A low expansion pressure and high resistance to external extrusion expansion sleeve after expansion

Abstract

This invention discloses a low-expansion-pressure and high-resistance-to-extrusion-stretch-out sleeve, with the following chemical composition by weight percentage: C: 0.04%~0.25%, Si: 0.1%~1.0%, Mn: 0.5%~1.8%, Nb: 0.02%~0.10%, P<150ppm, S<80ppm, with the balance being Fe and unavoidable impurities. The production method includes: steel smelting and continuous casting to obtain a suitable billet; hot rolling to produce a tube blank, ensuring suitable dimensions and a microstructure with good plasticity; pretreatment of the hot-rolled tube blank, including pickling, cleaning, neutralization, phosphating, and saponification; cold rolling to achieve the required size specifications and high dimensional accuracy; heat treatment, such as annealing or tempering, to optimize material properties; and sandblasting or grinding of the inner surface, along with rust prevention measures.

Description

Technical Field

[0001] This invention relates to the field of expansion sleeve technology, and more specifically, to an expansion sleeve with low expansion pressure and high resistance to external extrusion after expansion. Background Technology

[0002] Solid expansion casing in oil and gas development engineering is a type of metal round tube, which can be made of aluminum alloy, titanium alloy, etc., but steel tube is currently the most mature and widely used. Due to its good plasticity, its diameter can be increased downhole through mechanical or hydraulic means, while simultaneously improving its rigidity to achieve good bonding with downhole structures and resist internal and external pressures. Solid expansion casing is mainly used to seal lost circulation zones and high-pressure water layers, isolate fracture zones, repair damaged casing and seal perforated casing, replace conventional tailpipe hangers and tailpipe hanger packers, and serve as a replacement for conventional casing. Existing expansion casings still have shortcomings in the comprehensive design of strength, plasticity, and toughness, as well as in dimensional accuracy control, resulting in problems such as excessively high expansion pressure, unstable expansion pressure, and low resistance to internal and external pressures after expansion.

[0003] Therefore, it is necessary to design the chemical composition of the expansion sleeve and adopt a more reasonable process route to improve product performance and enhance product quality in order to meet the needs of engineering applications. Summary of the Invention

[0004] The present invention provides a low expansion pressure and high resistance to external extrusion expansion sleeve after expansion, in order to overcome at least one technical problem existing in the prior art.

[0005] This invention provides a low expansion pressure and high resistance to external extrusion expansion sleeve after expansion, comprising:

[0006] The chemical composition by weight percentage is C: 0.04%~0.25%, Si: 0.1%~1.0%, Mn: 0.5%~1.8%, Nb: 0.02%~0.10%, P<150ppm, S<80ppm, with the balance being Fe and unavoidable impurities;

[0007] The production method of this low expansion pressure and high resistance to external extrusion expansion sleeve after expansion specifically includes:

[0008] Step S1: Steel is smelted in a converter or electric furnace according to the composition, and billets are produced by continuous casting.

[0009] Step S2: Produce tube blanks using hot rolling method, with the billet heating temperature at 1150~1250℃. o C, hold at temperature for 1-4 hours, initial rolling temperature at 1100℃ o C and above, with a final rolling temperature of 850~950℃. oC. After rolling, the tube blank is naturally cooled in air; the diameter of the hot-rolled tube blank is 105%~120% of the diameter of the final product, and the wall thickness is 100%~120% of the diameter of the final product; the tube blank microstructure consists of ferrite + a small amount of pearlite.

[0010] Step S3: The hot-rolled billet is pickled, cleaned, neutralized, phosphated, and saponified. Then, the billet is continuously rolled using a cold rolling mill to achieve the final required dimensions. The dimensional tolerances are: wall thickness tolerance < ±3%, outer diameter tolerance < ±0.3%.

[0011] Step S4: The cold-rolled steel pipe is subjected to heat treatment. Annealing is selected as the heat treatment method, using a gas furnace, resistance furnace, or induction heating furnace. The annealing temperature is controlled at 400°C. o C ~750 o C, time 0.5h~4h, air cool to room temperature, the final microstructure is ferrite with a small amount of carbides; or a quenching and tempering heat treatment method is used, using a gas furnace, resistance furnace or induction heating furnace, heated to 800°C. o C ~950 o C, quenching to obtain lower bainite structure, then heating to 400 o C~750 o C, time 0.5h~4h, air cool to room temperature, the final microstructure is tempered bainite;

[0012] Step S5: Use a multi-roller straightener to straighten the heat-treated steel pipe. After straightening, the dimensional accuracy should reach wall thickness tolerance <±4%, outer diameter tolerance <±0.4%, and straightness <0.2mm / m.

[0013] Step S6: Sandblast or grind the inner wall of the heat-treated steel pipe to remove the oxide scale on the inner surface of the steel pipe. While keeping it dry, add pipe plugs to both ends of the steel pipe for protection. Spray paint on the outer wall of the steel pipe for protection to prevent corrosion during storage.

[0014] Preferably, it also includes Cr: 0.1%~1.5% and Ni: 0.1%~3.0%.

[0015] Preferably, it also includes: Cu: 0.1%~1.0%, Ti: 0.01~0.02%, and V: 0.01~0.2%.

[0016] Preferably, the Cu content does not exceed 40% of the Ni content.

[0017] This specification provides an embodiment that achieves at least the following beneficial effects: it is designed to solve problems encountered during the use of expansion sleeves, particularly to meet the requirements of low expansion pressure and high resistance to external extrusion after expansion. The technical solution of this application improves the overall performance of the expansion sleeve by optimizing material composition and manufacturing processes, such as improving dimensional accuracy and maintaining appropriate strength, thereby better meeting practical application needs. The products manufactured using this expansion tube production technology have a final microstructure of refined ferrite with a small amount of carbides, and a strength generally within the range of 300~500MPa. The control method is simple, and performance fluctuations are minimal. This ensures that the strength before expansion reaches over 300MPa while preventing excessive pressure during expansion. More importantly, the use of hot rolling + cold rolling + heat treatment significantly improves dimensional accuracy compared to existing products, with wall thickness tolerance <±4%, outer diameter tolerance <±0.4%, and straightness <0.2mm / m (standard hot-rolled tube wall thickness tolerance <±8%, outer diameter tolerance <±1%, straightness <0.5mm / m). Improving the dimensional accuracy of the steel pipe before expansion effectively improves the dimensional accuracy of the expanded steel pipe, which is crucial for enhancing the pipe's resistance to higher internal and external pressures. Therefore, the technical solution in this application uses low-alloy additives (low-cost materials) and achieves an excellent match between material performance and product quality with a limited increase in steel pipe production costs, thus meeting the technical requirements of low expansion pressure and high resistance to external extrusion after expansion of the expansion sleeve. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a production method for a low expansion pressure and high resistance to external extrusion expansion sleeve according to an embodiment of this application.

[0020] Figure 2 Based on Figure 1 A schematic diagram of the microstructure of the expansion tube produced by the annealing process using the method described in the article—ferrite + carbide;

[0021] Figure 3 Based on Figure 1 The diagram shows the microstructure of the expansion tube obtained by the method described in the article, namely tempered bainite. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of one or more embodiments of this specification clearer, the technical solutions of one or more embodiments of this specification will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of them. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of one or more embodiments of this specification.

[0023] The performance requirements for expansion sleeves are mainly as follows: 1. Maintain a certain strength (above 300MPa) and good plasticity before expansion; 2. The expansion pressure should not be too high during the expansion process (generally not higher than 30MPa, preferably within 25MPa); 3. After expansion, it can resist high internal and external pressures, generally requiring resistance to internal pressure of 60MPa and external pressure of 20MPa.

[0024] To achieve the above technical objectives, the present invention provides a low expansion pressure and high resistance to external extrusion expansion sleeve after expansion, wherein the chemical composition by weight percentage is C: 0.04%~0.25%, Si: 0.1%~1.0%, Mn: 0.5%~1.8%, Nb: 0.02%~0.10%, P<150ppm, S<80ppm, and the balance is Fe and unavoidable impurities;

[0025] The production method of this low expansion pressure and high resistance to external extrusion expansion sleeve after expansion specifically includes:

[0026] Step S1: Steel is smelted in a converter or electric furnace according to the above chemical composition, and billets are produced by continuous casting.

[0027] Step S2: Producing tube blanks using hot rolling method, specifically including heating the steel billet to 1150~1250°C. o C, and maintain for 1-4 hours. Subsequently, maintain the initial rolling temperature at 1100°C. o Rolling begins when the temperature is above C, and continues until the final rolling temperature reaches 850~950℃. o C. After rolling, allow the billet to cool naturally in air. During this process, the diameter of the hot-rolled billet should be 105% to 120% of the final product diameter, and the wall thickness should be 100% to 120% of the final product diameter. Furthermore, the microstructure of the billet after the above treatment is ferrite with a small amount of pearlite to obtain good plasticity, providing conditions for subsequent cold rolling.

[0028] Step S3: The hot-rolled tube billet is pickled, cleaned, neutralized, phosphated and saponified. Then, the steel tube billet is continuously rolled using a cold rolling mill to achieve the final required size. The dimensional tolerance requirements are: wall thickness tolerance < ±3%, outer diameter tolerance < ±0.3%.

[0029] In this step, the hot-rolled tube blank is pickled to remove surface oxides. Next, it undergoes cleaning, rinsing, neutralization, and phosphating to ensure a clean, impurity-free surface – a necessary step before cold rolling. Following this, saponification is performed. Saponification is a chemical treatment method applied to the material surface during production. Through saponification, a soap-like substance is formed on the material surface. This substance acts as a lubricant, helping to reduce friction during subsequent cold rolling, thereby protecting the material surface and improving processing quality.

[0030] Subsequently, the processed steel pipe billet is continuously rolled using a cold rolling mill. The precise dimensions required for the final product are achieved by controlling the cold rolling process parameters. Specifically, during cold rolling, the dimensions of the steel pipe are precisely controlled by precisely adjusting process parameters such as the reduction and rolling speed of the cold rolling mill. Because the material undergoes permanent plastic deformation during cold rolling, higher dimensional accuracy can be obtained. This step requires the following dimensional tolerances after cold rolling: wall thickness tolerance <±3%, outer diameter tolerance <±0.3%. This high-precision dimensional control allows the expansion sleeve to better meet engineering requirements during subsequent use, especially maintaining dimensional accuracy more stably during expansion, thereby improving its resistance to internal and external pressures. In this step, the cold rolling process not only changes the dimensions of the steel pipe but also increases the dislocation density and interface distortion energy in the material through plastic deformation. This increases the nucleation point density for recrystallization or austenitization during subsequent heat treatment, which is beneficial for grain refinement in the heat-treated microstructure, resulting in better mechanical properties.

[0031] Step S4: The cold-rolled steel pipe is subjected to heat treatment. Annealing is selected as the heat treatment method, using a gas furnace, resistance furnace, or induction heating furnace. The annealing temperature is controlled at 400°C. o C ~750 o C, time 0.5h~4h, air cool to room temperature, the final microstructure is ferrite with a small amount of carbides; or a quenching and tempering heat treatment method is used, using a gas furnace, resistance furnace or induction heating furnace, heated to 800°C. o C ~950 o C, quenching to obtain lower bainite structure, then heating to 400 o C~750 o C, time 0.5h~4h, air cool to room temperature, the final microstructure is tempered bainite.

[0032] In this step, the cold-rolled steel pipe undergoes heat treatment, with two methods available. The first is annealing, where the steel pipe is heated to 400°C–750°C using a gas-fired furnace, resistance furnace, or induction furnace, and held for 0.5 to 4 hours. Afterward, the pipe is allowed to cool naturally to room temperature in air. The resulting microstructure consists of ferrite and a small amount of carbides. Using annealing to produce expansion sleeves achieves the desired strength, plasticity, and toughness, and at a lower production cost.

[0033] The second method involves quenching and tempering. Using any of the heating equipment mentioned above, the steel pipe is heated to 800°C~950°C for quenching, then reheated to 400°C~750°C and held for 0.5 to 4 hours. Finally, it is allowed to cool naturally to room temperature. After this process, the microstructure of the steel pipe transforms into tempered bainite. Although the cost of producing expansion sleeves using the quenching and tempering method is slightly higher, the process stability is better, and while achieving the desired strength-plasticity-toughness balance, the toughness is better than that of the annealing process. Figure 2 and Figure 3 As shown, Figure 2 This is a schematic diagram of the microstructure of an expansion tube produced by an annealing process—ferrite + carbides. Figure 3 This is a schematic diagram of the microstructure of the expansion tube produced by the quenching and tempering process – tempered bainite.

[0034] Step S5: Sandblast or grind the inner wall of the heat-treated steel pipe to remove the oxide scale from the inner surface. While keeping the pipe dry, add plugs to both ends for protection. Paint the outer wall of the pipe to prevent corrosion during storage. Good inner surface quality effectively ensures pressure stability during expansion operations.

[0035] In the above scheme, the weight percentage of C (carbon) is set between 0.04% and 0.25% to ensure that the expansion sleeve has appropriate strength while matching good plasticity and toughness, so that the expansion pressure is not too high and the expansion process is stable. This carbon content range helps to form the required microstructure, which is mainly ferrite with a small amount of carbide reinforcement, thus meeting the desired performance requirements of the material. The weight percentage of Si (silicon) is set between 0.1% and 1.0% because within this range, it can effectively improve the strength and hardness of the material, while inhibiting the growth of ferrite and carbides during annealing / tempering, thus maintaining good plasticity and toughness after heat treatment, which helps to optimize the overall performance of the expansion sleeve. The weight percentage of Mn (manganese) is set between 0.5% and 1.8% because within this range, Mn can effectively improve the strength of the material and help increase hardenability; therefore, more Mn can be added appropriately when using a quenching and tempering process for thick-walled expansion tubes. The chemical composition of niobium (Nb) is set at 0.02%~0.10% by weight because within this range, Nb can effectively refine the grains of steel, forming dispersed precipitation to improve the strength of the material, without adversely affecting other properties. Phosphorus (P) and sulfur (S) are both impurity elements in steel, and their presence reduces the performance of the steel. In this design, to ensure good mechanical and processing properties of the expansion sleeve, the content of phosphorus (P) and sulfur (S) needs to be strictly controlled, i.e., P < 150 ppm and S < 80 ppm. Specifically, phosphorus causes the material to become brittle, especially at low temperatures, which is detrimental to improving the toughness of the material; while sulfur forms low-melting-point sulfide inclusions, which are easily distributed along grain boundaries during hot working, leading to hot brittleness, reducing the plasticity and toughness of the material, thus affecting the mechanical and processing properties of the final product. Therefore, to ensure good mechanical and processing properties of the expansion sleeve, the content of P and S needs to be strictly controlled, with P < 100 ppm and S < 50 ppm being optimal in actual production.

[0036] In optional embodiments, the technical solution also includes Cr: 0.1%~1.5% and Ni: 0.1%~3.0%. In this solution, the weight percentage of Cr is 0.1%~1.5%, and the weight percentage of Ni is 0.1%~3.0%. Adding Cr has a certain strengthening effect and can significantly improve the corrosion resistance of the expansion tube and improve surface quality. Adding Ni can improve the plasticity and toughness of the material and also improve its corrosion resistance to a certain extent, making it perform better under specific application conditions.

[0037] In the optional embodiment, the technical solution also includes: Cu: 0.1%~1.0%, Ti: 0.01~0.02%, and V: 0.01~0.2%. In this solution, for low expansion pressure and high resistance to external extrusion expansion sleeves after expansion, the chemical composition weight percentage of copper (Cu) is set to 0.1%~1.0%, the chemical composition weight percentage of titanium (Ti) is set to 0.01~0.02%, and the chemical composition weight percentage of vanadium (V) is set to 0.01%~0.2%, mainly to optimize material properties. Specifically, copper (Cu), as an alloying element, can improve the corrosion resistance of steel and also has a certain effect on improving the strength and toughness of the material. However, if the content is too high, it is easy to form a copper-rich phase with a low melting point at the interface, leading to deterioration of hot working performance. Generally, Cu and Ni are added together, with the amount of Cu added being half that of Ni. The technical solution of this application proposes a more stringent requirement: the Cu content is less than 40% of the Ni content. Titanium (Ti), added to steel as a microalloying element, primarily forms precipitates through a combination of carbon and nitrogen. This inhibits austenite growth at high temperatures, resulting in a finer austenite structure and improving the performance of hot-rolled tubes. Vanadium (V), added to steel as a microalloying element, mainly plays a role in precipitation strengthening. Simultaneously, V can refine grains to some extent, thus improving material strength without significantly compromising toughness. In summary, by rationally controlling the addition amounts of copper, titanium, and vanadium, the key performance indicators of expansion sleeves can be effectively adjusted without significantly increasing costs.

[0038] In summary, the technical solution of this invention ensures the basic properties of the material by controlling the chemical composition within a specific range (e.g., C: 0.04%~0.25%, Si: 0.1%~1.0%, Mn: 0.5%~1.8%, Nb: 0.02%~0.10%). The production process employs hot rolling + cold rolling + heat treatment, which not only improves dimensional accuracy (wall thickness tolerance <±4%, outer diameter tolerance <±0.4%, straightness <0.2mm / m) but also guarantees good mechanical properties of the material. The dimensional accuracy of the expansion sleeve is a key factor in ensuring stable expansion pressure. Furthermore, the high dimensional accuracy of the steel pipe before expansion can inhibit further deterioration of dimensional accuracy during expansion, thus achieving good dimensional accuracy after expansion as well. This is the most effective measure, besides strength, to improve the steel pipe's resistance to internal and external pressure damage after expansion. In the heat treatment process, annealing can be chosen to obtain a final microstructure of refined ferrite with a small amount of carbides, resulting in a good balance of strength, toughness, and plasticity. Alternatively, quenching and tempering can be selected to obtain tempered bainite, which is essentially ferrite with a small amount of carbides, differing only in its distribution morphology. Although the cost is slightly higher, the impact toughness is better. Using both processes, the yield strength of the expansion tube can be controlled between 300 and 500 MPa, ensuring the reliability of thread processing while preventing excessive expansion pressure and guaranteeing the high strength requirements after expansion. Example 1

[0039] The chemical composition by weight percentage is: C: 0.08%, Si: 0.3%, Mn: 1.0%, Nb: 0.03%, Ni: 0.5%, P < 120 ppm, S < 60 ppm, with the balance being Fe and unavoidable impurities. Steel is smelted in a converter, and billets are produced by continuous casting. Tube blanks are produced by hot rolling, with the billet heating temperature at 1200°C. o C, hold at temperature for 2 hours, initial rolling temperature 1140℃ o C, final rolling temperature at 900 o C. After rolling, the tube blank is naturally cooled in air; the diameter of the hot-rolled tube blank is Φ245mm×13.5mm; the microstructure of the hot-rolled tube blank is ferrite + a small amount of pearlite; it undergoes pickling, cleaning, neutralization, phosphating and saponification, and then the steel tube blank is continuously rolled using a cold rolling mill. The cold-rolled dimensions are Φ219mm×12.4mm, with a wall thickness tolerance of <±2.5% and an outer diameter tolerance of <±0.2%; the heat treatment is 680. oC annealing for 1 hour, followed by air cooling to room temperature, resulted in a final microstructure of ferrite with a small amount of carbides. The heat-treated steel pipe was then straightened using a multi-roller straightener, achieving dimensional accuracy of wall thickness tolerance <±3%, outer diameter tolerance <±0.3%, and straightness <0.15 mm / m. The inner wall of the heat-treated steel pipe was sandblasted to remove oxide scale. While maintaining dryness, pipe plugs were added to both ends of the pipe for protection. The outer wall of the steel pipe was then painted for protection against corrosion during storage.

[0040] Example 1 is characterized by its excellent comprehensive mechanical properties. Specifically, the steel pipe in this example has a yield strength of 330 MPa, a tensile strength of 460 MPa, a uniform elongation of 18%, an elongation after fracture of 40%, and a Charpy impact energy of 220 J. Furthermore, it exhibits an expansion pressure of 20-21 MPa at a 15% expansion rate, an impact energy greater than 150 J after expansion, resistance to external pressure of not less than 20 MPa, and resistance to internal pressure of not less than 50 MPa. These data demonstrate that expansion sleeve materials meeting specific performance requirements can be produced through hot rolling, cold rolling, and annealing processes. Example 2

[0041] The chemical composition by weight percentage is: C: 0.10%, Si: 0.3%, Mn: 1.4%, Nb: 0.02%, Cr: 0.4%, P < 100 ppm, S < 50 ppm, with the balance being Fe and unavoidable impurities. Steel is smelted in a converter, and billets are produced by continuous casting. Tube billets are produced by hot rolling at a heating temperature of 1220°C. o C, hold at heat for 2 hours, initial rolling temperature 1150℃ o C, final rolling temperature at 910 o C. After rolling, the tube blank is naturally cooled in air; the diameter of the hot-rolled tube blank is Φ219mm×12.5mm; the microstructure of the hot-rolled tube blank is ferrite + a small amount of pearlite; it undergoes pickling, cleaning, neutralization, phosphating and saponification, and then the steel tube blank is continuously rolled using a cold rolling mill. The cold-rolled dimensions are Φ194mm×11.4mm, with wall thickness tolerance <±2% and outer diameter tolerance <±0.2%; the heat treatment adopts the quenching and tempering process, 900 o C quenching, 690 o Tempered at C for 1 hour, then air-cooled to room temperature, the final microstructure was tempered bainite (e.g., Figure 3 (As shown); The heat-treated steel pipe is straightened using a multi-roller straightener. After straightening, the dimensional accuracy reaches a wall thickness tolerance of <±3%, an outer diameter tolerance of <±0.3%, and a straightness of <0.15mm / m. The inner wall of the heat-treated steel pipe is sandblasted to remove the oxide scale on the inner surface of the steel pipe. While keeping it dry, pipe plugs are added to both ends of the steel pipe for protection. The outer wall of the steel pipe is painted for protection to prevent corrosion during storage.

[0042] Compared to Example 1, the steel pipe of Example 2 has higher strength, with a yield strength of 420MPa, a tensile strength of 550MPa, a uniform elongation of 16%, an elongation after fracture of 44%, a Charpy impact energy of 310J, an expansion pressure of 24-25MPa at a 15% expansion rate, an impact energy greater than 200J after expansion, an external pressure resistance of 24MPa, and an internal pressure resistance of not less than 60MPa.

[0043] Compared to Example 1, this embodiment achieves higher strength by adding more C and Mn, with both yield strength (420 MPa) and tensile strength (550 MPa) increasing by nearly 100 MPa, while the plasticity of the steel pipe does not decrease. The addition of 0.4% Cr increases the product's corrosion resistance and achieves better surface quality. The heat treatment using a quenching and tempering method increases toughness by 90 J. Due to the increased strength, the expansion pressure during the expansion process is also increased, but the process remains stable. Furthermore, the impact toughness and resistance to internal pressure and external extrusion after expansion are correspondingly improved.

[0044] This technical solution is designed to address problems encountered during the use of expansion sleeves, particularly to achieve low expansion pressure and high resistance to external extrusion after expansion. This solution improves the overall performance of the expansion sleeve by optimizing material composition and manufacturing processes, such as increasing dimensional accuracy and maintaining appropriate strength, thereby better meeting practical application needs. The products manufactured using this expansion tube production technology have a final microstructure of refined ferrite with a small amount of carbides, and a strength generally within the range of 300~500MPa. The control method is simple, and performance fluctuations are minimal. This ensures that the strength before expansion reaches over 300MPa while preventing excessive pressure during expansion. More importantly, the use of hot rolling + cold rolling + heat treatment significantly improves dimensional accuracy compared to existing products, with wall thickness tolerance <±4%, outer diameter tolerance <±0.4%, and straightness <0.2mm / m (standard hot-rolled tube wall thickness tolerance <±8%, outer diameter tolerance <±1%, straightness <0.5mm / m). Improving the dimensional accuracy of the steel pipe before expansion effectively improves the dimensional accuracy of the expanded steel pipe, which is crucial for enhancing the pipe's resistance to higher internal and external pressures. Therefore, the technical solution in this application uses low-alloy additives (low-cost materials) and achieves an excellent match between material performance and product quality with a limited increase in steel pipe production costs, thus meeting the technical requirements of low expansion pressure and high resistance to external extrusion after expansion of the expansion sleeve.

[0045] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low expansion pressure and high resistance to external extrusion expansion sleeve after expansion, characterized in that, The chemical composition by weight percentage is C: 0.04%~0.25%, Si: 0.1%~1.0%, Mn: 0.5%~1.8%, Nb: 0.02%~0.10%, P<150ppm, S<80ppm, with the balance being Fe and unavoidable impurities; The production method of this low expansion pressure and high resistance to external extrusion expansion sleeve after expansion specifically includes: Step S1: Steel is smelted in a converter or electric furnace according to the composition, and billets are produced by continuous casting. Step S2: Produce tube blanks using hot rolling method, with the billet heating temperature at 1150~1250℃. o C, hold at temperature for 1-4 hours, initial rolling temperature at 1100℃ o C and above, with a final rolling temperature of 850~950℃. o C. After rolling, the tube blank is naturally cooled in air; the diameter of the hot-rolled tube blank is 105%~120% of the diameter of the final product, and the wall thickness is 100%~120% of the diameter of the final product; the tube blank microstructure consists of ferrite + a small amount of pearlite. Step S3: The hot-rolled billet is pickled, cleaned, neutralized, phosphated, and saponified. Then, the billet is continuously rolled using a cold rolling mill to achieve the final required dimensions. The dimensional tolerances are: wall thickness tolerance < ±3%, outer diameter tolerance < ±0.3%. Step S4: The cold-rolled steel pipe is subjected to heat treatment. Annealing is selected as the heat treatment method, using a gas furnace, resistance furnace, or induction heating furnace. The annealing temperature is controlled at 400°C. o C ~750 o C, time 0.5h~4h, air cool to room temperature, the final microstructure is ferrite with a small amount of carbides; or a quenching and tempering heat treatment method is used, using a gas furnace, resistance furnace or induction heating furnace, heated to 800°C. o C ~950 o C, quenching to obtain lower bainite structure, then heating to 400 o C~750 o C, time 0.5h~4h, air cool to room temperature, the final microstructure is tempered bainite; Step S5: Use a multi-roller straightener to straighten the heat-treated steel pipe. After straightening, the dimensional accuracy should reach wall thickness tolerance <±4%, outer diameter tolerance <±0.4%, and straightness <0.2mm / m. Step S6: Sandblast or grind the inner wall of the heat-treated steel pipe to remove the oxide scale on the inner surface of the steel pipe. While keeping it dry, add pipe plugs to both ends of the steel pipe for protection. Spray paint on the outer wall of the steel pipe for protection to prevent corrosion during storage.

2. The low expansion pressure and high resistance to external extrusion expansion sleeve according to claim 1, characterized in that, It also includes Cr: 0.1%~1.5%, Ni: 0.1%~3.0%.

3. The low expansion pressure and high resistance to external extrusion expansion sleeve according to claim 2, characterized in that, Also includes: Cu: 0.1%~1.0%, Ti: 0.01%~0.02%, and V: 0.01%~0.2%.

4. The low expansion pressure and high resistance to external extrusion expansion sleeve according to claim 3, characterized in that, The Cu content shall not exceed 40% of the Ni content.

Images