CN113714416B - Small-radius bent pipe forming process of U-shaped heat exchange pipe - Google Patents
Small-radius bent pipe forming process of U-shaped heat exchange pipe Download PDFInfo
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- CN113714416B CN113714416B CN202111058475.2A CN202111058475A CN113714416B CN 113714416 B CN113714416 B CN 113714416B CN 202111058475 A CN202111058475 A CN 202111058475A CN 113714416 B CN113714416 B CN 113714416B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D53/00—Making other particular articles
- B21D53/02—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers
- B21D53/06—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers of metal tubes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D9/00—Bending tubes using mandrels or the like
- B21D9/04—Bending tubes using mandrels or the like the mandrel being rigid
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Mechanical Engineering (AREA)
- Bending Of Plates, Rods, And Pipes (AREA)
- Shaping Of Tube Ends By Bending Or Straightening (AREA)
Abstract
The specific technical scheme of the invention is as follows: a small radius bend forming process of U-shaped heat exchange tube comprises the following steps, (1) loading and positioning; (2) clamping the pipe fitting (3) bending the pipe fitting; the range of the distance d between the junction of the main body section and the rounding head section and exceeding the bending starting point of the pipe fitting is 4-5 mm, and the relation between the diameter od of the main body section and the inner diameter ID of the pipe fitting is od=ID-0.5 mm. After the pipe fitting is bent into the finished pipe with R less than or equal to 3OD, the outer diameter of the bent pipe section can be stably controlled to be ideal 0.9 OD-1.1 OD, the ellipticity of the bent pipe section is stably controlled to be less than ideal 20%, the conventional step can be still adopted in the pipe bending step, the pipe bending efficiency is high, the bent pipe section is smooth and does not wrinkle, the quality of the finished pipe is generally and stably and controllably improved greatly, and the use effect of the pipe in a pipe heat exchanger is greatly improved, so that the pipe heat exchanger is worthy of popularization and use in the field.
Description
Technical Field
The invention relates to the technical field of cored elbows, in particular to a small-radius elbow forming process of a U-shaped heat exchange tube.
Background
The heat exchanger is a device for heating or cooling one medium by using the other medium, the two mediums have different temperatures, and generally have different medium components, and the heat exchanger is divided into a tubular heat exchanger and a plate heat exchanger according to a medium isolation mode, wherein heat exchange tubes adopted by the tubular heat exchanger have different forms, and mainly comprise straight tubes and U-shaped tubes. The U-shaped heat exchange tube is formed by cold bending a straight tube, the U-shaped heat exchange tube is provided with a straight tube section and a bent tube section, high-temperature and high-pressure liquid is generally introduced into the U-shaped tube, the flow speed is relatively high in order to improve the heat exchange efficiency, if the ovality difference between the bent tube section and the straight tube section is relatively large, turbulent flow is generated at the transition part of the fluid passing through the straight tube section and the bent tube section, and therefore vibration of the tube bundle is overlarge, and the use of equipment is affected.
Referring to fig. 1, the inside and outside diameters of the straight pipe section are respectively ID and OD, the bending radius of the bent pipe section is R, the deformation degree of the bent pipe section changes along with the change of the bending radius R, and the main reference parameters of the deformation are the outside diameter, ovality, wall thickness and the like of the bent pipe section. The difficulty of controlling the deformation is also different for different bending radii R, especially for U-shaped heat exchange tubes with bending radii r.ltoreq.3×od, which are also called small radii. Generally speaking, the ideal heat exchange tube product parameters are that the outer diameter of the bent tube section is in the range of 0.9-1.1 OD, and the ellipticity is 20-3 OD or less, but for the U-shaped heat exchange tube with R less than or equal to 3OD, the conventional tube bending forming process often has difficulty in ensuring that the outer diameter of the bent tube section is in the proper range, the ellipticity also often reaches about 30% OD, for example, the thin-wall small-radius tube rapid cold-drawing technology disclosed in the chinese patent application No. CN201710147704.5 is adopted, the thin-wall small-radius tube is rapidly cold-drawn by adopting a thin-wall small-radius tube bender, and the following steps are adopted for processing: a. core feeding; b. clamping in; c. bending in; d. core withdrawal; e. clamping and backing; f. the guiding die is retracted, and the pipe bending efficiency is high and the pipe can be bent without wrinkling and the bending surface is smooth, but the pipe manufactured by the scheme still can not meet the proper standard in the aspect of controlling and forming the outer diameter and ellipticity of the bent pipe section.
While other bend forming processes, such as hot bending or processes utilizing ball and socket joint rods, have the ability to control the forming outer diameter and ovality of the bend section, they are not suitable for processing U-shaped heat exchange tubes, so in order to effectively control the small radius bend section diameter and ovality of the U-shaped heat exchange tubes used in tube heat exchangers to meet predetermined forming criteria, new breakthroughs need to be sought based on existing bend processes.
Disclosure of Invention
The invention aims to provide a small-radius bend forming process of a U-shaped heat exchange tube, which solves the problem that the diameter and ellipticity of a bend section of the U-shaped heat exchange tube for a tube heat exchanger after small-radius bend processing cannot reach proper standards in the prior art.
The specific technical scheme of the invention is as follows: a small radius bend forming process of U-shaped heat exchange tube comprises the following steps,
(1) Feeding and positioning: the pipe fitting is placed in the guide cavity, the core rod is inserted into the pipe fitting, meanwhile, the pipe fitting is placed in the cavity of the pipe bending die, the pipe fitting is provided with a bending starting point serving as the junction of the bent pipe section and the straight pipe section, the core rod comprises a main body section and a rounding head section, and the junction of the rounding head section and the main body section exceeds the bending starting point;
(2) Clamping a pipe fitting: clamping the pipe fitting and the pipe bending die together through the pipe bending clamp;
(3) Bending pipe fitting: the pipe bending die and the pipe bending clamp drive the pipe fitting to rotate along with the circumference of the pipe bending die until the pipe fitting is formed into a U-shaped pipe from a straight pipe;
the range of the distance d between the junction of the main body section and the rounding head section and exceeding the bending starting point is 4-5 mm, and the relation between the diameter od of the main body section and the inner diameter ID of the pipe fitting is od=ID-0.5 mm.
The applicant has found that the existing bend forming process often only focuses on how to smooth, wrinkle-free, fracture-free finished bend sections, which, although well established, ignores the problem of how to stabilize finished bend sections to the desired dimensional specifications for practical use. The applicant researches that the outside diameter of a bent pipe section of a finished product of a U-shaped heat exchange pipe with a bending radius of small radius (R is less than or equal to 3 OD) is controlled to be ideally 0.9-1.1 OD, and ellipticity is controlled to be ideally below 20 percent, so that high-temperature, high-pressure and high-speed fluid cannot generate turbulent flow when flowing in the U-shaped heat exchange pipe, and excessive vibration affecting the use of the heat exchange pipe bundle is avoided, but even the existing forming process applicable to the U-shaped heat exchange pipe is difficult to manufacture products with ideal dimension specifications, other bending forming processes such as hot working, follow-up ball joint core rods and the like are basically not applicable to the U-shaped heat exchange pipe, and the rotating difficulty is high.
In the process of bending the pipe, the stress and the strain in the bending part of the pipe are changed in a complex manner, the cross section of the bending part of the pipe is deformed into an approximate ellipse under the combined action of the outside tension and the inside pressure, and the smaller the bending radius R is, the larger the combined action force is, and the more remarkable the deformation is. The U-shaped heat exchange tube is formed by a cored pipe bending process, namely a process of inserting a core rod into a pipe fitting and bending the pipe fitting, wherein the core rod is a fixed columnar core rod. The larger the diameter of the core rod is, the easier the core rod is to be clamped during insertion and extraction, and the easier the inner wall of the heat exchange tube is stretched during bending, so that the appearance is not smooth enough; the smaller the diameter of the mandrel, the larger the gap between the mandrel and the inner wall of the pipe, the more easily the outside of the bent pipe section is flattened and the more easily the inside is wrinkled. The mandrel is also required to be inserted into a pipe bending section to a certain position, namely the distance d between the junction of the rounding head section and the main body section and the bending starting point is larger than the distance d, if the mandrel is inserted too deeply, the pipe wall is possibly crushed in the bending process; if the insertion is insufficient, the corresponding anti-flattening and anti-wrinkling effects are not achieved (the core rod is inserted originally to prevent the bending section from being excessively flattened and wrinkled). Through research practice, under the condition that the rest conditions meet the normal processing requirement, the applicant finds that the diameter of the core rod and the insertion degree of the core rod are both the most critical forming factors, and the U-shaped heat exchange tube with the ideal size specification can be finally obtained and can be obtained more stably under the matched value condition that d is more than or equal to 4 and less than or equal to 5mm and od is less than or equal to ID-0.5mm.
Preferably, the outer diameter OD of the pipe fitting suitable for the process is 16.00-32.00 mm, and the wall thickness T is 0.80-2.50 mm.
The process is particularly aimed at the U-shaped heat exchange tube of the tube heat exchanger, and when the outer diameter and the wall thickness of the tube are the sizes, the forming effect is more excellent and stable.
Preferably, the surface roughness Ra of the mandrel bar is 3.2 μm or less.
The surface roughness influences the smoothness of the bending section molding, and also influences the abrasion degree of the core rod and the inner wall of the pipe, when the abrasion is quicker or more serious, the gap between the core rod and the inner wall of the pipe is increased, the outer side of the bending section is easy to flatten, the inner side is easy to wrinkle, and the surface roughness is less than 3.2 mu m, so that good molding quality and service life can be ensured in the scheme.
Preferably, the mandrel is a hard nylon mandrel.
The hard nylon core rod has good surface roughness conforming to the scheme, has good and stable wear resistance, stretching and bending properties, can not only sufficiently support the inner wall of the pipe fitting when the pipe fitting is bent, but also can follow stretching and bending to a certain extent, ensures smooth and uncreped forming, reduces the flattening degree as much as possible, and is more beneficial to meeting the requirements of the target outer diameter and ovality to be obtained by the scheme.
Preferably, the length L of the mandrel bar is in the range of 90 to 100mm.
The length L of the mandrel achieves a good shaping effect in this range, i.e. ensures adequate support of the tube on the basis of ease of manufacture, installation and cost-effectiveness.
Preferably, the range of the radius r corresponding to the arc segment of the rounding head segment is 3-4 mm.
The rounding head section can be in a complete ball head or peripheral part rounding form, and the corresponding radius r of the arc section achieves a good forming effect in the range, namely, extrusion of the bending section is reduced, sufficient support is provided, smooth and uncreped forming is ensured, the flattening degree is reduced as much as possible, and the requirements of the target outer diameter and ellipticity to be obtained by the scheme are more favorably met.
The invention has the technical advantages that the forming process is characterized in that through the matching arrangement of the material of the core rod, the diameter od, the distance d extending into the bent pipe section and the like, after the core rod is cold-bent into the small-radius U-shaped pipe with the bending radius R less than or equal to 3X OD, the outer diameter of the bent pipe section can be stably controlled to be ideal 0.9X OD-1.1X OD, the ellipticity of the bent pipe section is stably controlled to be less than ideal 20%, the bending step can still follow the traditional step, the efficiency of the bent pipe is high, the bent pipe section is smooth and does not wrinkle, the quality of a finished product is generally and stably and controllably greatly improved, and the use effect of the bent pipe section in a tubular heat exchanger is also greatly improved, so the bent pipe heat exchanger is worthy of popularization and use in the field.
Drawings
FIG. 1 is a schematic structural diagram of a U-shaped heat exchange tube according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a pipe bender and pipe fitting according to an embodiment of the present invention;
FIG. 3 is a schematic view of a mandrel and a pipe according to an embodiment of the present invention;
the names of the parts corresponding to the numbers in the figure are respectively as follows: the pipe fitting comprises a 1-pipe fitting, a 2-core rod, a 21-main body section, a 22-rounding head section, a 3-pipe bending die, a 4-pipe bending fixture, a 5-guide seat, a 51-guide wheel, a 6-pull rod, an a-bending starting point and a b-rounding head section and a main body section.
Detailed Description
The invention will be further illustrated by the following examples, taken in conjunction with the accompanying drawings:
embodiment one: a small radius bend forming process of U-shaped heat exchange tube uses the existing common tube bender to perform bending processing to obtain U-shaped heat exchange tube of tube heat exchanger shown in figure 1, and referring to figures 2 and 3, the following steps are performed,
(1) Feeding and positioning: the pipe fitting 1 is placed into a guide cavity of a pipe bending machine, a core rod 2 is inserted into the pipe fitting 1, meanwhile, the pipe fitting 1 is placed into a cavity of a pipe bending die 3 of the pipe bending machine, the pipe fitting 1 is provided with a bending starting point a serving as a junction of a bent pipe section and a straight pipe section, the core rod 2 comprises a main body section 21 and a rounding head section 22, the tail end of the core rod 2 is connected with a pull rod 6, the pull rod 6 is fixed by an external fixed connecting piece, the pull rod 6 extends out of the pipe fitting 1, and a junction b of the rounding head section 22 and the main body section 21 exceeds the bending starting point a;
(2) Clamping a pipe fitting: clamping the pipe fitting 1 and the pipe bending die 3 together by the pipe bending clamp 4;
(3) Bending pipe fitting: the pipe bending die 3 and the pipe bending clamp 4 drive the pipe fitting 1 to rotate along with the circumference of the pipe bending die 3, and the guide seat 5 with the guide wheel 51 is matched with the guide cavity to guide the pipe fitting 1 in bending until the pipe fitting 1 is formed into a U-shaped pipe from a straight pipe.
The dimension specification of the raw pipe fitting is that the outer diameter od=16 mm, the inner diameter id=14.4 mm, namely the wall thickness t=0.8 mm, the mandrel 2 is made of hard nylon material, and is a cylindrical mandrel, the surface roughness Ra is smaller than 3.2 μm, the diameter od=13.90 mm (smaller than the inner diameter ID by 0.5 mm) of the main body section 21 of the mandrel 2, the distance d=4.0 mm between the boundary b of the main body section 21 and the rounding head section 22 exceeds the bending point a, the length l=90 mm of the mandrel, and the radius r=3 mm of the rounding head section, and refer to fig. 3.
And processing the raw material pipe fitting into a U-shaped heat exchange pipe with a bending radius R=48 mm (R is less than or equal to 3X OD), wherein the maximum outer diameter of a bent pipe section of the finished product obtained after processing is 16.85mm, the minimum outer diameter of the bent pipe section is 14.77mm, the ellipticity of the bent pipe section is 13%, the outer diameter of the bent pipe section is in the range of 0.9X OD to 1.1X OD (namely 14.40 to 17.60 mm), the ellipticity of the bent pipe section is below 20%, and the finished product pipe is a qualified product.
Embodiment two: the steps are the same as those of the first embodiment, and differ from those of the first embodiment in that the distance d=4.5 mm between the junction b of the main body section 21 and the rounding head section 22 and beyond the starting point a.
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 17.20mm, the minimum outer diameter is 15.28mm, the ellipticity of the bent pipe section is 12%, the outer diameter of the bent pipe section is in the range of 0.9-1.1-1-2 (namely 14.40-17.60 mm), the ellipticity of the bent pipe section is below 20%, and the finished pipe is qualified.
Embodiment III: the steps are the same as those of the first embodiment, and differ from those of the first embodiment in that the distance d=5.0 mm between the junction b of the main body section 21 and the rounding head section 22 and beyond the starting point a.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 16.90mm, the minimum outer diameter is 14.66mm, so that the ellipticity of the bent pipe section is 14%, the outer diameter of the bent pipe section is in the range of 0.9-1.1-1-14 mm (namely 14.40-17.60 mm), the ellipticity of the bent pipe section is below 20%, and the finished pipe is qualified.
Comparative example 1.1: the steps are the same as those of the first embodiment, and differ from those of the first embodiment in that the distance d=3.5 mm between the junction b of the main body section 21 and the rounding head section 22 and beyond the starting point a.
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 17.26mm, the minimum outer diameter is 14.38mm, the ellipticity of the bent pipe section is 18%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-14 (i.e. 14.40-17.60 mm), and the finished pipe is a defective product.
Comparative example 1.2: the steps are the same as those of the first embodiment, and differ from those of the first embodiment in that the distance d=5.5 mm between the junction b of the main body section 21 and the rounding head section 22 and beyond the starting point a.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 16.60mm, the minimum outer diameter is 13.56mm, the ellipticity of the bent pipe section is 19%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-14.60 mm (namely, 14.40-17.60 mm), and the finished pipe is a defective product.
Comparative example 1.3: the procedure is the same as in the first embodiment, but differs from the first embodiment in that the diameter od of the main body section 21 of the mandrel 2=13.70 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm).
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 17.10mm, the minimum outer diameter is 14.06mm, the ellipticity of the bent pipe section is 19%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-14.60 mm (namely, 14.40-17.60 mm), and the finished pipe is a defective product.
Comparative example 1.4: the procedure is similar to the first embodiment and differs from the second embodiment in that the diameter od of the main body section 21 of the mandrel 2 is=13.70 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm).
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 17.00mm, the minimum outer diameter is 14.12mm, the ellipticity of the bent pipe section is 18%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-14.60 mm (namely, 14.40-17.60 mm), and the finished pipe is a defective product.
Comparative example 1.5: the procedure is the same as in the first embodiment, but differs from that of the third embodiment in that the diameter od=13.70 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 16.90mm, the minimum outer diameter is 14.18mm, the ellipticity of the bent pipe section is 17%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-14 mm (namely 14.4-17.6 mm), and the finished pipe is a defective product.
Embodiment four: the procedure is the same as in the first embodiment, and other specific parameters are set in such a way that the dimension of the raw pipe is od=19.05 mm, id=15.75 mm, i.e. the wall thickness t=1.625 mm, the mandrel 2 is made of hard nylon material, and is a cylindrical mandrel with a surface roughness Ra of less than 3.2 μm, the diameter od=15.25 mm (0.5 mm smaller than ID), the distance d=4.0 mm between the junction b of the main body section 21 and the rounding head section 22 exceeds the starting point a, the length l=90 mm of the mandrel, and the radius r=3 mm of the rounding head section.
And processing the raw material pipe fitting into a U-shaped heat exchange pipe with a bending radius R=28 mm (R is less than or equal to 3X OD), wherein the maximum outer diameter of a bent pipe section of the finished product obtained after processing is 20.05mm, the minimum outer diameter of the bent pipe section is 18.02mm, the ellipticity of the bent pipe section is 13%, the outer diameter of the bent pipe section is in the range of 0.9X OD to 1.1X OD (namely 17.145 to 20.955 mm), the ellipticity of the bent pipe section is less than 20%, and the finished product pipe is a qualified product.
Fifth embodiment: the step is similar to the first embodiment and differs from the fourth embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=4.5 mm from the starting point a.
The maximum outer diameter of the bent pipe section of the finished product obtained after processing is 20.20mm, the minimum outer diameter is 18.10mm, the ellipticity of the bent pipe section is 11%, the outer diameter of the bent pipe section is in the range of 0.9-1.1-1-5 mm (namely 17.145-20.955 mm), the ellipticity of the bent pipe section is below 20%, and the finished product pipe is qualified.
Example six: the step is different from the first embodiment and the fourth embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=5.0 mm from the starting point a.
The maximum outer diameter of the bent pipe section of the finished product obtained after processing is 20.30mm, the minimum outer diameter is 18.40mm, the ellipticity of the bent pipe section is 10%, the outer diameter of the bent pipe section is in the range of 0.9-1.1-1-5 mm (namely 17.145-20.955 mm), the ellipticity of the bent pipe section is below 20%, and the finished product pipe is qualified.
Comparative example 2.1: the step is similar to the first embodiment and differs from the fourth embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=3.5 mm from the starting point a.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 20.25mm, the minimum outer diameter is 16.63mm, the ellipticity of the bent pipe section is 19%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-17 (i.e. 17.145-20.955 mm), and the finished pipe is a defective product.
Comparative example 2.2: the step is similar to the first embodiment and differs from the fourth embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=5.5 mm from the starting point a.
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 20.14mm, the minimum outer diameter is 16.71mm, the ellipticity of the bent pipe section is 18%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-17 (i.e. 17.145-20.955 mm), and the finished pipe is a defective product.
Comparative example 2.3: the procedure is the same as in the first embodiment, but differs from that of the fourth embodiment in that the diameter od=15.05 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 21.20mm, the minimum outer diameter is 17.01mm, the ovality of the bent pipe section is 22%, wherein the maximum outer diameter and the minimum outer diameter of the bent pipe section are both beyond the range of 0.9-1.1-1-5 mm (namely 17.145-20.955 mm), the ovality of the bent pipe section is also beyond 20%, and the finished pipe is a defective product.
Comparative example 2.4: the procedure is the same as in the first embodiment, but differs from that of the fifth embodiment in that the diameter od=15.05 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 21.30mm, the minimum outer diameter is 17.68mm, the ellipticity of the bent pipe section is 19%, wherein the maximum outer diameter and the minimum outer diameter of the bent pipe section are both beyond the range of 0.9-1.1-1-namely 17.145-20.955 mm, and the finished pipe is a defective product.
Comparative example 2.5: the procedure is identical to that of the first embodiment and differs from that of the sixth embodiment in that the diameter od=15.05 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 20.68mm, the minimum outer diameter is 16.68mm, the ellipticity of the bent pipe section is 21%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-5 mm (namely 17.145-20.955 mm), the ellipticity of the bent pipe section also exceeds 20%, and the finished pipe is a defective product.
Embodiment seven: the procedure is the same as in the first embodiment, and other specific parameters are set in such a way that the dimension of the raw pipe is od=32 mm, id=27 mm, that is, the wall thickness t=2.5 mm, the mandrel 2 is made of a hard nylon material, and is a cylindrical mandrel, the surface roughness Ra is smaller than 3.2 μm, the diameter od= 26.50mm (smaller than 0.5mm than ID), the distance d=4.0 mm between the boundary b of the main body section 21 and the rounding head section 22 exceeds the starting point a, the length l=100 mm, and the radius r=4 mm of the rounding head section.
And processing the raw material pipe fitting into a U-shaped heat exchange pipe with a bending radius R=48 mm (R is less than or equal to 3X OD), wherein the maximum outer diameter of a bent pipe section of the finished product obtained after processing is 34.20mm, the minimum outer diameter of the bent pipe section is 30.38mm, the ellipticity of the bent pipe section is 12%, the outer diameter of the bent pipe section is in the range of 0.9X OD to 1.1X OD (namely 28.8 to 35.2 mm), the ellipticity of the bent pipe section is below 20%, and the finished product pipe is qualified.
Example eight: the step is different from the first embodiment and the seventh embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=4.5 mm of the starting point a.
The maximum outer diameter of the bent pipe section of the finished product obtained after processing is 33.80mm, the minimum outer diameter is 30.62mm, the ellipticity of the bent pipe section is 10%, the outer diameter of the bent pipe section is in the range of 0.9-1.1-1-od (28.8-35.2 mm), the ellipticity of the bent pipe section is below 20%, and the finished product pipe is qualified.
Example nine: the step is different from the first embodiment and the seventh embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=5.0 mm of the starting point a.
The maximum outer diameter of the bent pipe section of the finished product obtained after processing is 34.10mm, the minimum outer diameter is 29.65mm, the ellipticity of the bent pipe section is 14%, the outer diameter of the bent pipe section is in the range of 0.9-1.1-1-od (28.8-35.2 mm), the ellipticity of the bent pipe section is below 20%, and the finished product pipe is qualified.
Comparative example 3.1: the step is different from the first embodiment and the seventh embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=3.5 mm of the starting point a.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 34.50mm, the minimum outer diameter is 28.46mm, the ellipticity of the bent pipe section is 19%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-OD (namely 28.8-35.2 mm), and the finished pipe is a defective product.
Comparative example 3.2: the step is different from the first embodiment and the seventh embodiment in that the junction b of the main body section 21 and the rounding head section 22 exceeds the distance d=5.5 mm of the starting point a.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 34.60mm, the minimum outer diameter is 28.56mm, the ellipticity of the bent pipe section is 19%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-OD (namely 28.8-35.2 mm), and the finished pipe is a defective product.
Comparative example 3.3: the procedure is the same as in the first embodiment and differs from that of the seventh embodiment in that the diameter od=26.30 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 34.70mm, the minimum outer diameter is 27.70mm, the ellipticity of the bent pipe section is 22%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-2 od (namely 28.8-35.2 mm), the ellipticity of the bent pipe section exceeds 20%, and the finished pipe is a defective product.
Comparative example 3.4: the procedure is the same as in the first embodiment, but differs from that of the eighth embodiment in that the diameter od=26.30 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of a bent pipe section of the U-shaped heat exchange pipe obtained after processing is 35.00mm, the minimum outer diameter of the bent pipe section is 28.64mm, the ellipticity of the bent pipe section is 20%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-OD (namely 28.8-35.2 mm), and the finished pipe is a defective product.
Comparative example 3.5: the procedure is the same as in the first embodiment, but differs from the ninth embodiment in that the diameter od=26.30 mm (0.7 mm smaller than the inner diameter ID instead of 0.5 mm) of the main body section 21 of the mandrel 2.
The maximum outer diameter of the bent pipe section of the U-shaped heat exchange pipe obtained after processing is 34.60mm, the minimum outer diameter is 27.92mm, the ellipticity of the bent pipe section is 21%, wherein the minimum outer diameter of the bent pipe section exceeds the range of 0.9-1.1-1-2 od (namely 28.8-35.2 mm), the ellipticity of the bent pipe section exceeds 20%, and the finished pipe is a defective product.
In other embodiments, the diameter od of the main body section 21 of the mandrel 2 is made to be the size of ID-od < 0.5mm, but relatively large friction between the mandrel 2 and the inner wall of the pipe fitting 1 occurs, the mandrel 2 is not inserted smoothly, various degrees of clamping and inner wall extrusion occur during bending, and the manufactured bent pipe section is large in difference from the normal shape, and even has the effects of cracks, wrinkling and forced shutdown.
The technology is practically explored to obtain a main technical scheme of relatively fixed value matching of the diameter od of the core rod and the distance d of the core rod extending into the bent pipe section, the traditional mode can be still adopted on pipe bending equipment and steps, the small-radius U-shaped heat exchange pipe with the outer diameter of the bent pipe section of 0.9-1.1 OD and the ellipticity of the bent pipe section of less than or equal to 3OD can be basically and stably produced, the pipe bending efficiency is high, the bent pipe section is smooth and does not wrinkle, the quality of a finished product is stably and controllably greatly improved, and the use effect of the finished product in the pipe heat exchanger is greatly improved, so the technology is worthy of popularization and use in the field.
It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are by way of example only and are not limiting. The objects of the present invention have been fully and effectively achieved. The functional and structural principles of the present invention have been shown and described in the examples and embodiments of the present invention may be modified or practiced without departing from the principles.
Claims (6)
1. A small radius bend forming process of U-shaped heat exchange tube comprises the following steps,
(1) Feeding and positioning: the pipe fitting is placed in the guide cavity, the core rod is inserted into the pipe fitting, meanwhile, the pipe fitting is placed in the cavity of the pipe bending die, the pipe fitting is provided with a bending starting point serving as the junction of the bent pipe section and the straight pipe section, the core rod comprises a main body section and a rounding head section, and the junction of the rounding head section and the main body section exceeds the bending starting point;
(2) Clamping a pipe fitting: clamping the pipe fitting and the pipe bending die together through the pipe bending clamp;
(3) Bending pipe fitting: the pipe bending die and the pipe bending clamp drive the pipe fitting to rotate along with the circumference of the pipe bending die until the pipe fitting is formed into a U-shaped pipe from a straight pipe;
the method is characterized in that: the range of the distance d between the junction of the main body section and the rounding head section and exceeding the bending starting point is 4.0-5.0 mm, and the relation between the diameter od of the main body section and the inner diameter ID of the pipe fitting is od=ID-0.5 mm;
the outer diameter of the straight tube section is OD, the bending radius of the bent tube section is R, and for U-shaped heat exchange tubes with the bending radius R less than or equal to 3OD, the bending radius is called as a small radius.
2. The process for forming a small-radius bend of a U-shaped heat exchange tube according to claim 1, wherein: the outer diameter OD of the pipe fitting suitable for the process is 16.00-32.00 mm, and the wall thickness T is 0.80-2.50 mm.
3. The process for forming a small-radius bend of a U-shaped heat exchange tube according to claim 1, wherein: the surface roughness Ra of the mandrel bar is below 3.2 mu m.
4. A small radius bend forming process of a U-shaped heat exchange tube according to claim 1 or 2, wherein: the core rod is a hard nylon core rod.
5. The process for forming a small-radius bend of a U-shaped heat exchange tube according to claim 1, wherein: the length L of the core rod ranges from 90mm to 100mm.
6. The process for forming a small-radius bend of a U-shaped heat exchange tube according to claim 1, wherein: the range of the corresponding radius r of the arc section of the rounding head section is 3-4 mm.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN88211031U (en) * | 1988-01-19 | 1988-12-14 | 南京化学工业公司化工机械厂设备配件分厂 | Device for small curvature winding pipe forming |
| CN100491010C (en) * | 2005-08-09 | 2009-05-27 | 十堰市风雷工贸有限公司 | Shaping method of small curvature radius bend pipe |
| CN200963654Y (en) * | 2006-05-25 | 2007-10-24 | 贾其书 | Bending die for pipe |
| CN201127971Y (en) * | 2007-11-29 | 2008-10-08 | 上海交通大学 | Digital control pipe bender mold for hot bending |
| CN202070623U (en) * | 2011-05-13 | 2011-12-14 | 常州腾龙汽车零部件股份有限公司 | Mould preventing elbow pipe from sinking and wrinkling |
| CN109791029B (en) * | 2016-11-11 | 2020-10-09 | 康奈可关精株式会社 | Method for manufacturing tube with built-in fin and method for manufacturing double-layer tube |
| CN111069370A (en) * | 2019-11-19 | 2020-04-28 | 中国船舶重工集团公司第七二五研究所 | Numerical control heating bending forming method for thick-wall titanium alloy pipe |
| CN112122419A (en) * | 2020-09-10 | 2020-12-25 | 西北工业大学 | Bending die with small bending radius and bending method of bent pipe |
| CN213195157U (en) * | 2020-09-14 | 2021-05-14 | 无锡华光工业锅炉有限公司 | Pipe bending die structure for bending pipe |
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