A method of processing a copper or copper alloy heat transfer tube and a processing assembly for a copper or copper alloy heat transfer tube

Abstract

The application discloses a processing method of a copper or copper alloy heat transfer pipe and a processing assembly for the copper or copper alloy heat transfer pipe, and the processing method is innovatively processed by using the processing assembly which is constructed by a drawing die seat provided with a through hole, a core rod and a multi-roller rolling assembly, copper or copper alloy pipe blanks are sequentially subjected to reducing diameter and wall thickness treatment by using the organic cooperation between the components, the two serial combined drawing processes in the prior art can be replaced, and due to the fact that the processing method can achieve a large single deformation and an ideal deformation degree at one time, the drawing passes of a subsequent disc drawing machine can be reduced, the load of the disc drawing machine is reduced, the production cycle is shortened, and due to the fact that the disc drawing machine needs to be subjected to operations such as head shearing and head punching each time when disc drawing is performed, part of copper or copper alloy materials is wasted, and time and labor are consumed, and the processing method can reduce the disc drawing times, correspondingly reduces the waste of the copper or copper alloy materials, and the production efficiency is also improved.

Description

Technical Field

[0001] This invention relates to the field of copper or copper alloy heat transfer tube processing technology, and particularly to small-sized copper or copper alloy heat transfer tubes, such as air conditioning heat transfer tubes. Specifically, it relates to a processing method for copper or copper alloy heat transfer tubes and processing components for copper or copper alloy heat transfer tubes. Background Technology

[0002] The current processing method for copper and copper alloy heat transfer tubes generally adopts the following process: horizontal continuous casting of hollow round billets, rolling into disc-shaped copper or copper alloy tube billets using a three-roll planetary mill, drawing into disc-shaped semi-finished products using a two-series combined drawing machine (two-series combined drawing process), multi-pass drawing to the finished product specification using a coil drawing machine (intermediate annealing is performed depending on the degree of work hardening), rewinding, and finished product annealing, etc., which is referred to as the casting and rolling method. Among them, the specifications of the hollow round billets and planetary rolled tube billets are basically fixed and belong to the billets for subsequent copper tube processing. The number of drawing passes depends on the size of the finished product specification. Since metal materials have work hardening characteristics during cold working, the initial drawing passes usually have a larger processing rate. As the metal's deformation resistance increases and its plasticity decreases, the processing rate should decrease accordingly. Therefore, the smaller the tube specification to be produced, the more drawing passes are required. If the metal hardens to the point that it cannot be drawn further, intermediate annealing must be performed before drawing can continue. Currently, this process and production equipment have matured and are basically solidified.

[0003] However, due to the need for energy and material conservation, the specifications of copper and copper alloy heat transfer tubes used in air conditioning and refrigeration are trending towards smaller diameters and thinner walls. Due to the process characteristics of the aforementioned casting and rolling method, the smaller the specification of the copper tube, the more passes the drawing machine needs to run, resulting in a heavier load, longer processing time, and higher energy consumption. Repeated drawing also requires repeated cutting, heading, and handling of the tubes (only after cutting and heading can they meet the conditions for entering the equipment; otherwise, irregular or missized heads cannot enter the equipment for further drawing), which not only reduces production efficiency but also lowers the yield. Summary of the Invention

[0004] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide an improved processing method for copper or copper alloy heat transfer tubes. This processing method can achieve the processing of small-sized copper or copper alloy heat transfer tubes with fewer deformation passes, and can improve the metal microstructure and properties, reduce the number of times the tube is repeatedly cut or headed, reduce metal consumption, increase production speed, and significantly shorten processing time.

[0005] The present invention also provides a processing assembly for copper or copper alloy heat transfer tubes.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a processing method for copper or copper alloy heat transfer tubes, comprising the following steps: horizontal continuous casting of hollow round ingots, rolling into disc-shaped copper or copper alloy tube blanks using a three-roll planetary rolling mill, drawing into disc-shaped semi-finished products using a two-series combined drawing machine, drawing to the finished product specification using a multi-pass drawing machine, rewinding, and annealing the finished product. Specifically, in this processing method, the step of drawing into disc-shaped semi-finished products using a two-series combined drawing machine is replaced with a longitudinal rolling step; wherein the longitudinal rolling step includes:

[0007] The copper or copper alloy tube blanks rolled by a three-roll planetary mill are used as incoming materials for processing. After being processed by straightening pinch rolls, copper or copper alloy tube blanks with linear extension are obtained.

[0008] A linearly extending copper or copper alloy tube blank is fed into a drawing die with a through hole and fitted onto a mandrel. The mandrel is movably disposed in the through hole along its own extension direction and extends outward from the outlet side of the through hole. The diameter of the through hole varies at various points along the extension direction of the mandrel, such that the diameter near the outlet side of the through hole is less than or equal to (less than or equal to) the diameter near the inlet side of the through hole. This variation also allows the through hole to restrict the mandrel from disengaging from the outlet side of the through hole. The radial dimension of the copper or copper alloy tube blank is reduced by the pressing fit between the through hole and the mandrel.

[0009] The copper or copper alloy tube blank with a reduced radial dimension is moved along the mandrel into a multi-roll mill assembly, the multi-roll mill assembly including at least three rolls uniformly surrounding the outer periphery of the mandrel, and the wall thickness of the copper or copper alloy tube blank is reduced by the spinning engagement of the multi-roll mill assembly and the mandrel;

[0010] The rotation axis of the roll is perpendicular to the straight line of the extension direction of the core rod. During the rotation of the roll, the frictional force generated between the roll and the tube blank can drive the copper or copper alloy tube blank to move away from the drawing die.

[0011] The plane containing the center of the at least three rolls is parallel to the radial plane of the mandrel, and the surfaces of the at least three rolls that contact the copper or copper alloy tube blank are joined together at the same position in the axial direction of the copper or copper alloy tube blank to form a complete circle.

[0012] Another technical solution provided by the present invention: a method for processing a copper or copper alloy heat transfer tube, the method comprising:

[0013] A linearly extending copper or copper alloy tube blank is fed into a drawing die with a through hole and fitted onto a mandrel. The mandrel is movably disposed in the through hole along its own extension direction and extends outward from the outlet side of the through hole. The diameter of the through hole varies at various points along the extension direction of the mandrel, such that the diameter near the outlet side of the through hole is less than or equal to the diameter near the inlet side of the through hole. This variation also allows the through hole to restrict the mandrel from disengaging from the outlet side of the through hole. The radial dimension of the copper or copper alloy tube blank is reduced by the compression fit between the through hole and the mandrel.

[0014] The copper or copper alloy tube blank with a reduced radial dimension is moved along the mandrel into a multi-roll mill assembly, the multi-roll mill assembly including at least three rolls uniformly surrounding the outer periphery of the mandrel, and the wall thickness of the copper or copper alloy tube blank is reduced by the spinning engagement of the multi-roll mill assembly and the mandrel.

[0015] According to the present invention, the present invention can process coiled tubes as incoming materials, specifically, it can process disc-shaped copper or copper alloy tube blanks rolled by a three-roll planetary mill as incoming materials. According to some preferred and specific aspects of the present invention, the processing method further includes: processing the disc-shaped copper or copper alloy tube blanks rolled by a three-roll planetary mill as incoming materials, and treating them with straightening pinch rolls to obtain the linearly elongated copper or copper alloy tube blanks.

[0016] According to the present invention, during the processing of copper or copper alloy heat transfer tubes, the core rod remains relatively fixed under the combined action of the inner wall of the through hole and the copper or copper alloy tube blank. Specifically, the force applied to the core rod by the inner wall of the through hole, after decomposition, has the effect of moving the core rod towards the inlet side of the through hole, while the frictional force between the copper or copper alloy tube blank and the core rod during movement can drive the core rod towards the outlet side of the through hole. The forces of the two are balanced in the axial direction of the core rod, thus keeping the core rod relatively fixed during the processing.

[0017] According to some preferred and specific aspects of the invention, the through hole includes a clearance sub-hole and a limiting sub-hole connected in sequence, the diameter of the clearance sub-hole being greater than or equal to the diameter of the limiting sub-hole, and a copper or copper alloy tube blank entering from the clearance sub-hole and extending from the limiting sub-hole.

[0018] Furthermore, the radial dimension reduction factor of the copper or copper alloy tube blank can be adjusted by controlling the distance between the inner wall of the limiting sub-hole and the outer wall of the core rod.

[0019] Furthermore, the distance between any point on the inner wall of the limiting sub-hole and the outer wall of the core rod is the same.

[0020] In this invention, "spacing" refers to the vertical distance between any point on the inner wall of the limiting sub-hole and the outer wall of the core rod.

[0021] Furthermore, the inner wall of the limiting sub-hole includes an inclined surface and a horizontal surface, and its diameter first gradually decreases and then remains unchanged after the decrease.

[0022] According to some preferred and specific aspects of the present invention, the clearance sub-hole and the limiting sub-hole are integrally formed to constitute the through hole.

[0023] According to some preferred and specific aspects of the invention, the rod segment of the core rod located in the relief sub-hole has a portion larger than the diameter of the limiting sub-hole.

[0024] According to some preferred and specific aspects of the invention, the radial dimensions of the rod segment located outside the through hole are the same at all points.

[0025] According to some preferred and specific aspects of the invention, the outer surface of the portion of the mandrel that mates with the multi-roll mill assembly is a smooth surface.

[0026] According to some preferred and specific aspects of the invention, the rotational rolling direction of the rolls is controlled so that the frictional force generated between the rolls and the copper or copper alloy tube blank can drive the copper or copper alloy tube blank in a direction away from the drawing die.

[0027] According to some preferred aspects of the invention, the plane containing the centers of the at least three rolls is parallel to the radial plane of the mandrel.

[0028] According to some preferred aspects of the invention, the multi-roll mill assembly has at least two rolls, each roll acting on a copper or copper alloy tube blank from different directions.

[0029] According to the present invention, the cross-sectional shape of the part where the roll and the mandrel interact is circular or non-circular, and the non-circular shape includes triangle, hexagon or rectangle.

[0030] According to some specific aspects of the present invention, the maximum rolling speed of the copper or copper alloy tube blank is not less than 3 m / s.

[0031] According to some preferred and specific aspects of the invention, the processing method further includes: winding the copper or copper alloy tube blank, after the wall thickness reduction treatment by the multi-roll mill assembly, into a material frame, and then into a coil drawing machine for processing.

[0032] Another technical solution provided by the present invention: a processing assembly for copper or copper alloy heat transfer tubes, the processing assembly comprising: a drawing die base with through holes, a mandrel, and a multi-roll mill assembly;

[0033] The core rod is movably disposed in the through hole along its own extension direction and extends outward from the outlet side of the through hole; the diameter of the through hole varies at various points along the extension direction of the core rod, such that the diameter at various points near the outlet side of the through hole is less than or equal to the diameter at various points near the inlet side of the through hole, and such variation allows the through hole to restrict the core rod from disengaging from the outlet side of the through hole.

[0034] The multi-roll mill assembly includes at least three rolls, which are uniformly arranged around the outer periphery of the mandrel;

[0035] The rotation axis of the roll is perpendicular to the straight line extending from the core rod. The plane containing the center of the at least three rolls is parallel to the radial plane of the core rod. The surfaces of the at least three rolls that contact the copper or copper alloy tube blank are joined together to form a complete circle at the same position in the axial direction of the copper or copper alloy tube blank.

[0036] Another technical solution provided by the present invention: a processing assembly for copper or copper alloy heat transfer tubes, the processing assembly comprising: a drawing die base with through holes, a mandrel, and a multi-roll mill assembly;

[0037] The core rod is movably disposed in the through hole along its own extension direction and extends outward from the outlet side of the through hole; the diameter of the through hole varies at various points along the extension direction of the core rod, such that the diameter at various points near the outlet side of the through hole is less than or equal to the diameter at various points near the inlet side of the through hole, and such variation allows the through hole to restrict the core rod from disengaging from the outlet side of the through hole.

[0038] The multi-roll mill assembly includes at least three rolls that are uniformly arranged around the outer periphery of the mandrel.

[0039] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0040] This invention addresses the problems existing in the production of small-diameter copper or copper alloy tubes using existing casting and rolling processes. It innovatively employs an organic combination of a drawing die base with through holes, a mandrel, and a multi-roll mill assembly. This allows the copper or copper alloy tube blank to undergo sequential diameter and wall reduction processes, replacing the existing two-stage combined drawing process. Furthermore, because this method allows for a large single-stage deformation, achieving the desired deformation degree in one pass, it reduces the number of subsequent drawing passes on the coiling machine, lessening its load and shortening the production cycle. Additionally, since each coiling operation requires shearing and heading, wasting metal material and being time-consuming and labor-intensive, this invention reduces the number of coiling passes, thus decreasing copper or copper alloy material waste and improving production efficiency.

[0041] Through further experimental analysis, the inventors believe that the reason why existing combined drawing processes struggle to achieve large deformation and high-performance processing is due to the limitations of the combined drawing equipment structure (during the drawing process, clamps are used to hold the copper or copper alloy tube blank and move it forward. If the deformation is too large, the clamping force on the copper or copper alloy tube blank must be increased to prevent slippage, which inevitably damages the copper or copper alloy tube blank). Furthermore, if the deformation is too large during a single drawing process, the copper or copper alloy tube blank is prone to breakage, especially since drawing cannot be performed quickly; excessive speed also easily leads to breakage. This invention creatively uses a movable mandrel, which engages with the drawing die and the multi-roll mill assembly. By utilizing the specific through-holes in the mandrel and the drawing die, the diameter of the tube blank is reduced. Without wall reduction, the process can be quick and easy. After diameter reduction, the tube directly enters the multi-roll mill assembly along the mandrel for longitudinal spinning (the rotation axis of the roll is perpendicular to the straight line extending from the mandrel) wall reduction. Since the rolls act directly on the outer circumference of the copper or copper alloy tube blank, the size of the rolls can be relatively small, allowing them to be placed closer to the drawing die. This significantly reduces the space occupied by the production equipment compared to a two-tank combined drawing machine. At the same time, the multi-roll mill assembly includes at least three rolls, and the copper or copper alloy tube blank is under triaxial compressive stress, resulting in more balanced stress at various locations, more uniform deformation, less work hardening, and greatly improved metal microstructure. The total processing rate of a single continuous rolling can reach 80%, which can reduce the number of drawing passes of at least two subsequent coil drawing machines. Attached Figure Description

[0042] 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.

[0043] Figure 1 This is a schematic diagram of the process system used in the processing method of copper or copper alloy heat transfer tubes in the embodiments of the present invention;

[0044] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0045] Figure 3 This is a schematic diagram of the processing assembly for copper or copper alloy heat transfer tubes in an embodiment of the present invention;

[0046] Figure 4 for Figure 3 Enlarged view of point B in the middle;

[0047] Figure 5 for Figure 4 A schematic diagram with some components omitted;

[0048] In the attached figures, 1 is the receiving mechanism of a planetary mill; 2 is the straightening and pinching roll assembly; 3 is the drawing die base; 31 is the through hole; 311 is the clearance sub-hole; 312 is the limiting sub-hole; 313 is the outlet; 314 is the inlet; 4 is the mandrel; 5 is the multi-roll mill assembly; 51 is the roll; 6 is the material frame; and 7 is a linearly extending copper or copper alloy tube blank. Detailed Implementation

[0049] This invention employs a single-pass, large-deformation longitudinal rolling technology (where the rotation axis of the rolls is perpendicular to the extension direction of the mandrel). Specifically, this is achieved through the interaction between the mandrel and a drawing die base with through holes, and a multi-roll mill assembly. The uniquely designed mandrel passes between the through holes of the drawing die base and multiple rolls of the multi-roll mill assembly, separating diameter reduction and wall reduction. Utilizing the force exerted by the rolls on the copper or copper alloy tube blank—specifically, friction—reduces the axial movement of the copper or copper alloy tube blank during diameter or wall reduction, significantly reducing the need for external forces and power load. Furthermore, the drawing die base with through holes and the multi-roll mill assembly used in this invention do not require a large space, greatly reducing the size of the production workshop and lowering production costs. In particular, the innovative multi-roll mill assembly, comprising at least three rolls, when interacting with the mandrel for wall reduction, places the copper or copper alloy tube blank under triaxial compressive stress, resulting in a more efficient and effective reduction of the copper or copper alloy tube blank. The stress on each part of the tube blank is more balanced and greater, the deformation of the copper or copper alloy tube blank is more uniform, and the work hardening is less. This not only greatly improves the metal's microstructure and properties, but also greatly releases the amount of deformation per cycle. The copper or copper alloy tube blank undergoes spinning and wall reduction under controlled conditions, which basically does not affect the moving speed of the copper or copper alloy tube blank, and can also assist the movement of the copper or copper alloy tube blank. This greatly improves production efficiency and prevents the copper or copper alloy tube blank from breaking. As a result, the above process can replace the existing two-series combined drawing process. Furthermore, because the method of this invention can achieve a large amount of deformation per cycle and achieve the ideal deformation degree in one go, it can reduce the number of drawing passes of the subsequent coiling machine, reduce the load on the coiling machine, and shorten the production cycle. At the same time, since the coiling machine needs to perform cutting and heading operations every time it coils, some metal materials are wasted and it is time-consuming and labor-intensive. This invention can reduce the number of coiling passes, thereby reducing the waste of copper or copper alloy materials and improving production efficiency.

[0050] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0051] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0052] The existing processing flow for copper or copper alloy heat transfer tubes is basically as follows: horizontal continuous casting of hollow round billets, rolling into disc-shaped copper or copper alloy tube billets using a three-roll planetary mill, drawing into disc-shaped semi-finished products using a two-series combined drawing machine (two-series combined drawing process), multi-pass drawing to the finished product specification using a coil drawing machine (intermediate annealing is performed depending on the degree of work hardening), rewinding, and finished product annealing, etc., which is referred to as the casting and rolling method. Among them, the specifications of the hollow round billets and planetary rolled tube billets are basically fixed and belong to the billets for subsequent copper tube processing. The number of drawing passes depends on the size of the finished product specification. Since metal materials have work hardening characteristics during cold working, the initial drawing passes usually have a larger processing rate. As the metal's deformation resistance increases and its plasticity decreases, the processing rate should decrease accordingly. Therefore, the smaller the tube specification to be produced, the more drawing passes are required. If the metal hardens to the point that it cannot be drawn further, intermediate annealing must be performed before drawing can continue. Currently, this process and production equipment have matured and are basically solidified.

[0053] However, due to the need for energy and material conservation, the specifications of copper and copper alloy heat transfer tubes used in air conditioning and refrigeration are trending towards smaller diameters and thinner walls. Due to the process characteristics of the aforementioned casting and rolling method, the smaller the specification of the copper tube, the more passes the drawing machine needs to run, resulting in a heavier load, longer processing time, and higher energy consumption. Repeated drawing also requires repeated cutting, heading, and handling of the tubes (only after cutting and heading can they meet the conditions for entering the equipment; otherwise, irregular or missized heads cannot enter the equipment for further drawing), which not only reduces production efficiency but also lowers the yield.

[0054] Copper or copper alloys differ from other materials; processing methods suitable for other materials may not be applicable to the processing of copper or copper alloy tubes. Based on the characteristics of copper or copper alloys, this invention proposes the following improved process:

[0055] This example provides an improved processing method for copper or copper alloy heat transfer tubes. This method replaces the existing step of "drawing into a disc-shaped semi-finished product using a two-series combined drawing machine (two-series combined drawing process)" with a "special processing step, namely a longitudinal rolling process." In this example, copper or copper alloy coils are used as the raw material. Specifically, disc-shaped copper or copper alloy tube blanks rolled by a three-roll planetary mill are used as the raw material. After being processed by straightening and pinching rollers, linearly elongated copper or copper alloy tube blanks are obtained, ready for processing in this example's special processing step. The straightening and pinching rollers not only straighten the bent disc-shaped copper or copper alloy tube blanks but also move them. Furthermore, this processing method includes winding the tube blanks, after undergoing a special diameter and wall reduction process, into a material frame, and then into a coil drawing machine for further processing.

[0056] The following is combined Figures 1 to 5 The process apparatus, processing components, and partial structures shown further illustrate the processing method of the copper or copper alloy heat transfer tube in this example, especially the "special processing procedure, namely the longitudinal rolling process," to facilitate understanding.

[0057] See Figures 1 to 5 As shown, the disc-shaped copper or copper alloy tube blank rolled by the three-roll planetary mill is received by the planetary mill receiving mechanism 1 and then conveyed to the straightening pinch roll assembly 2 for straightening treatment, so that the disc-shaped copper or copper alloy tube blank is transformed into a linearly extended copper or copper alloy tube blank 7, that is, a straight tube blank. Then it enters the drawing die base 3 with a through hole 31 and is sleeved on the mandrel 4. The mandrel 4 is movably set in the through hole 31 along its own extension direction and extends outward from the outlet 313 side of the through hole 31. In specific installation, the mandrel 4 is inserted from the inlet 314 side of the through hole 31 and then partially extends outward from the outlet 313 side of the through hole 31.

[0058] The diameter of the through hole 31 varies along the extension direction of the core rod 4. This variation makes the diameter of the through hole 31 on the side near the outlet 313 of the through hole 31 smaller than or equal to the diameter of the through hole 31 on the side near the inlet 314 of the through hole 31. This variation also allows the through hole 31 to restrict the core rod 4 from disengaging from the outlet side of the through hole 31. The radial dimension of the copper or copper alloy tube blank is reduced by the extrusion fit between the through hole 31 and the core rod 4.

[0059] The copper or copper alloy tube blank with a reduced radial dimension is moved along the mandrel 4 into the multi-roll mill assembly 5, which includes at least three rolls 51 that are uniformly surrounded around the outer periphery of the mandrel 4. The wall thickness of the copper or copper alloy tube blank is reduced by the spinning fit between the multi-roll mill assembly 5 and the mandrel 4.

[0060] The rotation axis of the roll 51 is perpendicular to the straight line extending from the core rod 4. During the rotation of the roll 51, the friction between the roll 51 and the copper or copper alloy tube blank can drive the copper or copper alloy tube blank to move away from the drawing die 3. The plane containing the center of the aforementioned at least three rolls 51 is parallel to the radial plane of the core rod 4, and the contact surfaces of the at least three rolls 51 with the copper or copper alloy tube blank are joined together at the same position in the axial direction of the copper or copper alloy tube blank to form a complete circle. This makes the force on each position of the copper or copper alloy tube blank more balanced and greater, the deformation of the copper or copper alloy tube blank more uniform, and the work hardening less. This not only greatly improves the metal structure properties, but also greatly releases the amount of deformation per cycle. The copper or copper alloy tube blank undergoes spinning and wall reduction under controlled conditions, which basically does not affect the moving speed of the copper or copper alloy tube blank, and can also assist the movement of the copper or copper alloy tube blank. This greatly improves the production efficiency and prevents the copper or copper alloy tube blank from breaking.

[0061] As an optional implementation, in this example, the specifications of the disc-shaped copper or copper alloy tube blank rolled by the three-roll planetary mill are: outer diameter Ф45~100 and wall thickness 2~5mm.

[0062] As an optional implementation, in this example, the through hole 31 includes a clearance sub-hole 311 and a limiting sub-hole 312 connected in sequence. The diameter of the clearance sub-hole 311 is greater than or equal to the diameter of the limiting sub-hole 312. The tube blank enters through the clearance sub-hole 311 and extends out through the limiting sub-hole 312. In actual operation, one of the purposes of the clearance sub-hole 311 is to allow the copper or copper alloy tube blank, which has not yet undergone diameter reduction, to enter the drawing die 3 without obstruction. Then it can be fitted onto the mandrel 4. Since the copper or copper alloy tube blank moves continuously, after diameter reduction in the drawing die 3, it will extend out through the limiting sub-hole 312 and continue to move to the next processing point, namely the multi-roll mill assembly 5, for wall reduction. One of the purposes of the limiting sub-hole 312 is to provide a smaller space so that it can cooperate with the mandrel 4 during the movement of the copper or copper alloy tube blank. To achieve the diameter reduction of copper or copper alloy tube blanks, especially in this example where the mandrel 4 extends outward from the limiting sub-hole 312, the copper or copper alloy tube blank must always be able to abut or adhere to the mandrel 4 during the diameter reduction process, or even immediately after diameter reduction and removal from the limiting sub-hole 312. This prevents the reduced-diameter copper or copper alloy tube blank from immediately losing external support and undergoing unexpected deformation. Simultaneously, by controlling the distance between the inner wall of the limiting sub-hole 312 and the outer wall of the mandrel 4, the radial dimension reduction factor of the copper or copper alloy tube blank can be adjusted. This factor is adjusted according to actual needs. Furthermore, ensuring that the distance between any point on the inner wall of the limiting sub-hole 312 and the outer wall of the mandrel 4 is the same is more conducive to obtaining the desired radial dimension. If only a few points are reduced in diameter, the diameter reduction may not meet expectations. In this example, "distance" refers to the vertical distance between any point on the inner wall of the limiting sub-hole 312 and the outer wall of the mandrel 4.

[0063] Furthermore, as an optional implementation, the positioning sub-hole 311 and the limiting sub-hole 312 are integrally formed to form a through hole 31.

[0064] In this example, as Figures 2 to 4 As shown, the section of the core rod 4 located in the relief sub-hole 311 has a portion larger than the diameter of the limiting sub-hole 312. This prevents the core rod 4 from disengaging from the limiting sub-hole 312 and also allows the larger portion of the core rod 4 to support and guide the movement of the copper or copper alloy tube blank.

[0065] like Figures 2 to 4As shown, in this example, the radial dimensions of the mandrel 4 located outside the through hole 31 are the same at all points. This arrangement can further ensure that the wall reduction process is well achieved in the multi-roll mill assembly 5 and obtain a stable and uniform wall reduction effect; the outer surface of the part of the mandrel 4 that mates with the multi-roll mill assembly 5 is a smooth surface.

[0066] In this example, the rotational rolling direction of the rolls 51 is controlled so that the frictional force generated between the rolls 51 and the copper or copper alloy tube blank can drive the copper or copper alloy tube blank away from the drawing die 3. Specifically, the rolls 51 adopt longitudinal rolling, which cooperates with the mandrel 4 to achieve wall reduction. Furthermore, the plane containing the center of the aforementioned at least three rolls 51 is parallel to the radial plane of the mandrel 4, which can better ensure that the copper or copper alloy tube blank is subjected to uniform and balanced force during rolling, thereby effectively improving the metal microstructure. Figures 1 to 2 As shown, in this example, the multi-roll mill assembly 5 includes three rolls 51 with an included angle of 120° between them. The surfaces of the three rolls 51 that contact the copper or copper alloy tube blank are joined together to form a complete circle at the same position in the axial direction of the copper or copper alloy tube blank, so that the copper or copper alloy tube blank is subjected to triaxial compressive stress, resulting in uniform deformation of the rolled piece, small work hardening, and large deformation per pass.

[0067] Furthermore, in this example, the multi-roll mill assembly 5 has at least two rolls 51, each acting on the copper or copper alloy tube blank from different directions. This allows the copper or copper alloy tube blank to receive more uniform force in more directions, further improving the metal microstructure and achieving a uniform and balanced wall reduction effect. Figures 1 to 2 As shown, the multi-roll mill assembly 5 in this example has two components, and the two multi-roll mill assemblies 5 can be spaced very close together. At the same time, since the diameter reduction and wall reduction processing assembly in this example only requires the drawing die 3, the mandrel 4 and the roll 51 to be located in the operating system, and the components do not need to be spaced far apart as in the prior art of two-stage joint drawing, the production space is greatly reduced, which helps to save costs.

[0068] In essence, this invention innovatively combines the mandrel 4 with the multi-roll mill assembly 5. On the one hand, the mandrel 4 has a guiding function, ensuring that the copper or copper alloy tube blank always moves along a specific direction during the wall reduction process of the multi-roll mill assembly 5, without deviation. This is especially important during the initial processing and guidance into the multi-roll mill assembly 5, reducing manual positioning operations. On the other hand, the mandrel 4 can also act as an internal support for the copper or copper alloy heat transfer tube, ensuring that no unexpected diameter reduction occurs during the wall reduction process, and reducing the possibility of unexpected deformation of the copper or copper alloy tube blank.

[0069] In this example, the processing assembly that reduces the diameter and wall thickness of copper or copper alloy tube blanks can continuously perform the reduction process during the continuous movement of the copper or copper alloy tube blanks, thereby ensuring that the maximum rolling speed of the copper or copper alloy tube blanks is not less than 3m / s, which greatly improves production efficiency.

[0070] As an optional implementation, the cross-sectional shape of the part where the roll 51 and the core rod 4 interact is circular or non-circular, including triangular, hexagonal or rectangular shapes, while the cross-sectional shape of the through hole 31 can be circular, which can realize the preparation of irregular copper or copper alloy heat transfer tubes.

[0071] In summary, this method not only solves the drawbacks of using two-stage combined drawing in the processing of small-sized copper or copper alloy heat transfer tubes in the existing technology, but also effectively improves the metal microstructure and properties. It can also roll irregularly shaped tubes, greatly increasing the production speed. It is applicable to the processing of copper or copper alloy heat transfer tubes, such as those used in air conditioning and refrigeration.

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0073] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for processing a copper or copper alloy heat transfer tube, comprising the following steps: horizontal continuous casting of hollow round ingots, rolling into disc-shaped copper or copper alloy tube blanks using a three-roll planetary rolling mill, drawing into disc-shaped semi-finished products using a two-series combined drawing machine, drawing to the finished product specification using a multi-pass drawing machine, rewinding, and annealing the finished product, characterized in that, The processing method further includes replacing the process of drawing the two-stage combined drawing machine into a disc-shaped semi-finished product with a longitudinal rolling process; wherein, the longitudinal rolling process includes: The copper or copper alloy tube blanks rolled by a three-roll planetary mill are used as incoming materials for processing. After being processed by straightening pinch rolls, copper or copper alloy tube blanks with linear extension are obtained. A linearly extending copper or copper alloy tube blank is fed into a drawing die with a through hole and fitted onto a mandrel. The mandrel is movably disposed in the through hole along its own extension direction and extends outward from the outlet side of the through hole. The diameter of the through hole varies at various points along the extension direction of the mandrel, such that the diameter near the outlet side of the through hole is less than or equal to the diameter near the inlet side of the through hole. This variation also allows the through hole to restrict the mandrel from disengaging from the outlet side of the through hole. The radial dimension of the copper or copper alloy tube blank is reduced by the compression fit between the through hole and the mandrel. The through hole includes a clearance sub-hole and a limiting sub-hole connected in sequence. The diameter of the clearance sub-hole is greater than or equal to the diameter of the limiting sub-hole. The copper or copper alloy tube blank enters from the clearance sub-hole and extends out from the limiting sub-hole. The rod segment of the core rod located in the clearance sub-hole has a portion larger than the diameter of the limiting sub-hole. The copper or copper alloy tube blank with a reduced radial dimension is moved along the mandrel into a multi-roll mill assembly, the multi-roll mill assembly including at least three rolls uniformly surrounding the outer periphery of the mandrel, and the wall thickness of the copper or copper alloy tube blank is reduced by the spinning engagement of the multi-roll mill assembly and the mandrel; The rotation axis of the roll is perpendicular to the straight line of the extension direction of the core rod. During the rotation of the roll, the frictional force generated between the roll and the tube blank can drive the copper or copper alloy tube blank to move away from the drawing die. The plane containing the center of the at least three rolls is parallel to the radial plane of the mandrel, and the surfaces of the at least three rolls that contact the copper or copper alloy tube blank are joined together at the same position in the axial direction of the copper or copper alloy tube blank to form a complete circle.

2. The processing method of the copper or copper alloy heat transfer tube according to claim 1, characterized in that, The radial dimension reduction factor of the copper or copper alloy tube blank is thus adjusted by controlling the distance between the inner wall of the limiting sub-hole and the outer wall of the core rod.

3. The processing method of the copper or copper alloy heat transfer tube according to claim 1, characterized in that, The distance between any point on the inner wall of the limiting sub-hole and the outer wall of the core rod is the same.

4. The processing method of the copper or copper alloy heat transfer tube according to claim 1, characterized in that, The clearance sub-hole and the limiting sub-hole are integrally formed to constitute the through hole.

5. The processing method of the copper or copper alloy heat transfer tube according to claim 1, characterized in that, The radial dimensions of the rod segment located outside the through hole are the same at all points.

6. The processing method of the copper or copper alloy heat transfer tube according to claim 1, characterized in that, The multi-roll mill assembly has at least two rolls, each roll acting on a copper or copper alloy billet from a different direction.

7. The processing method of the copper or copper alloy heat transfer tube according to claim 1, characterized in that, The cross-sectional shape of the part where the roller and the mandrel interact is circular or non-circular, including triangular, hexagonal or rectangular shapes.

8. A processing assembly for copper or copper alloy heat transfer tubes, characterized in that, The processing assembly includes: a drawing die base with through holes, a mandrel, and a multi-roll mill assembly; The core rod is movably disposed in the through hole along its own extension direction and extends outward from the outlet side of the through hole; the diameter of the through hole varies at various points along the extension direction of the core rod, such that the diameter at various points near the outlet side of the through hole is less than or equal to the diameter at various points near the inlet side of the through hole, and such variation allows the through hole to restrict the core rod from disengaging from the outlet side of the through hole. The through hole includes a clearance sub-hole and a limiting sub-hole connected in sequence. The diameter of the clearance sub-hole is greater than or equal to the diameter of the limiting sub-hole. The copper or copper alloy tube blank enters from the clearance sub-hole and extends out from the limiting sub-hole. The rod segment of the core rod located in the clearance sub-hole has a portion larger than the diameter of the limiting sub-hole. The multi-roll mill assembly includes at least three rolls, which are uniformly arranged around the outer periphery of the mandrel. The rotation axis of the rolls is perpendicular to the straight line extending from the mandrel. The plane containing the center of the at least three rolls is parallel to the radial plane of the mandrel. The surfaces of the at least three rolls that contact the billet are joined together to form a complete circle at the same position in the axial direction of the copper or copper alloy billet.

Images