JP2007319889A - Series spot welding method and welding material structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a series spot welding method by which the stability of quality, the improvement of operability or the like, the reduction of designing and structural restrictions and the reduction of cost can be attained in a form of performing a welding by increasing the density of welding current. <P>SOLUTION: In the series spot welding method where either surface of superimposed two welding materials 21, 22 is press-contacted with a pair of separated electrodes 15, 16, and electric current is made to flow through the space between both the electrodes 15, 16, so as to weld the two welding materials 21, 22, at least one of the welding materials 21, 22 is provided with a projection 23 on the side between the materials, so as to form a gap 24 between the two welding materials 21, 22. At this time, when a pair of the electrodes 15, 16 are press-contacted, a pair of the electrodes 15, 16 are pressed from the face parts of the welding materials 21, 22, and the welding materials 21, 22 are deformed in such a manner that the gap 24 is crushed, sthereby welding them. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a series spot welding method and a welded material structure.

  In general, direct spot welding or series spot welding is performed when welding members, panels, and the like constituting a frame of a vehicle body.

  Direct spot welding, as shown in FIG. 9, sandwiches two superposed steel plates 1 and 2 between upper and lower electrodes 3 and 4 and pressurizes them to cause welding current to flow. The spot-like welded portion 5 is formed by using it.

  In the series spot welding, as shown in FIG. 10, a pair of spaced electrodes 6 and 7 are brought into pressure contact with one surface of two superposed steel plates 1 and 2, and a current is passed between both electrodes. The spot-like welded portion 8 is formed using the resistance heat generation of the steel plates 1 and 2.

  Here, as an example of a specific series spot welding, in order to reduce the reactive current flowing along the steel plate 1 which becomes a problem when a current flows between the electrodes 6 and 7, two sheets are used as shown in FIG. A back electrode 9 for controlling the current flowing through the pressure contact surface between the steel plates 1 and 2 in an increasing direction is disposed below the steel plates 1 and 2, and the current flowing along the electrode 9 as well as the steel plate 2 is combined. In some cases, a two-point spot-like weld (not shown) is suitably formed. In the case where the back electrode 9 is not provided, as shown in FIG. 12, the current flowing through the upper plate increases while the current flowing through the lower plate decreases. In particular, when the contact area increases due to the surface accuracy of the steel plates 1 and 2, the expected current density cannot be obtained, and a welded portion (not shown) cannot be formed appropriately.

  In another example of specific series spot welding, the absolute value of the current to the lower metal plate side determined by the resistance ratio of the upper and lower metal plates and the contact resistance between the upper and lower metal plates is intended to reduce the defective rate of the welding. In order to increase the current value between the electrodes 6 and 7, temporarily set to 1.5 times or more of the steady-state current only during the initial welding process, and after the pressure contact surface between the upper and lower metal plates is melted, it becomes easy to energize There is a type in which the current is returned to a steady current, the cracks caused by the overcurrent of the upper metal plate, in which electricity flows relatively easily, are prevented, and a constant nugget diameter is obtained. In addition, this series spot welding temporarily increases the pressure applied to the metal plate of the electrode 1.1 times or more so as to lower the contact resistance between the upper and lower metal plates when a steady current of 1.5 times or more flows. After that, when the steady current is returned to the normal value, the pressure applied to the metal plate of the electrode is restored (for example, see Patent Document 1). Here, in this series spot welding, the current value between the electrodes 6 and 7 is increased in the initial stage of welding, and by further increasing the applied pressure, the current absolute value between the upper and lower metal plates is temporarily increased, and further contact is made. The reduction in resistance and the reduction in contact area are promoted, and by combining these, the current density is increased and the defect rate is reduced.

Another specific example of series spot welding is to provide sufficient strength without a back electrode, and as shown in FIG. When welding 10 and 12, the seating surface 11 is crushed by the electrodes 6 and 7 of the welding apparatus, the two steel plates 10 and 12 are brought into point contact, and a spot-like welded portion (not shown) is suitably used. There is something to be formed (see, for example, Patent Document 2). Here, in the state where the two steel plates 10 and 12 are in point contact, the current density is increased by restricting the energization path.
Japanese Patent Laid-Open No. 11-333569 JP 2002-239742 A

  However, in direct spot welding, welding cannot be performed on a bag portion having a box cross-sectional shape, and it is necessary to provide a work hole for welding. Further, when the work hole is provided, there is a limitation in design and structure, and there is a problem that rigidity and strength are lowered. Furthermore, in the direct spot welding method, since the direct spot welding apparatus is enlarged and only one welded part can be obtained by one energization, it takes time to put in and out of the apparatus, resulting in inferior cost, productivity, and workability. It was.

  On the other hand, when the back electrode 9 is used as in the case of series spot welding, there are problems that equipment cost increases due to the back electrode 9 and that quality stability, workability, and security are poor.

  When the initial current is increased as in other examples of series spot welding, power consumption is increased and high pressure is required. In addition, since it is necessary to change the current absolute value and the applied pressure, there is a problem that quality is not stable and workability is deteriorated. Furthermore, since the applied pressure is high (250 kgf), it is necessary to use a robot or the like, and a pressing member on the back side of the work that prevents deformation of the welded part is required, resulting in an increase in equipment costs. Furthermore, there is a problem that a portion that can be applied to welding is limited due to a high pressurizing force and that it is impossible to work manually.

  When the seating surface 11 is provided as in another example of series spot welding, the electrodes 6 and 7 need to be accurately arranged at the set position so that the seating surface 11 is accurately crushed by the electrodes 6 and 7 of the welding apparatus. Therefore, there is a problem that the welding quality is greatly influenced by the setting mode of the electrodes 6 and 7, the quality is not stable, and the workability is deteriorated. In addition, since a certain load is required during welding, the lower plate side plate pressure is increased or a shape with rigidity is required, and if the welding tact is short in mass production, the seat surface 11 is There is a problem that the use of a robot or the like that crushes accurately becomes necessary, and the equipment cost increases. Furthermore, when considering the set position of the electrodes 6 and 7, the seat surface 11 needs to have a certain size so as not to cause poor welding, and the space for setting the seat surface 11 and the protrusions remaining after welding Due to the external shape, the parts that can be applied to welding are limited, and there are structural and design limitations. Furthermore, when crushing the seating surface 11, a certain load (50 kgf) is required, and when the seating surface 11 is made small so that the applicable part can be expanded, the load becomes even larger. Therefore, it was difficult to work manually. Further, when setting the seating surface 11 as a workpiece, it is necessary to build up the seating surface 11 on the mold, and particularly when the accuracy of the seating surface is corrected, there is a problem that the modification becomes large. It was.

  The present invention has been made in view of the above-described circumstances. In a mode of welding with increasing the density of welding current, improvement in quality stability, workability, etc., reduction in design and structural constraints, cost reduction. An object of the present invention is to provide a series spot welding method and a welded material structure capable of achieving the above.

  The present invention is a series spot welding in which a pair of spaced apart electrodes are brought into pressure contact with one surface of two overlapped materials to be welded, and a current is passed between the electrodes to weld the two materials to be welded. In the method, when a protrusion is provided on at least one of the materials to be welded and a gap is formed between the two materials to be welded, and the pair of electrodes are brought into pressure contact, the pair of electrodes are covered. The present invention relates to a series spot welding method, wherein the welded material is deformed and welded so as to be pressed from the surface portion of the welded material to crush the gap.

  Moreover, in this invention, when pressing a pair of electrode against one surface of the to-be-welded material provided with the some protrusion, it is preferable to press and weld the surface part between protrusions.

  The present invention provides a welded material structure in which a pair of spaced apart electrodes are pressed and contacted with one surface of two superposed welded materials, and a current is passed between the electrodes to perform welding. The present invention relates to a welded material structure characterized in that at least one projection is provided on the material-to-material side so that a gap is formed between two welded materials.

  Thus, according to the present invention, since the gap is crushed and the two materials to be welded are brought into point contact, the current density can be increased and welding can be performed. Unlike direct spot welding, in which only one welded part can be applied with one energization at the same time, two welds are formed with one energization, reducing labor and improving cost, productivity, and workability. In addition, since welding is possible from one surface of the workpiece, it is not necessary to provide a work hole when welding the bag part, etc., reducing design and structural restrictions, and at the same time preventing deterioration in rigidity and strength. be able to.

  In addition, since the back electrode is not required compared to normal series spot welding, the equipment cost is prevented from increasing, and the quality stability, workability, and safety are improved in welding that increases the current density. The structural constraints can be reduced.

  Furthermore, unlike series spot welding in which the initial current is increased, it is not necessary to change the current absolute value and the applied pressure, so that quality stability and workability can be improved. Further, it is possible to prevent an increase in equipment costs by eliminating the need for a holding member on the back side of the workpiece. Furthermore, since a high pressurizing force is not required, it is possible to relax restrictions on parts that can be applied to welding.

  Furthermore, unlike series spot welding in which a seating surface is provided, the portion to be crushed by the electrode is a surface portion, so that the work of accurately aiming at the target portion of the electrode is not required, and the material to be welded can be easily crushed. It is possible to appropriately weld a material to be welded with few structural restrictions in terms of sheet design, improve quality stability and workability, and reduce costs. In addition, since the holding member on the back side of the work is not required and work by manpower is possible, the equipment cost can be minimized. Further, it is not necessary to consider the space of the seating surface, and the unevenness of the protrusions remaining after welding is small, so that the restriction on the part applicable to welding can be relaxed, and the structural restrictions on design can be reduced. Furthermore, it is easier to modify the mold for forming the projection than to modify the mold to form a seating surface.

  When pressing a pair of electrodes against one surface of a material to be welded having a plurality of protrusions and pressing and welding the surface portion between the protrusions, the gap is very easily crushed and the two materials to be welded are suitably used. Welding can greatly improve quality stability and workability.

  According to the above-described series spot welding method and welded material structure of the present invention, in the aspect in which the welding current density is increased and welding is performed, stability of quality, improvement in workability, etc. Various excellent effects such as reduction and cost reduction can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIGS. 1-6 shows an example of the form which implements this invention, and the apparatus 13 of the series spot welding of this embodiment is equipped with a pair of electrodes 15 and 16 spaced apart via the pressurization part 14 in a main body. In addition, a contactor 18 and a welding transformer 19 are provided so that a current flows from the power source to the pair of electrodes 15 and 16 via the wiring 17, and the contactor 18 further includes a control unit 20 to control the current. Here, the series spot welding apparatus 13 may be an attachment type attached to a work robot or a portable type used by an operator. Further, the pair of spaced electrodes 15 and 16 may be of a fixed position type, the pitch (interval) between the electrodes 15 and 16 may be changed, or each electrode may be pressed substantially perpendicularly to the pressing surface of the workpiece 21. It may be a variable type.

  On the other hand, two welded materials 21 and 22 applied to series spot welding include a plurality of protrusions 23 on at least one welded material 21 and 22. Here, the welded materials 21 and 22 are preferably metal plates such as steel plates, but are not particularly limited as long as they can be welded by series spot welding. Further, the two welded materials 21 and 22 may be provided with a projection 23 on one side and a flat plate on the other, or may be provided with a projection 23 on both. Furthermore, the protrusion 23 may have any shape such as a round shape or an oval shape, or may be formed by pressing from the back surface, or may be a shape in which a protrusion-like member is attached to a flat plate. Further, the direction and interval of the protrusions 23 are not particularly limited, but are preferably substantially the same as the pitch of the pair of electrodes 15 and 16.

  When the two welded materials 21 and 22 are overlapped, the welded material 21 and 22 plates are overlapped so that the protrusion 23 faces the inside of the overlapping surface, and the two welded materials 21 are formed by the protrusion 23. , 22 is formed with a gap 24. Here, the protrusion 23 may be provided on any one of the welded materials 21 and 22 or may be provided on each of the two welded materials 21 and 22.

  Hereinafter, a series spot welding method according to an embodiment of the present invention will be described.

  When welding the two workpieces 21 and 22 (materials to be welded), after providing the projections 23 on at least one of the materials 21 and 22 to be welded, the projections 23 are overlapped (on the material side). The workpieces 21 and 22 are overlapped so as to be directed to each other, and a gap 24 is formed between the two workpieces 21 and 22 by the projections 23. As shown in FIG. The two welded materials 21 and 22 are fixed. Next, the pair of electrodes 15 and 16 are arranged above the two welded materials 21 and 22 by the series spot welding apparatus 13, and the pair of electrodes 15 and 16 are arranged from one surface of the welded materials 21 and 22. As shown in FIG. 3, the welded materials 21 and 22 are deformed so as to have the projections 23 as fulcrums by applying pressure, and the gap 24 is crushed. Subsequently, as shown in FIG. 4, the upper welded material 21 is brought into point contact with the lower welded material 22 at the plate interface by deformation of the applied pressure, and energization is started. Here, in the point contact, the contact resistance is large and the current density is high due to the low pressure. Further, in a state of point contact, as shown in FIG. 5, a predetermined current is passed between the pair of electrodes 15 and 16 in a constant cycle, and the welded portion 26 is formed on the two workpieces 21 and 22. Thereafter, the energization is terminated, the pair of electrodes 15 and 16 are left as they are, the two workpieces 21 and 22 are held, and cooled for a predetermined time. Next, after the holding and cooling are completed, as shown in FIG. 6, the pair of electrodes 15 and 16 are separated from the workpieces 21 and 22 and returned to the processing start position, and all the steps are completed.

  Here, as shown in FIG. 7, when the pair of electrodes 15 and 16 are pressed against the upper workpiece 21 with the protrusion 23, the surface portion between the protrusions 23 is pressed using the protrusion 23 as a mark. It is also possible to do. Further, the position where the electrodes 15 and 16 are pressed is not particularly limited as long as it is a surface portion that can crush the gap 24.

  Hereinafter, as an experimental example, those constructed in two examples of the present invention and those constructed in other comparative examples are compared in terms of tensile shear strength, and are shown in FIG.

  In one example of the present invention, the upper material to be welded is a flat plate and the lower material to be welded is a flat plate with protrusions. In another example of the present invention, the upper material to be welded is a flat plate with protrusions. In addition, the lower material to be welded is a flat plate. On the other hand, an example of the series spot welding of the comparative example (FIG. 8A) is a flat plate with the upper and lower welded materials, and an example of the direct spot welding of the comparative example (A in FIG. 8) is The application under the condition of the Chile limit current in the material to be welded is shown.

  Here, the flat plate of the material to be welded used in the two examples of the present invention and the other comparative examples is a steel plate having a thickness of 0.8 mm for the material to be welded on the upper side, and the material to be welded on the lower side. The steel plate has a thickness of 1.6 mm.

  Also, FIG. 8 shows the tensile shear strengths of the two examples of the present invention and other comparative examples.

  As a result, the series spot welding of the two examples of the present invention can be welded at a low pressurizing force (30 kgf) of about 1/6 compared with the direct spot welding (A) of the comparative example. Other examples of the invention showed substantially the same values as the direct spot welding (A) of the comparative example, and satisfied the tensile shear strength of JIS standard class B: 3.14 KN including the example of the present invention. Moreover, compared with the series spot welding (a) of the comparative example, 1.4 times or more high tensile shear strength was obtained.

  From the above, it is apparent that the example of the present invention can perform welding twice as much as the direct current welding with the pair of electrodes 15 and 16 at substantially the same current value, and greatly reduces the applied pressure. It is. Also in the series spot welding, it is clear that the tensile shear strength is higher than that obtained by superimposing two flat plates without protrusions, and the state of welding of the two sheets is good.

  Thus, according to the embodiment of the present invention, when welding the two workpieces 21 and 22, the gap 24 is crushed and the two workpieces 21 and 22 are brought into point contact, The current density can be increased for welding. Unlike direct spot welding, in which only one welded part can be formed with one energization, two welded parts can be formed with one energization, reducing labor and improving cost, productivity, and workability. Moreover, the quality stability and workability | operativity can be improved by welding the two to-be-welded materials 21 and 22 with low applied pressure. Furthermore, since welding can be performed from one surface of the workpieces 21 and 22, it is not necessary to provide a work hole when welding a bag part, etc., design and structural restrictions are reduced, and rigidity and strength are simultaneously reduced. Can be prevented.

  In addition, the back electrode is not required compared to the normal series spot welding, so the increase in equipment cost is prevented, the stability of quality, workability and security are improved, and there are restrictions on the design and structure. A reduction can be made.

  Furthermore, unlike the series spot welding that increases the initial current, it is not necessary to change the current absolute value and the applied pressure, so that the quality stability and workability can be improved. Further, it is possible to prevent an increase in equipment cost by eliminating the need for a holding member on the back side of the workpiece. Furthermore, since a high pressurizing force is not required, the restriction on the parts that can be applied to welding can be greatly relaxed.

  Further, unlike the series spot welding in which the seat surface is provided, the portion to be crushed by the electrodes 15 and 16 is a surface portion, so that the work of accurately aiming at the target portion of the electrodes 15 and 16 is not required, 22 to facilitate crushing, and to properly weld the materials to be welded 21 and 22 with less structural restrictions on the design of two sheets, to improve quality stability, workability, and cost reduction Can do. In addition, almost no pressing member on the back side of the work is required, and work by manpower is also possible, so that the equipment cost can be minimized. Furthermore, it is not necessary to consider the space of the seating surface, and the unevenness of the projections 23 remaining after welding is small. Therefore, the restriction on the part applicable to welding can be relaxed, and the structural restrictions on design can be reduced. Furthermore, it is simpler when the accuracy of the seating surface is corrected as compared with the case where the seat surface is formed.

  When the pair of electrodes 15, 16 are pressed against one surface of the workpieces 21, 22 having a plurality of protrusions 23, if the surface portion between the protrusions 23 is pressed using the protrusions 23 as a mark, the gap 24 is extremely reduced. It can be easily crushed and the two workpieces 21 and 22 are suitably welded, and the stability of quality and workability can be greatly improved. Here, the arrangement of the protrusions 23 is not particularly limited. However, when a plurality of protrusions 23 are formed at a predetermined interval, the gaps 24 between the two welded materials 21 and 22 are uniformly formed. The two welded materials 21 and 22 are suitably welded, and the quality stability and workability can be greatly improved.

  Note that the series spot welding method and the welded material structure of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is an II-II arrow line view of FIG. It is a conceptual diagram which shows the state which started the pressurization with an electrode. It is a conceptual diagram which shows the state which started electricity supply. It is a conceptual diagram which shows the state which completed electricity supply. It is a conceptual diagram which shows the state which completed welding. It is a conceptual diagram which shows the state which pressurized by the electrode in the state provided with the processus | protrusion in the upper to-be-welded material, and started energization. It is the table | surface which compared this invention and the comparative example. It is the schematic which shows general direct spot welding. It is the schematic which shows series spot welding (without a back electrode). It is the schematic which shows an example of the conventional series spot welding. It is the schematic which shows the case where two sheets of to-be-welded materials are made into a plane board in series spot welding without a back electrode. It is the schematic which shows the other example of the conventional series spot welding (no back electrode).

Explanation of symbols

15 electrode 16 electrode 21 material to be welded 22 material to be welded 23 protrusion 24 gap

Claims (3)

  In a series spot welding method in which a pair of spaced electrodes are brought into pressure contact with one surface of two superposed welded materials, and a current is passed between the electrodes to weld the two welded materials. When a protrusion is provided on at least one of the welding materials between the two materials to form a gap between the two materials to be welded and the pair of electrodes are brought into pressure contact with each other, the pair of electrodes are connected to the surface portion of the material to be welded. A series spot welding method characterized by deforming and welding a material to be welded so as to crush the gap by pressing from the side.   2. The series spot welding method according to claim 1, wherein when the pair of electrodes are pressed against one surface of a workpiece to be welded having a plurality of protrusions, the surface portion between the protrusions is pressed and welded.   In a welded material structure in which a pair of spaced apart electrodes are brought into pressure contact with one surface of two superposed welded materials and an electric current is passed between both electrodes to weld, at least one of the welded materials A welded material structure characterized in that a projection is provided on the material-to-material side so that a gap is formed between two welded materials.

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