Joint of copper terminal and aluminium conductor and plasma welding method therefor

Abstract

Provided is a joint of a copper terminal and an aluminium conductor. A copper terminal connecting member of the joint is connected to a conductive core of the aluminium conductor by means of a transition welding layer, and the joint can also be provided with a reinforcing welding layer. Further provided is a method for preparing the joint using plasma arc welding. According to the invention, the connection portion of the copper terminal with the aluminium conductor is filled with solder in a plasma arc welding manner, such that copper and aluminium are connected by means of the solder. Damage to an aluminium oxide layer during welding increases the conductivity and can also isolate the copper terminal and the aluminium conductor, thus preventing an electrochemical reaction between the copper and the aluminium, prolonging the service life of the joint of the copper terminal and the aluminium conductor, and ensuring the mechanical and electrical performances of the connection structure.

Description

A copper terminal and aluminum wire joint and a plasma welding method thereof TECHNICAL FIELD

[0001] The present invention belongs to the field of wiring harnesses and relates to a copper terminal and aluminum wire joint and a method for connecting the same by plasma welding. BACKGROUND

[0002] Copper is widely used due to its good electrical conductivity, thermal conductivity and plasticity. However, copper resources are scarce and copper is expensive. Therefore, people have begun to look for alternatives to copper to reduce costs. Aluminum is relatively low in price and also has good electrical conductivity, thermal conductivity and plasticity, so replacing copper with aluminum is the main trend of development at present. However, the performance of aluminum is not as good as that of copper, and many components cannot be completely replaced by aluminum, so there are cases of joint welding between aluminum components and copper components. For example, an aluminum wire is used as a cable, and when connecting such a cable to a copper terminal on various electrical devices, or when connecting with a copper cable, the copper and aluminum contact ends are connected by welding. The copper terminal in the prior art generally includes a connecting piece (or connecting end) and a functional piece (or fixed end) at the rear end of the connecting piece; the connecting piece is used to connect with the aluminum wire; and the functional piece is used to connect with the terminal of an electrical device, such as an automobile engine or a storage battery.

[0003] There are two technical problems that have not been solved for the connection of aluminum and copper: 1) Aluminum is a lively metal, and a dense oxide film is immediately formed on the surface of aluminum in dry air, which prevents further oxidation of aluminum and enables it to be resistant to water, but also greatly reduces the electrical conductivity of the aluminum wire. 2) Copper and aluminum belong to different elements, and the metal inertness of copper is greater than that of aluminum. There is a relatively large electrode potential difference between copper and aluminum, and when these two metals are connected and powered, an electrochemical reaction easily occurs, which causes the aluminum wire to be gradually oxidized, reducing the mechanical strength and electrical conductivity of the aluminum wire.

[0004] In the existing connection technology of wiring harnesses, the connection between the copper terminal and the wire is mainly achieved by crimping, that is, the core of the wire is placed in the connecting piece of the terminal, and the terminal and the wire are mechanically crimped together using a terminal crimping die. However, for the combination of a copper terminal and an aluminum wire, the traditional crimping method cannot solve the electrochemical reaction that occurs between the aluminum wire and the copper terminal over time, and cannot solve the resulting problems of the mechanical and electrical properties of the copper terminal and aluminum wire joint.

[0005] Therefore, a new low-cost method for connecting copper terminals and aluminum wires is urgently needed.

[0006] SUMMARY

[0007] In order to overcome the problems of easy electrochemical corrosion of copper-aluminum connection, easy oxidation of aluminum and reduction of joint strength over time in the prior art, the application provides a joint of copper terminal and aluminum wire and a manufacturing method thereof. The joint and the manufacturing method thereof can avoid copper-aluminum electrochemical corrosion, improve mechanical and electrical properties of the copper-aluminum joint, and increase the service life of the copper-aluminum joint.

[0008] The above object of the application is achieved by the following technical means:

[0009] In one aspect, the application provides a joint of copper terminal and aluminum wire and a manufacturing method thereof. The copper terminal comprises a connecting piece and a functional piece connected to the connecting piece of the copper terminal. The core of the aluminum wire is connected to the connecting piece of the copper terminal. At least the core of the aluminum wire is connected to the connecting piece of the copper terminal through a transition welding layer. The transition welding layer is composed of solder. Specifically, the transition welding layer is formed by filling the gap between the connecting piece of the copper terminal and the aluminum wire after the solder is melted. The penetration depth of the solder accounts for 3%-100% of the length of the connecting piece of the copper terminal. Preferably, the penetration depth of the solder accounts for 30%-100% of the length of the connecting piece of the copper terminal.

[0010] In the application, the joint of the copper terminal and the aluminum wire has a crimping area. The area of the crimping area accounts for at least 1% of the overlapping area of the aluminum wire and the copper terminal. Preferably, the area of the crimping area of the joint of the copper terminal and the aluminum wire accounts for at least 10% of the overlapping area of the aluminum wire and the copper terminal. The transition welding layer is composed of solder. The transition welding layer is formed by filling the gap between the copper terminal and the aluminum wire after the solder is melted. The penetration depth of the solder accounts for 5%-100% of the length of the entire crimping area. Preferably, the penetration depth of the solder accounts for 35%-100% of the length of the entire crimping area.

[0011] In the joint and the welding method of the application, the metal material of the solder is a metal or alloy with a melting point not higher than that of aluminum. As a preferred embodiment, the metal material of the solder contains zinc. Because the melting point of zinc is lower than that of copper and aluminum, the temperature can be controlled to melt zinc but not melt the joint of the copper terminal and the aluminum wire during the heating and melting of the solder in the processing process, thereby affecting the mechanical and electrical properties of the joint. Moreover, zinc is relatively low in price. More preferably, the zinc accounts for more than 30% of the total weight of the solder. More preferably, the zinc accounts for more than 60% of the total weight of the solder.

[0012] As a preferred embodiment, the joint of the copper terminal and the aluminum wire further has a reinforcing welding layer. Preferably, the reinforcing welding layer wraps the end face of the core of the aluminum wire. The thickness of the reinforcing welding layer is 0-15 mm. More preferably, the thickness of the reinforcing welding layer is 1.5-5.5 mm.

[0013] The joint of the copper terminal and the aluminum wire is isolated by the transition welding layer, or by the transition welding layer and the reinforcing welding layer, which effectively reduces the electrochemical corrosion of copper and aluminum. The reinforcing welding layer wraps the end face of the aluminum wire, and the core of the copper terminal and the wire does not contact air and moisture, further reducing corrosion. In addition, the transition welding layer and the reinforcing welding layer tightly fix the joint of the copper terminal and the aluminum wire, effectively increasing the pull-out force of the joint.

[0014] In the present application, the material of the copper terminal is copper or copper alloy; preferably, the connecting part of the copper terminal is flat, arc-shaped or hollow column-shaped with open ends, wherein the side surface of the hollow column-shaped body can be closed or not closed.

[0015] As a preferred embodiment, the connecting part of the copper terminal is integrated with the functional part. The connecting part is the part connecting the copper terminal and the aluminum wire; the functional part is the fixed area connecting the copper terminal and the electrical device, which is the main area for installing and fixing the end of the cable and realizing the electrical connection between the copper terminal and the electrical device.

[0016] As a preferred embodiment, the surface of the copper terminal further comprises a plating layer; preferably, the thickness of the plating layer is 3 μm to 5000 μm; more preferably, 5 μm to 1000 μm. The plating layer can be attached to the copper terminal by electroplating, electromagnetic welding, arc spraying or pressure welding, etc.

[0017] The thickness of the spacing metal layer is 3 μm to 5000 μm. As a preferred embodiment, the thickness of the spacing metal layer is 5 μm to 1000 μm. If the thickness of the spacing metal layer is less than 3 μm, the spacing metal layer is easily damaged by the copper terminal and the aluminum wire during pressure welding or welding, so that the copper and aluminum contact, resulting in that the spacing metal layer does not play the role of spacing copper and aluminum; when the thickness of the spacing metal layer is greater than 5000 μm, the thickness of the spacing metal layer leads to the increase of the voltage drop of the joint of the copper terminal and the aluminum wire, because the electrical conductivity of most spacing metal layer materials is not as good as that of copper and aluminum; in addition, the amount of spacing metal increases, the cost increases, but the electrical and mechanical properties of the joint of the copper terminal and the aluminum wire do not increase significantly. Generally, when electroplating or arc spraying is used to fix the spacing metal layer, the thickness of the spacing metal layer can reach 3 μm to 1000 μm; when electromagnetic welding or pressure welding is used, the thickness of the spacing metal layer can reach 1000 μm to 5000 μm; therefore, the thickness of the spacing metal layer in the present application is set in the range of 3 μm to 5000 μm.

[0018] The metal material of the plating layer is one or a combination of several metals selected from the group consisting of chromium or chromium alloy, zinc or zinc alloy, tin or tin alloy, titanium or titanium alloy, zirconium or zirconium alloy, nickel or nickel alloy, silver or silver alloy, gold or gold alloy; more preferably, the metal material of the plating layer is one or a combination of several metals selected from the group consisting of zinc or zinc alloy, tin or tin alloy, nickel or nickel alloy.

[0019] In the joint and welding method of the present application, the core of the aluminum wire can be aluminum or aluminum alloy. The aluminum wire can be a solid wire or a multi-core wire.

[0020] In another aspect, the present application also discloses a plasma welding method for the joint of the copper terminal and the aluminum wire, which comprises the following steps:

[0021] 1) assembling the core of the aluminum wire with the connecting part of the copper terminal;

[0022] 2) pressing the core of the aluminum wire and the connecting part of the copper terminal to form a press-fit area;

[0023] 3) feeding the solder to the copper terminal; preferably, feeding the solder to the connecting part of the copper terminal; preferably, feeding the solder to the press-fit area between the aluminum wire and the copper terminal, and then using plasma arc welding to melt the solder and fill it into the gap between the copper terminal and the aluminum wire to form a transition welding layer.

[0024] As another embodiment, the solder can be pre-filled before the connection, and the welding method comprises the following steps:

[0025] 1) wrapping the core of the aluminum wire with solder, or at least covering the part of the connecting part of the copper terminal that is in contact with the core of the aluminum wire, and then assembling the core of the aluminum wire with the connecting part of the copper terminal;

[0026] 2) pressing the core of the aluminum wire, the solder, and the connecting part of the copper terminal to form a press-fit area;

[0027] 3) using plasma arc welding to melt the solder between the copper terminal and the aluminum wire, and then filling it into the gap between the copper terminal and the aluminum wire to form a transition welding layer.

[0028] As a preferred embodiment of the above two methods, in step 3), the solder is first melted to form a reinforcing welding layer, and then the welding process is continued to fill the solder into the gap between the copper terminal and the aluminum wire to form a transition welding layer; preferably, the thickness of the reinforcing welding layer is 0-15 mm; more preferably, the thickness of the reinforcing welding layer is 1.5-5.5 mm.

[0029] In the above method for preparing the joint of the copper terminal and the aluminum wire, the following supplementary explanations are provided:

[0030] In step 2), the area of the crimping region of the joint of the copper terminal and the aluminum wire is at least 1% of the area of the overlapping region of the aluminum wire and the copper terminal; preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire is at least 10% of the area of the overlapping region of the aluminum wire and the copper terminal.

[0031] In step 2), the shrinkage rate of the aluminum wire after crimping is between 70% and 90%, and more preferably between 75% and 85%. When the compression rate of the aluminum wire is lower than 70%, the aluminum wire is compressed into a thin wire, the tension borne by the aluminum wire is small, resulting in insufficient mechanical properties of the terminal and the aluminum wire, and after the aluminum wire is compressed, it is difficult for the solder to enter the gap of the aluminum wire, reducing the insulation effect of the solder on the terminal and the aluminum wire; when the compression rate is higher than 90%, the gap between the aluminum wire and the copper terminal is too large, the contact is insufficient, resulting in insufficient mechanical and electrical properties of the joint of the aluminum wire and the copper terminal.

[0032] In step 3), the ionization and protective gas of the plasma welding can be nitrogen, argon, helium, neon, krypton or xenon, and more preferably argon.

[0033] In step 3), the welding current of the plasma welding is between 5A and 100A, and more preferably between 20A and 80A.

[0034] In step 3), the flow rate of the ionization gas is 1-5 liters per minute, and the flow rate of the protective gas is 3-12 liters per minute; more preferably, the flow rate of the ionization gas is 2-3 liters per minute, and the flow rate of the protective gas is 5-10 liters per minute.

[0035] In step 3), the included angle between the welding torch of the plasma welding and the axis of the copper terminal is less than 45°, and more preferably less than 20°.

[0036] In step 3), after the joint of the copper terminal and the aluminum wire is welded using the plasma welding, the penetration depth of the solder is 3%-100% of the length of the copper terminal connector; more preferably, the penetration depth of the solder is 30%-100% of the length of the copper terminal connector; it has been verified through experiments that the more the penetration depth accounts for the proportion of the entire connector length, the better the mechanical and electrical properties of the connector are, and when the penetration depth accounts for less than 3% of the entire connector length, the mechanical and electrical properties of the connector are significantly reduced.

[0037] In step 3), after the plasma welding, the penetration depth of the solder accounts for 5%-100% of the length of the entire compression region; preferably, the penetration depth of the solder accounts for 35%-100% of the length of the entire compression region. It has been verified by experiments that the more the penetration depth accounts for the entire compression region, the better the mechanical and electrical properties of the connector are. When the penetration depth accounts for less than 5% of the entire compression region, the mechanical and electrical properties of the connector are significantly reduced.

[0038] In step 3), the solder material is a metal or alloy with a melting point not higher than aluminum; preferably, the solder material is a metal or alloy with a melting point not higher than aluminum; more preferably, the solder material is zinc; more preferably, the zinc accounts for more than 30% of the total weight of the solder; more preferably, the zinc accounts for more than 60% of the total weight of the solder.

[0039] The present application first applies plasma arc welding combined with solder to the production of copper terminals and aluminum wire joints. Currently, the production of copper terminals and aluminum wire joints mainly uses compression, that is, mechanical compression is used to realize the connection between the copper terminal and the aluminum wire. In the production of wire harnesses, no one uses plasma arc welding to produce copper terminals and aluminum wire joints.

[0040] Firstly, pure plasma arc welding cannot guarantee the welding strength and stability of the copper terminal and the aluminum wire joint, and cannot meet the mechanical strength and stability requirements of the wire harness for the copper terminal and the aluminum wire joint. If the copper terminal and the aluminum wire are simply in contact and welded, the melting points of aluminum and copper are 660 DEG C and 1083 DEG C respectively, and they cannot be melted synchronously during welding. There are brittle metal compounds such as copper-rich metals in the weld, and the welding quality is very poor, which cannot meet the electrical and mechanical requirements of the wire harness field for the copper terminal and the aluminum wire joint.

[0041] The present application applies solder and plasma arc welding together in the connection of copper terminals and aluminum wires to ensure the mechanical and electrical properties of the copper terminal and the aluminum wire joint. More importantly, the solder melts to form a transition welding layer in the connection gap between the aluminum wire and the copper terminal; or the solder first forms a reinforcing welding layer and then continues the welding process, so that the solder fills the gap between the copper terminal and the aluminum wire to form a transition welding layer.

[0042] The transition welding layer insulates the aluminum conductor core from the copper terminal and mostly insulates the copper terminal from the aluminum conductor joint and the outside air and water, effectively avoiding the electrochemical corrosion caused by the direct contact between the copper terminal and the aluminum conductor core, reducing the potential difference between copper and aluminum through the transition welding layer, improving the service life of the copper terminal and the aluminum conductor joint, and ensuring the mechanical properties and long-term electrical properties of the copper terminal and the aluminum conductor joint. The reinforcing welding layer in the application can further improve the mechanical properties of the copper terminal and the aluminum conductor joint, and can completely isolate the aluminum conductor core from the outside air and water, further prolonging the service life of the copper terminal and the aluminum conductor joint.

[0043] In addition, the stability, heat output and temperature of the plasma arc welding are higher than those of general electric arc welding. Compared with general electric arc welding, it has greater penetration force and welding speed. The welding time is shortened by at least 20% or more than ordinary electric arc welding, the power consumption is reduced by at least 30% or more, and the manufacturing cost of the copper terminal and the aluminum conductor joint is significantly reduced.

[0044] It should be particularly pointed out that before the copper terminal and the conductor core of the aluminum conductor are welded by solder and plasma arc welding, the copper terminal and the aluminum conductor are first crimped, which can enhance the mechanical properties and electrical properties of the copper-aluminum connection terminal. Although the use of plasma arc welding and solder can improve the mechanical properties and electrical properties to a certain extent, the performance improvement is limited because the solder is only distributed on the surface of the wire by capillary action after melting and forms a connection with the copper terminal. As a preferred embodiment, the copper terminal and the aluminum wire are normally mechanically crimped, and then plasma arc welding is performed, which not only enhances the mechanical properties but also reduces the potential difference between copper and aluminum by using solder to ensure electrical properties. Non-obviously, the mechanical properties and electrical properties of the copper terminal and the aluminum conductor joint after plasma arc welding are enhanced by the cooperation of solder and crimping. Especially outstanding is that when more than 60% zinc is used as solder, combined with plasma arc welding and crimping, the maximum voltage drop of the copper terminal and the aluminum conductor joint is reduced by about 15%, and the maximum tensile force is increased by about 20%.

[0045] Advantages achieved by the application:

[0046] 1. The application first applies the transition welding layer formed by combining plasma arc welding and solder to the manufacturing of the copper terminal and the aluminum conductor joint, which not only enhances the mechanical properties and electrical properties of the copper terminal and the aluminum conductor joint, but also effectively avoids the electrochemical corrosion caused by the direct contact between the copper terminal and the aluminum conductor core, reduces the potential difference between copper and aluminum through the transition welding layer, and improves the service life of the copper terminal and the aluminum conductor joint.

[0047] 2. The reinforced welding layer in this invention can further improve the mechanical properties of the copper terminal and aluminum wire connector, and can completely isolate the aluminum wire core from contact with the outside air and water, thus further extending the service life of the copper terminal and aluminum wire connector.

[0048] 3. During the welding process of copper terminals and aluminum wire joints using plasma arc welding, the molten solder, heated copper terminals and aluminum wires are all under the protection of the inert gas of plasma arc welding, which isolates oxygen in the air from further oxidation of the aluminum wires, ensuring the electrical performance and service life of the copper terminals and aluminum wire joints after welding.

[0049] 4. Before welding the copper terminals and aluminum conductor cores with solder and plasma arc welding, crimping the copper terminals and aluminum conductors first can enhance the mechanical and electrical properties of the copper-aluminum connection terminals. The maximum voltage drop at the copper terminal and aluminum conductor joint is about 15%, and the maximum increase in pull-out force is about 20%.

[0050] 5. Plasma arc welding offers higher stability, heat generation, and temperature compared to conventional arc welding. It boasts greater penetration and welding speed compared to arc welding. Welding time is reduced by at least 20% and power consumption by at least 30% compared to conventional arc welding, significantly lowering the manufacturing cost of copper terminals and aluminum wire connectors. Furthermore, the stable processing of plasma arc welding effectively ensures the quality of both copper terminals and aluminum wire connectors.

[0051] 6. Traditional crimping methods for manufacturing copper terminals and aluminum wire connectors require the copper terminal connector to be arc-shaped or a hollow column with open ends. However, this invention is applicable to the manufacturing of copper terminals and aluminum wire connectors of various shapes, effectively solving the limitations of crimping and other methods in the selection of copper terminal shapes. Attached Figure Description

[0052] Figure 1 illustrates an example design of a copper terminal;

[0053] Figure 2 illustrates an example pattern of aluminum wire;

[0054] Figure 3 illustrates an example of a connection between an aluminum wire and a copper terminal;

[0055] Figure 4 shows an example top view of the copper terminals and aluminum wires after the connection is completed;

[0056] Figure 5 shows an example of the longitudinal section of the copper terminal and multi-core aluminum wire after welding is completed.

[0057] Figure 6 shows an example of the longitudinal section of the copper terminal and solid aluminum wire after welding is completed;

[0058] Figure 7 shows an example of the cross-sectional view of the copper terminal and aluminum wire after welding is completed;

[0059] Figure 8 illustrates a copper terminal with a barrel-shaped connecting piece suitable for use in the present application;

[0060] Figure 9 illustrates an example of the copper terminal in Figure 8 after welding according to the method of the present application;

[0061] Figure 10 illustrates an example of a side view of the flat copper terminal and aluminum wire after the connection is completed;

[0062] Furthermore, the reference numerals in Figures 1-10 are explained as follows:

[0063] 1. Copper terminal; 1.1. Functional piece; 1.2. Connecting piece;

[0064] 2. Aluminum wire; 2.1. Insulating layer; 2.2. Aluminum core;

[0065] 3. Transition welding layer;

[0066] 4. Reinforced welding layer;

[0067] 5. Terminal plating layer. DETAILED DESCRIPTION

[0068] The technical solutions of the present application are further explained below through specific examples, which do not represent a limitation on the scope of protection of the present application. Some non-essential modifications and adjustments made by others according to the concept of the present application still fall within the scope of protection of the present application.

[0069] Example 1: A joint of a copper terminal and an aluminum wire

[0070] As shown in Figures 1 and 8, the copper terminal 1 contains a connecting piece 1.2, and a functional piece 1.1 at the back end thereof.

[0071] As shown in Figure 2, the aluminum wire 2 is a multi-core wire containing an aluminum core 2.2 and an insulating layer 2.1.

[0072] The core of the aluminum wire 2 is connected to the connecting piece 1.2, and specifically, as shown in the longitudinal section view of the joint in Figure 5. There is a gap between the front end of the aluminum wire and the connecting piece, containing a transition welding layer 3, and at the front end of the aluminum wire, there is also a reinforced welding layer 4, which completely covers the front end face of the aluminum wire and forms an integral part with the transition welding layer.

[0073] As shown in Figure 3, the thickness of the reinforced welding layer is 0-15 mm; preferably, the thickness of the reinforced welding layer is 1.5-5.5 mm.

[0074] As shown in Fig. 5, the copper terminal and the aluminum wire core have a pressure contact area, and the area of the pressure contact area is at least 1% of the area of the overlapping region of the aluminum wire and the copper terminal; preferably, the area of the pressure contact area of the copper terminal and the aluminum wire joint is at least 10% of the area of the overlapping region of the aluminum wire and the copper terminal.

[0075] Example 2: A joint of a copper terminal and an aluminum wire

[0076] Example 2: A joint of a copper terminal and an aluminum wire

[0077] Example 3: A joint of a copper terminal and an aluminum wire

[0078] Example 3: A joint of a copper terminal and an aluminum wire

[0079] Example 4: A joint of a copper terminal and an aluminum wire

[0080] Example 4: A joint of a copper terminal and an aluminum wire

[0081] As shown in Fig. 5, the surface of the copper terminal also has a plating layer 5;

[0082] Preferably, the thickness of the plating layer is 3 μm to 5000 μm; more preferably, the thickness of the plating layer is 5 μm to 1000 μm;

[0083] Preferably, the plating layer is attached to the copper terminal by electroplating, electromagnetic welding, arc spraying, or pressure welding;

[0084] The electroplating method comprises the following steps: 1, the plating metal is at the anode; 2, the object to be plated is at the cathode; 3, the anode and the cathode are connected with the electrolyte solution of the metal positive ions plated; 4, after a direct current power supply is connected, the metal of the anode is oxidized (loses electrons), and the positive ions in the solution are reduced (gain electrons) into atoms and accumulated on the surface of the cathode.

[0085] The electromagnetic welding method comprises the following steps: 1, the two metals to be pressure welded are stacked; 2, the electromagnetic welding device forms a high-pressure magnetic field in the welding area, so that the two metals are pushed by the electromagnetic force to collide with each other at the atomic energy level, thereby welding the two metals together.

[0086] The arc spraying method is to transport the spacer metal to the arc area and atomize it, and then spray it at high speed to the surface of the workpiece under the action of compressed gas to form an arc spraying layer.

[0087] The method of pressure welding comprises the following steps: 1, stacking two metals to be pressure welded; 2, applying pressure to make the surfaces to be welded diffuse sufficiently to realize atomic combination; 3, according to different metals and pressure sources, the welding effect can be improved and the welding time can be shortened by increasing the temperature.

[0088] Preferably, the metal material of the plating layer is one or a combination of several metals selected from the group consisting of chromium or chromium alloy, zinc or zinc alloy, tin or tin alloy, titanium or titanium alloy, zirconium or zirconium alloy, nickel or nickel alloy, silver or silver alloy, gold or gold alloy; more preferably, the metal material of the plating layer is one or a combination of several metals selected from the group consisting of zinc or zinc alloy, tin or tin alloy, nickel or nickel alloy.

[0089] Example 5: A joint of a copper terminal and an aluminum wire

[0090] Example 1 is repeated, and the differences are as follows: the aluminum wire is a solid wire

[0091] Example 6: A plasma welding method of a copper terminal and an aluminum wire

[0092] As shown in FIG. 1, the copper terminal 1 of the present application has a functional part 1.1 and a connecting part 1.2 connected to the functional part. In this embodiment, the connecting part is wing-shaped, and the end surface thereof is in a U-shaped structure.

[0093] As shown in FIG. 2, the aluminum wire 2 of the present application has a multi-core aluminum core 2.2 and an outer insulating layer 2.1, and part of the insulating layer is stripped according to the size of the copper terminal before crimping.

[0094] The steps of manufacturing the joint of the copper terminal and the aluminum wire are as follows:

[0095] As shown in FIG. 3, the insulating layer of the aluminum wire is stripped, and the aluminum wire is placed in the wing-shaped connecting part of the copper terminal, and the aluminum wire and the wing-shaped connecting part of the copper terminal are crimped using a crimping die. The area of the crimping region is at least 1% of the area of the overlapping region of the aluminum wire and the copper terminal; preferably, the area of the crimping region of the joint of the copper terminal and the aluminum wire is at least 10% of the area of the overlapping region of the aluminum wire and the copper terminal.

[0096] After crimping, the compression rate of the aluminum wire core is between 70% and 90%; preferably, the compression rate of the aluminum wire core is between 75% and 85%, so as to ensure the mechanical properties and electrical conductivity of the joint of the copper terminal and the aluminum wire. The joint of the copper terminal and the aluminum wire after crimping is shown in FIG. 4.

[0097] Specifically, the solder is fed to the copper terminal, preferably to the connecting part of the copper terminal; preferably, the solder is fed to the crimping region of the aluminum wire and the copper terminal, and then plasma arc welding is used to melt the solder and fill it into the connection gap between the copper terminal and the aluminum wire through capillary action to form a transition welding layer.

[0098] The ionized and protective gas of the plasma arc welding can be nitrogen, argon, helium, neon, krypton or xenon, and more preferably argon; the flow rate of the ionized gas is 1-5 liters per minute, and the flow rate of the protective gas is 3-12 liters per minute; more preferably, the flow rate of the ionized gas is 2-3 liters per minute, and the flow rate of the protective gas is 5-10 liters per minute; during the welding process, the angle between the welding torch of the plasma arc welding and the copper terminal is less than 45°, and more preferably less than 20°; the welding current of the plasma arc welding is 5A-100A, and more preferably 20A-80A;

[0099] During the welding process, the center region of the welding temperature can reach 400-550°C, so that the solder is melted to form the reinforced welding layer 4, and then the welding process is continued to make the solder fill the gap between the copper terminal and the aluminum wire to form the transition welding layer 3; the longitudinal section view of the final state of the copper terminal and aluminum wire joint is shown in Fig. 5; the depth of the molten solder accounts for 3%-100% of the length of the copper terminal connector; more preferably, the depth of the molten solder accounts for 30%-100% of the length of the copper terminal connector; preferably, the depth of the molten solder accounts for 5%-100% of the length of the entire crimping region, and more preferably 35%-100% of the entire crimping region.

[0100] The metal material of the solder is a metal or alloy with a melting point not higher than that of aluminum, so that the conductor core of the aluminum wire is not melted during the welding and melting, so that the solder can penetrate into the gap between the aluminum wire conductor core and the copper terminal through capillary action to form the transition welding layer or, in this embodiment, first form the reinforced welding layer and then form the transition welding layer.

[0101] As shown in Fig. 7, the cross-sectional view of the crimping part of the copper terminal connector and the aluminum wire, in which the solder is tightly fused between the copper terminal connector and the aluminum wire, not only ensures the isolation of air and water from the corrosion of the aluminum wire conductor core, effectively avoids the electrochemical corrosion of air and water to the copper terminal and aluminum wire joint, but also can conduct electricity well with copper and aluminum, ensuring the mechanical properties, electrical properties and service life of the copper terminal and aluminum wire joint.

[0102] Example 7 A plasma arc welding method for a copper terminal and an aluminum wire

[0103] Repeat Example 6 with the following differences: the shape of the copper terminal connector is flat or arc-shaped structure; during the welding, the solder is first fed to the copper terminal, preferably to the connector of the copper terminal; preferably, the solder is fed to the crimping region of the aluminum wire and the copper terminal, and then plasma arc welding is used to melt the solder and fill it into the gap between the copper terminal and the aluminum wire to form the transition welding layer. The molten solder only fills the gap between the copper terminal connector and the aluminum wire to form the transition welding layer, and does not form a reinforced welding area.

[0104] Example 8 A method of plasma welding a copper terminal and an aluminum wire

[0105] Example 6 is repeated with the following differences:

[0106] 1. After stripping the insulation layer of the aluminum wire, a solid thin layer of solder is wrapped around the core of the aluminum wire after stripping the insulation layer, and then placed into the connecting part of the copper terminal for crimping.

[0107] 2. The connecting part of the copper terminal is a hollow columnar structure with openings at both ends, and the side surface is closed or not closed.

[0108] Example 9 A method of connecting a copper terminal and an aluminum wire

[0109] Example 6 is repeated with the following differences:

[0110] After stripping the insulation layer of the aluminum wire, a solid thin layer of solder is wrapped around the part of the copper terminal connecting part in contact with the core of the aluminum wire, and then the core of the aluminum wire is placed into the connecting part of the copper terminal for crimping.

[0111] Example 10 Effect of different connection methods on voltage drop and pull force of the joint of copper terminal and aluminum wire

[0112] Using copper terminals and aluminum wires of the same specification and structure, the joints of copper terminals and aluminum wires are made in the following 5 ways, 10 samples for each method, a total of 50 samples.

[0113] Method 1: Crimping

[0114] The aluminum wire is directly crimped into the copper terminal using a mold.

[0115] Method 2: Plasma arc welding

[0116] Using plasma arc welding, the copper terminal and the aluminum wire are directly welded together. The welding current of the plasma arc welding is 40 A, the flow rate of the ionizing gas argon is 2.5 liters / minute, and the flow rate of the protective gas argon is 7.5 liters / minute; the angle between the plasma welding torch and the axial direction of the copper terminal is 15°.

[0117] Welding method 3: Crimping + plasma arc welding

[0118] Referring to Example 6, the aluminum wire is crimped into the copper terminal using a mold, and then the crimped copper terminal and aluminum wire are welded together using plasma arc welding. After crimping, the compression rate of the aluminum wire is 80%; the welding current of the plasma arc welding is 40 A. The flow rate of the ionizing gas argon is 2.5 liters / minute, and the flow rate of the protective gas argon is 7.5 liters / minute; the angle between the plasma welding torch and the axial direction of the copper terminal is 15°.

[0119] Welding method 4: Plasma arc welding + solder

[0120] The solder is fed to the connecting part of the copper terminal, and the copper terminal and the aluminum wire are welded together by using the plasma arc welding. The welding current of the plasma arc welding is 40 A;

[0121] The solder contains 90% zinc and 10% aluminum, the flow rate of the ionized gas argon is 2.5 L / min, the flow rate of the shielding gas argon is 7.5 L / min, and the included angle between the welding torch of the plasma welding and the axial direction of the copper terminal is 15°.

[0122] Welding method 5: Crimping + plasma arc welding + solder

[0123] The aluminum wire is crimped into the connecting part of the copper terminal by using a mold. The solder is fed to the connecting part of the copper terminal, and the crimped copper terminal and the aluminum wire are welded together by using the plasma arc welding. The welding current of the plasma arc welding is 40 A; the solder is 90% zinc and 10% aluminum; the compression rate of the aluminum wire after crimping is 80%, the flow rate of the ionized gas argon is 2.5 L / min, the flow rate of the shielding gas argon is 7.5 L / min, and the included angle between the welding torch of the plasma welding and the axial direction of the copper terminal is 15°.

[0124] After the joints of the copper terminal and the aluminum wire are made by using the above-mentioned five methods, the voltage drop and the pulling force of the five groups of 50 samples are tested by using the same test method. The test parameters of each group of samples are averaged, and the test results are shown in Table 1.

[0125] Table 1 Comparison of voltage drop and pulling force of joints of copper terminal and aluminum wire made by five different methods

[0126]

[0127] As shown in Table 1, the joints of the copper terminal and the aluminum wire made by only crimping or only plasma arc welding (method 1 and method 2) have low pulling force and high voltage drop, which cannot meet the mechanical and electrical performance requirements of the joints of the copper terminal and the aluminum wire in use. Although the method 3 can improve the pulling force of the joints of the copper terminal and the aluminum wire, the voltage drop is still high, which still cannot meet the electrical performance requirements of the joints of the copper terminal and the aluminum wire in use. The joints of the copper terminal and the aluminum wire made by the method 4 and the method 5 of the present application meet the mechanical and electrical performance requirements of the joints of the copper terminal and the aluminum wire in use. Obviously, the mechanical and electrical performance of the joints made by the method of crimping + plasma arc welding + solder of the copper terminal and the aluminum wire in the present application is the best among the above-mentioned five methods.

[0128] Example 11 Effect of different proportions of zinc-based solder on the performance of the joints of the copper terminal and the aluminum wire

[0129] The soldering method is according to the method of Example 6, with the control variable method, the welding current is 40 A, the flow rate of ionized argon is 3 liters / minute, the flow rate of protective argon is 8 liters / minute, the compression rate of the aluminum wire is 80%, and the angle between the plasma torch and the copper terminal is 15°. The solder is made according to the different zinc base proportions, and the copper terminal and the aluminum wire joint are made according to the method of Example 3. The prepared joints are tested according to the same test method, and the average value is taken from 100 samples. The test results are shown in Table 2.

[0130] Table 2 Influence of different zinc base proportions of solder on joint performance

[0131] No. Metal composition of solder Voltage drop (mV) Tensile force (N) 1 100% Zn 2.7232 38.3 90% Zn 10% Al 2.8132 36.7 80% Zn 20% Al 2.9532 29.5 70% Zn 30% Al 3.0832 24.6 60% Zn 40% Al 3.5930 12.7 50% Zn 50% Al 3.6829 56.3 40% Zn 60% Al 3.7928 75.3 30% Zn 70% Al 3.9127 65.1 20% Zn 80% Al 4.7824 97.6 10% Zn 90% Al 5.7524 01.2

[0132] From Table 2, it can be seen that the higher the proportion of zinc in the solder, the lower the voltage drop of the copper terminal and the aluminum wire, that is, the better the electrical performance of the copper terminal and the aluminum wire joint.

[0133] When the solder with a zinc base proportion of more than 30% of the total weight of the solder is used to make the joint of the copper terminal and the aluminum wire, the tensile force performance of the joint meets the mechanical performance requirements of most copper terminal and aluminum wire joints. When the solder with a zinc base proportion of more than 60% of the total weight of the solder is used to make the joint of the copper terminal and the aluminum wire, the tensile force performance of the joint can completely meet the mechanical performance requirements of the copper terminal and the aluminum wire joint.

[0134] Example 12 Influence of the compression rate of the core of the aluminum wire on the performance of the copper terminal and the aluminum wire joint

[0135] To test the influence of the different compression rates of the aluminum conductor core on the performance of the copper terminal and aluminum conductor joint, the present embodiment uses the method of controlling variables to produce different joints as shown in Table 3 using the production method of the copper terminal and aluminum conductor joint of Example 6. Among them, the welding current is 40 A, the flow rate of ionized argon gas is 3 L / min, the flow rate of protective argon gas is 8 L / min, the solder contains 90% zinc and 10% aluminum, and the angle between the plasma welding torch and the copper terminal axis is 15°. The number of samples of the joint obtained by each method is 10, and the average value is taken as the test result. The compression rate and test results are shown in Table 3.

[0136] Table 3 Influence of different compression rates of the aluminum conductor core on the performance of the copper terminal and aluminum conductor joint

[0137] No. Compression rate of the aluminum conductor Voltage drop (mV) Pulling force (N) 165% 3.96 206 59.12 70% 3.56 263 8.43 75% 3.27 299 7.54 80% 3.05 326 1.25 85% 3.19 292 18.76 90% 3.51 257 5.47 95% 4.36 210 95.3

[0138] According to the test results in the present table, after crimping, the compression rate of the aluminum conductor core is between 70% and 90%, and the electrical and mechanical properties of the copper terminal and aluminum conductor joint are better. More preferably, after crimping, the compression rate of the aluminum conductor core is between 75% and 85%, and the electrical and mechanical properties of the copper terminal and aluminum conductor joint are more outstanding.

[0139] Example 13 Influence of different thicknesses of the reinforcing solder layer on the pulling force and voltage drop of the copper terminal and aluminum conductor joint

[0140] To prove the influence of different thicknesses of the reinforcing solder layer on the performance of the copper terminal and aluminum conductor joint, 17 groups of samples with different thicknesses of the reinforcing solder layer were produced, each group having 10 samples, and then the average value of the test results of each thickness of the reinforcing solder layer was filled in the table by testing the pulling force and voltage drop of the copper terminal and aluminum conductor joint, as shown in Table 4.

[0141] The welding method refers to Example 6, wherein the solder is 90% zinc and 10% aluminum, the flow rate of ionized argon gas is 2.5 L / min, the flow rate of protective argon gas is 7.5 L / min, and the angle between the plasma welding torch and the copper terminal axis is 15°.

[0142] As can be seen from the data in Table 4, when the thickness of the reinforcing solder layer of the copper terminal and aluminum conductor joint exceeds 15 mm, the pulling force and voltage drop performance of the copper terminal and aluminum conductor joint begins to decrease significantly. Therefore, the thickness of the reinforcing solder layer is selected to be 0-15 mm, and when the thickness of the reinforcing solder layer is 1.5 mm-5.5 mm, the pulling force and voltage drop performance of the copper terminal and aluminum conductor joint is better.

[0143] Table 4 Effect of different thickness of reinforced solder layer on the performance of copper terminal and aluminum wire joint

[0144]

[0145]

[0146] Example 14 Effect of different solder penetration depth on the performance of copper terminal and aluminum wire joint

[0147] In order to verify the effect of the penetration depth on the pull force and voltage drop of the copper terminal and aluminum wire joint, 44 groups of soldered samples with different penetration depths were prepared, 10 samples in each group.

[0148] The welding method refers to Example 6, wherein the solder is 90% zinc and 10% aluminum, the flow rate of ionized gas argon is 2.5 liters / minute, the flow rate of protective gas argon is 7.5 liters / minute; the angle between the plasma welding torch and the copper terminal axis is 15°.

[0149] As can be seen from Table 5 below, the greater the ratio of the penetration depth to the length of the joint or the length of the crimping area, the better the mechanical and electrical properties of the copper terminal and aluminum wire joint. However, when the penetration depth is less than 5% of the length of the crimping area, or when the penetration depth is less than 3% of the length of the joint, the mechanical and electrical properties of the copper terminal and aluminum wire joint are significantly reduced. When the penetration depth of the solder is 35%-100% of the crimping area of the copper terminal and aluminum wire joint, or when the penetration depth of the solder is 30%-100% of the length of the joint, the mechanical and electrical properties of the copper terminal and aluminum wire joint are better.

[0150] Table 5 Effect of different solder penetration depth on the pull force and voltage drop of the copper terminal and aluminum wire joint

[0151]

[0152]

[0153] Example 15 Effect of different crimping area on the performance of copper terminal and aluminum wire joint

[0154] In order to verify the effect of the crimping area of the copper terminal and aluminum wire joint on the pull force and voltage drop of the joint, 12 groups of soldered samples with different crimping areas were prepared, 10 samples in each group.

[0155] The soldering method is according to example 6, wherein the solder is 80% zinc and 20% aluminum, the flow rate of the ionizing gas is 2.5 liters / minute, the flow rate of the shielding gas is 7.5 liters / minute; the angle between the plasma torch and the copper terminal is 20°.

[0156] Table 6 Effect of the ratio of the crimping area to the overlapping area of the aluminum wire and the copper terminal on the tensile strength and voltage drop of the copper terminal and aluminum wire joint

[0157]

[0158] From the above table 6, it can be seen that the more the ratio of the crimping area to the overlapping area of the aluminum wire and the copper terminal, the better the mechanical and electrical properties of the joint. However, when the ratio of the crimping area to the overlapping area of the aluminum wire and the copper terminal is less than 1%, the mechanical and electrical properties of the joint are significantly reduced. Therefore, the crimping area is selected to be at least 1% of the overlapping area of the aluminum wire and the copper terminal, preferably, the crimping area of the copper terminal and aluminum wire joint is at least 10% of the overlapping area of the aluminum wire and the copper terminal.

Claims

1. A joint of a copper terminal and an aluminum wire, the copper terminal comprising a connecting member and a functional member connected to the connecting member of the copper terminal, the core of the aluminum wire being connected to the connecting member of the copper terminal, characterized in that, At least the conductor core of the aluminum wire is connected to the copper terminal connector through a transition welding layer.

2. The joint of a copper terminal and an aluminum wire according to claim 1, characterized in that, The copper terminal and the aluminum wire joint have a crimping area, and the area of the crimping area accounts for at least 1% of the area of the overlapping area between the aluminum wire and the copper terminal; preferably, the area of the crimping area of the copper terminal and the aluminum wire joint accounts for at least 10% of the area of the overlapping area between the aluminum wire and the copper terminal.

3. The joint of a copper terminal and an aluminum wire according to claim 1, characterized in that, The transition welding layer is composed of solder, and the penetration depth of the solder accounts for 3%-100% of the length of the copper terminal connector; preferably, the penetration depth of the solder accounts for 30%-100% of the length of the copper terminal connector.

4. The joint of a copper terminal and an aluminum wire according to claim 2, characterized in that, The transition welding layer is composed of solder, and the penetration depth of the solder accounts for 5%-100% of the length of the entire crimping area; preferably, the penetration depth of the solder accounts for 35%-100% of the length of the entire crimping area.

5. The joint of a copper terminal and an aluminum wire according to claim 3 or 4, characterized in that, The metal material of the solder is a metal or alloy with a melting point not higher than that of aluminum; preferably, the metal material of the solder contains zinc; more preferably, the zinc accounts for more than 30% of the total weight of the solder; more preferably, the zinc accounts for more than 60% of the total weight of the solder.

6. The joint of a copper terminal and an aluminum wire according to claim 1, characterized in that, The joint of the copper terminal and the aluminum wire also has a strengthening welding layer; Preferably, the strengthening welding layer wraps the end face of the conductor core of the aluminum wire; Preferably, the thickness of the strengthening welding layer is 0-15 mm; more preferably, the thickness of the strengthening welding layer is 1.5-5.5 mm.

7. The joint of a copper terminal and an aluminum wire according to claim 1, characterized in that, The material of the copper terminal is copper or copper alloy; Preferably, the shape of the connector of the copper terminal is flat, arc-shaped or a hollow column with openings at both ends, and the side surface of the hollow column is closed or not closed.

8. The joint of a copper terminal and an aluminum wire according to claim 1, characterized in that, The surface of the copper terminal also has a coating; Preferably, the thickness of the coating is 3 μm to 5000 μm; more preferably, the thickness of the coating is 5 μm to 1000 μm; Preferably, the coating is attached to the copper terminal by electroplating, electromagnetic welding, arc spraying or pressure welding; Preferably, the metal material of the coating is one or a combination of several metals such as chromium or chromium alloy, zinc or zinc alloy, tin or tin alloy, titanium or titanium alloy, zirconium or zirconium alloy, nickel or nickel alloy, silver or silver alloy, gold or gold alloy; more preferably, the metal material of the coating is one or a combination of several metals such as zinc or zinc alloy, tin or tin alloy, nickel or nickel alloy.

9. The joint of a copper terminal and an aluminum wire according to claim 1, characterized in that, The material of the conductor core of the aluminum wire is aluminum or aluminum alloy; preferably, the aluminum wire is a solid wire or a multi-core wire.

10. A plasma welding method for preparing the joint of a copper terminal and an aluminum wire according to any one of claims 1 - 9, characterized in that, The plasma welding method includes the following steps: 1) Assemble the conductor core of the aluminum wire and the connector of the copper terminal; 2) Adopt a crimping method to tightly press the conductor core of the aluminum wire and the connector of the copper terminal to form a crimping area; 3) Send the solder to the copper terminal; preferably, send the solder to the connector of the copper terminal; preferably, send the solder to the crimping area between the aluminum wire and the copper terminal, and then use plasma arc welding to weld, so that the solder melts and fills the connection gap between the copper terminal and the aluminum wire through capillary action to form a transition welding layer.

11. A plasma welding method for preparing the joint of a copper terminal and an aluminum wire according to any one of claims 1 - 9, characterized in that, The plasma welding method includes the following steps: 1) Wrap the solder around the aluminum wire core, or at least cover the part where the copper terminal connector is connected to the aluminum wire core, and then assemble the core of the aluminum wire with the copper terminal connector; 2) Use a crimping method to tightly press the core of the aluminum wire, the solder, and the connector of the copper terminal to form a crimping area; 3) Use plasma arc welding to melt the solder between the copper terminal and the aluminum wire, and fill the gap between the copper terminal and the aluminum wire through capillary action to form a transition welding layer.

12. The method according to claim 10 or 11, characterized in that, In step 3), use plasma arc welding to melt the solder to form a strengthening welding layer first, and then continue the welding process to fill the gap between the copper terminal and the aluminum wire with the solder to form a transition welding layer; Preferably, the thickness of the strengthening welding layer is 0 - 15 mm; more preferably, the thickness of the strengthening welding layer is 1.5 - 5.5 mm.

13. The method according to claim 10 or 11, characterized in that, In step 2), the area of the crimping area of the copper terminal and the aluminum wire joint accounts for at least 1% of the overlapping area of the aluminum wire and the copper terminal; preferably, the area of the crimping area of the copper terminal and the aluminum wire joint accounts for at least 10% of the overlapping area of the aluminum wire and the copper terminal; Preferably, in step 2), after the copper terminal and the aluminum wire joint are crimped, the compression rate of the aluminum wire core is between 70% - 90%; more preferably, the compression rate of the crimped aluminum wire core is between 75% - 85%; Preferably, in step 3), the ionization and shielding gas for the plasma welding is nitrogen, argon, helium, neon, krypton or xenon; more preferably, the ionization and shielding gas for the plasma welding is argon; Preferably, in step 3), the welding current for the plasma welding is between 5 A - 100 A; more preferably, the welding current for the plasma welding is between 20 A - 80 A; Preferably, in step 3), the flow rate of the ionization gas for the plasma welding is 1 - 5 liters per minute, and the flow rate of the shielding gas is 3 - 12 liters per minute; more preferably, the flow rate of the ionization gas is 2 - 3 liters per minute, and the flow rate of the shielding gas is 5 - 10 liters per minute; Preferably, in step 3), the angle between the plasma welding torch and the axis of the copper terminal is less than 45°; more preferably less than 20°; Preferably, in step 3), after the copper terminal and the aluminum wire joint are welded using plasma welding, the penetration depth of the solder accounts for 3% - 100% of the length of the copper terminal connector; more preferably, the penetration depth of the solder accounts for 30% - 100% of the length of the copper terminal connector; Preferably, in step 3), after the copper terminal and the aluminum wire joint are welded using plasma welding, the penetration depth of the solder accounts for 5% - 100% of the length of the entire crimping area; more preferably, the penetration depth of the solder accounts for 35% - 100% of the length of the entire crimping area; Preferably, in step 3), the metal material of the solder is a metal or alloy with a melting point not higher than that of aluminum; more preferably, the metal material of the solder contains zinc; more preferably, the zinc accounts for more than 30% of the total weight of the solder; more preferably, the zinc accounts for more than 60% of the total weight of the solder.