Positive pressure inert atmosphere protection device and method for pipe end hot forming

Abstract

The embodiment of the invention discloses a positive pressure inert atmosphere protection device and method for pipe end hot forming. A pipe blank is clamped through a clamping block installed on a side push plate of a machine tool so that the pipe blank can be kept coaxial with a hot forming die in the hot forming process; the ejection block is arranged at the extrusion end of the pipe blank in a pressing manner and is used for introducing air into the pipe blank through a first ventilation pipe in the ejection block; a forming cavity is formed in a main die of the hot forming die, an annular air knife is installed at the front end of the main die in a sleeving mode, an annular gap air channel communicating with the forming cavity is formed through the annular air knife, and therefore high-pressure inert gas is introduced through the annular gap air channel and enters the forming cavity of the main die, and a pipe blank hot forming area is isolated from external air; and the surface of the formed pipe fitting is cooled. The problems that in the titanium alloy pull rod forming process, a titanium alloy material is prone to chemically reacting with oxygen and air components, so that a compound formed on the inner side of a pull rod part cannot be accurately removed, and the mechanical property of the part is affected are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to, but not limited to, the technical field of plastic forming, in particular to a positive pressure inert atmosphere protection device and method for pipe end hot forming. BACKGROUND

[0002] The pull rod in the aircraft control and lift system is a kind of tubular part often used, and the structural characteristics of the part are thin outer diameter and thick wall at both ends, thick outer diameter and thin wall in the middle, hollow in the inner cavity, and shuttle-shaped in appearance. Generally, internal threads are processed by using the thicker tube wall at both ends. The part with such structure has the characteristics of light weight, high strength, resistance to stretching, compression, twisting and bending; the part can bear static load and dynamic load during use, and since such part is often used for flight attitude control, it directly affects flight safety during flight, and is often defined as a key part or an important part. Based on the similar closed cavity structure of the part, the inner surface of the part cannot be reached by traditional mechanical processing means, and the organization fibers are cut off during mechanical processing, which is not conducive to achieving excellent mechanical properties of the part. Plastic processing can more easily obtain ideal part performance, and cold rotary forging or hot extrusion process method is generally used.

[0003] With the development of aircraft, the use of metal materials with low density and high strength is required for the preparation of pull rods, and titanium alloy is selected as the material for the preparation of aircraft pull rods due to its light weight, high strength and high compatibility. For titanium alloy, hot extrusion process is adopted, however, during the hot extrusion process of titanium alloy pull rod, the chemical properties of titanium alloy material are active at high temperature, and chemical reaction with oxygen and air components is easy to occur, thereby causing the formation of compounds on the inner side of the pull rod part, which cannot be accurately removed, affecting the mechanical properties of the part. SUMMARY

[0004] The purpose of the present application is to solve the above technical problems, and the present application provides a positive pressure inert atmosphere protection device and method for pipe end hot forming to solve the problem that during the hot extrusion process of titanium alloy pull rod, the chemical properties of titanium alloy material are active at high temperature, and chemical reaction with oxygen and air components is easy to occur, thereby causing the formation of compounds on the inner side of the pull rod part, which cannot be accurately removed, affecting the mechanical properties of the part.

[0005] The technical scheme of the present application: in the first aspect, the present application provides a positive pressure inert atmosphere protection device for pipe end hot forming, comprising: a top block 1, a clamping block 2 and a hot forming die 3; Wherein, the pipe blank 4 to be formed is clamped by the clamping block 2 installed on the side pushing plate of the machine tool, so as to stably maintain the coaxial position of the pipe blank 4 and the hot forming die 3 during the hot forming process; the top block 1 is tightly arranged at the extrusion end of the pipe blank 4, and is used for venting the pipe blank 4 through the first air pipe 5 in the top block 1 to discharge harmful gases in the pipe blank 4; The main mold 19 of the hot forming mold 3 is internally provided with a forming cavity for the end of the pipe, which is used as a pipe blank 4 forming surface, and the front end of the main mold 19 is provided with an annular air knife 14. The annular air knife 14 forms an annular gap air channel that is in communication with the forming cavity. High-pressure inert gas is introduced into the annular gap air channel through the second air pipe 22 arranged outside the annular air knife 14. The inert gas is pressurized and accelerated in the annular gap air channel, and then enters the forming cavity of the main mold 19, so that the pipe blank 4 hot forming area of the main mold 19 is isolated from the outside air, and the surface of the formed pipe is cooled.

[0006] Optionally, in the positive pressure inert atmosphere protection device for pipe end hot forming as described above, the hot forming mold 3 comprises: a main mold 19, an exhaust pipe 8, a mounting flange 9, a positioning ring 11, an electrically adjustable air door 13, an annular air knife 14, a positioning cylinder 15, a heat insulation pad 16, a heat preservation cylinder 17, and a heating coil 18; The main mold 19 comprises a cylindrical body part and an annular boss. The middle part of the cylindrical body part is provided with a forming cavity for the end of the pipe. The annular boss at the front end of the main mold 19 is sequentially arranged in close contact with the heat insulation pad 16, the annular air knife 14, and the electrically adjustable air door 13. The positioning cylinder 15 is sleeved and mounted outside the heat insulation pad 16, the annular air knife 14, and the electrically adjustable air door 13. The positioning cylinder 15 is tightly arranged at the end of the positioning ring 11, and the positioning ring 11 is tightly fixed with the annular boss at the front end of the main mold 19 by the third screw 12. The heating coil 18 and the heat preservation cylinder 17 are sequentially sleeved and mounted on the cylindrical body part of the main mold 19. The mounting flange 9 is tightly arranged at the rear end of the cylindrical body part of the main mold 19, and the mounting flange 9 and the main mold 19 are fixedly installed by the first screw 7. The exhaust pipe 8 in the mounting flange 9 is in communication with the forming cavity of the main mold 19, and is used to exhaust the gas inside the main mold 19. The second screw 10 installed through the mounting flange 9 is used to fixedly connect the whole hot forming mold 3 with the equipment head.

[0007] Optionally, in the positive pressure inert atmosphere protection device for pipe end hot forming as described above, the hot forming mold 3 further comprises a thermocouple 20. The thermocouple 20 is embedded and installed inside the mold body structure of the main mold 19, and is used to measure the mold body temperature during hot forming.

[0008] Optionally, in the positive pressure inert atmosphere protection device for pipe end hot forming as described above, the annular air knife 14 comprises two metal rings 21. Two metal rings 21 are provided with annular semicircular grooves on the inner side of the opposite end faces, and the inner side end face of the annular semicircular groove is thinned. One of the metal rings 21 is provided with a radial through hole communicating with the annular semicircular groove, and the outer end of the radial through hole is provided with a second air pipe 22. After the two metal rings 21 are butted, an annular air channel is formed on the inner side, and an annular gap channel is formed in the inner side through the thinned area, which communicates with the forming cavity of the main mold 19. The annular air knife 14 introduces high-pressure inert gas into the annular gap channel through the second air pipe 22, slows down and reduces pressure in the annular gap channel, and makes the high-pressure inert gas uniformly distributed inside the annular gap channel. After the inert gas is pressurized and accelerated in the annular gap channel, it enters the forming cavity of the main mold 19, so that the hot forming area of the pipe blank 4 entering the main mold 19 is isolated from the outside air, and the surface of the formed pipe is cooled.

[0009] Optionally, in the positive pressure inert atmosphere protection device for pipe end hot forming as described above, the electrically adjustable air door 13 is a metal servo adjustable diaphragm, which has the function of quantitatively adjusting the angle of each blade, so as to accurately control the opening and closing size of the air door 13 according to the size and position of the pipe blank 4.

[0010] Optionally, in the positive pressure inert atmosphere protection device for pipe end hot forming as described above, The top block 1 is formed by welding a T-shaped mold 6 and a first air pipe 5. The T-shaped mold 6 is installed on the tailstock of the machine tool, and the first air pipe 5 is connected to the inert gas cylinder connector by a hose. The clamping block 2 is composed of two semicircular molds with inner profiles conforming to the outer diameter of the pipe blank 4, and is installed on the side push plate of the machine tool.

[0011] In a second aspect, the embodiments of the present application also provide a positive pressure inert atmosphere protection method for pipe end hot forming, which is executed by using the positive pressure inert atmosphere protection device for pipe end hot forming as described in any one of the above embodiments, and comprises the following steps: Step 1: Before the hot extrusion forming process, the positive pressure inert atmosphere protection device is used to clamp and install the pipe blank 4, and high-pressure inert gas is introduced into the forming cavity of the pipe blank 4 and the hot forming mold 3; Step 2: The hot forming mold 3 is used to perform hot extrusion forming operation on the pipe blank 4; Step 3: The single-sided formed pipe blank 4 is demolded, and the air volume of the top block 1 is increased during the demolding process; Step 4: Steps 1 to 3 are repeated to perform hot extrusion forming on the other end of the pipe blank 4.

[0012] Optionally, in the positive pressure inert atmosphere protection method for pipe end hot forming, the step 1 comprises: Before the hot extrusion forming process, the pipe blank 4 is fixed by the clamp block 2, the main die 19 of the hot forming die 3 is heated to a preset temperature, the top block 1 contacts and presses the end face of the pipe blank 4, the high-pressure inert gas is introduced into the hot forming die 3 through the top block 1 and the hot forming die 3, when the hot forming die 3 moves to the pipe end of the pipe blank 4, the air door 13 at the front end of the hot forming die 3 is opened to be slightly larger than the outer diameter of the pipe blank 4, the hot forming die 3 continues to move until the pipe end of the pipe blank 4 reaches the position of the heat insulation pad 16, and the high-pressure inert gas is continuously introduced into the hot forming die 3 through the top block 1 and the annular air knife 14, so that the positive pressure air curtain is formed.

[0013] Optionally, in the positive pressure inert gas atmosphere protection method for pipe end hot forming, the step 2 comprises: The head carries the hot forming die 3 to move to the clamp block 2, the pipe blank 4 enters the forming cavity of the main die 19, with the movement of the hot forming die 3 to the clamp block 2, until the bottom of the cavity of the hot forming die 3, the end of the pipe blank 4 is gradually tapered and sealed with the forming cavity, and the inside of the pipe blank 4 is protected by inert gas.

[0014] Optionally, in the positive pressure inert gas atmosphere protection method for pipe end hot forming, the step 3 comprises: The head carries the hot forming die 3 to move away from the clamp block 2, and the pipe blank 4 is separated from the hot forming die 3; wherein, during the demolding process, the air amount of the top block 1 is increased, when the pipe blank 4 is passed through the air door 13, the air door 13 is gradually reduced, the positive pressure inert atmosphere in the hot forming die 3 is maintained, and when the pipe blank 4 is completely separated from the hot forming die 3, the top block 1 continuously ventilates until the temperature of the pipe blank 4 decreases to room temperature.

[0015] The beneficial effects of the present application: the embodiment of the present application provides a positive pressure inert gas atmosphere protection device and method for pipe end hot forming, the pipe blank 4 to be formed is clamped by the clamp block 2 installed on the side pushing plate of the machine tool, so that the pipe blank 4 is stably kept in the coaxial position with the hot forming die 3 during the hot forming process; the top block 1 is arranged to press the extruded end of the pipe blank 4, and is used for ventilating the pipe blank 4 through the first air pipe 5 in the top block 1 to discharge harmful gas in the pipe blank 4; the main die 19 of the hot forming die 3 is internally provided with a forming cavity for the end of the pipe, which is used as a forming surface of the pipe blank 4, and the annular air knife 14 is sleeved and installed at the front end of the main die 19, and the annular gap air channel communicated with the forming cavity is formed through the annular air knife 14, so that the high-pressure inert gas is introduced into the annular gap air channel through the second air pipe 22 arranged outside the annular air knife 14, the inert gas is pressurized and accelerated in the annular gap air channel region and then enters the forming cavity of the main die 19, so that the hot forming area of the pipe blank 4 entering the main die 19 is isolated from the outside air, and the surface of the formed pipe is cooled. The technical scheme provided by the present application for the pipe end hot forming of the titanium alloy pipe blank 4 has the following beneficial effects: Firstly, the pipe end hot forming positive pressure inert atmosphere protection scheme provided by the application is a new type of hot extrusion forming method based on mature machine tool research and development, has the characteristics of good effect, easy operation and low cost, and provides a technical implementation approach for upgrading materials and improving the performance of pull rods; Secondly, the pipe end hot forming positive pressure inert atmosphere protection scheme provided by the application provides an implementation scheme for realizing hot extrusion forming of titanium alloy pull rods. On the one hand, by adding the first ventilation pipe 5 on the top block 1, quantitative positive pressure inert gas protection is implemented to the inside of the pipe blank 4, the atmosphere inside the high-temperature pipe blank 4 is effectively protected, and the flowing inert gas is used to cool the pipe blank end during the demolding stage, thereby effectively avoiding the situation that the inside of the pipe blank cannot be accurately cleaned due to air corrosion caused by high temperature. On the other hand, by adding the air knife and the annular electrically adjustable air door 13 on the hot forming die 3, quantitative positive pressure inert gas protection and surface cooling of the high-temperature area on the outer surface of the pipe blank 4 are realized, thereby effectively slowing down the air corrosion of the outer surface of the pipe blank caused by high temperature and reducing the workload of subsequent corrosion cleaning. Thirdly, the pipe end hot forming positive pressure inert atmosphere protection scheme provided by the application provides a specific structure of the annular air knife. The air pipe is offset, which weakens the uneven pressure and flow of the exhaust port caused by the direct blowing of high-pressure gas to the air knife exhaust port. Further, the high-pressure gas is reduced in pressure by entering the large space air channel, can realize speed and pressure reduction in the annular air channel, and is distributed relatively uniformly at any position of the annular air channel. The inert gas is discharged to the inside of the annular channel at an increased speed and pressure.

[0016] Fourthly, the pipe end hot forming positive pressure inert atmosphere protection scheme provided by the application provides a composite hot forming die structure. By planning the relationship and position of the thermocouple, the exhaust nozzle, the heating coil, the mounting flange, the heat insulation pad, the annular air knife and the electrically adjustable air door, temperature accurate control, high and low temperature working area isolation and inert gas entering and excluding functions are realized, and low energy consumption and high efficiency titanium alloy pull rod hot extrusion forming can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the technical scheme of the application, and constitute a part of the specification, and are used together with the embodiments of the application to explain the technical scheme of the application, and do not constitute a limitation on the technical scheme of the application.

[0018] Figure 1 A schematic diagram of the overall structure of the positive pressure inert atmosphere protection device for pipe end hot forming provided by the embodiment of the application is shown in the figure. Figure 2 The structure of the positive pressure inert atmosphere protection device for pipe end hot forming provided by the embodiment shown in the figure is shown in the figure. Figure 1 The structure of the positive pressure inert atmosphere protection device for pipe end hot forming provided by the embodiment shown in the figure is shown in the figure. Figure 3 The structure of the positive pressure inert atmosphere protection device for pipe end hot forming provided by the embodiment shown in the figure is shown in the figure. Figure 1The embodiment shown provides a structure diagram of a hot forming die in a positive pressure inert atmosphere protection device for tube end hot forming; Figure 4 For Figure 3 The embodiment shown provides a specific enlarged diagram of a ring-shaped air knife in a hot forming die; Figure 5 For Figure 4 The embodiment shown provides a three-dimensional structure diagram of a ring-shaped air knife; Figure 6 The embodiment shown provides a schematic diagram of a positive pressure inert atmosphere protection device for performing a tube blank hot extrusion forming preparation; Figure 7 The embodiment shown provides a schematic diagram of a positive pressure inert atmosphere protection device for performing a tube blank hot extrusion forming operation; Figure 8 The embodiment shown provides a schematic diagram of a positive pressure inert atmosphere protection device for performing a tube blank demolding operation.

[0019] Marked for explanation: 1, top block; 2, clamping block; 3, hot forming die; 4, tube blank; 5, first air pipe; 6, T-shaped die; 7, first screw; 8, exhaust pipe; 9, mounting flange; 10, second screw; 11, positioning ring; 12, third screw; 13, air door; 14, ring-shaped air knife; 15, positioning cylinder; 16, heat insulation pad; 17, heat preservation cylinder; 18, heating coil; 19, main die; 20, thermocouple; 21, metal ring; 22, second air pipe. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be described in detail below with reference to the drawings. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0021] As explained in the above background, the pull rod in the aircraft control and lift system is difficult to be manufactured by machining, and currently cold spinning or hot extrusion process method is used.

[0022] The cold spinning process method is to adjust the forging direction by self-rotation around the tube axis while the multi-petal closing die forgings the tube blank radially. Because there is a repeated torsional force on the pull rod during the spinning process, in order to avoid the torsional force causing the tube blank to lose stability, this method is generally used for forming thick-walled short shaft pull rods made of aluminum alloy and stainless steel materials.

[0023] Hot extrusion process is a forming method of using the characteristics of high temperature strength reduction and plasticity improvement of metal materials, by applying axial force to the tube blank, so that the tube blank enters the forming die, thereby forming a shuttle-shaped structure, which is suitable for forming pull rods of aluminum alloy and other materials with high temperature stability.

[0024] Currently, the tube blank used for pull rod forming is generally prepared by aluminum alloy and stainless steel pipe material. However, with the increase of aircraft tonnage and subsystem load, the characteristics of traditional materials such as light weight and high strength cannot meet the service requirements, and it is urgent to select a metal material with low density and high strength to replace the existing aluminum alloy and stainless steel pipe material. According to public data, the yield strength of aluminum alloy (quenching) is about 255 MPa, the density is 2.8 g / cm 3 ; the yield strength of titanium alloy (annealing) is about 825 MPa, the density is 4.44 g / cm 3 ; the yield strength of stainless steel (cold hardening) is about 880 MPa, the density is 7.85 g / cm 3 . It can be seen that titanium alloy is a metal material with high compatibility of light weight and high strength, which is very suitable for application in complex high-load working conditions such as pull rod.

[0025] However, due to the high strength and low plasticity of titanium alloy at room temperature, large deformation in the cold spinning forming process will cause cracks in the titanium alloy pull rod. When titanium alloy is heated to above 700℃, the material deformation resistance is greatly reduced, and the plasticity is greatly improved. It is feasible to form titanium alloy pull rod by hot extrusion process. However, titanium alloy has active chemical properties at high temperature, and is easy to react with oxygen and air components. Especially, the compound formed on the inside of the pull rod part cannot be accurately removed, which seriously affects the mechanical properties of the part.

[0026] In view of the above problems, the embodiment of the present application provides a positive pressure inert atmosphere protection device and method for tube end hot forming. The present application aims to establish an inert atmosphere protection scheme for titanium alloy pull rod tube end heating and extrusion process, so as to isolate the titanium alloy material in the high heat area from the air, realize the quantitative positive pressure inert gas protection and surface cooling of the high temperature area of the tube blank outer surface, effectively slow down the corrosion of the tube blank outer surface due to high temperature, and reduce the workload of subsequent corrosion cleaning. Especially, the inside material of the titanium alloy pull rod after forming does not need to be treated with corrosion.

[0027] The following specific embodiments provided by the present application can be combined with each other, and the same or similar concepts or processes may not be described in some embodiments.

[0028] Figure 1 The overall structure diagram of a positive pressure inert atmosphere protection device for tube end hot forming provided by the embodiment of the present application is shown in the figure, Figure 2 The overall structure diagram of a positive pressure inert atmosphere protection device for tube end hot forming provided by the embodiment of the present application is shown in the figure, Figure 1The illustrated embodiment provides a schematic diagram of the top block in a positive pressure inert atmosphere protection device for pipe end thermoforming. Figure 3 for Figure 1 The illustrated embodiment provides a schematic diagram of the structure of the thermoforming die in a positive pressure inert atmosphere protection device for pipe end thermoforming; the above... Figures 1 to 3 All are half-section diagrams. (Refer to...) Figures 1 to 3 As shown, the main structure of the positive pressure inert atmosphere protection device for pipe end thermoforming provided in this embodiment of the invention includes three parts: top block 1, clamping block 2 and thermoforming mold 3.

[0029] like Figures 1 to 3 As shown, the tube blank 4 to be formed is clamped by the clamping block 2 installed on the side push plate of the machine tool to maintain a stable coaxial position with the thermoforming mold 3 during the thermoforming process; the top block 1 is pressed and set at the extrusion end of the tube blank 4, and is used to vent air into the tube blank 4 through the first vent pipe 5 in the top block 1 to discharge harmful gases in the tube blank 4.

[0030] In this embodiment of the invention, the top block 1 is formed by welding a T-shaped mold 6 and a first vent pipe 5. The T-shaped mold 6 is installed on the tailstock of the machine tool, and the first vent pipe 5 is connected to the inert gas cylinder nozzle by a flexible hose. The clamping block 2 is composed of two semi-circular molds whose inner surfaces conform to the outer diameter of the tube blank 4, and is installed on the side push plate of the machine tool.

[0031] In this embodiment of the invention, the main mold 19 of the thermoforming mold 3 has a forming cavity for the end of the pipe, which serves as the forming surface of the pipe blank 4. An annular air knife 14 is fitted and installed at the front end of the main mold 19. The annular air knife 14 forms an annular gap air channel that communicates with the forming cavity. High-pressure inert gas is introduced into the annular gap air channel through the second vent pipe 22 provided outside the annular air knife 14. The inert gas is pressurized and accelerated in the annular gap air channel area and then enters the forming cavity of the main mold 19, thereby isolating the hot forming area of ​​the pipe blank 4 entering the main mold 19 from the outside air and cooling the surface of the formed pipe.

[0032] In one implementation of this invention, such as Figure 3 As shown, the thermoforming mold 3 includes: a main mold 19, an exhaust pipe 8, a mounting flange 9, a positioning ring 11, an electrically adjustable damper 13, an annular air knife 14, a positioning cylinder 15, a heat insulation pad 16, a heat insulation cylinder 17, and a heating coil 18.

[0033] In the implementation, the main mold 19 comprises a cylindrical main body and an annular boss, a middle part of the cylindrical main body is provided with a shaped cavity for the end of the pipe, the annular boss at the front end of the main mold 19 is sequentially tightly arranged with the heat insulation pad 16, the annular air knife 14 and the electrically adjustable air door 13, and the positioning cylinder 15 is sleeved and arranged outside the heat insulation pad 16, the annular air knife 14 and the electrically adjustable air door 13, the end of the positioning cylinder 15 is tightly arranged with the positioning ring 11, and the positioning ring 11 and the annular boss at the front end of the main mold 19 are tightly fixed by the third screw 12; the heating coil 18 and the heat preservation cylinder 17 are sequentially sleeved and arranged on the cylindrical main body of the main mold 19, the mounting flange 9 is tightly arranged at the rear end of the cylindrical main body of the main mold 19, and the mounting flange 9 and the main mold 19 are fixedly arranged by the first screw 7, the exhaust pipe 8 communicating with the shaped cavity of the main mold 19 is arranged in the mounting flange 9, and is used for exhausting the gas in the main mold 19; in addition, the second screw 10 arranged around the mounting flange 9 is used for fixedly connecting the whole hot forming mold 3 with the equipment head.

[0034] Further, the hot forming mold 3 provided by the implementation further comprises a thermocouple 20; the thermocouple 20 is embedded and arranged in the mold body structure of the main mold 19, and is used for measuring the mold body temperature in the hot forming process.

[0035] In one specific embodiment of the implementation, as shown in Figure 4 The annular air knife 14 comprises two metal rings 21.

[0036] In the specific embodiment, the inner side of the opposite end faces of the two metal rings 21 is provided with an annular semicircular groove, the inner side end face of the annular semicircular groove is thinned, a radial through hole is arranged on one of the metal rings 21 and communicates with the annular semicircular groove, and the outer end of the radial through hole is provided with a second air pipe 22; after the two metal rings 21 are abutted, an annular air channel is formed at the inner side, and an annular gap channel is formed at the inner side of the annular air channel through the thinned area, and the annular gap channel communicates with the shaped cavity of the main mold 19.

[0037] In the specific embodiment, the annular air knife 14 introduces high-pressure inert gas through the second air pipe 22, slows down and depressurizes in the annular gap channel, so that the high-pressure inert gas is uniformly distributed in the annular gap channel, and the inert gas is discharged from the shaped cavity of the main mold 19 after being pressurized and accelerated in the annular gap channel, so that the hot forming area of the pipe blank 4 entering the main mold 19 is isolated from the external air, and the surface of the formed pipe is cooled.

[0038] In one specific embodiment of the implementation, the electrically adjustable air door 13 is a metal servo adjustable diaphragm, has a function of quantitatively adjusting the angle of each blade, and thus accurately controls the opening and closing size of the air door 13 according to the size and position of the pipe blank 4.

[0039] Based on the pipe end hot forming positive pressure inert atmosphere protection device provided in the above-mentioned embodiments of the present application, the present application further provides a pipe end hot forming positive pressure inert atmosphere protection method using the above-mentioned positive pressure inert atmosphere protection device, comprising the following steps: Step 1, before the hot extrusion forming process, the pipe blank 4 is clamped and installed by using the positive pressure inert atmosphere protection device, and high-pressure inert gas is introduced into the pipe blank 4 and the forming cavity of the hot forming die 3; Step 2, the hot extrusion forming operation is performed on the pipe blank 4 by using the hot forming die 3; Step 3, the single-sided formed pipe blank 4 is demolded, and the air flow of the ejector block 1 is increased during the demolding process; Step 4, steps 1 to 3 are repeated to perform hot extrusion forming on the other end of the pipe blank 4.

[0040] The pipe end hot forming positive pressure inert atmosphere protection device and method provided in the present application, the pipe blank 4 to be formed is clamped by the clamping block 2 installed on the side pushing plate of the machine tool, so that the pipe blank 4 is stably maintained in the coaxial position with the hot forming die 3 during the hot forming process; the ejector block 1 is tightly arranged at the extrusion end of the pipe blank 4, and is used for introducing air into the pipe blank 4 through the first air pipe 5 in the ejector block 1 to discharge harmful gas in the pipe blank 4; the main die 19 of the hot forming die 3 is internally provided with a forming cavity for the end of the pipe, which serves as a forming surface of the pipe blank 4, and the annular air knife 14 is sleeved and installed at the front end of the main die 19, an annular gap air channel is formed in communication with the forming cavity through the annular air knife 14, so that high-pressure inert gas is introduced into the annular gap air channel through the second air pipe 22 arranged outside the annular air knife 14, the inert gas is pressurized and accelerated in the annular gap air channel region and then enters the forming cavity of the main die 19, so that the pipe blank 4 entering the hot forming area of the main die 19 is isolated from the external air, and the surface of the formed pipe is cooled. The technical solution provided in the present application for the pipe end hot forming of the titanium alloy pipe blank 4 has the following beneficial effects: First, the pipe end hot forming positive pressure inert atmosphere protection scheme provided in the present application is a new hot extrusion forming method based on mature machine tools, which has the characteristics of good effect, easy operation and low cost, and provides a technical implementation approach for improving the performance of the pull rod by upgrading the material; Secondly, the hot forming positive pressure inert atmosphere protection scheme for tube ends provided by the present invention provides an implementation scheme for hot extrusion forming of titanium alloy tie rods. On the one hand, by adding a first ventilation pipe 5 to the top block 1, a quantitative positive pressure inert gas is applied to the inside of the tube blank 4 to protect it, effectively protecting the interior of the high-temperature tube blank 4 with an atmosphere. During the demolding stage, the flowing inert gas is used to cool the end of the tube blank, effectively avoiding the situation where the inside of the tube blank cannot be accurately cleaned due to air corrosion caused by high temperature. On the other hand, by adding an air knife and an adjustable air damper 13 of annular electric motor 14 to the hot forming mold 3, a quantitative positive pressure inert gas protection and surface cooling of the high-temperature area on the outer surface of the tube blank 4 are achieved, effectively mitigating the corrosion of the outer surface of the tube blank due to high temperature and reducing the workload of subsequent corrosion cleaning. Third, the tube end thermoforming positive pressure inert atmosphere protection scheme provided by the present invention provides a specific structure of an annular air knife; the vent pipe is offset, which reduces the uneven pressure and flow of the exhaust port caused by the high pressure gas blowing directly into the exhaust port of the air knife; further, the high pressure gas is depressurized by entering the large space air passage, and can be depressurized and decelerated in the annular air passage, and is distributed relatively evenly at any position in the annular air passage, and the inert gas is pressurized and accelerated at the inner gap and discharged to the inner side of the annulus.

[0041] Fourth, the pipe end thermoforming positive pressure inert atmosphere protection scheme provided by the present invention provides a composite thermoforming mold structure. By planning the relationship and position of thermocouples, exhaust nozzles, heating coils, mounting flanges, heat insulation pads, annular air knives and electrically adjustable dampers, it realizes precise temperature control, isolation of high and low temperature working areas and inert gas entry and exit functions, and can realize low energy consumption and high efficiency titanium alloy tie rod hot extrusion forming.

[0042] The following is an illustrative description of the implementation of the positive pressure inert atmosphere protection device and method for pipe end thermoforming provided in this invention, through an embodiment example.

[0043] Implementation Example I. Structure and Composition of Positive Pressure Inert Atmosphere Protection Device like Figures 1 to 5 As shown, the positive pressure inert atmosphere protection device provided in this embodiment mainly consists of three parts: top block 1, clamping block 2, and thermoforming mold 3.

[0044] The top block 1 is used to prevent the tube blank 4 from axially displacing under forming force, reduce the radial pressure on the tube blank 4 when the clamping block 2 clamps the tube blank 4, avoid radial clamping and axial scratches on the tube blank 4, and provide a passage for filling the tube blank 4 with inert gas. The top block 1 is welded from a T-shaped mold 6 and a first vent pipe 5. The T-shaped mold 6 is mounted on the tailstock of the machine tool, and the first vent pipe 5 is connected to the inert gas cylinder nozzle by a hose.

[0045] The clamp block 2 is used to clamp the pipe blank 4 to enable the pipe blank 4 to be stably held in a coaxial position with the hot forming die 3. The clamp block 2 is composed of two semicircular dies with inner profiles conforming to the outer diameter of the pipe blank 4, which are installed on the side push plate of the machine tool.

[0046] The hot forming die 3 is used to heat form the pipe blank 4, provide a pipe blank 4 forming profile and a positive pressure inert gas atmosphere space, and cool the formed pipe blank 4 by air cooling. The hot forming die 3 is integrally installed with a thermocouple 20, an exhaust pipe 8, a heating coil 18, a mounting flange 9, a heat insulation pad 16, an annular air knife 14, an electrically adjustable air door 13 and a positioning ring 11. As shown in Figure 3

[0047] In the hot forming die 3 provided by the embodiment, the main die 19 is made of high-temperature-resistant metal material, for example, H13 die steel can be selected as the die material of the main die 19. The front end of the main die 19 is sequentially installed with the heat insulation pad 16, the annular air knife 14 and the electrically adjustable air door 13. The positioning cylinder 15 is sleeved and installed outside the heat insulation pad 16, the annular air knife 14 and the electrically adjustable air door 13. The end of the positioning cylinder 15 is pressed against the positioning ring 11, and the positioning ring 11 is fastened with the annular boss at the front end of the main die 19 by the third screw 12. The mounting flange 9 is welded with the exhaust pipe 8 for air exhaust inside the main die 19. The tail end of the main die 19 is sequentially sleeved into the heating coil 18 and the heat preservation cylinder 17, and the main die 19 is fixedly connected with the mounting flange 9 at the rear end thereof by the first screw 7. After the thermocouple 20 is inserted, the mounting flange 9 is connected with the machine head of the equipment by the second screw 10.

[0048] In the embodiment, the annular air knife 14 is composed of two metal rings 21. Each metal ring is processed with a semicircular air channel on the inner side, and is thinned by 0.1mm towards the inner diameter on the edge of the air channel, to form an annular gap air channel in communication with the forming cavity of the main die 19. One of the metal rings 21 is punched from the outer diameter air channel and welded with the second air pipe 22. The second air pipe 22 is connected with the inert gas cylinder connector by a hose. After the air channels of the two metal rings 21 are matched, high-pressure inert gas is introduced into the annular gap air channel through the second air pipe 22, and is slowed down and decompressed in the annular gap air channel, so that the high-pressure inert gas is uniformly distributed at any position of the annular gap air channel. Due to the difference in pressure side force inside and outside the annular air channel, the inert gas is discharged to the inside of the annular gap air channel after being pressurized and accelerated at the inner annular gap air channel, and enters the forming cavity of the main die 19, so as to isolate the hot forming area of the pipe blank 4 from the outside air, and cool the surface of the formed pipe.

[0049] In the embodiment, the electrically adjustable air door 13 is a commercially available metal servo adjustable diaphragm which is modified for use. The angle of each blade can be quantitatively adjusted according to the size and position of the pipe blank 4.

[0050] II. Working process of hot extrusion forming of titanium alloy pipe blank 4 ​(2.1) Preparation before hot extrusion forming of titanium alloy tube blank 4 Figure 6 The schematic diagram for performing the preparation before hot extrusion forming of the tube blank by the positive pressure inert atmosphere protection device provided by the embodiment of the present application is shown.

[0051] As shown in Figure 6 , the equipment head carries the hot forming die 3, and the tailstock carries the top block 1 to move away from each other. The side push plate carries the clamping block 2 in the open and closed state. The electric heating coil 18 is powered on, and the thermocouple 20 is powered on to detect the temperature of the main die 19, so that the temperature of the main die 19 is maintained at 720-760℃. The electrically adjustable air door 13 is adjusted to the minimum. The first air pipe 5 of the top block 1 is connected to the inert gas cylinder, and the air volume is adjusted to 5-10L / min. The second air pipe 22 of the hot forming die 3 is connected to the inert gas cylinder, and the air volume is adjusted to 10-20L / min. The tube blank 4 is placed in the clamping block 2, and the clamping block 2 is closed. The top block 1 contacts and presses the end face of the tube blank 4. The inert gas flows from one end of the tube blank 4 to the other end, and the air is discharged. The air in the hot forming die 3 is also diluted by the inert gas until a stable state is reached.

[0052] The head carries the hot forming die 3 to move towards the clamping block 2. When approaching the tube end of the tube blank 4, the air door 13 is opened to a size slightly larger than the outer diameter of the tube blank 4. The hot forming die 3 continues to move until the tube end of the tube blank 4 reaches the position of the heat insulation pad 16, and the hot forming die 3 stops moving. In order to further exhaust the air in the hot forming die 3, the inert gas is continuously introduced into the hot forming die 3 through the tube blank 4 for 5-10s at this time. The annular air knife 14 continuously blows high-pressure inert gas inward to form a positive pressure air curtain barrier, which is used to avoid air entering and corroding the metal on the outside of the tube blank 4, and at the same time achieves the cooling effect of the non-forming area of the tube blank 4, avoiding the air corrosion caused by the overheating of the tube blank 4 outside the air door 13 due to heat conduction.

[0053] (2.2) Hot extrusion forming operation of titanium alloy tube blank 4 Figure 7 The schematic diagram for performing the hot extrusion forming operation of the tube blank by the positive pressure inert atmosphere protection device provided by the embodiment of the present application is shown.

[0054] As shown in Figure 7 , the head carries the hot forming die 3 to move towards the clamping block 2. The tube blank 4 enters the forming cavity of the main die 19. Due to the constraint and heat conduction of the forming cavity, the strength of the tube blank 4 decreases and the plasticity increases. With the movement of the hot forming die 3 towards the clamping block 2, until the cavity bottom of the hot forming die 3 is reached, the end of the tube blank 4 is gradually thinned and forms a seal with the forming cavity. The inside of the tube blank 4 is protected by inert gas and cannot be in contact with air, which isolates the conditions for air corrosion of titanium alloy.

[0055] (2.3) Demolding operation of the tube blank 4 after unilateral forming Figure 8 A schematic diagram of the positive pressure inert atmosphere protection device provided by the embodiment of the present application performing the pipe blank demolding operation.

[0056] As shown in Figure 8 , the head carries the hot forming die 3 to move away from the clamping block 2, and the pipe blank 4 is separated from the hot forming die 3. In order to accelerate the cooling of the pipe blank 4, and avoid the pipe blank 4 in a hot state (300℃) contacting air to cause corrosion, the air flow of the top block 1 needs to be increased to 20-30L / min. With the pipe blank 4 slowly (2-7mm / s) moving out of the hot forming die 3, when the pipe blank 4 passes through the damper 13, the damper 13 gradually narrows, maintaining the positive pressure inert atmosphere in the forming die, avoiding air entering. When the pipe blank 4 is completely separated from the hot forming die 3, the top block 1 continues to ventilate until the temperature of the pipe blank 4 drops to room temperature.

[0057] (2.4) Double-sided hot extrusion forming of the titanium alloy pipe blank 4.

[0058] Open the clamping block 2, take out the pipe blank 4, and replace the pipe blank 4 in the direction of the unformed end towards the hot forming die. According to steps two to four, the other side pipe end processing is completed, thereby realizing the double-sided hot extrusion forming of the pipe blank 4.

[0059] Although the embodiments of the present application are disclosed as above, the content is only the embodiment adopted for the purpose of facilitating the understanding of the present application, and is not used to limit the present application. Any person skilled in the art of the present application can make any modification and change in the implementation form and details without departing from the spirit and scope of the present application disclosed, but the patent protection scope of the present application shall be subject to the scope defined by the appended claims.

Claims

1. A positive pressure inert atmosphere protection device for pipe end thermoforming, characterized in that, include: Top block (1), clamping block (2) and thermoforming mold (3); The tube blank (4) to be formed is clamped by a clamping block (2) installed on the side push plate of the machine tool so as to keep the tube blank (4) stably coaxial with the thermoforming die (3) during the thermoforming process; the top block (1) is pressed and set at the extrusion end of the tube blank (4) for passing air into the tube blank (4) through the first vent pipe (5) in the top block (1) to discharge harmful gases in the tube blank (4); The main mold (19) of the thermoforming mold (3) has a forming cavity for the end of the pipe, which serves as the forming surface of the pipe blank (4). An annular air knife (14) is fitted at the front end of the main mold (19). An annular gap air channel is formed by the annular air knife (14) and communicates with the forming cavity. High-pressure inert gas is introduced into the annular gap air channel through the second air pipe (22) set outside the annular air knife (14). The inert gas is pressurized and accelerated in the annular gap air channel area and then enters the forming cavity of the main mold (19), thereby isolating the hot forming area of ​​the pipe blank (4) entering the main mold (19) from the outside air and cooling the surface of the formed pipe.

2. The positive pressure inert atmosphere protection device for pipe end thermoforming according to claim 1, characterized in that, The thermoforming mold (3) includes: a main mold (19), an exhaust pipe (8), a mounting flange (9), a positioning ring (11), an electrically adjustable damper (13), an annular air knife (14), a positioning cylinder (15), a heat insulation pad (16), a heat insulation cylinder (17), and a heating coil (18). The main mold (19) includes a columnar main body and an annular boss. The columnar main body has a forming cavity for the end of the pipe fitting in the middle. The annular boss at the front end of the main mold (19) is fitted with a heat insulation pad (16), an annular air knife (14) and an electrically adjustable damper (13) in sequence. A positioning cylinder (15) is sleeved and installed on the outside of the heat insulation pad (16), the annular air knife (14) and the electrically adjustable damper (13). A positioning ring (11) is pressed against the end of the positioning cylinder (15). A third screw (12) is used to connect the positioning ring (11) to the front end of the main mold (19). The annular boss is pressed and fixed; a heating coil (18) and a heat preservation cylinder (17) are sequentially installed on the columnar main body of the main mold (19). The mounting flange (9) is pressed and set at the rear end of the columnar main body of the main mold (19), and the mounting flange (9) and the main mold (19) are fixed by the first screw (7). The mounting flange (9) is provided with an exhaust pipe (8) connected to the forming cavity of the main mold (19) to discharge the gas inside the main mold (19); the overall thermoforming mold (3) is fixedly connected to the machine head of the equipment by the second screw (10) installed around the mounting flange (9).

3. A positive pressure inert atmosphere protection device for pipe end thermoforming according to claim 2, characterized in that, The thermoforming mold (3) further includes: a thermocouple (20); The thermocouple (20) is embedded in the mold structure of the main mold (19) and is used to measure the mold temperature during the thermoforming process.

4. A positive pressure inert atmosphere protection device for pipe end thermoforming according to claim 2, characterized in that, The annular air knife (14) includes two metal rings (21). Among them, an annular semicircular groove is provided on the inner side of the opposite end face of the two metal rings (21), the inner end face of the annular semicircular groove is thinned, and a radial through hole is provided on one of the metal rings (21) to communicate with its annular semicircular groove, and a second vent pipe (22) is provided at the outer end of the radial through hole; after the two metal rings (21) are joined together, an annular air passage is formed on the inner side, and an annular gap air passage is formed on the inner side of the annular air passage through the thinned area, which is connected to the forming cavity of the main mold (19); The annular air knife (14) introduces high-pressure inert gas into the annular slit air passage through the second vent pipe (22). The gas is decelerated and depressurized in the annular slit air passage, so that the high-pressure inert gas is evenly distributed inside the annular slit air passage. After the inert gas is pressurized and accelerated in the annular slit air passage area, it enters the forming cavity of the main mold (19), thereby isolating the hot forming zone of the tube blank (4) entering the main mold (19) from the outside air and cooling the surface of the formed tube.

5. A positive pressure inert atmosphere protection device for pipe end thermoforming according to claim 2, characterized in that, The electrically adjustable damper (13) is a metal servo adjustable aperture, which has the function of quantitatively adjusting the angle of each blade, thereby precisely controlling the opening and closing size of the damper (13) according to the size and position of the tube blank (4).

6. A positive pressure inert atmosphere protection device for pipe end thermoforming according to any one of claims 1 to 5, characterized in that, The top block (1) is formed by welding a T-shaped mold (6) and a first vent pipe (5). The T-shaped mold (6) is installed on the tailstock of the machine tool, and the first vent pipe (5) is connected to the inert gas cylinder nozzle by a hose. The clamping block (2) consists of two semi-circular molds whose inner surfaces conform to the outer diameter of the tube blank (4) and is installed on the side push plate of the machine tool.

7. A method for positive pressure inert atmosphere protection during pipe end thermoforming, characterized in that, The method for performing positive pressure inert atmosphere protection for pipe end hot forming using the positive pressure inert atmosphere protection device for pipe end hot forming as described in any one of claims 1 to 6 includes: Step 1: Before the hot extrusion forming process, a positive pressure inert atmosphere protection device is used to clamp and install the tube blank (4), and high pressure inert gas is introduced into the forming cavity of the tube blank (4) and the hot forming die (3); Step 2: The tube blank (4) is subjected to hot extrusion forming operation using a thermoforming die (3); Step 3: Demold the tube blank (4) after it has been formed on one side. During the demolding process, increase the air flow of the top block (1). Step 4: Repeat steps 1 to 3 to hot extrude the other end of the tube blank (4).

8. The positive pressure inert atmosphere protection method for pipe end thermoforming according to claim 7, characterized in that, Step 1 includes: Before the hot extrusion forming process, the tube blank (4) is fixed by the clamping block (2), and its main mold (19) is heated by the hot forming mold (3) to reach the preset temperature; the top block (1) contacts and presses the end face of the tube blank (4) and presses the end face of the tube blank (4), and high pressure inert gas is introduced by the top block (1) and the hot forming mold (3) at the same time; when the hot forming mold (3) moves to the tube end near the tube blank (4), the air door (13) at the front end of the hot forming mold (3) is opened to be slightly larger than the outer diameter of the tube blank (4), and the hot forming mold (3) continues to move until the tube end of the tube blank (4) reaches the position of the heat insulation pad (16); high pressure inert gas is continuously blown into the hot forming mold (3) through the top block (1) and the annular air knife (14) to form a positive pressure air curtain barrier.

9. The positive pressure inert atmosphere protection method for hot forming of pipe ends according to claim 7, characterized in that, Step 2 includes: The die head carries the thermoforming die (3) to the clamping block (2), and the tube blank (4) enters the forming cavity of the main die (19). As the thermoforming die (3) moves towards the clamping block (2), it reaches the bottom of the cavity of the thermoforming die (3). The end of the tube blank (4) gradually shrinks and forms a seal with the forming cavity. The inside of the tube blank (4) is protected by inert gas.

10. A positive pressure inert atmosphere protection method for pipe end thermoforming according to claim 7, characterized in that, Step 3 includes: The die head carries the thermoforming mold (3) and moves away from the clamping block (2), and the tube blank (4) separates from the thermoforming mold (3); during the demolding process, the air volume of the top block (1) is increased, and when the tube blank (4) passes through the air damper (13) in the diameter reduction area, the air damper (13) gradually shrinks to maintain a positive pressure inert atmosphere in the thermoforming mold (3). When the tube blank (4) is completely separated from the thermoforming mold (3), the top block (1) continues to ventilate until the temperature of the tube blank (4) drops to room temperature.

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