Thickened sleeve for steel pipe, method for heat treating the same and use thereof

Abstract

This application discloses a thickened steel pipe sleeve, its heat treatment method, and its application, belonging to the field of metallic materials technology. The method includes: subjecting the thickened sleeve forming part to a first-heated sleeve by quenching at a temperature of 880-900℃; subjecting the first-heated sleeve to a first-water quenching to obtain a first-water-quenched sleeve; subjecting the first-water-quenched sleeve to a second-heated quenching at a temperature of 920-940℃; subjecting the second-water-quenched sleeve to a second-water quenching to obtain a second-water-quenched sleeve; cooling the primary and secondary sleeve bodies with external spraying and internal spraying, and cooling the thickened end with external spraying, internal spraying, and supplementary water; the external spraying flow rate is 2800-3200 m³ / h; the internal spraying flow rate is 1000-1500 m³ / h; and the supplementary water flow rate is 400-600 m³ / h. 3 / h; The secondary heating and tempering treatment of the sleeve yields a thickened steel pipe sleeve. The yield strength and tensile strength deviation of the tube body and the thickened end of the thickened sleeve after heat treatment in this application are ≤30MPa.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal materials, in particular to a steel pipe thickened casing pipe, a heat treatment method thereof and application. BACKGROUND

[0002] The thickened casing pipe is a key component for building oil and gas wellbore, which improves the threaded connection strength to more than 90% of the pipe body tensile strength by locally thickening the pipe end, effectively solving the industry problem of easy fracture of the connection part of the conventional flat-end casing pipe in deep wells, ultra-deep wells and complex working conditions. However, the thickened end wall thickness is usually 1.4-1.7 times of the pipe body, which poses a severe challenge to the heat treatment process due to the significant cross-section difference.

[0003] The existing technology generally adopts the quenching and tempering process of "one-time quenching + one-time tempering". Under this process, the cooling speed of the thickened end with larger wall thickness in the quenching process is much lower than that of the pipe body, which makes it difficult to be fully quenched, and non-martensitic structures such as bainite are easily formed in the microstructure. As a result, the mechanical properties (such as yield strength and tensile strength) of the thickened end are often lower than those of the pipe body, and this performance inconsistency directly affects the overall safety and reliability of the casing pipe in use. SUMMARY

[0004] The main purpose of the present application is to provide a thickened casing pipe and a heat treatment method and application thereof, so as to solve the problem of low mechanical properties of the thickened casing pipe in the prior art, and the inconsistent mechanical properties of the thickened end and the pipe body, which further leads to a great safety problem of the overall casing pipe in use.

[0005] In order to achieve the above purpose, according to one aspect of the present application, a heat treatment method of a steel pipe thickened casing pipe is provided, which comprises the following steps:

[0006] Step S1: one-time quenching heating is performed on the steel pipe thickened casing pipe forming piece to obtain a one-time heated casing pipe; wherein the temperature of the one-time quenching heating is 880-900℃;

[0007] Step S2: one-time water quenching is performed on the one-time heated casing pipe to obtain a one-time water quenched casing pipe; wherein the pipe body of the one-time heated casing pipe is cooled by the first outer spraying I and the first inner spraying I; the thickened end of the one-time heated casing pipe is cooled by the first outer spraying II, the first inner spraying II and the first outer surface water supplementing;

[0008] Step S3: two-time quenching heating is performed on the one-time water quenched casing pipe to obtain a two-time heated casing pipe; wherein the temperature of the two-time quenching heating is 920-940℃;

[0009] Step S4: secondary water quenching is performed on the secondary heating sleeve pipe to obtain a secondary water quenching sleeve pipe; wherein the pipe body of the secondary heating sleeve pipe is cooled by the second outer spraying I and the second inner spraying I; the thickened end of the secondary heating sleeve pipe is cooled by the second outer spraying II, the second inner spraying II and the second outer surface water supplement;

[0010] The spraying flow rates of the first outer spraying I, the first outer spraying II, the second outer spraying I and the second outer spraying II are respectively 2800-3200 m 3 / h; the spraying flow rates of the first inner spraying I, the first inner spraying II, the second inner spraying I and the second inner spraying II are respectively 1000-1500 m 3 / h; the flow rates of the first outer surface water supplement and the second outer surface water supplement are both 400-600 m 3 / h;

[0011] Step S5: tempering treatment is performed on the secondary heating sleeve pipe to obtain a final steel pipe thickened sleeve pipe.

[0012] Further, in step S2, the cooling speed of the pipe body of the primary heating sleeve pipe is 15-25 ℃ / s, and the cooling speed of the thickened end of the primary heating sleeve pipe is 9-14 ℃ / s.

[0013] Further, in step S4, the cooling speed of the pipe body of the secondary heating sleeve pipe is 15-25 ℃ / s, and the cooling speed of the thickened end of the secondary heating sleeve pipe is 9-14 ℃ / s.

[0014] Further, the material of the steel pipe thickened sleeve pipe forming piece is Cr-Mo low alloy steel.

[0015] Further, in step S2, the cooling speed of the pipe body of the primary heating sleeve pipe is 18-22 ℃ / s, and the cooling speed of the thickened end of the primary heating sleeve pipe is 12-14 ℃ / s.

[0016] Further, in step S4, the cooling speed of the pipe body of the secondary heating sleeve pipe is 18-22 ℃ / s, and the cooling speed of the thickened end of the secondary heating sleeve pipe is 12-14 ℃ / s.

[0017] Further, the element content of the steel pipe thickened sleeve pipe forming piece includes: the C content is 0.2wt%-0.3wt%, the Mn content is 0.4wt%-1.45wt%, the Cr content is 0.4wt%-1.2wt%, the Mo content is 0.4wt%-1.0wt%, and the balance is Fe.

[0018] Further, in step S1, the time of the primary quenching heating is (3.5-5.5)xt min, t is the wall thickness of the steel pipe thickened sleeve pipe forming piece, and the unit is mm.

[0019] Further, in step S3, the time of the second quenching heating is (5.5-7.5)xt min, t is the wall thickness of the steel pipe thickened sleeve forming piece, and the unit is mm.

[0020] Further, in step S1, the conditions of the first quenching heating include: the temperature is 880-890℃, and the holding time is (4-5)xt min, t is the wall thickness of the steel pipe thickened sleeve forming piece, and the unit is mm.

[0021] Further, in step S3, the conditions of the second quenching heating include: the temperature is 930-940℃, and the holding time is (6-7)xt min, t is the wall thickness of the steel pipe thickened sleeve forming piece, and the unit is mm.

[0022] Further, the flow rates of the first outer spray I, the first outer spray II, the second outer spray I and the second outer spray II are 3000-3200m 3 / h respectively; the flow rates of the first inner spray I, the first inner spray II, the second inner spray I and the second inner spray II are 1300-1500m 3 / h respectively; and the flow rates of the first outer surface water supplement and the second outer surface water supplement are both 500-600m 3 / h.

[0023] Further, in step S5, the conditions of the tempering treatment include: the temperature is 650-700℃, and the holding time is (11-14)xt min, t is the wall thickness of the steel pipe thickened sleeve forming piece, and the unit is mm.

[0024] Further, in step S5, the conditions of the tempering treatment include: the temperature is 670-690℃, and the holding time is (13-14)xt min, t is the wall thickness of the steel pipe thickened sleeve forming piece, and the unit is mm.

[0025] Further, in step S1, the temperature of the first heating sleeve when being subjected to the first water quenching is 800-840℃.

[0026] Further, in step S4, the temperature of the second heating sleeve when being subjected to the second water quenching is 840-880℃.

[0027] Further, the first quenching heating and the second quenching heating are both performed in a continuous step furnace.

[0028] Further, the grade of the steel pipe thickened sleeve forming piece is 27CrMo7S, 22CrMo8V or 25CrMnMo.

[0029] According to a second aspect of this application, a thickened steel pipe sleeve is provided, which is obtained by the heat treatment method of the aforementioned thickened steel pipe sleeve; wherein, the tensile strength deviation between the pipe body and the thickened end of the thickened steel pipe sleeve is ≤30MPa; and the yield strength deviation between the pipe body and the thickened end of the thickened steel pipe sleeve is ≤30MPa.

[0030] According to a third aspect of this application, a steel pipe thickened casing obtained by the heat treatment method described above and its application in the field of oil or natural gas extraction are provided.

[0031] Compared with the prior art, this application has the following beneficial effects:

[0032] The heat treatment method for thickened steel pipes provided in this application employs a single quenching heating process to ensure fine austenite grain control, preserving fine martensite morphology and undissolved carbides after the first water quenching, thus preparing for further refinement of the microstructure during the second quenching. A second quenching heating process ensures sufficient solid solution of alloying elements and thorough heating of the thickened end core, laying a solid microstructure foundation for achieving uniform and consistent performance. The innovative use of water replenishment at the thickened end during both the first and second water quenching processes further improves the microstructure of the thickened end, ensuring uniform performance between the thickened end and the overall pipe body after subsequent overall tempering. The innovative application of two quenching processes, the control of quenching temperature and time, the application of water replenishment at the thickened end, and the synergistic effect of tempering not only significantly improve the mechanical properties of the steel pipe but also enhance the performance uniformity between the thickened end and the pipe body. Furthermore, this method can be better applied to other petroleum processing raw materials with high strength and toughness requirements and significant differences in wall thickness between the pipe body and the thickened end. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 Metallographic image of the inner surface of the thickened end of the thickened sleeve prepared in Example 1 of this application;

[0035] Figure 2 Metallographic image of the wall thickness center of the thickened end of the thickened sleeve prepared in Example 1 of this application;

[0036] Figure 3 Metallographic image of the outer surface of the thickened end of the thickened sleeve prepared in Example 1 of this application;

[0037] Figure 4 This is a metallographic image of the wall thickness center of the thickened end of the thickened sleeve prepared in Example 2 of this application;

[0038] Figure 5 Metallographic diagram of the wall thickness center of the thickened end of the thickened sleeve prepared in Comparative Example 1 of this application;

[0039] Figure 6 Metallographic structure of the thickened end of the thickened sleeve prepared in Comparative Example 3 of this application;

[0040] Figure 7 This is a schematic diagram of the thickened end water supply device used in the embodiments of this application.

[0041] Figure label:

[0042] 1. Thickened sleeve; 11. Pipe body; 12. Thickened end;

[0043] 2. Thickened end water supply equipment; 21. Water supply pipe; 22. Water supply pipe; 23. Nozzle;

[0044] 3. Internal water spray pipe. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0046] As mentioned in the background section, the wall thickness of the thickened end of the steel pipe is usually 1.4 to 1.7 times that of the pipe body. In the single quenching and single tempering process, the cooling rate of the thickened end with a larger wall thickness is much lower than that of the pipe body during the quenching process, making it difficult to fully quench through. As a result, non-martensitic structures such as bainite are easily formed in the microstructure. Consequently, the mechanical properties (such as yield strength and tensile strength) of the thickened end are often lower than those of the pipe body. This inhomogeneity of properties seriously affects the overall safety and reliability of the casing.

[0047] According to one aspect of this application, a heat treatment method for thickened steel pipe sleeves is provided, the heat treatment method comprising the following steps:

[0048] Step S1: The steel pipe thickened sleeve forming part is subjected to a first quenching heating to obtain a first-heated sleeve; wherein, the conditions for the first quenching heating include: temperature of 880~900℃;

[0049] Step S2: Perform a water quench on the primary heating sleeve to obtain a primary water quenched sleeve; wherein, the tube body of the primary heating sleeve is cooled by the first external spray I and the first internal spray I, and the thickened end of the primary heating sleeve is cooled by the first external spray II, the first internal spray II and the first external surface water replenishment.

[0050] Step S3: Perform a second quenching heating on the first water-quenched sleeve to obtain a second-heated sleeve; wherein, the conditions for the second quenching heating include: a temperature of 920~940℃;

[0051] Step S4: Perform secondary water quenching on the secondary heating sleeve to obtain a secondary water quenched sleeve; wherein, the tube body of the secondary heating sleeve is cooled by the second external spray I and the second internal spray I, and the thickened end of the secondary heating sleeve is cooled by the second external spray II, the second internal spray II and the second external surface water replenishment.

[0052] Among them, the spray flow rates of the first external spray I, the first external spray II, the second external spray I, and the second external spray II are 2800~3200m³ / h, respectively. 3 / h; the spray flow rates of the first internal spray I, the first internal spray II, the second internal spray I, and the second internal spray II are 1000~1500m³ / h respectively. 3 / h; the spray flow rate for both the first and second surface water replenishment is 400~600m³ / h. 3 / h;

[0053] Step S5: Temper the secondary heating sleeve to obtain the final thickened steel pipe sleeve.

[0054] The primary quenching temperature in this application is any value from 880℃, 885℃, 890℃, 895℃, and 900℃, or a range between any two; the secondary quenching temperature is any value from 920℃, 925℃, 930℃, 935℃, and 940℃, or a range between any two; the holding time for both quenching heatings is controlled according to the wall thickness of the heating sleeve. By controlling the primary and secondary quenching heating temperatures within the above ranges, the internal microstructure of the formed steel pipe material can be made more uniform, thereby improving the performance consistency between the thickened end and the pipe body.

[0055] The spray flow rate of the first external shower I in this application is 2800, 2900, 3000, 3100, 3200 m³ / h. 3 The spray flow rate of the first external spray II, the second external spray I, and the second external spray II is the same as that of the first external spray I. The spray flow rate of the first internal spray I is 1000, 1100, 1200, 1300, 1400, or 1500 m³ / h. 3Any value in / h or a range between any two; the available range of spray flow rates for the first internal spray II, the second internal spray I, and the second internal spray II is the same as the available range of spray flow rate for the first internal spray I. Under the synergistic effect of the above two quenching heating processes, by adopting the above-mentioned composite cooling method of external spraying, internal spraying, and external surface water replenishment, and by precisely controlling the above-mentioned spray water flow rate, the cooling rate of the thickened end can be improved, making it as close as possible to the cooling effect of the tube body. This enables reasonable control of the microstructure of the thickened end and the tube body, thereby achieving consistent performance between the thickened end and the tube body.

[0056] In this application, the heating temperature and time of the thickened sleeve in the first quenching heating are relatively low. After ensuring that the thickened end reaches the transformation temperature, it is briefly held at that temperature before being taken out of the furnace, which allows the thickened sleeve to obtain fine original austenite grains. The first water quenching is to quench the sleeve heated in the first heating, which can quickly reduce the material temperature to the martensite transformation temperature, obtaining fine acicular martensite, some bainite, and some undissolved carbides. In the second quenching heating, the heating temperature of the thickened sleeve is higher and the heating time is longer, which can ensure that the thickened end is fully heated and the alloying elements are fully dissolved. The second water quenching is to cool the fully heated second heating sleeve by external rinsing and internal spraying, and to apply water to the surface of the thickened end, which can increase the cooling rate of the thickened end, so that the thickened end obtains all martensite and avoids the formation of bainite, which is beneficial to improving the performance consistency between the thickened end and the tube body.

[0057] To fully utilize the effects of the above-mentioned two quenching heating and two water quenching processes, a suitable thickening sleeve material is selected. In some specific embodiments, the material of the thickening sleeve forming part is Cr-Mo low alloy steel. This type of thickening sleeve has good mechanical properties. Due to its inherent characteristics, this type of thickening sleeve is more suitable for the heat treatment method of this application, and can maintain good consistency between the thickened end of the thickening sleeve and the tube body. Specifically, the core element content of the thickened sleeve includes: C content of 0.2wt%~0.3wt%, Mn content of 0.4wt%~1.45wt%, Cr content of 0.4wt%~1.2wt%, Mo content of 0.4wt%~1.0wt%, with the balance being Fe; for example: C content of 0.2wt%~0.3wt%, Si content of 0.2~0.3%, Mn content of 0.4wt%~1.45wt%, P content of 0.006~0.008%, S content of 0.001~0.003%, Cr content of 0.4wt%~1.2wt%, Mo content of 0.4wt%~1.0wt%, V content of 0.04~0.06%, with the balance being Fe. Other examples include grades such as 27CrMo7S, 22CrMo8V, or 25CrMnMo.

[0058] In some specific embodiments, the preparation process of the thickened steel pipe sleeve includes: sequentially subjecting the raw material to electric furnace smelting, ladle refining, vacuum degassing, arc continuous casting, and hot rolling to obtain a flat-end sleeve; upsetting the flat-end sleeve to obtain the thickened steel pipe sleeve; for example, the outer diameter of the thickened end of the thickened steel pipe sleeve is 200mm~220mm, the inner diameter is 140mm~150mm, and the length is 250mm~300mm; for example, the outer diameter is 216mm~220mm, the inner diameter is 143mm~147mm, and the length is 280mm~300mm; or, the outer diameter is 206mm~210mm, the inner diameter is 146mm~150mm, and the length of the thickened end is 250mm~270mm. The above-mentioned thickened sleeve sleeve can also be selected from existing technologies.

[0059] To further improve the effect of the primary quenching heating, uniform heating can be performed according to the wall thickness of the thickened sleeve. In some specific embodiments, the primary quenching heating is carried out in a continuous walking beam furnace. The primary quenching heating time is (3.5~5.5)×t min, where t is the wall thickness of the thickened sleeve in mm. For example, the temperature is 880~890℃, and the holding time is (4~5)×t min. Controlling the primary quenching heating time within the above range ensures that the thickened sleeve is fully heated without causing overheating and coarse grains due to excessively long heating time. This is beneficial for providing a fine initial structure for the secondary quenching heating, thereby improving production efficiency.

[0060] To improve the primary water quenching effect and ensure the generation of a large number of fine-grained martensite, the water quenching flow rate is precisely controlled. In some specific embodiments, the primary heating sleeve is fed to the water quenching area via a roller conveyor for primary water quenching, with a feeding speed of ≥0.61m / s. The equipment capable of achieving water replenishment at the thickened end of the thickened sleeve is not limited to any type, as long as it can achieve the required water replenishment volume. As shown, the inner body 11 and thickened end 12 of the thickened sleeve 1 are cooled by spraying with an internal water spray pipe 3; the outer side of the thickened end 12 is cooled by spraying with a thickened end water replenishment device 2, which includes: a horizontally arranged water supply pipe 21 and a water replenishment pipe 22 connected to the water supply pipe 21 (the horizontal section of the water replenishment pipe is 300mm long and has an outer diameter of 100mm). The water replenishment pipe 22 is placed at an angle of 45° to the thickened end 12, and nozzles 23 (e.g., 20 nozzles with an orifice diameter of 5mm) are distributed at the outlet of the water replenishment pipe 22 to replenish water to the thickened end 12. This equipment can achieve good water replenishment and cooling effect on the thickened end 12 of the thickened sleeve 1. The temperature of the sleeve during the first water quenching is 800~840℃. The flow rates of the first external quencher I and the first external quencher II are 3000~3200 m³ / h, respectively. 3 / h; the flow rates of the first internal spray I and the first internal spray II are 1300~1500m³ / h respectively. 3 / h; the flow rate of the first surface water replenishment is 500~600m³ / h. 3 The cooling rate of the primary heating sleeve body is 15~25℃ / s, and the cooling rate of the thickened end of the primary heating sleeve is 9~14℃ / s. The temperature of the quenching cooling water is ≤30℃. Preferably, the cooling rate of the primary heating sleeve body is 18~22℃ / s, and the cooling rate of the thickened end of the primary heating sleeve is 12~14℃ / s. The flow rates of the external and internal spray water will affect the cooling rate. A high flow rate can enhance the cooling effect, while a low flow rate will slow down the cooling rate. Water replenishment at the thickened end can further enhance the cooling rate of the thickened end. Controlling the flow rates of the external and internal spray water, the water replenishment flow rate at the thickened end, and the cooling rate within the above ranges is beneficial for producing finer martensite and bainite structures, and helps to improve the hardenability of secondary quenching and optimize its microstructure.

[0061] Similarly, to ensure sufficient solid solution of the alloying elements in the thickened sleeve, the sleeve can be uniformly heated according to its wall thickness. In some specific embodiments, the secondary quenching heating is carried out in a continuous walking beam furnace. The secondary quenching heating time is (5.5~7.5)×t min, where t is the wall thickness of the thickened sleeve in mm. For example, the temperature is 930~940℃, and the holding time is (6~7)×t min. Controlling the secondary quenching heating time within the above range allows for sufficient solid solution of the alloying elements in the thickened end and the tube body, which is beneficial for improving the hardenability of the secondary quenching process. This, in turn, improves the complete transformation of the sleeve into martensite during subsequent water quenching, thus improving the overall mechanical properties of the thickened sleeve, such as tensile strength and yield strength.

[0062] To ensure the complete transformation of the thickened sleeve into martensite, the secondary water quenching flow rate is precisely controlled. In some specific embodiments, the temperature of the secondary heated sleeve during secondary water quenching is 840~880℃. The spray flow rates of the second external quencher I and the second external quencher II are 3000~3200 m³ / h, respectively. 3 / h; the spray flow rates of the second internal spray I and the second internal spray II are 1300~1500m³ / h respectively. 3 / h; the spray flow rate for the second surface water replenishment is 500~600m³ / h. 3 The cooling rate of the secondary heating sleeve body is 15~25℃ / s, the cooling rate of the thickened end of the secondary heating sleeve is 9~14℃ / s, and the temperature of the quenching cooling water is ≤30℃; preferably, the cooling rate of the secondary heating sleeve body is 18~22℃ / s, and the cooling rate of the thickened end of the secondary heating sleeve is 12~14℃ / s. Controlling the external and internal spray flow rates of the secondary water quenching, the water supply flow rate at the thickened end, and the cooling rate within the above range is beneficial to improving hardenability, allowing the thickened end to more fully transform into martensite, reducing the difference in quenching hardness between the thickened end and the sleeve body, thereby preparing for excellent overall tube performance after overall tempering.

[0063] After the above two heating cycles and two water quenching cycles, in order to further improve the overall mechanical properties of the thickened sleeve, such as tensile strength, yield strength, and elongation, the sleeve is subjected to appropriate tempering treatment. In some specific embodiments, in step S5, the tempering conditions include: a temperature of 650~700℃ and a holding time of (11~14)×t min, where t is the wall thickness of the thickened sleeve forming part in mm. For example, a temperature of 670~690℃ and a holding time of (13~14)×t min; for example, a wall thickness of 28~40 mm for the thickened sleeve forming part. Controlling the overall tempering heating time of the thickened sleeve within the above-mentioned range ensures that the thickened end and the tube body are fully transformed into tempered sorbite structure, while preventing the tube body from becoming over-softened, which would lead to a decrease in performance. The control of the overall tempering heating time ensures that the thickened end is fully heated, while also preventing the tube body from softening due to excessive coarsening of carbides, which would result in lower tube body performance. The synergistic effect of process conditions such as the control of the two quenching heating temperatures and heating times, the application of water replenishment at the thickened end, and the control of tempering holding time significantly improves the mechanical properties of the steel pipe and the performance uniformity between the thickened end and the tube body.

[0064] According to a second aspect of this application, a thickened steel pipe sleeve is provided, which is a thickened steel pipe sleeve obtained by the heat treatment method described above; wherein, the tensile strength of the steel pipe sleeve body is ≥850MPa, the tensile strength of the thickened end of the steel pipe sleeve is ≥860MPa; the tensile strength deviation is ≤30MPa; the yield strength of the steel pipe sleeve body is ≥780MPa, the yield strength of the thickened end of the steel pipe sleeve is ≥800MPa; the yield strength deviation is ≤30MPa.

[0065] It should be noted that, due to the specific nature of the materials and limitations of existing testing and characterization methods, a comprehensive characterization of the thickened sleeve obtained by the above preparation method is not possible. However, experiments have confirmed that the performance deviation between the thickened end and the main body of the thickened steel pipe is relatively small.

[0066] According to a third aspect of this application, a steel pipe thickened casing obtained by the heat treatment method described above, or the application of the steel pipe thickened casing described above in the field of oil or natural gas extraction, is provided.

[0067] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0068] The raw materials used in the embodiments of this application are all existing technologies and are commercially available.

[0069] Example 1

[0070] The thickened tube is heat-treated using a continuous walking beam furnace, and the specific heat treatment steps for the thickened tube include:

[0071] Hot rolling forming: The raw material with the material grade 27CrMo7S is smelted in an electric furnace, refined in a ladle, degassed in a vacuum and continuously cast in an arc to obtain a continuously cast round billet with a billet diameter of 250mm. After hot rolling, a flat end sleeve with a specification of 203.2mm×25.4mm is obtained (outer diameter of sleeve 203.2mm, wall thickness of sleeve 25.4mm, inner diameter of sleeve 152.4mm). The ends of both ends of the sleeve are thickened to obtain a thickened end 12 with an outer diameter of 218mm, an inner diameter of 145mm and a length of 290mm.

[0072] First quenching heating: The thickened sleeve is placed in a continuous walking furnace for heating at a temperature of 885℃ for 120 minutes, so that the thickened sleeve is heated evenly as a whole.

[0073] First water quenching: After the heated thickened sleeve is removed from the quenching furnace, high-pressure water descaling is initiated (pressure set at 19MPa). A high-speed roller conveyor (speed set at 0.61m / s) rapidly transports the high-temperature steel pipe to the water quenching area. The temperature of the heated thickened sleeve during the first stage of water quenching is controlled at 830℃±10℃. Cooling is achieved using an external spray + internal spray + thickened end water replenishment method. The external spray flow rate is set to 3000m³ / h. 3 / h, internal spray flow rate setting: 1300m 3 / h, thickened end water supply spray flow rate 500m³ / h 3 / h, the cooling rate of the thickened end is controlled at 13℃ / s, and the cooling rate of the pipe body is controlled at 20℃ / s, so that the steel pipe is rapidly cooled to room temperature; among which, such as Figure 7 As shown, the interior of the pipe body 11 and the thickened end 12 is cooled by spraying with an internal water spray pipe 3; the thickened end 12 is cooled by spraying with a thickened end water supply device 2, which includes: a horizontally arranged water supply pipe 21 and a water supply pipe 22 (the horizontal section of the water supply pipe is 300mm long and the outer diameter is 100mm). The water supply pipe 22 is placed at an angle of 45° to the thickened end 12 of the thickened sleeve 1. A row of nozzles 23 (20 nozzles with an orifice diameter of 5mm) are distributed on the water supply pipe 22 to supply water to the thickened end 12.

[0074] Secondary quenching heating: The thickened sleeve after the first quenching is placed in a continuous walking furnace for heating at a temperature of 935℃ for 170 minutes, so that the thickened sleeve is heated evenly and fully dissolved.

[0075] Secondary water quenching: After the heated thickened sleeve is removed from the quenching furnace, high-pressure water descaling is initiated (pressure set at 19MPa). A high-speed roller conveyor (speed set at 0.61m / s) rapidly transports the high-temperature steel pipe to the water quenching area. The temperature of the heated thickened sleeve during the second stage of water quenching is controlled at 860℃±10℃. An external spray + internal spray + thickened end water replenishment method is used, with the external spray flow rate set at 3000m³ / h. 3 / h, internal spray flow rate setting: 1300m 3 / h, pipe end water supply flow rate 500m³ 3 / h, thickened end water supply equipment such as Figure 7 As shown; the cooling rate of the thickened end is controlled at 13℃ / s, and the cooling rate of the pipe body is controlled at 20℃ / s, so that the steel pipe can be quickly cooled to room temperature;

[0076] Overall tempering: The thickened sleeve after secondary water quenching is placed in a continuous walking beam furnace for overall tempering. The tempering temperature is set to 680±5℃, and the furnace time is 325 minutes, resulting in the final thickened sleeve product. The metallographic structure of the inner surface of the thickened end of the thickened sleeve is as follows: Figure 1 As shown, the metallographic structure of the central part of the thickened end is as follows: Figure 2 As shown, the metallographic structure of the outer surface of the thickened end is as follows: Figure 3 As shown.

[0077] Example 2

[0078] The thickened tube is heat-treated using a continuous walking beam furnace, and the specific heat treatment steps for the thickened tube include:

[0079] Hot rolling forming: The raw material with the material grade 27CrMo7S is smelted in an electric furnace, refined in an external furnace, degassed in a vacuum and continuously cast in an arc to obtain a continuously cast round billet with a billet diameter of 250mm. After hot rolling, a flat-end sleeve with a specification of 193.68mm×19.05mm is obtained (sleeve outer diameter of 193.68mm, sleeve wall thickness of 19.05mm, sleeve inner diameter of 155.58mm). The ends of both ends of the sleeve are thickened to obtain a thickened sleeve 1 with an outer diameter of 208mm, an inner diameter of 148mm and a length of 260mm.

[0080] One-time quenching heating: The thickened sleeve workpiece is placed in a continuous walking furnace for heating at a temperature of 885℃ for 95 minutes, so that the thickened sleeve is heated evenly as a whole.

[0081] First water quenching: After the heated thickened casing is removed from the quenching furnace, high-pressure water descaling is initiated (pressure set at 19MPa). A high-speed roller conveyor (speed set at 0.61m / s) rapidly transports the high-temperature steel pipe to the water quenching area. The temperature of the heated thickened casing during the first stage of water quenching is controlled at 830℃±10℃. An external spray + internal spray + thickened end water replenishment method is used, with the external spray flow rate set at 3000m³ / h. 3 / h, internal spray flow rate setting: 1400m 3 / h, thickened end water supply spray flow rate 500m³ / h 3 / h; the cooling rate of the thickened end is controlled at 13℃ / s, and the cooling rate of the pipe body is controlled at 20℃ / s, so that the steel pipe can be rapidly cooled to room temperature; among which, such as Figure 7 As shown, the interior of the pipe body 11 and the thickened end 12 is cooled by spraying with an internal water spray pipe 3; the thickened end 12 is cooled by spraying with a thickened end water supply device 2, which includes: a horizontally arranged water supply pipe 21 and a water supply pipe 22 (the horizontal section of the water supply pipe is 300mm long and the outer diameter is 100mm). The water supply pipe 22 is placed at an angle of 45° to the thickened end 12 of the thickened sleeve 1. A row of nozzles 23 (20 nozzles with an orifice diameter of 5mm) are distributed on the water supply pipe 22 to supply water to the thickened end 12.

[0082] Secondary quenching heating: The thickened sleeve after the first quenching is placed in a continuous walking furnace for heating at a temperature of 935℃ for 130 minutes, so that the thickened sleeve is heated evenly and fully dissolved.

[0083] Secondary water quenching: After the heated thickened sleeve is removed from the quenching furnace, high-pressure water descaling is initiated (pressure set at 19MPa). A high-speed roller conveyor (speed set at 0.61m / s) rapidly transports the high-temperature steel pipe to the water quenching area. The temperature of the heated thickened sleeve during the second stage of water quenching is controlled at 860℃±10℃. An external spray + internal spray + thickened end water replenishment method is used, with the external spray flow rate set at 3000m³ / h. 3 / h, internal spray flow rate setting: 1400m 3 / h, thickened end water supply flow rate 500m³ / h 3 / h, the cooling rate of the thickened end is controlled at 13℃ / s, and the cooling rate of the pipe body is controlled at 20℃ / s, so that the steel pipe can be cooled to room temperature quickly;

[0084] Overall tempering: The thickened sleeve after secondary quenching is placed in a continuous walking beam furnace for overall tempering. The tempering temperature is set to 680±5℃, and the furnace time is 250 min, resulting in the final thickened sleeve product. The metallographic structure at the center of the thickened end wall of the thickened sleeve is as follows: Figure 4 As shown.

[0085] Example 3

[0086] The difference between Example 3 and Example 1 is that the heating temperature for the first quenching heating is 900°C and the furnace time is 120 minutes.

[0087] Example 4

[0088] The difference between Example 4 and Example 1 is that the heating temperature for the first quenching heating is 880°C and the furnace time is 139 minutes.

[0089] Example 5

[0090] The difference between Example 5 and Example 1 is that the heating temperature for the secondary quenching heating is 940°C and the furnace time is 140 min.

[0091] Example 6

[0092] The difference between Example 6 and Example 1 is that the heating temperature for the secondary quenching heating is 920°C and the furnace time is 190 min.

[0093] Example 7

[0094] The difference between Example 7 and Example 1 is that the external spray flow rate is 3200 m³ / h during a single water quenching process. 3 / h, internal spray flow rate is 1500m³ / h 3 The tube cooling rate is 24℃ / s, and the thickened end water supply flow rate is 600m³ / h. 3 / h, the cooling rate of the thickened end is 14℃ / s.

[0095] Example 8

[0096] The difference between Example 8 and Example 1 is that, during the secondary water quenching process, the external spray flow rate is 2800 m³ / h. 3 / h, internal spray flow rate is 1000m³ / h 3 The tube cooling rate is 16℃ / s, and the thickened end water supply flow rate is 400m³ / h. 3 / h, the cooling rate of the thickened end is 10℃ / s.

[0097] Example 9

[0098] The difference between Example 9 and Example 1 is that the tempering temperature is 680°C and the holding time is 355 min.

[0099] Example 10

[0100] The difference between Example 10 and Example 1 is that the tempering temperature is 680°C and the holding time is 280 min.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 2 is that the thickened sleeve forming workpiece was not subjected to one quenching heating and one water quenching during heat treatment, but only two quenching heating and two water quenching.

[0103] The specific steps include:

[0104] The raw material with the material grade 27CrMo7S was smelted in an electric furnace, refined outside the ladle, degassed in a vacuum, and continuously cast in an arc to obtain a continuously cast round billet with a billet diameter of 250mm. After hot rolling, a flat-end sleeve with a specification of 193.68mm x 19.05mm was obtained (sleeve outer diameter of 193.68mm, sleeve wall thickness of 19.05mm, sleeve inner diameter of 155.58mm). The ends of the flat-end sleeve were thickened to obtain a thickened sleeve 1 with an outer diameter of 208mm, an inner diameter of 148mm, and a length of 260mm.

[0105] Quenching and heating: The thickened sleeve is placed in a continuous walking furnace for heating at a temperature of 935±5℃ for 130 minutes, so that the thickened sleeve is heated evenly and fully dissolved.

[0106] Water quenching: After the heated thickened casing is removed from the quenching furnace, high-pressure water descaling is initiated (pressure set at 19MPa). A high-speed roller conveyor (speed set at 0.61m / s) rapidly transports the high-temperature steel pipe to the water quenching area. The temperature of the heated thickened casing during water quenching is controlled at 860℃±10℃. An external spray + internal spray + pipe end water replenishment method is used, with the external spray flow rate set at 3000m³ / h. 3 / h, internal spray flow rate setting: 1400m 3 / h, thickened end water supply flow rate 500m³ / h 3 / h, the cooling rate of the thickened end is controlled at 13℃ / s, and the cooling rate of the pipe body is controlled at 20℃ / s, so that the steel pipe is rapidly cooled to room temperature; the water supply to the pipe end is carried out using... Figure 7 The thickened end water supply device 2 is shown.

[0107] Overall tempering: The quenched thickened sleeve is placed in a continuous walking beam furnace for overall tempering. The tempering temperature is set to 680±5℃, and the furnace time is 250 minutes, resulting in the final thickened sleeve product. The metallographic structure at the center of the thickened end wall of the thickened sleeve is as follows: Figure 5 As shown.

[0108] Comparative Example 2

[0109] The difference between Comparative Example 2 and Example 1 is that the thickened sleeve is subjected to only one quenching heating and one water quenching during heat treatment, without a second quenching heating and a second water quenching; the thickened sleeve after the first water quenching is tempered to obtain the final thickened sleeve product.

[0110] Comparative Example 3

[0111] The difference between Comparative Example 3 and Example 1 is that, in both the primary and secondary quenching processes of the thickened sleeve forming workpiece, no water was added to the thickened end; the metallographic structure at the center of the thickened end wall of the thickened sleeve is as follows: Figure 6 As shown.

[0112] Performance testing:

[0113] The component distribution of the thickened sleeve products of the above embodiments and comparative examples is shown in Table 1 (component content is expressed as a weight percentage).

[0114] The mechanical properties of the heat-treated thickened sleeves in each embodiment and comparative example were tested using the following methods, and the results are shown in Tables 2 and 3.

[0115] (1) When testing the thickened sleeves prepared in each embodiment and comparative example, the sampling point of the thickened end is 1 / 2 of the wall thickness of the thickened end.

[0116] (2) Rp0.7: The 0.7% offset yield strength of the thickened sleeve. The test method is based on the national standard GB / T 228.

[0117] (3) Rm: The tensile strength of the thickened sleeve. The test method is based on the national standard GB / T 228.

[0118] (4) The test method for elongation is in accordance with the national standard GB / T 228.

[0119] (5) Quenching hardness: Three points were taken at distances of 2.54 mm to 3.81 mm from the inner and outer surfaces of the sample, respectively. Three points were taken at 1 / 2 wall thickness. The hardness of the sample in the four quadrants was tested. The test method was in accordance with the national standard GB / T230.

[0120]

[0121]

[0122]

[0123] Table 2 shows that the thickened sleeves of Examples 1 to 10 of this application are subjected to two quenching treatments plus water replenishment treatment at the thickened end. By controlling the temperature and heating time during the quenching heating process, the temperature and heating time during the tempering heating process, and the flow rate during the two quenching processes, the thickened sleeves are obtained after heat treatment. The performance uniformity and consistency between the thickened end and the pipe body are good. In particular, by controlling the parameters during the heat treatment process within the preferred range, the overall performance of the steel pipe is better.

[0124] Comparative Examples 1 and 2 used a method of one quenching and one tempering. The thickened end of the steel pipe obtained after heat treatment had a large difference in performance from the pipe body, and the performance of the thickened end could not meet the requirements of the standard.

[0125] Although Comparative Example 3 used two quenching processes, water replenishment was not used at the thickened end during the first and second quenching processes. As a result, the performance of the thickened end of the thickened steel pipe was significantly different from that of the pipe body, and the performance of the thickened end could not meet the requirements of the standard.

[0126] Table 3 shows that the hardness values ​​at each point in Example 1 were stable at around 48 HRC, with the maximum hardness deviation of the cross section being 2.5 HRC. This indicates that the microstructure of the entire cross section was almost entirely transformed into high-hardness martensite, which is a manifestation of the ideal quenching effect.

[0127] The hardness tested in Comparative Examples 2 and 3 exhibited typical characteristics of insufficient quenching: in particular, the hardness in the middle of the cross section was significantly reduced (approximately 40 HRC in Comparative Example 2 and approximately 41 HRC in Comparative Example 3). The hardness of these structures was much lower than that of martensite, resulting in a decrease and unevenness in overall hardness.

[0128] For example, Figure 2 This is a metallographic image of the center of the wall thickness at the thickened end in Example 1, where martensite accounts for 100%. Figure 5 The image shows the metallographic structure at the center of the thickened end in Comparative Example 1, where martensite accounts for 60% and bainite accounts for 40%. Figure 6 The image shows the metallographic structure of the thickened end of Comparative Example 3, where martensite accounts for 75% and bainite accounts for 25%.

[0129] It is evident that the thickened sleeve obtained by the heat treatment process in Example 1 has been completely transformed into martensite, which has excellent mechanical properties; while Comparative Examples 1 to 3 either used a single quenching or did not replenish water to the thickened end, resulting in an uneven overall microstructure of the thickened sleeve, which was not completely transformed into martensite, and its mechanical properties were significantly worse.

[0130] The thickened sleeve and its heat treatment method provided in this application successfully solve the problem of performance uniformity control caused by the large difference in wall thickness between the thickened end and the tube body during the heat treatment process of high-performance thickened sleeves through the synergistic process design of "two quenchings + differentiated cooling at the thickened end". This method not only significantly improves the overall mechanical property consistency of the sleeve (the yield strength deviation between the thickened end and the tube body is ≤30MPa), but also achieves synergistic optimization of material strength and toughness through microstructure control (such as obtaining a full martensitic structure at the thickened end).

[0131] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0132] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A heat treatment method for thickened steel pipe sleeves, characterized in that, It includes the following steps: Step S1: The thickened steel pipe sleeve forming part is subjected to a first quenching heating to obtain a first-heated sleeve; wherein, the temperature of the first quenching heating is 880~900℃; the time of the first quenching heating is (3.5~5.5)×t min, where t is the wall thickness of the thickened steel pipe sleeve forming part in mm; the element content of the thickened steel pipe sleeve forming part includes: C content of 0.2wt%~0.3wt%, Mn content of 0.4wt%~1.45wt%, Cr content of 0.4wt%~1.2wt%, Mo content of 0.4wt%~1.0wt%, and the balance is Fe; Step S2: The primary heating sleeve is subjected to a primary water quench to obtain a primary water quenched sleeve; wherein, the tube body of the primary heating sleeve is cooled by a first external spray I and a first internal spray I; the thickened end of the primary heating sleeve is cooled by a first external spray II, a first internal spray II and a first external surface water replenishment. Step S3: Perform secondary quenching heating on the first-water quenched sleeve to obtain a secondary heated sleeve; wherein, the temperature of the secondary quenching heating is 920~940℃; the time of the secondary quenching heating is (5.5~7.5)×t min, where t is the wall thickness of the steel pipe thickened sleeve forming part, in mm; Step S4: Perform secondary water quenching on the secondary heating sleeve to obtain a secondary water-quenched sleeve; wherein, the tube body of the secondary heating sleeve is cooled by a second external spray I and a second internal spray I; the thickened end of the secondary heating sleeve is cooled by a second external spray II, a second internal spray II, and a second external surface water replenishment. The spray flow rates of the first external spray I, the first external spray II, the second external spray I, and the second external spray II are 2800~3200 m³ / h, respectively. 3 / h; the spray flow rates of the first internal spray I, the first internal spray II, the second internal spray I, and the second internal spray II are 1000~1500m³ / h, respectively. 3 / h; the flow rates of both the first and second surface water replenishment are 400~600m³ / h. 3 / h; Step S5: Temper the secondary heating sleeve. The tempering conditions include: temperature of 650~700℃ and holding time of (11~14)×t min, where t is the wall thickness of the steel pipe thickened sleeve forming part in mm, to obtain the final steel pipe thickened sleeve.

2. The heat treatment method for thickened steel pipe sleeves according to claim 1, characterized in that, In step S2, the cooling rate of the tube body of the primary heating sleeve is 15~25℃ / s, and the cooling rate of the thickened end of the primary heating sleeve is 9~14℃ / s. And / or, in step S4, the cooling rate of the tube body of the secondary heating sleeve is 15~25℃ / s, and the cooling rate of the thickened end of the secondary heating sleeve is 9~14℃ / s; And / or, the material of the thickened sleeve forming part of the steel pipe is Cr-Mo low alloy steel.

3. The heat treatment method for thickened steel pipe sleeves according to claim 1, characterized in that, In step S2, the cooling rate of the tube body of the primary heating sleeve is 18~22℃ / s, and the cooling rate of the thickened end of the primary heating sleeve is 12~14℃ / s. And / or, in step S4, the cooling rate of the tube body of the secondary heating sleeve is 18~22℃ / s, and the cooling rate of the thickened end of the secondary heating sleeve is 12~14℃ / s.

4. The heat treatment method for thickened steel pipe sleeves according to any one of claims 1 to 3, characterized in that, In step S1, the conditions for the first quenching heating include: a temperature of 880~890℃ and a holding time of (4~5)×t min, where t is the wall thickness of the steel pipe thickened sleeve forming part, in mm; And / or, in step S3, the conditions for the secondary quenching heating include: a temperature of 930~940℃ and a holding time of (6~7)×t min, where t is the wall thickness of the steel pipe thickened sleeve forming part, in mm.

5. The heat treatment method for thickened steel pipe sleeves according to any one of claims 1 to 3, characterized in that, The flow rates of the first external shower I, the first external shower II, the second external shower I, and the second external shower II are 3000~3200 m³ / h, respectively. 3 / h; the flow rates of the first internal spray I, the first internal spray II, the second internal spray I, and the second internal spray II are 1300~1500m³ / h respectively. 3 / h; the flow rates of both the first and second surface water replenishment are 500~600m³ / h. 3 / h.

6. The heat treatment method for thickened steel pipe sleeves according to any one of claims 1 to 3, characterized in that, In step S5, the tempering conditions include: a temperature of 670~690℃ and a holding time of (13~14)×t min, where t is the wall thickness of the steel pipe thickened sleeve forming part, in mm; And / or, in step S1, the temperature of the primary heating sleeve during the primary water quenching is 800~840℃; And / or, in step S4, the temperature of the secondary heating sleeve during the secondary water quenching is 840~880℃.

7. The heat treatment method for thickened steel pipe sleeves according to any one of claims 1 to 3, characterized in that, Both the primary quenching heating and the secondary quenching heating are carried out in a continuous walking beam furnace; And / or, the grade of the thickened steel pipe sleeve is 27CrMo7S, 22CrMo8V or 25CrMnMo.

8. A thickened steel pipe sleeve, characterized in that, The thickened steel pipe sleeve is obtained by the heat treatment method of the thickened steel pipe sleeve according to any one of claims 1 to 7; wherein, the tensile strength deviation between the pipe body and the thickened end of the thickened steel pipe sleeve is ≤30MPa; and the yield strength deviation between the pipe body and the thickened end of the thickened steel pipe sleeve is ≤30MPa.

9. The application of the thickened steel pipe casing obtained by the heat treatment method of any one of claims 1 to 7, or the thickened steel pipe casing of claim 8, in the field of oil or natural gas extraction.

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