Bimetallic composite pipe and preparation method thereof

Abstract

The present invention relates to a bimetallic composite pipe and a preparation method thereof, belonging to the technical field of bimetallic composite materials. In order to solve the problem that the reaction temperature of the interface between the inner thin-walled metal pipe and the outer metal layer cannot be accurately observed and controlled in real time during the preparation of the bimetallic composite pipe, the present invention provides a preparation method for a bimetallic composite pipe, wherein an inner metal pipe with a heating component placed therethrough is placed in a casting mold, and the inner metal pipe is preheated by the heating component under a protective atmosphere; the outer metal material is melted and poured into the casting mold, and the bimetallic interface of the composite pipe obtained by pouring is insulated by the heating component, and the bimetallic composite pipe is obtained after cooling. The present invention uses a resistance wire heating component to preheat the inner metal pipe and keep it warm during the composite process, thereby promoting element diffusion at the bimetallic interface and regulating the thickness of the bimetallic interface layer, thereby obtaining a bimetallic composite pipe with good composite interface bonding.

Description

Technical Field

[0001] The present invention belongs to the technical field of bimetallic composite materials, and in particular relates to a bimetallic composite pipe and a preparation method thereof. Background Art

[0002] Bimetallic composites are materials formed by metallurgically combining two different metals, leveraging the strengths of each to produce properties superior to those of a single material. Liquid-solid composite casting is currently the most widely used process for preparing bimetallic composites. However, during this process, the bonding performance of the bimetallics is severely affected by factors such as the significant differences in physical and chemical properties between the metals and the short contact time between them during the casting process. This can lead to the formation of oxide films on both surfaces and the formation of hard and brittle intermetallic compounds at the interface.

[0003] During bimetallic composite casting, temperature is one of the decisive factors in determining whether the composite interface can achieve effective bonding. In liquid-solid composite casting, due to the low surface temperature of the solid inlay, contact with the high-temperature melt during the composite process will produce a chilling effect, affecting the bonding of the bimetallic. At the same time, the poor fluidity and wettability of the liquid alloy also increase the manufacturing difficulty of bimetallic castings. Preheating can prolong the thermal interaction time between the melt and the solid inlay, thereby promoting the formation of metallurgical bonding between the materials. Based on this, it is necessary to preheat the casting mold and solid inlay before composite.

[0004] While conventional preheating equipment, such as heating furnaces, can be used to preheat solid inlays, they require removal and placement in the mold during the bimetallic composite manufacturing process. This prevents accurate monitoring and real-time control of the reaction temperature at the bimetallic interface, and also prevents insulation of the composite interface after the molten metal is poured. This is particularly true when preparing bimetallic composite pipes, where thin-walled, curved solid inlays cool more rapidly during the composite process with the molten metal, making it difficult for the bimetallic composite to form an effective fusion zone. Summary of the Invention

[0005] In order to solve the problem that the reaction temperature at the interface between the inner thin-walled metal tube and the outer metal layer cannot be accurately observed and controlled in real time during the preparation of bimetallic composite tubes, the present invention provides a bimetallic composite tube and a preparation method thereof.

[0006] The technical solution of the present invention:

[0007] A method for preparing a bimetallic composite pipe comprises placing an inner metal pipe with a heating component passing through it in a casting mold, preheating the inner metal pipe using the heating component under a protective atmosphere, melting an outer metal material and pouring it into the casting mold, insulating the bimetallic interface of the composite pipe obtained by pouring using the heating component, and obtaining the bimetallic composite pipe after cooling.

[0008] Furthermore, the heating component is composed of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, and the power of the resistance wire is 800 to 2500W.

[0009] Furthermore, the preheating temperature of the inner metal pipe is measured by a thermocouple and the temperature signal is transmitted to a temperature controller, which controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal pipe.

[0010] Furthermore, the inner metal tube is made of stainless steel; and the outer metal is made of aluminum alloy.

[0011] Furthermore, the inner metal pipe also includes a pretreatment step, and the specific method of the pretreatment is to polish the surface of the inner metal pipe with sandpaper to remove impurities and oxide layer on the surface of the inner metal pipe; then the inner metal pipe is subjected to alkaline washing, acid washing and ultrasonic cleaning in sequence.

[0012] Furthermore, the preheating temperature of the inner metal tube is 600-800° C., and the protective atmosphere is argon atmosphere.

[0013] Furthermore, the pouring temperature of the outer layer metal material is 700-900° C., and the pouring speed is 0.2 kg / s.

[0014] Furthermore, the insulation temperature is not less than 600° C., and the insulation time is 60 to 600 seconds.

[0015] A bimetallic composite pipe is prepared by a method for preparing a bimetallic composite pipe. The wall thickness of the inner metal pipe of the bimetallic composite pipe is 0.5-2 mm, and the thickness of the outer metal layer is 20-50 mm.

[0016] Furthermore, the inner metal tube of the bimetallic composite tube is a stainless steel tube, and the outer metal is an aluminum alloy, wherein the aluminum alloy is specifically an aluminum-copper alloy or an aluminum-silicon alloy, and the chemical composition of the stainless steel tube includes, by weight percentage: C ≤ 0.030%; Si ≤ 1.00%; Mn ≤ 2.00%; S ≤ 0.030%; P ≤ 0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%, and the balance is Fe and unavoidable impurities;

[0017] The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%, with the remainder being Al and unavoidable impurities.

[0018] The chemical composition of the aluminum-silicon alloy includes, by mass percentage, Si: 4.5-6.0%; Fe≤0.8%; Cu≤0.30%; Mn≤0.05%; Mg≤0.05%; Zn≤0.10%, and the balance is Al and unavoidable impurities.

[0019] Beneficial effects of the present invention:

[0020] The preparation method of the bimetallic composite pipe provided by the present invention preheats the inner metal pipe and keeps it warm during the composite process through a resistance wire heating component, thereby solving the problem of fast cooling speed of the thin-walled curved surface of the inner metal pipe, promoting the element diffusion of the bimetallic interface and regulating the thickness of the bimetallic interface layer, thereby obtaining a bimetallic composite pipe with good composite interface bonding.

[0021] The present invention solves the problem that the reaction temperature of the interface between the inner thin-walled metal pipe and the outer metal during the composite process cannot be accurately observed and controlled in real time through a built-in heating component. The preheating temperature is measured by a thermocouple and the temperature signal is transmitted to a temperature controller to control the heating of the resistance wire, which can further achieve precise control of the preheating temperature of the inner metal pipe. When the temperature of the inner metal pipe cannot be measured, the preheating temperature of the stainless steel pipe can be inferred based on the power of the resistance wire and the preheating time.

[0022] The preparation method of the bimetallic composite pipe provided by the present invention is used to prepare an aluminum alloy / stainless steel bimetallic composite pipe. The obtained bimetallic composite pipe forms a continuous Fe-Al diffusion phase layer at the aluminum-steel interface, has a very dense interface between the aluminum alloy matrix and the stainless steel matrix, and has no defects such as cracks and pores at the interface. The composite is good and the interface connection rate reaches more than 75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the assembly of a casting mold, an inner metal tube, a ceramic insulating tube, and a resistance wire in the method for preparing a bimetallic composite tube according to the present invention, wherein: 1, casting mold; 2, inner metal tube; 3, ceramic insulating tube; 4, resistance wire;

[0024] Figure 2 This is an SEM image of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in Example 1;

[0025] Figure 3 This is an EDS image of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in Example 1;

[0026] Figure 4 This is an SEM image of the composite interface of the aluminum-silicon alloy / stainless steel bimetallic composite pipe prepared in Example 2;

[0027] Figure 5 This is an EDS image of the composite interface of the aluminum-silicon alloy / stainless steel bimetallic composite pipe prepared in Example 2;

[0028] Figure 6 This is an SEM image of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in Comparative Example 1;

[0029] Figure 7 This is the EDS image of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in Comparative Example 1. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention. The process equipment or devices not specifically noted in the following examples are all conventional equipment or devices in the art. Unless otherwise specified, the raw materials used in the examples of the present invention can be obtained commercially; unless otherwise specified, the technical means used in the examples of the present invention are all conventional means well known to those skilled in the art.

[0031] Example 1

[0032] This embodiment provides a method for preparing a bimetallic composite pipe, and uses the method for preparing an aluminum-copper alloy / stainless steel bimetallic composite pipe.

[0033] The inner metal tube used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite tube in this embodiment is a 316L stainless steel tube, and its chemical composition by weight percentage includes: C: ≤0.030%; Si ≤1.00%; Mn ≤2.00%; S ≤0.030%; P ≤0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%, and the balance is Fe and unavoidable impurities.

[0034] The outer metal used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is ZL205A aluminum-copper alloy. The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%; the balance is Al and unavoidable impurities.

[0035] The heating assembly in this embodiment consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, wherein the outer diameter of the resistance wire is 4.3 mm and the power of the resistance wire is 1200 W; the outer diameter of the ceramic insulating tube is 6 mm and the inner diameter is 5 mm; the size of the outer stainless steel tube in this embodiment is 8 mm in outer diameter, 7 mm in inner diameter and 130 mm in length.

[0036] The specific preparation method of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is as follows:

[0037] Step 1: Pre-treat the stainless steel pipe:

[0038] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0039] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0040] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0041] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0042] Step 2: Place the stainless steel tube in the mold and preheat it:

[0043] like Figure 1 As shown, an inner metal tube with a heating component placed through it is placed in a casting mold. Under the protection of an argon atmosphere, the resistance wire in the heating component is energized to preheat the stainless steel tube. The preheating temperature of the inner metal tube is measured by a thermocouple and the temperature signal is transmitted to a temperature controller. The temperature controller controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal tube to reach a preheating temperature of 650°C.

[0044] Step 3: After melting the outer layer of aluminum-copper alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-copper alloy is 720° C. and the pouring speed is 0.2 kg / s.

[0045] Step 4: After the pouring is completed, the resistance wire continues to be energized to keep the bimetallic interface of the obtained composite pipe warm. The insulation temperature is not less than 600°C and the insulation time is 120s. After cooling, an aluminum-copper alloy / stainless steel bimetallic composite pipe with an outer aluminum-copper alloy layer with a thickness of 30mm is obtained.

[0046] Aluminum-copper alloys have a wide crystallization temperature range, a wide liquid-solid phase region during solidification, well-developed dendrites, and a large hot brittle zone. This leads to poor fluidity and wettability, and a high tendency to hot cracking. Therefore, conventional liquid-solid composite casting methods are difficult to produce aluminum-copper alloy and stainless steel bimetallic castings. However, the preparation method provided by the present invention can successfully produce aluminum-copper alloy / stainless steel bimetallic composite pipes. Figure 2 and Figure 3 The SEM and EDS images of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite tubing prepared in this example demonstrate the formation of a continuous Fe-Al diffusion phase layer at the aluminum-steel interface. The resulting aluminum-copper alloy / stainless steel bimetallic tubing exhibits a very dense interface between the aluminum and steel substrates, free of cracks and defects, demonstrating excellent interfacial bonding.

[0047] The connection rate is calculated based on the length of the well-connected portion of the bimetallic interface and the total length of the bimetallic interface. Connection rate = length of the well-connected portion of the bimetallic interface / total length of the bimetallic interface * 100%. The bimetallic interface connection rate obtained in this embodiment is over 80%.

[0048] Example 2

[0049] This embodiment provides a method for preparing a bimetallic composite pipe, and uses the method for preparing an aluminum-silicon alloy / stainless steel bimetallic composite pipe.

[0050] The inner metal tube used in the preparation of the aluminum-silicon alloy / stainless steel bimetallic composite tube in this embodiment is a 316L stainless steel tube. The chemical composition of the stainless steel tube is as follows by weight: C: ≤0.030%; Si: ≤1.00%; Mn: ≤2.00%; S: ≤0.030%; P: ≤0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%; the balance is Fe and unavoidable impurities.

[0051] The outer metal used in the preparation of the aluminum-silicon alloy / stainless steel bimetallic composite pipe in this embodiment is 4043 aluminum-silicon alloy. The chemical composition of the aluminum-silicon alloy includes, by weight percentage, Si: 4.5-6.0%, Fe≤0.8%, Cu≤0.30%, Mn≤0.05%, Mg≤0.05%, Zn≤0.10%, and the balance is Al and unavoidable impurities.

[0052] The heating assembly in this embodiment consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, wherein the outer diameter of the resistance wire is 4.3 mm and the power of the resistance wire is 1200 W; the outer diameter of the ceramic insulating tube is 6 mm and the inner diameter is 5 mm; the size of the outer stainless steel tube in this embodiment is 8 mm in outer diameter, 7 mm in inner diameter and 130 mm in length.

[0053] The specific preparation method of the aluminum-silicon alloy / stainless steel bimetallic composite pipe in this embodiment is as follows:

[0054] Step 1: Pre-treat the stainless steel pipe:

[0055] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0056] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0057] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0058] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0059] Step 2: Place the stainless steel tube in the mold and preheat it:

[0060] like Figure 1 As shown, an inner metal tube with a heating component placed through it is placed in a casting mold. Under the protection of an argon atmosphere, the resistance wire in the heating component is energized to preheat the stainless steel tube. The preheating temperature of the inner metal tube is measured by a thermocouple and the temperature signal is transmitted to a temperature controller. The temperature controller controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal tube to reach a preheating temperature of 650°C.

[0061] Step 3: After melting the outer layer of aluminum-silicon alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-silicon alloy is 720° C. and the pouring speed is 0.2 kg / s.

[0062] Step 4: After the casting is completed, the resistance wire continues to be energized to keep the bimetallic interface of the obtained composite pipe warm. The insulation temperature is not less than 600°C and the insulation time is 120s. After cooling, an aluminum-silicon alloy / stainless steel bimetallic composite pipe with an outer aluminum-silicon alloy layer with a thickness of 30mm is obtained.

[0063] Figure 4 and Figure 5 SEM and EDS images of the composite interface of the aluminum-silicon alloy / stainless steel bimetallic composite tubing prepared in this example demonstrate the formation of a continuous Fe-Al diffusion phase layer at the aluminum-steel interface. The resulting aluminum-silicon alloy / stainless steel bimetallic tubing exhibits a very dense interface between the aluminum and steel substrates, free of any cracks or defects. The interface is well bonded, with a bimetallic interface connectivity exceeding 85%.

[0064] Example 3

[0065] This embodiment provides a method for preparing a bimetallic composite pipe, and uses the method for preparing an aluminum-copper alloy / stainless steel bimetallic composite pipe.

[0066] The inner metal tube used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite tube in this embodiment is a 304 stainless steel tube. The chemical composition of the stainless steel tube includes, by weight percentage: C ≤ 0.08%; Si ≤ 1.00%; Mn ≤ 2.00%; S ≤ 0.030%; P ≤ 0.045%; Cr: 18.00-20.00%; Ni: 8.00-11.00%; Mo: 2.00-3.00%; the balance is Fe and unavoidable impurities.

[0067] The outer metal used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is ZL205A aluminum-copper alloy. The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%; the balance is Al and unavoidable impurities.

[0068] The heating assembly in this embodiment consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, wherein the outer diameter of the resistance wire is 4.3 mm and the power of the resistance wire is 1200 W; the outer diameter of the ceramic insulating tube is 6 mm and the inner diameter is 5 mm; the size of the outer stainless steel tube in this embodiment is 8 mm in outer diameter, 7 mm in inner diameter and 130 mm in length.

[0069] The specific preparation method of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is as follows:

[0070] Step 1: Pre-treat the stainless steel pipe:

[0071] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0072] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0073] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0074] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0075] Step 2: Place the stainless steel tube in the mold and preheat it:

[0076] like Figure 1As shown, an inner metal tube with a heating component placed through it is placed in a casting mold. Under the protection of an argon atmosphere, the resistance wire in the heating component is energized to preheat the stainless steel tube. The preheating temperature of the inner metal tube is measured by a thermocouple and the temperature signal is transmitted to a temperature controller. The temperature controller controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal tube to reach a preheating temperature of 650°C.

[0077] Step 3: After melting the outer layer of aluminum-copper alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-copper alloy is 720° C. and the pouring speed is 0.2 kg / s.

[0078] Step 4: After the pouring is completed, the resistance wire continues to be energized to keep the bimetallic interface of the obtained composite pipe warm. The insulation temperature is not less than 600°C and the insulation time is 120s. After cooling, an aluminum-copper alloy / stainless steel bimetallic composite pipe with an outer aluminum-copper alloy layer with a thickness of 30mm is obtained.

[0079] The aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment forms a continuous Fe-Al diffusion phase layer at the aluminum-steel interface. The interface is well composited, and the bimetallic interface connection rate reaches more than 80%.

[0080] Example 4

[0081] This embodiment provides a method for preparing a bimetallic composite pipe, and uses the method for preparing an aluminum-copper alloy / stainless steel bimetallic composite pipe.

[0082] The inner metal tube used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite tube in this embodiment is a 316L stainless steel tube. The chemical composition of the stainless steel tube is as follows by weight percentage: C ≤ 0.030%; Si ≤ 1.00%; Mn ≤ 2.00%; S ≤ 0.030%; P ≤ 0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%; the balance is Fe and unavoidable impurities.

[0083] The outer metal used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is ZL205A aluminum-copper alloy. The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%; the balance is Al and unavoidable impurities.

[0084] The heating assembly in this embodiment consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, wherein the outer diameter of the resistance wire is 7.5 mm and the power of the resistance wire is 2000 W; the outer diameter of the ceramic insulating tube is 9 mm and the inner diameter is 8 mm; the size of the outer stainless steel tube in this embodiment is 12 mm in outer diameter, 10 mm in inner diameter and 130 mm in length.

[0085] The specific preparation method of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is as follows:

[0086] Step 1: Pre-treat the stainless steel pipe:

[0087] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0088] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0089] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0090] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0091] Step 2: Place the stainless steel tube in the mold and preheat it:

[0092] like Figure 1 As shown, an inner metal tube with a heating component placed through it is placed in a casting mold. Under the protection of an argon atmosphere, the resistance wire in the heating component is energized to preheat the stainless steel tube. The preheating temperature of the inner metal tube is measured by a thermocouple and the temperature signal is transmitted to a temperature controller. The temperature controller controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal tube to reach a preheating temperature of 650°C.

[0093] Step 3: After melting the outer layer of aluminum-copper alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-copper alloy is 720° C. and the pouring speed is 0.2 kg / s.

[0094] Step 4: After the casting is completed, the resistance wire continues to be energized to keep the bimetallic interface of the obtained composite pipe warm. The insulation temperature is not less than 600°C and the insulation time is 120s. After cooling, an aluminum-copper alloy / stainless steel bimetallic composite pipe with an outer aluminum-copper alloy layer with a thickness of 25mm is obtained.

[0095] The aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment forms a continuous Fe-Al diffusion phase layer at the aluminum-steel interface. The interface is well composited, and the bimetallic interface connection rate reaches more than 75%.

[0096] Example 5

[0097] This embodiment provides a method for preparing a bimetallic composite pipe, and uses the method for preparing an aluminum-copper alloy / stainless steel bimetallic composite pipe.

[0098] The inner metal tube used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite tube in this embodiment is a 316L stainless steel tube. The chemical composition of the stainless steel tube is as follows by weight percentage: C ≤ 0.030%; Si ≤ 1.00%; Mn ≤ 2.00%; S ≤ 0.030%; P ≤ 0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%; the balance is Fe and unavoidable impurities.

[0099] The outer metal used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is ZL205A aluminum-copper alloy. The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%; the balance is Al and unavoidable impurities.

[0100] The heating assembly in this embodiment consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, wherein the outer diameter of the resistance wire is 4.3 mm and the power of the resistance wire is 1200 W; the outer diameter of the ceramic insulating tube is 6 mm and the inner diameter is 5 mm; the size of the outer stainless steel tube in this embodiment is 8 mm in outer diameter, 7 mm in inner diameter and 130 mm in length.

[0101] The specific preparation method of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is as follows:

[0102] Step 1: Pre-treat the stainless steel pipe:

[0103] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0104] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0105] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0106] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0107] Step 2: Place the stainless steel tube in the mold and preheat it:

[0108] like Figure 1 As shown, an inner metal tube with a heating component placed through it is placed in a casting mold. Under the protection of an argon atmosphere, the resistance wire in the heating component is energized to preheat the stainless steel tube. The preheating temperature of the inner metal tube is measured by a thermocouple and the temperature signal is transmitted to a temperature controller. The temperature controller controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal tube to reach a preheating temperature of 600°C.

[0109] Step 3: After melting the outer layer of aluminum-copper alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-copper alloy is 700° C. and the pouring speed is 0.2 kg / s.

[0110] Step 4: After the casting is completed, the resistance wire continues to be energized to keep the bimetallic interface of the obtained composite pipe warm. The insulation temperature is not less than 600°C and the insulation time is 120s. After cooling, an aluminum-copper alloy / stainless steel bimetallic composite pipe with an outer aluminum-copper alloy layer with a thickness of 50mm is obtained.

[0111] The aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment forms a continuous Fe-Al diffusion phase layer at the aluminum-steel interface. The interface is well composited, and the bimetallic interface connection rate reaches more than 75%.

[0112] Example 6

[0113] This embodiment provides a method for preparing a bimetallic composite pipe, and uses the method for preparing an aluminum-copper alloy / stainless steel bimetallic composite pipe.

[0114] The inner metal tube used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite tube in this embodiment is a 316L stainless steel tube. The chemical composition of the stainless steel tube is as follows by weight percentage: C ≤ 0.030%; Si ≤ 1.00%; Mn ≤ 2.00%; S ≤ 0.030%; P ≤ 0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%; the balance is Fe and unavoidable impurities.

[0115] The outer metal used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is ZL205A aluminum-copper alloy. The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%; the balance is Al and unavoidable impurities.

[0116] The heating assembly in this embodiment consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire, wherein the outer diameter of the resistance wire is 4.3 mm and the power of the resistance wire is 1200 W; the outer diameter of the ceramic insulating tube is 6 mm and the inner diameter is 5 mm; the size of the outer stainless steel tube in this embodiment is 8 mm in outer diameter, 7 mm in inner diameter and 130 mm in length.

[0117] The specific preparation method of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this embodiment is as follows:

[0118] Step 1: Pre-treat the stainless steel pipe:

[0119] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0120] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0121] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0122] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0123] Step 2: Place the stainless steel tube in the mold and preheat it:

[0124] like Figure 1 As shown, an inner metal tube with a heating component placed through it is placed in a casting mold. Under the protection of an argon atmosphere, the resistance wire in the heating component is energized to preheat the stainless steel tube. The preheating temperature of the inner metal tube is measured by a thermocouple and the temperature signal is transmitted to a temperature controller. The temperature controller controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal tube to reach a preheating temperature of 700°C.

[0125] Step 3: After melting the outer layer of aluminum-copper alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-copper alloy is 750° C. and the pouring speed is 0.2 kg / s.

[0126] Step 4: After the casting is completed, the resistance wire continues to be energized to keep the bimetallic interface of the obtained composite pipe warm. The insulation temperature is not less than 600°C and the insulation time is 60s. After cooling, an aluminum-copper alloy / stainless steel bimetallic composite pipe with an outer aluminum-copper alloy layer with a thickness of 30mm is obtained.

[0127] The aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment forms a continuous Fe-Al diffusion phase layer at the aluminum-steel interface. The interface is well composited, and the bimetallic interface connection rate reaches more than 75%.

[0128] Comparative Example 1

[0129] This comparative example provides a method for preparing an aluminum-copper alloy / stainless steel bimetallic composite pipe by preheating a stainless steel pipe in a common heating furnace.

[0130] The inner metal tube used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite tube in this comparative example is a 316L stainless steel tube. The chemical composition of the stainless steel tube includes, by weight percentage: C ≤ 0.030%; Si ≤ 1.00%; Mn ≤ 2.00%; S ≤ 0.030%; P ≤ 0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%; the balance is Fe and unavoidable impurities.

[0131] The outer metal used in the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this comparative example is ZL205A aluminum-copper alloy, and the chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%; the balance is Al and unavoidable impurities.

[0132] The dimensions of the outer stainless steel tube in this comparative example are 8 mm in outer diameter, 7 mm in inner diameter and 130 mm in length.

[0133] The specific preparation method of the aluminum-copper alloy / stainless steel bimetallic composite pipe of this comparative example is as follows:

[0134] Step 1: Pre-treat the stainless steel pipe:

[0135] (1) Use sandpaper to polish the surface of the stainless steel tube to remove obvious impurities and oxide layer on the surface of the stainless steel tube;

[0136] (2) Soak the stainless steel tube in a 10% NaOH solution for 10 minutes for alkaline cleaning;

[0137] (3) Soak the stainless steel tube in 10% hydrochloric acid solution for 10 minutes for pickling;

[0138] (4) Place the stainless steel tube in alcohol for ultrasonic cleaning.

[0139] Step 2: Place the stainless steel tube in a common heating furnace and preheat it under a nitrogen atmosphere to a preheating temperature of 650°C. Take the stainless steel tube that has reached the preheating temperature out of the heating furnace and place it in a casting mold.

[0140] Step 3: After melting the outer layer of aluminum-copper alloy, pour it into the mold until it is full. The pouring temperature of the aluminum-copper alloy is 720° C. and the pouring speed is 0.2 kg / s.

[0141] Step 4: After the pouring is completed, the pipe is cooled to obtain an aluminum-copper alloy / stainless steel bimetallic composite pipe with an outer aluminum-copper alloy layer having a thickness of 30 mm.

[0142] Figure 6 and Figure 7 SEM and EDS images of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this comparative example show no distinct Fe-Al diffusion layer between the aluminum and steel, resulting in only a basic mechanical bond. Defects such as pores are present at the aluminum-steel interface, resulting in a poor mechanical bond and a 0% bimetallic interface connection rate.

Claims

1. A method for preparing a bimetallic composite pipe, characterized in that: An inner metal tube with a heating component placed through it is placed in a casting mold, and the inner metal tube is preheated by the heating component under a protective atmosphere, and the preheating temperature of the inner metal tube is 600-800°C; the outer metal material is melted and poured into the casting mold at a pouring speed of 0.2kg / s, and the pouring temperature of the outer metal material is 700-900°C, and the inner metal tube is stainless steel; the outer metal is an aluminum alloy, and the bimetallic interface of the composite tube obtained by casting is insulated by the heating component, and the insulation temperature is not less than 600°C, and the insulation time is 60-600s. After cooling, a bimetallic composite tube is obtained, and the wall thickness of the inner metal tube of the bimetallic composite tube is 0.5-2mm, and the thickness of the outer metal layer is 20-50mm; The aluminum alloy is specifically an aluminum-copper alloy or an aluminum-silicon alloy, and the chemical composition of the stainless steel pipe includes, by weight percentage: C≤0.030%; Si≤1.00%; Mn≤2.00%; S≤0.030%; P≤0.045%; Cr: 16.00-18.00%; Ni: 10.00-14.00%; Mo: 2.00-3.00%, and the balance is Fe and unavoidable impurities; The chemical composition of the aluminum-copper alloy includes, by mass percentage, Cu: 4.0-5.0%; Si≤0.06%; Mg≤0.05%; Mn: 0.3-0.6%; Fe≤0.15%; Ti: 0.15-0.35%; V: 0.05-0.3%; Zr: 0.15-0.25%; B: 0.005-0.6%, with the remainder being Al and unavoidable impurities. The chemical composition of the aluminum-silicon alloy includes, by mass percentage, Si: 4.5-6.0%; Fe≤0.8%; Cu≤0.30%; Mn≤0.05%; Mg≤0.05%; Zn≤0.10%, and the balance is Al and unavoidable impurities.

2. The method for preparing a bimetallic composite pipe according to claim 1, characterized in that: The heating component consists of a resistance wire and a ceramic insulating tube sleeved on the outer layer of the resistance wire. The power of the resistance wire is 800-2500W.

3. The method for preparing a bimetallic composite pipe according to claim 2, characterized in that: The preheating temperature of the inner metal pipe is measured by a thermocouple and the temperature signal is transmitted to the temperature controller, which controls the heating of the resistance wire to achieve precise control of the preheating temperature of the inner metal pipe.

4. The method for preparing a bimetallic composite pipe according to claim 3, characterized in that: The inner metal pipe also includes a pretreatment step, and the specific method of the pretreatment is to polish the surface of the inner metal pipe with sandpaper to remove impurities and oxide layer on the surface of the inner metal pipe; then the inner metal pipe is sequentially subjected to alkali washing, acid washing and ultrasonic cleaning.

5. The method for preparing a bimetallic composite pipe according to claim 4, characterized in that: The protective atmosphere is argon atmosphere.

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