Processing and manufacturing method of HR3C extra-thick seamless tube for power station superheater

Abstract

The invention belongs to the field of seamless tube machining, and relates to a machining and manufacturing method of an HR3C extra-thick seamless tube for a power station superheater. According to the technical scheme, the method comprises the steps of round steel perforating, surface cleaning, pierced billet cold rolling, heat treatment and degreasing treatment. After the round steel is heated to 1200 DEG C, a perforating machine is adopted for perforating, in the perforating process, the included angle between the center of a perforating roller and the center of the roller is 8 degrees, the rolling speed is 260-270 r / min, and the pierced billet is prepared. Straightening and pickling the pierced billet, and cleaning surface defects. And rolling the pierced billet by adopting a cold pilger mill, wherein the ratio of the diameter of the large head of a core rod of the cold pilger mill to the diameter of the sizing section is 1-2.5. And the cold-rolled pierced billet is subjected to degreasing treatment. And carrying out heat treatment on the degreased pierced billet. The method for perforating the round steel further comprises the steps that the round steel is heated to 1200 + / -10 DEG C, and the heating time is kept for 6 hours.

Description

Technical Field

[0001] The invention belongs to the field of seamless pipe processing and relates to a processing and manufacturing method of an HR3C extra-thick seamless pipe for a power station superheater. Background Art

[0002] HR3C (25Cr-20Ni-Nb-N) steel is a new type of austenitic heat-resistant steel successfully developed by adding 0.2-0.6% Nb and 0.15-0.35% N to 25Cr-20N TP310H steel, and improving the creep strength of the material through solid solution strengthening and precipitation strengthening. In particular, the precipitation strengthening effect of carbides and Nb carbonitrides precipitated during service increases the creep rupture strength of the material to 181MPa. When the metal wall temperature is 650℃, its high-temperature endurance strength can reach about twice that of TP310H. HR3C extra-thick seamless steel pipes are mainly used in final superheaters and thick frequency superheaters to meet the higher pressure requirements of final superheaters and thick frequency superheaters, and to manufacture high-temperature superheater and reheater components with a manufacturing temperature not exceeding 700℃. The high strength and hardness of HR3C material make it difficult to make perforation, cold rolling, heat treatment and other processes in the pipe making process, especially the production process of extra-thick seamless pipe (wall diameter between 2-3) introduced in this patent, which makes the pipe making process even more difficult. HR3C composition:

[0003] Table 1 HR3C composition

[0004]

[0005] At present, the diameter-to-wall ratio of HR3C pipe products is mainly concentrated between 3 and 20. However, the thick-walled seamless finished pipe with a diameter-to-wall ratio of less than 3 exceeds the equipment capacity and has been mainly processed by multi-pass cold drawing. 17mm and other specifications. Due to the high pressure development of ultra-supercritical power station boilers, extra-thick seamless steel pipes have become their must-have products. Multi-pass cold drawing not only has a long processing route, but also has a low yield rate due to the large number of passes, and the performance cannot be guaranteed due to the large grain difference caused by multi-pass heat treatment. Therefore, the development of extra-thick seamless steel pipe technology is a common goal of users and our company. This product has basic characteristics that are different from ordinary specifications, such as its small diameter-to-wall ratio, large weight per meter of steel pipe, small inner hole of steel pipe, and extra-thick wall thickness. In particular, the use of tools and dies in the production process exceeds the limit and exceeds the equipment capacity, which brings difficulties to the development of this product.

[0006] Taking into account the extremely poor wall thickness and grain size of the superheater of the thermal power unit, the requirements for mechanical properties, the existing equipment capabilities and the fact that the existing processes are not available for reference, this production process is developed. The production process design of the ultra-thick seamless steel pipe with a diameter-to-wall ratio of HR3C pipe less than 3 is: perforation + two cold rolling + one cold drawing.

[0007] The method of the invention solves the problems of the perforation process of ultra-thick rough pipes with small deformation in the production process, the difficulty of ultra-thick pipes being unable to be directly rolled into finished products, and the problem of uneven grains of ultra-thick pipes during heat treatment. Summary of the invention

[0008] In order to overcome the defects in the above-mentioned related technologies, the present invention proposes a method for processing and manufacturing HR3C extra-thick seamless pipes for power station superheaters. The processing and manufacturing method of HR3C extra-thick seamless pipes for power station superheaters is suitable for extra-thick seamless pipes processed with HR3C stainless steel. The processing and manufacturing method of HR3C extra-thick seamless pipes for power station superheaters includes: perforating round steel, cleaning the surface, cold rolling the rough pipe, heat treatment, and degreasing. After heating the round steel to 1200°C, a perforator is used for perforation. During the perforation process, the perforating roller and the roller center angle are 8°, and the rolling speed is 260-270 rpm to prepare the rough pipe. The rough pipe is straightened and pickled, and the surface defects are cleaned. The rough pipe is rolled by a cold rolling mill, wherein the ratio of the big head diameter of the mandrel of the cold rolling mill to the diameter of the sizing section is 1 to 2.5. The cold-rolled rough pipe is degreased. The degreased rough pipe is heat treated.

[0009] The method for perforating round steel further comprises: heating the round steel to 1200±10° C. and maintaining the heating time for 6 hours.

[0010] The cold rolling of the rough pipe also includes:

[0011] The first cold rolling is performed by a cold rolling mill, wherein the ratio of the diameter of the mandrel of the cold rolling mill to the diameter of the sizing section is 1 to 2.5;

[0012] The second cold rolling is performed by a cold rolling mill, and the ratio of the big end diameter of the mandrel of the cold rolling mill to the sizing section diameter in the second cold rolling is 1 to 2.5.

[0013] The rolling speed of the cold rolling tube mill is 30 times / min, and the feed amount is 3-3.5 mm.

[0014] After the rough pipe is cold-rolled, the manufacturing method of the HR3C extra-thick seamless pipe for a power station superheater further comprises drawing the rough pipe after cold rolling.

[0015] The cold rolling of the rough pipe also includes:

[0016] After the first cold rolling, the rough pipe is heat treated, wherein the rough pipe is heat treated after the first cold rolling, wherein the rough pipe is heated to 1220±15° C. and kept at this temperature for 55±2 minutes;

[0017] The rough pipe is heat treated after the second cold rolling, and the process of heat treating the rough pipe after the second cold rolling includes heating the rough pipe to 1200±15° C. and keeping the temperature for 52±2 minutes.

[0018] The manufacturing method of the HR3C extra-thick seamless pipe for the power station superheater further comprises: after the cold-rolled rough pipe is drawn once, the manufacturing method of the HR3C extra-thick seamless pipe for the power station superheater further comprises: heat-treating the rough pipe after the cold-rolling, and the heat-treating process for the rough pipe after the cold-rolling once comprises: heating the rough pipe to 1200±15℃ and keeping it warm for 50±2min

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention provides a method for processing and manufacturing high-nickel alloy HR3C extra-thick seamless steel pipes, providing a solution when the equipment manufacturing capacity is insufficient. The extra-thick pipes produced meet the requirements of boiler power stations for higher temperatures and higher pressures. At the same time, the technical difficulties of processing and manufacturing high-nickel alloy HR3C extra-thick seamless steel pipes, such as the wall thickness cannot be controlled (there is a wall reduction phenomenon in the drawing of thick-walled pipes) and the extremely poor grain of the finished product, are solved, and the machining amount of extra-thick pipes is effectively reduced. The performance fully meets the national standard requirements and the design requirements of power station boilers.

[0021] 2. The invention adjusts the perforation roller speed from the original 300-320 rpm to 260-270 rpm, reduces the roller speed to reduce the round steel rotation speed, improves the alignment between the perforation head and the round steel, reduces the occurrence of wall deviation, and stabilizes the perforation. If the roller speed is too low, it is easy to cause the round steel temperature to drop too much during the perforation process, affecting the perforation quality.

[0022] Reduce the angle between the piercing roller and the center of the roller from the original 12° to 8°, reduce the angle of the roller, reduce the feeding speed of the round steel during the piercing process, greatly reduce the rolling force, stabilize the push rod, and improve the centering.

[0023] By taking the above measures, the small defect of the perforation ejector rod is solved, and at the same time, the quality problem of the perforation wall deviation is solved, and the wall deviation is less than 1.5mm.

[0024] For round steel with the same specifications, the specifications of the rough pipe after perforation are different, the elongation is inconsistent, and the deformation heat generated during the deformation process is also inconsistent, so the heating temperature of the round steel is uncertain. For perforation of Φ114*22mm small deformation specifications, it is necessary to re-determine the perforation temperature and heating time to solve quality problems such as perforation carding and internal cracking.

[0025] 3. The piercing temperature of the present invention is 1200±10°C and the heating time is 6 hours. The rolling is stable, the piercing mandrel runs smoothly, and there is no problem with the quality of the inner and outer surfaces.

[0026] After testing, the piercing temperature was 1170±15℃ and the heating time was 5 hours. The piercing process was difficult to bite into the hole, the rolling was unstable, and the core rod was bent. The temperature of the round steel measured during the piercing process reached 30°, which was greater than the temperature drop of ordinary specifications. The piercing temperature was 1220±10℃ and the heating time was 6 hours. The piercing bit normally, the rolling was stable, and the piercing mandrel ran smoothly, but internal cracks occurred on the inner surface, and the internal crack ratio reached 12%.

[0027] 4. The present invention designs a core rod for a rough pipe and performs multiple cold rolling to avoid multiple drawing processes. It can also avoid the situation where the grains vary greatly and the performance cannot be guaranteed due to multiple heat treatments after multiple drawing.

[0028] 5. The present invention adopts a one-time drawing process. In the ordinary drawing process, the wall thickness will increase. The wall thickness reduction of 1mm in the empty drawing process does not occur in the actual production process. This process reduces the wall thickness by one drawing to 17.3-17.7mm, which meets the tolerance requirements of the finished product. If the drawing is two or more passes, the wall thickness of the finished product is not enough to meet the tolerance requirements. The multi-pass drawing of HR3C extra-thick tubes cannot control the wall thickness and complete mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a surface diagram of a rough pipe when the rolling speed is 55 times / min and the feed amount is 2.5 mm in the rough pipe cold rolling process of the present invention;

[0031] Figure 2 This is a cross-sectional view of a rough pipe after a single cold drawing of the present invention;

[0032] Figure 3 The present invention is a grain map of the outer surface of a rough tube after a single cold drawing;

[0033] Figure 4 The present invention is a grain map of the inner surface of a rough tube after a single cold drawing;

[0034] Figure 5 This is a cross-sectional view of the seamless steel pipe that has undergone multiple cold drawing in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0036] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0038] Example 1

[0039] The specific manufacturing process of this application includes the following steps:

[0040] Punch holes in Φ110mm round steel to prepare Φ114*22mm rough pipes.

[0041] The Φ114*22mm rough pipe is subjected to the first cold rolling operation to prepare a Φ89*19mm rough pipe.

[0042] The Φ89*19mm rough pipe is subjected to a second cold rolling operation to prepare a Φ57*18mm rough pipe.

[0043] The Φ57*18mm rough pipe is subjected to a single cold drawing operation to prepare a Φ51*18mm seamless steel pipe.

[0044] The following is an explanation of the technical difficulties of the main key processes and the key quality control points:

[0045] 1. Perforation

[0046] The Φ114*22mm high nickel alloy HR3C has a large piercing rolling force, but the ejector rod uses a Φ60 specification. The Φ60 ejector rod is used for the specification of Φ65 outer diameter of the perforation, which breaks the limit of the tooling. The smaller the perforation tip, the more unstable the perforation process, causing the ejector rod to bend, the ejector head and the round steel to be unable to be aligned, and the perforated rough pipe to be seriously deviated from the wall.

[0047] Measures to be taken:

[0048] Adjust the perforation roller speed from the original 300-320 rpm to 260-270 rpm. Reduce the roller speed to reduce the round steel rotation speed, improve the alignment between the perforation head and the round steel, reduce the occurrence of wall deviation, and stabilize the perforation. If the roller speed is too low, it is easy to cause the round steel temperature to drop too much during the perforation process, affecting the perforation quality.

[0049] Reduce the angle between the piercing roller and the center of the roller from the original 12° to 8°, reduce the angle of the roller, reduce the feeding speed of the round steel during the piercing process, greatly reduce the rolling force, stabilize the push rod, and improve the centering.

[0050] By taking the above measures, the small defect of the perforation ejector rod is solved, and at the same time, the quality problem of the perforation wall deviation is solved, and the wall deviation is less than 1.5mm.

[0051] For round steel with the same specifications, the specifications of the rough pipe after perforation are different, the elongation is inconsistent, and the deformation heat generated during the deformation process is also inconsistent, so the heating temperature of the round steel is uncertain. For perforation of Φ114*22mm small deformation specifications, it is necessary to re-determine the perforation temperature and heating time to solve quality problems such as perforation carding and internal cracking.

[0052] Table 2 Comparison of perforation deformation

[0053]

[0054] Perforation temperature test:

[0055] The first piercing temperature was 1170±15℃ and the heating time was 5 hours. During the piercing process, the piercing was difficult to bite into, the rolling was unstable, and the core rod was bent. During the piercing process, the temperature of the round steel reached 30°, which was larger than the temperature drop of ordinary specifications.

[0056] The second piercing temperature was 1200±10℃ and the heating time was 6 hours. The piercing bit normally, the rolling was stable, the piercing ejector rod ran smoothly, and there was no problem with the quality of the inner and outer surfaces.

[0057] The third piercing temperature was 1220±10℃ and the heating time was 6 hours. The piercing bit normally, the rolling was stable, and the piercing mandrel ran smoothly, but internal cracks occurred on the inner surface, and the proportion of internal cracks reached 12%.

[0058] The piercing temperature of HR3C small deformation thick wall pipe is controlled at 1200±10° and the heating time is 6 hours. The given piercing temperature range is small. The higher piercing temperature ensures that the temperature of the steel pipe after piercing is above the solid solution temperature, which improves the mechanical properties of the rough pipe cold rolling.

[0059] 2. Cold rolling process

[0060] The first cold rolling: rolling the Φ114*22mm rough pipe into 89*18.5mm rough pipe.

[0061] The second cold rolling: the Φ89*19mm rough pipe is rolled into a Φ57*18.5mm rough pipe.

[0062] Table 3 Comparison of cold rolled inner diameter and core rod

[0063]

[0064]

[0065] The following measures are taken to address problems such as mismatch between steel pipes and tools, insufficient wall reduction, and core rod curve design.

[0066] Measures to be taken:

[0067] The specification of the mandrel bar declared for the first cold rolling is Φ114*22-Φ89*18.5, ensuring that the inner diameter of the steel pipe after cold rolling is Φ52mm, which can meet the minimum gap requirement of 3mm for the mandrel bar of the next rolling, and the steel pipe can pass through the mandrel bar for rolling to meet the process design requirements. It is also necessary to ensure that the wall thickness of the semi-finished product is greater than the wall thickness of the finished product, otherwise it cannot be rolled. In the actual production process, the outer diameter of the cold rolling is adjusted to Φ88.7~88.8mm, and the position of the mandrel is adjusted backward to ensure that the wall thickness meets the requirement of 19mm, ensuring that the finished product is rolled normally with reduced wall thickness.

[0068] The second cold rolling mandrel is designed according to Φ89*19-Φ57*18, which can ensure that the ratio of the mandrel head diameter to the sizing section diameter is less than 2.5, and the mandrel curve design is no problem, and can be rolled normally. In the actual rolling process, the cold rolling outer diameter is adjusted to Φ57.6-57.8mm, and the mandrel position is adjusted backward to ensure that the cold rolling wall thickness is ≧18.3mm, ensuring that the wall thickness of the finished product can meet the tolerance requirements even if the wall thickness is reduced during the drawing process.

[0069] For the high rolling speed and small feed rolling parameters during the cold rolling process of HR3C extra-thick seamless pipe, the large rolling speed and small feed parameters mean that the pipe is rolled more frequently and more times within the unit length of the mandrel, which can easily cause HR3C cold rolling hardening, poor cold rolling plasticity, and defects such as surface transverse cracks and surface cracks.

[0070] Measures to be taken:

[0071] Low rolling speed and high feed can reduce the number of rolling times per unit length of the pipe, reduce work hardening, and reduce surface cracking.

[0072] Adjusting the heat treatment process of semi-finished products and changing the mechanical properties of HR3C semi-finished products are beneficial to cold deformation.

[0073] Table 4 Comparison of cold rolling parameters

[0074]

[0075] 3. Drawing process

[0076] The Φ57*18.5mm rough pipe is cold drawn into a Φ51*18mm seamless steel pipe in one pass.

[0077] HR3C extra-thick (tube diameter-to-wall ratio ≤ 5) seamless steel pipe drawing will cause wall reduction. By testing this process, the following wall thickness changes were obtained. In the ordinary specification drawing process, the wall thickness will increase, and the wall thickness reduction of 1mm in the empty drawing process does not occur in the actual production process. This process reduces the wall thickness by one drawing to 17.3-17.7mm, which meets the tolerance requirements of the finished product. If the drawing is done in two passes, the wall thickness of the finished product is not enough to meet the tolerance requirements. The HR3C extra-thick pipe cannot control the wall thickness by multiple drawing passes to complete mass production.

[0078] Table 5: Wall thickness variation

[0079]

[0080] 4. Heat treatment process

[0081] The heat treatment process is mainly to ensure that the cold working performance of the semi-finished product and the mechanical properties and grain range of the finished product meet the requirements. The following is a heat treatment process system designed according to the different deformation amounts and heat treatment purposes of each pass.

[0082] Table 3 Comparison of cold rolled inner diameter and core rod

[0083]

[0084] Measures to be taken:

[0085] The high temperature and long holding time of heat treatment after the first cold rolling are to solve the mechanical properties of the next cold rolling, reduce the yield strength and tensile strength of HR3C material, and improve the elongation.

[0086] The total deformation of the second cold rolling is larger, but the wall reduction is smaller and the diameter reduction is larger, resulting in inconsistent wall thickness deformation in the radial direction of the steel pipe and different grain breakage. Lowering the heat treatment temperature and shortening the insulation time can solve the technical problem of the final finished product grain range greater than 3, and can also meet the mechanical property requirements of HR3C with small air drawing deformation.

[0087] In the third pass of empty drawing, due to the small diameter-to-wall ratio of the pipe, the drawing deformation is as the pipe is pulled out. The steel pipe contacts the outer die with the outer metal layer to generate friction, which is subject to large resistance and slow metal flow, resulting in inconsistent metal flow speed in the radial direction and wall reduction. In addition, the change in the grain of the outer layer of the wall thickness is greater than that of the inner layer of the wall thickness. It is necessary to adjust the heat treatment temperature and actual to ensure the extreme grain of the finished product after heat treatment.

[0088] After the implementation of the method of the invention, not only a Φ51*18mm thick-walled tube that meets the requirements is obtained, but also the wall thickness is uniform, the inner and outer surfaces are smooth and consistent, the dimensional accuracy is high, the yield rate reaches more than 87%, and at the same time, the grain size of the inner and outer surfaces after heat treatment is uniform, the extreme difference is small, and the design requirements are met.

[0089] Comparative Example 1

[0090] Use multi-pass drawing to produce 51*18mm tube multi-pass process:

[0091] Punch holes in Φ110mm round steel;

[0092] Multiple drawing operations are performed, and each drawing operation forms the following rough pipes in sequence: Φ104*20mm rough pipe, Φ94*18 rough pipe, Φ84*18 rough pipe, Φ74*18mm rough pipe, Φ65*17.8mm rough pipe, Φ60*17mm rough pipe, Φ55*(16.5-17)mm rough pipe, and Φ51*(16.5-17)mm rough pipe.

[0093] The multi-pass drawing process cannot accurately meet the wall thickness requirement of 18mm, and can only achieve a negative difference, and the pass rate is low.

[0094] At the same time, the inner and outer surfaces are rough after cold rolling, the grains always extend in a single direction, and the mechanical properties are unstable. Due to multiple cold drawing, multiple heat treatments are inevitably used for softening, so multiple heat treatments cause large grain differences. The inner surface is rough, and it is very easy to cause the inner hole to be not cleanly pickled after heat treatment. After cold drawing, the surface defects increase, which increases the repair and rework. The comprehensive yield rate is less than 70%.

[0095] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0096] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for processing and manufacturing HR3C extra-thick seamless pipes for power station superheaters, which is suitable for extra-thick seamless pipes processed from HR3C stainless steel, and is characterized in that: The manufacturing method of the HR3C extra-thick seamless pipe for a power station superheater comprises: The round steel is perforated by heating the round steel to 1200°C and then perforating it with a perforator. During the perforation process, the angle between the perforating roller and the center of the roller is 8°, and the rolling speed is 260-270 rpm to prepare a rough pipe. Surface cleaning, straightening and pickling of rough pipes, and cleaning of surface defects; Cold rolling of the rough pipe, using a cold rolling mill to roll the rough pipe, wherein the ratio of the big end diameter of the mandrel of the cold rolling mill to the diameter of the sizing section is 1-2.5; Degreasing treatment: degreasing the cold-rolled rough pipe; Heat treatment: heat treatment of the degreased rough pipe.

2. The method for processing and manufacturing HR3C extra-thick seamless pipe for power station superheater according to claim 1, characterized in that: The method for perforating round steel further comprises: heating the round steel to 1200±10° C. and maintaining the heating time for 6 hours.

3. The method for processing and manufacturing HR3C extra-thick seamless pipe for power station superheater according to claim 2, characterized in that: The cold rolling of the rough pipe also includes: The first cold rolling is performed by a cold rolling mill, wherein the ratio of the diameter of the mandrel of the cold rolling mill to the diameter of the sizing section is 1 to 2.5; The second cold rolling is performed by a cold rolling mill, and the ratio of the big end diameter of the mandrel of the cold rolling mill to the sizing section diameter in the second cold rolling is 1 to 2.

5.

4. The method for processing and manufacturing HR3C extra-thick seamless pipe for power station superheater according to claim 3, characterized in that: The rolling speed of the cold rolling mill is 30 times / min, and the feed amount is 3-3.5 mm.

5. The method for processing and manufacturing HR3C extra-thick seamless pipe for power station superheater according to claim 4, characterized in that: After the rough pipe is cold-rolled, the manufacturing method of the HR3C extra-thick seamless pipe for a power station superheater further comprises drawing the rough pipe after cold rolling.

6. The method for processing and manufacturing HR3C extra-thick seamless pipe for power station superheater according to claim 5, characterized in that: The cold rolling of the rough pipe also includes: After the first cold rolling, the rough pipe is heat treated, wherein the rough pipe is heat treated after the first cold rolling, wherein the rough pipe is heated to 1220±15° C. and kept at this temperature for 55±2 minutes; The rough pipe is heat treated after the second cold rolling, and the process of heat treating the rough pipe after the second cold rolling includes heating the rough pipe to 1200±15° C. and keeping the temperature for 52±2 minutes.

7. The method for processing and manufacturing HR3C extra-thick seamless pipe for power station superheater according to claim 6, characterized in that: The processing and manufacturing method of the HR3C extra-thick seamless pipe for power station superheater also includes: after drawing the cold-rolled rough pipe once, the processing and manufacturing method of the HR3C extra-thick seamless pipe for power station superheater also includes: heat treating the once cold-drawn rough pipe, and the heat treatment process of the once cold-drawn rough pipe includes: heating the rough pipe to 1200±15℃ and keeping it warm for 50±2min.

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