A method and device for ultra-low temperature plastic connection of aluminum alloy thin-walled conical tube and thin plate

Abstract

The present invention provides a method and device for ultra-low temperature plastic connection of aluminum alloy thin-walled conical tubes and thin plates, belonging to the technical field of light alloy tube-sheet connection. Aiming at the difficulty of efficient connection of aluminum alloy thin-walled conical tubes and thin plates, the conical tube and the prefabricated thin plate are clamped and positioned with a half-type pressure ring; by virtue of the ultra-low temperature deformation enhancement and plasticization characteristics of aluminum alloy, an ultra-low temperature medium is filled in the insulation tank, and the conical tube and the thin plate are cryogenically treated at the same time; the root of the conical tube is expanded in an ultra-low temperature environment by using an expanding punch, and the tube material is squeezed out of the center hole of the thin plate; the remaining material is pressed into the annular groove near the center hole on the lower surface of the thin plate by a rotating extrusion plate, so as to realize efficient connection of the aluminum alloy thin-walled conical tube and the thin plate. The present invention combines the expansion process of thin-walled conical tubes with the plastic connection process of conical tubes, and has the advantages of high efficiency and speed, green and environmental protection, high process integration, and good plastic joint quality.

Description

Technical Field

[0001] The invention belongs to the technical field of light alloy tube-sheet connection, and in particular relates to a method and a device for ultra-low temperature plastic connection of a thin-walled conical tube and a thin plate. Background Art

[0002] The connection between aluminum alloy thin-walled conical tubes and thin plates is mainly used to transmit low-temperature gaseous, liquid or gas-liquid coexisting media with pressure, and is widely used in important fields such as petroleum refining, chemical synthesis, natural gas transportation, and low-temperature fuel supply for aerospace vehicles. This type of joint has high requirements for its sealing and strength, and is usually connected by welding. However, the traditional fusion welding method is difficult to effectively connect joints with complex shapes such as thin-walled conical tubes and thin plates. There are disadvantages such as complex welding process, poor quality of circumferential welds, easy burning through and cracking of thin-walled structures, and low production efficiency. In order to solve the above defects, based on the characteristics of aluminum and aluminum alloys that the strength and elongation are significantly increased at ultra-low temperatures, the present invention provides an ultra-low temperature plastic connection method and device for aluminum alloy thin-walled conical tubes and thin plates. The connection method has the advantages of high efficiency and speed, high process integration, good joint quality, green environmental protection, and suitability for mass production.

[0003] Therefore, how to overcome the difficulties in the prior art, such as the difficulty in effectively connecting complex structures such as thin-walled conical tubes and thin plates, the complex welding process, poor quality of circumferential welds, easy burn-through and cracking of thin-walled structures, low production efficiency, and environmental pollution, has become an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0004] The present invention proposes a method and device for ultra-low temperature plastic connection of an aluminum alloy thin-walled conical tube and a thin plate, aiming to solve the problems existing in the prior art: the connection between the aluminum alloy thin-walled conical tube and the thin plate is a complex structural connection, and the welding process is complex; the thin wall is easy to burn and weld through, the weld is easy to crack, and the strength is low; the production efficiency is low and the environment is polluted.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is to propose a method and device for ultra-low temperature plastic connection of aluminum alloy thin-walled conical tube and thin plate. The device mainly comprises a flaring punch, a half-type blank holder, an extrusion plate, a conical tube, a thin plate, an ultra-low temperature cooling medium, a stainless steel insulation tank, a push plate, a support rod, a pad and other structures.

[0006] Before forming, the thin-walled conical tube and the thin plate with prefabricated center hole and annular groove are placed on the pad, and the half-type blank holder clamps the thin-walled conical tube and presses the thin plate with the center hole as a whole; the fixed thin plate and thin-walled conical tube are immersed and cooled by ultra-low temperature medium to reduce their temperature to below the ultra-low temperature critical transformation temperature (-150℃) of the material. At the same time, the push rod pushes the large-diameter extrusion plate to make it just contact with the lower surface of the thin plate blank; the expansion punch descends into the ultra-low temperature medium to cool, and then descends to extrude the thin-walled conical tube blank from the center hole of the thin plate, and expands the deep-cooled thin-walled conical tube; by rotating the push rod upward, the small-diameter extrusion plate is driven to rotate and the straight wall section of the thin-walled conical tube is reversely pressed into the annular groove near the center hole on the lower surface of the thin plate, realizing the plastic connection between the aluminum alloy thin-walled conical tube and the thin plate. The whole process can be divided into three stages: ultra-low temperature cooling stage, ultra-low temperature expansion stage, and ultra-low temperature plastic connection stage, which specifically includes the following steps:

[0007] Step 1: Open a center hole at the center of the thin plate according to the design requirements of the pipe diameter, and use a lathe to machine a concentric arc-shaped groove at the center hole position on the lower surface of the thin plate;

[0008] Step 2: Place the thin-walled conical tube and the slab with prefabricated center hole and prefabricated groove on the pad, and clamp the thin-walled conical tube with a half-type blank holder and press the thin plate with the center hole as a whole to form a closed cavity inside the thin-walled conical tube;

[0009] Step 3: Place the assembly of the half-type blank holder, thin-walled cone tube and thin plate into a stainless steel insulation tank, and position and fix them on the press;

[0010] Step 4: The hole-expanding punch moves down to the small opening inside the thin-walled conical tube, and coincides with the center of the half-type blank holder, the thin-walled conical tube, and the thin plate placed on the pad;

[0011] Step 5: Fill the stainless steel groove and the inner cavity of the thin-walled cone tube with ultra-low temperature medium to fill the entire closed cavity. At the same time, cool the hole expansion punch, thin-walled cone tube and thin plate as a whole to keep the temperature of the deformation zone of the tube and plate below the ultra-low temperature critical transition temperature (-150℃) of the material;

[0012] Step 6: Rotate the push rod to push the large-diameter extrusion plate upward until it just contacts the lower surface of the thin slab;

[0013] Step 7: The reaming punch moves downward to reame the cooled thin-walled conical tube and squeeze the tube material out of the center hole of the thin plate;

[0014] Step 8: Rotate the push rod upward, and the small-diameter extrusion plate rotates to press the tube material into the annular groove near the center hole on the lower surface of the thin plate, so as to achieve plastic connection between the aluminum alloy thin-walled cone tube and the thin plate;

[0015] Step 9: After the connection is completed, the hole expansion punch moves upward, and drives the assembly of the half-type blank holder, thin-walled cone tube, and thin plate to be moved out of the stainless steel insulation tank as a whole;

[0016] Step 10: Rotate the push rod back to its original position;

[0017] Step 11: Open the half-type blank holder, disassemble the thin-walled tapered tube and thin plate connector from the hole expansion punch and take out the parts; at the same time, provide personnel protection to prevent frostbite from residual ultra-low temperature cooling medium.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: a method and device for ultra-low temperature plastic connection of an aluminum alloy thin-walled conical tube and a thin plate are proposed, by fixing and centering the thin-walled conical tube and a thin plate with a prefabricated center hole and a bevel, and by utilizing the ultra-low temperature deformation enhancement and plasticization characteristics of the aluminum alloy, the tube material is first extruded from the center hole of the thin plate under an ultra-low temperature environment through an expanding punch, and the deep-cooled thin-walled conical tube is expanded; then, the small-diameter extrusion plate is driven to rotate by rotating the push rod, and the straight wall section of the thin-walled conical tube is reversely pressed into the annular groove near the center hole on the lower surface of the thin plate, thereby realizing the plastic connection between the aluminum alloy thin-walled conical tube and the thin plate. This method uses the plasticization and strengthening characteristics of materials in ultra-low temperature environments to solve the problem of connecting complex structures of aluminum alloy thin-walled conical tubes and thin plates; it combines the hole expansion of thin-walled conical tubes with the plastic connection process of thin-walled conical tubes into one, avoiding the problems of difficult operation of traditional girth welds, complex welding process, and low production efficiency; it can connect not only the same materials, but also dissimilar materials, and can overcome technical difficulties such as easy burning and penetration of traditional welding methods for thin tubes and thin plates, easy cracking of girth welds, and low joint strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solution of the method for ultra-low temperature plastic connection of aluminum alloy thin-walled conical tubes and thin plates implemented in the present invention, the descriptions in each implementation measurement will be briefly introduced using the accompanying drawings.

[0020] Figure 1 is the main reference numeral;

[0021] Figure 2 For connecting thin-walled conical tubes and thin plates;

[0022] Figure 3 It is the ultra-low temperature cooling stage;

[0023] Figure 4 It is the ultra-low temperature hole expansion stage;

[0024] Figure 5 It is the ultra-low temperature plastic connection stage;

[0025] Figure 6 It is an ultra-low temperature plastic connector for thin-walled conical tubes and thin plates.

[0026] Main figure marks: 1 push plate; 2 support rod; 3 extrusion plate; 4 stainless steel insulation tank; 5 ultra-low temperature cooling medium (liquid nitrogen); 6 half-type blank holder; 7 hole expansion punch; 8 thin-walled tapered tube; 9 thin plate; 10 pad; 11 sealing ring; 12 pad; 13 rotating push rod. DETAILED DESCRIPTION

[0027] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with the accompanying drawings.

[0028] See also Figure 1 .

[0029] The present invention provides a method and device for ultra-low temperature plastic connection of an aluminum alloy thin-walled conical tube and a thin plate 9. The method combines the expansion process of the thin-walled conical tube 8 and the plastic connection process of the thin-walled conical tube 8 into one by taking advantage of the ultra-low temperature deformation enhancement and plasticization characteristics of aluminum alloy. First, the tube material is extruded from the center hole of the thin plate 9 by the expansion punch 7 under ultra-low temperature environment, and the deep-cooled thin-walled conical tube 8 is expanded; then the small-diameter extrusion plate 3 is driven to rotate by rotating the push rod 13, and the straight wall section of the thin-walled conical tube 8 is reversely pressed into the annular groove near the center hole of the lower surface of the thin plate 9, so as to realize efficient plastic connection between the aluminum alloy thin-walled conical tube and the thin plate 9. The method can solve the problems of difficult operation of traditional girth welds, complex welding process, and low production efficiency, and can also overcome the difficulties of easy burning and penetration of traditional welding methods for thin tubes and thin plates 9, easy cracking of girth welds, and low strength of fusion welded joints.

[0030] The ultra-low temperature plastic connection device is basically composed of: a flaring punch 7, a half-type pressure ring 6, an extrusion plate 3, a thin-walled cone 8, a thin plate 9, an ultra-low temperature cooling medium (liquid nitrogen) 5, a stainless steel insulation tank 4, a push plate 1, a support rod 2, a pad 10 and other structures. The specific working steps of the device are as follows:

[0031] A center hole is opened at the center position of the thin plate 9 according to the design requirements of the pipe diameter, and a concentric arc-shaped groove is machined at the center hole position on the lower surface of the thin plate 9 by lathe to prefabricate the blank;

[0032] Place the thin-walled conical tube 8 and the thin plate 9 with prefabricated center hole and groove on the pad, and clamp the thin-walled conical tube and the thin plate 9 with the center hole as a whole by the half-type blank holder 6, so as to form a closed cavity inside the thin-walled conical tube 8;

[0033] Put the assembly of the half-type blank holder 6, the thin-walled cone tube 8 and the thin plate 9 into the stainless steel insulation tank 4, and position and fix it on the workbench of the press;

[0034] The hole-expanding punch 7 moves downward to the small opening of the thin-walled tapered tube 8, so that it coincides with the center of the half-type blank holder 6, the thin-walled tapered tube 8, and the thin plate 9 placed on the backing plate 10;

[0035] The stainless steel heat preservation tank 4 and the inner cavity of the thin-walled cone tube 8 are filled with ultra-low temperature cooling medium (liquid nitrogen) 5, so that it fills the entire cavity, and the mold components 3, 6, 7, 10, the thin-walled cone tube 8 and the thin plate 9 are cooled as a whole, so that the temperature of the deformation zone of the tube and the plate is maintained below the ultra-low temperature critical transition temperature;

[0036] The rotating push rod 13 pushes the large-diameter extrusion plate 3 upward to just contact the lower surface of the thin plate 9;

[0037] The hole-expanding punch 7 moves downward and expands the cooled thin-walled tapered tube 8, and squeezes the tube material out of the center hole of the thin plate 9;

[0038] The push rod 13 is rotated upward, and the straight wall section of the thin-walled conical tube 8 is reversely rotated and pressed into the annular groove near the center hole on the lower surface of the thin plate 9 by replacing the small-diameter extrusion plate 3, so as to realize the plastic connection between the thin-walled conical tube 8 and the thin plate 9;

[0039] After the plastic connection is completed, the hole-expanding punch 7 moves upward, and drives the assembly of the half-type blank holder 6, the thin-walled cone tube 8, and the thin plate 9 to be moved out of the stainless steel insulation tank 4 as a whole;

[0040] The rotating push rod 13 drives the small-diameter extrusion plate 3 to return to its original position;

[0041] Open the half-type blank holder 6, disassemble the connector of the thin-walled conical tube 8 and the thin plate 9 from the hole expansion punch 7, and take out the plastic connector. At the same time, protect personnel to prevent frostbite caused by the residual ultra-low temperature cooling medium (liquid nitrogen) 5.

[0042] Example

[0043] The implementation process of ultra-low temperature plastic connection between thin-walled conical tube 8 and thin plate 9 is shown in Figure 2 , Figure 3 , Figure 4 and Figure 5 .

[0044] The material of the thin-walled cone tube 8 is AA6061 aluminum alloy. Taking the ultra-low temperature plastic connection of the thin-walled cone tube 8 and the thin plate 9 as an example, Figure 2 As shown, the average thickness of the thin-walled cone tube 8 is 1.2 mm, the thickness of the thin plate 9 is 2.5 mm, the depth of the arc-shaped groove is 1.2 mm, and the number of the arc-shaped grooves is 3 circles.

[0045] Ultra-low temperature liquid nitrogen cooling stage, such as Figure 3 shown.

[0046] Ultra-low temperature expansion stage, such as Figure 4 shown.

[0047] Ultra-low temperature plastic connection stage, such as Figure 5 shown.

[0048] By taking advantage of the ultra-low temperature deformation enhancement and plasticization characteristics of aluminum alloy, by fixing the thin-walled conical tube 8 and the thin plate 9 with prefabricated center hole and groove, the tube material is first extruded from the center hole of the thin plate 9 by the punch 7 under ultra-low temperature environment, and the deep-cooled thin-walled conical tube 8 is expanded; then the small-diameter extrusion plate 3 is driven to rotate by rotating the push rod 13, and the straight wall section of the thin-walled conical tube 8 is reversely pressed into the annular groove near the center hole on the lower surface of the thin plate 9, so as to realize the efficient plastic connection between the thin-walled conical tube 8 and the thin plate 9, as shown in FIG. Figure 6 shown.

[0049] In summary, the embodiment of the present invention provides a method and device for ultra-low temperature plastic connection of aluminum alloy thin-walled conical tube and thin plate 9. This method combines the expansion of the thin-walled conical tube 8 and the plastic connection process of the thin-walled conical tube 8 into one by taking advantage of the plasticization and strengthening characteristics of aluminum alloy in ultra-low temperature environment, avoiding the problems of difficult operation, complex welding process and low production efficiency of traditional girth welds; it can connect not only the same materials but also different materials; at the same time, it can avoid the shortcomings of easy burning and penetration of traditional welding methods of thin tubes and thin plates 9, and solve the engineering problems such as easy cracking of complex structure girth welds of aluminum alloy thin-walled conical tubes and thin plates 9 and low joint strength.

[0050] The above is only a preferred implementation mode of the present invention. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified or part or all of the technical features can be replaced by equivalents, and these modifications and replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for ultra-low temperature plastic connection of an aluminum alloy thin-walled conical tube and a thin plate, which is realized by a plastic connection device, and the plastic connection device comprises: A cushion block (12), wherein a channel with an opening facing downward is formed inside the cushion block (12); A rotating push rod (13), the rotating push rod (13) enters from the bottom of the channel, a push plate (1) is connected to the rotating push rod (13), and the top of the push plate (1) is connected to two support rods (2) upward; A stainless steel heat preservation tank (4), wherein the stainless steel heat preservation tank (4) is installed on the top of the cushion block (12), and the stainless steel heat preservation tank (4) contains an ultra-low temperature cooling medium (5); An extrusion plate (3), the bottom of which is connected to the two support rods (2) and is capable of moving up and down in the stainless steel heat preservation tank (4); A backing plate (10), wherein the stainless steel heat preservation tank (4) is provided with a backing plate (10), wherein the middle of the backing plate (10) has an extrusion hole, the side wall of the backing plate (10) has a medium communication hole, and the top of the backing plate (10) is used to support the thin plate (9), the extrusion plate (3) contacts the bottom of the thin plate (9) through the extrusion hole, and the top of the thin plate (9) is pressed and positioned by a half-type pressure ring (6), and the middle of the half-type pressure ring (6) has a positioning cone hole that matches the thin-walled cone tube (8); The hole-expanding punch (7) enters from the top of the positioning cone hole, expands the thin-walled cone tube (8) in the ultra-low temperature cooling medium, and squeezes the tube material out of the center hole of the thin plate; The invention is characterized in that the connection method comprises the following steps: Step 1: Open a center hole at the center of the thin plate according to the design requirements, and at the same time open an arc-shaped groove concentric with the center hole at the center hole position on the lower surface of the thin plate for storing the blank; Step 2: Place the thin-walled conical tube and the thin plate with prefabricated center hole and arc-shaped groove on the pad respectively, and clamp the thin-walled conical tube with the half-type blank holder and press the thin plate with the center hole as a whole to form a closed cavity inside the thin-walled conical tube; Step 3: Place the assembly of the half-type blank holder, thin-walled cone tube and thin plate into a stainless steel insulation tank, and position and fix them on the press; Step 4: Lower the hole-expanding punch to the vicinity of the small opening of the thin-walled cone tube, pour ultra-low temperature medium into the stainless steel insulation tank to cool the hole-expanding punch, the thin-walled cone tube and the thin plate as a whole, so that the temperature of the deformation zone of the thin-walled cone tube and the thin plate is maintained below the ultra-low temperature; Step 5: The push rod pushes the extrusion plate with a large central diameter upward to contact the lower surface of the thin slab; Step 6: The hole-expanding punch moves down into the ultra-low temperature medium, expands the small opening area of ​​the cooled thin-walled tapered tube, and squeezes the tube material out of the center hole of the thin plate; Step 7: Rotate the push rod upward to drive the small-diameter extrusion plate to rotate and press the straight wall section of the thin-walled cone tube into the prefabricated annular groove on the lower surface of the thin plate in reverse, so as to achieve the plastic connection between the aluminum alloy thin-walled cone tube and the thin plate; Step 8: After the connection is completed, the hole-expanding punch moves upward, and drives the assembly of the half-type blank holder, the thin-walled cone tube, and the thin plate to be moved out of the stainless steel insulation tank filled with ultra-low temperature medium; Step 9: Open the half-type blank holder, remove the connector between the thin-walled tapered tube and the thin plate from the hole expansion punch, and return it to its original position.

Images