A powder filling extrusion forming process for high-quality copper pipe side branch

Abstract

The application provides a powder filling and extrusion forming process for a high-quality copper pipe side branch, and relates to the technical field of non-ferrous metal processing. A powder medium containing a main skeleton powder and a hot-melt adhesive powder is used to fill the inner cavity of a through pipe part to form a medium filling body. A branch forming section is determined on the medium filling body, and a first heating is performed on other regions of the medium filling body except the region corresponding to the branch forming section, so that the powder medium in the region subjected to the first heating forms a solidified support layer on the inner wall of the through pipe part. The formation of the solidified support layer enables partial powder medium to be bonded together, and in the cold extrusion process, the loss of the medium can be reduced, the powder medium has a good support effect, and the qualified rate of the finished product of the air conditioner pipe side branch is improved.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing technology, specifically to a powder-filling extrusion molding process for high-quality copper pipe side branch pipes. Background Technology

[0002] In air conditioning piping systems, side branch pipes (also known as branch pipes or branch pipes) are used to achieve the splitting or merging of refrigerant and are an important part of the air conditioning piping. Side branch pipes usually adopt a tee structure, and their forming quality directly affects the sealing performance and service life of the air conditioning system.

[0003] In the existing technology, the forming methods for air conditioning duct side branch pipes mainly include the following:

[0004] (a) Welding process

[0005] Prefabricated branch pipes are welded to the main pipe using brazing or argon arc welding. This process has several drawbacks, including: a heat-affected zone that leads to a decrease in the mechanical properties of the pipe; stress concentration at the weld, which can cause fatigue cracking and liquid leakage under vibration conditions in air conditioning systems; and complex welding procedures and low production efficiency.

[0006] (ii) Hydraulic bulging process

[0007] High-pressure liquid is injected into the inner cavity of the tube blank, and the liquid pressure causes the tube wall to bulge outward to form a branch pipe. This process requires a dedicated high-pressure sealing device, resulting in a large investment in equipment; the high-pressure liquid is prone to leakage from the seal, and the forming pressure is unstable; moreover, the high-pressure injection is carried out by dedicated equipment, which cannot meet the internal support requirements between multiple processes. Especially when processing side branches on through pipe fittings with a length greater than 20cm, the distance between the two ends of the through pipe fitting is relatively large, requiring a larger high-pressure sealing device.

[0008] (III) Solid Particle Media Forming Process

[0009] Solid particles (such as quartz sand, metal powder, etc.) are used as the force transmission medium, and the pressure is transmitted through extrusion to form the branch pipe. For example, Chinese patent application publication number CN103331329A, entitled "Powder Medium for Forming T-Type Pipes and its Forming Process," discloses "selecting a suitable straight pipe; filling the inner cavity of the straight pipe with a non-metallic mixed powder medium of 68%-87% industrial salt, 10%-15% soda ash, and 0-21% wetting agent; cold-extruded the straight pipe after filling with the powder medium to initially form a T-type two-way pipe; annealing the T-type two-way pipe; extruding the annealed T-type two-way pipe into the required t-type pipe; step six, removing the filled powder medium." Another example is patent application publication number CN101288881B, entitled "Non-metallic Filling Medium for Manufacturing Pipe Tees and its Use." A Chinese patent for the extrusion tee manufacturing process discloses that "the filling medium is a uniformly mixed non-metallic powder material, the formulation of which consists of three powders: talc powder (H2Mg3(SiO3)4), industrial salt (NaCl), and urea (NH2)2CO, mixed in mass ratios of 5-25%, 95-50%, and 0-25%, respectively. The main processing flow includes: feeding → filling the straight pipe with non-metallic powder material → cold extrusion → annealing → mechanical forming → removing the filled non-metallic powder material → pickling → drying → packaging."

[0010] Both the solid particle media molding process exemplified above and the conventional solid particle media molding process currently in use have the following problems: easy media loss: loose powder media is easily squeezed out from the tube opening during the extrusion process, especially in the early stage of side support molding, resulting in a reduction in media filling volume, a drop in internal pressure, and an inability to effectively support the tube wall; complex removal process: existing powder media usually require water dissolution or high-temperature incineration to remove; among them, the water dissolution method is difficult to thoroughly clean the dead corner areas of complex internal cavities, and media residue is easy to remain; the high-temperature incineration method has high energy consumption and may cause copper tube oxidation and discoloration, affecting the appearance quality.

[0011] To address the aforementioned issues, there is an urgent need to develop a forming process for air conditioning pipe side branch pipes that can balance forming support with easy removal, strong process adaptability, and high production efficiency. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention provides a powder-filled extrusion molding process for high-quality copper tubing side branches, which solves the problems that may exist in existing solid particle media molding processes, such as easy media loss, complex removal processes, poor process adaptability, and low production efficiency.

[0013] To achieve the above objectives, the present invention provides the following technical solution:

[0014] A powder-filled extrusion molding process for a high-quality copper tubing side branch pipe includes the following steps:

[0015] S1. Take a through pipe fitting and fill the inner cavity of the through pipe fitting with powder medium to form a medium filling body; wherein, the powder medium contains main skeleton powder and hot melt binder powder;

[0016] S2. Determine a branch pipe forming section on the medium filler, and perform a first heating on the other areas of the medium filler except for the area corresponding to the branch pipe forming section, so that the powder medium in the first heated area forms a solidified support layer on the inner wall of the pipe fitting; the formation of this solidified support layer causes some of the powder medium to bond together, which can reduce the loss of medium during the cold extrusion process, so that the powder medium has a better support effect and improves the finished product qualification rate of the air conditioning pipe side branch pipe.

[0017] S3. The medium filling material processed in step S2 is subjected to at least one cold extrusion to make the pipe wall of the branch pipe forming section bulge outward to form a side branch, thereby obtaining a semi-finished pipe fitting; wherein, the end of the side branch remains closed.

[0018] S4. The side branch of the semi-finished pipe is cut off at the end and bent into shape. Then, it is heated a second time to melt some of the components in the powder medium. The powder medium flows out and is then cleaned and dried to obtain the side branch of the air conditioning pipe.

[0019] It is understandable that the bending and forming process of the semi-finished pipe fittings is designed to be performed before the powder medium is removed, making the bending and forming of the semi-finished pipe fittings simpler and the finished product quality better (high consistency of the internal channels).

[0020] It is understandable that the two processes of cutting off the ends of the side branches of the semi-finished pipe fittings and bending the semi-finished pipe fittings are independent of each other, and their order has little impact on the finished product.

[0021] Preferably, the hot melt adhesive powder is a mixture of various materials including polyethylene wax, polypropylene wax, EVA resin, and petroleum resin.

[0022] The use of the above-mentioned synthetic wax or thermoplastic resin hot melt binder powder has the following advantages: on the one hand, it can melt at the first heating temperature and combine with the main skeleton powder to form a solidified support layer; on the other hand, it can melt completely at the second heating temperature and has good fluidity, which is conducive to the outflow of the powder medium; on the other hand, the synthetic wax or thermoplastic resin powder itself has a certain lubricating effect, which is conducive to the flow of the powder medium in the core and meets the requirements of the cold extrusion side support molding process.

[0023] Preferably, the hot melt adhesive powder is one of polyethylene wax, polypropylene wax, EVA resin, and petroleum resin.

[0024] The use of a single-component hot-melt binder powder facilitates subsequent separation and recycling.

[0025] For example, the hot melt adhesive powder is polyethylene wax, which has good recycling characteristics; the powder medium discharged after melting some of the components is heated and kept warm to separate the liquid phase and solid phase. The obtained liquid phase is cooled, crushed, sieved and reused. The separated solid phase is also reused after dispersion treatment.

[0026] Preferably, the main skeleton powder is a mixture of various powders including iron powder, copper powder, quartz sand powder, and calcium carbonate powder.

[0027] Iron powder, copper powder, quartz sand powder, and calcium carbonate powder all have good thermal stability. Using these powders as the main framework powders facilitates subsequent separation and recycling.

[0028] Preferably, the main skeleton powder is one of iron powder, copper powder, quartz sand powder, and calcium carbonate powder.

[0029] The single-component backbone powder has uniform physical properties such as particle morphology, particle size distribution, and hardness. It exhibits consistent deformation behavior and force transmission characteristics during cold extrusion, which helps to ensure the uniformity of tube wall deformation and forming accuracy.

[0030] Preferably, in step S1, filling the inner cavity of the through pipe with powder medium specifically includes:

[0031] First filling: Fill the inner cavity of the pipe fitting with powder medium to 60%-80% and then vibrate and compact the filled powder medium; the area filled with powder medium for the first time should at least cover the area corresponding to the branch pipe forming section.

[0032] Second filling: Fill the tube with powder medium until it is full, and then mechanically compact the filled powder medium.

[0033] By using a two-stage filling method, it can be ensured that the filling powder medium has a relatively dense filling effect in the center of the pipe fitting and near both ends of the pipe fitting.

[0034] Preferably, in step S2, the first heating is infrared focusing heating, the heating temperature is 100℃-130℃, and the heating time is 25s-45s.

[0035] For example, an annular infrared heater is used, which consists of an infrared-emitting heating wire and an annular transparent quartz tube containing the heating wire, and is in the shape of a cylindrical ring; the manipulator is inserted into the center of the annular infrared heater, and the manipulator is heated from the outside.

[0036] Preferably, the thickness of the cured support layer is 2mm-5mm, for example, the thickness of the cured support layer is 3mm, 4mm, or 5mm.

[0037] Preferably, in step S4, the temperature of the second heating is 120℃-150℃, and the holding time is 15min-30min.

[0038] Preferably, the powder medium also contains a lubricant to give the powder medium good fluidity, so that the powder medium flows into the interior of the side branch during the formation of the side branch.

[0039] Preferably, the lubricant is one of graphite powder and zinc stearate.

[0040] Preferably, the powder medium comprises, by weight ratio:

[0041] 40-60 parts of main skeleton powder;

[0042] 20-35 parts of hot melt adhesive powder;

[0043] 2-5 parts lubricant.

[0044] This invention provides a powder-filled extrusion molding process for high-quality copper tubing side branch pipes. It offers the following advantages:

[0045] 1. This invention uses a powder medium containing a main skeleton powder and a hot-melt binder powder to fill the inner cavity of a pipe fitting, forming a medium filler. A branch pipe forming section is defined on the medium filler. The areas of the medium filler other than the area corresponding to the branch pipe forming section are first heated, so that the powder medium in the first heated area forms a solidified support layer on the inner wall of the pipe fitting. The formation of this solidified support layer causes some of the powder medium to bond together, which can reduce the loss of medium during cold extrusion, so that the powder medium has a better support effect and improves the finished product qualification rate of the air conditioning pipe side branch pipe. The powder medium in the branch pipe forming section area still retains good fluidity, which meets the internal support requirements of the pipe wall of the branch pipe forming section to bulge outward to form a side branch during cold extrusion. Moreover, during material removal, a second heating is performed to melt some of the components in the powder medium, and the powder medium flows out. After cleaning and drying, the air conditioning pipe side branch pipe is obtained, thereby simplifying the powder medium removal process.

[0046] 2. In this invention, the bending and forming process of the semi-finished pipe fittings is designed to be carried out before the powder medium is unloaded, which makes the bending and forming of the semi-finished pipe fittings simpler and the finished product quality better.

[0047] 3. This invention utilizes a solidified support layer to better support the pipe fittings, thereby optimizing the cold extrusion process and ensuring the pass rate of the semi-finished products without annealing. Attached Figure Description

[0048] Figure 1 This is a flowchart of a powder-filling extrusion molding process for a high-quality copper pipe side branch pipe proposed in this invention.

[0049] Among them, 1 represents a through pipe fitting; 2 represents a medium filler; 3 represents a medium filler after the solidified support layer is formed; 4 represents a semi-finished pipe fitting; 5 represents a semi-finished pipe fitting after the bending and forming process; 6 represents a semi-finished pipe fitting after the end cutting process of the side branch; 7 represents a finished air conditioning pipe side branch pipe. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1:

[0052] This invention provides a powder medium, the components of which, by weight ratio, include: 50 parts of quartz sand powder and 37 parts of polyethylene wax powder.

[0053] Both the quartz sand powder and the polyethylene wax powder are sieved through a 200-mesh sieve.

[0054] Example 2:

[0055] This invention provides a powder medium, the components of which, by weight ratio, include: 52 parts iron powder; 35 parts petroleum resin powder; and 3 parts graphite powder.

[0056] Iron powder, petroleum resin powder, and graphite powder are all sieved through a 200-mesh sieve.

[0057] Example 3:

[0058] This invention provides a powder medium, the components of which, by weight ratio, include: 55 parts calcium carbonate powder; 31 parts petroleum resin powder; and 2 parts zinc stearate powder.

[0059] Calcium carbonate powder, petroleum resin powder, and zinc stearate powder are all powders that have passed through a 200-mesh sieve.

[0060] Example 4:

[0061] This invention provides a powder-filled extrusion molding process for high-quality copper tubing side branch pipes, comprising the following steps:

[0062] S1. Take the through pipe fitting and fill the inner cavity of the through pipe fitting with powder medium to form a medium filling body.

[0063] S2. Determine the branch pipe forming section on the medium filler, and perform a first heating on the other areas of the medium filler except for the area corresponding to the branch pipe forming section, so that the powder medium in the first heated area forms a solidified support layer on the inner wall of the pipe fitting.

[0064] The first heating method uses infrared focusing heating, with a heating temperature of 125℃ and a heating time of 35 seconds.

[0065] S3. The medium filler processed in step S2 is subjected to at least one cold extrusion to make the pipe wall of the branch pipe forming section bulge outward to form a side branch, thereby obtaining a semi-finished pipe fitting; wherein the end of the side branch remains closed.

[0066] S4. The side branch of the semi-finished pipe fitting is cut off at the end and bent into shape. Then, it is heated a second time to melt some components in the powder medium, causing the powder medium to flow out. After cleaning and drying, the air conditioning pipe side branch is obtained. The temperature of the second heating is 145℃, and the holding time is 20 minutes.

[0067] Example 5:

[0068] This invention provides a powder-filled extrusion molding process for high-quality copper tubing side branch pipes, comprising the following steps:

[0069] S1. Take the through pipe fitting and fill the inner cavity of the through pipe fitting with powder medium to form a medium filling body.

[0070] S2. The pipe fitting is subjected to at least one cold extrusion to make the pipe wall of the pipe fitting bulge outward to form a side support, thereby obtaining a semi-finished pipe fitting; wherein the end of the side support remains closed.

[0071] S3. The side branch of the semi-finished pipe is cut off at the end and bent into shape. Then, it is heated a second time to melt some of the components in the powder medium. The powder medium flows out and is then cleaned and dried to obtain the side branch of the air conditioning pipe.

[0072] The second heating temperature is 145℃, and the holding time is 20 minutes.

[0073] Example 6:

[0074] The present invention uses the powder medium in Example 1 and the powder filling and extrusion molding process of the air conditioning pipe side branch pipe in Example 4 to obtain the first batch of finished air conditioning pipe side branch pipes.

[0075] Raw material: T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm.

[0076] Finished air conditioning pipe side branch pipe: Main pipe outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm; length 60mm.

[0077] Example 7:

[0078] In this embodiment of the invention, the powder medium in Example 2 is used, and the powder filling and extrusion molding process of the air conditioning pipe side branch pipe in Example 4 is used to obtain the second batch of finished air conditioning pipe side branch pipes.

[0079] Raw material: T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm;

[0080] Finished air conditioning pipe side branch: Main pipe outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm; length 60mm.

[0081] Example 8:

[0082] The present invention uses the powder medium in Example 3 and the powder filling and extrusion molding process of the air conditioning pipe side branch pipe in Example 4 to obtain the third batch of air conditioning pipe side branch pipe finished products.

[0083] Raw material: T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm;

[0084] Finished air conditioning pipe side branch: Main pipe outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm; length 60mm.

[0085] Comparative Example 1:

[0086] The present invention uses the powder medium in Example 1 and the powder filling and extrusion molding process of the air conditioning pipe side branch pipe in Example 5 to obtain the fourth batch of air conditioning pipe side branch pipe finished products.

[0087] Raw material: T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm;

[0088] Finished air conditioning pipe side branch pipe: Main pipe outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm; length 60mm.

[0089] Comparative Example 2:

[0090] The present invention uses the powder medium in Example 2 and the powder filling and extrusion molding process of the air conditioning pipe side branch pipe in Example 5 to obtain the fifth batch of air conditioning pipe side branch pipe finished products.

[0091] Raw material: T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm;

[0092] Finished air conditioning pipe side branch pipe: Main pipe outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm; length 60mm.

[0093] Comparative Example 3:

[0094] The present invention uses the powder medium in Example 3 and the powder filling and extrusion molding process of the air conditioning pipe side branch pipe in Example 5 to obtain the sixth batch of air conditioning pipe side branch pipe finished products.

[0095] Raw material: T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm;

[0096] Finished air conditioning pipe side branch pipe: Main pipe outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm; length 60mm.

[0097] Comparative Example 4:

[0098] This invention provides a powder-filled extrusion molding process for high-quality copper tubing side branch pipes, comprising the following steps:

[0099] S1. Take a tube fitting (T2 copper tube; outer diameter Φ28 mm; wall thickness 1.8 mm; length 220 mm), fill the inner cavity of the tube fitting with powder medium to form a medium filling body; wherein, the powder medium used is quartz sand powder.

[0100] S2. The pipe fitting is subjected to at least one cold extrusion, and the pipe wall of the pipe fitting protrudes outward to form a side branch, thereby obtaining a semi-finished pipe fitting; wherein, the end of the side branch remains closed.

[0101] S3. The side branch of the semi-finished pipe is cut off at the end and bent into shape. Then, the filling powder medium is removed by water-soluble method to obtain the seventh batch of air conditioning pipe side branch finished products (main body outer diameter Φ27mm; length 200mm; side branch wall outer diameter 23mm and length 60mm).

[0102] The first to seventh batches of finished air conditioning pipe side branch pipes were tested (each batch of finished air conditioning pipe side branch pipes consisted of 100 finished air conditioning pipe side branch pipes produced continuously under the corresponding process), and the pass rate was calculated according to grade A, grade B, grade C, and scrap grade.

[0103] The evaluation criteria are shown in Table 1 below:

[0104]

[0105] Note that the lowest indicator level is used as the final grade of the product.

[0106] The pass rate is shown in Table 2 below:

[0107]

[0108] Note that the overall pass rate is the sum of the A-level pass rate, B-level pass rate, and C-level pass rate.

[0109] In Examples 6-8, a powder medium containing main skeleton powder and hot melt binder powder is used to fill the inner cavity of the pipe fitting to form a medium filling body. A branch pipe forming section is defined on the medium filling body, and the areas of the medium filling body other than the area corresponding to the branch pipe forming section are first heated. This causes the powder medium in the first heated area to form a solidified support layer on the inner wall of the pipe fitting. This method can reduce the loss of medium during cold extrusion, give the powder medium a better support effect, and improve the overall qualification rate of the air conditioning pipe side branch pipe (above 97%). The A-grade rate can reach above 85%, meeting the needs of high-quality air conditioning pipeline production.

[0110] In Comparative Examples 1-3, the filling powder medium formed by the main skeleton powder and hot melt binder powder was used. Without heating to form a solid support layer on the inner wall of the pipe fitting, the overall qualification rate of the finished air conditioning pipe side branch was 73%-82%, which was significantly lower than the overall qualification rate of 97%-99% for the finished air conditioning pipe side branch in Examples 6-8. It can be seen that heating to form a solid support layer on the inner wall of the pipe fitting can improve the overall qualification rate of the finished air conditioning pipe side branch.

[0111] Comparative Example 4 uses quartz sand powder to fill the inner cavity of the pipe fitting. During the cold extrusion process, the quartz sand powder has poor material fluidity and poor support effect on the inner wall of the branch pipe, resulting in a significant increase in the scrap rate of the finished air conditioning pipe side branch pipe.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A powder-filled extrusion molding process for a high-quality copper pipe side branch pipe, characterized in that, Includes the following steps: S1. Take a pipe fitting and fill the inner cavity of the pipe fitting with a powder medium to form a medium filler; wherein the powder medium contains a main skeleton powder and a hot melt adhesive powder; wherein the hot melt adhesive powder is one or more of polyethylene wax, polypropylene wax, EVA resin, and petroleum resin; and the main skeleton powder is one or more of iron powder, copper powder, quartz sand powder, and calcium carbonate powder. S2. Determine a branch pipe forming section on the medium filling body, and perform a first heating on the other areas of the medium filling body except for the area corresponding to the branch pipe forming section, so that the powder medium in the first heated area forms a solidified support layer on the inner wall of the pipe fitting; wherein, the first heating adopts infrared focusing heating, the heating temperature is 100℃-130℃, and the heating time is 25s-45s. S3. The medium filling material processed in step S2 is subjected to at least one cold extrusion to make the pipe wall of the branch pipe forming section bulge outward to form a side branch, thereby obtaining a semi-finished pipe fitting; wherein, the end of the side branch remains closed. S4. The side branch of the semi-finished pipe is cut off at the end and bent into shape. Then, it is heated a second time to melt some of the components in the powder medium and the powder medium flows out. After cleaning and drying, the air conditioning pipe side branch is obtained. The temperature of the second heating is 120℃-150℃ and the holding time is 15min-30min.

2. The powder-filling extrusion molding process for a high-quality copper pipe side branch pipe according to claim 1, characterized in that: In step S1, filling the inner cavity of the through pipe with powder medium specifically includes: First filling: Fill the inner cavity of the pipe fitting with powder medium to 60%-80% and then vibrate and compact the filled powder medium. Second filling: Fill the tube with powder medium until it is full, and then mechanically compact the filled powder medium.

3. The powder-filling extrusion molding process for a high-quality copper pipe side branch pipe according to claim 1, characterized in that: The thickness of the cured support layer is 2mm-5mm.

4. The powder-filling extrusion molding process for a high-quality copper pipe side branch pipe according to claim 1, characterized in that: The powder medium also contains a lubricant.

5. The powder-filling extrusion molding process for a high-quality copper pipe side branch pipe according to claim 4, characterized in that: The lubricant is one of graphite powder and zinc stearate.

6. The powder-filling extrusion molding process for a high-quality copper pipe side branch pipe according to claim 1, characterized in that, The powder medium comprises, by weight ratio: 40-60 parts of main skeleton powder; 20-35 parts of hot melt adhesive powder; 2-5 parts lubricant.

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