JP7389315B2 - Lap joint structure and automobile frame parts - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lap joint structure and an automobile frame component.

In order to improve collision safety and fuel efficiency at the same time, the application of high-strength steel plates to structural members that form the framework of monocoque bodies that make up automobile bodies (hereinafter referred to as "automotive structural members") is expanding. There is. Currently, high-tensile steel plates with a tensile strength of 980 MPa class are used for structural members for automobiles. Further, by using a hot stamping method in which quenching is performed at the same time as press forming, high-strength structural members for automobiles with a tensile strength of 1500 MPa or more are being manufactured. According to the hot stamping method, there are fewer problems with dimensional accuracy after forming because the steel sheet is press-formed in a high-temperature, soft state. It has the great advantage of being superior in quality.

However, in spot welded joints that include steel plates with a tensile strength of 780 MPa or more, the toughness of the nugget decreases, and stress in the peeling direction concentrates at the nugget ends, so the tensile strength of the steel plate increases. However, there is a problem that the cross tensile strength (CTS) does not increase or decreases.

One technique for solving this problem is a technique of mechanically joining a plurality of metal plates using mechanical joining means such as rivets and screws without melting the base material. By using this technology, it is possible to manufacture automobile parts with higher strength and reliability than conventional ones.

Furthermore, in automobile bodies and the like, combinations of different materials such as steel plates and aluminum plates, or steel plates and carbon fiber reinforced plastic (CFRP) plates are sometimes joined together for the purpose of reducing weight. In this way, when the materials to be combined have different physical properties such as melting points and coefficients of linear expansion, they are fastened and joined using mechanical joining means, as described in Patent Documents 1 and 2, for example. . Furthermore, for aluminum plates with low electrical resistance, friction stir spot welding is sometimes used instead of resistance spot welding. Hereinafter, the mechanical joining means and the friction stir point joining means may be collectively referred to as non-melting joining means.

In providing this non-melting bonding means to the lap bonding structure, it is inevitably necessary to provide holes in the plate members. For example, when the overlapped portions of a plurality of stacked plate members are joined at the joint portion using a mechanical joining means such as a blind rivet, a hole through which the rivet is inserted is formed in the joint portion of the plate members. Further, when the overlapped portions are point-joined by friction welding means, a hole remains at the joint portion of the plate member on the rotary tool side due to the press-fit trace of the probe at the tip of the rotary tool.

According to the inventor's study, in a lap joint member in which the overlapped parts are joined by mechanical joining means or friction joining means, when the entire overlap joint member is subjected to tensile deformation, strain is concentrated in the hole formed in the joint part. Therefore, a problem arose in which the plate member broke due to small deformation starting from the hole. In the prior art such as Patent Documents 1 and 2, no consideration has been given to this problem.

Japanese Patent Application Publication No. 2000-272541 Japanese Patent Application Publication No. 2005-119577

In a stacked joint structure in which overlapped parts formed by stacking a plurality of plate members are joined by a non-melting joining means, the plate members may break starting from a hole formed in the non-melting joining part. The present invention suppresses the breakage of a plate member starting from a hole formed in a non-melting joint of the plate member, thereby increasing the elongation (amount of strain) until the plate member breaks. The purpose is to provide a joint structure.

The gist of the present invention is as follows.
(1) The overlap joint structure according to one aspect of the present invention is configured by a plurality of overlapping plate members and a mechanical joining means or a friction stir point joining means provided at the overlapping portion of the plurality of plate members. a plurality of joints, each of which has a hole through which the mechanical joining means is inserted or a hole formed by friction stir point welding, and one of the plurality of plate members In one or more sheets, a hard part is provided around the hole, and the hard part is a part of the plate member and is provided over the entire thickness direction of the plate member. and the hole passes through one or more of the plurality of plate members .
(2) In the lap joint structure described in (1) above, the shortest distance D between the edge of the hole and the edge of the hard part around the hole, the diameter K of the hole, and the Vickers distance of the hard part The hardness H1 and the Vickers hardness H2 of the plate member provided with the hard portion may satisfy Expression 1.
D≧K×H2/{2×(H1-H2)} (Formula 1)
(3) In the overlapping joint structure described in (1) or (2) above, the distance d between the plurality of hard parts and the diameter K of the hole may satisfy Expression 2.
d≧2×K (Formula 2)
( 4 ) In the lap joint structure according to any one of (1) to ( 3 ) above, the plate member provided with the hard portion may be a steel plate having a tensile strength of 1180 MPa or less.
( 5 ) In the lap joint structure according to any one of (1) to ( 4 ) above, the hard portion is provided on the main plate member having the largest product of plate thickness and tensile strength. .
( 6 ) An automobile frame component according to another aspect of the present invention has the lap joint structure according to any one of (1) to ( 5 ) above.
( 7 ) The automobile frame component described in ( 6 ) above may be an A pillar, a B pillar, a side sill, a floor member, a bumper, a front side member, a rear side member, a battery frame, or a roof rail.

According to the present invention, it is possible to suppress the breakage of the plate member starting from the hole formed in the non-melting joint of the plate member, thereby increasing the elongation (amount of strain) until the plate member breaks. It is possible to provide a layered joint structure.

FIG. 2 is a perspective view of a stacked joint structure according to the present embodiment. FIG. 3 is a cross-sectional view of a joint. FIG. 3 is a conceptual diagram of mechanical joining means formed by resistance element welding. FIG. 3 is a conceptual diagram of mechanical joining means formed by resistance element welding. FIG. 3 is a conceptual diagram of friction stir point joining means formed by friction stir point joining. FIG. 3 is a diagram schematically illustrating a method for identifying a hard part. It is a schematic diagram showing the shortest distance D between the edge of the hole and the edge of the hard part around the hole, the diameter K of the hole, and the distance d between the hard parts. It is a perspective view which illustrates the variation of the shape of a hard part. It is a perspective view which illustrates the variation of the shape of a hard part. It is a perspective view which illustrates the variation of the shape of a hard part. It is a perspective view which illustrates the variation of the shape of a hard part. FIG. 1 is a perspective view of a B-pillar that is an automobile frame component according to the present embodiment. 9 is a sectional view taken along line IX-IX of the B-pillar in FIG. 8. FIG. FIG. 2 is a perspective view of an A-pillar and a roof rail, which are examples of automobile frame parts according to the present embodiment. 11 is a sectional view taken along line XI-XI of the roof rail in FIG. 10. FIG. FIG. 2 is a perspective view of a hinge reinforcement of a B-pillar, which is an example of an automobile frame component according to the present embodiment. FIG. 3 is a plan view and a side view of a test piece simulating a conventional lap joint structure. FIG. 2 is a plan view and a side view of a test piece simulating the lap joint structure of the present invention. 14 is a photograph of the test piece of FIG. 13 after a tensile test.

The present inventors have solved the problem of suppressing the breakage of the plate members starting from the holes formed in the joint parts when the overlapped parts formed by stacking a plurality of plate members are joined by non-melting joining means. We have repeatedly investigated methods for providing a stacked joint structure for stacked members that can be used. As a result, the present inventors came up with the idea that it would be better to provide a means for dispersing strain so that strain would not be concentrated at the end of the hole formed in the joint. The inventors have also discovered that by forming a hard portion around the hole in the plate member, it is possible to prevent strain caused by a tensile load from concentrating on the hole. The lap joint structure based on this knowledge suppresses fractures originating from holes and improves its elongation.

Hereinafter, the stacked joint structure 1 according to the present embodiment will be described with reference to the drawings as appropriate. In addition, although the plate member 11 which has the flange 12 is shown in the figure as an example of the overlap joint structure 1, the overlap joint structure 1 according to this embodiment may not include the flange 12. Further, although the stacked joint structure according to the present embodiment will be described while illustrating a configuration in which the number of plate members 11 is two or three in the drawings, the number of plate members 11 may be four or more.

A stacked joint structure 1 according to an embodiment of the present invention obtained from the above findings includes a plurality of stacked plate members 11 and a stacked portion of the plate members 11, as shown in FIG. , a plurality of joint parts 13 (not shown in FIG. 1) configured by mechanical joining means or friction stir point joining means, and each of the plurality of joint parts 13 has a hole 131 through which the mechanical joining means is inserted; Alternatively, it has a hole 131 formed by friction stir spot welding, and a hard portion 14 is provided around the hole 131 in one or more of the plurality of plate members 11. Further, although the overlapping portion in FIG. 1 is the flange portion 12, the flange portion 12 is not essential as described above.

(1) Plate member 11
The material of the plate member 11 is not particularly limited. The plate member 11 is, for example, a metal plate such as a resin plate, a CFRP (Carbon Fiber Reinforced Plastic) plate, an aluminum plate, an aluminum alloy plate, a stainless steel plate, a titanium plate, or a steel plate. The plate member 11 may be provided with a surface treatment layer such as a coating film or plating. Although the overlapping joint structure according to this embodiment is constructed by stacking a plurality of plate members 11, the plurality of plate members 11 may be made of the same material or may be made of different materials. The thickness and mechanical strength (tensile strength, hardness, etc.) of the plate member 11 are not particularly limited either. For example, when the plate member 11 is a steel plate, the thickness of the plate member 11 may be, for example, 0.5 to 2.6 mm. When the plate member 11 is a CFRP plate, the thickness of the plate member 11 may be, for example, 0.3 to 4.0 mm. The thickness and mechanical strength of the plurality of plate members 11 may be the same or may be different.

Note that, among the plurality of plate members 11 constituting this structure, the one having the largest influence on the mechanical strength of the overlapped structure is the one with the largest product of plate thickness and tensile strength. In the lap joint structure according to the present embodiment, the plate member 11 having the largest product of plate thickness and tensile strength is referred to as the main plate member, and the other plate members 11 are referred to as sub-plate members. When the lap joint structure has two or more plate members 11 with the same product of plate thickness and tensile strength, and the product of these plate thicknesses and tensile strength is the largest among the plurality of plate members 11, Both of these can be considered main plate members.

The most suitable example of the plate member 11 is a steel plate having a tensile strength of 1180 MPa or less. By subjecting such a steel plate to local hardening treatment such as laser irradiation, a hard portion 14, which will be described later, can be easily formed. On the other hand, the plate member 11 may be made of a steel plate having a tensile strength of more than 1180 MPa.

When the plate member 11 is a steel plate, the steel plate may be a non-plated steel plate whose surface is not plated, and may be galvanized by alloying hot-dip galvanizing (GA plating), hot-dip galvanizing (GI plating), or electrogalvanizing (EG plating). ), Zn-Al plating, Zn-Al-Mg plating, Zn-Mg plating, or other zinc-based plating, or may be an aluminum-plated steel sheet. The plate member 11 may be a steel plate coated with chromate, resin, or the like. When the plate member 11 is a hot-stamped material, the plate member 11 is made of a non-plated steel plate, aluminum plating, an intermetallic compound of iron and aluminum, or a composite layer composed of an iron-zinc solid solution layer and a zinc oxide layer. It may be a coated steel sheet or a steel sheet coated with a composite layer consisting of a solid solution layer of iron-zinc-nickel and a zinc oxide layer.

According to the mechanical joining means described later, it is also possible to join plate members 11 that are not suitable for welding. For example, mechanical joining means can also be applied to the overlap joint structure 1 in which a plurality of aluminum materials are combined, the overlap joint structure 1 in which aluminum materials and steel materials are combined, and the like. Furthermore, mechanical joining means can also be applied to the stacked joint structure 1 using CFRP material instead of metal plates. It is also possible to join materials that are not compatible with welding by the friction stir point joining means described below. For example, the friction stir point welding means can also be applied to a lap joint structure 1 that combines a plurality of aluminum materials, a lap joint structure 1 that combines aluminum materials and steel materials, and the like. For the above reasons, the material of the plate member 11 is not particularly limited.

(2) Joint part 13 and hole 131
The plurality of plate members 11 are partially or entirely overlapped, and are joined to each other at the overlapped portions. The joining portion 13 includes non-melting joining means, ie, mechanical joining means 132, friction stir point joining means 133, and the like.

Mechanical joining means 132 are, for example, blind rivets, self-piercing rivets (SPR), hollow rivets, flat rivets, drill screws, bolts, EJOWELD®, FDS®, and the like. According to these, the plate members 11 are joined by cold or hot plastic working. The plate members 11 may be joined by a combination of these mechanical joining means and electrical heating and heating. Mechanical joining means 132 include those that penetrate all of the stacked metal plate members 11, such as blind rivets, and those that do not penetrate a portion of the stacked metal plate members 11, such as self-piercing rivets. However, any of them can be used in the overlapping joint structure 1 according to the present embodiment. In the example of the joint 13 shown in FIG. 2, the mechanical joint means 132 is comprised of a rivet.

As the mechanical joining means 132, resistance element welding (REW) may be used. As shown in FIG. 3A, this REW includes a plate member 11 (for example, an aluminum alloy plate) in which a hole 131 penetrating through the plate is formed and another plate member 11 (for example, a steel plate such as boron steel). The mechanical joining means 132, which is a steel flanged rivet, is inserted into the hole 131, and the electrodes X are used to sandwich the two plate members 11 (see FIG. 3A). This is a joining means that melts the contact portion between the tip portion of the mechanical joining means 132 and the plate member 11 by applying current to the two plate members 11 at a current value of , thereby forming a nugget 132' (FIG. 3B ). In this way, although REW partially utilizes melt-joining means, it is essentially a joining means that utilizes a mechanical element called a flanged rivet, so such joining means are also mechanical joining means. 132, it can be suitably used in the present invention.

When joining the plate members 11 using the mechanical joining means 132, it is necessary to provide a hole 131 in the plate member 11 through which the mechanical joining means 132 is inserted. That is, the joint portion 13 constituted by the mechanical joining means 132 has a hole 131 through which the mechanical joining means 132 is inserted. The hole 131 into which the mechanical joining means 132 is inserted may or may not penetrate the plate member 11.

The friction stir point welding means will be explained. Friction stir spot welding (FSSW) is, as shown in Fig. 4, a rotating tool Y that is relatively harder than the base material, which is press-fitted into the base material while rotating, without melting the base material. It is a type of solid phase joining. In friction stir spot welding, the deformation resistance of the plate member 11 is reduced by frictional heat generated by the rotation of the rotary tool Y, and the plate member 11 around the rotary tool Y is made to plastically flow and stirred by the movement of the rotary tool Y. (See Figure 4(B)). The rotary tool Y used in these series of steps usually has a probe with a threaded tip. When the rotary tool is press-fitted into the plate member 11, friction stir spot welding is performed, and then the rotary tool Y is pulled out from the base material, there will inevitably be press-fit marks of the probe on the plate member 11 into which the rotary tool Y was press-fitted. occurs (see Figure 4(C)). That is, the joint formed by the friction stir point joining means has a hole 131 which is a press-fit trace of the probe. The stacked joint structure 1 according to this embodiment is preferably applied when a hole having a depth of 80% or more of the plate thickness is formed by press-fitting a probe.

Note that it is not prohibited to combine these non-melting bonding means with other bonding means (for example, resin, etc.). For example, an adhesive (for example, an epoxy resin adhesive, etc.) may be interposed between the overlapping surfaces, and bonding using the adhesive may be used in combination with non-melting bonding means. A sealing resin (sealer, electrodeposition coating) may be interposed between the overlapping surfaces to waterproof or insulate the seam. It is a preferable form of the overlap joint structure 1 according to the present embodiment to interpose a structural adhesive, an impact-resistant adhesive, etc. on the overlapping surfaces and use adhesive joining together with non-melting joining means. be. In particular, in the case of a structural member made of a combination of aluminum and steel, it is preferable to use a resin, adhesive, etc. that has a sealing function that can provide electrical insulation, and a non-melting bonding means.

Although the position of the joint part 13 is not particularly limited, by separating the position of the hole 131 formed in the joint part 13 from the end of the plate member 11, the possibility of breakage starting from the hole 131 can be further suppressed. can. For example, it is preferable that the shortest distance L between the end of the hole 131 and the end of the plate member 11 and the diameter K of the hole 131 satisfy the following formula.
L≧0.8K

The pitch of the joints 13 (the distance between adjacent joints 13) is also not particularly limited. The pitch may be appropriately set depending on the structure to which the overlapping joint structure 1 is applied and the application site. When the overlapping joint structure 1 is applied to automobile parts, the pitch of the joint portions 13 may be approximately 20 mm to 100 mm, for example.

In addition, in the stacked joint structure 1 according to the present embodiment, the hole 131 is not limited to a hole that penetrates the plate member 11 (through hole), but also a hole that does not penetrate the plate member 11 (blind hole), or a hole that has a step on the inner surface. It may be a hole (stepped hole), a hole with a conical inner surface (tapered hole), a hole with a threaded inner surface (female threaded hole), or the like. Moreover, the hole 131 may be provided in either the main plate member or the sub-plate member.

(3) Hard part 14
As described above, in the lap joint member 1 in which the overlapped portions are joined by the mechanical joining means 132 or the friction stir point joining means, when the entire overlap joint member 1 is subjected to tensile deformation, the hole formed in the joint portion 13 If the strain concentrates on the hole 131, there is a possibility that the plate member 11 will break starting from the hole 131. Therefore, the present inventors studied means for dispersing strain so that the strain would not be concentrated at the end of the hole 131 formed in the joint portion 13. As a result, the present inventors found that by forming the hard portion 14 around the hole 131 of the plate member 11, it is possible to prevent strain caused by a tensile load from concentrating on the hole 131.

Based on the above findings, in the stacked joint structure 1 according to the present embodiment, the hard portion 14 is provided around the hole 131 in one or more of the plurality of plate members 11. The hard portion 14 is a region having a Vickers hardness that is 20% or more higher than the Vickers hardness H2 of the plate member 11 on which the hard portion 14 is provided. An example of means for identifying the hard portion 15 is shown in FIG. FIG. 5 is a plan view of the hole 131 of the joint portion 13. By performing Vickers hardness measurement, for example, in a grid pattern around the joint portion 13 (hole 131), a Vickers hardness that is 20% or more higher than the Vickers hardness H2 of the plate member 11 on which the hard portion 14 is provided is detected. It is possible to obtain measurement points α and other measurement points β. The boundary between the set of measurement points α and the set of measurement points β is the outer edge of the hard portion 14.

In order to identify the hard portion 14, it is necessary to measure the Vickers hardness of the plate member 11. It is recommended to measure Vickers hardness using a Vickers hardness meter. The measurement load at the time of Vickers hardness measurement may be appropriately selected depending on the material of the plate member 11. As is clear from the above definition, whether or not a given region of the plate member 11 corresponds to the hard portion 15 is determined based on the relative value between the Vickers hardness of the plate member 11 and the Vickers hardness of the region. It will be done. Therefore, if the Vickers hardness of the plate member 11 and the region is measured with the same measurement load, it is possible to determine whether or not the region corresponds to the hard part 15 without being affected by the measurement load. can. When determining whether or not the lap joint structure 1 satisfies Equations 1 and 2 described later, for the same reason, the measurement load at the time of Vickers hardness measurement can be selected as appropriate depending on the material of the plate member 11. good.

Although the hard portion 14 needs to be provided on one or more of the plurality of plate members 11 constituting the overlapping joint structure 1, it can be appropriately selected on which plate member 11 the hard portion 14 is arranged. Preferably, the hard portion 14 is provided on the main plate member. As described above, the main plate member is the member that most affects the mechanical properties of the lap joint structure 1, so by providing the hard portion 14 on the main plate member, its stress relaxation effect can be maximized. Preferably, the hard portion 14 is provided in the plate member 11 in which the hole 131 is present. Hereinafter, the overlap joint structure 1 according to the present embodiment will be explained based on a configuration in which the hard portion 14 is provided in a main plate member having a hole 131. However, the hard portion 14 may be provided on the sub-plate member, or may be provided on the plate member 11 that does not have the hole 131.

Although the size and shape of the hard part 14 are not particularly limited, for example, the shortest distance D between the edge of the hole 131 and the edge of the hard part 14 around the hole 131, the diameter K of the hole 131, the Vickers diameter of the hard part 14, etc. It is preferable to determine the size and shape of the hard part 14 so that the hardness H1 and the Vickers hardness H2 of the plate member 11 provided with the hard part 14 satisfy the following formula 1.
D≧K×H2/{2×(H1-H2)} (Formula 1)
When stress is applied in the direction in which the holes are lined up, the conditions under which deformation does not easily occur in the hard part containing the holes can be roughly expressed by the following equation.
2×D×H1≧(2×D+K)×H2
By rearranging this formula with respect to D, (Formula 1) is obtained.

FIG. 6 shows "the shortest distance D between the edge of the hole 131 and the edge of the hard part 14 around the hole 131." The larger the value of D, the stronger the reinforcement effect of the hole 131 due to hardening. The means for specifying the edge of the hole 131 is as described above. In addition, when the hard part 14 is bent as shown in FIG. 7B, the distance between the edge of the hole 131 and the edge of the hard part is a value measured along the bent part of the hard part.

When the hole 131 is cylindrical, the diameter K of the hole 131 is the diameter of the hole 131 when the plate member 11 is viewed from above. If the hole 131 has a non-cylindrical shape, such as a conical shape, the diameter of a cylinder having the same volume and depth as the actual volume and the actual depth of the hole 131 is considered to be the diameter K of the hole 131. . If the shape of the hole 131 in plan view is not a circle, the equivalent circle diameter is regarded as the diameter K of the hole 131. When the hole 131 is a female threaded hole, the diameter of the wider one of the uneven pitches is regarded as the diameter K of the hole 131.

As shown in FIG. 5, the Vickers hardness H1 of the hard part 14 is the largest value for the hard part 14 to 3 among the plurality of Vickers hardness values obtained by measuring the Vickers hardness of the hard part 14. It is the average value of the largest value. However, the area corresponding to the friction stir point welding means 133 is ignored when measuring the Vickers hardness H1 of the hard part 14. As mentioned above, the hard part 14 is defined as a region having a Vickers hardness that is 20% or more higher than the Vickers hardness H2 of the plate member 11 on which the hard part 14 is provided. The quality is not necessarily constant. Therefore, the Vickers hardness of a particularly hard part of the hard part 14 is defined as the Vickers hardness H1 of the hard part 14.

The Vickers hardness H2 of the plate member 11 is the Vickers hardness of a region other than the joint portion 13 and the hard portion 14 of the plate member 11 provided with the hard portion 14. The average value of the Vickers hardness measured at at least three points within a region sufficiently distant from the hole 131 is regarded as the Vickers hardness H2 of the plate member 11.

In addition, in measuring H1 and H2, the measurement load at the time of Vickers hardness measurement may be appropriately selected according to the material of the plate member 11. Equation 1 determines the lower limit value of D based on the relative ratio of H1 and H2. Therefore, by measuring H1 and H2 with the same measurement load, it is possible to evaluate whether the hard part 14 satisfies Equation 1 without being affected by the measurement load. This also applies to Equations 1' and 1'', which will be described later.

The hard part 14 that satisfies Equation 1 is sufficiently large relative to the diameter K of the hole 131, so that when stress is applied to the lap joint structure 1, it alleviates the concentration of strain and prevents the lap joint structure from breaking. 1 can be increased. In order to obtain this effect, it is preferable that the shortest distance D between the edge of the hole 131 and the edge of the hard part 14 around the hole 131 be as large as possible. For example, the shape of the hard portion 14 may be defined such that D, K, H1, and H2 satisfy the following formula 1' or formula 1''.
D≧1.2×K×H2/{2×(H1-H2)} (Formula 1')
D≧1.4×K×H2/{2×(H1-H2)} (Formula 1'')
However, if D is too large, the distance between the hard parts 14, which will be described later, will become narrower. It is preferable to determine the length L1 of the hard portion 14 while taking these factors into consideration.

The stacked joint structure 1 according to this embodiment has a plurality of joints 13. The hard portion 14 may be provided around only one of the holes 131 of the plurality of joints 13, or the hard portion 14 may be provided around two or more holes 131. When a plurality of hard parts 14 are provided in the lap welded structure 1, the positional relationship between the plurality of hard parts 14 is not particularly limited. However, for example, the distance d between the plurality of hard parts 14 and the diameter K of the hole 131 may satisfy Expression 2.
d≧2×K (Formula 2)

Note that, as shown in FIG. 6, the distance d between the plurality of hard parts 14 is defined as the distance d between a line connecting the centers of the holes 131 inside these hard parts 14 and the edges of these hard parts 14. is the distance between the intersection points. By providing a space between the hard parts 14 so as to satisfy Expression 2, the strain generated around the hole 131 can be efficiently distributed between the hard parts 14. Therefore, by arranging the plurality of hard parts 14 so as to satisfy Expression 2, it is possible to further suppress the concentration of strain in the lap joint member 1 and further improve the elongation.

The method for manufacturing the stacked joint structure 1 according to the present embodiment, particularly the method for forming the hard portion 14, is not particularly limited, and can be appropriately selected depending on the material of the plate member 11. If the plate member 11 is made of a steel plate with a tensile strength of 1180 MPa or less, whose strength can be improved by hardening, the hard part can be strengthened by local hardening treatment such as laser irradiation, high-frequency heating, and electrical heating. 14 can be easily formed. When the plate member 11 is made of an aluminum plate, an aluminum alloy plate, etc. whose strength can be improved by work hardening, the hard part 14 can be easily strengthened by locally performing forging, shot blasting, etc. can be formed into

The hard portion 14 may be formed before or after the plate members 11 are joined. For example, when the plate member 11 is a steel plate having a tensile strength of 1180 MPa or less, it is preferable to form the hard portion 14 after the plate member 11 is joined. Thereby, a hole for inserting the mechanical joining means can be easily formed. On the other hand, if it is necessary to use a hardening method that is difficult to apply to the plurality of joined plate members 11, the hard portion 14 may be formed before joining the plate members 11. In this way, the timing for forming the hard portion 14 can be flexibly selected depending on the material of the plate member 11 and the coin method of the plate member 11.

A specific example of the overlapping joint structure 1 according to the present embodiment described above will be described below with reference to FIGS. 7A to 7D. 7A to 7D, the plate members 11 have a bent portion and a flange portion 12, the plate members 11 are overlapped at the flange portion 12, and are joined by a joint portion 13 (not shown in FIGS. 7A to 7D). Various overlap joint structures 1 are shown below. In either example, the hard part 14 is provided around the hole 131 of the joint part 13, but the shape of the hard part 14 can be varied.

FIG. 7A shows an example in which the hard part 14 has a rectangular shape along the end of the flange part 12 and is provided only inside the flange part 12.

FIG. 7B is an example in which the hard part 14 has a rectangular shape along the edge of the flange part 12 and extends beyond the bent part of the plate member 11. Specifically, in the lap joint structure 1 illustrated in FIG. 7B, the hard portion 14 extends not only inside the flange portion 12 but also beyond the bent portion to the outside of the flange portion 12. The hard portion 14 also extends to the end of the flange portion 12.

FIG. 7C is an example in which the hard part 14 has a shape that widens from the bent part toward the end of the flange part 12. FIG. 7D shows an example in which the hard portion 14 has a rounded rectangular shape. In this case, in order to find the distance d between the hard parts 14, measure the distance between the two intersections of the line connecting the centers of the holes 131 inside the hard parts 14 and the edges of these hard parts 14. do it.

Note that in the overlap joint structure 1 according to the present embodiment, it is not necessary to provide the hard portion 14 around all the holes 131. This is because the ease with which deformation occurs is not necessarily uniform in the overlap joint structure 1. For example, the hard portion 14 may be provided only at locations where deformation is particularly likely to occur and strain concentration in the hole 131 is feared, and the hard portion 14 may not be provided at other locations. That is, the overlap joint structure 1 in which the hard portion 14 is provided only between some of the holes 131 also corresponds to the overlap joint structure 1 according to the present embodiment.

The application of the overlap joint structure 1 according to this embodiment is not particularly limited. One of the preferred uses of the lap joint structure 1 is automobile parts, especially automobile frame parts, which are made up of a plurality of joined steel plates. Since the automobile frame parts are composed of high-strength steel plates containing martensite, the lap joint structure 1 according to the present embodiment can be easily applied, and in this case, the remarkable effect of improving the collision safety of the automobile is possible. Effects can be obtained. On the other hand, it is possible to apply the lap joint structure 1 according to this embodiment to any plate member 11 that is joined by the mechanical joining means 132 and/or the friction stir point joining means. For example, the lap joint structure 1 according to the present embodiment can be applied to bridge members joined by rivets or high-strength bolts, and aluminum railway vehicle structures joined by friction stir point welding, thereby suppressing breakage. is considered possible. It is also possible to apply the stacked joint structure 1 according to the present embodiment to household appliances and fixtures such as architectural fittings, beams, link members, simple warehouses, furniture, refrigerators, televisions, copy machines, and outdoor cooler units.

Next, an automobile frame component according to another aspect of the present invention will be described. The automobile frame component according to the present embodiment is an automobile frame component having the lap joint structure 1 according to the present embodiment. This automobile frame part is, for example, an A-pillar, a B-pillar, a side sill, a bumper, a floor member, a front side member, a rear side member, or a roof rail. Hereinafter, an example of the automobile frame part according to this embodiment will be explained.

FIG. 8 is a perspective view of a B-pillar 2, which is an example of an automobile frame component according to this embodiment. In this figure, the side panel outer is omitted. The B-pillar 2 in FIG. 8 has a mechanical joint 13 (not shown) having a hole 131 and a hard part 14 provided around the hole 131. However, no hard portion is provided around some of the holes 131 (areas surrounded by dotted lines in FIG. 8). This is because the amount of distortion during a side collision of the vehicle body varies depending on the part of the B-pillar, and it is not necessarily necessary to provide a hard part in parts where the amount of distortion is small and where breakage from the hole is less likely to occur during a collision. Depends on the reason.

FIG. 9 is a sectional view taken along line IX-IX of the B-pillar 2 in FIG. The B-pillar 2 is composed of a B-pillar inner 22 made of a normal steel plate, a B-pillar reinforcement 21 made of a high-strength steel plate, and a side panel outer 23 made of aluminum or mild steel. These correspond to the plate member 11, and in particular, the B pillar reinforcement 21 corresponds to the main plate member. The B-pillar reinforcement 21, the B-pillar inner 22, and the side panel outer 23 are joined at both ends, and the B-pillar reinforcement 21, which corresponds to the main plate member, is provided with a hard portion 14.

FIG. 10 is a perspective view of an A-pillar 3 and a roof rail 4, which are examples of automobile frame parts according to this embodiment. Also in the part shown in FIG. 10, the hard portion 14 is provided only around some of the holes 131.

FIG. 11 is a sectional view taken along line XI-XI of the roof rail 4 shown in FIG. This automobile frame component is composed of a roof rail inner 42 made of a high-strength steel plate, a roof rail outer reinforcement 41 made of a high-strength steel plate, and a side panel outer 43 made of aluminum or mild steel. These correspond to the plate member 11, and especially the roof rail outer reinforcement 41 corresponds to the main plate member. The roof rail inner 42, the roof rail outer reinforcement 41, and the side panel outer 43 are joined at both ends, and the roof rail outer reinforcement 41, which corresponds to the main plate member, is provided with a hard portion 14.

FIG. 12 is a perspective view of the hinge reinforcement 5 of the B-pillar, which is an example of the automobile frame component according to the present embodiment. In this automobile frame part, a hat-shaped member 52 and a high-strength steel plate 51 arranged along the inside of the hat-shaped member are joined by a joint 13 that is a mechanical joining means, and the high-strength steel plate joint A hard portion 14 is provided around the hole 131 of the hole 13 . The configuration shown in FIG. 12 can also be used for the floor member.

In the description of the stacked joint structure 1 according to the present embodiment, a stacked joint structure in which a joint part is formed at the overlapped part where two or three plate members 11 are stacked is illustrated, but four or more plate members 11 may be superimposed. In addition, in the explanation of the overlap joint structure 1 according to the present embodiment, a case where a hard portion is formed in one plate member 11 or two plate members 11 out of two or three plate members 11 will be explained. However, for example, a joint part may be formed in the overlapped part of four or more (plurality) of plate members 11 to form a stacked joint structure, and in such a case, the plate member on which the hard part is formed. The number of 11 sheets can be set arbitrarily. Further, the overlapping portion formed by overlapping the plate members 11 does not need to be a flange portion. It goes without saying that the overlap joint structure according to this embodiment also includes a overlap joint structure in which plate members 11 without flanges are overlapped and joined together for the purpose of partial reinforcement or the like.

A sample shown in FIG. 13 in which neither plate member A nor B has a hard part, and a sample shown in FIG. 14 in which only plate member A has a hard part were created. Here, (A) in FIGS. 13 and 14 is a plan view of the sample (riveted), and (A) in FIGS. 13 and 14 is a side view of the sample (riveted). Note that in FIGS. 14 and 15, plate member A is a 200 mm long plate (rating interval 70 mm ). In FIGS. 14 and 15, plate member B is a plate having a width of 20 mm and a length of 80 mm, which is stacked on the parallel portion of plate member A. The distance between the edge of the hole and the score was 8 mm. The types of plate member A and plate member B are as shown in the table below.

In the sample shown in FIG. 14, the hard portion was formed by laser irradiation. The laser irradiation conditions were as follows.
・Oscillator: Semiconductor laser ・Laser output: 1.0 to 2.5kW
・Speed: 0.3~1.0m/min
・Beam shape: Rectangular (width: adjusted to 10-20mm)

And sample No. of Table 2. Tensile tests were conducted on samples Nos. 1 to 11, and their breaking strains were measured. The measurement results are shown in Table 2. Note that the shape of the sample described as "no hard part" in Table 2 was as shown in FIG. 13, and the shape of the other samples was as shown in FIG. 14.

As shown in Table 2, sample No. 1 has a lap joint structure made of plate members without a hard part. In Nos. 1 and 8, the breakage occurred starting from the hole, as shown as a breakage point Z in FIG. On the other hand, sample No. 1 has a lap joint structure including a plate member A having a hard portion. 2 to 7, and No. In No. 9 to No. 11, a break occurred from the base material, as shown as a break Z in FIG. 14. This result shows that the provision of the hard part alleviates the concentration of strain on the hole. For reference, No. 1 in which the break occurred from the hole. A photograph after the tensile test of No. 1 is shown in FIG.

In addition, as shown in Table 2, sample No. 1 has a lap joint structure composed of plate members without a hard part. In comparison with Sample No. 1 and 8, Sample No. 8 has a lap joint structure including plate member A having a hard portion. 2 to 7, and No. Nos. 9 to 11 had better breaking strain. This result shows that the elongation of the lap joint structure is improved by providing a hard part to alleviate strain concentration in the hole.

According to the present invention, when the overlapping portion formed by overlapping a plurality of plate members is joined by a non-melting joining means, the plate member is prevented from breaking starting from the hole formed in the joining portion. , it is possible to provide a lap joint structure of lap joint members that can increase elongation until breakage. For example, when the present invention is applied to an automobile, the occupant protection performance in the event of a collision can be dramatically improved. Therefore, the present invention has high industrial applicability.

1 Overlapping joint structure 11 Plate member 12 Flange part 13 Joint part 131 Hole 132 Mechanical joining means 132' Nugget 133 Friction stir point joining means 14 Hard part 2 B pillar 21 B pillar reinforcement 22 B pillar inner 23 Side panel outer 3 A pillar 4 Roof rail 41 Roof rail outer reinforcement 42 Roof rail inner 43 Side panel outer 5 Hinge reinforcement 51 High-strength steel plate 52 Hat-shaped member X Electrode Y Rotating tool

Claims (7)

A plurality of overlapping plate members,
A plurality of joints formed by mechanical joining means or friction stir point joining means provided at the overlapped portions of the plurality of plate members;
Equipped with
The plurality of joints have a hole through which the mechanical joint means is inserted, or a hole formed by friction stir point welding,
A hard part is provided around the hole in one or more of the plurality of plate members,
The hard part is a part of the plate member and is provided over the entire thickness direction of the plate member,
The stacked joint structure is characterized in that the hole passes through one or more of the plurality of plate members . the shortest distance D between the edge of the hole and the edge of the hard part around the hole;
The diameter K of the hole,
Vickers hardness H1 of the hard part; and Vickers hardness H2 of the plate member provided with the hard part.
The lap joint structure according to claim 1, wherein: satisfies formula 1.
D≧K×H2/{2×(H1-H2)} (Formula 1) The overlapping joint structure according to claim 1 or 2, wherein a distance d between the plurality of hard parts and a diameter K of the hole satisfy Expression 2.
d≧2×K (Formula 2) The lap joint structure according to any one of claims 1 to 3 , wherein the plate member provided with the hard portion is a steel plate having a tensile strength of 1180 MPa or less. The overlap joint structure according to any one of claims 1 to 4 , wherein the hard portion is provided on the main plate member having the largest product of plate thickness and tensile strength. An automobile frame component having the lap joint structure according to any one of claims 1 to 5 . The automobile frame part according to claim 6 , which is an A-pillar, a B-pillar, a side sill, a floor member, a bumper, a front side member, a rear side member, a battery frame, or a roof rail.

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