JPH10146679A - Electric resistance welding method for different kinds of materials - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength of a welding part (exfoliation resistance) by forming a lapped part at a part of a member of low electroconductivity, attaching with inserting a member of high electroconductivity in this lapped part, welding this part, generating high heat caused on the contact electric resistance between materials of two lapped parts, raising the concentration of the welding heat and welding at the time of welding the member of low electroconductivity to a seat material of high electroconductivity. SOLUTION: In the case of welding a spacer 30 of SUS 304 stainless steel onto four numbers of copper foil lead bundles 20 of a lithium ion secondary battery, a lateral U shaped lapped part 31 is preformed at a part of a spacer of low electroconductivity stainless steel, and one side end part 21 of the copper lead bundles 20 of high electroconductivity is inserted inside the lapped part 31. In this state, this part is clamped with a pair of electrodes 40, 41 of a capacitor type electroresistance welding machine. Therefore, a nugget is formed on the central part of lapped layers of the lapped part 31 of the lead part side one end part 21 and the spacer 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electric resistance welding of dissimilar materials for joining a sheet-shaped metal member having high electric conductivity and a metal member having lower electric conductivity than this metal member.

[0002]

2. Description of the Related Art In recent years, with the spread of portable electric devices such as portable telephones, portable video cameras, and notebook personal computers, needs for a large capacity and high energy density of a battery serving as a power supply have been rapidly increasing. Under such circumstances, a lithium secondary battery has attracted attention as a new secondary battery replacing lead and nickel cadmium. Since this has a weight energy density that is three to four times higher than that of a lead battery or a nickel cadmium battery of the same capacity, it is optimal for the above-described need for higher density.

This battery generally has a structure in which positive and negative electrodes are opposed to each other in a sealed metal case, and a current flows from a lead connected to the electrode through the battery case. Has been taken out. In addition, stainless steel is often used for the battery case because of its good corrosion resistance to chemicals such as an electrolytic solution and the need for strength. On the other hand, copper is often used for the negative electrode lead connected to the battery case because of the need for electric corrosion resistance and high conductivity. For this reason, it has been necessary to connect the leads made of different materials and the battery case by welding or the like.

As described above, the dissimilar materials of the sheet-like first metal member having high electric conductivity and the second metal member having lower electric conductivity than the first metal member are easily and firmly joined to each other. There was a need for a way to do that. On the other hand, as a method for welding two sheet-shaped metal members, two sheet-shaped metal members are overlapped, and a pair of electrodes are used to conduct electricity while being pressed in a direction approaching each other. There is an electric resistance welding method for welding these metal members. In this method, a high-temperature heat is generated by contact resistance between metal members by energization, and the high heat melts and welds the metal members at an electric welding contact point. The electric resistance welding machine having a pair of welding electrodes Etc., and two types of plate-shaped metal members can be easily and firmly joined.

However, when one of the metal members has high thermal conductivity, the heat generated by the contact resistance between the metal members is dissipated through the high thermal conductivity metal member in the conventional electric resistance welding method. In addition, there has been a problem that welding becomes unstable due to poor concentration of welding heat and the like, and the welding comes off after welding. In particular, in welding the above-described lead made of copper and the battery case made of stainless steel, the heat conductivity of copper is remarkable because the heat conductivity is very good, and the welding is removed during use of the battery and current cannot be taken out. There is a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a first metal member in the form of a sheet having high electric conductivity and a lower electric conductivity than the first metal member. It is an object of the present invention to provide a method for electric resistance welding of dissimilar materials capable of easily and firmly joining dissimilar materials of a second metal member.

[0007]

Means for Solving the Problems The present inventor has provided a second metal member with a folded portion partially folded,
One side end of the first metal member is inserted into the folded portion,
Subsequently, the first metal member and the second metal member are connected to each other by sandwiching the folded portion in which one side end of the first metal member is inserted between the pair of electric welding contacts and supplying current. The inventors have found that welding can be performed easily and firmly, and have arrived at the present invention.

That is, according to the method of the present invention, a sheet-shaped first metal member having high electric conductivity and a second metal member having lower electric conductivity than the first metal member are provided. A method of electrical resistance welding of dissimilar materials, wherein the second metal member has a folded portion in which a part of the second metal member is folded, and one side end of the first metal member is joined to the folded portion. And a pair of electric welding contacts sandwiches the folded portion in which one side end of the first metal member is inserted, and energizes the first metal member and the second metal member. It is characterized by joining with a metal member.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method for electric resistance welding of dissimilar materials according to the present invention, one side end of a first metal member is inserted into a folded portion of a second metal member to form a pair of first metal members. It is welded by being sandwiched between electric welding contacts and energized. The embodiment is as follows. First, the first metal member is a sheet-shaped metal member having high electrical conductivity, but the material is not particularly limited,
In general, a metal member made of a single metal such as iron, copper, or aluminum, or an alloy or the like, which is generally referred to as having high electric conductivity and widely used industrially, can be used.

[0010] The structure of the first metal member is not particularly limited, and a structure in which a plurality of foil-shaped metal members are laminated can be used. Further, the first metal member may have a film having a lower electric conductivity than the metal member on the surface. Next, the second metal member is connected to the first metal member.
Metal member having lower electrical conductivity than the metal member of
The kind of the metal member is limited depending on the material of the metal member. However, the combination of the first metal member and the second metal member is not particularly limited. If the second metal member is a metal member having lower electric conductivity than the first metal member, the first metal member may be the first metal member. The combination can be arbitrarily selected irrespective of the thermal conductivity of the metal member. For example, the first metal member may be made of copper or a copper alloy, and the second metal member may be made of stainless steel.

The second metal member is partially folded and has a folded portion, but the shape of the folded portion is not particularly limited. It can be selected according to the shape of the side end.
At this time, if one end of the first metal member has a rectangular cross section, the folded portion desirably has a U-shaped cross section. Thus, one end of the first metal member is inserted into the folded portion of the second metal member without any gap.

The width and length of the folded portion are not particularly limited, and the size and the size of the first metal member are not limited.
It can be selected according to the size of the welded portion, the number of welded portions, and the like. Further, it is desirable that the second metal member is made of an elastic member, and that the folded portion sandwiches one side end of the inserted first metal member by a spring action. Thereby, one side end of the first metal member is firmly held between the folded portions of the second metal member, and can be fixed so as not to be displaced from each other. In particular, when the first metal member is formed by laminating a plurality of foil-shaped metal materials, a spring action works in a direction approaching each other, so that not only fixing but also pressing is performed at the same time as being pinched by a pinch.

Next, an electric resistance welding machine or the like having a pair of welding electrodes can be used as the current supply means. At this time, a capacitor-type resistance welding machine or the like can be used as the resistance welding machine. Also, the shape and size of the welding electrode are not particularly limited, and can be selected according to the welding space, the size of the welded portion, and the like. The same welding electrode may be used for each of the pair of welding electrodes, or different welding electrodes may be used.

[0014]

According to the electric resistance welding method for dissimilar materials of the present invention, the electric resistance of the second metal member and the contact at the two contact portions of the folded portion of the first metal member and the second metal member by the energization. High-temperature heat is generated by the resistance. Due to the high heat generated from these two locations, the concentration of welding heat is improved, and the first metal member and the second metal member are fused and welded to each other at the electric welding contacts very effectively. For this reason, since the first metal member and the second metal member are welded at two locations, the joining becomes strong.

In particular, since the first metal member is welded in a state where one end portion of the first metal member is inserted into the folded portion of the second metal member, the first metal member and the second metal member are connected to each other. Strongly joined. Further, in the electric resistance welding method for dissimilar materials according to the present invention, even when a film having a large electric resistance is interposed between the first metal member and the second metal member, the current between the electrodes is changed to the first electric current by the contact resistance. Flows through the second metal member, bypassing the metal member, and high-temperature heat is generated by the electric resistance of the current flowing through the second metal member. Due to the high heat, the first metal member and the second metal member are melted and welded to each other at the electric welding contacts.

Further, the first metal member is formed by laminating a plurality of foil-shaped metal members, and the second metal member is formed of an elastic member, and the folded portion is formed by inserting the first metal member.
When one end of the metal member is held by a spring action, not only fixing but also pressurizing is performed at the same time. Therefore, when electricity is supplied, the size of pressing by the electrode can be reduced, and welding can be performed more easily.

The welding of the combination in which the first metal member is made of copper or a copper alloy and the second metal member is made of stainless steel is the same as the welding of the combination of the lead and the battery case in forming the battery described above. The present welding method can be used for connecting such battery components. In connection between the lead and the battery case,
Using a metal member such as a spacer with lower electrical conductivity than the lead, welding the lead and this spacer first, then welding the spacer and the battery case, connecting the lead and the battery case via the spacer Is also good.

[0018]

The present invention will be described below in detail with reference to examples. (Example 1) In this example, the present invention was implemented to connect a negative electrode lead and a battery case in manufacturing the cylindrical lithium ion secondary battery shown in FIG.

This cylindrical lithium ion secondary battery 1 has
A sheet-shaped positive electrode 2 and a negative electrode 3 are wound in a cylindrical shape with a separator 4 interposed therebetween, and a cylindrical battery case 5 is formed.
It is formed by being housed in a box. The positive electrode 2 is formed by applying or depositing a positive electrode active material such as lithium manganese oxide on both surfaces of a current collector made of aluminum foil, and the negative electrode 3 is formed on both surfaces of a current collector made of copper foil. It is made by pressing metallic lithium or its alloy. Battery case 5 is made of stainless steel (SUS304). The separator 4 is made of polyethylene or propylene. The negative electrode 3 is connected to a negative electrode lead 6 for extracting a current, and the negative electrode lead 6 is connected to the bottom of the battery case 5. The positive electrode 2 is also connected to a positive electrode lead 7 for extracting current, and the positive electrode lead 7 is connected to a current collector on the upper surface of the battery.

To form the cylindrical lithium ion secondary battery 1, first, a sheet-shaped negative electrode 3 having a negative electrode lead 6 having a predetermined size and a thickness of 20 μm as shown in FIG. One positive electrode 2 of each size was prepared, and each was alternately wound with a separator interposed therebetween to form a cylindrical laminate 10 shown in FIG. The four negative electrode leads 5 connected to the negative electrode 3 are bundled together to form a lead bundle 20, and one end 21 of the lead bundle 20 has a laminated structure of the negative electrode leads 5.

Subsequently, a 50 μm-thick stainless steel (SUS304) having a U-shaped folded portion 31 is provided.
m, and one end 21 of the lead bundle 20 is inserted into the folded portion 31 of the spacer 30, and is sandwiched between a pair of electric welding contacts using a capacitor-type resistance welding machine to energize. Then, the lead bundle 20 and the spacer 30 were welded. FIG. 4 shows that one end 21 of the lead bundle 20 is the spacer 3.
0 shows a state of being inserted into the folded portion 31 of the
A state where one end 21 of the lead bundle 20 and the folded portion 31 of the spacer 30 are sandwiched by the welding electrodes 40 and 41 between the pair of electric welding contacts 40a and 41a and welded is shown.

A welding electrode 40 of a condenser type resistance welding machine;
41 are both made of chromium copper, and the size thereof is such that the welding electrode 40 has a diameter of 3 mm, a tip angle of 30 °, and a tip diameter of 1 mm, and the opposing welding electrode 41 has a diameter of 5.5 mm, a tip angle of 45 °, and a tip diameter of 3. 5 mm. At this time, energization was performed at an energization output of 20 W · S. Subsequently, as shown in FIG. 5, the laminate 10 is inserted into the battery case 5, and the bottom portion 51 of the battery case 5 having a thickness of 0.3 mm and the spacer 30 are overlapped. Was used to weld the bottom portion 51 of the battery case 5 and the spacer 30 with the welding electrodes 42 and 43. FIG. 6 is an enlarged cross-sectional view showing a state in which the bottom of the battery case 5 and the spacer 30 are overlapped with each other.
3 shows a state of being sandwiched and welded by a pair of electric welding contacts 42a and 43a. At this time, the bottom portion 51 of the battery case 5 and the spacer 30 were pressurized from both sides by the welding electrodes 42 and 43, and were subjected to resistance welding by energizing in a completely fixed state. In addition, the welding electrodes 42 and 4 of the condenser type resistance welding machine are used.
As No. 3, the same electrode as the welding electrode 40 was used as the welding electrode 42, and a chrome copper welding electrode having a diameter of 10 mm was used as the welding electrode 43. At this time, the energization output is set to 17 W · S
As energized. (Comparative Example 1) As shown in FIG. 7, one end 21 of the lead bundle 20 and the bottom 51 of the battery case 5 are directly overlapped without using the spacer 30, and a pair of electric The one end 21 of the lead bundle 20 and the battery case 5 were welded in the same manner as in Example 1 except that the welding was performed while being sandwiched between the resistance welding points 42b and 43b. At this time, energization was performed with an energization output of 30 to 40 W · S. (Quality Evaluation) First, the welded state of Example 1 and Comparative Example 1 was observed using a microscope. In the observation of this welding state, dents, spread, and cracks generated on the surface of the welded portion were evaluated by surface observation. Also,
The welded part is cut in cross-section, and by observing the cross-section, it evaluates the scatter inside the weld, blowholes, cracks, and lifting of the plate, and is the most important nugget in controlling the welding strength in quality evaluation. Was evaluated.

With respect to the welded portion of Example 1, it was found from the result of surface observation that dents, spreads, and cracks were scarcely observed on the surface of the welded portion. It was found that blow holes, cracks, and lifting of the board were hardly observed. Further, with respect to the nugget, a micrograph of the cross section thereof is shown in FIG.
As shown in FIG. 9, a nugget 50 is formed at one end 21 of the lead bundle 20 and at the center of the lamination of the folded portion 31 of the spacer 30, and the spacer 30 is wrapped around the nugget 50. It can be seen that the stainless steel component is dissolved. From the observation result of the nugget 50, it can be seen that the laminated portion of the one end 21 of the lead bundle 20 is sufficiently melted. From the surface observation and the cross-sectional observation of these welded parts, it was found that the welded state of the welded part of Example 1 was excellent.

On the other hand, with respect to the welded portion of Comparative Example 1, it was found from the surface observation that the surface of the welded portion was often dented, spread, and scattered.
It was found that many blow holes and board lifts were observed. Although not shown, the nugget was small in diameter and varied in size, and it was found that the welding strength was not sufficient.
From the surface observation and the cross-sectional observation of these welded parts, it was found that the welded state of the welded part of Comparative Example 1 was not excellent.

Next, a welding strength test was performed on the welded portions of Example 1 and Comparative Example 1. In this test, in order to examine the welding strength of the laminated portion of the one end 21 of the lead bundle 20 and the folded portion 31 of the spacer 30, five samples were prepared, and the peeling strength of these five samples was measured by a peeling method. Was measured. Table 1 shows the measurement results for the welded portion of Example 1. Table 1 also shows the presence / absence of a nugget residue and the state of sputtering.

[0026]

[Table 1] As shown in Table 1, the peel strength was 0.72 to 0.85.
It was found to be kgf. Since the peel strength of the welded portion between the spacers 30 was 0.77 to 0.88 kgf, it was found that the weld strength was high. On the other hand, when the peel strength of the welded portion of Comparative Example 1 was measured, it was not displayed, but was found to be 0.07 to 1.77 kgf, indicating that the weld strength was unstable. It was also found that the presence or absence of a nugget residue and the state of sputtering were good.

From the above observation of the welding state and the welding strength test, it was found that the welding of Example 1 was excellent in welding quality.

[0028]

According to the electric resistance welding method for dissimilar materials of the present invention, a sheet-shaped first metal member having high electric conductivity and a second metal member having lower electric conductivity than the first metal member are formed. Since it is possible to easily and firmly perform welding, it is possible to manufacture a strong welded product and to reduce the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a perspective sectional view showing the structure of a cylindrical lithium ion secondary battery used in the present embodiment.

FIG. 2 is a front view of a sheet-shaped negative electrode used in Example 1.

FIG. 3 is an overall perspective view of a laminate used in Example 1. FIG.

FIG. 4 is an enlarged view of a main part of the first embodiment, showing a main part in which one end of a lead bundle is inserted into a folded portion of a spacer; It is a figure which shows a mode that the folded part of a spacer is welded.

FIG. 5 is a partial cross-sectional view showing a state where the bottom of the battery case and the spacer are overlapped in Example 1, and shows a state where the bottom of the battery case and the spacer are welded. FIG.

FIG. 6 is an enlarged sectional view of a main part showing a state where the bottom of the battery case and the spacer are overlapped in Example 1, and showing a state where the bottom of the battery case and the spacer are welded. It is.

FIG. 7 is an enlarged cross-sectional view of a main part showing a state where one end of a lead bundle and a bottom of a battery case are overlapped in Comparative Example 1; It is a figure which shows a mode that the bottom part of a case is welded.

FIG. 8 is a photomicrograph showing a cross section of a welded portion between the bottom of the battery case and the spacer in Example 1.

FIG. 9 is a schematic diagram illustrating the micrograph of FIG. 8;

[Procedure amendment]

[Submission date] January 20, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 8

[Correction method] Change

[Correction contents]

FIG. 8

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B23K 103: 22

Claims (6)

[Claims] 1. A sheet-shaped first metal member having high electric conductivity and a second metal member having lower electric conductivity than the first metal member.
An electric resistance welding method of dissimilar materials for welding the first metal member to the first metal member, wherein the second metal member has a folded portion in which a part thereof is folded. The first metal member is inserted into the folded portion, one end of the first metal member is sandwiched by the pair of electric welding contacts, and current is applied to the folded portion.
An electric resistance welding method for dissimilar materials, comprising welding the first metal member and the second metal member. 2. The method according to claim 1, wherein the first metal member is formed by laminating a plurality of foil-shaped metal materials. 3. The method for joining dissimilar materials according to claim 1, wherein the first metal member has a film having a lower electric conductivity on the surface than the metal member. 4. The method according to claim 1, wherein the second metal member has a U-shaped cross section. 5. The second metal member comprises an elastic member,
The joining method for dissimilar materials according to claim 1, wherein the folded portion holds one end of the inserted first metal member by a spring action. 6. The method according to claim 1, wherein said first metal member is made of copper or a copper alloy, and said second metal member is made of stainless steel.