Method for improving bending yield of thin-walled pipe

Abstract

The invention discloses a method for increasing the bending yield of a thin-walled tube, and relates to the technical field of Coriolis force mass flow meters. The method comprises the following steps: inserting a dense spring group into a thin-walled tube to enable two ends of the dense spring group to extend out of two ends of the thin-walled tube, and bending the thin-walled tube; the difference between the outer diameter of the dense spring group and the inner diameter of the thin-walled tube is not more than 0.2 mm; the thin-walled tube and the dense spring group are made of steel; the dense spring group is a spiral spring with a uniform diameter and a spiral angle within 5 degrees; and the width of a gap between adjacent coils of the dense spring group is 0-0.5 mm. The thin-walled tube and the dense spring set are matched in material, and the adopted materials and steps are simple; due to the diameter difference and the structure of the dense spring set, the dense spring set has a strong supporting effect, and meanwhile the process that the dense spring set is inserted into the thin-walled tube is smooth; the thin-wall bent pipe prepared by the bending method based on the thin-wall pipe and dense spring group structure is basically not wrinkled or broken at the bending part, and the prepared thin-wall bent pipe is good in consistency and high in yield.

Description

Technical Field

[0001] The present application relates to the technical field of Coriolis mass flowmeters, and in particular to a method for improving the yield of thin-walled tube bending. Background Art

[0002] When the fluid flows in a steady-state stimulated pipe, it will generate a Coriolis force proportional to the mass flow rate. This law can be used to measure the mass flow rate of the fluid. Compared with ultrasonic and thermal flow meters, mass flow meters achieve truly high-precision direct measurement of mass flow. When there is no relative motion between the thin-walled tube and the fluid, the vibrations of the regularly symmetrical curved tube at each point are in the same phase after the stimulated vibration. When the thin-walled tube and the fluid move relative to each other, that is, the fluid flows in the thin-walled tube, the responses of the thin-walled tube structure are different. The vibration phase at the input end will lag behind the drive phase, while the vibration phase at the output end will lead the drive phase. The difference between the sinusoidal signals on the input and output sides is proportional to the mass flow rate. In order to obtain a stable phase difference, thin-walled tubes generally have high requirements for the symmetry and consistency of their own molding.

[0003] Thin-walled tubes are mainly composed of gate type, straight tube type and U type. Gate type and U type are both bent tube configurations, and the thin-walled tubes of mass flowmeters are generally bent tube configurations. The bending process is generally to bend directly using a tube bender. During this bending process, it is easy to wrinkle the inside of the bend and break the outside, resulting in low yield and poor molding consistency. Especially when the mass flowmeter uses thin-walled tubes due to design constraints, such as thin tubes with a wall thickness of 0.1 to 0.3 mm, this bending process becomes a key factor restricting product performance.

[0004] Therefore, some studies have attempted to suppress unnecessary structural deformation during the bending process by filling the inside of thin-walled tubes with objects such as rubber and sand. For example, in the patent "A method for pushing and bending an L-shaped thin-walled aluminum alloy elbow with a small curvature radius" with application number CN201710024648.6, a low-melting-point alloy is used as a filling medium for the inner wall of the aluminum alloy tube, a protective agent is applied to the outside of the tube blank and molybdenum disulfide is applied to the inside, and a number of polyurethane cylindrical blocks and core heads are filled inside the tube blank to prevent the tube blank from breaking and wrinkling during the push-bending process. However, the materials and steps used in this type of method are cumbersome, and the thin-walled tube of the mass flowmeter is usually made of 304 or 316L stainless steel, which has a higher hardness and modulus than aluminum alloy. The filler does not match the material of the thin-walled tube and cannot truly damage the inner wall. Therefore, the above methods still cannot solve the problem of bending consistency and low yield of thin-walled stainless steel tubes. Summary of the invention

[0005] This application meets the needs of mass flow meter thin-walled tube bending and molding. In view of the manufacturing defects such as poor consistency and low yield caused by traditional bending process, the bending process is controlled by cooperating with the medium-intensive spring group, and the qualified rate of thin-walled tube products is improved. It is universal for bending thin-walled tubes of different calibers.

[0006] A method for improving the yield rate of thin-walled tube bending, comprising: first inserting a dense spring group into the thin-walled tube so that two ends of the dense spring group extend out of two ends of the thin-walled tube, and then bending the thin-walled tube; the difference between the outer diameter of the dense spring group and the inner diameter of the thin-walled tube is ≤0.2mm; the thin-walled tube and the dense spring group are both made of steel; the dense spring group is a coil spring with a uniform diameter and a helical angle within 5°; the gap width between adjacent coils of the dense spring group is 0-0.5mm.

[0007] By adopting the above technical solution, the materials of the thin-walled tube and the dense spring group are matched, and the materials and steps adopted are simple; the diameter difference and the structure of the dense spring group enable the dense spring group to have a strong supporting effect, and the dense spring group can be inserted into the thin-walled tube smoothly; the thin-walled bent tube prepared by the bending method based on the above thin-walled tube and dense spring group structure basically does not wrinkle or crack at the bending part, and the prepared thin-walled bent tube has good consistency and high yield rate.

[0008] A preferred solution of the method for improving the yield rate of thin-walled tube bending is that the wall thickness of the thin-walled tube is 0.1-0.3 mm.

[0009] By adopting the above technical solution, the wall thickness is the wall thickness of the elbow in a general Coriolis mass flowmeter, and the method is suitable for manufacturing the elbow in a Coriolis mass flowmeter with a general wall thickness.

[0010] A preferred solution of the method for improving the yield of thin-walled tube bending is that the material of the thin-walled tube is 304 stainless steel or 316L stainless steel; the material of the dense spring group is 72A carbon spring steel, 65# carbon spring steel or 304 stainless steel.

[0011] By adopting the above technical solution, 304 stainless steel or 316L stainless steel is used as the material of the thin-walled tube in a general Coriolis mass flowmeter, and the material of the dense spring group is the same as or close to that of the thin-walled tube, so that the dense spring group has an elastic modulus and hardness similar to that of the thin-walled tube, and can achieve the effect of basically not affecting the quality of the inner surface of the thin-walled tube during the bending process of the thin-walled tube, thereby reducing the extrusion damage of the inner wall of the thin-walled tube caused by this link, thereby affecting the fluid flow performance.

[0012] A preferred solution of the method for improving the yield rate of thin-walled tube bending is that the Rockwell hardness of the dense spring group minus the Rockwell hardness of the thin-walled tube=±10.

[0013] By adopting the above technical solution, the Rockwell hardness of the dense spring group and the thin-walled tube is very close or equal. Therefore, during the bending process of the thin-walled tube, the dense spring group basically does not cause extrusion damage to the inner wall of the thin-walled tube, thereby significantly improving the mass flowmeter bending tube forming consistency and yield rate.

[0014] A preferred solution of the method for improving the yield of thin-walled tube bending is that the dense spring group is a single dense spring, which runs through the thin-walled tube, and each end of the single dense spring extends out of the thin-walled tube by a length of 10 to 50 mm.

[0015] By adopting the above technical solution, a single dense spring group is easy to install, and the thin-walled tubes extending from both ends are used to facilitate the removal of the dense spring group after the thin-walled tube is bent. If the end of the dense spring group is too short, it is not conducive to clamping the end of the dense spring group, and during the bending process of the thin-walled tube, the dense spring group may shrink and drill into the thin-walled tube. If the end of the dense spring group is too long, it is not convenient to operate.

[0016] A preferred solution of the method for improving the yield of thin-walled tube bending is that the dense spring group consists of two dense springs, which are respectively inserted into the two ends of the thin-walled tube, each dense spring passes through the bending area of ​​the thin-walled tube, and the outer end of each dense spring extends out of the thin-walled tube by a length of 10 to 50 mm.

[0017] By adopting the above technical solution, when the thin-walled tube is long, a dense spring group consisting of two dense springs can be used. The outer end of each dense spring extends out of the thin-walled tube. After bending the two ends of the thin-walled tube, the outer end of each dense spring can be clamped separately, thereby clamping out each dense spring, reducing the risk of a longer single dense spring sliding a long distance in a longer thin-walled tube and damaging the inner wall of the thin-walled tube.

[0018] A preferred solution of the method for improving the yield rate of thin-walled tube bending is that the wire diameter of the dense spring group is 1 to 1.5 times the wall thickness of the thin-walled tube.

[0019] By adopting the above technical solution, the dense spring group has a good supporting effect and good bendability, and causes little damage to the inner wall of the thin-walled tube.

[0020] A preferred solution of the method for improving the yield rate of thin-walled tube bending is that the method for improving the yield rate of thin-walled tube bending includes: cleaning the dense spring assembly; Insert the cleaned dense spring group into the thin-walled tube. If there is any jamming during the insertion process, rotate the dense spring group to push the dense spring group deeper into the thin-walled tube, so that both ends of the dense spring group are finally extended out of the thin-walled tube. Put the thin-walled tube with the dense spring group inserted into the tube bending machine, keep both ends of the dense spring group extending out of the thin-walled tube, fix the thin-walled tube, and symmetrically bend both ends of the thin-walled tube to the target angle; Taking down the bent thin-walled tube, and performing heat treatment on the thin-walled tube to remove stress; The dense spring assembly in the thin-walled tube is removed.

[0021] By adopting the above technical solution, the spring is cleaned to avoid oil pollution inside the thin-walled tube, and the way of inserting the spring is conducive to the smooth passage of the spring through the thin-walled tube. The application adopts a simple method to bend the thin-walled tube, the inside of the thin-walled tube is basically not wrinkled, the outside is basically not broken, the consistency is good, and the yield rate is high.

[0022] A preferred solution of the method for improving the yield of thin-walled tube bending is that when removing the dense spring group from the thin-walled tube, a clamping tool is used to clamp the outer end of the dense spring group, and the dense spring group is pulled out of the thin-walled tube along the axial direction of the straight tube section at the end of the thin-walled tube.

[0023] By adopting the above technical solution, the dense spring group can be pulled out along the axial direction of the pipe section, and the pulling out is smooth, and the dense springs cause little damage to the inner wall of the thin-walled pipe.

[0024] A preferred solution of the method for improving the yield of thin-walled tube bending is that the heat treatment to remove stress includes heating the thin-walled tube to 550-650° C. for 1-4 hours and then cooling it to room temperature.

[0025] By adopting the above technical solution, after the heat treatment, the bending part of the thin-walled tube is shaped and is not prone to wrinkling, deformation, rupture, etc.

[0026] To summarize, the method for improving the yield of thin-walled tube bending of the present application has the following beneficial effects: the present application inserts a dense spring group into the thin-walled tube, limits the material of the dense spring group and the thin-walled tube to be the same or similar, and stipulates that the difference between the outer diameter of the spring and the inner diameter of the thin-walled tube is not greater than 0.2 mm, as well as a simple bending process, thereby improving the consistency and yield of the mass flowmeter bending forming and improving the performance of the mass flowmeter itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A method step diagram for improving the yield rate of thin-walled tube bending.

[0028] Figure 2This is a combined diagram of a single dense spring penetrating a thin-walled tube.

[0029] Figure 3 This is a calculation diagram for the length of the thin-walled tube exposed at both ends of a single dense spring.

[0030] Figure 4 To calculate the length of each dense spring when two dense springs are inserted into the two ends of a U-shaped thin-walled tube.

[0031] Figure 5 To calculate the length of each dense spring when two dense springs are inserted into the two ends of the gate-shaped thin-walled tube.

[0032] Figure numerals: 1. dense spring group; 2. thin-walled tube. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the following embodiments, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] A method for improving the yield rate of thin-walled tube bending. The bent thin-walled tube 2 can be applied to a Coriolis mass flowmeter to measure the mass flow of a fluid.

[0035] Compared with the method of directly bending the thin-walled tube 2, the method of improving the yield of thin-walled tube bending adds an auxiliary component, a dense spring group 1, which can be a single dense spring or two dense springs. When the thin-walled tube 2 is short, for example, the length is less than 200mm, the dense spring group 1 is suitable for a single dense spring, which is inserted into the thin-walled tube 2, and both ends of the single dense spring extend out of the thin-walled tube 2, and the length of each end extending can be 10~50mm, so that after bending the thin-walled tube 2, the dense spring group 1 can be pulled out by clamping the end of the dense spring group 1. When the thin-walled tube 2 is long, for example, the length is greater than 200mm, the dense spring group 1 is suitable for two dense springs, which are inserted into the two ends of the thin-walled tube 2 from both ends, and the length of each dense spring exposed from the thin-walled tube 2 is 10~50mm.

[0036] The above dense spring group 1 plays a role in supporting the thin-walled tube 2, which can reduce or avoid wrinkles on the inner side of the bend or tears on the outer side of the bend during the bending process of the thin-walled tube 2. After bending, the thin-walled tube 2 is also heat-treated to release the bending stress, so that the thin-walled tube 2 is shaped and basically no longer deformed during subsequent use.

[0037] In order to enable the addition of the dense spring group 1 to reduce the bending wrinkles and cracks of the thin-walled tube 2, and reduce the damage of the dense spring group 1 to the inner wall of the thin-walled tube 2, a preferred implementation condition is that the dense spring group 1 is a spiral spring with uniform diameters at all locations, and the thin-walled tube 2 is also a tube body with uniform inner and outer diameters at all locations. Before bending the thin-walled tube 2, the thin-walled tube 2 is generally a straight tube, and the outer diameter of the dense spring group 1 is less than 0.2 mm smaller than the inner diameter of the thin-walled tube 2. This design takes into account the strong supporting effect of the dense spring group 1 on the thin-walled tube 2 and the smoothness of insertion into the thin-walled tube 2. The material of the dense spring group 1 should be the same as or close to that of the thin-walled tube 2. For example, the material of the thin-walled tube 2 is generally 304 stainless steel or 316L stainless steel, and the material of the dense spring group 1 can be 72A carbon spring steel, 65# carbon spring steel or 304 stainless steel. The dense spring group 1 and the thin-walled tube 2 have similar Rockwell hardness and elastic modulus. Preferably, the Rockwell hardness of the dense spring group 1 - the Rockwell hardness of the thin-walled tube 2 = ±10. For example, the Rockwell hardness of the dense spring group 1 and the thin-walled tube 2 are both 92. In the process of bending the thin-walled tube 2, the dense spring group 1 does not affect the internal surface quality of the thin-walled tube 2, thereby reducing the extrusion damage of the inner wall of the thin-walled tube 2 caused by this link, thereby affecting the fluid flow performance.

[0038] The wall thickness of the thin-walled tube 2 is generally 0.1~0.3mm. The dense spring group 1 can be a uniform coil spring with a helical angle within 5°. The helical angle is the angle between the tangent of the spring coil and the cross section of the spring. The wire diameter of the dense spring group 1 is generally 0.1~0.8mm. Preferably, the wire diameter of the dense spring group 1 is 1~1.5 times the wall thickness of the thin-walled tube 2, so that the dense spring group 1 has both strong support and bendable properties. The dense spring group 1 can be a standardized spring on the market, and it should be stored in a dry environment at room temperature to avoid rust and other changes in the size and performance of the spring. Preferably, in the dense spring group 1, adjacent coils are close together, that is, the gap width between adjacent coils is 0, and the gap width can also be within 0.5mm.

[0039] The above limits the material, diameter, length and other structures of the thin-walled tube 2 and the dense spring group 1. The following specifically describes the method for improving the yield rate of thin-walled tube bending in the present application. Figure 1 The method includes the following seven steps to bend the two ends of the thin-walled tube 2 into two bending angles: 1) Dense spring group 1 (Dense spring group 1 in Figure 1 In the figure, it is briefly described as the surface purification of the spring. In order to avoid foreign matter or oil pollution on the inner wall of the thin-walled tube 2 during the bending process, so as not to increase the workload of the subsequent cleaning process, it is necessary to use reagents such as anhydrous alcohol to clean the dense spring group 1 and remove its dirt.

[0040] 2) If Figure 2, slowly place the dense spring group 1 into the linear thin-walled tube 2 (the thin-walled tube 2 is Figure 1 The wall thickness of the thin-walled tube 2 is 0.1mm~0.3mm (simply described as a straight tube or pipeline). During the operation, rapid and sharp insertion must be avoided. If there is a jam, it is allowed to go deeper by rotation. If the jam is serious, the dense spring group 1 needs to be replaced or the thin-walled tube 2 needs to be inspected to avoid damage to the thin-walled tube 2 in this link.

[0041] 3) Measure the length allowance of dense spring group 1. Dense spring group 1 can be a single dense spring, for example Figure 3 The single dense spring includes a spring segment 101 extending out of the left end of the thin-walled tube 2, the length of the spring segment 101 can be 10~50mm, a spring segment 102 located in the thin-walled tube 2, and a spring segment 103 extending out of the right end of the thin-walled tube 2, the length of the spring segment 103 can be 10~50mm.

[0042] The dense spring group 1 can also be two dense springs, which are inserted into the two ends of the thin-walled tube 2 respectively. The two dense springs do not touch each other in the thin-walled tube 2, and each dense spring should cover the bending part of the thin-walled tube 2: Figure 4 Taking the finished U-shaped thin-walled tube 2 as an example, the length of each dense spring is (L105+L104+LR×ψ+50) mm, L105 is the length of the spring segment 105, L104 is the length of the spring segment 104, ψ is the central angle of the arc between the spring segment 105 and the spring segment 104, which is not in Figure 4 In the figure, LR×ψ is the length of the arc segment between the spring segment 105 and the spring segment 104; Figure 5 Taking the finished gate-shaped thin-walled tube 2 as an example, the length of each dense spring is (L106+L107+LR1×ψ+50) mm, L106 is the length of spring segment 106, L107 is the length of spring segment 107, ψ is the central angle of the arc between spring segment 106 and spring segment 107, which is not in Figure 5 As indicated therein, LR1×ψ is the length of the arc segment between the spring segment 106 and the spring segment 107 .

[0043] After the dense spring group 1 with a certain length calculated is cut, it is inserted into the thin-walled tube 2, and the part of the dense spring group 1 extending out of the thin-walled tube 2 is measured, and its length is 10~50mm.

[0044] 4) Place the thin-walled tube 2 with the dense spring group 1 inserted into the tube bending machine. During this step, the relative positions of the dense spring group 1 and the thin-walled tube 2 should be kept basically unchanged to prevent the dense spring group 1 from slipping out of the thin-walled tube 2.

[0045] 5) After stably clamping the thin-walled tube 2 using the tooling, slowly load both ends of the thin-walled tube 2 to the bending angle.

[0046] 6) Remove the bent thin-walled tube 2, keep the relative position of the dense spring group 1 and the thin-walled tube 2 unchanged, and perform heat treatment on the thin-walled tube 2 to relieve stress. The main process of heat treatment in this link is: heat the thin-walled tube 2 to 550~650℃ for 1~4 hours, and then cool it to room temperature.

[0047] 7) Remove the dense spring group 1 to prepare the thin-walled tube 2 for subsequent processing. When removing the dense spring group 1, it needs to be removed slowly, usually with the assistance of a clamping tool, and the dense spring group 1 is pulled out along the axial direction of the straight tube section at the outer end of the thin-walled tube 2.

[0048] The bent tube was prepared by the above method, and the results are shown in Tables 1 to 4. The helical angle of the dense spring used was 3°, the coil spacing of the dense spring was 0, and the length of the thin-walled tube 2 exposed at each end of the dense spring was 50 mm.

[0049]

[0050]

[0051]

[0052] In Tables 1 to 4, good products are those with no wrinkles on the inside of the bend, no cracks on the outside, and smooth inner and outer surfaces. Defective products are those with wrinkles on the inside, cracks on the outside, or other uneven surfaces on the inside and outside.

[0053] By comparing the results of Table 1 and Table 3, and comparing the results of Table 2 and Table 4, it can be concluded that the method of improving the bending yield of thin-walled tubes in the present application has an improvement effect on thin-walled tubes of different calibers, indicating that the method is universal. The thin-walled bent tubes prepared by the present method do not wrinkle on the inside of the bend, do not crack on the outside of the bend, and have no other deformation phenomena. The surface of the bend is smooth, the molding consistency is good, and the yield can reach more than 97%.

[0054] Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for improving the yield rate of thin-walled tube bending, characterized in that: First, a dense spring group (1) is inserted into a thin-walled tube (2) so that two ends of the dense spring group (1) extend out of two ends of the thin-walled tube (2), and then the thin-walled tube (2) is bent; the difference between the outer diameter of the dense spring group (1) and the inner diameter of the thin-walled tube (2) is ≤0.2 mm; the thin-walled tube (2) and the dense spring group (1) are both made of steel; the dense spring group (1) is a uniform diameter helical spring with a helical angle within 5°; and the gap width between adjacent coils of the dense spring group (1) is 0-0.5 mm.

2. The method for improving the yield rate of thin-walled tube bending according to claim 1, characterized in that: The wall thickness of the thin-walled tube (2) is 0.1-0.3 mm.

3. The method for improving the yield rate of thin-walled tube bending according to claim 1, characterized in that: The material of the thin-walled tube (2) is 304 stainless steel or 316L stainless steel; the material of the dense spring group (1) is 72A carbon spring steel, 65# carbon spring steel or 304 stainless steel.

4. The method for improving the yield rate of thin-walled tube bending according to claim 1 or 3, characterized in that: The Rockwell hardness of the dense spring group (1) minus the Rockwell hardness of the thin-walled tube (2) = ±10.

5. The method for improving the yield rate of thin-walled tube bending according to claim 1, characterized in that: The dense spring group (1) is a single dense spring, which passes through the thin-walled tube (2), and each end of the single dense spring protrudes from the thin-walled tube (2) by a length of 10 to 50 mm.

6. The method for improving the yield rate of thin-walled tube bending according to claim 1, characterized in that: The dense spring group (1) comprises two dense springs, which are respectively inserted into the two ends of the thin-walled tube (2), each dense spring passes through the bending area of ​​the thin-walled tube (2), and the outer end of each dense spring protrudes from the thin-walled tube (2) by a length of 10 to 50 mm.

7. The method for improving the yield rate of thin-walled tube bending according to claim 1, characterized in that: The wire diameter of the dense spring group (1) is 1 to 1.5 times the wall thickness of the thin-walled tube (2).

8. The method for improving the yield rate of thin-walled tube bending according to claim 1, characterized in that: The method for improving the yield rate of thin-walled tube bending comprises: Cleaning the dense spring assembly (1); Inserting the cleaned dense spring group (1) into the thin-walled tube (2); if there is any jamming during the insertion process, rotating the dense spring group (1) to push the dense spring group (1) deeper into the thin-walled tube (2), so that both ends of the dense spring group (1) extend out of the thin-walled tube (2); Putting the thin-walled tube (2) with the dense spring group (1) inserted into the tube bending machine, keeping both ends of the dense spring group (1) extending out of the thin-walled tube (2), fixing the thin-walled tube (2), and symmetrically bending the two ends of the thin-walled tube (2) to the target angle; removing the bent thin-walled tube (2), and performing heat treatment on the thin-walled tube (2) to remove stress; The dense spring assembly (1) is removed from the thin-walled tube (2).

9. The method for improving the yield rate of thin-walled tube bending according to claim 8, characterized in that: When removing the dense spring group (1) from the thin-walled tube (2), a clamping tool is used to clamp the outer end of the dense spring group (1), and the dense spring group (1) is pulled out of the thin-walled tube (2) along the axial direction of the straight tube section at the end of the thin-walled tube (2).

10. The method for improving the yield rate of thin-walled tube bending according to claim 8, characterized in that: The heat treatment to remove stress comprises heating the thin-walled tube (2) to 550-650° C. and keeping the temperature for 1-4 hours, and then cooling to room temperature.

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