ±0.03mm. This ultra-precision control not only improves the mechanical strength and compressive resistance of the steel pipe, but also ensures the uniformity of the wall thickness of each section of the steel pipe, especially when used for high-pressure transportation and complex working conditions, the safety and reliability of the steel pipe can be significantly improved.

[0011] Furthermore, after step (6), the method further includes the following steps: performing nondestructive testing on each steel pipe, including ultrasonic testing and X-ray testing, to ensure uniformity of wall thickness and absence of internal defects. Nondestructive testing is a necessary step for quality assurance of each steel pipe. The combination of ultrasonic testing and X-ray testing can comprehensively check the internal defects and wall thickness uniformity of the steel pipe. Ultrasonic testing is mainly used to detect pores, inclusions and cracks inside the steel pipe. In particular, high-frequency ultrasonic waves can penetrate thick-walled pipes to detect internal defects, while X-ray testing can further detect uniformity of internal organization and changes in microstructure by comparing different density areas. The application of these nondestructive testing methods ensures that each steel pipe meets high quality standards and avoids early failures caused by internal defects.

[0012] Furthermore, in step (6), the cooling process is segmented cooling, and the cooling rate of each segment is adjusted in real time by an independent control system. The cooling rate of the first segment is 40°C / s, and the cooling rate of the second segment is 25°C / s. The cooling process has a direct impact on the structure and performance of the material. The segmented cooling method enables the steel pipe to obtain the best cooling rate control at different stages. The cooling rate of the first segment is set to 40°C / s, which can quickly reduce the surface temperature of the steel pipe, inhibit excessive grain growth, and ensure the hardness and wear resistance of the surface layer; while the cooling rate of the second segment is 25°C / s. The purpose of slowing down the cooling rate is to balance the temperature gradient of the inner and outer walls, and avoid microcracks caused by excessive thermal stress due to inconsistent cooling rates. In addition, the independent control system adjusts the cooling rate of each segment in real time, further ensuring the uniformity of the internal structure of the steel pipe and the stability of the mechanical properties.

[0013] Furthermore, in the step (1), 0.001%-0.005% by weight of pure argon is added to the alloy liquid after preliminary smelting for gas stirring, and the stirring time is 10-15 minutes. The purpose of adding 0.001%-0.005% by weight of pure argon to the alloy liquid after preliminary smelting for gas stirring is to form a strong stirring effect through the inertness and density of argon, reduce the gas and inclusions in the molten steel, and reduce the oxygen content. Argon stirring can also evenly disperse the elements in the alloy liquid to prevent local oversaturation or uneven composition, especially for the uniform distribution of difficult-to-melt elements, such as Mo and Cr. The stirring time is controlled to 10-15 minutes in order to give full play to the purification effect of argon, while avoiding excessive oxidation or cooling of the alloy liquid due to excessive stirring, which affects the molding quality of the subsequent casting process.

[0014] Beneficial effects: By introducing the laser interference wall thickness measurement module, high-frequency measurement is performed to ensure that the changes in the wall thickness of the steel pipe can be accurately grasped during the manufacturing process, thereby greatly improving the control accuracy of the production process; combined with the precise control of the mold barrel speed, the system can adjust the speed in time according to the measurement results, so that the steel pipe always maintains a uniform wall thickness during the casting process; the optimized cooling control system adopts forced air cooling, which effectively prevents the uneven wall thickness that may be caused during the heat treatment process; in addition, the reasonable raw material ratio not only ensures the strength and toughness of the steel pipe, but also improves the wall thickness accuracy of the finished steel pipe, and finally produces high-quality hot-rolled seamless steel pipes that meet precision requirements; Overall, this solution significantly reduces the wall thickness error of seamless steel pipes, is safer and more durable, increases the plasticity of the thickness of seamless steel pipes, and is more suitable for a diverse market environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The invention is a flow chart of a hot-rolled seamless steel pipe and a wall thickness controllable processing technology thereof. DETAILED DESCRIPTION

[0016] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0017] The present invention provides a hot-rolled seamless steel pipe. The raw material components of the seamless steel pipe are proportioned as follows in weight percentage: C: 0.05%-0.25%, Si: 0.10%-0.50%, Mn: 0.30%-1.20%, P: ≤0.030%, S: ≤0.030%, Cr: 0.40%-1.10%, Mo: 0.10%-0.30%, Ni: 0.10%-0.40%, and the rest are Fe and inevitable impurities. The wall thickness of the seamless steel pipe is 5-20mm.

[0018] Please see Figure 1 The present invention also provides a wall thickness controllable processing technology for hot-rolled seamless steel pipes. The raw material components of the seamless steel pipes are as follows in weight percentage: C: 0.05%-0.25%, Si: 0.10%-0.50%, Mn: 0.30%-1.20%, P: ≤0.030%, S: ≤0.030%, Cr: 0.40%-1.10%, Mo: 0.10%-0.30%, Ni: 0.10%-0.40%, and the rest are Fe and unavoidable impurities. The preparation method thereof comprises the following steps:

[0019] (1) The raw materials are placed in a vacuum arc furnace according to the raw material composition. During the smelting process, the temperature is gradually increased to 1640-1660°C and maintained for at least 25 minutes, and the initial alloy liquid is obtained after slag removal. (2) The mold barrel is preheated at a temperature of 290-310°C, a layer of zircon powder coating is sprayed on the mold barrel, and the mold barrel speed is controlled at 75-90 times the acceleration of gravity. The initial alloy liquid is injected into the mold barrel at a casting temperature of 1500-1600°C. (3) The wall thickness is measured by laser interference. The measuring module collects the wall thickness data of the steel billet in real time, and the measuring frequency reaches 300-600 times per second; (4) the rotation speed of the mold barrel is controlled according to the measurement result of the laser interference wall thickness measuring module, and the steel pipe is demoulded and drawn after casting; (5) the steel pipe is annealed, and the annealing temperature is controlled between 900℃ and 1000℃, and the insulation time is 20-30 minutes; (6) forced air cooling is adopted at a cooling rate of 30℃ / s, and pickling and phosphating are performed after cooling to room temperature; in step (1), the real The pressure in the empty arc furnace is controlled below 0.001Pa. During the smelting process, the slag content of the preliminary alloy liquid obtained by slag removal is less than 0.01%; in step (2), the thickness of the zircon powder coating is 2-3mm, the pressure during coating spraying is maintained at 0.9MPa, and the speed of injecting the preliminary alloy liquid into the mold barrel is 30-40kg / s; in step (5), during the annealing process, the change of the tube wall thickness is also monitored by the laser interference wall thickness measurement module, so that the wall thickness deviation does not exceed ±0.03mm; in step The method further comprises the following steps after step (6): performing nondestructive testing on each steel pipe, including ultrasonic testing and X-ray testing, to ensure uniformity of wall thickness and absence of internal defects; in step (6), the cooling process is segmented cooling, and the cooling rate of each segment is adjusted in real time by an independent control system, the cooling rate of the first segment is 40°C / s, and the cooling rate of the second segment is 25°C / s; and adding 0.001%-0.005% by weight of pure argon gas to the alloy liquid after preliminary smelting for gas stirring, and the stirring time is 10-15 minutes.

[0020] For the purpose of greater clarity, the invention is described in detail through the following examples.

[0021] Embodiment 1:

[0022] The following raw material components are selected and mixed by weight percentage: C: 0.12%, Si: 0.30%, Mn: 0.80%, P: 0.028%, S: 0.028%, Cr: 0.85%, Mo: 0.25%, Ni: 0.30%, and the rest is Fe and unavoidable impurities;

[0023] The raw materials are mixed according to the above ratio and put into a vacuum arc furnace. The pressure in the furnace is controlled at 0.0008Pa. During the smelting process, the temperature is gradually increased to 1650°C and maintained for 25 minutes. The smelting process is treated by efficient slag removal technology to obtain a preliminary alloy liquid. Pure argon gas with a weight ratio of 0.004% is added to the alloy liquid after preliminary smelting for gas stirring. The stirring time is 10-15 minutes, so that the slag content is controlled to be less than 0.008%;

[0024] The mold barrel is preheated before use, and the preheating temperature is controlled at 300℃. At the same time, a layer of zircon powder coating with a thickness of 2.5mm is sprayed on the inner wall of the mold barrel. The coating spraying pressure is maintained at 0.9MPa to ensure that the coating is evenly attached to the surface of the mold barrel to prevent the mold barrel from cracking due to thermal shock during the subsequent high-temperature pouring process;

[0025] The preliminary alloy liquid is injected into the mold barrel at a speed of 35kg / s, the casting temperature is controlled at 1550℃, and the rotation speed of the mold barrel is regulated at 85 times the acceleration of gravity, so that the alloy liquid is evenly distributed in the mold barrel and quickly formed;

[0026] The laser interference wall thickness measurement module collects the billet wall thickness data in real time, and the measurement frequency is set to 400 times per second. According to the measurement results, the system automatically adjusts the rotation speed of the mold barrel to ensure that the wall thickness is within the design requirements and the deviation does not exceed ±0.03mm;

[0027] After the steel pipe is formed, it is annealed at a temperature of 950°C and a holding time of 25 minutes. During the annealing process, the laser interferometer wall thickness measurement module continuously monitors the change in the wall thickness of the steel pipe to ensure that the wall thickness change caused by thermal expansion and contraction during the annealing stage is within the allowable range;

[0028] After annealing, the steel pipe is cooled in sections. The cooling rate of the first section is controlled at 40℃ / s, and the cooling rate of the second section is 25℃ / s. The cooling rate of each section is adjusted in real time through an independent control system. After cooling to room temperature, pickling and phosphating treatment are carried out to improve the corrosion resistance of the steel pipe surface.

[0029] After the steel pipe is cooled, it is subjected to non-destructive testing by combining ultrasonic testing and X-ray testing. Ultrasonic testing is used to detect pores and inclusions inside the steel pipe, while X-ray testing is used to confirm the uniformity of the internal structure of the steel pipe to ensure that each steel pipe is defect-free.

[0030] After testing, the steel pipe has excellent wall thickness uniformity, the deviation is controlled within ±0.02mm, there are no obvious defects on the surface of the steel pipe, the internal structure is dense, and the final product has good mechanical strength, corrosion resistance and high-pressure performance, which is suitable for high-demand application fields such as oil pipelines and pressure vessels. Through the production process of this embodiment, hot-rolled seamless steel pipes with uniform wall thickness and stable performance are successfully manufactured, especially with excellent performance in wall thickness control, meeting the market demand for high-precision seamless steel pipes.

[0031] Embodiment 2:

[0032] This embodiment further optimizes the wall thickness controllable processing technology of hot-rolled seamless steel pipes, and improves the precision and stability of steel pipe production by refining process steps and adjusting parameters. The specific implementation steps are as follows:

[0033] The following raw material components are selected and mixed by weight percentage: C: 0.15%, Si: 0.20%, Mn: 0.60%, P: 0.020%, S: 0.020%, Cr: 0.75%, Mo: 0.15%, Ni: 0.25%, and the rest is Fe and unavoidable impurities;

[0034] The raw materials were mixed according to the above ratio and put into a vacuum arc furnace. The pressure in the furnace was maintained at 0.0005Pa. During the smelting process, the temperature was gradually increased to 1645°C and maintained for 30 minutes. During the smelting process, high-efficiency slag removal technology was used to ensure that the slag content was less than 0.005%. 0.003% pure argon was added to the alloy liquid for gas stirring for 12 minutes to further remove gas inclusions and improve melt uniformity.

[0035] The mold barrel is preheated at 305°C, and a 2.8mm thick zircon powder coating is sprayed on the inner wall of the mold barrel. The pressure during spraying is controlled at 1.0MPa to ensure the uniformity and integrity of the coating, and the mold barrel speed is set to 80 times the acceleration of gravity;

[0036] The preliminary alloy liquid is injected into the mold barrel at a speed of 32kg / s, the casting temperature is maintained at 1525℃, and the speed of the mold barrel is automatically adjusted during the casting process to achieve optimal billet flow and uniform forming;

[0037] The laser interference wall thickness measurement module is used to collect the billet wall thickness data in real time. The measurement frequency is set to 350 times per second. According to the measurement data, the mold barrel speed is automatically adjusted to maintain the stability of the wall thickness, ensuring that the deviation does not exceed ±0.02mm.

[0038] The formed steel pipe is annealed in the annealing furnace at a temperature of 925°C for 25 minutes. During the annealing process, the tube wall thickness is monitored by the laser interferometer wall thickness measurement module to ensure that the wall thickness deviation is kept within the range of ±0.02mm during the annealing process;

[0039] After annealing, the steel pipe is cooled in sections, with the cooling rate of the first section at 35°C / s and the cooling rate of the second section at 20°C / s. After cooling to room temperature, it is pickled and phosphated to ensure that there is no oxide layer and impurities on the surface of the steel pipe, and to improve the corrosion resistance and surface finish of the steel pipe.

[0040] After the steel pipe is cooled, it is subjected to comprehensive non-destructive testing, including ultrasonic testing and X-ray testing. Ultrasonic testing is used to detect internal pores and inclusions, and X-ray testing is used to confirm the uniformity of the internal organizational structure. Through these two testing methods, it is ensured that the internal quality of the steel pipe meets the standard requirements;

[0041] During the inspection, the uniformity of the wall thickness of the steel pipe was controlled within ±0.015mm, the internal structure was dense and without obvious defects, and the surface was smooth. The product is suitable for demanding structural parts and high-pressure application fields, such as oil and gas pipelines and high-pressure containers; through the process improvement of this embodiment, the wall thickness control accuracy and production stability of the hot-rolled seamless steel pipe are further improved, ensuring the reliability and service life of the final product under high load and high pressure environments.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A hot rolled seamless steel pipe, characterized in that: The raw material components of the seamless steel pipe are arranged in the following proportions by weight: C: 0.05%-0.25%, Si: 0.10%-0.50%, Mn: 0.30%-1.20%, P: ≤0.030%, S: ≤0.030%, Cr: 0.40%-1.10%, Mo: 0.10%-0.30%, Ni: 0.10%-0.40%, and the rest are Fe and unavoidable impurities. The wall thickness of the seamless steel pipe is 5-20mm.

2. A wall thickness controllable processing technology for hot-rolled seamless steel pipe, used to realize a hot-rolled seamless steel pipe as claimed in claim 1, characterized in that The raw material components of the seamless steel pipe are proportioned as follows by weight percentage: C: 0.05%-0.25%, Si: 0.10%-0.50%, Mn: 0.30%-1.20%, P: ≤0.030%, S: ≤0.030%, Cr: 0.40%-1.10%, Mo: 0.10%-0.30%, Ni: 0.10%-0.40%, and the rest is Fe and inevitable impurities. The preparation method comprises the following steps: (1) according to the raw material components, the raw materials are placed in a vacuum arc furnace. During the smelting process, the temperature is gradually increased to 1640-1660°C and maintained for at least 25 minutes, and a preliminary alloy liquid is obtained after slag removal treatment; (2) the mold barrel is preheated and pre- The hot temperature is controlled at 290-310°C, a layer of zircon powder coating is sprayed on the mold barrel, the mold barrel rotation speed is controlled at 75-90 times the acceleration of gravity, the preliminary alloy liquid is injected into the mold barrel, and the casting temperature is 1500-1600°C; (3) the wall thickness data of the steel billet is collected in real time through the laser interference wall thickness measurement module, and the measurement frequency reaches 300-600 times per second; (4) the rotation speed of the mold barrel is controlled according to the measurement result of the laser interference wall thickness measurement module, and the steel pipe is demoulded and drawn after casting; (5) the steel pipe is annealed, the annealing temperature is controlled between 900°C and 1000°C, and the insulation time is 20-30 minutes; (6) forced air cooling is adopted with a cooling rate of 30°C / s, and pickling and phosphating are carried out after cooling to room temperature.

3. A wall thickness controllable processing technology for hot-rolled seamless steel pipe according to claim 2, characterized in that: In the step (1), the pressure in the vacuum arc furnace is controlled below 0.001 Pa, and during the smelting process, the slag content of the preliminary alloy liquid obtained by slag removal is less than 0.01%.

4. A wall thickness controllable processing technology for hot-rolled seamless steel pipe according to claim 2, characterized in that: In the step (2), the thickness of the zircon powder coating is 2-3 mm, the pressure during coating spraying is maintained at 0.9 MPa, and the speed of injecting the initial alloy liquid into the mold barrel is 30-40 kg / s.

5. The wall thickness controllable processing technology of hot-rolled seamless steel pipe according to claim 2, characterized in that: In the step (5), during the annealing process, the change in tube wall thickness is also monitored by a laser interferometer wall thickness measurement module to ensure that the wall thickness deviation does not exceed ±0.03 mm.

6. A wall thickness controllable processing technology for hot-rolled seamless steel pipe according to claim 2, characterized in that: After step (6), the method further includes: performing nondestructive testing on each steel pipe, including ultrasonic testing and X-ray testing, to ensure uniformity of wall thickness and absence of internal defects.

7. The wall thickness controllable processing technology of hot-rolled seamless steel pipe according to claim 2, characterized in that: In the step (6), the cooling process is segmented cooling, and the cooling rate of each segment is adjusted in real time by an independent control system. The cooling rate of the first segment is 40°C / s, and the cooling rate of the second segment is 25°C / s.

8. The wall thickness controllable processing technology of hot-rolled seamless steel pipe according to claim 2, characterized in that: In the step (1), 0.001% to 0.005% by weight of pure argon gas is added to the alloy liquid after preliminary smelting for gas stirring, and the stirring time is 10 to 15 minutes.

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