JP6426043B2 - Rivet for dissimilar material joining, dissimilar material joined body, and dissimilar material joining method - Google Patents

Description

  The present invention relates to a rivet for joining dissimilar materials, a joined body of dissimilar materials, and a method for joining dissimilar materials.

  In recent years, fuel consumption has been improved by reducing the weight of a vehicle such as a car in response to global environmental problems caused by exhaust gas and the like. In addition, various attempts have been made to improve the safety in the event of a vehicle collision of a car without inhibiting the reduction in weight as much as possible. In particular, for car body structures of automobiles, it has been increased to substitute a part of conventionally used steel materials with light alloy materials such as aluminum alloy materials and magnesium materials which are lighter in weight and excellent in energy absorption. doing.

  The aluminum alloy material used for the car body etc. of an automobile has a form such as a rolled plate material, an extruded material, or a forged material. For example, as outer panels and inner panels of large panel structures such as car roofs, hoods, fenders, doors and trunk lids, 6000 series (Al-Mg-Si series) of AA standard or JIS standard, and 5000 series ( The use of aluminum alloy sheets such as Al-Mg-based is being studied. These aluminum alloy materials need to be used in combination with steel materials (steel members) such as steel plates or mold steels originally used for general use unless all parts of the vehicle body are made of aluminum alloy materials. Therefore, it is necessarily necessary to join the aluminum alloy material and the steel material.

In Patent Documents 1 to 5, after a rivet made of steel is joined in advance to a light alloy material such as an aluminum alloy material, the head of the rivet and the steel material are sandwiched between a pair of electrodes and electricity is supplied thereto. Discloses a technique for spot welding steel materials and joining light alloy materials and steel materials.
In Patent Document 1, a steel rivet is driven into a light alloy material, the light alloy material is punched out at the shaft, and the rivet is crimped to the light alloy material, and then the shaft of the rivet and the steel material are spot welded. There is. At the head of the rivet, a recess (annular groove) surrounding the shaft is formed.
Similarly, in Patent Document 2, a steel rivet is driven into a light alloy material, the light alloy material is punched at the shaft portion, and the rivet is crimped to the light alloy material, and then the rivet shaft and the steel material are spot welded doing. The rivet has a recess (annular groove) surrounding the shaft at the head, and the shaft has a large cross-sectional area toward the tip. Further, a projection (protruding part) is formed on the tip end face of the shank of the rivet.
Patent Document 3 describes that a recessed portion is formed on the circumferential surface of the tip of the shaft portion of a steel rivet, and the recessed portion connected to the recessed portion is formed in the light alloy material when the rivet is driven into the light alloy material. It is done. Further, according to Patent Document 3, a film (insulation layer) having higher resistance than steel material is formed on a portion of the surface of the head and shaft of the rivet which contacts the light alloy material after being driven into the light alloy material. Is described.
In Patent Document 4, a steel rivet is pressed into a pilot hole formed in a light alloy material, the rivet is caulked and fixed to the light alloy material, and then a shaft of the rivet and a steel material are spot welded. The shank of this rivet has a tip with a diameter smaller than the diameter of the pilot hole, a base end larger than the diameter of the pilot hole, and a curved diameter portion between the tip and the base (diameter smaller than the tip) It consists of
In Patent Document 5, a steel rivet is driven into a light alloy material, the light alloy material is punched at the shaft portion, and at the same time the rivet is crimped to the light alloy material, and then the shaft portion of the rivet and the steel material are spot welded. ing. The rivet comprises a ridge at the head and at the tip of the shank. Further, according to Patent Document 5, a film (insulation having resistance higher than that of a steel material is formed on a head portion by forming a concave portion (annular groove) surrounding a shaft portion and in contact with the light alloy material after being punched into the light alloy material. It is described to form a layer).

JP, 2009-285678, A JP, 2010-207898, A JP, 2014-580, A JP, 2014-121710, A JP, 2014-173683, A

  In FIG. 2 of Patent Document 2, a steel different rivet for jointing different materials in which a protrusion is formed at the center of the tip of the shaft portion is described. However, when such a rivet is used, as shown in FIG. 10, the spot welding electrode 211 may cause misalignment from the rivet 213. In that case, the rivet 213 which joins the light alloy material 215 and the steel material 217 may be inclined. In the inclined rivet 213, the shaft 219 of the rivet 213 contacts the steel material 217 at two points, the protrusion 221 and the tip peripheral edge 223 of the shaft 219.

  When the rivet 213 is inclined as described above, there is a possibility that the strength of caulking fixing of the rivet 213 and the light alloy material 215 may be reduced. When the spot welding electrode 211 is energized in this state, the welding nugget 225 does not grow well, and the nugget diameter is smaller than in the case where no misalignment of the spot welding electrode 211 occurs. As a result, the required high bonding strength can not be obtained. The reason why the growth of the welding nugget 225 is hindered is that the spot welding current is relatively large in area including the two contact points (the central protrusion 221 and the peripheral edge 223) between the shaft 219 of the rivet 213 and the steel 217. It is considered that the current flows in a dispersed manner, and a sufficiently high current density can not be obtained. However, there is no disclosure in the cited references regarding preventing the reduction of the current density due to the inclination of the rivet.

  The present invention has been made in view of the above-mentioned matters, and an object thereof is to suppress a decrease in current density even when misalignment between a shaft of a spot welding electrode and a shaft of a rivet occurs, and a necessary size. It is an object of the present invention to provide a rivet for joining different materials which can stably form the nugget of the present invention, a joined material of different materials, and a joining method of different materials.

The rivet for dissimilar material joining according to the present invention comprises a plate-like head fixed to a light alloy by caulking, a shaft extending from the head and penetrating the light alloy and having a tip spot-welded to a steel material And a rivet for joining different materials made of steel,
The head has a rectangular plane having a ratio (L / W) of length (L) to width (W) of 1.5 or more and 3 or less,
The shaft portion is rectangular in a bottom view,
A linear groove is formed in the longitudinal direction at root portions on both sides of the shaft in the head,
A plurality of linearly extending protrusions disposed in parallel in a width direction, a longitudinal direction, or an oblique direction inclined from the longitudinal direction of the axial portion are formed on the tip end surface of the axial portion .
The rivet for dissimilar material joining according to the present invention comprises a plate-like head fixed to a light alloy by caulking, a shaft extending from the head and penetrating the light alloy and having a tip spot-welded to a steel material And a rivet for joining different materials made of steel,
The head is a rectangular plane having a ratio (L / W) of length (L) to width (W) of 1.5 or more and 3 or less,
The shaft portion is rectangular in a bottom view,
A linear groove is formed in the longitudinal direction at root portions on both sides of the shaft in the head,
A knurled protrusion is formed at the tip of the shaft portion.
The dissimilar material joined body according to the present invention is characterized by comprising the rivet for dissimilar material joining and the light alloy material and the steel material joined respectively by the rivet for dissimilar material joining.
The dissimilar material joining method according to the present invention is a dissimilar material joining method in which the steel material and the light alloy material are joined using the rivet for dissimilar material joining described above,
Driving the light alloy material from the tip end side of the shaft of the different material bonding rivet, and caulking and fixing the different material bonding rivet to the light alloy material;
The rivet for dissimilar material joining crimped and fixed to the light alloy material is superimposed on the steel material, the head of the rivet for dissimilar material bonding and the steel material are sandwiched by a pair of electrodes, and the dissimilar material is joined using the pair of electrodes. Applying a current to the electrode while pressing a rivet and the steel material, and spot welding the shaft portion of the rivet for joining different materials and the steel material;
It is characterized by including.

In the rivet for dissimilar material joining of the present invention, the head is provided with a rectangular plane having an aspect ratio such that the ratio (L / W) of length (L) to width (W) is 1.2 or more and 3 or less. A plurality of linearly extending protrusions (projections) or knurled protrusions (projections) are formed on the tip end surface of the shaft portion. With such a shape of the head portion and the shaft portion, the grounding point of the electrode can be easily secured even if the electrode position at the time of spot welding varies.
In addition, even when a deviation (core deviation) between the axis of the electrode and the axis of the rivet occurs during spot welding, the rivet is less likely to be inclined as compared with the case where only the conventional central projection is formed. Even if the electrodes are misaligned during spot welding and the rivet is inclined, the projections are arranged relatively close, so the welding current is relatively narrow in the region including the adjacent projections. Flow. As a result, a reduction in current density can be suppressed, a nugget of a necessary size can be stably formed, and a necessary bonding strength can always be stably ensured.

It is a perspective view showing an example of a rivet. It is the sectional view on the AA line of the rivet shown in FIG. (A), (B) is explanatory drawing which shows a mode that a rivet is pierced into a light alloy material from the front end side of an axial part. (A), (B) is explanatory drawing which shows a mode that a rivet and steel materials are resistance spotted. It is explanatory drawing which shows the misalignment of an electrode typically. (A) is a BB sectional view taken on the line of FIG. 5, (B) is a CC sectional view taken on the line of FIG. It is width direction sectional drawing of the rivet of a 1st modification. The width direction sectional view of the rivet of the 2nd modification is shown. (A)-(D) are typical bottom views which show the protrusion of the rivet tip of another modification. It is sectional drawing which shows the state of core offset of the electrode in the resistance spot welding process using the conventional rivet.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a view for explaining an embodiment of the present invention, and is an external perspective view of a rivet for joining different materials (hereinafter simply referred to as a rivet), and FIG. 2 is a sectional view taken along the line AA of FIG. Section).

  The rivet 11 is entirely made of steel, and has a plate-like head 13 and a shaft 15 extending from the head 13 in the normal direction of the plate surface. The head 13 has a rectangular plane perpendicular to the joining direction (axial direction). The ratio (L / W) of the length (L) in the longitudinal direction of the head 13 to the length (W) in the width direction orthogonal to the longitudinal direction is 1.5 or more and 3 or less. The shaft portion 15 is rectangular in a bottom view, and has a block shape of a substantially rectangular parallelepiped as a whole.

  The shaft portion 15 has a plurality of linearly extending protrusions 19 on the tip end surface 17. The protrusions 19 project in the axial direction of the shaft portion 15 and include a central protrusion 21 disposed at the center in the width direction and side protrusions 23 and 23 disposed on both sides of the central protrusion 21. Ru. The side protrusions 23, 23 are disposed inside the side surfaces 25, 25 of the width direction end of the shaft portion 15. The central projection 21 and the side projections 23 are formed to have the same projecting height. In addition, linear grooves 27 and 27 are formed at root portions on both sides of the shaft portion 15 in the head portion 13.

  Although the said rivet 11 can be shape | molded by a forge process from a raw material, you may shape | mold using cutting, a knurl process, etc. together.

  It is preferable to form an insulating layer on the entire surface of the rivet 11 excluding the side surfaces 29 and 29 of the widthwise end of the head portion 13 and the tip end surface 17 of the shaft portion 15. The insulating layer may be a film having a resistance higher than that of the steel material. The insulating layer can be formed, for example, of an insulating paint such as DISGO (registered trademark), RAFLE (registered trademark), GEOMET (registered trademark), polyester resin precoat, silicone elastomer, and the like. The insulating layer may be formed at a position where the rivet 11 and the light alloy material are in contact when the rivet 11 is punched into the light alloy material described later.

  In the present specification, as the type of light alloy material, magnesium (including metal and alloy), magnesium (including metal and alloy), and the like are included in addition to aluminum (including metal and alloy).

Next, each process of the dissimilar-material joining method which uses the rivet 11 of the said structure for dissimilar-material joining of a light alloy material and steel materials is demonstrated.
First, as shown in FIG. 3A, the light alloy material 33 is placed on the cylindrical lower die 31, and the rivet 11 is placed immediately above the lower die 31. Then, the rivet 11 is driven into the light alloy material 33 from the tip end side of the shaft portion 15 by the upper die (punch) 35 disposed on the upper side of the rivet 11. The rivet 11 is disposed on the light alloy material 33 while being supported by a suitable support device. The rivet 11 can also be disposed on the light alloy material 33 by magnetically attaching it to the punch 35 which is magnetized.

  Next, the punch 35 is lowered toward the light alloy 33, and the rivets 11 are driven into the light alloy 33. Then, as shown in FIG. 3 (B), the light alloy material 33 is punched by the shaft portion 15 and the scraps 37 fall into the lower die 31. Thereby, the tip end portion of the shaft portion 15 penetrates the light alloy material 33, and the punched hole 39 is formed in the light alloy material 33. By this punching, the material around the punching hole 39 is sandwiched between the head 13 of the rivet 11 and the lower die 31 to cause plastic flow. That is, the surrounding material is lifted into the groove 27 formed in the head 13 of the rivet 11 and comes in close contact with the periphery of the shaft 15. The rivet 11 is caulked and fixed to the light alloy member 33 by the above-described driving.

  The light alloy material 33 to which the rivets 11 are fixed by caulking is carried into the resistance spot welding apparatus 41 shown in FIG. 4A and stacked on the steel material 43. At this time, the light alloy material 33 and the steel material 43 are disposed such that the rivet 11 is positioned between the spot welding electrodes (hereinafter abbreviated as electrodes) 45 and 47. Since the shaft 15 of the rivet 11 penetrates the light alloy material 33, the plurality of projections 19 at the tip of the shaft 15 are in contact with the steel material 43.

  Then, the upper and lower electrodes 45 and 47 are made to approach each other, and the head 13 of the rivet 11 and the steel material 43 are sandwiched to apply a pressing force. Then, a spot welding current (pulse current) is applied between the electrodes 45 and 47. Thereby, as shown to FIG. 4 (B), the dissimilar-material joined body by which the rivet 11 and the steel materials 43 resistance spot-welded is obtained. In this example, since the axes of the electrodes 45 and 47 and the axis of the rivet 11 substantially coincide with each other, the current flows through the center of the axis 15 of the rivet 11 and the nugget 49 is easily formed at the center of the axis 15 .

  In FIGS. 4A and 4B, the axes of the electrodes 45 and 47 coincide with the axes of the rivet 11, but as schematically shown in FIG. 5, the axes of the electrodes 45 and 47 are, for example, P1. , P2 may be offset from the axis O of the rivet 11. In that case, in the conventional rivet, as shown in FIG. 10, the rivet 213 sandwiched between the electrodes 211 and 212 is easily inclined. As described above, when welding is performed in a state where the rivet 213 is inclined, the end of the shaft portion 219 of the rivet 213 bites into the steel material 217 and is in surface contact, and the density of the welding current decreases. Therefore, the welding nugget 225 becomes smaller.

  On the other hand, in the rivet 11 of this configuration, as shown in FIGS. 1 and 2, the plate-like head 13 is substantially rectangular (L / W> 1) in plan view, and the shaft 15 is in bottom view And has a rectangular substantially rectangular parallelepiped shape. Furthermore, the distal end surface 17 of the shaft portion 15 has a central protrusion 21 linearly extending along the rectangular parallelepiped longitudinal direction, and a plurality of side protrusions 23 juxtaposed to the central protrusion 21. As described above, by arranging a plurality of side protrusions 23 around the central protrusion 21, the arrangement region of the electrodes 45 and 47 capable of stably supporting the rivet 11 becomes wide. Therefore, even if the rivet 11 is pinched by the electrodes 45 and 47 in which the misalignment occurs, the rivet 11 does not easily tilt.

  That is, as shown in FIG. 5, even if the electrodes 45 and 47 cause misalignment in the longitudinal direction (L1 direction) or the width direction (L2 direction) of the rivet 11, or in the longitudinal direction and the width direction, The distributed arrangement of 19 prevents the rivet 11 from tilting.

  Furthermore, even if the rivet 11 is slightly inclined, the spot welding current of the electrodes 45 and 47 flows through each of the plurality of projections 19 in contact with the steel material 43 at a high current density. Therefore, a plurality of weld nuggets 49 are formed by the plurality of projections 19, and the individual weld nuggets 49 do not become small. Moreover, the welding nuggets 49 adjacent to each other gather as time passes, so that a larger welding nugget is formed.

  6 (A) is a cross-sectional view taken along the line B-B in FIG. 5, and (B) is a cross-sectional view taken along the line C-C in FIG. In either case shown in FIGS. 6A and 6B, the shaft portion 15 and the steel material 43 are melted starting from the contact portion between the protrusion 19 having the plurality of protrusions and the steel material 43, and appropriate welding strength is obtained. A weld nugget 49 of a size that provides

  In addition, the conditions generally used for joining of the same kind of materials of normal steel materials-steel materials can be applied as it is as the conditions of spot welding. In other words, although the present configuration is a dissimilar joint of light alloy material-steel material, conditions generally used for spot joining of similar steel-steel material same kind can be applied.

  It is preferable that said spot welding makes the applied pressure between a pair of electrodes 45 and 47 into the range of 1.0-5.0 kN. In addition, the interelectrode current is in the range of 5 to 15 kA, preferably in the range of 7 to 8 kA, and the current application time is 200 × t (msec) or less in relation to the thickness t (mm) of the bonding portion of the light alloy material. It is preferable to use time. The reason for making the current application time proportional to the thickness t of the light alloy material 33 is to compensate for the heat that escapes through the light alloy material 33 with high thermal conductivity that is crimped and fixed to the rivet 11 to make a spot weld nugget of a certain size This is to form 49.

  When the ratio (L / W) of the length (L) in the longitudinal direction of the rivet 11 to the length (W) in the width direction is less than 1.5, the contact area of the electrodes 45 and 47 becomes small In particular, in the case of bonding of narrow parts such as the joint part of the car roof panel and the tire drain force (the part where the molding is fitted), the area of the head 13 to which the electrodes 45 and 47 can be grounded is small. Is more likely to occur.

  On the other hand, when the ratio (L / W) exceeds 3, the weight of the rivet 11 is increased, and the weight of the joined body is increased more than necessary. In addition, since the number of rivets that can be installed per unit length decreases and the area of the weld nugget does not increase, the ratio of the formation area of the weld nugget to the shaft area of the rivet 11 decreases. As a result, the bonding strength of the bonded body is reduced.

  According to the different material joining rivet 100 of this configuration, the ground point of the electrode can be easily secured even if the electrode position at the time of spot welding varies. In addition, since a plurality of projections are formed at the tip of the shaft portion, the rivet is less likely to be inclined even if a shift (core shift) between the axis of the electrode and the axis of the rivet occurs. Even if the electrodes are misaligned during spot welding and the rivet is inclined, the projections are arranged relatively close, so the welding current is relatively narrow in the region including the adjacent projections. Flow. As a result, a reduction in current density can be suppressed, a nugget of a required size can be stably formed, and a required bonding strength can be secured.

<Modification of rivet>
Next, a modification of the rivet 11 will be described. In the following description, the description will be simplified or omitted by giving the same reference numerals to the same or corresponding members.

  FIG. 7 shows a widthwise sectional view of the rivet 11A of the first modified example. In the rivet 11 </ b> A of the present modification, a recessed portion 51 that is recessed inside the shaft portion 15 is formed on the side surface of the width direction end of the shaft portion 15. The recess 51 is a groove having a substantially semicircular cross section along the longitudinal direction of the shaft 15. The other configuration is the same as the rivet 11 described above.

  According to the rivet 11A of this modification, when the shaft portion 15 punches out the light alloy material 33, the light alloy material 33 plastically flows in the recess 51. Therefore, the light alloy material 33 is joined to the rivet 11 A only by the edge of the punched hole 39 entering the recess 51, and the light alloy material 33 does not come out of the recess 51.

  FIG. 8 shows a widthwise sectional view of the rivet 11B of the second modified example. In the rivet 11B of the present modification, the protrusion 19 formed on the tip end surface 17 of the shaft portion 15 is composed of a plurality of protrusions 24 whose number is larger than the total number of central protrusions 21 and lateral protrusions 23 of the rivet 11 described above. . Therefore, the distance between the adjacent protrusions 24 through which the welding current flows can be reduced, and a decrease in the current density does not occur, and a welding nugget of a predetermined size can be formed more stably.

  As described above, the form of the projection is not particularly limited. As shown in FIG. 9A, it may be a rivet 11C in which a plurality of rows of protrusions 24 are arranged in parallel in the width direction on the tip end surface of the shaft portion 15. Moreover, as shown to FIG. 9 (B), the rivet 11D by which the projection part 24 of multiple rows was arranged in parallel by the longitudinal direction may be sufficient. Furthermore, as shown in FIG. 9 (C), it may be a rivet 11E in which a plurality of rows of protrusions 24 are juxtaposed along an oblique direction inclined from the longitudinal direction.

  Further, the rivet 11F is not limited to the linear protrusion 24 described above, but is a rivet 11F having a knurled protrusion 26 (a ridge line around the recess 28) having a minute concavo-convex pattern as shown in FIG. 9D. May be The knurled shape includes, for example, the shape defined in JIS B 0951 or the like.

  Also by the rivets 11C, 11D, 11E, and 11F having the above-described shapes, the same effects as in the case where the rivets 11, 11A, and 11B are used can be obtained. That is, since the welding current can reduce the distance between the plurality of adjacent protrusions 24 and 26 in contact with the steel material 43 in both the width direction and the longitudinal direction, the current density does not decrease. As a result, as in the case of the rivets 11, 11A and 11B, a weld nugget having a size that can obtain an appropriate weld strength is formed.

  At that time, it is preferable to set the distance between adjacent projections to W, and the diameter d of the contact area of the electrodes 45 and 47 (see FIG. 4A) to a dimension such that W> d. Preferred.

11, 11A, 11B, 11C, 11D, 11E, 11F Rivets (Rivets for joining dissimilar materials)
13 head 15 axis portion 17 tip surface 19 protrusion 21 central protrusion 23 side protrusion 24 protrusion 26 protrusion 27 groove 33 light alloy material 43 steel 45, 47 spot welding electrode

Claims (4)

For joining dissimilar metals made of steel having a plate-shaped head fixed to a light alloy material by caulking and a shaft extending from the head and penetrating the light alloy material and having its tip spot-welded to a steel material It is a rivet,
The head has a rectangular plane having a ratio (L / W) of length (L) to width (W) of 1.5 or more and 3 or less,
The shaft portion is rectangular in a bottom view,
A linear groove is formed in the longitudinal direction at root portions on both sides of the shaft in the head,
A plurality of linearly extending protrusions formed in parallel in a diagonal direction inclined from the width direction, the longitudinal direction, or the longitudinal direction of the axial portion are formed on the tip end surface of the axial portion. Rivets. For joining dissimilar metals made of steel having a plate-shaped head fixed to a light alloy material by caulking and a shaft extending from the head and penetrating the light alloy material and having its tip spot-welded to a steel material It is a rivet,
The head is a rectangular plane having a ratio (L / W) of length (L) to width (W) of 1.5 or more and 3 or less,
The shaft portion is rectangular in a bottom view,
A linear groove is formed in the longitudinal direction at root portions on both sides of the shaft in the head,
A knurled protrusion is formed at the tip of the shaft, and the rivet for dissimilar material joining is characterized in that A rivet for dissimilar material joining according to claim 1 or claim 2 ;
The light alloy material and the steel material joined respectively by the different material joining rivet;
What is claimed is: 1. A dissimilar material joint comprising: It is a dissimilar-materials joining method which joins the said steel materials and the said light alloy material using the rivet for dissimilar-materials joining according to the said Claim 1 or 2, Comprising:
Driving the light alloy material from the tip end side of the shaft of the different material bonding rivet, and caulking and fixing the different material bonding rivet to the light alloy material;
The rivet for dissimilar material joining crimped and fixed to the light alloy material is superimposed on the steel material, the head of the rivet for dissimilar material bonding and the steel material are sandwiched by a pair of electrodes, and the dissimilar material is joined using the pair of electrodes. Applying a current to the electrode while pressing a rivet and the steel material, and spot welding the shaft portion of the rivet for joining different materials and the steel material;
A dissimilar metal bonding method characterized in that the method comprises:

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