The present invention relates to a resistance spot welding techniques, in particular, it relates to resistance spot welding apparatus for performing welding the plate pairs including a plurality of metal plates stacked. Further, the present invention relates to a composite electrode and the resistance spot welding method is utilized in the resistance spot welding.
BACKGROUND
[0002]
　Transportation machinery including automobiles, industrial machinery, etc., composed of a plurality of structural components. Often, the production of structural parts, resistance spot welding (hereinafter, simply referred to as "spot welding") is used.
[0003]
　In general, spot welding is performed as follows. Prepare a plate assembly as a material. Plate assembly has a portion in which a plurality of metal plates are stacked. Next, sandwiching the plate pairs by a pair of electrodes, pressed against each electrode plate assembly. Then, while pressing the plate pairs by the pressing of the electrodes, applying a current between the electrodes. Thus, in the plate group, with the pressure applied by the electrodes, contacts the metal plates adjacent to each other, current flows in the contact region and the region of the vicinity. These regions melted by Joule heat due to electrical resistance, which nugget is formed by coagulation. The formation of nuggets, are stitched together plates of sets of metal plates to each other are joined, the structural component is produced.
[0004]
　As the electrode, a flat type electrode chip, DR (double radius) type electrode chip, SR (Single ares) type electrode chip or the like is used. Flat electrode tip is a cylindrical, having a flat tip surface. DR-type electrode tip is a generally cylindrical tip portion has a projecting shape, the distal end surface is formed to the curvature radius of the larger convex surface. SR-type electrode tip is generally semi-cylindrical, having a distal end surface of the radius of curvature larger convex surface.
[0005]
　Recently, a promoted lightweight structural parts, as metal plate constituting the plate pair, high tensile steel, are often so-called high-tensile steel is employed. High-tensile steel, especially tensile strength 590 ~ 780 MPa class or higher tensile steel (hereinafter also referred to as "super-high-tensile steel") is difficult to plastic deformation, a high electrical resistance.
[0006]
　Due to such materials in nature, in the spot welding of ultrahigh-tensile material, the proper range of welding current value applied to the electrodes (hereinafter also referred to as "proper current range") tends to be narrowed. Proper current range from the minimum current value reference nugget diameter is set by the design specifications is obtained refers to the current value range up current value which dust is not generated. By the proper current range is wide, it is advantageous to ensure stable operation and the nugget diameter of the spot welding.
[0007]
　Also, in the ultra-high-tensile steel, difficult to improve the strength of the joint by spot welding. For example, the tensile strength of the base material (high-tensile steel) exceeds 590 ~ 780 MPa, which is one direction of peeling of the tensile strength of the welded joint strength, so-called cross tensile strength (Cross-Tension Strength: CTS) is improved It tends to decrease rather without.
[0008]
　Therefore, in the spot welding of ultrahigh-tensile material, the proper current range is narrowed, and CTS is that it is a problem to decrease, with the expansion of the proper current range, improvement in welded joint strength is required.
[0009]
　The measure to expand the proper current range, and increasing the pressure in pressing the electrode plate assembly, it is conceivable to or under an electricity application at multiple stages in applying a current between the electrodes. However, increasing the applied pressure, there is a limit on the stiffness of the device. Also, when the multi-step current, welding time is increased, productivity is lowered. Therefore, these measures are all poor in practicality.
[0010]
　On the other hand, the measure to improve the welded joint strength, or under an electricity application after added after the formation of the nugget, is possible or expand its nugget diameter conceivable. Rear energized, the formed nugget by temper softening, improving the toughness. This improvement in welded joint strength is achieved by. However, when the rear energization, resulting in welding time is increased, productivity is lowered. Therefore, post-energization poor practicality.
[0011]
　Also, expansion of the nugget diameter, effectively contributes to the improvement of the weld joint strength. Depending on the expansion of the nugget diameter, welded joint strength is improved. The measure to expand the nugget diameter, and go the energization to the electrodes in multiple stages, it is conceivable to or expand the diameter of the electrode tip surface. However, multi-stage current is a process to gradually proceed the growth of the nugget, the welding time is increased, productivity is lowered. Accordingly, multi-step energization poor practicality.
[0012]
　Expansion of the electrode tip diameter, have the following problems. For example, when employing a flat electrode tip as an electrode, it is necessary to uniformly contact the flat tip surface that is enlarged in a plate pair. Therefore, the flatness of the electrode distal end surface, is required a very high dimensional accuracy. On the other hand, when employing the DR type electrode tip as an electrode, pushing a large front end surface of the enlarged convex curved plate assembly, it is necessary to contact over the entire area. However, if the pressing amount is large, the sheet separation occurs because the current path is limited, the expansion of the nugget diameter is limited. Accordingly, the flat type electrode chip, the DR-type electrode chip or the like, a mere enlargement of the electrode tip diameter, far from practical.
[0013]
　For these measures, technique to expand the nugget diameter from another point of view has been proposed in JP 2012-55896 (Patent Document 1). Patent Document 1 includes a pair of main electrodes opposing each other between the plate pairs, one main electrode of its main electrodes (hereinafter, "first main electrode" in the description) to surround the an auxiliary electrode arranged annular discloses a resistance spot welding apparatus comprising a. In the technique disclosed in Patent Document 1, applying a polarity of the auxiliary electrode and the polarity of the first main electrode and the opposite polarity, between a pair of main electrodes, and a current between the first main electrode and the auxiliary electrode to. Thus, in addition to between the main electrodes, a current also flows between the first main electrode and the auxiliary electrode.
[0014]
　If the thickness of the metal plate is first main electrode and the auxiliary electrode in contact with a thin, because the contact area between the thin metal plate and the metal plate adjacent thereto is close to the first main electrode and the auxiliary electrode, Its contact region wide range of current flows. As a result, in Patent Document 1, it has a large nugget nugget diameter is formed.
[0015]
　However, in the technique disclosed in Patent Document 1, when the thickness of the metal plate is first main electrode and the auxiliary electrode in contact it is thick, the nugget diameter is not increased. Since the contact area between the thick thickness metal plate metal plate adjacent thereto are separated from the first main electrode and the auxiliary electrode, current range of the current flowing through the contact area is because not spread.
CITATION
Patent Document
[0016]
Patent Document 1: JP 2012-55896 JP
Summary of the Invention
Problems that the Invention is to Solve
[0017]
　As described above, in the spot welding of ultrahigh-tensile material, with the expansion of the proper current range, improvement in welded joint strength is required. However, the above measures are not any practical. In addition, the improvement in welded joint strength, where it is effective to enlarge the nugget diameter, the expansion of the nugget diameter, even with said technique disclosed in Patent Document 1 is insufficient.
[0018]
　An object of the present invention, resistance spot welding apparatus having the following characteristics, is to provide a composite electrode and the resistance spot welding method:
　- in the spot welding of ultrahigh-tensile material, it expands the proper current range;
　Ultra high-tension in spot welding of the wood, to improve the welded joint strength.
Means for Solving the Problems
[0019]
　Resistance spot welding apparatus according to an embodiment of the present invention is an apparatus for performing resistance spot welding to the plate set including a plurality of metal plates stacked,
　a pair disposed on opposite sides between the plate pairs comprising a composite electrode.
　Wherein each composite electrode,
　and the rod of the electrode body distal end surface is pressed in contact with the plate assembly,
　a through hole which the electrode body is inserted, rigid distal end surface is pressed in contact with said plate assembly a is a rigid body containing the insulated conductor to the electrode body,
　is connected to the rear end of the rigid, with the pressing of the electrode body and the rigid to the plate sets, pressed against the rigid comprising an elastic member for applying pressure, the.
[0020]
　In the above resistance spot welding apparatus can be configured part or all of the front end surface of the rigid body is a conductor.
[0021]
　In the above resistance spot welding apparatus, it is preferable that the rigid body is cylindrical. The rigid body, the shape of the inner peripheral edge is circular said tip surface, it is also possible to shape the outer periphery of the distal end surface is elliptical, it is oval or substantially square configuration.
[0022]
　In the above resistance spot welding apparatus, it is possible the elastic body or a structure is a compression coil spring, or a structure wherein the elastic member is a cylindrical resin molded body.
[0023]
　Any of the above resistance spot welding apparatus, it is preferable distance between the inner periphery of the front end surface of the outer peripheral edge and the rigid of the tip surface of the electrode body is 7mm or less.
[0024]
　Any of the above resistance spot welding apparatus, it is preferable to provide a cooling mechanism for cooling the rigid body.
[0025]
　Composite electrode according to an embodiment of the present invention is a composite electrode for use in a plate set of resistance spot welding including a plurality of metal plates stacked,
　rod-shaped distal end surface is pressed in contact with the plate group electrode and body,
　has a through hole which the electrode body is inserted, a rigid distal end surface is pressed in contact with the plate group, a rigid body comprising an insulated conductor to the electrode body,
　wherein is connected to the rear end of the rigid body, with the pressing of the electrode body and the rigid to the plate set, and an elastic member for applying pressure pressing said rigid.
[0026]
　In composite electrode described above, it is possible to adopt a configuration some or all of the front end surface of the rigid body is a conductor.
[0027]
　In composite electrode described above, it is preferable that the rigid body is cylindrical. The rigid body, the shape of the inner peripheral edge is circular said tip surface, it is also possible to shape the outer periphery of the distal end surface is configured elliptical or substantially rectangular.
[0028]
　In the composite electrode of the, or a structure wherein the elastic member is a compression coil spring, the elastic body can or a structure is a cylindrical resin molded body.
[0029]
　Any of the above composite electrode, it is preferable distance between the inner periphery of the front end surface of the outer peripheral edge and the rigid of the tip surface of the electrode body is 7mm or less.
[0030]
　Any of the above composite electrode, it is preferable to provide a cooling mechanism for cooling the rigid body.
[0031]
　Resistance spot welding method according to an embodiment of the present invention is a method for performing resistance spot welding to the plate set including a plurality of metal plates stacked, the first step, a second step, a third step, including a series of steps.
　The first step, in between the plate pairs, and a second electrode of the first electrode member and the rod of the rod-like causes disposed opposite has a through hole which the first electrode member is inserted the includes a first rigid body including a conductor which first elastic body is connected to the rear end, a conductor in which the second elastic body is connected to the rear end has a through hole in which the second electrode body is inserted 2 and rigid, is arranged opposite the.
　The second step, together with pressing said each distal end surface of the first electrode member and the second electrode member to said plate assembly while applying a pressure pressing from the first elastic body to said first rigid body, said second elastic member while applying a pressure pressing said second rigid from pressing the respective distal end surface of the first rigid body and said second rigid the plate assembly, pressurizing the plate pairs.
　The third step, while pressurizing the plate assembly, applying a current between the first electrode member and said second electrode member.
The invention's effect
[0032]
　Resistance spot welding apparatus, the composite electrode and the resistance spot welding method of the present invention have a remarkable effect of the following:
　- In the spot welding of ultra high-tensile steel, can be expanded to the proper current range;
　in spot welding and ultra high-tensile steel, It can be improved welding joint strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033]
[1] Figure 1 is a sectional view showing an example of a plate assembly which is a material to be welded.
[Figure 2A] Figure 2A is a schematic diagram showing an example of a resistance spot welding device of the first embodiment, showing a state before welding.
[Figure 2B] Figure 2B is a schematic diagram showing an example of a resistance spot welding device of the first embodiment, showing a state during welding.
FIG. 3 is a schematic diagram illustrating a situation where the nugget is formed by spot welding using a resistance spot welding apparatus shown in FIG.
FIG. 4 is the electrode - is a graph showing a relation between the distance and the maximum nugget diameter and proper current range of the rigid body.
[Figure 5A] Figure 5A is a schematic diagram showing an example of a resistance spot welding device of the second embodiment, showing a state before welding.
[Figure 5B] Figure 5B is a schematic diagram showing an example of a resistance spot welding device of the second embodiment, showing a state during welding.
FIG. 6 is a graph showing the results of a spot welding test in Example.
DESCRIPTION OF THE INVENTION
[0034]
　Hereinafter, resistance spot welding device of the present invention, the composite electrode and the resistance spot welding method, described in detail embodiments thereof.
[0035]
　Resistance spot welding apparatus of this embodiment is used to perform spot welding the plate pairs including a plurality of metal plates stacked. Composite electrode of the present embodiment is mounted on the spot welding device, it is used for spot welding. Resistance spot welding method of the present embodiment is used for spot welding using the spot welding device.
[0036]
　 1. Configuration of a resistance spot welding apparatus and the composite electrode
　Figure 1 is a sectional view showing an example of a plate assembly which is a material to be welded. As shown in the figure, the plate sets 1 as the material used in this embodiment has a portion two metal plates 2A, 2B are stacked with each other. Metal plate 2A, the material of the 2B are both tensile strength of 590 ~ 780 MPa class or more ultra-high-tensile steel. Metal plates 2A, 2B of the thickness are both about 0.5 ~ 3 mm, it may be the same as each other or may be different.
[0037]
　However, the plate assembly is depending on the form of structural parts produced by spot welding, but may be one having a portion which three or more metal plates are stacked. The material of the metal plate is not limited as long as it is possible to spot welding, the tensile strength is to may be a high-tensile steel below 590 MPa, it may be a mild steel. In addition, the presence or absence of plating, not limited to the type and the like. A plurality of metal plates stacked may be the same metal species, it may be a different metal species.
[0038]
　2A and 2B are schematic diagrams showing an example of a resistance spot welding device of the first embodiment. In these drawings, FIG. 2A shows a state before welding, Figure 2B shows a state during welding. Spot welding apparatus shown in FIGS. 2A and 2B, a pair of composite electrodes 10, 20. For convenience of explanation, while the (upper composite electrodes in FIGS. 2A and 2B) is also referred to as the first composite electrode 10, the other (lower side in FIGS. 2A and 2B of those composite electrode 10, 20 refers to a composite electrode) is also a second composite electrode 20. A first composite electrode 10 and the second composite electrode 20 is arranged on opposite sides between the plate pairs 1 one another, the structure is the same. That is, the first composite electrode 10 comprises a first electrode member 11 of the first rigid body 12, the second composite electrode 20 is provided with a second electrode member 21 and the second rigid 22.
[0039]
　First electrode member 11 is provided with a rod-shaped shank 11b straight, an electrode tip 11a which is attached to the distal end of the shank 11b, a rod-shaped as a whole. Shank 11b has a flange portion 11ba adjacent the electrode tip 11a. Electrode tip 11a is the DR type electrode tip. That is, the electrode tip 11a is a generally cylindrical tip portion has a projecting shape, the distal end surface 11aa is formed to the curvature radius of the larger convex surface. The electrode tip 11a, can also be used a known electrode tips in addition to DR-type electrode chip, may flat electrode tip, even with SR-type electrode chip or the like. Shank 11b has its rear end portion is fixed to the holder 14.
[0040]
　The first rigid body 12 is a cylindrical shape having a circular through-hole 12b on the central axis, the first electrode member 11 is disposed on the central axis. Electrode tip 11a and the flange portion 11ba of the first electrode member 11 is inserted into the first rigid 12, it is possible to relatively move along the axial direction between the tip end face 12a of the first rigid body 12 . By the flange portion 11ba of the first electrode member 11 comes into contact with the stopper surface 12c of the rear end portion of the first rigid body 12, the first rigid 12 does not fall off from the first electrode member 11.
[0041]
　The first rigid body 12 and the first electrode member 11 are not mutually are isolated, electrically connected. More specifically, a region first rigid 12 and the first electrode member 11 is capable of directly or indirectly connected, an insulator such as engineering plastic is disposed. For example, the insulator is disposed in a region shank 11b and the sliding of the areas of the through hole 12b of the first rigid body 12.
[0042]
　Holding plate 15 is fixed to the front end of the holder 14. Between the rear end and the holding plate 15 of the first rigid 12, the first elastic body 13, the compression coil spring 13A is disposed. The shank 11b of the first electrode member 11 penetrates through the upper central axis of the compression coil spring 13A (the first elastic member 13). The first rigid body 12 can relatively move along the shank 11b.
[0043]
　Similarly, the second electrode member 21 is provided with a rod-shaped shank 21b straight, and an electrode tip 21a which is attached to the distal end of the shank 21b, a rod-shaped as a whole. Shank 21b has a flange portion 21ba adjacent the electrode tip 21a. Electrode tip 21a is the DR type electrode tip. Shank 21b has its rear end portion is fixed to the holder 24.
[0044]
　The second rigid 22 is cylindrical with a circular through-hole 22b on the central axis, the second electrode bodies 21 are disposed on the central axis. Electrode tip 21a and the flange portion 21ba of the second electrode member 21 is housed in the second rigid 22, it is possible to relatively move along the axial direction between the tip end face 22a of the second rigid 22 . By the flange portion of the second electrode member 21 21ba contacts the stopper surface 22c of the rear end of the second rigid 22, the second rigid 22 does not fall off from the second electrode member 21.
[0045]
　A second rigid 22 second electrode 21 are not mutually are isolated, electrically connected. More specifically, in a region between the second rigid 22 second electrode member 21 is capable of directly or indirectly connected, an insulator such as engineering plastic is disposed. For example, the insulator is disposed in the region which slides a shank 21b of the areas of the through hole 22b of the second rigid 22.
[0046]
　Holding plate 25 is fixed to the front end of the holder 24. Between the rear end and the retaining plate 25 of the second rigid 22, the second elastic member 23, the compression coil spring 23A is disposed. The shank 21b of the second electrode member 21 penetrates through the upper central axis of the compression coil spring 23A (the second elastic member 23). The second rigid 22 can relatively move along the shank 21b.
[0047]
　Shank 11b constituting the first electrode 11 and the second electrode member 21, respectively, 21b and the electrode tip 11a, the material of 11a, chromium copper, chromium zirconium copper, beryllium copper, alumina dispersion strengthened copper or copper tungsten. However, the material of the first electrode member 11 and the second electrode body 21, as long as the hold as the electrode is not particularly limited.
[0048]
　The first rigid body 12 and the second rigid 22 is a rigid body which is not deformed against an external force, a conductor such as metal. The first rigid body 12 and the second rigid 22, each tip surface 12a, may be composed of a total of 22a with a conductor may constitute a part of a conductor.
[0049]
　The material of the first rigid body 12 and the second rigid 22 so long as it has a high electrical conductivity is not particularly limited, and may be the same as the first electrode member 11 and the second electrode bodies 21, be different good. However, the material of the first rigid body 12 and the second rigid 22 should have at least welded plate pair high electrical conductivity than the (metal plate). Although details will be described later, in order to draw effectively towards the current flowing through the plate assembly in at spot welded to the first rigid 12 and the second rigid 22.
[0050]
　The first composite electrode 10 and the second composite electrode 20 of the structure, each of the holders 14 and 24 are attached to the spot welding gun (not shown). Specifically, the welding gun has a pair of arms capable of opening and closing operation, the holder 14 of the first composite electrode 10 is attached to the distal end of one arm of which the second composite on the tip of the other arm holder 24 of the electrode 20 is mounted. The opening and closing operation of both arms, the first composite electrode 10 and the second composite electrode 20, or closer or apart from each other. At this time, in a state where the first electrode 11 second electrode 21 is arranged coaxially to face each other, it disposed coaxially with the first rigid 12 also face each other second rigid 22 . However, one of the pair of arms, but may be fixed.
[0051]
　Further, the first electrode 11 second electrode 21 is connected to a power supply device (not shown). For example, when using a DC power supply as a power supply, the positive pole of the power source is connected to the first electrode member 11, the negative pole of the power source is connected to the second electrode member 21. Connecting the positive electrode and the negative electrode may be reversed. The power supply device, it is also possible to use an AC power supply.
[0052]
　2. Resistance spot welding
　to FIG. 2 and FIG. 3 below with reference, describing a process of spot welding by spot welding apparatus of this embodiment.
[0053]
　First, as shown in FIG. 2A, as the material, two metal plates 2A, 2B is prepared a plate assembly 1 with stacked portions together. Then, in between the plate pairs 1, causes disposed to face the first electrode member 11 of the first composite electrode 10 and the second electrode 21 of the second composite electrode 20, each of the first rigid body 12 When is disposed opposite a second rigid 22. This operation is performed by the movement or transport of the plate sets 1 of the welding gun.
[0054]
　Then run the closing operation of both arms of the welding gun to initiate a first pressing operation of the composite electrode 10 and the second composite electrode 20 of the plate assembly 1. Thus, the first composite electrode 10, the holder 14 is moved toward the plate group 1, and at the same time, the second composite electrode 20, the holder 24 moves toward the plate group 1. Accordingly, the first composite electrode 10, first, the distal end surface 12a of the first rigid 12 is pressed in contact with the surface of the metal plate 2A plate assembly 1, further movement of the first rigid 12 limits It is. In the second composite electrode 20, first, the distal end surface 22a of the second rigid 22 is pressed in contact with the surface of the metal plate 2B plate assembly 1, further movement of the second rigid 22 is restricted.
[0055]
　Furthermore, the first composite electrode 10, first electrode member 11 continues to move toward the metal plate 2A. At this time, narrowing the distance between the first rigid 12 and the holding plate 15 is gradually first elastic member 13 (compressive coil springs 13A) is compressed and deformed. At the same time, the second composite electrode 20, second electrode member 21 continues to move toward the metal plate 2B. At this time, narrowing the interval between the holding plate 25 and the second rigid 22 gradually, the second elastic member 23 (compressive coil springs 23A) is compressed and deformed.
[0056]
　Then, as shown in FIG. 2B, the first composite electrode 10, the distal end surface of the first electrode member 11 11aa is pressed in contact with the surface of the metal plate 2A, further movement of the first electrode member 11 is limited It is. At the same time, the second composite electrode 20, the distal end surface of the second electrode member 21 21aa is pressed in contact with the surface of the metal plate 2B, further movement of the second electrode member 21 is limited.
[0057]
　In this manner, the plate assembly 1, together are sandwiched by the first electrode member 11 and the second electrode 21 facing each other, it is sandwiched by the first rigid 12 and the second rigid 22 facing each other. In this case, the plate assembly 1, is pressed against the pressure applied from the first electrode 11 and the second electrode member 21, the pressure pressing from the first rigid 12 and the second rigid 22 is added.
[0058]
　Here, the first rigid 12, the repulsive force of the compression deformation of the first elastic body 13 are deformed by compression acts, the second rigid 22, compressive deformation of the second elastic member 23 which is deformed by compression the repulsive force of acting. Therefore, the metal plate 2A constituting the plate group 1, 2B each other, not only pressurized contact area between the first electrode 11 and the second electrode member 21, annular region (first rigid around its pressurized contact area) between the 12 and the second rigid 22, in a state where sufficient contact over a wide range. Thus, occurrence of sheet separation is suppressed.
[0059]
　Once in this state, by driving the power supply to apply a current between the first electrode member 11 and the second electrode member 21.
[0060]
　Figure 3 is a schematic diagram illustrating a situation where the nugget is formed by spot welding using a resistance spot welding apparatus shown in FIG. In the figure, the dotted arrows indicate the flow of welding current.
[0061]
　As shown in FIG. 3, as compared to conventional spot welding, a metal plate 2A, the contact area 2B each other not only in the contact area between the first electrode 11 and the second electrode body 21, a first rigid around its and over a wide range and to the contact area between the 12 and the second rigid 22. Therefore, when the first electrode 11 to apply a current between the second electrode member 21, significant without sheet separation occurs within the plate assembly 1, i.e. a metal plate 2A, Within 2B, current extensively spread flows.
[0062]
　Specifically, current flows from the first electrode member 11 not only flows simply toward the second electrode member 21, after being drawn toward the first electrode 11 to the first rigid 12, second rigid drawn towards the 22, finally it flows toward the second electrode member 21. Metal plates 2A, 2B to each other while sufficient contact with a region opposed to the first rigid 12 by a strong pressure from the first rigid 12 and the second rigid 22 and the second rigid 22, first rigid 12 and the second both rigid body 22 is because having a high electrical conductivity.
[0063]
　In general, dust is generated from between the metal plates are, upon application of a large current to the electrode, the contact portion of the electrode and the metal plate becomes excessive heating, there are cases where dust is generated from the metal plate surface. If the first rigid 12 and the second rigid 22 as in this embodiment conductor and, a bypass current from the first electrode 11 and the second electrode member 21 to the first rigid 12 and the second rigid 22 conductor to, suppressed heat generation at the contact portion of the electrode and the metal plate, there is an advantage that it is possible to suppress dust generation from the metal plate surface.
[0064]
　Therefore, the metal plate 2A, since the 2B together are pressed strongly pressurized by the first structure 12 and second structure 22, a metal plate 2A, melted over a contact area wide range of 2B to each other, a large nugget nugget diameter 3 is formed.
[0065]
　According to the spot welding of the present embodiment, it is possible to enlarge the nugget diameter, it is possible to improve the welded joint strength, including CTS. Moreover, it is possible with the expansion of the nugget diameter to expand the proper current range.
[0066]
　Meanwhile, in order to express the inhibitory effect of sheet separation, the spacing between the inner periphery of the outer peripheral edge and the distal end surface 12a of the first rigid 12 of the distal end surface 11aa of the first electrode member 11, and the tip of the second electrode member 21 spacing between the inner periphery of the outer peripheral edge and the distal end face 22a of the second rigid 22 surface 21aa is important. Hereinafter collectively intervals, the electrode - referred to as interval rigid. Electrode - spacing rigid, to the extent that is not in contact with the electrode body and the rigid during welding, it is preferable to approach as much as possible. Electrode - the interval of the rigid body is too wide, on the inhibitory effect of the sheet separation is reduced, the current is less likely to spread. Electrode - spacing rigid is preferably 7mm or less. More preferably 5mm or less, more preferably less than 3mm. On the other hand, the electrode - the interval of the rigid body is too narrow, the electrode body and the rigid body energized by inadvertently contact during welding, the welding current becomes unstable. Thus, the electrode - the spacing of the rigid body, the practical is preferably 0.3mm or more. More preferably 0.5mm or more, and still more preferably less than 1.0mm.
[0067]
　4, the electrode - is a graph showing a relation between the distance and the maximum nugget diameter and proper current range of the rigid body. Relationship shown in FIG. 4, using ( "SORPAS (registered trademark)" manufactured by SCSK Corporation) spot welding analysis software, the electrodes of the spot welding - a result of analyzing the effect of spacing of the rigid body. In the analysis, it sets the condition that current spreads toward the electrode body to the rigid, electrodes - were variously change the interval of the rigid body. Metal plates to be welded, the thickness t has a 1.2mm tensile strength 1500MPa class hot stamping steel plate (non-coated). The material of the electrode body and rigid was chromium copper (Cu-1 wt% Cr). Electrode tip of the electrode body has an outer diameter, including the distal end surface is 8 mm, the radius of curvature R of the front end surface is set to 80mm of SR type electrode tip. Pressure applied by the electrode body and 3.43kN (350kgf), energizing time 16Cycle: was (frequency at 60 Hz). Then, the electrode was changed - the welding current variously changed at each interval of the rigid body, were investigated nugget diameter and occurrence or non-occurrence of dust for each condition.
[0068]
　Here, the electrode - to evaluate the maximum nugget diameter and proper current range of each of the spacing of the rigid body. Maximum nugget diameter, was the largest nugget diameter that dust does not occur. Appropriate current range, nugget diameter from the current value nugget 4√t was obtained as a current value range up to the maximum current value dust is not generated. As shown in FIG. 4, the electrode - the interval of the rigid body is 7mm in the boundary, the electrode - the more closely spaced rigid, maximum nugget diameter is large, it can be seen that the proper current range is expanded. Therefore, the preferred electrodes - it can be said that the spacing of the rigid body is 7mm or less.
[0069]
　In the spot welding apparatus of this embodiment, the first electrode 11 (in particular, electrode tip 11a) is in a state of being surrounded by the first rigid 12. Similarly, the second electrode 21 (in particular, electrode tip 21a) is in a state of being surrounded by a second rigid 22. Therefore, there is a possibility that heat generated by spot welding tends to accumulate in the first electrode member 11 and the second electrode 21, electrode tip 11a, the life of 21a decreases. Therefore, it is possible to suppress the heat storage is cooled actively first rigid 12 and the second rigid 22, it is desirable to indirectly cool the first electrode member 11 and the second electrode member 21. As the cooling structure, for example, a cooling water channel provided inside the first rigid 12, it may be to circulate cooling water in the cooling water channel. Another cooling structure may be sprayed with a coolant on the outer peripheral surface of the first rigid body 12. In the latter case, the cooling water used which rust agent is added. These cooling structures can be similarly applied to the second electrode member 21.
[0070]
　
　FIGS. 5A and 5B are schematic views illustrating an example of a resistance spot welding device of the second embodiment. In these drawings, FIG. 5A shows a state before welding, and FIG. 5B shows a state during welding. Spot welding apparatus of the second embodiment shown in FIGS. 5A and 5B, FIG. 2A and is intended to be based on the configuration of the spot welding device of the first embodiment shown in FIG. 2B, overlapping description will be omitted .
[0071]
　The shank 11b of the first electrode member 11 in the second embodiment does not have a flange portion 11ba as in the first embodiment. Accordingly, the first rigid 12 has no stopper surface 12c of the rear portion as in the first embodiment.
[0072]
　The rear end of the first rigid 12 movable plate 16 is fixed, the holding plate 15 is fixed to the front end of the holder 14. The shank 11b of the first electrode member 11 penetrates their movable plate 16 and the holding plate 15. Between the holding plate 15 and movable plate 16, the first elastic member 13, a cylindrical resin molded body 13B is disposed. The shank 11b of the first electrode member 11 penetrates through the upper central axis of the resin molded body 13B (first elastic member 13). The periphery of the holding plate 15, a plurality of guide bolts 17 extending through the periphery of the movable plate 16 is screwed. Accordingly, the first elastic member 13 is held in a state sandwiched between the holding plate 15 and movable plate 16. The first rigid body 12, integrally with the movable plate 16, while being guided by the guide bolts 17, it is possible to relatively move along the shank 11b.
[0073]
　The first rigid body 12 and the first electrode member 11 are not mutually are isolated, electrically connected. More specifically, a region first rigid 12 and the first electrode member 11 is capable of directly or indirectly connected, an insulator such as engineering plastic is disposed. For example, the movable plate 16 capable of shank 11b and the sliding is formed by an insulator.
[0074]
　Similarly, the shank 21b of the second electrode member 21 in the second embodiment does not have a flange portion 21ba as in the first embodiment. Accordingly, the second rigid 22 has no stopper surface 22c of the rear portion as in the first embodiment.
[0075]
　The rear end of the second rigid 22 movable plate 26 is fixed, the holding plate 25 is fixed to the front end of the holder 24. The shank 21b of the second electrode member 21 penetrates their movable plate 26 and the holding plate 25. Between the retaining plate 25 and movable plate 26, the second elastic member 23, a cylindrical resin molded body 23B is disposed. The shank 21b of the second electrode member 21 penetrates through the upper central axis of the resin molded body 23B (second elastic member 23). The periphery of the holding plate 25, a plurality of guide bolts 27 extending through the periphery of the movable plate 26 is screwed. Thus, the second elastic member 23 is held in a state sandwiched between the holding plate 25 and the movable plate 26. The second rigid 22 is integral with the movable plate 26, while being guided by the guide bolts 27, it is possible to relatively move along the shank 21b.
[0076]
　A second rigid 22 second electrode 21 are not mutually are isolated, electrically connected. More specifically, in a region between the second rigid 22 second electrode member 21 is capable of directly or indirectly connected, an insulator such as engineering plastic is disposed. For example, the movable plate 26 capable of shank 21b and the sliding is formed by an insulator.
[0077]
　The material of the first elastic body 13 and the second elastic body 23 is excellent in durability, and urethane resins having appropriate elasticity.
[0078]
　The welding by such an arrangement of the spot welding apparatus, the first rigid 12 and the second rigid 22, first elastic member 13 and the second elastic member 23 which is compressed and deformed, i.e. the resin molded body 13B, the pressing force from 23B is It is added. This situation is the same as the first embodiment. Therefore, the same effects as the first embodiment in the second embodiment.
Example
[0079]
　In order to confirm the effect of the present invention was carried out welding tests to perform spot welding using a spot welding apparatus of the first embodiment shown in FIG. 2. As test materials, plate thickness using the 1.6mm tensile strength 1500MPa class hot stamping steel plate (non-coated), the steels were prepared a number of two stacked plates of sets of each other DoitaAtsu. As the electrode tip and the electrode tip of the second electrode of the first electrode member, using a DR-type electrode tip. Each DR electrode tip, the material is chromium copper (Cu-1 wt% Cr), tip diameter with an outer diameter of 12mm is 6 mm, the radius of curvature R of the front end surface was 40 mm. The first rigid body and second rigid, material inner diameter was 13mm chrome copper (Cu-1 wt% Cr).
[0080]
　Shows the welding conditions shown in Table 1 below. Change the welding current to the time of spot welding, behavior and Chile that nugget to grow is to investigate the current generated. It should be noted, 1cycle in Table 1 is a 1/60 of a second.
[0081]
[Table 1]

[0082]
　For comparison, as a conventional general method, the test was carried out to perform the spot welding only by sandwiching a plate assembly simply by a pair of electrode tips. Test materials, electrode tip and the welding conditions were the same as that in the present invention embodiment.
[0083]
　For each plate pair after the spot welding was performed torsion test. It was measured nugget diameter from the appearance of the nugget which appeared by torsion testing. Specifically, measured from two directions perpendicular diameter of the nugget to each other, and the average value of both the nugget diameter.
[0084]
　Figure 6 is a diagram showing the correlation between welding current value and a nugget diameter, obtained in test Example. Test material is 1500MPa grade hot stamping steel sheet having a thickness t is 1.6 mm (non-plated).
[0085]
　As shown in FIG. 6, in the present invention example, compared with the comparative example, suitability current range and the maximum nugget diameter is greatly enlarged. In the comparative example, the maximum nugget diameter to the range of about 5√T, in the present invention example, the maximum nugget diameter exceeds 6√T. Further, in the comparative example, the proper current range to the range of about 2.6 kA, in the present invention example, the proper current range is expanded to approximately 4.0KA. Therefore, the present invention, in the spot welding of ultra high-tensile steel, can expand the proper current range, moreover since the nugget diameter is enlarged, it has been demonstrated that is possible to improve the welded joint strength.
[0086]
　Others The invention is not limited to the above embodiments, without departing from the scope of the present invention, various modifications are possible. For example, the shape of the rigid body is not limited to a cylindrical shape, it is possible to change depending on the plate set in the form of welded. That is, the shape of the inner peripheral edge of the front end surface of the rigid body is circular, the shape of the outer peripheral edge of the front end surface may be those which are elliptical, oval or substantially square.
Industrial Applicability
[0087]
　The present invention can be effectively utilized in the production of structural parts of ultrahigh-tensile material.
DESCRIPTION OF SYMBOLS
[0088]
　　1: plate set, 2A: a metal plate, 2B: a metal plate, 3:
　　Nugget, 10: first composite electrode, 11: first electrode
　　member, 11a: electrode tip, 11aa: the distal end surface of the electrode
　　tip, 11b: shank, 11ba: flange portion of the
　　shank, 12: first rigid, 12a: front end face of the first
　　rigid, 12b: through-hole of the first rigid, 12c: stopper surface of the first
　　rigid, 13: elastic member, 13A: compression coil spring,　　
13B: resin molding 14: holder, 15: holding　　
plate, 16: movable plate, 17: guide
　　bolt 20: the second composite electrode, 21: second electrode member,
　　21a: electrode tip, 21aa: the electrode tip tip
　　face, 21b: shank, 21ba: flange portion of the
　　shank, 22: second rigid, 22a: front end surface of the second
　　rigid, 22b: through-hole of the second rigid, 22c: stopper surface of the second rigid
　　body, 23 : Elastic body, 23A: compression coil　　
spring, 23B: Resin molded body, 24: holder, 25: holding　　
plate, 26: movable plate, 27: guide bolts

WE claims

An apparatus for performing resistance spot welding to the plate set including a plurality of metal plates stacked,
　the resistance spot welding apparatus,
　comprising a pair of composite electrodes disposed on opposite sides between the plate pairs,
　wherein each composite electrode,
　and the rod of the electrode body distal end surface is pressed in contact with the plate assembly,
　a through hole which the electrode body is inserted, rigid distal end surface is pressed in contact with said plate assembly a is a rigid body containing the insulated conductor to the electrode body,
　is connected to the rear end of the rigid, with the pressing of the electrode body and the rigid to the plate sets, pressed against the rigid comprising an elastic member for applying pressure, a resistance spot welding apparatus.
[Requested item 2]
　A resistance spot welding apparatus according to claim 1,
　some or all of the front end surface of the rigid body is a conductor, the resistance spot welding device.
[Requested item 3]
　A resistance spot welding apparatus according to claim 1 or 2,
　wherein the rigid body is cylindrical, resistance spot welding device.
[Requested item 4]
　A resistance spot welding apparatus according to claim 1 or 2,
　wherein the rigid bodies, the shape of the inner peripheral edge of the front end surface is circular, elliptical shape of the outer peripheral edge of the tip surface, oval or substantially square in it, resistance spot welding device.
[Requested item 5]
　A resistance spot welding apparatus according to any one of claims 1 to 4,
　wherein the elastic member is a compression coil spring, resistance spot welding device.
[Requested item 6]
　A resistance spot welding apparatus according to any one of claims 1 to 4,
　wherein the elastic member is a cylindrical resin molded body, the resistance spot welding device.
[Requested item 7]
　A resistance spot welding apparatus according to any one of claims 1 to 6,
　the interval between the inner periphery of the front end surface of the outer peripheral edge and the rigid of the tip surface of the electrode body is 7mm or less, resistance spot welding equipment.
[Requested item 8]
　A resistance spot welding apparatus according to any one of claims 1 to 7,
　comprising a cooling mechanism for cooling the rigid, resistance spot welding device.
[Requested item 9]
　A composite electrode for use in a plate set of resistance spot welding including a plurality of metal plates stacked,
　the composite electrode is
　a rod-shaped electrode body distal end surface is pressed in contact with the plate assembly,
　the electrode assembly there has a through hole to be inserted, a rigid distal end surface is pressed in contact with the plate group, a rigid body comprising an insulated conductor to the electrode body,
　connected to the rear end of the rigid It is, with the pressing of the electrode body and the rigid to the plate set, and an elastic member for applying pressure pressing on the rigid, composite electrode.
[Requested item 10]
　A composite electrode according to claim 9,
　part or all of the front end surface of the rigid body is a conductor, the composite electrode.
[Requested item 11]
　A composite electrode according to claim 9 or 10,
　wherein the rigid body is cylindrical, the composite electrode.
[Requested item 12]
　A composite electrode according to claim 9 or 10,
　wherein the rigid body, the shape of the inner peripheral edge of the front end surface is circular, the shape of the outer peripheral edge of the tip surface is elliptical or substantially rectangular, composite electrode .
[Requested item 13]
　A composite electrode according to any one of claims 9-12,
　wherein the elastic member is a compression coil spring, the composite electrode.
[Requested item 14]
　A composite electrode according to any one of claims 9-12,
　wherein the elastic member is a cylindrical resin molded body, the composite electrode.
[Requested item 15]
　A composite electrode according to any one of claims 9-14,
　gap between the inner periphery of the front end surface of the outer peripheral edge and the rigid of the tip surface of the electrode body is 7mm or less, the composite electrode .
[Requested item 16]
　A composite electrode according to any one of claims 9-15,
　comprising a cooling mechanism for cooling the rigid composite electrode.
[Requested item 17]
　A method for performing resistance spot welding to the plate set including a plurality of metal plates stacked,
　the resistance spot welding method,
　in between the plate pairs, the first electrode member and the second electrode of the rod-shaped rod-like together to place the body and facing, the first rigid body comprising a first elastic body connected to electrical conductors on the rear end has a through hole which the first electrode member is inserted, the second electrode body a second rigid body containing the inserted through holes of a conductor in which the second elastic body is connected to the rear end, a first step of arranging to face a
　first electrode member and the second electrode member each distal end surface with pressing the plate group, wherein while applying pressure pressing said first rigid from the first elastic body, while applying a pressure pressing said second rigid from said second elastic member, said first rigid and pressing each distal end surface of the second rigid the plate assembly, pressurizing the plate pairs And second step,
　while pressurizing the plate assembly, including a third step of applying a current between the second electrode member and the first electrode member, resistance spot welding method.