Intensity-only expanded connection method for carbon steel pipe plate and carbon steel heat exchange pipe

Abstract

The invention relates to the technical field of strength expanded connection processes, in particular to a strength expanded connection method for a carbon steel pipe plate and a carbon steel heat exchange pipe. The method is applied to expanded connection of a 16MnIII carbon steel tube plate and a 10 # carbon steel heat exchange tube, and comprises the following steps: S1, selecting mechanical properties of a base material; s2, the outer surface of the heat exchange tube is treated; s3, expanded connection grooves are machined in tube plate holes; and S4, the heat exchange tube is in expanded connection with the tube plate. According to the method, the mechanical property of base metal is selected, the outer surface of the heat exchange tube is carefully treated, the tube plate hole and the expanded connection groove are precisely machined, and finally hydraulic expanded connection is adopted, so that the heat exchange tube is uniformly expanded in the tube plate hole and is tightly combined with the expanded connection groove; the step of detecting the expanded connection sealing quality is added, the expanded connection quality between the carbon steel pipe plate and the carbon steel heat exchange pipe is ensured, whether cracks or damage or leakage exists at the connecting position or not is verified through appearance inspection and a pressure test, and therefore the reliability and safety of connection are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of strength expansion technology, and in particular to a strength expansion connection method for a carbon steel tube sheet and a carbon steel heat exchange tube. Background Art

[0002] The shell and tube heat exchanger used in a specific oil refining unit uses low alloy steel 16MnIII material in accordance with NB / T47008-2017 standard, while the heat exchange tube uses carbon steel 10# in accordance with GB / T9948-2013 standard, with a specification of φ25×3.4mm. Given that the equipment needs to withstand severe stress corrosion environment, the traditional strength welding or sealing welding connection method is not suitable for this scenario because the welding residual stress induced causes weld cracks, which in turn causes equipment failure. Therefore, it was decided to use expansion as the only connection method between the tube sheet and the heat exchange tube. It is worth noting that in the field of pressure vessels, it is rare for carbon steel heat exchange tubes to be connected to tube sheets only by expansion, especially when the heat exchange tube specification is such as φ25×3.4mm, and its wall thickness to diameter ratio is relatively large, the difficulty of expansion increases significantly. As the core of the heat exchange system, the connection quality of the heat exchanger is directly related to its overall performance and long-term reliability. Faced with this challenge, technicians in this field are constantly seeking technological breakthroughs. Although there are connection processes such as those described in Chinese patent CN104084673A, these solutions are still insufficient when dealing with specific working conditions; although welding is strong, it is accompanied by thermal stress and corrosion risks; simple expansion joints are difficult to meet strength requirements under extreme conditions. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for strength expansion connection between a carbon steel tube sheet and a carbon steel heat exchange tube.

[0004] The technical solution adopted by the present invention is as follows: A strength expansion connection method for a carbon steel tube sheet and a carbon steel heat exchange tube, which is applied to the expansion connection of a 16MnIII carbon steel tube sheet and a 10# carbon steel heat exchange tube, comprises the following steps: S1. Selection of mechanical properties of parent materials: The carbon steel tube sheet is selected as 16MnIII material, and the carbon steel heat exchange tube is selected as 10# carbon steel with a specification of φ25×3.4mm; the hardness range of the carbon steel tube sheet is 140~160HBW, and the hardness of the carbon steel heat exchange tube does not exceed 110HBW, ensuring that the hardness difference between the two is ≥30HBW; S2. Heat exchange tube outer surface treatment: Use a 60-80 mesh flap wheel to perform preliminary grinding on the outer surface of the insertion side of the carbon steel heat exchange tube; use a 300 mesh or larger flap wheel for secondary grinding to ensure that the outer surface of the insertion side of the carbon steel heat exchange tube is smooth and free of rust; S3. Processing expansion grooves in tube sheet holes: Use a CNC drilling machine to process tube sheet holes on the carbon steel tube sheet, ensure that the tube hole size is φ25.25±0.1mm, and control the inner surface roughness of the tube hole to not exceed 6.3μm, and process expansion grooves in the tube sheet holes; S4. Expansion of heat exchange tubes and tube sheets: Use hydraulic expansion equipment and set the expansion pressure to 210~230MPa to make the carbon steel heat exchange tubes expand evenly in the tube sheet holes and closely combine with the expansion grooves to form a sealed connection.

[0005] This technical solution selects the mechanical properties of the base material, carefully processes the outer surface of the heat exchange tube, accurately processes the tube sheet holes and expansion grooves, and finally uses hydraulic expansion to make the heat exchange tube expand evenly in the tube sheet hole and tightly combine with the expansion groove. Specifically, in step S1, 16MnIII is a low-alloy high-strength steel. 10# carbon steel is a common carbon structural steel. As the thickness and diameter of the heat exchange tube increase, the difficulty of expansion increases exponentially. Ensuring a certain hardness difference (≥30HBW) between the carbon steel tube sheet and the carbon steel heat exchange tube is to make it easier for the carbon steel heat exchange tube to undergo plastic deformation during the expansion process, while the carbon steel tube sheet maintains a high rigidity, thereby forming a good sealing effect. In step S2, the roughness of the outer surface of the heat exchange tube insertion side is gradually reduced by grinding with a thousand-blade wheel of different mesh sizes until it reaches a smooth and rust-free state. The purpose is to reduce the friction resistance during the expansion process, improve the quality of the expansion, and prevent loose connections or leakage caused by residual rust. In step S3, the processing size of the tube sheet hole (φ25.25±0.1mm) and the roughness of the inner surface of the tube hole are selected. The roughness (≤6.3μm) is to ensure that the heat exchange tube can be accurately inserted into the tube sheet hole and maintain a stable position during the expansion process; the expansion groove is processed in the tube sheet hole to provide an additional mechanical locking effect during the expansion process; when the heat exchange tube expands under the action of hydraulic pressure, its expanded part will be embedded in the expansion groove to form a tighter and more reliable connection; the shape, size and number of the expansion groove need to be selected according to the specific process requirements; in step S4, a high pressure (210~230MPa) is applied to the heat exchange tube by using a hydraulic expansion device to make the heat exchange tube expand uniformly in the tube sheet hole, and the expansion deformation is plastic, that is, after unloading the pressure, the heat exchange tube will maintain its expanded shape and size; as the heat exchange tube expands, a tight sealing structure is formed between its outer surface and the inner surface of the tube sheet hole.

[0006] In addition, the strength expansion connection method of the carbon steel tube sheet and the carbon steel heat exchange tube proposed in the present invention also has the following additional technical features: According to one embodiment of the present invention, the present invention further comprises the following subsequent steps: S5. Expansion seal quality inspection: After the expansion is completed, perform an appearance inspection on the joint to ensure that there are no cracks or damage; set the test pressure to 3MPa and observe whether there is any leakage at the joint.

[0007] This technical solution is used to ensure the quality of the expansion connection between the carbon steel tube sheet and the carbon steel heat exchange tube by adding an expansion seal quality inspection step, and to verify whether there are cracks, damage or leakage at the connection through appearance inspection and pressure test, thereby ensuring the reliability and safety of the connection.

[0008] According to one embodiment of the present invention, in step S2, the carbon steel heat exchange tube is divided into a tube side and a shell side; both the tube side and the shell side are provided with a guide angle of 60°; wherein the shell side of the carbon steel heat exchange tube and the insertion side of the carbon steel heat exchange tube are plugged into and matched with each other.

[0009] This technical solution sets a 60° guide angle on the tube side and shell side of the carbon steel heat exchange tube, and specifically points out the plug-in matching mode between the shell side and the insertion side, so as to optimize the insertion and positioning process of the heat exchange tube, reduce the insertion resistance, and improve the expansion efficiency and connection quality.

[0010] According to an embodiment of the present invention, in step S3, at least two expansion grooves are provided in the tube sheet hole.

[0011] This technical solution emphasizes that at least two expansion grooves are set in the tube sheet hole to further enhance the strength and sealing of the expansion connection; multiple expansion grooves provide more mechanical locking points, so that the heat exchange tubes are more firmly embedded in the tube sheet hole during the expansion process.

[0012] According to one embodiment of the present invention, in step S3, the expansion groove is a groove opened on the inner wall of the tube sheet hole; the width of the expansion groove is 9-10 mm, the depth of the expansion groove is 0.5 mm, and the tolerance range is -0.05-0 mm.

[0013] This technical solution defines the expansion groove as a groove opened on the inner wall of the tube sheet hole to provide accurate expansion depth and width. The structure of the expansion groove can also be customized according to different process requirements and connection conditions to optimize the connection effect.

[0014] According to an embodiment of the present invention, in step S4, the carbon steel heat exchange tube expands under the action of the hydraulic expansion equipment, and the expanded position is embedded in the expansion groove to form a sealing structure.

[0015] This technical solution is used to directly explain the core mechanism of the expansion connection by clarifying that during the hydraulic expansion process, the expanded position of the carbon steel heat exchange tube will be embedded in the expansion groove to form a sealing structure. The embedded sealing structure can effectively prevent medium leakage and ensure high sealing performance at the connection.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) By selecting the mechanical properties of the base material, carefully processing the outer surface of the heat exchange tube, accurately processing the tube sheet holes and expansion grooves, and finally using hydraulic expansion, the heat exchange tube can be evenly expanded in the tube sheet hole and tightly combined with the expansion groove.

[0017] (2) By adding the expansion seal quality inspection step, the quality of the expansion connection between the carbon steel tube sheet and the carbon steel heat exchange tube is ensured. By visual inspection and pressure test, it is verified whether there are cracks, damage or leakage at the connection, so as to ensure the reliability and safety of the connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow diagram of the method of the present invention.

[0019] Figure 2 This is the hydraulic expansion diagram of carbon steel tube sheet and carbon steel heat exchange tube.

[0020] Figure 3 This is the processing drawing of carbon steel tube plate with expansion groove.

[0021] In the figure: 1. carbon steel heat exchange tube; 11. tube side; 12. shell side; 2. carbon steel tube sheet; 3. expansion groove. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

[0023] Example 1 like Figure 1 As shown, this embodiment provides a strength expansion connection method for a carbon steel tube sheet and a carbon steel heat exchange tube, which is applied to the expansion connection of a 16MnIII carbon steel tube sheet and a 10# carbon steel heat exchange tube, and includes the following steps: S1. Selection of mechanical properties of parent materials: The carbon steel tube sheet 2 is selected as 16MnIII material, and the carbon steel heat exchange tube 1 is selected as 10# carbon steel with a specification of φ25×3.4mm; the hardness range of the carbon steel tube sheet 2 is 140~160HBW, and the hardness of the carbon steel heat exchange tube 1 does not exceed 110HBW, ensuring that the hardness difference between the two is ≥30HBW; S2. Heat exchange tube outer surface treatment: Use a 60-80 mesh flap wheel to perform preliminary grinding on the outer surface of the insertion side of the carbon steel heat exchange tube 1; use a 300 mesh or larger flap wheel for secondary grinding to ensure that the outer surface of the insertion side of the carbon steel heat exchange tube 1 is smooth and free of rust; S3. Processing expansion grooves in tube sheet holes: Use a CNC drilling machine to process tube sheet holes on the carbon steel tube sheet 2, ensuring that the tube hole size is φ25.25±0.1mm, and the inner surface roughness of the tube hole is controlled to be no more than 6.3μm, and process expansion grooves 3 in the tube sheet holes, such as Figure 3 As shown; S4. Expansion of heat exchange tube and tube sheet: Use hydraulic expansion equipment and set the expansion pressure to 210~230MPa to make the carbon steel heat exchange tube 1 expand evenly in the tube sheet hole and closely combine with the expansion groove 3 to form a sealed connection. Figure 2 shown.

[0024] like Figures 1 to 3 As shown, this technical solution selects the mechanical properties of the base material, carefully processes the outer surface of the heat exchange tube, accurately processes the tube sheet hole and the expansion groove 3, and finally uses hydraulic expansion to make the heat exchange tube expand uniformly in the tube sheet hole and tightly combine with the expansion groove 3. Specifically, in step S1, 16MnIII is a low-alloy high-strength steel, 10# carbon steel is a common carbon structural steel. As the thickness and diameter of the heat exchange tube increase, the difficulty of expansion increases exponentially. Ensure that there is a certain hardness difference (≥30HBW) between the carbon steel tube sheet 2 and the carbon steel heat exchange tube 1, so that during the expansion process, the carbon steel heat exchange tube 1 can be more easily plastically deformed, while the carbon steel tube sheet 2 maintains a high rigidity, thereby forming a good sealing effect. In step S2, the roughness of the outer surface of the insertion side of the heat exchange tube is gradually reduced by grinding with a thousand-blade wheel of different meshes until it reaches a smooth and rust-free state, in order to reduce the friction resistance during the expansion process, improve the quality of expansion, and prevent loose connection or leakage caused by residual rust. In step S3, select the processing size of the tube sheet hole (φ25.25±0.1mm) and the inner surface of the tube hole. The roughness (≤6.3μm) is to ensure that the heat exchange tube can be accurately inserted into the tube sheet hole and maintain a stable position during the expansion process; the expansion groove 3 is processed in the tube sheet hole to provide an additional mechanical locking effect during the expansion process; when the heat exchange tube expands under the action of hydraulic pressure, its expanded part will be embedded in the expansion groove 3 to form a tighter and more reliable connection; the shape, size and number of the expansion groove 3 need to be selected according to the specific process requirements; in step S4, a high pressure (210~230MPa) is applied to the heat exchange tube by using a hydraulic expansion device to make the heat exchange tube expand uniformly in the tube sheet hole, and the expansion deformation is plastic, that is, after unloading the pressure, the heat exchange tube will maintain its expanded shape and size; as the heat exchange tube expands, a tight sealing structure is formed between its outer surface and the inner surface of the tube sheet hole.

[0025] In addition, the strength expansion connection method of the carbon steel tube sheet and the carbon steel heat exchange tube proposed in the present invention also has the following additional technical features: According to one embodiment of the present invention, the present invention further comprises the following subsequent steps: S5. Expansion seal quality inspection: After the expansion is completed, perform an appearance inspection on the joint to ensure that there are no cracks or damage; set the test pressure to 3MPa and observe whether there is any leakage at the joint.

[0026] This technical solution ensures the quality of the expansion connection between the carbon steel tube sheet 2 and the carbon steel heat exchange tube 1 by adding an expansion seal quality inspection step, and verifies whether there are cracks, damage or leakage at the connection through appearance inspection and pressure test, thereby ensuring the reliability and safety of the connection.

[0027] According to one embodiment of the present invention, in step S2, the carbon steel heat exchange tube 1 is divided into a tube side 11 and a shell side 12; the tube side 11 and the shell side 12 are both provided with a guide angle of 60°; wherein the shell side 12 of the carbon steel heat exchange tube 1 and the insertion side of the carbon steel heat exchange tube 1 are plugged into and matched with each other.

[0028] The technical solution sets a 60° guide angle on the tube side 11 and the shell side 12 of the carbon steel heat exchange tube 1, and particularly points out the plug-in matching mode between the shell side 12 and the insertion side, so as to optimize the insertion and positioning process of the heat exchange tube, reduce the insertion resistance, and improve the expansion efficiency and connection quality.

[0029] According to an embodiment of the present invention, in step S3, at least two expansion grooves 3 are provided in the tube sheet hole.

[0030] The technical solution emphasizes that at least two expansion grooves 3 are provided in the tube sheet hole to further enhance the strength and sealing of the expansion connection; multiple expansion grooves 3 provide more mechanical locking points, so that the heat exchange tubes are more firmly embedded in the tube sheet hole during the expansion process.

[0031] According to one embodiment of the present invention, in step S3, the expansion groove 3 is a groove opened on the inner wall of the tube sheet hole; the width of the expansion groove is 9-10 mm, the depth of the expansion groove is 0.5 mm, and the tolerance range is -0.05-0 mm.

[0032] This technical solution defines the expansion groove 3 as a groove opened on the inner wall of the tube sheet hole to provide accurate expansion depth and width. The structure of the expansion groove 3 can also be customized according to different process requirements and connection conditions to optimize the connection effect.

[0033] According to an embodiment of the present invention, in the step S4, the carbon steel heat exchange tube 1 is expanded under the action of the hydraulic expansion equipment, and the expanded position is embedded in the expansion groove 3 to form a sealing structure.

[0034] This technical solution clarifies that during the hydraulic expansion process, the expanded position of the carbon steel heat exchange tube 1 will be embedded in the expansion groove 3 to form a sealing structure, which is used to directly explain the core mechanism of the expansion connection. The embedded sealing structure can effectively prevent medium leakage and ensure high sealing performance at the connection.

[0035] Although the present invention is described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A strength expansion connection method for carbon steel tube sheet and carbon steel heat exchange tube, which is applied to the expansion connection of 16MnIII carbon steel tube sheet and 10# carbon steel heat exchange tube, characterized in that: The steps include: S1. Selection of mechanical properties of parent materials: The carbon steel tube sheet (2) is selected as 16MnIII material, and the carbon steel heat exchange tube (1) is selected as 10# carbon steel with a specification of φ25×3.4mm; the hardness range of the carbon steel tube sheet (2) is 140~160HBW, and the hardness of the carbon steel heat exchange tube (1) does not exceed 110HBW, ensuring that the hardness difference between the two is ≥30HBW; S2. Heat exchange tube outer surface treatment: Use a 60-80 mesh flap wheel to perform preliminary grinding on the outer surface of the insertion side of the carbon steel heat exchange tube (1); use a 300 mesh flap wheel or above to perform secondary grinding to ensure that the outer surface of the insertion side of the carbon steel heat exchange tube (1) is smooth and free of rust; S3. Processing expansion grooves in tube sheet holes: Use a CNC drilling machine to process tube sheet holes on the carbon steel tube sheet (2), ensure that the tube hole size is φ25.25±0.1mm, and control the inner surface roughness of the tube hole to not exceed 6.3μm, and process expansion grooves (3) in the tube sheet holes; S4. Expansion of heat exchange tubes and tube sheets: Use hydraulic expansion equipment and set the expansion pressure to 210-230 MPa to make the carbon steel heat exchange tubes (1) expand evenly in the tube sheet holes and tightly combine with the expansion grooves (3) to form a sealed connection.

2. The strength expansion connection method for carbon steel tube sheet and carbon steel heat exchange tube according to claim 1, characterized in that: The following follow-up steps are also included: S5. Expansion joint seal quality inspection: After the expansion joint is completed, conduct an appearance inspection on the joint to ensure that there are no cracks or damage; set the test pressure to 3MPa and observe whether there is any leakage at the joint.

3. The strength expansion connection method for carbon steel tube sheet and carbon steel heat exchange tube according to claim 1, characterized in that: In step S2, the carbon steel heat exchange tube (1) is divided into a tube side (11) and a shell side (12); the tube side (11) and the shell side (12) are both provided with a guide angle of 60°; wherein the shell side (12) of the carbon steel heat exchange tube (1) and the insertion side of the carbon steel heat exchange tube (1) are plugged into and matched with each other.

4. The strength expansion connection method for carbon steel tube sheet and carbon steel heat exchange tube according to claim 3, characterized in that: In the step S3, at least two expansion grooves (3) are provided in the tube sheet hole.

5. The strength expansion connection method of carbon steel tube sheet and carbon steel heat exchange tube according to claim 1 or 4, characterized in that: In the step S3, the expansion groove (3) is a groove opened on the inner wall of the tube sheet hole; the width of the expansion groove (3) is 9-10 mm, the depth of the expansion groove (3) is 0.5 mm, and the tolerance range is -0.05-0 mm.

6. The method for connecting a carbon steel tube sheet and a carbon steel heat exchange tube by strength expansion only according to claim 5, characterized in that: In the step S4, the carbon steel heat exchange tube (1) expands under the action of the hydraulic expansion equipment, and the expanded position is embedded in the expansion groove (3) to form a sealing structure.

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