Method for internal high-pressure forming of three-way pipe fitting

Abstract

The invention provides a method for internal high-pressure forming of a three-way pipe fitting, and the method is executed through the following device which comprises a frame body, an upper mounting plate, a lower mounting plate, a left push head, a right push head and a horizontal hydraulic cylinder; the left pushing head and the right pushing head are respectively arranged on a piston rod of the left hydraulic cylinder and a piston rod of the right hydraulic cylinder; the horizontal hydraulic cylinder is arranged on the lower mounting plate in a position-adjustable mode, the axis of a piston rod of the horizontal hydraulic cylinder and the first axis are located in the same horizontal plane, the angle formed by the two axes is variable, and a pushing head is further arranged on the piston rod of the horizontal hydraulic cylinder. And the pushing head is controlled to move in the direction away from the pipe blank along the branch pipe cavity and apply pushing force to the pipe blank. According to the method provided by the invention, the forming speed of the branch pipe of the inclined three-way pipe fitting is controlled through the pushing head on the horizontal hydraulic cylinder, so that the consumption of raw materials is reduced, the labor is saved, and the rejection rate is reduced.

Description

Technical Field

[0001] This application relates to the technical field of basic non-cutting machining or treatment of metal plates, tubes, rods or profiles, and particularly relates to a method for internal high-pressure forming of three-way pipe fittings. Background Art

[0002] Internal High Pressure Forming (IHPF) is an advanced process for manufacturing pipe fittings with complex shapes and is suitable for forming pipe fittings such as tees. In the internal high-pressure forming method, high-pressure liquid is applied to the inside of the pipe, causing the pipe to expand within the mold and conform to the mold cavity, thereby forming the desired shape. This process combines the advantages of hydroforming and die forming and can manufacture three-way pipe fittings with high precision, complex geometries, no welds, and high strength.

[0003] Currently, when using existing internal high-pressure forming equipment to form inclined three-way pipe fittings, it is difficult to control the pressure. During the pressing process, it is easy for some parts of the pipe wall to become too thin, resulting in quality problems. Once the pressure is too high, the pipe blank may even explode, leading to the scrapping of the pipe blank and causing waste of materials, energy, and labor. Summary of the Invention

[0004] To at least partially solve the above problems, an embodiment of this application provides a method for internal high-pressure forming of three-way pipe fittings. This method is executed by the following device, which includes: a frame body that is respectively provided with an upper hydraulic cylinder and a lower hydraulic cylinder that are opposite up and down, and a left hydraulic cylinder and a right hydraulic cylinder that are opposite left and right; an upper mounting plate connected to the piston rod of the upper hydraulic cylinder for mounting the upper die of the three-way pipe fitting mold; a lower mounting plate arranged on the frame body and opposite to the upper mounting plate. The lower mounting plate is provided with a through hole for the piston rod of the lower hydraulic cylinder to pass through, and the lower mounting plate is used for mounting the lower die of the three-way pipe fitting mold; a left push head and a right push head are respectively arranged on the piston rods of the left hydraulic cylinder and the right hydraulic cylinder and are arranged on the same first axis; a horizontal hydraulic cylinder is adjustably arranged on the lower mounting plate. The axis of the piston rod of the horizontal hydraulic cylinder and the first axis are in the same horizontal plane and the angle formed by the two axes is variable, so that the axis of the piston rod of the horizontal hydraulic cylinder can be collinear with the axis of the branch cavity of the three-way pipe fitting mold. The piston rod of the horizontal hydraulic cylinder is provided with a push head, and the radial dimension of the push head is the same as the radial dimension of the branch cavity of the three-way pipe fitting mold. This method includes: after placing the pipe blank and closing the mold, adjusting the horizontal hydraulic cylinder so that the angle between the axis of the piston rod of the horizontal hydraulic cylinder and the first axis is the angle between the main pipe and the branch pipe of the three-way pipe fitting to be formed, controlling the push head to enter the branch cavity, and when the pipe blank expands to contact the push head under pressure increase, controlling the push head to move away from the pipe blank along the branch cavity and applying a pushing force to the pipe blank.

[0005] In some embodiments, the left pusher and the right pusher are controlled to synchronously apply an axial thrust to the tube blank and feed axially along the tube blank for feeding; after the tube blank contacts the pusher head, the axial feeding distances of the left pusher and the right pusher are controlled to be different. Among them, the axial feeding distance of the pusher head in the main tube cavity on the side where the angle formed with the branch tube cavity is an obtuse angle is M1, and the axial feeding distance of the pusher head in the main tube cavity on the side where the angle formed with the branch tube cavity is an acute angle is M2, and M1 > M2.

[0006] In some embodiments, after the tube blank contacts the pusher head, the pressure is continuously increased, and the speed at which the pusher head withdraws from the branch tube cavity is controlled to be less than or equal to the speed at which the top end of the branch tube expands along the branch tube cavity.

[0007] In some embodiments, the magnitude of the pushing force applied by the pusher head to the tube blank is collected in real time; in response to the pushing force being less than a preset threshold, the speed at which the pusher head withdraws from the branch tube cavity is reduced, and the value range of the preset threshold is 50 - 500 N.

[0008] In some embodiments, in response to the pusher head moving to a preset position, the pusher head, the left pusher, and the right pusher are controlled to stop moving, and at the same time, the pressure increase is stopped and the pressure is maintained. The preset position is related to the length of the branch tube to be formed.

[0009] In some embodiments, after maintaining the pressure for a preset time, the pusher head is controlled to move a preset distance in the direction close to the branch tube along the branch tube cavity, and the value range of the preset distance is 5 - 30 mm.

[0010] In some embodiments, before the tube blank contacts the pusher head, the internal pressure range is 50 - 100 MPa; after the tube blank contacts the pusher head, the pressure is continuously increased, and the internal pressure range is 150 - 250 MPa; when the pressure increase is stopped and the pressure is maintained, the internal pressure range is 300 - 400 MPa; after maintaining the pressure for a preset time, the pressure is reduced in stages.

[0011] In some embodiments, a first lubricant is coated on the inner wall of the main tube cavity of the mold, and a second lubricant is coated on the inner wall of the branch tube cavity of the mold and at the transition position between the branch tube cavity and the main tube cavity. The friction coefficient of the first lubricant is greater than that of the second lubricant.

[0012] The method for internal high-pressure forming of a three-way pipe fitting provided by the embodiments of the present application, with the aid of a device for internal high-pressure forming of a three-way pipe fitting, during the process of expanding and forming a branch pipe from a tube blank, the pushing head of the control device continuously applies a pushing force to the tube blank and moves along with the expansion of the branch pipe part of the tube blank, can control the forming speed of the branch pipe during the forming process of the branch pipe, effectively prevent some pipe walls from being too thin or the tube blank from exploding, reduce the occurrence of tube blank scrapping, and moreover, there is no need to additionally increase too much pipe wall thickness to prevent the tube blank from exploding, reducing waste of materials, energy, and labor. The present invention solves the problems in the traditional forming of three-way pipe fittings, such as difficult precise control of tube blank deformation, unstable forming quality, and low forming efficiency, through multi-directional collaborative forming technology and refined control. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0014] Figure 1 is a schematic structural diagram of a device for internal high-pressure forming of a three-way pipe fitting provided by the embodiments of the present application;

[0015] Figure 2 is a partial structural schematic diagram of a device for internal high-pressure forming of a three-way pipe fitting provided by the embodiments of the present application;

[0016] Figure 3 is an exploded partial structural diagram of a device for internal high-pressure forming of a three-way pipe fitting provided by the embodiments of the present application;

[0017] Figure 4 is a top view of another partial structure of a device for internal high-pressure forming of a three-way pipe fitting provided by the embodiments of the present application;

[0018] Figure 5 is a schematic structural diagram of a lower mounting plate with a vertical plate installed provided by the embodiments of the present application;

[0019] Figure 6 is a schematic structural diagram of a vertical plate provided by the embodiments of the present application;

[0020] Figure 7 is a schematic structural diagram of a fixing block provided by the embodiments of the present application;

[0021] Figure 8 is a schematic structural diagram of an upper mounting plate with an upper die installed provided by the embodiments of the present application.

[0022] The reference numerals are as follows:

[0023] 10. Frame body; 11. Upper hydraulic cylinder; 12. Lower hydraulic cylinder; 13. Left hydraulic cylinder; 14. Right hydraulic cylinder; 15. Horizontal hydraulic cylinder; 151. Piston rod of the horizontal hydraulic cylinder; 152. End cover; 21. Upper mounting plate; 211. First limiting groove; 212. Second limiting groove; 213. Third limiting groove; 22. Lower mounting plate; 221. First mounting groove; 222. Second mounting groove; 223. Third mounting groove; 224. Through hole; 231. Mounting hole; 232. Insertion part; 233. Clamping groove; 234. Limiting part; 235. Limiting pad; 23. Vertical plate; 24. Fixed block; 241. First end; 242. Second end; 2421. Protrusion; 243. Through hole; 25. Bolt; 31. Left pushing head; 32. Right pushing head; 33. Top pushing head; 41. Upper die; 42. Lower die; 43. Main pipe cavity; 44. Branch pipe cavity.

[0024] It should be understood that the dimensions of the various parts shown in the drawings are not drawn in accordance with actual proportional relationships. In addition, the same or similar reference numerals represent the same or similar components. Detailed implementation manners

[0025] The technical solutions of the preferred embodiments of the present application will be clearly and completely described below in conjunction with the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection required by the present application.

[0026] The "first", "second" and similar terms used in the present application do not indicate any order, quantity or importance, but are only used to distinguish different parts. The terms such as "including" or "comprising" mean that the elements before this word cover the elements listed after this word, and do not exclude the possibility of also covering other elements. The terms such as "upper", "lower", "left" and "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0027] When the inventors of the present application used the existing internal high-pressure forming device to produce inclined tee pipe fittings (such as the included angles between the main pipe and the branch pipe are 30°, 45°, 60°, etc.), it was found that it was difficult to control the forming speed of the branch pipe. If the forming speed was too fast, on the one hand, part of the pipe wall was too thin, which did not meet the quality requirements, and even the pipe blank exploded; on the other hand, it was also difficult to control the length of the branch pipe, resulting in material waste and increased labor costs.

[0028] In order to obtain an inclined tee fitting that meets the quality requirements, the inventor has tried to avoid the above situation by reducing the pressure used during forming, increasing the thickness of the tube blank, and other means. However, reducing the pressure used during forming will lead to an increase in the number of forming times, and at the same time, the corresponding number of manual processing times will also increase accordingly; increasing the thickness of the tube blank will lead to an increase in the amount of raw materials used, and after forming, machining is still required to obtain fittings that meet the thickness requirements and length requirements. Therefore, the above methods will all result in cumbersome operations, more material waste, and higher labor costs. Moreover, even if the above methods are adopted, there is still a high rejection rate.

[0029] To at least partially solve the above problems, the inventor of the present application has obtained the present invention through continuous attempts and improvements.

[0030] An embodiment of the present application provides a method for internal high-pressure forming of a tee fitting. This method is executed by the following device. Please combine Figure 1 , and this device includes: a frame body, which is respectively provided with an upper hydraulic cylinder and a lower hydraulic cylinder that are opposite up and down, and a left hydraulic cylinder and a right hydraulic cylinder that are opposite left and right; an upper mounting plate, which is connected to the piston rod of the upper hydraulic cylinder and is used to mount the upper die of the tee fitting mold; a lower mounting plate, which is arranged on the frame body and is opposite to the upper mounting plate. The lower mounting plate is provided with a through hole for the piston rod of the lower hydraulic cylinder to pass through, and the lower mounting plate is used to mount the lower die of the tee fitting mold; a left push head and a right push head, which are respectively arranged on the piston rods of the left hydraulic cylinder and the right hydraulic cylinder and are arranged on the same first axis; a horizontal hydraulic cylinder, which is adjustably arranged on the lower mounting plate. The axis of the piston rod of the horizontal hydraulic cylinder and the first axis are located in the same horizontal plane and the angle formed by the two axes is variable, so that the axis of the piston rod of the horizontal hydraulic cylinder can be collinear with the axis of the branch cavity of the tee fitting mold. The piston rod of the horizontal hydraulic cylinder is provided with a pushing head, and the radial dimension of the pushing head is the same as the radial dimension of the branch cavity of the tee fitting mold.

[0031] This method includes: after putting in the tube blank and closing the mold, adjust the horizontal hydraulic cylinder so that the angle between the axis of the piston rod of the horizontal hydraulic cylinder and the first axis is the angle between the main pipe and the branch pipe of the tee fitting to be formed. Control the pushing head to enter the branch cavity. When the pressure is increased to make the tube blank expand until it contacts the pushing head, control the pushing head to move away from the tube blank along the branch cavity and apply a pushing force to the tube blank.

[0032] Specifically, the selected material for the tube blank can be aluminum alloy, stainless steel, titanium alloy or high-strength steel, which should have good plasticity (for example, elongation ≥ 20%) and tensile strength. Cut the tube to the designed length, and the end face should be flat (for example, the perpendicularity error is usually ≤ 0.1 mm) to obtain the tube blank. When pushing the inclined tee by the internal high-pressure process, due to the asymmetric structure of the inclined tee, the tube blank can be preformed first to adapt to the die space and facilitate subsequent internal high-pressure forming. Place the tube blank into the tee fitting die and close the die. When making the inclined tee, the axis of the main pipe cavity of the tee fitting die forms an angle less than 90° with the axis of the branch pipe cavity, for example, it can be 30°, 45°, 60°, etc. Control the left pusher and the right pusher to enter the main pipe cavity and respectively seal the openings at both ends of the tube blank. Control the pusher to enter the branch pipe cavity, fill the inner cavity of the tube blank with a liquid medium and increase the pressure, so that the tube wall corresponding to the branch pipe cavity of the tube blank expands into the branch pipe cavity and gradually forms the branch pipe. When the tube blank does not contact the pusher, the pusher can remain stationary; once it is detected that the tube blank contacts the pusher, control the pusher to move away from the tube blank along the branch pipe cavity and apply a pushing force to the tube blank.

[0033] The method for internal high-pressure forming of tee fittings provided by the embodiments of the present application, with the aid of the device for internal high-pressure forming of tee fittings, during the process of the tube blank expanding to form the branch pipe, the pusher of the control device continuously applies a pushing force to the tube blank and moves together with the expansion of the branch pipe part of the tube blank, which can control the forming speed of the branch pipe during the forming process of the branch pipe, effectively prevent some tube walls from being too thin or the tube blank from exploding, reduce the occurrence of tube blank scrapping, and moreover, there is no need to additionally increase the tube wall thickness excessively to prevent the tube blank from exploding, reducing the waste of materials, energy and labor.

[0034] In some embodiments, the left pusher and the right pusher are controlled to synchronously apply an axial thrust to the tube blank and feed axially along the tube blank to replenish materials. After the tube blank contacts the pusher head, the axial feeding distances of the left pusher and the right pusher are controlled to be different. Among them, the axial feeding distance of the pusher head in the main pipe cavity on the side where the angle formed with the branch pipe cavity is an obtuse angle is M1, and the axial feeding distance of the pusher head in the main pipe cavity on the side where the angle formed with the branch pipe cavity is an acute angle is M2, and M1 > M2. It can be understood that in the inclined tee mold, taking the intersection point of the branch pipe cavity and the main pipe cavity as the demarcation point, the angle formed between the main pipe cavity on one side of the demarcation point and the branch pipe cavity can be an obtuse angle, and the angle formed between the main pipe cavity on the other side of the demarcation point and the branch pipe cavity can be an acute angle. In this embodiment, by applying an axial thrust and feeding axially along the tube blank to replenish materials, the material loss during the forming of the branch pipe of the tube blank is compensated. Before the tube blank contacts the pusher head, the axial feeding distances of the left pusher and the right pusher can be the same or different; after the tube blank contacts the pusher head, due to the asymmetric characteristics of the inclined tee, the left pusher and the right pusher can be fed differentially. On the side where the branch pipe and the main pipe form an obtuse angle, a larger amount of deformation needs to be generated. Therefore, in this embodiment, a larger axial feeding distance is provided on this side to prevent the wall thickness of this side from being too thin and causing quality problems. Specifically, according to the forming characteristics of the inclined tee pipe fitting, the pusher head always supports the top of the branch pipe during forming, and cooperates with the asymmetric feeding of the left and right filling to realize the gradual bulging of the branch pipe, avoiding the excessive thinning of the middle large arc during the bulging of the branch pipe and resulting in cracking.

[0035] In some embodiments, after the tube blank contacts the pusher head, the pressure is continuously increased, and the speed at which the pusher head withdraws from the branch pipe cavity is controlled to be less than or equal to the speed at which the top end of the branch pipe expands along the branch pipe cavity. In this embodiment, continuously increasing the pressure after the tube blank contacts the pusher head can increase the forming speed of the branch pipe and prevent the tube blank from exploding due to premature pressurization; controlling the movement speed of the pusher head can ensure that the pusher head always contacts the branch pipe and continuously applies a pushing force to the branch pipe. Exemplarily, the speed at which the pusher head withdraws from the branch pipe cavity can be 0.1 - 0.3 mm / s.

[0036] In some embodiments, the magnitude of the pushing force applied by the pusher head to the tube blank is collected in real time; in response to the pushing force being less than a preset threshold, the speed at which the pusher head withdraws from the branch pipe cavity is reduced. Preferably, the value range of the preset threshold is 50 - 500 N. In this embodiment, a force sensor can be set on the horizontal hydraulic cylinder to collect the pushing force in real time. By monitoring the magnitude of the pushing force, the relationship between the movement speed of the pusher head and the expansion speed of the branch pipe is analyzed in real time, so as to finely control the movement of the pusher head, prevent the pusher head from detaching from the tube blank, and cause the forming speed of the tube blank to get out of control without the pushing force, resulting in local wall thickness being too thin and generating quality defects.

[0037] In some embodiments, in response to the pushing head moving to a preset position, the pushing head, the left pushing head, and the right pushing head are controlled to stop moving. Meanwhile, the pressure boosting is stopped and the pressure is maintained. The preset position is related to the length of the branch pipe to be formed. In this embodiment, the preset position is determined according to the designed length of the branch pipe. For example, the distance between adjacent preset positions and the distance between the preset position and the initial position of the pushing head can both be 1 / N of the length of the branch pipe, where N is an integer. Alternatively, the preset position can be multiple position points sequentially marked on the expansion path during the process of the branch pipe expanding to the length of the branch pipe. When the pushing head moves to the preset position, it stops moving to ensure that a branch pipe with the designed length is obtained. At this time, the pressure boosting is stopped and the pressure is maintained. The internal pressure reaches the maximum value. The left pushing head and the right pushing head also stop the axial feeding and remain stationary, only maintaining the axial seal. The tube blank expands under the action of the internal pressure, fully adheres to the mold, and eliminates local depressions or wrinkles.

[0038] In some embodiments, after maintaining the pressure for a preset time, the pushing head is controlled to move a preset distance along the cavity of the branch pipe in the direction close to the branch pipe. The value range of the preset distance is 5 - 30 mm. In this embodiment, after the pressure maintaining ends, under the condition that the tube blank is under pressure, the pushing head can perform reverse pushing to reduce the fillet of the expanded branch pipe, increase the length of the effective straight section of the branch pipe, effectively improve the material utilization rate and reduce the difficulty of bulging, and reduce the material usage length of the tube blank. When forming a partial angle tee pipe fitting, the end of the pushing head used to contact the tube blank can be formed into a stepped shape, so as to directly punch holes under pressure during reverse pushing, cut off the end of the branch pipe, and improve the working efficiency.

[0039] In some embodiments, before the tube blank contacts the pushing head, the internal pressure range is 50 - 100 MPa; after the tube blank contacts the pushing head, the pressure is continuously boosted, and the internal pressure range is 150 - 250 MPa; when the pressure boosting is stopped and the pressure is maintained, the internal pressure range is 300 - 400 MPa; after maintaining the pressure for a preset time, the pressure is reduced in stages to prevent the springback amount of the tube blank from exceeding the standard. Due to the asymmetric structure of the angle tee pipe fitting, during forming, the device needs to push and form a single tube blank multiple times to obtain the tee pipe fitting. After each push and form, the tube blank is heat-treated to eliminate stress. In this embodiment, according to the positional relationship between the tube blank and the pushing head and the forming stage, the pressure is boosted in stages, so as to reach a higher internal pressure value, which can improve the amount of deformation in a single push while ensuring the product quality, thereby reducing the number of forming times and improving the forming efficiency. Specifically, in the actual production process, when forming an angle tee pipe fitting in a device without a pushing head, the internal pressure range used is usually 50 - 100 MPa, and usually 11 times of push and form and corresponding heat treatments are required; when forming the same angle tee pipe fitting in the device with a pushing head provided by the embodiments of the present application, only 5 - 6 times of push and form and corresponding heat treatments are required, greatly reducing the costs of heat treatment and pushing.

[0040] In some embodiments, a first lubricant is applied to the inner wall of the main cavity of the mold, and a second lubricant is applied to the inner wall of the branch cavity of the mold and the transition position between the branch cavity and the main cavity, and the friction coefficient of the first lubricant is greater than the friction coefficient of the second lubricant. It can be understood that when forming an oblique tee, it is usually necessary to apply lubricants to the main cavity and the branch cavity of the mold to facilitate the flow of the material of the tube blank. However, since the material flow direction of the tube blank is from the main cavity to the branch cavity as a whole, this will bring part of the lubricant in the main cavity into the branch cavity, resulting in too low friction coefficient of the inner wall of the branch cavity, while too high friction coefficient of the inner wall of the main cavity, thereby generating a large friction coefficient gradient at the junction of the main cavity and the branch cavity, resulting in the flow path of the tube blank material deviating from the ideal direction when it flows here, causing the pipe fitting to have corrugated or spiral surface defects, and the material replenishment in the main area is blocked, while the material flow in the branch area is too fast, which is also easy to cause excessive stretching and thinning of the tube wall, resulting in quality defects. In this embodiment, this arrangement makes the main pipe cavity have a relatively large friction coefficient. After the lubricant is reduced, the friction coefficient increases less while ensuring the lubrication effect. The branch pipe cavity is mixed with the lubricant with a large friction coefficient in the main pipe cavity. While ensuring the lubrication effect, the friction coefficient decreases less, thereby reducing the friction coefficient gradient of the main pipe cavity area and the branch pipe cavity area, reducing the occurrence of corrugated or spiral surface defects, and preventing the occurrence of quality defects caused by excessive thinning of the pipe wall. In some embodiments, the first lubricant is molybdenum disulfide and the second lubricant is graphene. The friction coefficient of molybdenum disulfide ranges from 0.08 to 0.12, and the friction coefficient of graphene ranges from 0.05 to 0.08. The difference between the two friction coefficients is small, and a smaller friction coefficient gradient can be formed after the lubricant is transferred, reducing the occurrence of product surface defects and quality defects.

[0041] The various technical features of the present invention (such as multi-directional hydraulic cylinders, dynamically adjusted horizontal hydraulic cylinders, dual lubricant systems, staged pressurization and pressure maintenance, etc.) cooperate with each other to form a complete molding process. There is a clear synergy between these features, which jointly improves the molding quality and efficiency. The invention not only solves a single technical problem, but also achieves high efficiency, stability and high quality of the molding process through overall optimization.

[0042] The following is a more comprehensive description of the device for high pressure internal forming of a three-way pipe provided in the embodiments of the present application.

[0043] See also Figure 1 to Figure 8 The device includes a frame 10, an upper mounting plate 21, a lower mounting plate 22, a left push head 31, a right push head 32 and a horizontal hydraulic cylinder 15.

[0044] Upper hydraulic cylinders 11, lower hydraulic cylinders 12, left hydraulic cylinders 13, and right hydraulic cylinders 14 are respectively arranged on the upper, lower, left, and right of the frame body 10. The upper hydraulic cylinders 11 and the lower hydraulic cylinders 12 are arranged oppositely, and the left hydraulic cylinders 13 and the right hydraulic cylinders 14 are arranged oppositely. The upper mounting plate 21 is connected to the piston rod of the upper hydraulic cylinder 11, and the upper mounting plate 21 is used to mount the upper die 41 of the three-way pipe fitting mold; the lower mounting plate 22 is arranged on the frame body 10 and is arranged oppositely to the upper mounting plate 21. The lower mounting plate 22 is provided with a through hole 224 for the piston rod of the lower hydraulic cylinder 12 to pass through, and the lower mounting plate 22 is used to mount the lower die 42 of the three-way pipe fitting mold; the left push head 31 and the right push head 32 are respectively arranged on the piston rods of the left hydraulic cylinder 13 and the right hydraulic cylinder 14. The left push head 31 and the right push head 32 are arranged on the same axis. For the convenience of description, this axis is hereinafter referred to as the first axis; the horizontal hydraulic cylinder 15 is arranged on the lower mounting plate 22 with adjustable position. The axis of the piston rod 151 of the horizontal hydraulic cylinder is in the same horizontal plane as the first axis and the included angle between the two axes is variable, so that the axis of the piston rod 151 of the horizontal hydraulic cylinder can be collinear with the axis of the branch cavity 44 of the three-way pipe fitting mold. A push head 33 is also arranged on the piston rod 151 of the horizontal hydraulic cylinder. The radial dimension of the push head 33 is the same as the radial dimension of the branch cavity 44 of the three-way pipe fitting mold.

[0045] Specifically, please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 . The frame body 10 can be formed by welding a plurality of metal plates. The frame body 10 can be a cuboid. An open space can be formed in the middle of the frame body 10 for installing other components. The three-way pipe fitting can also be subjected to internal high-pressure forming here. The extending directions of the upper hydraulic cylinders 11, the lower hydraulic cylinders 12, the left hydraulic cylinders 13, the right hydraulic cylinders 14, and the piston rod 151 of the horizontal hydraulic cylinder can all face this open space.

[0046] The upper hydraulic cylinder 11 can be used to drive the upper die 41 to move, change the distance between the upper die 41 and the lower die 42, so as to realize mold closing and mold opening. The upper hydraulic cylinder 11 can also provide the clamping force between the upper die 41 and the lower die 42 during mold closing. The upper hydraulic cylinder 11 can have a larger size than the lower hydraulic cylinder 12 and can provide a greater output force.

[0047] The lower hydraulic cylinder 12 can be disposed relative to the upper hydraulic cylinder 11 and below the upper hydraulic cylinder 11. The lower hydraulic cylinder 12 can have a size and output force smaller than those of the upper hydraulic cylinder 11. When forming a straight three-way pipe fitting, the piston rod of the lower hydraulic cylinder 12 can pass through the through hole 224 of the lower mounting plate 22 and enter the branch cavity 44 of the straight three-way pipe fitting mold, and abut against the side wall of the pipe blank. When forming a straight three-way pipe fitting, the piston rod of the lower hydraulic cylinder 12 can gradually retract as the branch of the straight three-way pipe bulges, so as to control the forming speed of the branch of the straight three-way pipe. At the same time, when demolding, the piston rod of the lower hydraulic cylinder 12 can eject the straight three-way pipe by acting on the branch of the straight three-way pipe. At this time, the upper and lower dies 42 of the straight three-way pipe fitting mold can be of an asymmetric structure, and the branch cavity 44 of the straight three-way pipe fitting mold can be arranged at the bottom of the lower die 42, and the upper die 41 does not have the branch cavity 44.

[0048] In this embodiment, the three-way pipe fitting mold can include an upper die 41 and a lower die 42, and the upper die 41 and the lower die 42 can have a mirror-symmetrical structure or a non-mirror-symmetrical structure. The three-way pipe fitting mold can include a straight three-way pipe fitting mold and an inclined three-way pipe fitting mold. In the straight three-way pipe fitting mold, the angle formed by the axes of the main pipe cavity 43 and the branch cavity 44 is 90°. In the inclined three-way pipe fitting mold, the angle formed by the axes of the main pipe cavity 43 and the branch cavity 44 can be, for example, 30°, 45°, 60°, etc. In this embodiment, the inclined three-way pipe fitting mold can have an upper die 41 and a lower die 42 with a mirror-symmetrical structure, and the main pipe cavity 43 and the branch cavity 44 are simultaneously formed by the upper die 41 and the lower die 42. Compared with the mold in which the branch cavity 44 is formed by a separate lower die 42, this mold can facilitate the demolding of the inclined three-way pipe fitting after forming. In the actual production process, both the upper die 41 and the lower die 42 are in a horizontal state, and the branch cavity 44 can also be located in the horizontal plane.

[0049] A left push head 31 is installed on the piston rod of the left hydraulic cylinder 13, and a right push head 32 is installed on the piston rod of the right hydraulic cylinder 14. When forming a three-way pipe fitting, the left push head 31 and the right push head 32 enter the main pipe cavity 43 of the three-way pipe fitting mold and are hermetically connected to both ends of the pipe blank. The left hydraulic cylinder 13 and the right hydraulic cylinder 14 can drive the left push head 31 and the right push head 32 to move in the main pipe cavity 43. The pipe blank can be filled with a liquid medium, and the liquid medium can be pressurized to generate an internal high pressure, so as to push the side wall of the pipe blank at the entrance of the branch cavity 44 into the branch cavity 44 and expand into a branch. The left push head 31 and the right push head 32 can be arranged in a double-step structure in the sealing structure, that is, the ends of the left push head 31 and the right push head 32 for contacting the pipe blank can be formed by connecting a plurality of coaxial cylinders with gradually decreasing diameters. The adjacent two cylinders form a step surface due to the diameter difference, which is used for sealing with the end of the pipe blank. Specifically, the pipe blank is locally extruded by the step to realize reliable sealing by using the plastic deformation in the thickness direction of the pipe blank.

[0050] The horizontal hydraulic cylinder 15 is disposed on the lower mounting plate 22 in a position-adjustable manner. In this embodiment, the manner of achieving position adjustment for the horizontal hydraulic cylinder 15 is not limited. Exemplarily, the horizontal hydraulic cylinder 15 can be disposed on a slide rail fixedly connected to the frame body 10, thereby achieving position adjustment. At the same time, the horizontal hydraulic cylinder 15 can also be swingably connected to the slide rail in the horizontal plane, thereby achieving angle adjustment of the piston rod of the horizontal hydraulic cylinder 15. The axis of the piston rod 151 of the horizontal hydraulic cylinder is in the same horizontal plane as the axes of the left push head 31 and the right push head 32, and the angle formed by the two axes (i.e., the axis of the piston rod 151 of the horizontal hydraulic cylinder and the common axis of the left push head 31 and the right push head 32) is variable, so that the axis of the piston rod 151 of the horizontal hydraulic cylinder can be collinear with the axis of the branch cavity 44 of the three-way pipe fitting mold. In this embodiment, this setting manner can enable the push head 33 disposed on the piston rod 151 of the horizontal hydraulic cylinder to adapt to various three-way pipe fitting molds for forming branches with different angles, and achieve control of the forming speed of the branch.

[0051] The radial dimension of the push head 33 is the same as the radial dimension of the branch cavity 44 of the three-way pipe fitting mold, which enables the push head 33 to enter the branch cavity 44 and move along the branch cavity 44. In this embodiment, the push head 33 can be cylindrical. In some embodiments, one end of the push head 33 away from the horizontal hydraulic cylinder 15 can form an inclined surface, and the inclination angle of the inclined surface can correspond to the included angle between the main pipe and the branch pipe of the three-way pipe fitting. In this way, the push head 33 can be more closely attached to the side wall of the pipe blank, and achieve control of the forming rate at the initial stage of branch forming. Exemplarily, when the included angle between the main pipe and the branch pipe is 60°, the included angle between the inclined surface and the axis of the branch cavity 44 can be 60°. In some embodiments, the end of the push head for contacting the pipe blank can form a stepped shape to directly punch a hole in the end of the branch under pressure and cut off the top end of the branch, improving work efficiency. In some embodiments, the push head 33 can be detachably connected to the piston rod 151 of the horizontal hydraulic cylinder. This setting manner can achieve matching of molds with different diameters of the branch cavity 44 by replacing the push head 33 with different radial dimensions. Exemplarily, the push head 33 and the piston rod 151 of the horizontal hydraulic cylinder can be detachably connected by bolt connection. Preferably, when the push head 33 is fixed to the horizontal hydraulic cylinder 15 by bolts, the bolts can be located on the side surface of the push head 33, so that the end surface of the push head 33 for contacting the pipe blank is smoother, preventing the uneven end surface of the push head 33 from affecting the control of the branch forming rate.

[0052] The device for internal high pressure forming of three-way pipe fittings provided in the embodiment of the present application is provided with a horizontal hydraulic cylinder 15 with adjustable position. The push head 33 on the piston rod 151 of the horizontal hydraulic cylinder can enter the branch pipe cavity 44 of the three-way pipe fitting mold of various angles when the three-way branch pipe is formed, and interfere with the side wall of the pipe blank used for forming the three-way pipe fitting, so as to control the branch pipe forming speed of the three-way pipe fittings of various angles such as the inclined three-way pipe fitting, so that there is no need to reserve a large thickness of the pipe blank in advance, which reduces the amount of raw materials used, reduces the workload of subsequent machining, saves labor, and reduces the scrap rate. In addition, due to the use of the horizontal hydraulic cylinder 15 and the push head 33, a higher pressure can be used for internal high pressure forming when forming the inclined tee, which reduces the number of forming times and further reduces labor costs and energy consumption costs. In addition, due to the presence of the push head 33, the shape and length of the end of the inclined three-way branch pipe can be controlled, which reduces the cutting length of the end of the inclined three-way branch pipe, further reducing material consumption and labor costs. The device for internal high pressure forming of three-way pipe fittings provided in the embodiment of the present application can achieve the forming of straight three-way pipe fittings and oblique three-way pipe fittings using a single device by increasing the functionality of the equipment at low equipment cost (without increasing the number of internal high pressure forming equipment).

[0053] See also Figure 5 as well as Figure 6 In some embodiments, the device for high pressure forming of three-way pipe fittings further comprises a vertical plate 23, the vertical plate 23 is vertically arranged on the lower mounting plate 22, the horizontal hydraulic cylinder 15 is arranged on the vertical plate 23, and the axis of the piston rod 151 of the horizontal hydraulic cylinder is perpendicular to the vertical plate 23. In this embodiment, the connection between the horizontal hydraulic cylinder 15 and the lower mounting plate 22 is realized by the vertical plate 23, and the horizontal hydraulic cylinder 15 and the lower mounting plate 22 can be separated in the height direction, thereby compensating the thickness of the lower mold 42, so that the piston rod 151 of the horizontal hydraulic cylinder can enter the branch pipe cavity 44 of the mold, and this structure is simple and reliable. Preferably, the vertical plate 23 is detachably connected to the lower mounting plate 22. In this arrangement, when producing some straight three-way pipe fittings, the vertical plate 23 with the horizontal hydraulic cylinder 15 can be disassembled as a whole to facilitate the installation of the mold in which the branch pipe cavity 44 is arranged in the lower mold 42.

[0054] In some embodiments, the lower mounting plate 22 is provided with a mounting groove, and the extending direction of the mounting groove forms an angle with the axes of the left pushing head 31 and the right pushing head 32, which is determined based on the angle between the main pipe and the branch pipe of the three-way pipe fitting; the bottom end of the vertical plate 23 forms a plug-in portion 232, and the plug-in portion 232 is plugged into the mounting groove. Exemplarily, the angle formed by the extending direction of the mounting groove and the common axis of the left pushing head 31 and the right pushing head 32 can be 30° or 45°, corresponding to the three-way pipe fittings with the angles between the main pipe and the branch pipe being 60° and 45° respectively. In this embodiment, the vertical plate 23 is plugged into the mounting groove, and the mounting groove can define the angle of the vertical plate 23 to adapt to the extending direction of the branch pipe cavity 44 of the corresponding three-way pipe fitting mold. The vertical plate 23 is installed in the mounting groove by plugging, with a simple structure and easy disassembly.

[0055] In some embodiments, the mounting groove includes a first mounting groove 221, a second mounting groove 222, and a third mounting groove 223; the angle formed by the extending direction of the first mounting groove 221 and the first axis is 45°; the angle formed by the extending direction of the second mounting groove 222 and the first axis is 30°; the extending direction of the third mounting groove 223 is parallel to the first axis. In this embodiment, the first mounting groove 221, the second mounting groove 222, and the third mounting groove 223 are provided on the lower mounting plate 22, making full use of the space of the lower mounting plate 22. The above angles can cover the mainstream 45° and 60° inclined three-way pipe fitting products, and at the same time take into account some straight three-way products, increasing the versatility of the device. It can be understood that in other embodiments, mounting grooves with other angles can be provided.

[0056] Please refer to Figure 7 , in some embodiments, the device for internal high-pressure forming of three-way pipe fittings further includes a plurality of fixing blocks 24. The plurality of fixing blocks 24 are arranged on the lower mounting plate 22 and are evenly distributed on both sides of the mounting groove; clamping grooves 233 are provided at positions corresponding to the fixing blocks 24 on both sides of the plug-in portion 232 of the vertical plate 23, and the first end portion 241 of the fixing block 24 is located in the clamping groove 233 to limit the plug-in portion 232. In this embodiment, the vertical plate 23 is fixed by the cooperation of the fixing blocks 24 and the clamping grooves 233, further ensuring the stability of the vertical plate 23, and at the same time facilitating the disassembly and installation of the vertical plate 23; in addition, by using the fixing blocks 24 for limiting, the structure of the lower mounting plate 22 can be simplified, and only the mounting groove and the screw holes need to be provided on the lower mounting plate 22, without making excessive adjustments to the structure of the lower mounting plate 22.

[0057] In some embodiments, a plurality of screw holes are formed on both sides of the mounting groove, and the fixing block 24 is fixed to the lower mounting plate 22 by bolts 25; a protrusion 2421 is formed at the bottom of the second end 242 of the fixing block 24 opposite to the first end 241, and the protrusion 2421 abuts against the lower mounting plate 22. When the bolt 25 passes through the fixing block 24 and fixes the fixing block 24 at the screw hole position of the lower mounting plate 22, the bolt 25 is located between the first end 241 and the second end 242. A through hole 243 may be provided in the middle of the fixing block 24. When the insertion portion 232 is inserted into the mounting groove, the clamping groove 233 may be slightly higher than the surface of the lower mounting plate 22. In this embodiment, when the vertical plate 23 is fixed by the fixing block 24, the protrusion 2421 can serve as a fulcrum. The bolt 25 passes through the through hole 243 and is located in the middle of the fixing block 24. The nut exerts a downward force on the fixing block 24, generating a lever effect, so that the first end 241 of the fixing block 24 generates a force to press down the side wall of the clamping groove 233, and the vertical plate 23 can be more reliably fixed to the lower mounting plate 22.

[0058] In some embodiments, the length of the mounting groove is greater than the length of the insertion portion 232, the number of screw holes is greater than the number of fixing blocks 24, and the plurality of screw holes are evenly distributed on both sides of the mounting groove, and the distance between adjacent two screw holes is equal. In this embodiment, through the above structure, the vertical plate 23 can be fixed at different positions in the extending direction of the mounting groove, realizing fine adjustment of the position of the vertical plate 23 in the extending direction of the mounting groove, so as to adapt to more different three-way molds. In this embodiment, the screw holes can be divided into two rows, and the two rows of screw holes are respectively located on both sides of the mounting groove. In each row of screw holes, the distance between adjacent two screw holes is equal, and the distance of one row of screw holes is equal to the distance of the other row of screw holes. With this setting method, when using different three-way pipe fitting molds, the position of the vertical plate 23 installation can be determined by counting the number of screw holes, and the operation is simple.

[0059] In some embodiments, a mounting hole 231 is formed on the vertical plate 23, and the diameter of the mounting hole 231 is the same as the diameter of the cylinder barrel of the horizontal hydraulic cylinder 15. The cylinder barrel is sleeved in the mounting hole 231, and an end cover 152 with a diameter larger than that of the cylinder barrel is provided at one end of the cylinder barrel close to the pushing head 33. The end cover 152 is fixedly connected to the vertical plate 23 and is located on the side of the vertical plate 23 close to the pushing head 33. It can be understood that during the working process of the horizontal hydraulic cylinder 15, it will be subjected to the reaction force of the tube blank. To ensure the reliable fixation of the horizontal hydraulic cylinder 15, in this embodiment, by providing the end cover 152, the diameter of the end cover 152 is larger than that of the cylinder barrel and is located on the side of the vertical plate 23 close to the pushing head 33. When the tube blank exerts a reaction force on the horizontal hydraulic cylinder 15, the force will be transmitted to the vertical plate 23 through the outer edge of the end cover 152, thus avoiding the force on the bolt 25 for fixing the horizontal hydraulic cylinder 15 and realizing the reliable fixation of the horizontal hydraulic cylinder 15.

[0060] In some embodiments, a limiting portion 234 is formed at the top end of the vertical plate 23; a limiting groove is provided at a position corresponding to the limiting portion 234 on the upper mounting plate 21. When the three-way pipe fitting mold is closed, the distance between the upper mounting plate 21 and the lower mounting plate 22 is less than the height of the vertical plate 23. The upper mounting plate 21 and the lower mounting plate 22 can be arranged in parallel and have the same or similar sizes. In this embodiment, through this setting method, when the three-way pipe fitting mold is closed, the top end of the vertical plate 23 can enter the limiting groove. At this time, in the extending direction of the plane where the upper mounting plate 21 and the lower mounting plate 22 are located, the bottom end of the vertical plate 23 is limited by the mounting groove of the lower mounting plate 22, and the top end of the vertical plate 23 is limited by the limiting groove of the upper mounting plate 21. The vertical plate 23 can be supported more reliably and evenly, reducing the risk of the vertical plate 23 breaking due to excessive reaction force. Exemplarily, a first limiting groove 211 can be provided at a position corresponding to the first mounting groove 221 of the upper mounting plate 21 and the lower mounting plate 22, a second limiting groove 212 can be provided at a position corresponding to the second mounting groove 222 of the upper mounting plate 21 and the lower mounting plate 22, and a third limiting groove 213 can be provided at a position corresponding to the third mounting groove 223 of the upper mounting plate 21 and the lower mounting plate 22.

[0061] In some embodiments, a plurality of limiting pads 235 are provided on both sides of the limiting portion 234, and the limiting pads 235 are detachably provided on the limiting portion 234. In this embodiment, by providing the limiting pads 235 on both sides of the limiting portion 234, it is possible to prevent the top end of the vertical plate 23 from directly contacting the limiting groove of the upper mounting plate 21, thereby reducing the wear of the top end of the vertical plate 23 after multiple mold closing and opening, and increasing the service life of the vertical plate 23. The limiting pads 235 are detachably provided on the limiting portion 234. When the limiting pads 235 are severely worn, it is convenient to remove the limiting pads 235 and replace them with new ones, preventing the situation of poor limiting effect due to wear of the limiting pads 235 and tilting of the vertical plate 23, and preventing damage to the three-way pipe fitting mold, the horizontal hydraulic cylinder 15 or the vertical plate 23.

[0062] Embodiment 1

[0063] Obtain stainless steel pipes, cut the pipes to 50 cm, with the end face perpendicularity error ≤ 0.1 mm, to form pipe blanks. The included angle between the axes of the main pipe cavity and the branch pipe cavity of the mold is 45°. Pretreat the pipe blanks to adapt to the mold space, and add lubricant molybdenum disulfide to the inner wall of the mold cavity. Figure 1Internal high-pressure forming is carried out in the shown device. The preformed tube blank is placed into the lower mold cavity, and the upper mold is closed to complete mold clamping. The left pusher and the right pusher move towards both ends of the tube blank to complete sealing, and water is injected into the tube. The left pusher and the right pusher synchronously apply axial thrust for feeding, with the axial feeding distance on both sides being 20 mm. At the same time, the internal pressure is gradually increased to 100 MPa to enable free bulging of the middle section of the tube blank. When the top of the branch tube contacts the pusher head, the pusher head starts to retreat along the preset path at a speed of 0.2 mm / s. The axial feeding distance of the left pusher is 10 mm, and the axial feeding distance of the right pusher is 15 mm. At the same time, the internal pressure is continuously increased to 200 MPa. When the pusher head retreats, the pushing force exerted by the pusher head on the tube blank is collected in real time. When the pushing force is less than 200 N, the speed at which the pusher head exits the branch tube cavity is reduced. After the pusher head moves to the designated position, the internal pressure rises to the peak value of 400 MPa. The left pusher and the right pusher stop feeding and only maintain sealing, and the middle punch stops retreating. After the pressure holding is completed, the pressure is reduced in stages, and the pressure reduction gradient is 400→200→50→0 MPa. After the pressure reduction, the tube blank is taken out for heat treatment to eliminate stress. Then it is put into the mold again, and the above steps are repeated until the length of the branch tube reaches 20 cm.

[0064] Example 2

[0065] When the top of the branch tube contacts the pusher head, the pusher head starts to retreat along the preset path at a speed of 0.2 mm / s. The axial feeding distance of the left pusher is 10 mm, and the axial feeding distance of the right pusher is 10 mm. At the same time, the internal pressure is continuously increased to 200 MPa. The remaining steps are the same as those in Example 1.

[0066] Example 3

[0067] When the pusher head retreats, the pushing force exerted by the pusher head on the tube blank is collected in real time. When the pushing force is less than 40 N, the speed at which the pusher head exits the branch tube cavity is reduced. The remaining steps are the same as those in Example 1.

[0068] Example 4

[0069] After the pressure holding is completed, the pressure is directly reduced from 400 MPa to 0 MPa. The remaining steps are the same as those in Example 1.

[0070] Example 5

[0071] The tube blank is pretreated to adapt to the mold space. Molybdenum disulfide, a lubricant, is added to the inner wall of the main tube cavity of the mold, and graphene, a lubricant, is added to the inner wall of the branch tube cavity of the mold and the transition position between the branch tube cavity and the main tube cavity. The remaining steps are the same as those in Example 1.

[0072] Comparative Example

[0073] Obtain stainless steel pipes, cut the pipes to 50 cm, with the end face perpendicularity error ≤ 0.1 mm to form pipe blanks. The included angle between the axes of the main pipe cavity and the branch pipe cavity of the mold is 45°. Pretreat the pipe blanks to adapt to the mold space, and add the lubricant molybdenum disulfide to the inner wall of the mold cavity. Figure 1 Carry out internal high-pressure forming in the equipment shown in Figure 1 , but do not install the vertical plate and auxiliary structures such as the horizontal hydraulic cylinder on the vertical plate. Place the preformed pipe blank into the lower mold cavity, and close the upper mold to complete mold clamping. The left push head and the right push head move towards both ends of the pipe blank to complete sealing, and inject water into the pipe. The left push head and the right push head synchronously apply axial thrust for feeding, with the axial feeding distance on both sides being 20 mm. At the same time, gradually increase the internal pressure to 100 MPa to make the middle section of the pipe blank expand freely. Continue to increase the pressure. During the pressure increase process, the axial feeding distance of the left push head and the right push head is 10 mm. Start pressure holding when the pressure increases to 150 MPa. The left push head and the right push head stop feeding and only maintain sealing. After the pressure holding ends, release the pressure, take out the pipe blank for heat treatment to eliminate stress. Then put it into the mold again and repeat the above steps until the length of the branch pipe reaches 20 cm.

[0074] Produce 50 inclined three-way pipe fittings respectively by the methods of the examples and the comparative examples, and collect relevant data. Among them, if the pipe blank explodes during the forming process, some areas of the pipe wall of the formed three-way pipe fitting are too thin, or there are surface quality defects on the pipe wall of the formed three-way pipe fitting, it is unqualified, as shown in the following table.

[0075] Maximum pressure Number of pushing times required for forming a single inclined tee fitting Number of heat treatment times required for forming a single inclined tee fitting Qualified rate Example 1 400 MPa 5~6 5~6 96% Example 2 400 MPa 5~6 5~6 90% Example 3 400 MPa 5~6 5~6 92% Example 4 400 MPa 5~6 5~6 86% Example 5 400 MPa 5~6 5~6 100% Comparative example 150 MPa 10~11 10~11 72%

[0076] As can be seen from the above table, by the method of the examples, during internal high-pressure forming, compared with the method of the comparative examples, a greater pressure can be used, reducing the number of pushing times and heat treatment times, and significantly improving the qualified rate. From the comparison between Example 1 and Example 2, it can be known that if the left push head and the right push head do not carry out differential feeding, the qualified rate of the inclined three-way pipe fitting will be reduced; from the comparison between Example 1 and Example 3, it can be known that if the threshold value of the top thrust is set too small, the qualified rate of the inclined three-way pipe fitting will be reduced; from the comparison between Example 1 and Example 4, it can be known that if staged pressure relief is not carried out, the qualified rate of the inclined three-way pipe fitting will be reduced; from the comparison between Example 1 and Example 5, it can be known that adding molybdenum disulfide and graphene lubricants to the main pipe cavity and the branch pipe cavity respectively will improve the qualified rate of the inclined three-way pipe fitting.

[0077] Based on the above embodiments of the present application, without explicit negation or conflict, the technical features of one embodiment can be beneficially combined with one or more other embodiments.

[0078] Although some specific embodiments of the present application have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration purposes and not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified or equivalent substitutions can be made to some technical features without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A method for high pressure forming of a three-way pipe fitting, characterized in that: The method is performed by the following device, which includes: The frame body is provided with an upper hydraulic cylinder and a lower hydraulic cylinder opposite to each other vertically, and a left hydraulic cylinder and a right hydraulic cylinder opposite to each other horizontally; An upper mounting plate, connected to the piston rod of the upper hydraulic cylinder, for mounting the upper die of the three-way pipe fitting die; The lower mounting plate is arranged on the frame and opposite to the upper mounting plate. The lower mounting plate is provided with a through hole for the piston rod of the lower hydraulic cylinder to pass through. The lower mounting plate is used to install the lower mold of the three-way pipe fitting mold; The left push head and the right push head are respectively arranged on the piston rods of the left hydraulic cylinder and the right hydraulic cylinder, and are arranged on the same first axis; A horizontal hydraulic cylinder is adjustably arranged on the lower mounting plate, the axis of the piston rod of the horizontal hydraulic cylinder and the first axis are located in the same horizontal plane and the angle between the two axes is variable, so that the axis of the piston rod of the horizontal hydraulic cylinder can be colinear with the axis of the branch pipe cavity of the three-way pipe fitting mold, and the piston rod of the horizontal hydraulic cylinder is provided with a push head, and the radial dimension of the push head is the same as the radial dimension of the branch pipe cavity of the three-way pipe fitting mold; The method comprises: after placing a tube blank and closing the mold, adjusting a horizontal hydraulic cylinder so that the included angle between the axis of the piston rod of the horizontal hydraulic cylinder and the first axis is the included angle between the main pipe and the branch pipe of the three-way pipe fitting to be formed, controlling a push head to enter the branch pipe cavity, increasing pressure to expand the tube blank until it contacts the push head, controlling the push head to move along the branch pipe cavity in a direction away from the tube blank and applying a push force to the tube blank; Control the left pusher and the right pusher to synchronously apply axial thrust to the tube blank and feed the tube blank axially to replenish the material; When the tube blank contacts the push head, the axial feed distances of the left push head and the right push head are controlled to be different, wherein the axial feed distance of the push head in the main tube cavity on the side that forms an obtuse angle with the branch tube cavity is M1, and the axial feed distance of the push head in the main tube cavity on the side that forms an acute angle with the branch tube cavity is M2, and M1>M2.

2. The method according to claim 1, characterized in that After the tube blank contacts the push head, the pressure is continued to be increased, and the speed at which the push head exits the branch tube cavity is controlled to be less than or equal to the speed at which the top end of the branch tube expands along the branch tube cavity.

3. The method according to claim 2, characterized in that The magnitude of the pushing force applied by the pushing head to the tube blank is collected in real time; in response to the pushing force being less than a preset threshold, the speed at which the pushing head exits the branch tube cavity is reduced, and the preset threshold value ranges from 50 to 500N.

4. The method according to claim 2, characterized in that: In response to the push head moving to a preset position, the push head and the left push head and the right push head are controlled to stop moving, and the pressurization is stopped and maintained at the same time. The preset position is related to the length of the branch pipe to be formed.

5. The method according to claim 4, characterized in that After holding the pressure for a preset time, the push head is controlled to move a preset distance along the branch pipe cavity toward the branch pipe, and the value range of the preset distance is 5~30mm.

6. The method according to claim 4, characterized in that Before the tube billet contacts the push head, the internal pressure ranges from 50 to 100 MPa; after the tube billet contacts the push head, the pressure continues to increase, and the internal pressure ranges from 150 to 250 MPa; when the pressure is stopped and maintained, the internal pressure ranges from 300 to 400 MPa; After maintaining the pressure for a preset time, the pressure is reduced in stages.

7. The method according to claim 1, characterized in that A first lubricant is coated on the inner wall of the main cavity of the mold, and a second lubricant is coated on the inner wall of the branch cavity of the mold and the transition position between the branch cavity and the main cavity. The friction coefficient of the first lubricant is greater than the friction coefficient of the second lubricant.

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