JP2011067830A - Method of joining copper sheet and steel sheet by laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a stable lap joining in the joining of a copper sheet and a steel sheet by laser. <P>SOLUTION: In the lap joining of two metal sheets composed of an upper sheet of the cooper sheet Cu and a lower sheet of a steel sheet SUS, an introducing hole Wp for receiving a laser beam Lb is previously provided on the side of the copper sheet Cu. The laser beam Lb to be emitted is a semiconductor laser, and its wavelength is ≤1 μm. The laser beam is emitted from the side of the copper sheet Cu and onto the steel sheet SUS through the introducing hole Wp. When the laser beam is emitted, the steel sheet SUS is heated principally independently, and the copper sheet Cu is heated by heat conduction since the two sheets are stacked closely. Simultaneously, in the outer peripheral foot part of the energy distribution of the laser beam Lb, the laser beam is absorbed on the wall face and the outer peripheral surface of the introducing hole Wp of the copper sheet and the copper sheet is heated and its temperature is raised. Because a wire Wire which turns into a brazing filer metal is supplied in the heated state of both these sheets and molten by the laser beam Lb, fusion joining of high strength is completed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser welding method for efficiently manufacturing an electric system such as a hybrid car and an electric vehicle.

FIG. 3 shows an electric resistance welding method which is the conventional joining technique 1. Electric resistance welding method of the conventional joining technique 1 This is a method in which a positive electrode Pv + and a negative electrode Pv- are attached to both sides of a copper plate and a steel plate, and a current is passed. . In the welding of the copper plate Cu and the steel plate SUS, the steel plate has a low electrical conductivity of about 1/6 compared to the copper plate. In terms of electrical resistivity, the steel sheet is about 6 times, so the Joule heat, which is the calorific value, becomes 36 times, and in the state where the copper plate is slightly heated, the current-carrying part Hz melts in the steel plate. In this manner, the electric resistance welding method melts the steel plate without melting the copper plate, and the copper plate and the steel plate cannot be joined. Thus, it is impossible to join the copper plate and the steel plate by the electric resistance welding method of the conventional joining technique 1.
FIG. 4 shows a laser welding method using CO2 laser, YAG laser and semiconductor laser, which is the conventional joining technique 2.
The reflectivity exceeds 95 percent at the wavelength of the CO2 laser, YAG laser and semiconductor laser on the surface of the copper plate.
A laser beam LBin is applied to the copper plate from the laser processing head LBph. The copper plate has a high reflectivity with respect to the laser beam, and the laser beam contributing to the heating of the copper plate reflected by many laser beams LBout is 5% or less of the whole.
As described above, it is difficult for the laser welding method of the conventional joining description 2 to join the intended copper plate and steel plate.

(1) Low productivity by mechanical fixing method (2) High reflectivity of copper plate surface (3) Ensuring mechanical strength against vibration, tension and bending,
(4) Ensuring a large current value corresponding to acceleration and high-speed charging.

The problem is
(1) Low productivity by mechanical fixing method Lap joining of a copper plate and a steel plate is currently difficult. As a result, the copper plate and the steel plate are provided with overlapping through holes, and the caulmel or bolting is performed. However, this method requires processing from both sides of the copper plate and the steel plate, and the shape of the workpiece is limited. Such a mechanical method takes time, and it is difficult to stabilize the electrical resistivity at the joint for achieving the original electrical joining. The laser welding method of the present application is a method for solving these problems, and provides a laser welding method that can be processed from one side on the copper plate side and becomes a metal joint so that a low electrical resistivity can be secured stably. It is.

(2) High reflectivity on the copper plate surface In the lap joint of copper plate and steel plate, the reflectivity of the laser beam is as high as 95% or more on the copper plate surface, so most of the laser beam is reflected and contributes to heating and melting of the copper plate. There is no.
In the laser welding method of the present application, an introduction hole for receiving a laser beam is provided in advance on the copper plate side. Even if this hole reaches the steel plate side, there is no problem. The steel plate is heated through the introduction hole, and the copper plate is heated by the conduction of the heat.
While the laser beam is irradiated, the wall surface of the introduction hole of the copper plate is heated by the absorption of the laser beam by the copper plate simultaneously with the heating and melting of the steel plate and the heating of the copper plate by heat propagation. A brazing wire is supplied to the heated state of both plates and melted with a laser beam, so that brazing with excellent wettability is completed. The laser welding method of the present application is a method for solving these problems, and provides a laser welding method that can be processed from one side on the copper plate side and becomes a metal joint, so that a low electrical resistivity can be secured stably.

(3) Ensuring mechanical strength against vibration, tension and bending,
It is possible to secure mechanical strength against vibration, tension, and bending by the number and arrangement of the joining points joined by the laser welding method of the present application.
The laser welding method of the present application provides a joining method having high mechanical strength against vibration, tension, and bending.

(4) Ensuring a large current value corresponding to acceleration and high-speed charging.
The total area of the joints can be increased by increasing the number of joints joined by the laser welding method of the present application, and a large current value corresponding to acceleration and high-speed charging can be secured. The laser welding method of the present application secures a low electrical resistivity and provides a joint corresponding to a large current value corresponding to acceleration and high-speed charging.

(1) Provide laser welding technology that achieves high productivity.
This is a laser welding technique that greatly improves the low productivity of the prior art in the mechanical fixing method. The lap joint of a copper plate and a steel plate is a difficult state at present. As a result, the copper plate and the steel plate are provided with overlapping through holes, and the caulmel or bolting is performed. However, this method requires processing from both sides of the copper plate and the steel plate, and the shape of the workpiece is limited. Such a mechanical method takes time, and it is difficult to stabilize the electrical resistivity at the joint for achieving the original electrical joining.
The laser welding method of the present application is a method for solving these problems, and provides a laser welding method that can be processed from one side on the copper plate side and becomes a metal joint so that a low electrical resistivity can be secured stably. It is.

(2) Propose a laser welding technique that achieves the welding of copper plate and steel plate with high reflectivity.
In the lap joint between a copper plate and a steel plate, the reflectivity of the laser beam is as high as 95% or more on the surface of the copper plate, so most of the laser beam is reflected and does not contribute to heating or melting of the copper plate. In the laser welding method of the present application, an introduction hole for receiving a laser beam is provided in advance on the copper plate side of the upper plate. Even if this hole reaches the steel plate side of the lower plate, there is no problem. A laser beam is irradiated from the copper plate side, and the steel plate is irradiated through the introduction hole. When the laser beam is irradiated, the steel plate is mainly heated. At the same time, since the two materials are in close contact with each other, the copper plate is heated by the heat conduction. While the laser beam is being radiated, simultaneously with the heating of the copper plate by heat propagation, the outer periphery of the energy distribution of the laser beam effectively absorbs the laser beam at the introduction hole wall surface and outer peripheral surface of the copper plate and heats it. Increase the temperature. Since the wire used as the brazing material is supplied to the heated state of both plates and melted by the laser beam, a high-strength melt joint with brazing having excellent wettability is completed. The laser welding method of the present application is a method for solving these problems, and provides a laser welding method that can be processed from one side on the copper plate side and becomes a metal joint, so that a low electrical resistivity can be secured stably.

(3) Propose a laser welding technology that can ensure mechanical strength against vibration, tension, and bending.
It is possible to secure mechanical strength against vibration, tension, and bending by the number and arrangement of the joining points joined by the laser welding method of the present application. The laser welding method of the present application provides a joining method having high mechanical strength against vibration, tension, and bending.

(4) Propose a laser welding technique that ensures a large current value for acceleration and high-speed charging.
The total area of the joints can be increased by increasing the number of joints joined by the laser welding method of the present application, and a large current value corresponding to acceleration and high-speed charging can be secured. The laser welding method of the present application secures a low electrical resistivity and provides a joint corresponding to a large current value corresponding to acceleration and high-speed charging. In this manner, the laser welding technique of the present application is a laser welding technique that enables joining of a copper plate and a steel plate. That is, it is possible to achieve a lap joint between a copper plate and a steel plate, which are extremely accurate and stable, with high strength, and can efficiently manufacture a motive electric system of a hybrid car and an electric vehicle.

Explanatory drawing which shows the relationship of the lap joint of the copper plate and steel plate by the laser which comprises this patent Explanatory drawing which shows the situation of the example by this patent, and the section of a joined part Explanatory drawing which shows the relationship between the state of the lap joint of the copper plate and steel plate by the resistance heating of the conventional welding method 1, and the cross section of a junction part Explanatory drawing which shows the relationship between the concept of the lap joint of the copper plate and steel plate by the laser of the conventional welding method 2, and the cross section of a junction part Explanatory drawing showing the relationship of the state where the laser beam introduction hole was made in the copper plate Explanatory drawing showing the relationship of the state in which a laser beam introduction hole is made in a copper plate and this introduction hole reaches the steel plate Explanatory drawing which shows the relationship which the inner surface part of an introduction hole heats by irradiation to the introduction hole of a laser beam Explanatory drawing which shows the relationship which irradiates a laser beam to an introduction hole, supplies the wire of a brazing material simultaneously with laser beam irradiation after heating an introduction hole, and performs joining Explanatory drawing which shows the sample for a test which performs the tensile strength test of a joining member with a copper plate and a steel plate by the manufacturing method of this patent Explanatory drawing which shows the tensile strength test result of the member which joined the copper plate and steel plate by this patent Explanatory drawing which shows the increase method of the intensity | strength of a joining member and energization capability by this patent

  FIG. 1 shows the relationship of lap joining of a copper plate Cu and a steel plate SUS by a laser processing head LBph constituting the present patent and a wire supply head Wire for supplying a brazing material. And the joining point Wp after the joining of 3 places is shown.

  In the section of the conventional technology, it was explained that it is difficult to lap-join a copper plate and a steel plate with a conventional joining technique. At present, joining is difficult, so a copper plate and a steel plate are provided with through-holes, and caulmel or bolting is performed.

  However, this mechanical fixing method requires processing from both sides of the copper plate and the steel plate, and the shape of the workpiece is limited and the productivity is low. The laser welding method of the present application is a method for solving these problems, and provides a laser welding method that can be processed from one side of the copper plate side and becomes a metal joint so that a low electrical resistivity can be secured stably. It is.

FIG. 2 shows the state of the joint after joining the copper plate and the steel plate by the laser welding method of this patent.
In the method of superimposing and joining two metal plates, a copper plate and a steel plate, a wire for brazing simultaneously with laser irradiation through a laser beam introduction hole Hole provided in the copper plate Cu from the copper plate side using the semiconductor laser Lb Supply wire and perform bonding. The junction point Wp which is the state of the completed joining is shown.
(FIGS. 1 to 11 will be described.)

  In the lap joint between a copper plate and a steel plate, the reflectivity of the laser beam is as high as 95% or more on the surface of the copper plate, so most of the laser beam is reflected and does not contribute to heating or melting of the copper plate.

  As shown in FIG. 1 of the present application, an introduction hole for receiving a laser beam is provided in advance on the copper plate side. 5 and 6 show the relationship between the copper plate Cu, the steel plate SUS, and the laser beam introduction hole. As shown in FIG. 6, there is no problem in joining even if the laser beam introduction hole Hole reaches the steel plate side. After processing the introduction hole, the introduction hole is irradiated with the laser beam Lb. Thus, the laser beam Lb heats the steel plate SUS through the introduction hole Hole. The copper plate Cu is heated by the heat conduction, and the inside Hw of the introduction hole Hole is heated. While the introduction hole Hole is irradiated with the laser beam Lb, as shown in FIG. 7, the introduction hole of the copper plate by the absorption of the laser beam in the copper plate simultaneously with the heating and melting of the steel plate SUS and the heating of the copper plate Cu by heat propagation Heat the walls.

  Here, the laser beam to be irradiated is a semiconductor laser, and the wavelength thereof is 1 micron or less. In the case of a semiconductor laser with a wavelength of 808 nm, the absorption rate of the laser beam on the surface of the copper plate is two to three times that of the YAG laser, and the copper plate wall is slightly inside the introduction hole, but there is also direct copper plate heating. While the laser beam is irradiated in this manner, the wall surface of the introduction hole of the copper plate is heated by the absorption of the laser beam by the copper plate simultaneously with the heating and melting of the steel plate and the heating of the copper plate by heat propagation.

  As shown in FIG. 8, a wire that becomes a brazing material is supplied to the heated state of both plates and melted by a laser beam, so that the inner wall of the introduction hole is already in a heated state, so that the molten brazing material is melted to the inner wall. The arrival starts. This situation is an excellent state of wettability which is important in the brazing method.

As shown in FIG. 9, two joining points Wp are formed and the joining of the copper plate and the steel plate by brazing is completed. Using this joined sample, a strength test of the joining point Wp was performed. In the lap joint of a copper plate and a steel plate, an introduction hole for receiving a laser beam is provided in advance on the copper plate side. Even if this hole reaches the steel plate side, there is no problem. The laser beam to be irradiated is a semiconductor laser, and the wavelength thereof is 1 micron or less. In the case of a semiconductor laser with a wavelength of 808 nm, the absorption rate of the laser beam on the copper plate is 2 to 3 times that of the YAG laser, which is slight, but there is also direct heating of the copper plate. A laser beam is irradiated from the copper plate side, and the steel plate is irradiated through the introduction hole. When the laser beam is irradiated, the steel plate is mainly heated, and at the same time, since the two materials are closely adhered and stacked, the copper plate is heated by the heat conduction. While the laser beam is being radiated, simultaneously with the heating of the copper plate by heat propagation, the outer periphery of the energy distribution of the laser beam effectively absorbs the laser beam at the introduction hole wall surface and outer peripheral surface of the copper plate and heats it. Increase the temperature. Since the wire used as the brazing material is supplied to the heated state of both plates and melted by the laser beam, a high-strength melt joint with brazing having excellent wettability is completed. FIG. 9 A test sample in which a copper plate and a steel plate were joined was used as a sample for a tensile strength test. Tensile strength of 200N / mm ² of copper which is a material, the tensile strength of the copper plate is of 450N / mm ^2. FIG. 10 shows the test results as a result of pulling the bonded test pieces. Junction Wp is two points, the strength at break of the first point after start of the test is 642N / mm ^2, the strength at break of the second point of junction 420N / mm ^2. The diameter of the joining point is 1 mm or less. Even when the larger the area and 1 mm ^2, the tensile strength of the junction can be said to be 450 N / mm ² or more. FIG. 11 shows how the number of junction points is increased to ensure the mechanical strength against vibration, tension, and bending, and to secure a large current value corresponding to acceleration and high-speed charging. Regarding the securing of mechanical strength against vibration, tension, and bending, as shown in FIG. 11, the number of joints joined by the laser welding method of the present application and the arrangement of the mechanical strength against vibration, tension, and bending are as follows. It can be secured. The laser welding method of the present application provides a joining method having high mechanical strength against vibration, tension, and bending. For securing a large current value for acceleration and high-speed charging, as shown in Fig. 11, the total area of the joint points can be expanded by increasing the number of joint points joined by the laser welding method of this application. It is possible to secure a large current value corresponding to acceleration and high-speed charging. The laser welding method of the present application ensures a low electrical resistivity and provides a joint corresponding to a large current value corresponding to acceleration and high-speed charging.

FIG. 1 is a typical block diagram of the present invention. The relationship between the lap joint of the copper plate Cu and the steel plate SUS by the laser processing head LBph constituting this patent and the wire supply head Wire for supplying the brazing material is shown. And the joining point Wp after the joining of 3 places is shown.

In the lap joint of a copper plate and a steel plate, an introduction hole for receiving a laser beam is provided in advance on the copper plate side. Even if this hole reaches the steel plate side, there is no problem. The laser beam to be irradiated is a semiconductor laser, and the wavelength thereof is 1 micron or less.
In the case of a semiconductor laser with a wavelength of 808 nm, the absorption rate of the laser beam on the copper plate is 2 to 3 times that of the YAG laser, which is slight, but there is also direct heating of the copper plate. The steel plate is heated through the introduction hole, and the copper plate is heated by the conduction of the heat.
While the laser beam is irradiated, the wall surface of the introduction hole of the copper plate is heated by the absorption of the laser beam by the copper plate simultaneously with the heating and melting of the steel plate and the heating of the copper plate by heat propagation. Since the wire used as the brazing material is supplied to the heated state of both plates and melted by the laser beam, a high-strength melt joint with brazing having excellent wettability is completed. The copper component of the wire is 90% or more. The laser output is 1 kW and the irradiation time is 2 seconds. In this way, it is possible to achieve a lap joint between a copper plate and a steel plate, which are extremely accurate and stable, with high strength, and can efficiently manufacture a motive electric system of a hybrid car and an electric vehicle.

Cu: Copper plate, SUS: Steel plate, Hole: Introduction hole, B-Hole: Bottom of introduction hole, Lb: Laser beam,
Wire: Brazing wire, Bond: Bonding part, Pv +: Positive electrode, Pv-: Negative electrode, Hz: Heating zone,
LBph: laser processing head, LBin: incident laser beam, LBout: reflected laser beam,
Hw: Internal heating area of introduction hole, Wp: Junction point

Claims (3)

(Semiconductor) laser welding characterized in that a laser beam is irradiated from a copper plate side through a laser beam introduction hole provided in the copper plate using a semiconductor laser in a method of superimposing and joining two metal plates, a copper plate and a steel plate. Method. In the method of joining two metal plates, a copper plate and a steel plate, by superposing and joining a laser beam from a copper plate side through a laser beam introduction hole provided in the copper plate using a semiconductor laser and simultaneously supplying a brazing wire A laser welding method characterized by joining. In the method of overlapping and joining two metal plates, a copper plate and a steel plate, a plurality of laser beam introduction holes are provided to secure the necessary strength value and necessary current value from the copper plate side to the copper plate using a semiconductor laser. A laser welding method characterized in that a laser beam is irradiated through an introduction hole and at the same time a wire for brazing is supplied and joined.