Machining method for large-helix-angle internal-thread copper pipe

Abstract

The invention discloses a machining method for a large-helix-angle internal-thread copper pipe, and relates to the technical field of thread copper pipe machining, and the machining method comprises the steps that a round copper pipe is adopted as a pipe blank, and surface cleaning and straightness correction treatment are conducted on the pipe blank; clamping the treated pipe blank in spinning forming equipment, sleeving the front end of the pipe blank into a threaded core head, and guiding and positioning by matching with a moving core; the spinning equipment is started, continuous cold extrusion is carried out on the pipe blank through the external spinning ring under the synergistic effect of rotating motion and axial feeding, and an initial thread structure with a preset lead angle is formed along the inner wall of the pipe blank in the rotating process; during cold extrusion forming, the threaded core head and the moving core jointly maintain inner cavity supporting and tooth profile transmission; after spinning forming is completed, the copper pipe with the internal threads is guided into a sizing procedure, and size finishing is conducted on the outer diameter of the pipe body through a precise sizing die; the wall thickness distribution of the pipe body is synchronously controlled in the sizing process, so that the thickness of the bottom wall is uniform and meets the structural strength requirement.

Description

Technical Field

[0001] This invention relates to the field of threaded copper tube processing technology, and in particular to a processing method for internally threaded copper tubes with a large helix angle. Background Technology

[0002] Threaded copper tube processing technology refers to the manufacturing technology of processing a continuous spiral tooth structure on the inner or outer wall of a copper tube through plastic forming methods. It is mainly used to improve the heat transfer efficiency between the refrigerant and the metal tube wall in a heat exchanger.

[0003] In the field of threaded copper tube processing, existing technologies that increase the number of teeth or thin the bottom wall will reduce the structural strength of the tube body. During the spinning process, tube wall cracking, tooth collapse, or uneven bottom wall thickness are likely to occur. This solution needs to meet the technical requirements of high number of teeth, ultra-thin bottom wall, and large helix angle at the same time. Traditional processes cannot achieve this. Moreover, when spinning the internal threads of thin-walled copper tubes, the external radial pressure is prone to causing local concavity, ellipticization, or eccentricity of the tube body, resulting in incomplete thread forming and excessive wall thickness deviation, which affects the pressure resistance and consistency of the product. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a processing method for copper tubes with large helix angle internal threads. In the prior art, increasing the number of teeth or thinning the bottom wall reduces the structural strength of the tube body, and tube wall cracking, tooth collapse, or uneven bottom wall thickness are prone to occur during spinning. This solution needs to meet the technical requirements of high number of teeth, ultra-thin bottom wall, and large helix angle at the same time, which traditional processes cannot achieve. Moreover, when spinning thin-walled copper tubes with internal threads, the external radial pressure can easily cause local concavity, ellipticization, or eccentricity of the tube body, resulting in incomplete thread forming, excessive wall thickness deviation, and affecting the pressure resistance and consistency of the product.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for processing a copper tube with a large helix angle internal thread, comprising: A circular copper tube is used as the tube blank, and the tube blank is subjected to surface cleaning and straightness correction treatment; The processed tube blank is clamped in the spinning forming equipment, and its front end is fitted with a threaded mandrel for guidance and positioning with the moving mandrel. Start the spinning equipment and use the combined action of rotational motion and axial feed to continuously cold extrude the tube blank through the external spinning ring, so that the tube blank forms an initial thread structure with a predetermined helix angle along the inner wall during the rotation process; During cold extrusion forming, the threaded core and the floating core work together to maintain the internal cavity support and tooth profile transmission. After spinning is completed, the copper tube with internal threads is introduced into the sizing process, and the outer diameter of the tube is dimensionally adjusted by a precision sizing die. During the sizing process, the pipe wall thickness distribution is controlled synchronously to ensure that the bottom wall thickness is uniform and meets the structural strength requirements; A finished copper tube with a large helix angle thread structure on its inner surface is obtained.

[0007] In a preferred embodiment of the processing method for the large helix angle internally threaded copper tube of the present invention, the threaded mandrel is used to form the tooth profile of the internal thread during the spinning process, and the specific steps are as follows: The outer surface of the threaded mandrel is designed to have a continuous spiral groove structure, wherein the spiral groove includes a guide section, a forming section and a shaping section; The threaded mandrel is installed at the front end of the spindle of the spinning equipment, so that the axis is consistent with the direction of movement of the tube blank; During the clamping process, the front end of the tube blank is slid into the guide section to achieve initial positioning; After spinning begins, the tube blank rotates with the spindle, and the forming section of the threaded core contacts the inner wall of the tube blank. Through cold extrusion, the copper material undergoes plastic deformation along the groove, gradually replicating the corresponding tooth shape. At the end of the spinning process, the shaping section makes fine adjustments to the formed thread to eliminate dimensional deviations caused by material springback.

[0008] In a preferred embodiment of the processing method for the large helix angle internally threaded copper tube of the present invention, the wandering mandrel is disposed inside the tube blank and abuts against the threaded mandrel head to support the inner wall of the tube blank and maintain coaxiality during the forming process. The specific steps are as follows: A hollow cylindrical core is selected, with a tapered inlet at the front end, a constant diameter support section in the middle, and a connection interface at the tail end that matches the threaded core head. While the tube blank is being fitted with the threaded mandrel, the pendant is inserted from the rear end of the tube blank so that its front end is mated with the tail end of the threaded mandrel. During the spinning process, the walking core moves synchronously with the tube blank, and its equal-diameter support section is always located upstream of the spinning deformation zone, providing radial support to the inner cavity of the tube blank that is about to enter the spinning zone. The support provided by the core prevents the tube blank from developing localized depressions or uneven wall thickness under external pressure.

[0009] In a preferred embodiment of the processing method for large helix angle internally threaded copper tubes according to the present invention, the spinning equipment achieves thread forming through a combined motion of spindle rotation and axial feeding of the spinning ring, specifically comprising the following steps: Start the spindle drive to make the tube blank move at a constant angular velocity. Rotates about its own axis; Simultaneously activate the feed mechanism to make the spinning ring move at a linear velocity. It is advanced along the axial direction of the tube blank and enters the gap between the tube blank and the outer mold; The inner surface of the spinning ring is a cylindrical working surface with a diameter slightly larger than the target outer diameter, applying radial pressure to the tube blank during the advancement process. ; Under pressure Under the action, the tube blank material is compressed and flows inward, adhering to the surface of the threaded mandrel to form the initial thread tooth shape; The rotational motion and axial feed are performed synchronously, and the two maintain a fixed motion relationship, forming the basis for generating the threaded helical trajectory.

[0010] In a preferred embodiment of the processing method for large helix angle internally threaded copper tubes according to the present invention, the helix angle is determined by the ratio between the spindle speed and the feed speed of the spinning ring, and the specific steps are as follows: Set the spindle speed to The corresponding number of revolutions per second of the tube blank is ; Set the axial feed speed of the spinning ring to be That is, the distance moved along the axis per unit time; Define thread lead The axial projection length of a single thread cycle satisfies the following relationship: ; helix angle Defined as the angle between the thread and the cross-section of the pipe, satisfying a trigonometric function relationship. ,in The thread pitch diameter; By adjusting and The ratio controls the size of L, thereby precisely regulating... The angle value.

[0011] As a preferred embodiment of the processing method for the large helix angle internally threaded copper tube of the present invention, the spinning process is a multi-pass local plastic deformation, and the specific steps are as follows: The feed stroke of the spinning ring is divided into multiple continuous micro-segments, each micro-segment corresponding to a local compression region; Within each micro-segment, the spinning ring applies instantaneous radial pressure to the tube blank, causing the material in the region to plastically yield and bulge inward; As the spinning ring moves forward, the next micro-segment continues to be compressed, while the previous region, having already formed a tooth shape, enters a stable state. The entire thread length is completed through several local compressions, with the deformation amount controlled within the material's elongation limit each time to avoid cracks or folding defects. All local deformation zones are continuously distributed along the axial direction, forming a complete, continuous and uninterrupted helical tooth structure.

[0012] In a preferred embodiment of the processing method for large helix angle internally threaded copper tubes according to the present invention, the sizing process is used to calibrate the outer diameter of the finished product and optimize the wall thickness distribution, and the specific steps are as follows: Remove the spun copper tube from the equipment and inspect its surface integrity. One end of the copper tube is introduced into the sizing die inlet, and the inner hole of the sizing die is a high-precision cylindrical cavity. The copper tube is passed through the sizing die hole by pulling or pushing, and the outer diameter is compressed to the target size under the constraint of the die wall. During compression, the outer wall material transmits stress inward, causing the bottom wall of the internal thread area to be further compacted; After demolding, the outer surface of the copper tube is smooth and the dimensional accuracy is improved.

[0013] As a preferred embodiment of the processing method for large helix angle internally threaded copper tubes according to the present invention, the sizing die is provided with an inlet cone angle and a working section, and the specific steps are as follows: A tapered transition zone is machined at the inlet end of the sizing die, with a tapered angle of _____. It is used to guide the copper tube smoothly into the die hole and reduce initial frictional resistance; The main body of the sizing die is a cylindrical working section, the length of which is... The inner diameter is ; set up The axial length is greater than the full thread lead to ensure that at least one full thread cycle is covered during the sizing process; When the copper tube passes through the working section, the outer wall is subjected to uniform radial constraint, while the internal thread structure does not collapse due to the core support. By controlling The dimensional accuracy enables precise control of the outer diameter.

[0014] In a preferred embodiment of the processing method for the large helix angle internally threaded copper tube of the present invention, the material response during the sizing process is used to improve the uniformity of the bottom wall thickness, and the specific steps are as follows: Under the compression action of the sizing die, the outer wall of the copper tube is subjected to uniform compressive stress; The stress is transmitted through the pipe wall to the valley area of ​​the internal thread, causing a small amount of plastic flow in the local material; Because there is a difference in wall thickness at the bottom of the thread, the stress concentration effect causes the thicker area to be compressed more, while the thinner area is relatively stable. After the overall drawing process, the wall thickness at each tooth valley tends to be consistent, and the deviation of the bottom wall thickness is reduced. After the material is demolded, it undergoes elastic recovery, forming a stable and uniform bottom wall structure, which improves its pressure resistance.

[0015] As a preferred embodiment of the processing method for the large helix angle internally threaded copper tube of the present invention, the finished product has an internal surface structure that enhances heat exchange capacity, and the specific steps are as follows: After the internal thread is formed, high-density helical teeth are formed on the inner wall of the copper tube, which are evenly distributed along the circumference. The side surface of each tooth forms a heat exchange extension surface, and its total surface area is composed of the inner surface area of ​​the tube plus the sum of the areas of all tooth sides and the valley bottom. When the refrigerant flows through the pipe, the spiral tooth structure breaks the fluid boundary layer, inducing circumferential eddies and secondary flows. The flow path extends in a spiral shape, prolonging the fluid residence time and enhancing heat exchange efficiency; The obtained copper tubes have a higher heat transfer coefficient for the same tube diameter.

[0016] The beneficial effects of this invention are as follows: Through the systematic process design of tube blank pretreatment, spinning forming and sizing finishing, high-precision and stable processing of large helix angle threads on the inner wall of small-diameter copper tubes is achieved. The use of a threaded mandrel and a walking mandrel cooperative support structure effectively prevents deformation and instability of thin-walled tubes during cold extrusion, ensuring the integrity of tooth profile replication and the uniformity of bottom wall thickness. By precisely matching the spindle rotation and the axial feed of the spinning ring, the helix angle is controlled by kinematic relationship, breaking through the limitations of traditional processes on thread lead. The multi-pass local plastic deformation mechanism avoids the risk of material cracking and improves the forming limit. The subsequent sizing process not only calibrates the outer diameter dimension, but also optimizes the inner wall structure through stress transfer, improving the dimensional accuracy and mechanical properties of the finished product. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0018] Figure 1 This is a flowchart of the processing method for the large helix angle internally threaded copper tube in Example 1.

[0019] Figure 2 This is a schematic diagram of the internal thread forming process in Example 1.

[0020] Figure 3 This is a schematic diagram of the internal thread forming principle in Example 1.

[0021] Figure 4 This is a schematic diagram of the internally threaded pipe structure in Example 1. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0025] Example, refer to Figures 1-4 This embodiment of the invention provides a method for processing a copper tube with a large helix angle internal thread, comprising the following steps: S1. Use round copper tubes as tube blanks; Furthermore, the tube blank undergoes surface cleaning and straightness correction. It should be noted that surface cleaning of the tube blank can remove grease, oxides and particulate impurities attached during the rolling process, avoiding scratches on the mold or local stress concentration during subsequent forming. Straightness correction is achieved by eliminating the original bending of the tube through multi-roll straightening or stretching, ensuring the stability of its axis during clamping and spinning, and preventing vibration, uneven wall thickness or tooth profile deviation caused by eccentric rotation, thus providing a geometric reference and material basis for subsequent high-precision thread forming.

[0026] S2. The processed tube blank is clamped in the spinning forming equipment, and its front end is fitted with the threaded mandrel, which is used for guiding and positioning with the moving mandrel. Furthermore, the running mandrel is positioned inside the tube blank and connects with the threaded mandrel head to support the inner wall of the tube blank and maintain coaxiality during the forming process. The specific steps are as follows: A hollow cylindrical core is selected, with a tapered inlet at the front end, a constant diameter support section in the middle, and a connection interface at the tail end that matches the threaded core head. While the tube blank is being fitted with the threaded mandrel, the pendant is inserted from the rear end of the tube blank so that its front end is mated with the tail end of the threaded mandrel. During the spinning process, the walking core moves synchronously with the tube blank, and its equal-diameter support section is always located upstream of the spinning deformation zone, providing radial support to the inner cavity of the tube blank that is about to enter the spinning zone. The support of the core prevents the tube blank from developing local depressions or uneven wall thickness under external pressure. It should be noted that the mating of the wick and the threaded core not only achieves axial positioning, but also forms a continuous internal support system, which effectively suppresses the buckling instability of thin-walled copper tubes under cold extrusion. The equal-diameter support section is located upstream of the deformation zone, and prestress is applied to the undeformed section in advance, so that the material is in a uniform stress state before entering the spinning zone, thereby improving the controllability of plastic flow and ensuring the continuity and dimensional consistency of the thread forming process.

[0027] S3. Start the spinning equipment and use the combined effect of rotational motion and axial feed to continuously cold extrude the tube blank through the external spinning ring, so that the tube blank forms an initial thread structure with a predetermined helix angle along the inner wall during the rotation process. Furthermore, the spinning equipment achieves thread forming through the combined motion of spindle rotation and axial feeding of the spinning ring. The specific steps are as follows: Start the spindle drive to make the tube blank move at a constant angular velocity. Rotates about its own axis; Simultaneously activate the feed mechanism to make the spinning ring move at a linear velocity. It is advanced along the axial direction of the tube blank and enters the gap between the tube blank and the outer mold; The inner surface of the spinning ring is a cylindrical working surface with a diameter slightly larger than the target outer diameter, applying radial pressure to the tube blank during the advancement process. ; Under pressure Under the action, the tube blank material is compressed and flows inward, adhering to the surface of the threaded mandrel to form the initial thread tooth shape; Rotational motion and axial feed are performed synchronously, and the two maintain a fixed motion relationship, forming the basis for generating the thread helical trajectory; The helix angle is determined by the ratio between the spindle speed and the feed speed of the spinning ring. The specific steps are as follows: Set the spindle speed to The corresponding number of revolutions per second of the tube blank is ; Set the axial feed speed of the spinning ring to be That is, the distance moved along the axis per unit time; Define thread lead The axial projection length of a single thread cycle satisfies the following relationship: ; helix angle Defined as the angle between the thread and the cross-section of the pipe, satisfying a trigonometric function relationship. ,in The thread pitch diameter; By adjusting and The ratio controls the size of L, thereby precisely regulating... Angle value; Spinning is a multi-pass localized plastic deformation process, and the specific steps are as follows: The feed stroke of the spinning ring is divided into multiple continuous micro-segments, each micro-segment corresponding to a local compression region; Within each micro-segment, the spinning ring applies instantaneous radial pressure to the tube blank, causing the material in the region to plastically yield and bulge inward; As the spinning ring moves forward, the next micro-segment continues to be compressed, while the previous region, having already formed a tooth shape, enters a stable state. The entire thread length is completed through several local compressions, with the deformation amount controlled within the material's elongation limit each time to avoid cracks or folding defects. All local deformation zones are continuously distributed along the axial direction, forming a complete, continuous and uninterrupted helical tooth structure; It should be noted that the synchronous control of the spindle rotation and the spinning ring feed is achieved through a servo linkage system, which ensures a constant ratio of motion parameters and is the key to forming a stable spiral trajectory. The multi-pass local deformation mechanism decomposes the total deformation into several small cumulative processes, reduces the stress peak of a single loading, avoids material cracking due to strain concentration, and at the same time facilitates heat dissipation, reduces the impact of temperature rise on microstructure and properties, and achieves high-quality cold forming.

[0028] S4. During cold extrusion forming, the threaded core and the floating core work together to maintain the inner cavity support and tooth profile transmission. Furthermore, the threaded mandrel is used to form the tooth profile of the internal thread during the spinning process. The specific steps are as follows: The outer surface of the threaded mandrel is designed to have a continuous helical groove structure, which includes a guide section, a forming section and a shaping section. Install the threaded mandrel at the front end of the spindle of the spinning equipment so that the axis is consistent with the direction of movement of the tube blank; During the clamping process, the front end of the tube blank is slid into the guide section to achieve initial positioning; After spinning begins, the tube blank rotates with the spindle, and the forming section of the threaded core contacts the inner wall of the tube blank. Through cold extrusion, the copper material undergoes plastic deformation along the groove, gradually replicating the corresponding tooth shape. At the end of the spinning process, the shaping section makes fine adjustments to the formed thread to eliminate dimensional deviations caused by material springback. It should be noted that the guide section, forming section and shaping section of the thread core are distributed sequentially along the axial direction, respectively undertaking the functions of guiding, main forming and finishing, forming a gradient forming path. The structural design allows the material to gradually adapt to the shape change, slowing down the sudden change in deformation resistance. At the same time, the shaping section performs slight cold work hardening on the formed teeth, improving the hardness and wear resistance of the tooth surface, and compensating for the dimensional springback caused by the elastic recovery of the material, ensuring the final thread profile accuracy.

[0029] S5. After spinning, the copper tube with internal threads is introduced into the sizing process, and the outer diameter of the tube is dimensionally adjusted by a precision sizing die. Furthermore, the sizing process is used to calibrate the outer diameter of the finished product and optimize the wall thickness distribution. The specific steps are as follows: Remove the spun copper tube from the equipment and inspect its surface integrity. One end of the copper tube is introduced into the sizing die inlet, and the inner hole of the sizing die is a high-precision cylindrical cavity. The copper tube is passed through the sizing die hole by pulling or pushing, and the outer diameter is compressed to the target size under the constraint of the die wall. During compression, the outer wall material transmits stress inward, causing the bottom wall of the internal thread area to be further compacted; After demolding, the outer surface of the copper tube is smooth and the dimensional accuracy is improved; It should be noted that the high-precision inner hole of the sizing die serves as the final control link for dimensions. It corrects the fluctuation of the outer diameter after spinning through a small amount of plastic deformation, thereby improving the roundness and surface finish of the product. The choice between drawing or pushing methods is determined based on the tube length and wall thickness conditions, ensuring processing efficiency and yield. At the same time, the process eliminates residual stress from the previous process, improves the uniformity of the structure, and provides good process adaptability for subsequent assembly processes such as tube bending and expansion.

[0030] S6. During the sizing process, the pipe wall thickness distribution is controlled synchronously to ensure that the bottom wall thickness is uniform and meets the structural strength requirements. Furthermore, the sizing die is equipped with an inlet cone angle and a working section. The specific steps are as follows: A tapered transition zone is machined at the inlet end of the sizing die, with a tapered angle of _____. It is used to guide the copper tube smoothly into the die hole and reduce initial frictional resistance; The main body of the sizing die is a cylindrical working section, the length of which is... The inner diameter is ; set up The axial length is greater than the full thread lead to ensure that at least one full thread cycle is covered during the sizing process; When the copper tube passes through the working section, the outer wall is subjected to uniform radial constraint, while the internal thread structure does not collapse due to the core support. By controlling The dimensional accuracy enables precise control of the outer diameter; The material response during the sizing process is used to improve the uniformity of the bottom wall thickness. The specific steps are as follows: Under the compression action of the sizing die, the outer wall of the copper tube is subjected to uniform compressive stress; Stress is transmitted through the pipe wall to the valley area of ​​the internal thread, causing a small amount of plastic flow in the local material; Because there is a difference in wall thickness at the bottom of the thread, the stress concentration effect causes the thicker area to be compressed more, while the thinner area is relatively stable. After the overall drawing process, the wall thickness at each tooth valley tends to be consistent, and the deviation of the bottom wall thickness is reduced. After the material is demolded, it undergoes elastic recovery, forming a stable and uniform bottom wall structure, which improves its pressure resistance. It should be noted that the working section of the sizing die covers at least one complete thread cycle, which can effectively constrain the deformation behavior of the entire thread cross section in the radial direction, prevent local crushing or tooth tip collapse, and reduce the initial bite resistance by introducing the cone angle design, thereby reducing die wear and extending die life. The stress redistribution mechanism caused by outer wall compression actively optimizes the consistency of bottom wall thickness, and a thin-walled high-strength structure that meets the strength requirements can be obtained without additional testing and adjustment.

[0031] S7. Obtain a finished copper tube with a large helix angle thread structure on the inner surface; Furthermore, the finished product possesses an internal surface structure that enhances heat exchange capacity. The specific steps are as follows: After the internal thread is formed, high-density helical teeth are formed on the inner wall of the copper tube, which are evenly distributed along the circumference. The side surface of each tooth forms a heat exchange extension surface, and its total surface area is composed of the inner surface area of ​​the tube plus the sum of the areas of all tooth sides and the valley bottom. When the refrigerant flows through the pipe, the spiral tooth structure breaks the fluid boundary layer, inducing circumferential eddies and secondary flows. The flow path extends in a spiral shape, prolonging the fluid residence time and enhancing heat exchange efficiency; The obtained copper tubes have a higher heat transfer coefficient for the same tube diameter; It should be noted that the high-density helical tooth structure significantly increases the inner surface area without increasing the outer diameter of the tube, strengthens the heat transfer boundary layer disturbance, reduces the critical Reynolds number at which the refrigerant flow state changes from laminar to turbulent, and improves the heat transfer coefficient. The structure also enhances fluid disturbance and wall shearing, inhibits fouling, and extends the equipment maintenance cycle, making it suitable for high-efficiency and energy-saving heat exchange systems under high heat flux density conditions.

[0032] In summary, this invention achieves high-precision and stable machining of large helix angle threads on the inner wall of small-diameter copper tubes through a systematic process design of tube blank pretreatment, spinning, and sizing finishing. The use of a threaded mandrel and a moving mandrel collaborative support structure effectively prevents deformation and instability of thin-walled tubes during cold extrusion, ensuring the integrity of the tooth profile replication and the uniformity of the bottom wall thickness. Precise matching of spindle rotation and axial feed of the spinning ring, utilizing kinematic relationships to control the helix angle, breaks through the limitations of traditional processes on thread lead. The multi-pass local plastic deformation mechanism avoids the risk of material cracking and improves the forming limit. The subsequent sizing process not only calibrates the outer diameter but also optimizes the inner wall structure through stress transfer, improving the dimensional accuracy and mechanical properties of the finished product.

[0033] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method of machining a large-pitch-angle internal thread brass pipe, characterized by: The application relates to a method for manufacturing a copper pipe with an inner thread structure. The method comprises the following steps: A round copper pipe is used as a pipe blank, the pipe blank is subjected to surface cleaning and straightness correction treatment; The treated pipe blank is clamped in a spinning forming device, and the front end of the pipe blank is sleeved into a threaded core head, and the core head is guided and positioned; The spinning device is started, the pipe blank is subjected to continuous cold extrusion by an external spinning ring through the cooperation of the rotating motion and the axial feeding, and the pipe blank is formed into an initial thread structure with a predetermined helix angle along the inner wall in the rotating process; The thread core head and the loose core jointly maintain the inner cavity support and the tooth profile transmission during the cold extrusion forming; After the spinning forming is completed, the copper pipe with the inner thread is introduced into a sizing process, and the outer diameter of the pipe body is subjected to size finishing through a precision sizing die; The wall thickness distribution of the pipe body is synchronously controlled during the sizing process, so that the bottom wall thickness is uniform and meets the structural strength requirement; 2. The method of processing a large pitch angle internal thread brass tube according to claim 1, wherein: A copper pipe product with a large helix angle thread structure on the inner surface is obtained. The thread core head is used for forming a tooth profile of the inner thread in the spinning process, and the specific steps are as follows: The outer surface of the thread core head is designed to have a continuous helical groove structure, and the helical groove comprises a guide section, a forming section and a shaping section; The thread core head is installed at the front end of the main shaft of the spinning device, so that the axis is consistent with the movement direction of the pipe blank; In the clamping process, the front end of the pipe blank is sleeved into the guide section to realize initial positioning; After the spinning starts, the pipe blank rotates with the main shaft, the forming section of the thread core head is in contact with the inner wall of the pipe blank, plastic deformation of the copper material occurs along the groove through cold extrusion, and the corresponding tooth shape is gradually copied out; 3. The method of processing large pitch angle internal thread copper tubes as claimed in claim 2, wherein: In the end stage of the spinning, the shaping section adjusts and corrects the formed thread, and eliminates the size deviation caused by material springback. The loose core is arranged inside the pipe blank and is in butt joint with the thread core head, and is used for supporting the inner wall of the pipe blank and maintaining the coaxiality in the forming process, and the specific steps are as follows: A hollow cylindrical loose core is selected, the front end of the loose core is provided with a tapered guide-in part, the middle part is an equal-diameter supporting section, and the tail part is provided with a connecting interface matched with the thread core head; When the pipe blank is sleeved into the thread core head, the loose core is inserted into the pipe blank from the rear end, so that the front end of the loose core is in butt joint with the tail part of the thread core head; In the spinning process, the loose core moves synchronously with the pipe blank, and the equal-diameter supporting section is always located at the upstream position of the spinning deformation zone, so that the inner cavity of the pipe blank entering the spinning zone is provided with radial support; 4. The method of producing a large-pitch angle internal thread brass pipe according to claim 3, wherein: Through the supporting action of the loose core, local concave or uneven wall thickness of the pipe blank under the action of external pressure is prevented. The spindle drive is activated so that the tube blank rotates at a constant angular velocity about its own axis; At the same time the feed mechanism is activated, causing the spinning ring to advance axially along the tube blank into the gap between the tube blank and the outer die. At the same time the feed mechanism is activated, causing the spinning ring to advance axially along the tube blank into the gap between the tube blank and the outer die. The inner surface of the spinning ring is a cylindrical working surface with a diameter slightly larger than the target outer diameter, which exerts a radial pressure on the tube blank during the advancement ; Under the action of pressure The pipe blank material is compressed and flows inward to fit the surface of the thread core head to form an initial thread profile. The spinning device realizes thread forming through the combined motion of the main shaft rotation and the axial feeding of the spinning ring, and the specific steps are as follows:

5. The method of producing a large-pitch angle internal thread brass pipe according to claim 4, wherein: The rotating motion and the axial feeding are synchronously performed, and the two maintain a fixed motion relationship, and constitute the basis for generating the thread helical trajectory. The main shaft rotation speed is set as The corresponding pipe blank rotation per second is ; The axial feed speed of the spinning ring is set as i.e. the distance moved along the axis in unit time; Defining thread lead is the axial projection of a single thread period, satisfying the relation ; helix angle defined as the angle between the thread line and the pipe cross section, which satisfies the trigonometric function relationship wherein is the pitch diameter of the thread; By adjusting the ratio of , the size of L is controlled, and the angle value of is accurately regulated.

6. The method of producing a large-pitch angle internal thread brass pipe according to claim 5, wherein: The helix angle is determined by the proportional relationship between the main shaft rotating speed and the feeding speed of the spinning ring, and the specific steps are as follows: The spinning process is a multi-pass local plastic deformation, and the specific steps are as follows: The feeding stroke of the spinning ring is divided into a plurality of continuous micro segments, and each micro segment corresponds to a local compression area; In each micro segment, the spinning ring applies instantaneous radial pressure to the pipe blank, so that the regional material is plastically yielded and bulges inward; With the forward movement of the spinning ring, the next micro segment continues to be pressed, and the formed tooth shape of the previous region enters a stable state; The entire thread length is completed by several times of local compression, and the deformation amount is controlled within the material ductility limit range to avoid crack or folding defects; All local deformation zones are continuously distributed along the axial direction to form a complete, continuous and uninterrupted spiral tooth structure.

7. The method of producing a large-pitch angle internal thread brass pipe according to claim 6, wherein: The sizing process is used to calibrate the outer diameter of the finished product and optimize the wall thickness distribution, and the specific steps are as follows: The copper pipe that has completed the spinning forming is unloaded from the equipment, and the surface integrity is checked; One end of the copper pipe is introduced into the sizing die inlet, and the sizing die inner hole is a high-precision cylindrical cavity; The copper pipe is made to pass through the sizing die hole by drawing or pushing, and the outer diameter is compressed to the target size under the constraint of the die wall; During the compression process, the outer wall material transmits stress inward, which promotes the further compaction of the bottom wall of the internal thread area; After the copper pipe is discharged from the die, the outer surface is smooth, and the size accuracy is improved.

8. The method of producing a large-pitch angle internal thread brass pipe according to claim 7, wherein: The sizing die is provided with a lead-in cone angle and a working section, and the specific steps are as follows: A taper transition section with a taper angle of is formed at the entrance end of the sizing die to guide the copper tube smoothly into the die hole and reduce the initial frictional resistance. The main body of the sizing die is a cylindrical working section having a length of and an inner diameter of ; Setting an axial length greater than the full thread pitch to ensure that at least one full thread period is covered during sizing; When the copper pipe passes through the working section, the outer wall is uniformly constrained in the radial direction, and the internal thread structure does not collapse due to the support of the core; By controlling the dimensional accuracy, precise control of the outer diameter is achieved.

9. The method of producing a large-pitch angle internal thread brass pipe according to claim 8, wherein: The material response in the sizing process is used to improve the uniformity of the bottom wall thickness, and the specific steps are as follows: Under the compression action of the sizing die, the outer wall of the copper pipe bears uniform compressive stress; The stress is conducted to the bottom area of the internal thread valley through the pipe wall, which promotes the plastic flow of the local material; Due to the thickness difference of the thread valley bottom, the stress concentration effect makes the thicker area produce more compression, and the thinner area is relatively stable; After overall drawing, the wall thickness of each tooth valley tends to be uniform, and the thickness deviation of the bottom wall is reduced; After the material is discharged from the die, it undergoes elastic recovery to form a stable and uniform bottom wall structure, which improves the pressure resistance performance.

10. The method of producing a large-pitch-angle internal thread brass tube according to claim 9, wherein: The finished product has an internal surface structure that enhances the heat exchange capacity, and the specific steps are as follows: After the internal thread is formed, the copper pipe inner wall forms a high-density spiral tooth that is uniformly distributed along the circumference; The side surface of each tooth constitutes a heat exchange expansion surface, and its total surface area is composed of the inner surface area of the light pipe and the sum of the areas of all tooth side surfaces and valley bottoms; When the refrigerant flows through the pipe, the spiral tooth structure breaks the fluid boundary layer and induces circumferential vortex and secondary flow; The flow path extends in a spiral shape, prolonging the fluid residence time and enhancing the heat exchange efficiency; The obtained copper pipe has a higher heat transfer coefficient under the same pipe diameter.

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