JP5605405B2 - Resistance welded joint - Google Patents

Description

The present invention relates to a resistance welding body, specifically, relates to a resistance welding joint bodies produced a plurality of metal plates which are arranged superimposed the thickness of the plate is resistance welding.

  Resistance spot welding is frequently used to assemble automobiles and other transportation machines and various industrial machines. In general structural parts, since there are a plurality of joints in one joined body, resistance spot welding is performed by appropriately using various resistance spot welding methods. In the following description, the case where the metal plate used for resistance spot welding is a steel plate is taken as an example.

  11A is an explanatory view showing spot welding, FIG. 11B is an explanatory view showing one-side spot welding, and FIG. 11C is an explanatory view showing series spot welding. is there.

  As shown in FIG. 11 (a), spot welding is performed by welding electrodes 4 and a back electrode 5 disposed opposite to each other with two steel plates 1 and 2 disposed so as to overlap each other in the thickness direction. This is performed by flowing a welding current A indicated by a solid line from the welding electrode 4 to the back electrode 5. Moreover, as shown in FIG.1 (b), while one side spot welding contact | abuts the welding electrode 9 to the steel plate 6 in the two steel plates 6 and 7 arrange | positioned by being piled up in the plate | board thickness direction, The back electrodes 10 and 10 (one or three or more back electrodes 10 may be provided differently from the illustrated example) are brought into contact with the positions different from the positions at which the welding electrodes 9 face each other, and the welding electrodes 9 are connected to the back electrodes 10 and 10. This is done by passing a welding current A. The back electrode 10 may be brought into contact with the steel plate 6 instead of the steel plate 7. Furthermore, as shown in FIG. 11 (c), in the series spot welding, the two welding electrodes 13 and 14 are separated from the steel plate 11 of the two steel plates 11 and 12 that are arranged in the thickness direction. The welding current A is made to flow from the welding electrode 13 to the welding electrode 14.

  In spot welding shown in FIG. 11 (a) and one-side spot welding shown in FIG. 11 (b), when resistance spot welding is to be performed on a place where the welding electrodes 4 and 9 are in contact, resistance is first applied in the vicinity of the joint. When other resistance welds 3 and 8 formed by spot welding exist or when the series spot welding shown in FIG. 11C is performed, the welding current A from the welding electrodes 4, 9 and 13 is increased. It is known that a reactive current B indicated by a broken line is generated which partially reaches the back electrodes 5, 10 and the welding electrode 14 through the other welded portions 3 and 8 and the steel plate 11. As the current value of the reactive current B increases, the current value of the welding current A flowing through the portion to be spot welded decreases, so that it is difficult to form and grow an appropriate nugget.

  In particular, in the one-side spot welding shown in FIG. 11 (b), since the energization path from the point to be joined to the back electrode 10 is long, the back electrode 10 hits only the steel plate 7 on the side not in contact with the welding electrode 9. Even under the circumstances, the reactive current B to the other contact point formed by the resistance spot welding, the strong contact point which is the portion including the protruding portion or the corner portion formed on the steel plates 6 and 7 is present. It is likely to occur. In addition, as shown in FIG. 11C, also in series spot welding, the welding current energized from one welding electrode 13 passes only through one steel plate 11 contacting the welding electrode 14 and passes through the other steel plate 12. Since a path leading to the other welding electrode 14 is also generated, the weldability due to the reactive current B is likely to deteriorate.

  In general, in resistance spot welding multi-point welding, it is known that the reactive current increases as the welding spot pitch becomes narrower, and the minimum weldable pitch depends on the plate thickness of the steel sheet to be welded. . For example, the standard condition indicated by the Resistance Welding Committee discloses a method of increasing the spot pitch according to the thickness of the material to be welded in order to solve the deterioration of weldability due to the generation of reactive current.

  However, in this method, due to the shape of the component, for example, when a seating surface that can be welded to one or both of the steel plates cannot be sufficiently secured, there is a possibility that a sufficient hitting pitch cannot be secured. In addition, there is a concern that the rigidity and strength of the parts will decrease in order to widen the hitting pitch.

  In addition, it is known that the reactive current is more likely to be generated as the pressure applied by resistance spot welding is smaller, and that the lower the welding current is, the greater the decrease in strength of the welded portion when reactive current is generated. It is also recommended to perform resistance spot welding, and Patent Document 1 discloses an invention relating to a method of applying a high pressure only at the initial stage of welding.

  On the other hand, with regard to welding methods that are particularly prone to reactive currents, such as single-side spot welding and series spot welding, for example, a method of performing welding by placing a conductor auxiliary in the back or very close to the welding point, or patent literature 2 discloses an invention relating to a method of performing resistance spot welding by providing a projection to a weld. In any of these inventions, the welding current is supplied to the welded portion in a concentrated manner by shortening or limiting the energization path of the welding current.

  Further, Patent Document 3 discloses an invention relating to a method of heating a steel plate by energizing a preliminary current and reducing an ineffective current by increasing the electrical resistance of the steel plate.

Japanese Patent Laid-Open No. 11-333569 JP 2005-14003 A JP 2007-14968 A

  However, the invention disclosed in Patent Document 1 is sometimes restricted by the performance of the spot welder and cannot be implemented. In addition, when welding parts with a structure in which the back electrode cannot be placed on the steel plate placed on the opposite side of the welding electrode, such as the one-side spot welding or series spot welding described above, deformation of the part by pressurization of the welding electrode In order to prevent this, the pressurizing force cannot be increased.

  In addition, in the method of performing welding by placing an electric conductor auxiliary behind or very close to the welding point, of course, the shape of the electric conductor can be set because it is greatly restricted by the shape of the parts. This can only be done for parts that have it. On the other hand, in order to carry out the invention disclosed in Patent Document 2, it is necessary to strictly manage the target position of spot welding, and it is difficult to carry out surely.

  Furthermore, in the invention disclosed in Patent Document 3, there is a concern that the productivity may be impaired due to an increase in welding time, and the shape of the component may be impaired due to the softening of the steel sheet by energization heating.

From one aspect, as illustrated in FIG. 1, discussed later (a), a plurality of metal plates are arranged superimposed to the thickness direction of the (1,2), the plurality of metal plates (1, 2) And a superposed contact portion (not shown) in which the plurality of metal plates (1, 2) are in contact with each other and are in contact with each other. The welding electrode (4) and the back electrode (5) that are arranged to face each other with the plurality of metal plates (1, 2) sandwiched therebetween are contacted, and the plurality of metal plates (1, 2) are resistance-welded. A method wherein at least one of the outermost two metal plates (1, 2) with which the welding electrode (4) or the back electrode (5) abuts is joined 3 or at least one of the overlapping contact portions (not shown), Resistance welding comprising a slit (1a, 2a) formed so as to divide at least a part of a region (25) connecting a contact electrode (4) or a portion where the back electrode (5) is provided. Is the method.

From another viewpoint, as shown in FIG. 1, discussed later (b) constituting a plurality of metal plates which are arranged superimposed to the thickness direction (6,7), the two outermost In the metal plate (6) of one of the metal plates (6, 7), the plurality of metal plates (6, 7) are joined, and the joint portion (8) having electrical conductivity or the plurality of metal plates ( 6 and 7) are in contact with each other and a welding electrode (9) is brought into contact with the vicinity of an overlapping contact portion (not shown) having electrical conductivity and the other one of the two metal plates (6 and 7). In this method, the back electrodes (10, 10) are brought into contact with the metal plate (7) at a position different from the position where the welding electrode (9) is opposed, and the plurality of metal plates (6, 7) are resistance-welded. The one metal plate (6) is at least either the joint (8) or the overlapping contact portion. And one welding electrode (9) is a resistance welding method, characterized in that it comprises a slit (6a) which is formed so as to divide at least part of the region (25) connecting the abutting portion.

These resistors welding method, superimposed contact portion, the plurality of metal plates (1, 2), the clamping portion is pressurized by a clamping means (6, 7), or a plurality of metal plates (1, 2) , (6, 7), it is exemplified that it is a portion including a protrusion or a corner formed on at least one metal plate.

From another viewpoint, as shown in FIG. 1, discussed later (c) constitute a plurality of metal plates which are arranged superimposed to the thickness direction (11, 12), the two outermost A method in which a plurality of welding electrodes (13, 14) are brought into contact with one metal plate (11) of the metal plates (11, 12) and the plurality of metal plates (11, 12) are resistance-welded. A slit formed so that one metal plate (11) divides at least a part of at least one region (25) of a plurality of regions connecting portions where the welding electrodes (13, 14) abut. (11a) It is a resistance welding method characterized by the above-mentioned.

These resistors welding method, a slit (1a, 2a, 6a, 11a) is desirably in the through hole penetrating the thickness direction of one metal plate (1,2,6,11).

The present invention, as shown in FIGS. 1 (a) and 1 (b), a plurality of metal plates are arranged superimposed the thickness of the plate (1,2), and (6,7), these a plurality of metal plates (1, 2), a contact portion superposed with electric conductivity with (6,7) are in contact, are formed in the vicinity of the I heavy mating contact portion with a plurality of metal plates (1, 2), resistance weld joining (6,7) (16), and (18), it heavy mating contact portion contact and resistance weld (16), to divide at least part of the region (25) connecting (18) The slits (1a, 2a) and (6a) formed in this way, and the overlapping contact portion is at least one metal of the plurality of metal plates (1, 2) and (6, 7) Resistance welding joints (15), (17), characterized in that they are portions including protrusions or corners formed on a plate A. Further, in this case, the resistance welds it heavy mating contact portion (16), is exemplified not more than the distance of 50mm between the (18).

Furthermore , from another point of view, as shown in FIG. 1 (c), a plurality of metal plates (11, 12) and a plurality of metal plates (11, 12) arranged in the thickness direction are arranged. A plurality of resistance welds (20, 21) to be joined and at least a part of at least one region (25) among a plurality of regions connecting two adjacent resistance welds (20, 21) are divided. It is a resistance welding joint (19) provided with the slit (11a) formed. Also in this case, it is illustrated that the distance between two adjacent resistance welds (20, 21) is 50 mm or less.

The Oite "region" in these, FIG. 1 (a), as illustrated in FIG. 1 (b), joint, defined as the outer shell of the molten portion formed as (3,8), also formed A region 25 surrounded by a line connecting resistance welds (16, 18) defined as the outer shell of the nugget to be formed, or an outer shell of a portion where the metal plates (11, 12) are in strong contact with each other due to the action of external pressure Means a region surrounded by a line connecting the resistance welds (16, 18).

The Oite "superposing contacting portion" in these plurality of metal plates (1,2), (6,7), it means a moiety having an electric conductivity as well as contact (11, 12), For example, as shown in FIGS. 6A and 6B, which will be described later, a portion where the metal plates are in contact with each other by applying an external force by the clamp device 26 or the like, for example, FIG. As shown in FIG.7 (b), the part contacted via the protrusion part formed in the metal plate and the part contacted via the corner | angular part formed in the metal plate are included. Such contact points can be confirmed by occurrence of discoloration in the metal plate due to heat generated by energization when resistance welding is performed by a normal resistance welding method without providing a slit.

Further, the Oite "near" to these, the welding electrode (4), (9), the joint (3), the reactive current flowing through the contact portion so (8) or superimposed increases from (13, 14) The range means, for example, the distance from the center of the resistance welded portion (16, 18, 20, 21) formed by the welding electrodes (4), (9), (13, 14) being 50 mm. Within the range, preferably within 30 mm. That is, when the distance between the joints (3), (8) or the overlap contact part and the center of the resistance welded part (16, 18, 20, 21) increases beyond 50 mm, the joints (3), (8 ) Or the reactive current flowing through the overlapping contact portion is reduced, and the influence of the reactive current substantially disappears, so that the distance from the center of the resistance welded portion (16, 18, 20, 21) is within 50 mm. It is desirable to form slits when there are joints or contact portions.

Further, the Oite "slit (1a, 2a, 6a, 11a)" to these, the plate thickness direction to penetrate, the outermost of the metal plate of the metal plate (1,2,6,11) (1,2 , 6, 11) means a notch or a through-hole opening at the end face, and the shape thereof is not particularly limited. In the present invention, the “slit” is formed at a position where at least one of the joint (3, 8) or the overlapping contact portion in the example shown in FIG. 1 (a) or FIG. 1 (b) and welding. It may be at least a part of the region (25) connecting the electrode (4, 9) or the back electrode (5) and the welding electrode (13, 14) in the example shown in FIG. ) May be at least a part of the region (25) connecting the portions to be installed, and is not particularly limited.

Furthermore, this Oite "slit (1a, 2a, 6a, 11a)" to the colleagues, the plurality of metal plates are arranged superimposed to (I) a plate thickness direction (1,2,6,7,11,12 ), (II) at least one center of the joint (3, 8) or the overlapping contact portion, and (4, 9) or a portion where the back electrode (5) is provided. (III) At least one center of the junction (3, 8) or the overlapping contact portion and (4, 9) or the back electrode (5) are provided. It is desirable that each of the regions (25) connecting the portions to be cut is provided so as to be divided.

  According to the present invention, welding conditions for resistance spot welding (pressure applied by welding electrodes, energization time, and welding current) even in situations where there are spot welds or parts that are partly in strong contact between the materials to be welded Without significantly changing the conventional welding conditions, the above-mentioned spot welds and parts that are in strong contact with each other while reducing the reactive current sufficiently under almost the same welding conditions as in the conventional case where reactive current does not occur In this case, good resistance spot welding can be performed in the vicinity of this, and therefore, even when the distance between the hit points of resistance spot welding is as small as 50 mm or less, for example, an appropriate nugget is surely provided, so that sufficient bonding strength is obtained. It is possible to provide a resistance welding joint having the same.

It is explanatory drawing which shows embodiment, FIG. 1 (a) shows the condition which applied this invention to the spot welding which uses a welding electrode and a back electrode, FIG.1 (b) applied this invention to the one-side spot welding. The situation is shown, and FIG. 1C is an explanatory view showing the situation where the present invention is applied to series spot welding. It is explanatory drawing which shows the evaluation method of the material of a steel plate and shape which can ensure multipoint weldability which the present inventors performed. It is explanatory drawing of the slit provided in embodiment. It is explanatory drawing of the slit provided in embodiment. It is explanatory drawing of the slit provided in embodiment. It is explanatory drawing which shows the formation position of a slit, Fig.6 (a) shows the various examples of spot welding, FIG.6 (b) shows the various examples of single side spot welding, FIG.6 (c) shows series spot welding. An example is shown. It is explanatory drawing which shows the location which steel plates contact in this way strongly in one side spot welding, Fig.7 (a) is a convex part which protrudes toward the mutual mating surface direction on the steel plate of the laminated steel plates. The case where it exists and FIG.7 (b) shows the case where the steel plate which has a ridgeline part, and a flat steel plate are joined. It is explanatory drawing which shows the steel plate which forms a slit, FIG.8 (a) shows the various steel plates in spot welding, FIG.8 (b) shows the various steel plates in one side spot welding, Furthermore, FIG.8 (c) is FIG. Various steel plates in series spot welding are shown. FIG. 9 (a) shows the situation in which slits are formed on the steel plate with the largest plate thickness and the welding electrode in contact with each other, and FIG. FIG. 9 (c) shows a situation where slits are formed in the steel plate, and FIG. 9 (c) shows a situation where slits are formed in the steel plate. It is explanatory drawing which shows collectively the shapes 1-10 of the test piece of an Example. 11A is an explanatory view showing spot welding, FIG. 11B is an explanatory view showing one-side spot welding, and FIG. 11C is an explanatory view showing series spot welding. is there.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the following description, the case where the metal plate is a steel plate is taken as an example, but it goes without saying that the metal plate can be similarly applied to other than the steel plate as long as it is a metal plate subjected to resistance spot welding. .

  FIG. 1 is an explanatory view showing the present embodiment. FIG. 1 (a) shows a situation where the present invention is applied to spot welding using a welding electrode 4 and a back electrode 5, and FIG. 1 (b) shows a one-side spot. The situation where the present invention is applied to welding is shown. Further, FIG. 1C is an explanatory diagram showing the situation where the present invention is applied to series spot welding.

  As shown in FIG. 1A, in spot welding, the steel plates 1 and 2 in a plurality (two in the illustrated example) of steel plates 1 and 2 that are arranged in a stacked manner in the thickness direction are joined and the conductivity is increased. The welding electrode 4 and the back electrode 5 that are arranged to face each other with the steel plates 1 and 2 arranged in a superimposed manner are placed in the vicinity of the spot welded portion 3 that is a joint portion having the steel plates 1 and 2 Weld.

  In addition, although not shown in figure, it replaces with the spot welding part 3, and the superposition contact part which has the electrical conductivity while the steel plates 1 and 2 contact, for example, (a) The steel plate 1 by the application of the external force by the clamping means of the steel plates 1 and 2 When the two steel plates 1 and 2 are in strong contact with each other by, for example, protruding portions or corner portions formed on the steel plates 1 and 2 and, for example, (b) the steel plates 1 and 2 are in contact with each other. It includes a portion where the steel plates 1 and 2 are discolored by heat generated by energization.

  The welding electrode 4 is a so-called electrode tip, which is a rod-shaped electrode that transmits a welding current and transmits the applied pressure to the steel plate 1. Further, the back electrode 5 is an electrode that receives the pressure applied from the welding electrode 4 and allows a welding current from the welding electrode 4 to flow. The one shown in FIG. 1A is a rod-shaped electrode, for example, a plate-shaped electrode. May be.

  In the present embodiment, the steel plate 1 against which the welding electrode 4 abuts and the steel plate 2 against which the back electrode 5 abuts the region 25 connecting the spot welded portion 3 and the portion where the welding electrode 4 or the back electrode 5 is disposed. Slits 1a and 2a formed so as to divide at least a part are provided. In the illustrated example, the slits 1a, 2a are notches that penetrate in the thickness direction of the steel plates (1, 2) and open at the end faces of the steel plates (1, 2). A through-hole penetrating in the plate thickness direction may be used, and a through-hole is rather desirable because it can minimize the decrease in strength of the steel plates 1 and 2 and can be easily processed.

  When the present invention is applied to spot welding in which the stacked steel plates 1 and 2 are sandwiched and welded between the welding electrode 4 and the back electrode 5 arranged at opposing positions, the welding current is transferred from the welding electrode 4 to the back electrode 5. As shown in FIG. 1 (a), spot welding is performed from the welding electrode 4 by forming slits 1a and 2a in one or both of the steel plates 1 and 2, as shown in FIG. It is possible to reduce the current value of the reactive current that flows to the back electrode 5 through the portion 3.

  For this reason, according to the present embodiment shown in FIG. 1 (a), without significantly changing the welding conditions of resistance spot welding (pressure applied by the welding electrode, energization time and further welding current) from the conventional welding conditions, Even in the vicinity of the spot welded part 3 or the part where the steel plates 1 and 2 are in strong contact with each other, while reducing the reactive current sufficiently under the welding conditions almost equivalent to the conventional case where the reactive current does not occur, Good resistance spot welding can be performed.

  In this way, it is possible to provide the resistance welded joint 15 including the resistance welded portion 16 in the vicinity of the spot welded portion 3 or a portion where the steel plates 1 and 2 are in strong contact with each other. This resistance welded joint 15 includes steel plates 1 and 2 that are arranged so as to be overlapped in the plate thickness direction, a spot welded portion 3 that joins the steel plates 1 and 2, and a region connecting the spot welded portion 3 and the resistance welded portion 16. Slits 1a and 2a formed so as to divide at least a part. The resistance welded joint 15 has a reactive current induced by the previously formed spot weld 3 even if the distance between the spot weld 3 and the resistance weld 16 is 50 mm or less, and even 30 mm or less. The resistance weld 16 having a healthy nugget is formed without being affected.

  Moreover, as shown in FIG.1 (b), in one side spot welding, these two steel plates 6 and 7 are joined to the steel plate 6 in the two steel plates 6 and 7 arrange | positioned by being piled up in the plate | board thickness direction. In addition, the welding electrode 9 is brought into contact with the vicinity of the spot welded portion 8 (or the superposed contact portion having electrical conductivity while being in contact with the steel plates 6 and 7), which is a joint portion having electrical conductivity, and the steel plate 7 The back electrodes 10 and 10 are brought into contact with the positions different from the positions at which the welding electrodes 9 face each other, and the two steel plates 6 and 7 are resistance-welded.

  Under the present circumstances, the steel plate 6 is provided with the slit 6a formed so that at least one part of the area | region 25 which ties the spot welding part 8 and the part which the welding electrode 9 contact | abuts may be parted. As described above, the slit 6 a is desirably a through-hole penetrating in the thickness direction of the steel plates 6 and 7.

  When the present invention is applied to one-side spot welding in which the back electrode 10 is disposed at a position different from the position where the welding electrode 9 is opposed with the stacked steel plates 6 and 7 being sandwiched, the welding electrode 9 is welded to the back electrode 10. In this embodiment, a slit 6a is formed in the steel plate 6 as shown in FIG. 1 (b). Therefore, the slit 6a is formed from the welding electrode 9 through the spot weld 3 in this embodiment. The value of the reactive current flowing through the back electrode 10 can be reduced.

  In addition, as shown in FIG. 1B, not only when the position where the welding electrode 9 faces is a space and the back electrode 10 is provided at another position, for example, insulation is provided at the position where the welding electrode 9 faces. A thing may be arrange | positioned and you may make it suppress the bending of the steel plates 6 and 7 in the case of one-side spot welding.

  In this way, a resistance welded assembly 17 including the resistance welded portion 18 in the vicinity of the spot welded portion 8 is provided. This resistance welded joint 17 includes steel plates 6 and 7 that are arranged so as to be overlapped in the plate thickness direction, a spot weld 8 that joins the steel plates 6 and 7, and a region 25 that connects the spot weld 8 and the resistance weld 18. And a slit 6a formed so as to divide at least a part thereof. This resistance welded joint 17 has a reactive current induced by the previously formed spot weld 8 even if the distance between the spot weld 8 and the resistance weld 18 is 50 mm or less, and even 30 mm or less. The resistance weld 18 having a healthy nugget is formed without being affected.

  Further, as shown in FIG. 1C, in series spot welding, the two welding electrodes 13 and 14 are brought into contact with the steel plate 11 of the two steel plates 11 and 12 arranged to be overlapped in the plate thickness direction. The steel plates 11 and 12 are resistance spot welded.

  Under the present circumstances, the steel plate 11 is provided with the slit 11a formed so that the one area | region 25 which ties the part which the welding electrodes 13 and 14 contact | abut may be parted. In addition, unlike the example shown in FIG. 1 (c), a steel plate having three or more welding electrodes in contact with the steel plate 11 of the two steel plates 11 and 12 arranged to be overlapped in the thickness direction. 11 and 12, when resistance spot welding is performed, the steel plate 11 is provided with a slit formed so as to divide at least one of a plurality of regions connecting portions where three or more welding electrodes come into contact with each other. do it.

  When the present invention is applied to series spot welding, which is a welding method in which the welding electrodes 13 and 14 are arranged only on the steel plates 11 of the stacked steel plates 11 and 12, only the steel plate 11 passes from one welding electrode 13. Thus, the reactive current flowing through the other welding electrode 14 can be reduced.

  In this way, a resistance welded joint 19 including the resistance welds 20 and 21 existing in the vicinity is provided. This resistance welding joined body 19 includes a plurality of regions connecting two steel plates 11 and 12, which are arranged to be overlapped in the thickness direction, resistance welding portions 20 and 21, and two adjacent resistance welding portions 20 and 21. 25 and a slit 11a formed so as to divide at least a part of 25.

  This resistance welded joint 19 is a resistor having a healthy nugget without being affected by reactive current during spot welding even when the distance between the resistance welds 20 and 21 is 50 mm or less, and even 30 mm or less. Welded portions 20 and 21 are formed.

  1B and 1C, the slits 6a and 11a penetrate in the thickness direction of the steel plates 6 and 11 in the same manner as the slit 2a shown in FIG. It means a notch shape or a through hole that opens in the end face, and the shape is not particularly limited. The position where the slit 6a is formed may be at least a part of the region connecting the spot welded portion 8 and the portion where the welding electrode 9 abuts, and the position where the slit 11a is formed is the welding electrode 13, There is no particular limitation as long as it is at least part of the region connecting the positions where 14 abuts.

  Furthermore, the slits 2a and 6a are provided in any of (I) the steel plates (1, 2) and (6, 7) arranged to be overlapped in the plate thickness direction, and (II) the spot welds 3, 8 And (c) the spot welded portions 3 and 8 are connected to the portions where the welding electrodes 4 and 9 are provided. Each of the regions 25 is desirably provided so as to be divided, and the slit 11a is provided in any of the steel plates (11, 12) arranged to be overlapped in the (I) plate thickness direction, (II) It is desirable to be provided so as to divide the line connecting the centers of the resistance welds 20, 21, and (c) desirably provided so as to divide all the regions 25 connecting the resistance welds 20, 21. .

Further, details of each embodiment shown in FIGS. 1A to 1C will be described in detail.
FIG. 2 is an explanatory diagram showing a method for evaluating the material and shape of a steel sheet that can ensure multi-point weldability performed by the present inventors.

  As shown in FIG. 2, the shapes of the steel plates 20 and 21 (the types of the steel plates 20 and 21, the arrangement of the resistance welds 22, the spot welds) for the combinations 20 and 21 of steel plates having several kinds of strength and thickness. Single point and multi-point spot welding and single-side spot welding were performed by changing the presence or absence of 23 and the like.

  Then, as shown in FIG. 2, the steel plates 20 and 21 joined after welding are twisted and broken, the diameter of the weld nugget 24 formed in the resistance weld 22 is measured, and single point welding is performed under the same welding conditions. “Nugget growth rate” (= nugget growth rate (%) = (nugget diameter obtained when multi-point welding is performed)) / (single By examining the nugget diameter) × 100) obtained when spot welding was performed, the materials and shapes of the steel plates 20 and 21 capable of ensuring multi-point weldability were examined.

As a result, it was found that satisfying the conditions described below is effective for ensuring multi-point weldability. In the following description, the slit 1a provided in the steel plate 1 is taken as an example, but the same applies to the slit 2a provided in the steel plate 2, the slit 6a provided in the steel plate 6, and the slit 11a provided in the steel plate 11.
(I) Formation position and shape of slit 1a (length, width, depth)
3-5 is explanatory drawing of the slit 1a provided in this Embodiment.

  As described above, in multi-point welding by resistance welding, it is known that the reactive current increases as the pitch of the welding spot becomes narrower. This is because, as the welding spot pitch is narrower, the path through which the reactive current from the position where the welding electrode 4 is contacted and joined to the spot welded portion 3 passes becomes shorter and the resistance for passage becomes smaller. It is. Needless to say, this is a phenomenon that can occur not only in multi-point welding by the same welding method, but also when there are energized joint points provided by other methods.

  As illustrated in FIG. 3A to FIG. 3C, it is obtained by connecting the point 16 to be joined and the spot welded portion 3 that are already welded in a straight line in the steel plate 1 that is the material to be welded. By eliminating a part or all of the region 25 by providing the slit 1a, the reactive current flowing to the spot weld 3 can be suppressed, thereby increasing the nugget growth rate obtained at the point 16 to be joined. .

  By forming the slit 1a, the shortest path of the reactive current on the straight line connecting the point 16 to be joined and the spot welded portion 3 can be divided. Since the current bypasses the formation portion of the slit 1a, the path through which the reactive current passes is extended, and the reactive current can be suppressed when the hitting pitch is widened.

  Regardless of where the slit 1a is formed in the region 25, the effect of suppressing the reactive current can be obtained. The width of the slit 1a (the dimension of the slit 1a in the direction connecting the point 16 to be joined and the spot welded portion 3) is not limited to a specific range, and can be set to an arbitrary width.

  As shown in FIG. 3B, the slit 1a is desirably provided at a position where the line connecting the center of the spot 16 to be joined and the center of each spot weld 3 is the shortest reactive current path.

  Moreover, as shown in FIG.3 (c), the slit 1a is a position which completely divides | segments all the area | regions 25 obtained by connecting the point 16 to be joined and the spot-welded part 3 already welded with a straight line. It is more desirable to provide in.

  The slit 1a to be formed may be a through-hole penetrating the steel plate 1 as shown in FIG. 4 (a) or a shape opened at the end of the steel plate 1 as shown in FIG. 4 (b). As shown to Fig.4 (a), it is desirable that it is a through-hole which does not open to the edge part of the steel plate 1. FIG.

  Further, in the case of spot welding shown in FIG. 1 (a), slits 1a and 2a are formed in all the stacked steel plates 1 and 2 as shown in FIGS. 5 (a) and 5 (b). Is desirable.

  6A and 6B are explanatory views showing the formation positions of the slits, FIG. 6A shows various examples of spot welding, FIG. 6B shows various examples of one-side spot welding, and FIG. An example of series spot welding is shown. In addition, the code | symbol 3-1 and 3-2 in FIG. 6 all show the spot weld part already formed, and the code | symbol 26 shows the clamp apparatus which clamps the steel plates 1 and 2. FIG.

  Hereinafter, description will be made with reference to FIG. 6A, and since FIG. 6B and FIG. 6C are the same, description thereof will be omitted.

  In FIG. 6A, the main reactive current path during multi-point welding by resistance welding is the spot 16 to be resistance-welded and the spot welded portion 3 that has already been spot-welded, which is adjacent to the point 16. It is the area | region 25 which ties the part clamped strongly by the clamp apparatus 26, and on the extension line of the line which ties the adjacent spot welded part 3, in a position far from this spot welded part 3, and another spot It is known that even if a weld exists, a decrease in the nugget growth rate due to reactive current to other spot welds hardly causes a problem. This is because the welding current energized from the welding electrode 4 has a property of preferentially flowing through a path having a low electrical resistance among paths leading to the back electrode 5.

  Therefore, in order to reduce the reactive current and increase the nugget growth rate at the point 16 to be joined, the spot weld 3 adjacent to the point 16 to be joined and the point 16 to be joined are adjacent. It is effective to cause the steel sheet 1 on the line connecting other points of concern about reactive current shunting (hereinafter referred to as “shunting concerns”) to be lost. The “adjacent point” does not mean “the most adjacent point”. Since the welding current input from the point 16 to be joined may flow in all directions, the spot weld 3 and other diversion concerns are limited to one direction as seen from the point 16 to be joined. If not, the nearest neighbor point in each direction can be a reactive current conduction path. Therefore, in this case, the slits 1a are formed in all the diversion paths that are directed not only in the direction from the point 16 to be joined toward the spot weld 3 but also in the direction toward other diversion concerns. It is desirable to do.

  Examples of the diversion concerns include, for example, a location where the steel plate is clamped by a clamping device, and a joining location other than the pre-spotting point in resistance welding (for example, a bolt fastening location or a welding location in fusion welding).

  However, it is self-evident that the shortest path among the plurality of reactive current energization paths, and hence the low resistance required for passage, is the path that passes through the nearest point. Therefore, even if it is a case where the slit 1a cannot be provided on all the lines which connect the already-welded point of each direction and the point 16 to be joined, the spot weld part 3 with the short distance from the point 16 to be joined is short. By forming the slit 1a preferentially between the two, the growth rate of the nugget obtained at the point 16 to be joined can be improved.

  Desirably, the slit 1a is provided on the line connecting the adjacent spot welded portion 3 or the adjacent adjacent shunt point and the point 16 to be joined, and more preferably, the adjacent in all directions. The slit 1a is provided on a line connecting the point and the point 16 to be joined.

  In the one-side spot welding shown in FIG. 6B, even if single point resistance welding is performed when there is no spot weld between the steel plates 6 and 7, the place where the steel plates 6 and 7 are clamped, A reactive current that flows through a contact portion between the electrode 10 and the steel plate 7 or a portion where the steel plates 6 and 7 are in strong contact with each other due to the structure is generated, and the nugget growth rate at the point 18 to be joined may be lowered.

  FIG. 7 is an explanatory view showing a location where the steel plates 6 and 7 come into strong contact with each other in the one-side spot welding, and FIG. 7A shows the steel plates 7 of the superposed steel plates 6 and 7 with each other. FIG. 7B shows a case where the steel plate 7 having the ridge portions 7b and 7b and the flat steel plate 6 are joined.

  As shown in FIGS. 7A and 7B, when a predetermined position of the steel plate 6 is pressed by the welding electrode 9 in order to perform one-side spot welding, the steel plates 6 and 7 are illustrated by this pressurization. Accordingly, the steel plate 7 partially contacts the steel plate 6 strongly at the corners of the convex portion 7a and the ridge line portions 7b and 7b.

  In one-side spot welding, reactive currents that flow through the contact points as described above tend to occur. As described above, this is due to the fact that the one-side spot welding has a long current-carrying path that contributes to welding, and that bonding is performed with a low applied pressure. That is, in the path where the current can be passed from the welding electrode 9 to the back electrode 10, a location where the steel plates 6, 7 are in contact with each other with a strong or wide area more than just below the welding electrode 10 (in the illustrated example, the corner of the convex portion 7 a And the ridge line portions 7b and 7b) are likely to be generated, and in this case, the interface resistance generated at the contact portion is low, so that the reactive current is easily generated.

Therefore, in the case of one-side spot welding, not only the spot welded portion 3, but also a part where all the steel plates are in strong contact with each other and a part or all of the region 25 connecting the points 16 to be joined, The effect of increasing the nugget growth rate at the point to be joined can be obtained by providing the slit 6a for the defect.
(Ii) Steel plate forming slit FIG. 8 is an explanatory view showing a steel plate forming slit, FIG. 8 (a) shows various steel plates in spot welding, and FIG. 8 (b) shows various steel plates in one-side spot welding. Further, FIG. 8C shows various steel plates in series spot welding.

  The left figure of Fig.8 (a) shows the case where the slit 2a is formed in the steel plate 2 with a small plate thickness instead of the steel plate 1 with a large plate thickness, and the middle figure of FIG. The case where the slit 1a is formed in the big steel plate 1 is shown, and the left figure of FIG. 8A shows the case where the slits 1a and 2a are formed in both the steel plates 1 and 2. Moreover, FIG.8 (b) shows the steel plates 6 and 7 in single side spot welding, and FIG.8 (c) shows the steel plates 11 and 12 in series spot welding.

  As described above, a decrease in the nugget growth rate due to the diversion to the already formed spot weld 3 in the resistance welding is more likely to occur as the plate thickness of the steel plates 1, 2, 6, 7, 11, 12 is thicker. As a result of various studies, the lower the specific resistance of the steel plates 1, 2, 6, 7, 11, 12, that is, the lower the specific electric resistance value of the steel plates 1, 2, 6, 7, 11, 12 at room temperature, the nugget It has been found that the growth rate tends to decrease. This is because as the plate thickness of the steel plates 1, 2, 6, 7, 11, and 12 is larger and the specific resistance is lower, the energization resistance when diverting from the welding point 16 to the spot welded portion 3 is lower. is there.

  For this reason, on the structure of the resistance welded joint to be manufactured, when the diversion path of all the steel plates among the two or more steel plates (1, 2), (6, 7), (11, 12) cannot be divided (for example, In the case where these steel plates are of a different combination, for example, when only one of the two sheets can be processed), a slit is formed in a steel plate having a large thickness or a low specific resistance value. By forming, a higher effect can be obtained.

  On the other hand, as a result of various investigations, in resistance welding in which the welding electrodes 9, 13, and 14 are arranged on one side of the stacked steel plates (6, 7) and (11, 12), such as single-side spots and series spots, Spot weldability is most strongly dependent on the electrical resistance and thickness of the steel plates 6 and 11 arranged on the welding electrodes 9, 13 and 14 side. As a result of evaluation by the above-described method, the nugget growth rate decreases as the specific electrical resistance of the steel plates 6 and 11 disposed on the welding electrodes 9, 13 and 14 is lower and the plate thickness is thicker.

  Therefore, in one-side spot welding or series spot, as shown in FIG. 8B and FIG. 8C, the steel plates 6 and 11 disposed on the welding electrodes 9, 13 and 14 side of two or more steel plates. It is effective to form slits 6a and 11a.

  In addition, when forming the slits 1a, 6a, and 11a causes a decrease in the strength of the resistance welded joint to be manufactured, after forming the slits 1a, 6a, and 11a and performing resistance welding, What is necessary is just to ripen the formation part of slit a, 6a, 11a by arc welding etc. and to improve an intensity | strength.

  FIG. 9 shows various situations in which three steel plates are overlapped and series spot welding is performed, and FIG. 9A shows a situation in which slits 6a are formed in the steel plate 6 with the largest plate thickness and the welding electrode 9 contacting. FIG. 9B shows a situation where the slits 6a and 7a are formed in the steel plates 6 and 7, and FIG. 9C shows a situation where the slit 7a is formed in the steel plate 7. FIG.

  As shown in FIG. 9A, the reactive current can be reduced by forming the slit 6a in the steel plate 6 arranged closest to the welding electrode 9 among the three steel plates 6, 7, and 27. it can.

  Further, as shown in FIG. 9B, the reactive current can be further reduced by forming the slits 7 a in the steel plate 7 in contact with the steel plate 6.

  Further, as shown in FIG. 9C, when the steel plate 6 with which the welding electrode 9 abuts does not have the spot welded portion 8, the welded electrode among the steel plates 7 and 27 joined by the spot welded portion 3. The reactive current can be reduced by forming the slits 7 a in the steel plate 7 disposed on the side closest to 9.

Furthermore, the present invention will be described more specifically with reference to examples.
The above-mentioned already welded spot welded portion 28 and the test pieces made of two-layer steel plates having various shapes having the slits 29 defined in the present invention are spot welded to form a resistance welded portion. The torsional fracture diameter of this resistance weld was investigated by an evaluation method. The shapes 1 to 10 of these test pieces are collectively shown in FIG. Shapes 1 to 8 are test pieces having a width of 30 mm and a length of 100 mm, and shapes 9 and 10 are test pieces having a width of 40 mm and a length of 120 mm.

  A single-point welding test was also carried out with the same welding method and welding conditions, and the above-described nugget growth rate was determined from the respective fracture diameters. The spot welding conditions were such that a nugget diameter of 4√t or more with respect to the plate thickness t was obtained during single point welding.

  The results are summarized in Table 1. In Table 1, the electrode tip 1 and the electrode tip 2 mean a welding electrode and a back electrode, respectively.

  Trial numbers A2, A4, A5, A8, A11 are provided with slits 29 in the steel plate on the electrode tip 1 side, trial number 7 is provided with slits 29 on the steel plate on the electrode tip 2 side, and trial numbers 9 and 12 are Slits 29 were provided in both the electrode tip 1 side and the electrode tip 2 side steel plates. Test numbers A1 to 5 are examples of spot welding to test pieces having shapes 1 to 3, and test numbers A2, 4, and 5 are evaluation welds 30 formed by spot welding 28 and spot welding. It is the example of this invention which provided the slit 29 between these. Trial numbers A14 and A16 are examples of the present invention in which a through hole 31 is provided in place of the slit 29 between the spot welded portion 28 and the evaluation point 30 as shown in the shape 10 to block the flow dividing path. .

  Under the condition of a welding current of 8 kA, the nugget growth rate was 60% or less in the comparative example shown in the trial number A1, whereas the invention example shown in the trial number A2 exceeded 65%. Further, in the condition of the welding current of 8 kA, the nugget growth rate of the example shown in the trial number 3 is 70% or less, whereas in the invention examples shown in the trial numbers A4 and 5, both nuggets exceeding 80% are obtained. It was.

  Next, an example in which spot welding is performed on the test pieces of shapes 4 and 5 shown in test numbers A6 to A9 will be described. These are examples in which two steel plates having different strengths were studied by changing the material forming the slit 29. Test numbers A7 to 9 are examples of the present invention in which a slit 29 is provided between the spot weld 28 and the evaluation point 30. The test number A7 was provided with a slit 29 shown in the shape 5 on both the 60 k precipitated steel side, the test number A8 on the SPCC side, and the test number A9 on both of the two steel plates. In the comparative example shown in the trial number A6, the nugget growth rate was 65% or less, whereas the trial number A7 in which the slit 29 was provided on the 60k precipitated steel side improved to a nugget growth rate of 65% or more. In the example where the slit 29 was provided on the SPCC side shown in the trial number A8, further improvement was recognized, and the nugget growth rate exceeded 70%. Further, in sample No. A9 in which the slits 29 were provided in both of the two steel plates, the nugget growth rate exceeded 75%, and the highest effect was obtained.

  A description will be given of an example in which two steel plates having different thicknesses shown in test numbers A10 to A12 are overlapped and spot-welded to the test pieces of shapes 4 and 5. Test numbers A11 and A12 are examples of the present invention in which a slit 29 is provided between the spot welded portion 28 and the evaluation point 30. The trial number A11 was provided with the slit 29 shown in the shape 5 in the steel plate having the larger thickness among the two steel plates, and the trial number A12 was provided in both steel plates. In the comparative example shown in the trial number A10, the nugget growth rate was 85% or less, whereas the nugget growth rate of the trial number A11 in which the slit 29 was provided in one sheet of steel exceeded 85%.

  Furthermore, in sample number A12 in which slits were provided in both of the two steel plates, a nugget growth rate of 90% or more was obtained.

  The trial numbers A13 to A16 will be described. Trial numbers A14 and A16 are examples of the present invention in which the through holes 31 are provided, and trial numbers A13 and A15 are comparative examples in which the through holes 31 are not provided. In the trial number 13 and the trial number 14 having a hitting point interval of 30 mm, in the comparative example shown in the trial number 13, the nugget growth rate was 67%, whereas in the inventive example of the trial number 14, it was 70% or more. Moreover, in the trial number 15 and the trial number 16 having a hitting distance of 40 mm, the comparative example shown in the trial number 15 has a nugget growth rate of 70%, whereas the present invention example of the trial number 16 has 75% or more. .

  One-side spot welding was performed on test pieces made of two-layered steel sheets having various shapes and provided with spot welds 28 and slits 29 that were already joined, and the twist fracture diameter of the welds was investigated by the method described above. In addition, a single-point welding test was also conducted under the same welding method and welding conditions, and the nugget growth rate was determined from the respective fracture diameters.

  The welding conditions in the one-side spot welding were such that a nugget diameter of 3√t or more with respect to the plate thickness t was obtained during single point welding. The test results are summarized in Table 2.

  In the trial numbers B2, 4, 6, 8, 10, 12, 14, 15, and 17, slits were formed in the material to be welded on the electrode tip side.

  First, an example of one-side spot welding to a test piece provided with one spot weld 28 as in the shapes 4 and 5 shown in the test numbers B1 to B6 will be described.

  Trial numbers B2, 4, and 6 are examples of the present invention. Test numbers B1 and B2, B3 and B4, and B5 and B6 are the same steel plate and welding conditions, respectively, and the present invention example and other shapes are compared.

  In the examples of the welding times of 10 cycles shown in the trial numbers B1 to B4, no joining was obtained in the trial numbers B1 and B3, whereas in the present invention examples shown in the trial numbers B2 and B4, the nugget growth rate was 85% or more. The nugget was obtained. Even in the example of the welding time 20 cycles shown in the trial numbers B5 and B6, the growth rate of the nugget was 60% or less in the trial number B5, whereas it was 70% or more in the invention example shown in the trial number B6.

  Next, an example of one-side spot welding to a test piece provided with two spot welds 28 shown in test numbers B7 to B12 will be described.

  Trial numbers B8, B10 and B12 are examples of the present invention. Trial numbers B7 and B8, B9 and B10, B11 and B12 are the same steel plates and welding conditions, respectively, and the present invention example and other shapes are compared. It is.

  While the nugget growth rate of the trial number B7 is 80% or less, in the example of the present invention shown in the trial number B8, a nugget exceeding 90% was obtained. Similarly, the nugget growth rate of the trial number B12 was 90% or more, while the nugget was not formed in the trial number B11, while the nugget was not formed in the trial number B11 with respect to 70% or less of the trial number B9.

  Next, an example in which one-side spot welding is performed by combining differential thickness plates shown in trial numbers B13 to B15 will be described.

  Test numbers B14 and B15 are examples of the present invention, and test number B13 is an example of welding under the same steel plate and welding conditions. The nugget growth rate of the trial number B13 was 74%, whereas the nugget growth rates of the present invention examples of the trial numbers B14 and B15 both exceeded 85%. As described above, the present invention example has a remarkable nugget growth rate compared to the comparative example in which the slit 29 is not formed between the evaluation point 30 and the spot welded portion 28 when resistance welding is performed under the same welding conditions. The increase of can be obtained with certainty.

  Furthermore, the case where a clamp part exists in the joint point vicinity like the shapes 7 and 8 shown to trial number B16-17 is demonstrated.

  The trial number B17 is an example of the present invention in which the slit 29 is provided between the evaluation point 30 and the portion where the steel plates strongly contact each other by the clamp 26.

  In the trial number B16, the nugget growth rate was 72% or less, whereas in the product of the present invention shown in the trial number B17, a nugget with a nugget growth rate of 90% or more was obtained. As described above, the example of the present invention can surely obtain a significant increase in the nugget growth rate even when the overlapping contact portion where the steel plates are in strong contact with each other other than the spot welded portion exists on the steel plate.

Reference example 1

  Two-point simultaneous welding series spot welding was performed on a test piece made of two-layer steel plates at a welding current of 8 kA and energization time of 20 and 15 cycles, and the torsional fracture diameter of the weld was examined. The test results are shown in Table 3. In each test, the larger nugget of the two welding points was evaluated.

Trial numbers C1 to C4 in Table 3 are examples of series spot welding in which the interval between welding points is 110 mm. Trial numbers C2 and C4 are examples in which a slit is provided between two points, and trial number C1. , C3 is a comparative example. In addition, the slits of the trial numbers C2 and C4 were provided in the steel sheet that comes into contact with the welding electrode tip of the series spot welder among the two-layered steel sheets.

  As shown in Table 1, when the energization time was 20 cycles, the maximum nugget growth rate was 65% in the trial number C1, whereas the trial number C2 welded under the same welding conditions as the trial number C1. The nugget growth rate was over 75%, significantly exceeding the trial number C1.

  Further, when the energization time is 15 cycles, the nugget growth rate of the trial number C3 was 55% or less, whereas the nugget growth rate of the trial number C4 welded under the same welding conditions as the trial number 3 is It was over 70%, greatly exceeding the trial number C3.

1, 2, 6, 7, 11, 12 Metal plate (steel plate)
Slit 1a, 2a, 6a, 11a
3, 8 Joint 4, 9, 13, 14 Welding electrode 5, 10 Back electrode 15, 17, 19 Resistance welded joint 16, 18, 20, 21 Resistance weld 25

Claims (2)

A plurality of metal plates are arranged superimposed to the sheet thickness direction, and the superimposed contact portion having electrical conductivity with said plurality of metal plates are in contact, before Symbol superimposed contact portion and the plurality of formed near the further comprising a slit formed so as to divide the resistance welding portion joining a metal plate, at least a part of the previous SL superimposed contact portion contact and region connecting the resistance welding portion, and the superimposed contact portion Is a portion including protrusions or corners formed on at least one metal plate of the plurality of metal plates. A resistor welding assembly according to claim 1 distance is 50mm or less between the resistance welding unit to the previous SL overlay contacts.

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