Bimetal composite pipe and preparation method thereof

Abstract

The invention relates to a bimetal composite pipe and a preparation method thereof, and belongs to the technical field of bimetal composite materials. In order to solve the problem that the interface reaction temperature of an inner-layer thin-wall metal pipe and an outer-layer metal pipe cannot be accurately observed and regulated in real time in the preparation process of the bimetal composite pipe, the invention provides a preparation method of the bimetal composite pipe, which comprises the following steps of: putting an inner-layer metal pipe in which a heating assembly is arranged in a penetrating manner into a casting mold; the inner-layer metal pipe is preheated through a heating assembly under the protective atmosphere; and an outer-layer metal material is smelted and then poured into a casting mold, the heating assembly is used for conducting heat preservation on the bimetallic interface of the composite pipe obtained through pouring, and the bimetallic composite pipe is obtained after cooling. The inner layer metal pipe is preheated through the resistance wire heating assembly, heat preservation is conducted in the compounding process, element diffusion of the bimetallic interface is promoted, the thickness of the bimetallic interface layer is regulated and controlled, and the bimetallic composite pipe with the good composite interface combination is obtained.

Description

Technical Field

[0001] The 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 made of two different metals through metallurgical methods. They can fully utilize the advantages of each material to produce performance that is better than that of a single material. Liquid-solid composite casting is currently the most widely used process in the preparation of bimetallic composites. However, in the liquid-solid composite casting process, due to the large differences in the physical and chemical properties between the metals and the short contact time between the metals during the casting process, oxide films are easily formed on the surfaces of both metals, and hard and brittle intermetallic compound phases are easily formed on the interface, which seriously affects the bonding performance of the bimetal.

[0003] In the process of bimetallic composite casting, temperature is one of the decisive factors for whether the composite interface can achieve effective bonding. In liquid-solid composite casting, due to the low surface temperature of the solid inlay, it will produce a chilling effect when it comes into contact with the high-temperature melt during the composite process, affecting the bonding of the bimetal. At the same time, the poor fluidity and wettability of the liquid alloy will also increase the difficulty of manufacturing bimetallic castings. Preheating treatment can prolong the thermal action 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 mold and solid inlay before composite.

[0004] Although common preheating equipment such as heating furnaces can be used to preheat solid inlays, the solid inlays need to be taken out and placed in the mold in advance during the preparation of bimetallic composite materials. It is impossible to accurately observe the reaction temperature of the bimetallic interface and adjust it in real time, and it is also impossible to keep the composite interface warm after the molten metal is poured. Especially when preparing bimetallic composite pipes, the thin-walled curved solid inlay cools faster during the composite process with the molten metal, and it is difficult for the bimetal to form an effective fusion zone. Summary of the invention

[0005] In order to solve the problem that the interface reaction temperature 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 the bimetallic composite tube, 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 placed therethrough in a casting mold, preheating the inner metal pipe by using the heating component under a protective atmosphere; smelting an outer metal material and pouring it into the casting mold, using the heating component to insulate the bimetallic interface of the composite pipe obtained by pouring, 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 800-2500W.

[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 pipe 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 grind the surface of the inner metal pipe with sandpaper to remove impurities and oxide layer on the surface of the inner metal pipe; then perform alkaline washing, acid washing and ultrasonic cleaning on the inner metal pipe in turn.

[0012] Furthermore, the preheating temperature of the inner metal tube is 600-800° C., and the protective atmosphere is an 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 prepared by a method for preparing a bimetallic composite pipe, wherein the pipe wall thickness of an inner metal pipe of the bimetallic composite pipe is 0.5-2 mm, and the thickness of an 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%, 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 remainder 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 accurate 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 resistance wire power and 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 is more than 75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention 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 preparation method of the bimetallic composite tube, wherein: 1, casting mold; 2, inner metal tube; 3, ceramic insulating tube; 4, resistance wire;

[0024] Figure 2 This is a 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 a 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 a 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 in conjunction with the embodiments, but it 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 protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments 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 the 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, 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 remainder 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 4.3mm and the power of the resistance wire is 1200W; the outer diameter of the ceramic insulating tube is 6mm and the inner diameter is 5mm; the size of the outer stainless steel tube in this embodiment is 8mm in outer diameter, 7mm in inner diameter and 130mm 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0040] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked 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 the stainless steel tube:

[0043] like Figure 1 As shown, an inner metal pipe with a heating component placed inside 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 pipe. The preheating temperature of the inner metal pipe 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 pipe 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 insulate the bimetallic interface of the obtained composite pipe. 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 thickness of 30mm is obtained.

[0046] Aluminum-copper alloy has a wide crystallization temperature range, a wide liquid-solid two-phase region during solidification, well-developed dendrites and a large hot brittle region. Its fluidity and wettability are poor, and the alloy has a large tendency to hot cracking. Therefore, it is difficult to prepare aluminum-copper alloy and stainless steel bimetallic castings using conventional liquid-solid composite casting methods. The preparation method provided by the present invention can successfully prepare aluminum-copper alloy / stainless steel bimetallic composite pipes. Figure 2 and Figure 3 The composite interface SEM and EDS images of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment show that a continuous Fe-Al diffusion phase layer is formed at the aluminum-steel interface. The obtained aluminum-copper alloy / stainless steel bimetallic has a very dense interface between the aluminum matrix and the steel matrix, and there are no crack defects at the interface, and the interface is well composited.

[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 more than 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 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 remainder 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 4.3mm and the power of the resistance wire is 1200W; the outer diameter of the ceramic insulating tube is 6mm and the inner diameter is 5mm; the size of the outer stainless steel tube in this embodiment is 8mm in outer diameter, 7mm in inner diameter and 130mm 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0057] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked 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 the stainless steel tube:

[0060] like Figure 1 As shown, an inner metal pipe with a heating component placed inside 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 pipe. The preheating temperature of the inner metal pipe 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 pipe 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 0.2kg / s.

[0062] Step 4: After the pouring is completed, the resistance wire continues to be energized to insulate the bimetallic interface of the obtained composite pipe. 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 thickness of 30mm is obtained.

[0063] Figure 4 and Figure 5 The composite interface SEM and EDS images of the aluminum-silicon alloy / stainless steel bimetallic composite pipe prepared in this embodiment show that a continuous Fe-Al diffusion phase layer is formed at the aluminum-steel interface. The obtained aluminum-silicon alloy / stainless steel bimetallic has a very dense interface between the aluminum matrix and the steel matrix, and there are no crack defects at the interface. The interface is well composited, and the bimetallic interface connection rate is more than 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, and 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, 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 remainder 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 4.3mm and the power of the resistance wire is 1200W; the outer diameter of the ceramic insulating tube is 6mm and the inner diameter is 5mm; the size of the outer stainless steel tube in this embodiment is 8mm in outer diameter, 7mm in inner diameter and 130mm 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0073] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked 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 the stainless steel tube:

[0076] like Figure 1As shown, an inner metal pipe with a heating component placed inside 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 pipe. The preheating temperature of the inner metal pipe 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 pipe 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 insulate the bimetallic interface of the obtained composite pipe. 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 thickness of 30mm is obtained.

[0079] A continuous Fe-Al diffusion phase layer is formed at the aluminum-steel interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment. The interface is well composited, and the bimetallic interface connection rate is 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, 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%; 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, 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 remainder 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 7.5mm and the power of the resistance wire is 2000W; the outer diameter of the ceramic insulating tube is 9mm and the inner diameter is 8mm; the size of the outer stainless steel tube in this embodiment is 12mm in outer diameter, 10mm in inner diameter and 130mm 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0089] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked 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 the stainless steel tube:

[0092] like Figure 1 As shown, an inner metal pipe with a heating component placed inside 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 pipe. The preheating temperature of the inner metal pipe 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 pipe 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 pouring is completed, the resistance wire continues to be energized to insulate the bimetallic interface of the obtained composite pipe. 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 thickness of 25mm is obtained.

[0095] A continuous Fe-Al diffusion phase layer is formed at the aluminum-steel interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment. The interface is well composited, and the bimetallic interface connection rate is 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, 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%; 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, 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 remainder 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 4.3mm and the power of the resistance wire is 1200W; the outer diameter of the ceramic insulating tube is 6mm and the inner diameter is 5mm; the size of the outer stainless steel tube in this embodiment is 8mm in outer diameter, 7mm in inner diameter and 130mm 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0105] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked 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 the stainless steel tube:

[0108] like Figure 1 As shown, an inner metal pipe with a heating component placed inside 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 pipe. The preheating temperature of the inner metal pipe 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 pipe 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 pouring is completed, the resistance wire continues to be energized to insulate the bimetallic interface of the obtained composite pipe. 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 thickness of 50mm is obtained.

[0111] A continuous Fe-Al diffusion phase layer is formed at the aluminum-steel interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment. The interface is well composited, and the bimetallic interface connection rate is 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, 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%; 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, 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 remainder 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 4.3mm and the power of the resistance wire is 1200W; the outer diameter of the ceramic insulating tube is 6mm and the inner diameter is 5mm; the size of the outer stainless steel tube in this embodiment is 8mm in outer diameter, 7mm in inner diameter and 130mm 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0121] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked 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 the stainless steel tube:

[0124] like Figure 1 As shown, an inner metal pipe with a heating component placed inside 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 pipe. The preheating temperature of the inner metal pipe 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 pipe 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 pouring is completed, the resistance wire continues to be energized to insulate the bimetallic interface of the obtained composite pipe. 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 thickness of 30mm is obtained.

[0127] A continuous Fe-Al diffusion phase layer is formed at the aluminum-steel interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this embodiment. The interface is well composited, and the bimetallic interface connection rate is 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 pipe used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe in this comparative example is a 316L stainless steel pipe, 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%; the balance is Fe and unavoidable impurities.

[0131] The outer metal used in the preparation of the aluminum-copper alloy / stainless steel bimetallic composite pipe 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) The stainless steel tube was placed in a 10% by mass NaOH solution and soaked for 10 minutes for alkaline cleaning;

[0137] (3) The stainless steel tube is placed in a 10% hydrochloric acid solution and soaked for 10 minutes for pickling;

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

[0139] Step 2: Place the stainless steel pipe in a common heating furnace, preheat the stainless steel pipe under a nitrogen protective atmosphere to a preheating temperature of 650° C. Take the stainless steel pipe 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 The SEM and EDS images of the composite interface of the aluminum-copper alloy / stainless steel bimetallic composite pipe prepared in this comparative example show that there is no obvious Fe-Al diffusion phase layer between the aluminum and steel, and only a common mechanical bond is formed. There are defects such as pores at the aluminum-steel interface, the mechanical bonding effect is poor, and the bimetallic interface connection rate is 0%.

Claims

1. A method for preparing a bimetallic composite pipe, characterized in that: An inner metal pipe with a heating component placed through it 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.

2. The method for preparing a bimetallic composite pipe according to claim 1, characterized in that: 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 800-2500W.

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. A method for preparing a bimetallic composite pipe according to any one of claims 1 to 3, characterized in that: The inner metal pipe is made of stainless steel; the outer metal is made of aluminum alloy.

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

6. The method for preparing a bimetallic composite pipe according to claim 5, characterized in that: The preheating temperature of the inner metal pipe is 600-800° C., and the protective atmosphere is an argon atmosphere.

7. The method for preparing a bimetallic composite pipe according to claim 6, characterized in that: The pouring temperature of the outer metal material is 700-900° C., and the pouring speed is 0.2 kg / s.

8. The method for preparing a bimetallic composite pipe according to claim 7, characterized in that: The insulation temperature is not less than 600° C., and the insulation time is 60 to 600 seconds.

9. A bimetallic composite pipe prepared by the method for preparing a bimetallic composite pipe according to any one of claims 1 to 8, characterized in that: The wall thickness of the inner metal tube of the bimetallic composite tube is 0.5-2 mm, and the thickness of the outer metal layer is 20-50 mm.

10. The bimetallic composite pipe according to claim 9, characterized in that: The inner metal tube of the bimetallic composite pipe is a stainless steel pipe, 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 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%, the balance is 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.

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