A method for controllable increasing of wall thickness of metal round pipe based on diameter reduction

Abstract

The present application relates to the technical field of metal pipe processing, and particularly discloses a metal round pipe wall thickness controllable increasing method based on reducing diameter, which reduces diameter in a hot extrusion manner, and a damping force is applied in the opposite direction of the extrusion force to damp the reduced diameter pipe extruded from a hollow reducing diameter die, the damping force size, the extrusion force size and the backward speed of the damping force applying mechanism are controlled, and the backward speed of the damping force applying mechanism is less than the forward speed of the extrusion force applying mechanism, wherein the difference between the backward speed of the damping force applying mechanism and the forward speed of the extrusion force applying mechanism is constant during the reducing diameter process. The present application can effectively increase the wall thickness of the extruded reduced diameter round pipe uniformly, and the reducing diameter ratio and the wall thickness increasing ratio are controllable.

Description

Technical Field

[0001] This invention relates to the field of metal pipe processing technology, specifically to a method for controllable increase of wall thickness in metal round pipes based on diameter reduction. Background Technology

[0002] There are generally two methods for reducing the diameter of metal pipes: one is to use drawing or rolling (usually called cold drawing or cold rolling) at room temperature to reduce the outer diameter of the metal pipe. The disadvantage of this method is that the reduction ratio in one step is small (<30%). If the reduction ratio is large, multiple drawing processes are required, and annealing is also necessary in between. The other method is to heat the metal pipe to a certain temperature (generally below 600℃) for drawing, which can increase the reduction ratio in one step. This is usually called warm drawing. The two methods mentioned above share common characteristics: the wall thickness increases to a certain extent while reducing the diameter, but this increase in wall thickness is relatively small, and it is uncontrollable. The increase in wall thickness in the transverse direction is uneven, and the straightness of the reduced diameter pipe is extremely poor, requiring straightening again before it can be used. Summary of the Invention

[0003] To address the shortcomings of the existing technology, the purpose of this invention is to provide a reasonable method for controllable increase of the wall thickness of a metal circular tube based on diameter reduction.

[0004] To achieve the above objectives, the present invention adopts the following technical approach: A method for controllable wall thickness increase of metal circular tubes based on diameter reduction is characterized by using hot extrusion for diameter reduction, and applying a damping force in the opposite direction of the extrusion force to dampen the reduced-diameter tube extruded from the hollow diameter reduction die. The magnitude of the damping force and the extrusion force are controlled such that the retracting speed of the damping force application mechanism is less than the forward speed of the extrusion force application mechanism. During the diameter reduction process, the difference between the retracting speed of the damping force application mechanism and the forward speed of the extrusion force application mechanism remains constant. In practice, the specific value of the speed difference is determined based on the specific diameter reduction ratio and wall thickness increase ratio, and this specific value must be kept stable during actual operation.

[0005] Furthermore, the above-mentioned method for controllable increase of the wall thickness of metal round tubes based on diameter reduction is based on a specially designed forming machine, which includes a machine base, a heater, a hollow diameter reduction die, an extrusion pressure application mechanism, and a damping force application mechanism. The machine base includes a pressing cylinder fixing plate, a damping cylinder fixing plate, a base, an upper frame, a lower frame, and a mold base. The pressing cylinder fixing plate, the damping cylinder fixing plate, and the mold base are all vertically fixedly connected to the base. The upper frame and the lower frame are horizontally arranged and fixedly connected between the pressing cylinder fixing plate and the damping cylinder fixing plate. The mold base is fixedly connected between the upper frame and the lower frame. The extrusion pressure application mechanism includes an extrusion cylinder and a movable top plate. The extrusion cylinder is fixedly connected to the extrusion cylinder fixed vertical plate. The free end of the piston rod of the extrusion cylinder is fixedly connected to the movable top plate. The movable top plate slides between the upper frame and the lower frame and performs a horizontal linear sliding action relative to the upper frame and the lower frame under the action of the extrusion cylinder. The damping force application mechanism includes a damping cylinder, a movable damping plate, and a damping top rod. The damping cylinder is fixedly connected to the damping cylinder fixed plate. The extension direction of the piston rod of the damping cylinder is opposite to the extension direction of the piston rod of the compression cylinder. The free end of the piston rod of the damping cylinder is fixedly connected to the movable damping plate. The damping top rod is fixedly connected to the other side of the movable damping plate. The movable damping plate is slidably fitted between the upper frame and the lower frame and performs a horizontal linear sliding motion relative to the upper frame and the lower frame under the action of the damping cylinder. The heater and the hollow reducing die are arranged between the extrusion force application mechanism and the damping force application mechanism, with the heater closer to the extrusion force application mechanism. The heater, the hollow reducing die, the damping top rod, the damping cylinder piston rod, the moving top plate, and the moving cylinder piston rod are all coaxially arranged.

[0006] Furthermore, multiple upper guide wheel mechanisms are connected to the upper frame. Each upper guide wheel mechanism includes an upper guide wheel frame lifting cylinder, an upper guide wheel frame, and an upper guide wheel. The cylinder of the upper guide wheel frame lifting cylinder is fixedly connected to the upper frame. The piston rod of the upper guide wheel frame lifting cylinder extends vertically downward and is fixedly connected to the end of the piston rod. An upper guide wheel is rotatably connected to the upper guide wheel frame. Multiple lower guide wheel mechanisms are connected to the lower frame. Each lower guide wheel mechanism includes a lower guide wheel frame lifting cylinder, a lower guide wheel frame, and a lower guide wheel. The cylinder of the lower guide wheel frame lifting cylinder is fixedly connected to the lower frame. The piston rod of the lower guide wheel frame lifting cylinder extends vertically upward and is fixedly connected to the end of the piston rod. A lower guide wheel is rotatably connected to the lower guide wheel frame. The upper guide wheels and lower guide wheels are arranged symmetrically, one above the other. The upper guide wheel mechanism and the lower guide wheel mechanism are only arranged between the compression cylinder fixing plate and the heater.

[0007] Furthermore, multiple lifting roller mechanisms are arranged between the hollow diameter reduction mold and the damping cylinder fixing plate. Each lifting roller mechanism includes a roller lifting cylinder, a roller fixing frame, and a roller. The cylinder of the roller lifting cylinder is fixedly connected to the lower frame. The piston rod of the roller lifting cylinder extends vertically upward and is fixedly connected to the roller fixing frame at the end of the piston rod. A roller is rotatably connected to each roller fixing frame.

[0008] Furthermore, a circular tube feeding transverse movement mechanism is provided on one or both sides of the lower guide wheel mechanism; the circular tube feeding transverse movement mechanism includes a transverse movement platform and a feeding assembly. The transverse movement platform includes a support frame, a transverse movement platform beam, and stops. The support frame is fixedly connected to the lower frame. Two parallel transverse movement platform beams are fixedly connected to the top of the support frame, and the extension direction of each transverse movement platform beam is orthogonal to the arrangement direction of the lower guide wheel mechanism. A stop is fixedly connected to the top of each end of each transverse movement platform beam. The feeding assembly includes a telescopic arm beam, a U-shaped bracket, a telescopic arm cylinder, a telescopic arm, and a telescopic arm beam lifting cylinder. The two telescopic arm beams are arranged between the two transverse movement platform beams and are parallel to each other. A telescopic arm is slidably fitted inside each telescopic arm beam, i.e., the telescopic arm beam is square. The telescopic arm is a hollow tube with a square cross-section. Driven by the telescopic arm cylinder, it can extend and retract inside the telescopic arm beam. One end of the telescopic arm is connected to the piston rod of the telescopic arm cylinder, which is fixedly connected to the telescopic arm beam. The telescopic arm beam is hinged to the support frame. A U-shaped bracket is fixedly connected to the top of the other end of each telescopic arm. Correspondingly, a U-shaped groove is provided on each telescopic arm beam to allow the U-shaped bracket to reciprocate, preventing interference with the U-shaped bracket during the reciprocating linear motion of the telescopic arm. The tail of the telescopic arm beam lifting cylinder is hinged to the support frame. The piston rod of the lifting cylinder extends upwards and its end is hinged to the telescopic arm beam. The piston rod of the lifting cylinder can lift the telescopic arm beam, causing it to swing and rise, while simultaneously raising and lowering the telescopic arm and the U-shaped bracket.

[0009] Furthermore, an extrusion tube removal platform is provided on one side of the lifting roller mechanism. The extrusion tube removal platform includes a base frame, a removal platform beam, a removal telescopic arm, a removal telescopic arm cylinder, and a stop block. The base frame is fixedly connected to the lower frame. Two parallel removal platform beams are fixedly connected to the top of the base frame. The extension direction of each removal platform beam is orthogonal to the arrangement direction of the lower guide wheel mechanism. A removal telescopic arm is slidably fitted inside each removal platform beam. One end of each removal telescopic arm is fixedly connected to the piston rod of a removal telescopic arm cylinder. The tail of each removal telescopic arm cylinder is fixedly connected to the corresponding removal platform beam. A stop block is fixedly connected to the top of the free end of each removal telescopic arm.

[0010] Furthermore, the heater is cylindrical, and the inner diameter of the cylinder is slightly larger than the outer diameter of the tube.

[0011] Furthermore, the above-mentioned method for controllable increase of the wall thickness of a metal circular tube based on diameter reduction is specifically achieved through the following steps: Step 1) Place multiple round tubes to be processed on the round tube feeding and transverse movement mechanism beforehand. When the first tube near the lower frame of the forming machine contacts the corresponding stop block, start the feeding assembly. The telescopic arm beam lifting cylinder lowers the telescopic arm beam until the U-shaped bracket is below the bottom of the round tube. Then start the telescopic arm cylinder so that the U-shaped bracket of the telescopic arm is below the first tube on the transverse movement frame beam. The telescopic arm beam lifting cylinder raises the telescopic arm beam and the telescopic arm, so that the U-shaped bracket lifts the first tube until the bottom of the round tube is above the stop block on the corresponding side of the transverse movement frame beam. Then start the telescopic arm cylinder to send the round tube horizontally above the lower guide wheel. At this time, the round tube is called the pre-diameter reduction mother tube. As the lower guide wheel rises, the telescopic arm descends and retracts to the origin. The first feeding is completed. Step 2) The pre-reduction tube is on the lower guide wheel and coaxial with the piston rod of the extrusion cylinder. Then, multiple upper guide wheels descend to press on the pre-reduction tube. The extrusion cylinder is started, which drives the moving top plate and the mandrel on the moving top plate to move at a constant speed. When the mandrel contacts one end of the pre-reduction tube, it continues to move forward and pushes the pre-reduction tube to move horizontally at a constant speed. When the moving top plate approaches a pair of upper and lower guide wheels, the pair of upper and lower guide wheels automatically rise and fall so that the moving top plate can continue to move forward without interference. Step 3) When one end of the pre-reduction header enters the heater, the heater is started to heat the pre-reduction header. The heating temperature is set to 650-900℃. Step 4) The extrusion cylinder continues to push the pre-reduction tube forward. The heated pre-reduction tube is continuously pushed into the cavity of the hollow reduction mold. The round tube extruded from the cavity is the reduced round tube. The diameter of the pre-reduction tube entering the cavity is D1 and the wall thickness is t1. The diameter of the reduced round tube extruded from the cavity is D2 and the wall thickness is t2. Before extruding from the cavity, the damping cylinder is activated in advance to push the moving damping plate to move horizontally and uniformly towards the moving top plate until the positioning shaft head on the damping top rod is flush with the outlet of the hollow reduction mold. Step 5) The extrusion cylinder continues to push the front tube of the reduced diameter forward. When one end of the reduced diameter tube contacts the positioning shaft and pushes the positioning shaft into the inner cavity of the reduced diameter tube, the damping cylinder reverses and moves backward. The backward speed of the moving damping plate is controlled to be slower than the forward speed of the moving top plate. Step 6) After a round tube is completely extruded from the reducing die, the extrusion cylinder returns to its original position, and the reduced-diameter round tube falls onto the roller of the lifting roller mechanism. The roller is raised, and the reduced-diameter round tube rolls along the inclined surface of the roller to the extruded round tube removal platform. The removal telescopic arm cylinder drives the removal telescopic arm to retract, bringing the reduced-diameter round tube onto the beam of the removal platform and close to the outer end.

[0012] Furthermore, the maximum reduction ratio is D2 / D1=0.6, and the maximum increase in wall thickness is t2 / t1=2.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention applies damping force in the opposite direction of thermal reduction by extrusion, and controls the magnitude of damping force and extrusion force so that the backward speed of the damping force application mechanism is less than the forward speed of the extrusion force application mechanism. The difference between the backward speed of the damping force application mechanism and the forward speed of the extrusion force application mechanism remains constant in each reduction process, which can effectively make the wall thickness of the extruded reduced diameter round tube increase uniformly, and the reduction ratio and the wall thickness increase ratio are controllable. 2. The specially designed forming machine of this invention can effectively ensure the straightness of the reduced diameter round tube, and can be used without straightening; 3. The method of the present invention can achieve a diameter reduction ratio of up to 0.7 and a wall thickness increase ratio of up to 1.85 in a single diameter reduction process. Compared with the prior art, the wall thickness increase ratio is relatively large. Attached Figure Description

[0014] Figure 1 This is a front structural diagram of the specially manufactured molding machine of the present invention; Figure 2 This is a top view schematic diagram of the specially manufactured molding machine of the present invention; Figure 3 This is a cross-sectional schematic diagram of the transverse moving platform in the circular tube feeding transverse moving mechanism of the present invention; Figure 4 This is a cross-sectional schematic diagram of the feeding assembly in the circular tube feeding transverse movement mechanism of the present invention; Figure 5 This is a cross-sectional schematic diagram of the extruded cylindrical tube removal platform according to the present invention; Figure 6 This is a schematic diagram of the cross-section of the moving telescopic arm and the telescopic arm beam in the moving feeding assembly of the present invention; Figure 7 This is a schematic diagram of the cross-section of the telescopic arm and the crossbeam of the tube removal platform described in this invention. Figure 8 This is a schematic diagram of the structure of the hollow diameter reduction mold cavity described in this invention; Wherein: (1) is the machine base, (1-1) is the fixed plate for the extrusion cylinder, (1-2) is the fixed plate for the damping cylinder, (1-3) is the base, (1-4) is the upper frame, (1-5) is the lower frame, and (1-6) is the center line of the molding machine; (2) is the extrusion cylinder, (2-1) is the piston rod of the extrusion cylinder; (3) is the moving top plate, (3-1) is the top head; (4) is the upper guide rail of the moving top plate; (5) is the lower guide rail of the moving top plate; (6) is the upper guide wheel mechanism, (6-1) is the upper guide wheel frame, and (6-2) is the upper guide wheel frame. (6-3) is the upper guide wheel frame lifting cylinder; (7) is the lower guide wheel mechanism; (7-1) is the lower guide wheel frame; (7-2) is the lower guide wheel frame lifting cylinder; (7-3) is the lower guide wheel; (8) is the front tube for diameter reduction; (9) is the heater; (9-1) is the cylindrical induction coil; (9-2) is the high-temperature resistant frame; (10) is the diameter reduction mold; (10-1) is the mold cavity; (11) is the mold base; (12) is the damping cylinder; (12-1) is the piston rod; (13) is the damping push rod; 14) is the moving damping plate; (15) is the upper guide rail of the moving damping plate; (16) is the lower guide rail of the moving damping plate; (17) is the reduced diameter round pipe; (18) is the spare main pipe; (19) is the transverse moving platform; (19-1) is the transverse moving platform crossbeam; (19-2) is the support frame; (19-3) is the stop block; (20) is the feeding assembly; (20-1) is the telescopic arm crossbeam; (20-2) is the U-shaped bracket; (20-3) is the telescopic arm cylinder; (20-4) is the telescopic arm fixing hinge; (20-5) For the telescopic arm to be moved in, (20-6) is the telescopic arm beam lifting cylinder; (21) is the lifting roller mechanism, (21-1) is the roller, (21-1-1) is the inclined plane, (21-2) is the roller lifting cylinder, (21-3) is the roller fixing frame; (22) is the extrusion tube removal platform, (22-1) is the basic frame, (22-2) is the removal platform beam, (22-2-1) is the U-shaped groove, (22-3) is the telescopic arm to be moved out, (22-4) is the telescopic arm to be moved out cylinder, (22-5) is the stop block. Detailed Implementation

[0015] The present invention will now be further described with reference to specific embodiments. Any parts not detailed below are based on existing techniques in the art.

[0016] like Figure 1-8 As shown, the molding machine specially designed by the present invention includes a base 1, a heater (9), a hollow diameter reduction mold (10), an extrusion pressure application mechanism, an upper guide wheel mechanism (6), a lower guide wheel mechanism (7), a damping force application mechanism, a lifting roller mechanism (21), a round tube feeding and transverse movement mechanism, and an extruded round tube removal platform (22).

[0017] The machine base 1 includes an extrusion cylinder fixing plate (1-1), a damping cylinder fixing plate (1-2), a base (1-3), an upper frame (1-4), a lower frame (1-5), and a mold base (11). The extrusion cylinder fixing plate (1-1), the damping cylinder fixing plate (1-2), and the mold base (11) are vertically fixed to the base (1-3). Furthermore, the extrusion cylinder fixing plate (1-1) and the damping cylinder fixing plate (1-2) are connected and supported by the upper frame (1-4) and the lower frame (1-5). The mold base (11) is vertically fixed between the upper frame (1-4) and the lower frame (1-5). (1-6) is the center line of the molding machine.

[0018] The extrusion pressure application mechanism includes an extrusion cylinder (2) and a movable top plate (3). The extrusion cylinder (2) is horizontally fixed on the extrusion cylinder fixed plate (1-1). The center line of the extrusion cylinder is coaxial with the center line of the molding machine (1-6). The movable top plate (3) is connected to the piston rod (2-1) of the extrusion cylinder. The top head (3-1) is coaxial with the extrusion cylinder (2) and is fixed on the movable top plate (3). The upper guide rail (4) of the movable top plate is horizontally fixed on the upper frame (1-4). The lower guide rail (5) of the movable top plate is fixed on the lower frame (1-5). The upper and lower parts of the movable top plate (3) are respectively embedded and slidably fitted on the upper guide rail (4) and the lower guide rail (5) of the movable top plate. The movable top plate (3) moves horizontally between the upper guide rail (4) and the lower guide rail (5) of the movable top plate. The upper guide rail (4) and the lower guide rail (5) of the movable top plate ensure the straightness accuracy of the horizontal movement of the movable top plate (3).

[0019] Multiple upper guide wheel mechanisms (6) are connected to the upper frame (1-4). Each upper guide wheel mechanism (6) includes an upper guide wheel frame lifting cylinder (6-2), an upper guide wheel frame (6-1), and an upper guide wheel (6-3). The cylinder of the upper guide wheel frame lifting cylinder (6-2) is fixedly connected to the upper frame (1-4). The piston rod of the upper guide wheel frame lifting cylinder (6-2) extends vertically downward and is fixedly connected to the end of the piston rod to the upper guide wheel frame (6-1). The upper guide wheel (6-3) is rotatably connected to the upper guide wheel frame (6-1). The upper guide wheel (6-3) is driven to rise and fall by the upper guide wheel frame lifting cylinder (6-2) to press against or move away from the front diameter reduction tube (8). Multiple lower guide wheel mechanisms (7) are connected to the lower frame (1-5). Each lower guide wheel mechanism (7) includes a lower guide wheel frame lifting cylinder (7-2) and a lower guide wheel frame (7-1). The lower guide wheel (7-3) has its cylinder barrel fixedly connected to the lower frame (1-5) of the lower guide wheel frame lifting cylinder (7-2). The piston rod of the lower guide wheel frame lifting cylinder (7-2) extends vertically upward and is fixedly connected to the lower guide wheel frame (7-1) at the end of the piston rod. The lower guide wheel (7-3) is rotatably connected to the lower guide wheel frame (7-1). The lower guide wheel frame lifting cylinder (7-2) can make the lower guide wheel (7-3) rise and fall, i.e. support or leave the front mother tube (8) before the diameter reduction. Moreover, the rising height of the lower guide wheel (7-3) is controllable and adjustable, which fully ensures that the central axis of the mother tube of different specifications is horizontal and coaxial with the center line (1-6) of the forming machine. The upper guide wheel (6-3) and the lower guide wheel (7-3) are symmetrically arranged one above the other. The upper guide wheel mechanism (6) and the lower guide wheel mechanism (7) are evenly arranged at equal intervals between the extrusion cylinder fixed plate (1-1) and the heater (9).

[0020] The heater (9) of this invention uses a hollow flat copper tube wound into a cylindrical induction coil (9-1). The inner diameter of the cylinder is slightly larger than the outer diameter (8) of the mother tube before diameter reduction. It is fixed on the lower frame (1-5) by an insulating high-temperature resistant frame (9-2). The center line of the inner diameter hole of the heater (9) is coaxial with the center line (1-6) of the forming machine. The hollow diameter reduction mold (10) is detachably connected to the mold base (11). The axis of the cavity (10-1) of the hollow diameter reduction mold (10) is coaxial with the center line of the extrusion forming machine. The mother tube (8) before diameter reduction is heated while passing horizontally between the upper guide wheel and the lower guide wheel through the heater (9) under the push of the moving top plate (3) driven by the extrusion cylinder (2). Then it enters the cavity (10-1) of the hollow diameter reduction mold (10) for diameter reduction.

[0021] The damping force application mechanism includes a damping cylinder (12), a movable damping plate (14), and a damping top rod (13). The damping cylinder (12) is fixedly connected to the damping cylinder fixed plate (1-2) and is coaxial with the center line (1-6) of the molding machine. The extension direction of the piston rod (12-1) of the damping cylinder (12) is opposite to the extension direction of the piston rod (2-1) of the extrusion cylinder (2) (both are horizontal extensions). The free end of the piston rod (12-1) of the damping cylinder (12) is fixedly connected to the movable damping plate (14). The damping top rod (13) is fixedly connected to the other side of the movable damping plate (14). The damping top rod (13) is coaxial with the damping cylinder (12). The upper guide rail (15) of the movable damping plate is fixed on the upper frame (1-4), and the lower guide rail (16) of the movable damping plate is fixed on the lower frame (1-5). The upper and lower parts of the movable damping plate (14) are respectively embedded and slidably fitted on the upper guide rail (15) and the lower guide rail (16) of the movable damping plate. The movable damping plate (14) moves horizontally left and right between the two guide rails (15) and (16), and the extruded reduced diameter round tube (17) has a diameter of D2.

[0022] To ensure that the extruded diameter-reducing tube (17) does not deform after exiting the hollow diameter-reducing mold (10), multiple lifting roller mechanisms (21) are evenly arranged between the hollow diameter-reducing mold (10) and the damping cylinder fixing plate (1-2). Each lifting roller mechanism includes a roller lifting cylinder (21-2), a roller fixing frame (21-3), and a roller (21-1). The cylinder of the roller lifting cylinder (21-2) is fixedly connected to the lower frame (1-5). The piston rod of the roller lifting cylinder (21-2) extends vertically upward and is fixedly connected to the roller fixing frame (21-3) at the end of the piston rod. A roller (21-1) is rotatably connected to each roller fixing frame (21-3). Each roller (21-1) has a slope (21-1-1) formed on the outer periphery of the section of its length away from the extruded tube exiting the frame. This slope is downward from the side away from the extruded tube exiting the frame to the side closer to the extruded tube exiting the frame.

[0023] like Figure 3 , Figure 4 , Figure 6As shown, in order to place the spare mother tube (18) on the lower guide wheel (7-3), a round tube feeding transverse movement mechanism is set in the direction perpendicular to the center line (1-6) of the forming machine. The round tube feeding transverse movement mechanism includes a transverse movement platform (19) and a feeding assembly (20), wherein the transverse movement platform (19) includes a support frame (19-2), a transverse movement platform crossbeam (19-1), and a stop block (19-3). The support frame (19-2) is fixedly connected to the lower frame (1-5). Two parallel transverse platform beams (19-1) are fixedly connected to the top of the support frame (19-2). The extension direction of each transverse platform beam (19-1) is orthogonal to the arrangement direction of the lower guide wheel mechanism (7). A stop block (19-3) is fixedly connected to the top of one or both ends of each transverse platform beam (19-1). The feeding assembly (20) includes a telescopic arm beam (20-1), a U-shaped bracket (20-2), a telescopic arm cylinder (20-3), a telescopic arm (20-5), and a telescopic arm beam lifting cylinder (20-6). Two telescopic arm beams (20-1) are positioned between two transverse platform beams (19-1), and the telescopic arm beams (20-1) and transverse platform beams (19-1) are parallel to each other. Each telescopic arm beam (20-1) is fixedly connected between the support frame (19-2) and the lower frame (1-5). A sliding telescopic arm (20-5) is slidably fitted within each telescopic arm beam (20-1). That is, the telescopic arm beam (20-1) is a square hollow tube, and the sliding telescopic arm (20-5) also has a square cross-section. Under the push of the sliding telescopic arm cylinder (20-3), the sliding telescopic arm (20-5) can be moved to the corresponding telescopic arm. The crossbeam (20-1) extends and retracts internally; one end of the telescopic arm (20-5) is fixedly connected to the piston rod of the telescopic arm cylinder (20-3), and the tail of the telescopic arm cylinder (20-3) is fixedly connected to the telescopic arm crossbeam (20-1), while the telescopic arm crossbeam (20-1) is hinged to the support frame (19-2) through the telescopic arm fixing hinge (20-4); a U-shaped bracket (20-2) is fixedly connected to the top of one end of each telescopic arm (20-5) near the lower frame (1-5), and correspondingly, a section is provided on each telescopic arm crossbeam (20-1) for the U-shaped bracket (20-2) to reciprocate and make room. The U-shaped groove avoids interference between the telescopic arm beam (20-1) and the U-shaped bracket (20-2) on the telescopic arm during the reciprocating linear motion of the telescopic arm. The tail of the telescopic arm beam lifting cylinder (20-3) is hinged to the support frame (19-2), and the piston rod of the telescopic arm beam lifting cylinder (20-6) extends upward and the end of the piston rod is hinged to the telescopic arm beam (20-1) (the specific hinge point is the bottom of the telescopic arm beam near the lower frame). The piston rod of the telescopic arm beam lifting cylinder (20-6) can lift the telescopic arm beam and swing it up and down, while also lifting the telescopic arm (20-5) and the U-shaped bracket (20-2).Feeding is achieved by extending and retracting the telescopic arm cylinder (20-3) in the horizontal direction. The spare mother pipe (18) is placed on the crossbeam (19-1) of the transverse platform for standby. When needed, the spare mother pipe (18) is moved to the lower guide wheel (7-3) by the feeding mechanism (20) to become the mother pipe (8) before the diameter reduction.

[0024] Figure 5 , Figure 7 This is a cross-sectional schematic diagram of the extruded round tube removal platform of the present invention. In order to move the extruded reduced diameter round tube (17) laterally out of the molding machine, an extruded round tube removal platform (22) is provided. The extruded round tube removal platform (22) is arranged perpendicular to the center line of the molding machine on the outside of the molding machine. The extruded round tube removal platform (22) includes a base frame (22-1), a removal platform crossbeam (22-2), a removal telescopic arm (22-3), a removal telescopic arm cylinder (22-4), and a stop block (22-5). The base frame (22-1) is fixedly connected to the lower frame (1-5). Two parallel removal platform crossbeams (22-2) are fixedly connected to the top of the base frame (22-1). The cross section of the removal platform crossbeam (22-2) is a square hollow steel section. The cross section of the removal telescopic arm (22-3) is also square and is slidably clearance-fitted with the inner hole of the removal platform crossbeam (22-2). Each telescopic arm (22-3) has a piston rod of a telescopic arm cylinder (22-4) fixedly connected to one end. The telescopic arm cylinder (22-4) is installed inside the crossbeam (22-2) of the removal platform, and the tail of the cylinder barrel of the telescopic arm cylinder (22-4) is fixed on the crossbeam (22-2). In order to prevent the stop block (22-5) on the telescopic arm (22-3) from interfering with the crossbeam (22-2), a U-shaped groove (22-2-1) is also opened on the upper surface of each crossbeam (22-2). Example

[0025] The method for controllably increasing the wall thickness of a metal circular tube based on diameter reduction is achieved through the following steps: First, multiple lower guide wheels (7-3) descend to the same horizontal design position, and multiple upper guide wheels (6-3) rise. When the first spare mother tube (18) near the side of the lower frame (1-5) of the forming machine contacts the stop block (19-3) on the corresponding side, the feeding assembly (20) is activated. The telescopic arm beam lifting cylinder (20-6) lowers the telescopic arm beam (20-1) until the U-shaped bracket (20-2) is lower than the bottom of the spare mother tube (18). Then, the telescopic arm lifting cylinder (20-3) is activated so that the U-shaped bracket (20-2) of the telescopic arm is below the first spare mother tube (18). Then, the telescopic arm beam lifting cylinder (20-6) rises, driving the telescopic arm beam. (20-1) The telescopic arm (20-5) is raised, and the U-shaped bracket (20-2) lifts the first spare mother tube (18) near the lower frame (1-5) until the bottom of the spare mother tube (18) is higher than the stop block (19-3) on that side. Then, the telescopic arm cylinder (20-3) is activated to extend the telescopic arm (20-5) and move the spare mother tube (18) horizontally onto the lower guide wheel (7-3), so that the first spare mother tube becomes the pre-reduction mother tube (8). The lower guide wheels (7-3) are raised so that the center line of the pre-reduction mother tube (8) is coaxial with the center line of the forming machine (1-6). Then, the upper guide wheel (6-3) is lowered to press the pre-reduction mother tube (8). The second step is to start the extrusion cylinder (2), which drives the moving top plate (3) and the mandrel (3-1) to move to the left at a constant speed. When the mandrel (3-1) pushes into the tail end of the reducing front tube (8), it continues to move forward and pushes the reducing front tube (8) to move horizontally to the left. The reducing front tube (8) moves horizontally between the upper and lower guide wheels (6-3) and (7-3). When the moving top plate (3) approaches a pair of upper and lower guide wheels (6-3) and (7-3), the pair of upper and lower guide wheels (6-3) and (7-3) automatically rise and fall, so that the moving top plate (3) can continue to move forward without interference. The third step is that the front tube (8) before the diameter reduction continues to move forward under the push of the extrusion cylinder (2). When the head of the front tube (8) before the diameter reduction enters the heater (9), the heater is started. The current and voltage are applied according to the set value to start heating the front tube (8) before the diameter reduction. The heating temperature is set to a fixed value in the range of 650-900℃. The front tube (8) before the diameter reduction continues to move forward under the push of the extrusion cylinder and passes through the heater (9) while being heated to the design temperature. In the fourth step, the extrusion cylinder (2) continues to advance the pre-reduction tube (8). The heated pre-reduction tube (8) head enters the cavity (10-1) of the hollow reduction mold (10). The heated pre-reduction tube (8) is continuously extruded into the cavity (10-1), and at the same time, the extruded reduction tube (17) is also continuously extruded from the left side of the cavity (10-1) of the mold 10. Because the inner diameter of the cavity (10-1) gradually transitions from large to small, and the longitudinal section is trumpet-shaped (as shown in the image), the reduction tube is continuously extruded from the left side of the cavity (10-1) of the mold 10. Figure 8 The inlet diameter D0 of the mold cavity (10-1) exceeds the diameter D1 of the mother tube before the reduction. Therefore, the diameter D1 of the mother tube (8) before the reduction enters the mold cavity (10-1) and is reduced to the diameter D2 of the extruded reduced round tube (17), while the tube wall thickness changes from t1 to t2. Fifth step: Before the extrusion of the reduced diameter round tube (17) into the hollow reduced diameter die (10), the damping cylinder (12) is opened, and the moving damping plate (14) is pushed to the right quickly by the piston rod (12-1) along with the damping top rod (13), and the positioning shaft head (13-1) stops at the position flush with the outlet of the hollow reduced diameter die (10); In the sixth step, the extrusion cylinder (2) continues to advance, pushing the pre-diameter reduction tube (8) forward. When the head of the extruded reduced diameter tube (17) contacts the positioning shaft head (13-1) of the damping push rod (13), (13-1) pushes into the inner cavity of the extruded reduced diameter tube (17). The damping cylinder (12) is reversed and moved backward by the program-controlled hydraulic system, and the backward speed of the piston rod of the damping cylinder (12) is slower than the forward speed of the extrusion cylinder (2), which generates a certain resistance to the forward movement of the extruded reduced diameter tube (17), i.e., a damping effect. The damping force is adjustable and controllable. The result of the adjustable and controllable damping force and speed is that the diameter reduction ratio of the extruded reduced diameter tube (17), i.e., D1 / D2, and the wall thickness increase ratio of the tube, i.e., t2 / t1, can be controlled under the set conditions. The maximum diameter reduction ratio of the present invention is D2 / D1=0.6, and the maximum wall thickness increase ratio is t2 / t1=2.

[0026] The key point of this invention is the setting of the difference between the forward speed of the extruded reducing round tube (17), i.e. the backward speed of the damping cylinder (12), and the forward speed of the extrusion cylinder (2). Specific example design: such as the diameter D1 and wall thickness t1 of the mother tube (8) before reduction, and the outer diameter D2 and wall thickness t2 of the product (i.e. the reduced round tube) after reduction; if the forward speed of the extrusion cylinder (2) is designed to be V1 and the backward speed of the damping cylinder (12) is V2, then V2=V1(D1-t1)t1 / (D2-t2)t2.

[0027] Step 7: After the first diameter reduction tube (8) is completely extruded from the hollow diameter reduction die (10), it falls onto the roller (21-1) of the lifting roller mechanism (21). The roller of the lifting roller mechanism (21-1) is raised, and the extruded diameter reduction tube (17) will roll laterally along the inclined surface (21-1-1) of the roller to the material stop block (22-5) on the removing telescopic arm (22-3) of the extruded tube removal platform (22). Step 8: Activate the cylinder (22-2) to retract the telescopic arm (22-3), and the stop block (22-5) will bring the extruded reducing diameter round tube (17) onto the crossbeam (22-2) of the removal platform and close to the outer end.

[0028] This completes the entire process of feeding a tube laterally into the molding machine, then extruding and reducing its diameter, and finally removing the extruded and reduced-diameter product from the molding machine.

Claims

1. A method for controllable increase of wall thickness in a metal circular tube based on diameter reduction, characterized in that, The diameter is reduced by hot extrusion, and a damping force is applied in the opposite direction of the extrusion force to dampen the reduced diameter tube extruded from the hollow diameter reduction die; the magnitude of the damping force and the magnitude of the extrusion force are controlled such that the backward speed of the damping force application mechanism is less than the forward speed of the extrusion force application mechanism, wherein the difference between the backward speed of the damping force application mechanism and the forward speed of the extrusion force application mechanism remains unchanged during the diameter reduction process. The above method is based on a specially designed molding machine, which includes a base, a heater, a hollow reducing die, an extrusion pressure application mechanism, and a damping force application mechanism. The machine base includes a pressing cylinder fixing plate, a damping cylinder fixing plate, a base, an upper frame, a lower frame, and a mold base. The pressing cylinder fixing plate, the damping cylinder fixing plate, and the mold base are all vertically fixedly connected to the base. The upper frame and the lower frame are horizontally arranged and fixedly connected between the pressing cylinder fixing plate and the damping cylinder fixing plate. The mold base is fixedly connected between the upper frame and the lower frame. The extrusion pressure application mechanism includes an extrusion cylinder and a movable top plate. The extrusion cylinder is fixedly connected to the extrusion cylinder fixed vertical plate. The free end of the piston rod of the extrusion cylinder is fixedly connected to the movable top plate. The movable top plate slides between the upper frame and the lower frame and performs a horizontal linear sliding action relative to the upper frame and the lower frame under the action of the extrusion cylinder. The damping force application mechanism includes a damping cylinder, a movable damping plate, and a damping top rod. The damping cylinder is fixedly connected to the damping cylinder fixed plate. The extension direction of the piston rod of the damping cylinder is opposite to the extension direction of the piston rod of the compression cylinder. The free end of the piston rod of the damping cylinder is fixedly connected to the movable damping plate. The damping top rod is fixedly connected to the other side of the movable damping plate. The movable damping plate is slidably fitted between the upper frame and the lower frame and performs a horizontal linear sliding motion relative to the upper frame and the lower frame under the action of the damping cylinder. The heater and the hollow reducing die are arranged between the extrusion force application mechanism and the damping force application mechanism, with the heater closer to the extrusion force application mechanism. The heater, the hollow reducing die, the damping top rod, the damping cylinder piston rod, the moving top plate, and the extrusion cylinder piston rod are arranged coaxially.

2. The method for controllable increase of wall thickness of a metal circular tube based on diameter reduction according to claim 1, characterized in that, Multiple upper guide wheel mechanisms are connected to the upper frame. Each upper guide wheel mechanism includes an upper guide wheel frame lifting cylinder, an upper guide wheel frame, and an upper guide wheel. The cylinder of the upper guide wheel frame lifting cylinder is fixedly connected to the upper frame. The piston rod of the upper guide wheel frame lifting cylinder extends vertically downward and is fixedly connected to the end of the piston rod. An upper guide wheel is rotatably connected to the upper guide wheel frame. Multiple lower guide wheel mechanisms are connected to the lower frame. Each lower guide wheel mechanism includes a lower guide wheel frame lifting cylinder, a lower guide wheel frame, and a lower guide wheel. The cylinder of the lower guide wheel frame lifting cylinder is fixedly connected to the lower frame. The piston rod of the lower guide wheel frame lifting cylinder extends vertically upward and is fixedly connected to the end of the piston rod. A lower guide wheel is rotatably connected to the lower guide wheel frame. The upper and lower guide wheels are arranged symmetrically, one above the other. The upper and lower guide wheel mechanisms are only arranged between the extrusion cylinder fixing plate and the heater.

3. A method for controllable increase of wall thickness of a metal circular tube based on diameter reduction, as described in claim 1 or 2, characterized in that, Multiple lifting roller mechanisms are arranged between the hollow diameter reduction mold and the damping cylinder fixing plate. Each lifting roller mechanism includes a roller lifting cylinder, a roller fixing frame, and a roller. The cylinder of the roller lifting cylinder is fixedly connected to the lower frame. The piston rod of the roller lifting cylinder extends vertically upward and is fixedly connected to the roller fixing frame at the end of the piston rod. A roller is rotatably connected to each roller fixing frame.

4. The method for controllable increase of wall thickness of a metal circular tube based on diameter reduction according to claim 3, characterized in that, A circular tube feeding transverse movement mechanism is provided on one or both sides of the lower guide wheel mechanism; the circular tube feeding transverse movement mechanism includes a transverse movement platform and a feeding assembly. The transverse movement platform includes a support frame, a transverse movement platform beam, and stops. The support frame is fixedly connected to the lower frame. Two parallel transverse movement platform beams are fixedly connected to the top of the support frame, and the extension direction of each transverse movement platform beam is orthogonal to the arrangement direction of the lower guide wheel mechanism. A stop is fixedly connected to the top of each end of each transverse movement platform beam. The feeding assembly includes a telescopic arm beam, a U-shaped bracket, a telescopic arm cylinder, a telescopic arm, and a telescopic arm beam lifting cylinder. The telescopic arm beam is positioned between two transverse platform beams, and the telescopic arm beam is parallel to the transverse platform beam. A sliding telescopic arm is slidably fitted within each telescopic arm beam. One end of the sliding telescopic arm is connected to the piston rod of the sliding telescopic arm cylinder. The sliding telescopic arm cylinder is fixedly connected to the telescopic arm beam. The telescopic arm beam is hinged to the support frame. A U-shaped bracket is fixedly connected to the top of the other end of each sliding telescopic arm. Correspondingly, a U-shaped groove is provided on each telescopic arm beam to allow the U-shaped bracket to reciprocate. The bottom of the telescopic arm beam lifting cylinder is hinged to the support frame, and the piston rod of the telescopic arm beam lifting cylinder extends upward and its end is hinged to the telescopic arm beam.

5. The method for controllable increase of wall thickness of a metal circular tube based on diameter reduction according to claim 4, characterized in that, An extrusion tube removal platform is provided on one side of the lifting roller mechanism. The extrusion tube removal platform includes a base frame, a removal platform beam, a removal telescopic arm, a removal telescopic arm cylinder, and a stop block. The base frame is fixedly connected to the lower frame. Two parallel removal platform beams are fixedly connected to the top of the base frame. The extension direction of each removal platform beam is orthogonal to the arrangement direction of the lower guide wheel mechanism. A removal telescopic arm is slidably fitted inside each removal platform beam. One end of each removal telescopic arm is fixedly connected to the piston rod of a removal telescopic arm cylinder. The tail of each removal telescopic arm cylinder is fixedly connected to the corresponding removal platform beam. A stop block is fixedly connected to the top of the free end of each removal telescopic arm.

6. The method for controllable increase of wall thickness of a metal circular tube based on diameter reduction according to claim 5, characterized in that, The above-mentioned method for controllable increase of the wall thickness of metal circular tubes based on diameter reduction is implemented through the following steps: Step 1) Place multiple round tubes to be processed on the round tube feeding and transverse movement mechanism beforehand. When the first tube near the lower frame of the forming machine contacts the corresponding stop block, start the feeding assembly. The telescopic arm beam lifting cylinder lowers the telescopic arm beam until the U-shaped bracket is below the bottom of the round tube. Then start the telescopic arm cylinder so that the U-shaped bracket of the telescopic arm is below the first tube on the transverse movement frame beam. Raise the telescopic arm beam and the telescopic arm using the telescopic arm beam lifting cylinder, so that the U-shaped bracket lifts the first tube until the bottom of the round tube is above the corresponding stop block on the transverse movement frame beam. Then start the telescopic arm cylinder to send the round tube horizontally above the lower guide wheel. At this time, the round tube is called the pre-diameter reduction mother tube. As the lower guide wheel rises, the telescopic arm descends and retracts to the origin. The first feeding is completed. Step 2) The pre-diameter reduction tube is on the lower guide wheel and coaxial with the piston rod of the extrusion cylinder. Then, multiple upper guide wheels descend to press on the pre-diameter reduction tube; start the extrusion cylinder to drive the moving top plate to move at a constant speed. Step 3) When one end of the pre-reduction header enters the heater, the heater is started to heat the pre-reduction header. The heating temperature is set to 650-900℃. Step 4) The extrusion cylinder continues to push the pre-reduction tube forward. The heated pre-reduction tube is continuously pushed into the cavity of the hollow reduction mold. The round tube extruded from the cavity is the reduced round tube. The diameter of the pre-reduction tube entering the cavity is D1 and the wall thickness is t1. The diameter of the reduced round tube extruded from the cavity is D2 and the wall thickness is t2. Before extruding from the cavity, the damping cylinder is activated in advance to push the moving damping plate to move horizontally and uniformly towards the moving top plate until the positioning shaft head on the damping top rod is flush with the outlet of the hollow reduction mold. Step 5) The extrusion cylinder continues to push the front tube of the diameter reduction to move forward. When one end of the diameter reduction tube contacts the damping force application mechanism, the damping cylinder reverses and moves backward, controlling the backward speed of the moving damping plate to be slower than the forward speed of the moving top plate. Step 6) After a round tube is completely extruded from the reducing die, the extrusion cylinder returns to its original position, and the reduced-diameter round tube falls onto the roller of the lifting roller mechanism. The roller is raised, and the reduced-diameter round tube rolls along the inclined surface of the roller to the extruded round tube removal platform. The removal telescopic arm cylinder drives the removal telescopic arm to retract, bringing the reduced-diameter round tube onto the beam of the removal platform and close to the outer end.

7. The method for controllable increase of wall thickness of a metal circular tube based on diameter reduction according to claim 6, characterized in that, The maximum reduction ratio is D2 / D1=0.6, and the maximum increase ratio of wall thickness is t2 / t1=2.

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