CN106903212A - A kind of double-layer composite pipe and preparation method thereof - Google Patents

Abstract

The invention provides a double-layer composite pipe and a forming method thereof, which are used to solve the problems in the prior art that the double-layer metal pipes have different expansion and contraction ratios, complicated processing technology, and cannot form components with complex structures. The invention provides a method for forming a double-layer composite pipe, comprising the following steps: assembling, placing a hollow aluminum alloy pipe blank inside a hollow carbon steel pipe blank to form a double-layer composite pipe blank; forming, placing the double-layer composite pipe blank Placed in the extrusion space, the extrusion space can be matched with the double-layer composite tube blank, and has a cavity forming a target shape; filling the hollow aluminum alloy tube blank of the double-layer composite tube blank medium particles; applying pressure to the medium particles from the axial direction of both ends of the double-layer composite tube blank; the double-layer composite tube blank is deformed to fill the cavity to form a double-layer composite tube. The double-layer composite pipe of the invention is simple to prepare, has good performance, and can be used to make pipe fittings with complex structures.

Description

A kind of double-layer composite pipe and its preparation method

technical field

The invention relates to the technical field of pipe fitting processing, in particular to a double-layer composite pipe and a preparation method thereof.

Background technique

As a common fluid conveying device for gases, liquids, powders, etc., pipelines are widely used in various fields such as aerospace, transportation, automobiles, city gas, water supply and heating systems, as well as metallurgy, petroleum, chemical industry, and electric power. With the continuous development of the national economy and the improvement of people's living standards, as well as the expansion of industrial construction and residential construction, the performance requirements for pipelines are also increasing. On the basis of ensuring rigidity, they must also have good corrosion resistance and High temperature performance, etc.

The bimetallic composite pipe is composed of two different metal pipes. The inner and outer pipes are tightly combined through various deformation and connection techniques. When an external force is applied, the inner and outer pipes deform at the same time and the interface does not separate. The general design principle of bimetal composite pipe is that the base material meets the design stress of the parts, and the inner pipe meets the performance requirements such as corrosion resistance or wear resistance. Compared with the single metal pipe, the bimetallic composite pipe combines the physical, chemical and mechanical properties of the component metal materials, can make full use of the characteristics of the outer pipe and the inner pipe, not only has the required high strength, but also has excellent anti-corrosion properties. Corrosion, wear resistance and other properties, and save the use of rare and precious metals, reducing production costs. Therefore, bimetallic composite pipes can be widely used in transportation pipes, heat exchanger pipes, and equipment pipes in the fields of petroleum, chemical industry, nuclear industry, medical treatment, food, construction, and fire protection.

In the bimetal composite pipe, the inner pipe mainly realizes the anti-corrosion function, and the outer pipe improves the rigidity and strength, which reduces the cost and improves the rigidity and strength compared with the simple aluminum alloy pipe member; compared with the simple steel pipe, the anti-corrosion performance is improved, and the specific stiffness is increased to achieve light weight .

If the inner tube is made of high-strength aluminum alloy extruded pipe, the formability of the high-strength aluminum alloy extruded pipe is poor, and the elongation of the aluminum alloy extruded pipe of the 5 series, 6 series and 7 series does not exceed 10% at most, and some are even lower than 5%, even if annealing or solution treatment is used, the increase in elongation generally does not exceed 20%. Therefore, it is almost impossible to use high-strength aluminum alloy extruded pipes to form complex-shaped tubular members. At the same time, high-strength aluminum alloy tubular components generally have the characteristics of anti-corrosion or weight reduction, and also have high requirements for mechanical properties such as strength, stiffness, surface hardness and fatigue resistance.

The existing double-layer metal pipe processing adopts the hydraulic expansion method. In the hydraulic bulging process, the pipe end seal is generally sealed by mechanical compression, that is, the two ends of the double-layer metal pipe are compressed and deformed to achieve sealing. This sealing method makes the inner and outer layers When the metal tube blank is bulging, the material at both ends cannot flow to the forming area to form a feeding effect. Therefore, the forming area of the pipe fittings hydroformed in this way is severely thinned and even ruptured.

Therefore, there is an urgent need for a manufacturing process for processing double-layer metal pipes, making full use of the advantages of the inner pipe and the outer pipe, and simplifying the processing technology.

Contents of the invention

The technical solution adopted to solve the above problems is a double-layer composite pipe and a preparation method thereof.

A method for forming a double-layer composite pipe provided by the present invention is characterized in that it comprises the following steps:

Assembly: the hollow aluminum alloy tube blank is set inside the hollow carbon steel tube blank to form a double-layer composite tube blank;

Forming: placing the double-layer composite tube blank in the extrusion space, the extrusion space can match the double-layer composite tube blank, and has a cavity forming a target shape;

filling medium particles in the hollow aluminum alloy tube blank of the double-layer composite tube blank;

applying pressure to the media particles from the axial direction of both ends of the double-layer composite tube blank;

The double-layer composite pipe is deformed to fill the cavity to form a double-layer composite pipe.

Preferably, the hollow carbon steel billet is obtained by coil welding.

Preferably, the cavity is a convex ring, tetrahedron or hexahedron.

Preferably, the material of the hollow carbon steel billet is selected from Q235 or 304 stainless steel plate.

Preferably, the material of the hollow aluminum alloy tube blank is selected from AA6061 or AA5052.

Preferably, the extrusion space is composed of a closed space surrounded by a pipe fitting mold and a medium pressure head;

Among them, there are at least two pipe fitting molds, which are driven by the driving mechanism for relative movement;

The medium pressure head includes a first pressure head and a second pressure head for applying pressure to the medium particles.

Preferably, the step of heat-treating the hollow aluminum alloy tube is also included before the assembling step;

The heat treatment method includes: annealing treatment or solution treatment.

Preferably, after the forming step, a step of aging treatment for the double-layer composite pipe is also included.

The purpose of the present invention is also to provide a double-layer composite pipe, which is prepared by the above-mentioned forming method of the double-layer composite pipe.

The present invention has the following advantages:

1) Due to the extensibility of high-strength aluminum alloy materials such as 5 series, 6 series and 7 series (the so-called 5 series, 6 series, and 7 series refer to the aluminum alloy extruded pipes marked with AA and starting with 5, 6, and 7 respectively) Poor, especially extruded pipes; at the same time, the welding performance is also poor, and it is difficult to prepare sheet coil welded pipes. These are the main reasons that limit the wide application of high-strength aluminum alloy pipes in actual production. If it is coated with thin-walled carbon steel pipe to obtain a composite pipe blank, the high-strength aluminum alloy pipe blank lined with the dual action of the internal pressure of the medium particles and the outer coating of the carbon steel pipe can effectively improve its formability. The mechanism of the improved formability lies in that the substantial increase in the thickness pressure increases the forming limit; at the same time, the friction between the two tubes is enhanced, thereby inhibiting the deformation and thinning of the lining tube billet, which is different from the stress-strain state of the general bulging deformation process .

(2) The preparation of the double-layer composite tube blank is simple. The inner liner can be extruded high-strength aluminum alloy pipe, and the hollow carbon steel billet can be rolled and welded according to the outer diameter of the extruded pipe. Because the medium particle bulging process has lower requirements on the roundness and dimensional tolerance of the double-layer composite tube blank, especially the low requirements on the matching size of the inner lining and the hollow carbon steel tube blank, this makes the tube blank preparation of this process very convenient and cheap;

(3) High-strength aluminum alloy tubular members generally have application characteristics such as anti-corrosion, weight reduction and energy absorption, and have high requirements for mechanical properties such as strength, stiffness, surface hardness and fatigue resistance. The combination of aluminum alloy extruded tubes, and by adjusting the material and thickness of bimetallic materials, can adapt to the use needs to a greater extent, achieve optimal material utilization efficiency, and further expand the application field of tubular components.

(4) This type of composite pipe fittings is prepared by the medium particle bulging process. The forming process has lower requirements on the mold and loading equipment, and the process steps can be realized on a general-purpose press without adding external devices. The process is easy to implement and does not need to add more invest.

Description of drawings

Fig. 1 is a flowchart of the assembly of the double-layer composite pipe in Embodiment 1 of the present invention.

Fig. 2 is a mold opening sectional view of the double-layer composite pipe forming mold in Embodiment 1 of the present invention.

Fig. 3 is a mold closing sectional view of the double-layer composite pipe forming mold in Embodiment 1 of the present invention.

Fig. 4 is a cross-sectional view of extrusion forming of a double-layer composite pipe forming die in Embodiment 1 of the present invention.

Fig. 5 is a photo of the double-layer composite pipe prepared in Example 2 of the present invention.

Fig. 6 is a photo of the double-layer composite pipe prepared in Example 3 of the present invention.

Reference signs: 1. Hollow carbon steel pipe billet; 2. Hollow aluminum alloy pipe billet; 3. Double-layer composite pipe billet; 4. Welding joint; 5. Medium particle; 6. Medium pressure head; 61. First pressure head; 62. The second pressure head; 7. Pipe fitting mold; 71. The first pipe fitting mold; 72. The second pipe fitting mold; 8. Die frame; 9. Clamping cylinder; 10. Extrusion space; 11. Guide rod; 12. Guide rod nut; 13. Cavity; 14. Double-layer composite pipe.

detailed description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figures 1-4, this embodiment provides a method for forming a double-layer composite pipe, including the following steps:

Assembly: the hollow aluminum alloy tube blank 2 is placed inside the hollow carbon steel tube blank 1 to form a double-layer composite tube blank 3;

Specifically, as shown in Figure 1, the welding joint 4 of the hollow carbon steel pipe billet 1 needs to be cleaned and leveled, and the inner diameter is designed according to the basic size of the outer diameter of the hollow aluminum alloy pipe billet 2, and the base shaft clearance is matched with B11 grade, and the same precision grade is adopted. Controlling the cylindricity of the welded hollow carbon steel pipe billet 1. Then, two hollow carbon steel tube blanks 1 and hollow aluminum alloy tube blanks 2 of different materials are assembled to obtain a double-layer composite tube blank 3 .

Preferably, the hollow carbon steel pipe blank 1 is obtained by coil welding.

Forming: placing the double-layer composite tube blank 3 in the extrusion space 10, the extrusion space 10 can match the double-layer composite tube blank 3, and has a cavity 13 for forming a target shape;

Filling medium particles 5 in the hollow aluminum alloy tube blank 2 of the double-layer composite tube blank 3;

Apply pressure to the medium particles 5 from the axial direction of both ends of the double-layer composite tube blank 3;

The double-layer composite pipe blank 3 is deformed to fill the cavity 13 to form a double-layer composite pipe 14 .

Specifically, as shown in Figure 2, the mold device is in an open state, and the medium pressure head 6 includes a first pressure head 61 and a second pressure head 62, wherein the first pressure head 61 is at the upper limit position, and the second medium pressure head 62 At the lower limit position, all are directly driven by hydraulic equipment;

The pipe fitting mold 7 includes a first pipe fitting mold 71 and a second pipe fitting mold 72, which are in the mold-opening state, respectively driven directly by the clamping cylinders 9 on both sides, and installed on the guide rod 11 to realize sliding guidance, and the guide rod 11 passes through the guide rod Nut 12 is fixed on the formwork 8. The above-mentioned first medium pressure head 61 , second medium pressure head 62 , first pipe fitting mold 71 and second pipe fitting mold 72 can ensure the smooth loading of the double-layer composite pipe blank 3 in the mold opening state.

As shown in Figure 3, the double-layer composite tube blank 3, the second medium pressure head 62, the first pipe fitting mold 71, and the second pipe fitting mold 72 are respectively moved to the mold closing position, and then the medium particles 5 are loaded; the first The medium pressure head 61 also moves to the mold closing position.

The above-mentioned first medium pressure head 61, second medium pressure head 62, first pipe fitting mold 71 and second pipe fitting mold 72 form an extrusion space 10 after mold closing, and the extrusion space 10 can be combined with a double layer The blank tube 3 is fitted and has a cavity 13 formed into a target shape.

The cavity 13 is a convex ring, a tetrahedron or a hexahedron. It can be understood that the shape of the cavity 13 can be designed according to specific requirements.

As shown in Figure 4, the first pipe fitting mold 71 and the second pipe fitting mold 72 respectively ensure the mold clamping state under the pressure of the mold clamping cylinder 90. Loading is carried out under the drive of the equipment, and the medium particles 5 are loaded to force the double-layer composite pipe blank 3 to be deformed and molded to obtain a double-layer composite pipe 14 . After forming, the first medium pressure head 61 and the second medium pressure head 62 first move to the initial position, then the first pipe mold 71 and the second pipe mold 72 move to the initial position, and the double-layer composite pipe 14 is taken out to complete the forming process.

The above method utilizes the cladding pressure effect of the hollow carbon steel tube blank and the hollow aluminum alloy tube blank during coupling deformation, and the friction retention effect between the two tube blanks, which greatly improves the forming performance of the aluminum alloy tube material, and can be formed by conventional methods. Complex tubular members that are less than .

Moreover, by adjusting the material and thickness of the hollow carbon steel pipe billet and the hollow aluminum alloy pipe billet, the advantages of high specific strength and strong corrosion resistance of the aluminum alloy are fully utilized, and the advantages of high hardness, high strength and excellent welding performance of the steel are utilized, which can be adapted to The stiffness and strength requirements of different service conditions can achieve the goal of lightweight components.

At the same time, due to the poor welding performance of the hollow aluminum alloy tube billet, extruded pipe can be used; while the weldability of the steel plate is better, the hollow carbon steel pipe billet can be welded according to the outer diameter of the aluminum alloy extruded pipe, and the hollow carbon steel pipe billet and There must be a certain gap between the two tube blanks in the assembly of the hollow aluminum alloy tube blank, but through the high pressure bulge in the medium particle, the two tube blanks are jointly deformed and tightly fitted, which ensures the integrity of the composite pipe fitting.

Compared with other internal high-pressure forming processes, the medium particle bulging process does not need to be compressed and sealed at both ends of the composite tube blank to form a bulging internal high pressure. Therefore, the two ends of the double-layer composite tube blank can shrink freely during the medium particle bulging process. This is the key to improving the uniformity of the wall thickness of the formed pipe fittings. At the same time, due to the difference in material properties of the two materials of the double-layer composite tube blank, there must be a difference in the shrinkage of the inner and outer tube blanks during forming, and the free tube end boundary conditions are more conducive to the forming of composite tube fittings.

The use of double-layer composite tube blanks for high-pressure bulging of medium particles has the following advantages:

①During the process of internal bulging of the medium particles, the medium particles are always coated on the inner surface of the hollow aluminum alloy tube blank, forcing the inner and outer bimetallic tube blanks to be jointly deformed, and the deformation of the hollow carbon steel tube blank reacts on the surface method of the hollow aluminum alloy tube blank The pressure can significantly improve the forming performance of the inner hollow aluminum alloy tube; at the same time, the increase of the positive pressure on the tube wall enhances the friction between the two tube walls, and the friction can inhibit the forming of the hollow aluminum alloy tube. Thinning, the so-called enhanced friction retention effect, is also one of the important factors for increasing the forming limit;

②Select the material of the inner and outer metals according to the product requirements, and design the thickness ratio of the inner and outer metal layers to adjust the stiffness and strength requirements of the product to achieve optimal material utilization efficiency. Since the medium particle bulging process uses solid particles to transmit pressure, the high internal pressure environment of the tube blank required by the process does not require a special sealing device, so the requirements for the roundness and dimensional tolerance of the pipe fittings are very low. This process advantage makes the double-layer composite pipe The billet preparation can use the hollow carbon steel pipe billet and the hollow aluminum alloy pipe billet for large gap assembly, which reduces the conditions for the preparation of the double-layer composite pipe, thereby reducing the manufacturing cost.

The following is an analysis of the stress on the two tube blanks during the specific forming process:

Assumption: the inner and outer radii of the hollow aluminum alloy tube blank are a and b respectively; the inner and outer radii of the outer tube are c and d respectively; the thickness of the tube wall is t. Before compounding, c>b, that is, there is a gap between the hollow aluminum alloy tube blank and the hollow carbon steel tube blank. According to the theory of elastic-plastic mechanics, during the bulging compounding process, the hollow aluminum alloy tube billet gradually expands and gradually combines with the hollow carbon steel tube billet. Under the condition of plane stress, with the ideal elastoplasticity as the material model, when the hollow aluminum alloy tube blank undergoes plastic deformation and just contacts with the hollow carbon steel tube blank, but the contact pressure has not yet been generated, the internal pressure of the hollow aluminum alloy tube blank, hollow After the aluminum alloy tube billet expands further, it will generate contact pressure with the hollow carbon steel tube billet. When the contact pressure reaches a certain limit value, the surface of the hollow carbon steel billet just yields, and at the same time, the internal pressure on the hollow aluminum alloy billet also reaches its limit value. During the loading process, after the hollow aluminum alloy tube billet is in contact with the hollow carbon steel tube billet and generates contact pressure, the hollow carbon steel tube billet is only subjected to uniform internal pressure (contact pressure). The force condition and radial displacement and the displacement of the inner wall of the hollow carbon steel billet. In the unloading stage, the hollow aluminum alloy tube is no longer under the action of pressure, and the plastic unloading shrinkage will naturally occur, that is, the outer circumference of the hollow aluminum alloy tube will produce radial displacement. The difference between the displacement at the inner wall of the hollow carbon steel billet and the natural shrinkage of the hollow aluminum alloy billet when it is unloaded is the interference between the hollow aluminum alloy billet and the hollow carbon steel billet during the "common" unloading process. When the displacement at the wall is not less than the natural shrinkage of the hollow aluminum alloy tube billet, there will be residual pressure at the contact surface during unloading.

Example 2

This embodiment adopts the method as described in Example 1. The hollow carbon steel pipe billet 1 adopts Q235 plate welded steel pipe, and the hollow aluminum alloy pipe billet 2 adopts AA5052 extruded pipe material. Through the above steps, the convex ring pipe fittings are formed, as shown in the figure. 5.

In addition, before the AA5052 pipe is formed, it can also be subjected to heat treatment, specifically annealing treatment, in order to increase the elongation. The strengthening of AA5052 can be strengthened by strain, that is, the greater the degree of bulging, the better the strengthening effect . The main functions of AA5052 in this embodiment are anti-corrosion, energy absorption and weight reduction, while the stiffness and strength of the components are mainly realized by Q235 plate welded steel pipes.

Example 3

This embodiment adopts the method as described in Example 1. The hollow carbon steel pipe billet 1 adopts 304 stainless steel coil welded pipe, and the hollow aluminum alloy pipe billet 2 adopts AA6061 extruded pipe material. Through the above steps, a hexahedral pipe fitting is formed, as shown in the figure. 6.

In addition, before the AA6061 pipe is formed, heat treatment can be carried out to strengthen the material. It should be understood that solution treatment is selected for the heat treatment of the 6-series and 7-series aluminum alloy extruded pipes.

Immediately after solution treatment, it is assembled with 304 stainless steel coil welded pipe and expanded into the target shape, and then artificially aged to restore the strength of the aluminum alloy pipe. The artificial aging conditions of AA6061 pipe fittings will not affect the material properties of 304 stainless steel, which is also an important reason why they can be used in combination, because they must enter the artificial aging process together after forming. In this way, the rigidity and strength of the pipe member are shared by the two, while the inner aluminum alloy material still plays an important role in corrosion resistance, energy absorption and weight reduction.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (9)

1. a kind of manufacturing process of double-layer composite pipe, it is characterised in that comprise the following steps：

Assembling：Hollow aluminum-alloy tubes are arranged inside hollow carbon steel pipe base, two-layer compound pipe is formed；

Shaping：The two-layer compound pipe is placed in extruding space, described extruding space can be with the two-layer compound pipe Match, and with forming the die cavity of target shape；

The filled media particle in the hollow aluminum-alloy tubes of the two-layer compound pipe；

Pressure is applied to the media particle from the axial direction at the two-layer compound pipe two ends；

The two-layer compound pipe deforms upon the die cavity described in filling, forms double-layer composite pipe.

2. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that described hollow carbon steel pipe base is logical Cross and be welded what is obtained.

3. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that described die cavity is bulge loop, four sides Body or hexahedron.

4. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that the material of described hollow carbon steel pipe base Material is selected from Q235 or 304 stainless steel plates.

5. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that described hollow aluminum-alloy tubes Material is selected from AA6061 or AA5052.

6. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that described extruding space is by pipe fitting The closing space composition that mould and medium pressure head are surrounded；

Wherein, pipe fitting mold at least two, and be driven by drive mechanism and perform relative motion；

The medium pressure head includes the first pressure head and the second pressure head, for applying pressure to the media particle.

7. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that it is right also to include before installation step The step of hollow aluminium-alloy pipe is heat-treated；

Described heat treatment method includes：Annealing or solution treatment.

8. the manufacturing process of double-layer composite pipe as claimed in claim 1, it is characterised in that it is right also to include after forming step The step of double-layer composite pipe carries out Ageing Treatment.

9. a kind of double-layer composite pipe, it is characterised in that the double-layer composite pipe be using as described in claim 1-8 is any pair Prepared by the manufacturing process of layer multiple tube.