JP2009095881A - Method of manufacturing welded structural member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a welded structural member by stably forming a large nugget in the interface of members to be welded by using one-side resistance spot welding by which the members to be welded are pressurized from one side without using a back bar and a back bar electrode even when the members to be welded are metal sheets having low rigidity. <P>SOLUTION: When performing the one-side resistance spot welding in which a second member 2 to be welded is energized through an electrode tip 3 for spot welding which abuts on the surface of the second member 2 to be welded which is arranged by being superposed on a first member 1 to be welded, a projecting part 4 which is convex toward the side of the second member 2 to be welded is formed in a position of the first member 1 to be welded, the position being opposite to a position where the electrode tip 3 for spot welding abuts on the second member 2 to be welded. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a welded structural member. Specifically, the present invention relates to a method for manufacturing a welded structural member by performing so-called one-side resistance spot welding.

  As is well known, spot welding, which is a representative example of lap resistance welding, includes a plurality of metal plates to be welded and placed on both sides by a pair of spot welding electrode tips arranged opposite to each other. By energizing while pressurizing in, by passing a large current through the welding location of each member to be welded, by forming a melted portion called nugget by the resistance heat generated by this, by welding each member to be welded is there. Spot welding is widely used for welding thin steel sheets constituting automobile bodies.

  In order to perform this spot welding, it is generally necessary to sandwich and pressurize a plurality of members to be welded by a pair of spot welding electrode tips arranged opposite to each other. For this reason, for example, when welding a member to be welded having a closed cross-sectional structure and a plate-like member to be welded (for example, a plate-like reinforcement in a direction perpendicular to the longitudinal direction inside the closed cross-section body) When manufacturing a car body side member or cross member configured with a metal plate), it is not possible to sandwich and pressurize each member to be welded by a pair of spot welding electrode tips from both sides. In many cases, welding can be performed only from one side of the overlapped members to be welded, for example, by melt welding such as arc welding or laser welding. However, when arc welding is performed, thermal distortion is likely to occur in the member to be welded. On the other hand, there is a problem that equipment costs increase when laser welding is performed.

  Therefore, even when it is difficult to sandwich and weld a plurality of welded members from both sides by a pair of spot welding electrode tips, the spot welding electrode tips are pressed only from one side of the overlapped welded members. Inventions relating to so-called one-side resistance spot welding, in which resistance spot welding is performed, have been proposed.

  As one-side resistance spot welding, (a) before performing welding, a back bar electrode which is a dedicated electrode for supporting a welded portion inside a hollow welded member having a closed cross-sectional structure is used. An invention for performing resistance spot welding after being separately arranged, and (b) an electrode tip for spot welding arranged in two rows in parallel using a back bar for supporting a welded portion that does not have an electrode function There has been known an invention relating to a so-called series spot welding method in which resistance spot welding is performed by energizing during the period.

  For example, in Non-Patent Document 1, when a supporting member such as a back bar electrode or a back bar is not disposed at a portion facing one spot welding electrode tip to be pressurized, the pressure applied by the spot welding electrode tip is set low. Thus, an invention for performing one-side resistance spot welding is disclosed. However, according to the present invention, it is difficult to obtain a sound welded portion, and it is difficult to ensure welding quality such as welding strength.

  In Patent Document 1, a protrusion that protrudes toward the electrode tip for spot welding is formed on a member to be welded that contacts the electrode tip for spot welding when performing one-side resistance spot welding. By carrying out resistance spot welding while pressing the electrode tip for spot welding against the part and applying pressure while pressing the member to be welded to deform this projection, sufficient welding strength can be obtained without using a backbar electrode or backbar. The invention to be obtained is disclosed.

Further, in Patent Document 2, when the first welded member, the second welded member, and the third welded member made of a metal plate are subjected to overlap resistance welding, a pair of recesses are provided at one center. The first welded member and the second welded member are resistance spot welded using the spot welding electrode tip, and the surface of the first welded member abutted on the spot welding electrode tip is obtained. Two convex portions are formed at positions corresponding to the concave portions, the third welded member is overlapped with the first welded member via the tops of the two convex portions, and the two welded members in the third welded member are overlapped. Two spot welding electrode tips are respectively pressed to the positions where the convex portions come into contact, and one spot welding electrode tip → one convex portion → the other one convex portion → the other one spot welding electrode tip By passing the current in order, the third welded member Invention to perform series spot welding without using a press die for forming the convex portion is disclosed.
Japanese Patent Laid-Open No. 2002-239742 JP 2006-61916 A Welding technology, December 2006 issue, 109P, one-side resistance spot welding of automobile parts

  In the invention disclosed in Patent Document 1, a pressing force is required to deform the protruding portion during resistance spot welding. At this time, depending on the rigidity of the member to be welded, not only the protrusion but also its peripheral part may be deformed by this pressurization. Therefore, it is difficult to apply the present invention to welding of a member to be welded having low rigidity.

  In the invention disclosed in Patent Document 2, the welding step includes a first step of welding the first welded member and the second welded member, and a first step of welding these and the third welded member. Since there are two processes including two processes, the efficiency of the welding operation is low. Further, the diameter of the formed protrusion is limited to the size of the recess formed at the tip of the electrode, and the nugget diameter formed along with this is reduced, so that the welding strength tends to be insufficient.

  Further, without using a back bar or back bar electrode as in the inventions described in Patent Documents 1 and 2, the electrodes are pressed from one side only to the protrusion formed on one welded member to add each welded member. When resistance spot welding is performed while pressure is applied, if the member to be welded on which the protrusion is formed has low rigidity, the member to be welded bends during welding, thereby increasing the contact area between the members to be welded. For this reason, the spread of the electric current to to-be-welded members other than the to-be-welded member in which this projection part was formed becomes large, and it becomes difficult to raise an electric current density. For this reason, it becomes difficult to form a sound nugget at the interface of each member to be welded, and a reduction in welding quality is inevitable.

  The object of the present invention is to use one side to press from one side of the member to be welded even if the member to be welded is a metal plate having low rigidity, such as a steel plate having a thickness of 3 mm or less, without using a back bar or a back bar electrode. It is to provide a method of manufacturing a welded structure member that uses a resistance spot welding to stably form a large nugget at the interface of a member to be welded, whereby the weld has both sound joint characteristics and strength. .

  In order to solve such a problem in the one-side resistance spot welding, the present invention is directed to the welded portion of the member to be welded that does not contact the spot welding electrode tip, toward the side of the member to be welded that contacts the spot welding electrode tip. This is based on the knowledge that it is effective to form a protruding portion that is convex.

  Further, the present invention provides an electrode tip for spot welding that abuts on a surface of a second welded member that is disposed in contact with the first welded member or superimposed on one or more welded members. A method of manufacturing a welded structural member in which a first welded member and a second welded member are welded by performing one-side resistance spot welding to energize the second welded member, 1 to-be-welded member has a projecting portion that protrudes toward the second to-be-welded member at a position opposite to the position of the second to-be-welded member, where the electrode tip for spot welding abuts. It is a manufacturing method of the welding structure member characterized by energizing the 1st member to be welded through this projection part.

  In addition, the present invention provides an electrode tip for spot welding that is in contact with the surface of the second member to be welded, which is arranged so as to be superimposed on the first member to be welded that forms a main body having a closed cross-sectional structure together with the third member. A method of manufacturing a welded structural member in which a first welded member and a second welded member are welded by performing one-side resistance spot welding to energize the second welded member, 1 to-be-welded member has a projecting portion that protrudes toward the second to-be-welded member at a position opposite to the position of the second to-be-welded member, where the electrode tip for spot welding abuts. It is a manufacturing method of the welding structure member characterized by energizing the 1st member to be welded through this projection part.

  In addition, the present invention is arranged via a spot welding electrode tip that is arranged to be overlapped with the first member to be welded and is in contact with the surface of the second member to be welded that forms a main body having a closed sectional structure together with the third member. A method of manufacturing a welded structural member in which the first welded member and the second welded member are welded by performing one-side resistance spot welding to energize the second welded member, The welded member has a protruding portion that protrudes toward the second welded member at a position opposite to the position of the second welded member on which the spot welding electrode tip abuts. It is a manufacturing method of the welding structure member characterized by energizing the 1st member to be welded via a projection part. In this case, the first member to be welded is exemplified as a reinforcing member that is disposed inside the main body and reinforces the main body.

  In these methods for manufacturing a welded structure member according to the present invention, it is desirable that the protrusion has a shape in which the cross-sectional area increases from the top to the bottom.

  By the method for manufacturing a welded structure member according to the present invention, a member to be welded that is spot welded by being overlapped without using a back bar or a back bar electrode by using one-side resistance spot welding that pressurizes from one side of the member to be welded. Even if it is a thin metal plate with low rigidity, for example, a thin steel plate with a thickness of 3 mm or less, a large nugget is stably formed at the interface between the overlapped welded members, so that the welded portion is sound. Spot welding having both excellent joint characteristics and sufficient strength can be performed.

  For this reason, according to the present invention, in particular, various members such as side members and cross members constituting the automobile body, pillars such as A pillars and B pillars, side sills, and roof rail sides, such as strength members of the monocoque body, A strength member of an automobile body having a closed cross-section main body and having a separate reinforcement formed therein can be reliably and inexpensively manufactured as a welded structure member.

(Embodiment 1)
Hereinafter, the best mode for carrying out the method for manufacturing a welded structure member according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 13 is an explanatory diagram illustrating a situation in which the welding method for the welded structure member of the present embodiment is performed.
As shown in FIG. 13, the metal plate member 17 as the second member to be welded is in contact with the spot welding electrode tip 3 of the one-side spot welding, and the metal as the first member to be welded disposed thereunder. The plate member 18 is provided with a projection 4 directed toward the spot welding electrode tip 3.

The metal plate 18 is supported by two electrodes 19 installed at positions distant from the spot welding electrode tip 3, and there is no support immediately below the spot welding electrode tip 3.
With the spot welding electrode tip 3 urged the metal plate 17 toward the metal plate 18, and with the metal plates 17, 18 in pressure contact via the projection 4, the spot welding electrode tip 3 and projection 4, even when the metal plates 17 and 18 that are overlapped and spot welded without using a back bar or a back bar electrode are thin metal plates with low rigidity. A large nugget can be formed stably at the interface between the metal plates 17 and 18, and spot welding can be performed in which the weld has both sound joint characteristics and sufficient strength.

In the one-side resistance spot welding, the metal plate 17 is pressed and brought into pressure contact with the metal plate 17 by urging the metal plate 17 toward the metal plate 18 by the electrode tip 3 for spot welding. By energizing the metal plate 17 from the spot welding electrode tip 3 without supporting the position where the spot welding electrode tip 3 is in contact with the metal plate 17 in the metal plate 18, The metal plate 17 and the metal plate 18 are welded.
(Embodiment 2)
Next, a second embodiment will be described. In the following description of each embodiment, parts that are different from the above-described embodiment will be mainly described, and parts that are the same as those already described will be denoted by the same reference numerals and redundant description will be given. Omitted as appropriate.

  As shown in FIG. 1, in the present embodiment, for example, a plate-like member disposed to overlap a plate-like first welded member 1 that is a member having a hollow hat-shaped cross section made of, for example, a steel plate. Alternatively, the second welded member 2 is energized through the spot welding electrode tip 3 that is in contact with the surface of the second welded member 2 that is a steel plate having a closed cross-sectional structure, and the first welded member 1 One-side resistance spot welding is performed in which the first member to be welded 1 is energized through an electrode 3 'that is in contact with the plate-like third member 5 that is arranged so as to overlap the flange portions 1b and 1b formed at the edge. . In addition, before or after performing one-side resistance spot welding, the flange portion of the first member to be welded 1 and the third member 5 are joined by ordinary resistance spot welding. The welded structure member 0 in which the first welded member 1, the second welded member 2, and the third welded member 5 are joined by welding is manufactured by this one-side resistance spot welding and flange welding. Reference symbol A represents a welding power source.

  In the present embodiment, the first welded member 1 is placed on the side of the second welded member 2 at a position 1a opposite to the position 2a of the second welded member 2 where the spot welding electrode tip 3 abuts. It has the protrusion part 4 which becomes convex toward the surface, desirably the protrusion part 4 having a shape in which the cross-sectional area increases from the top to the bottom.

  In this way, by using the first member to be welded having the protrusions 4 and biasing the member 2 to be welded 1 with the electrode tip 3 for spot welding, the members 1 and 2 to be welded, By applying current between the electrode tip 3 for spot welding and the electrode 3 ′ in a pressure contact state via the protrusion, the electrodes are overlapped and spot welded without using a back bar or back bar electrode. Even if the welded members 1 and 2 are thin metal plates with low rigidity, for example, a thin steel plate having a thickness of 3 mm or less, a large nugget is stably formed on the interface between the welded members 1 and 2 that are overlapped. Thus, spot welding can be performed in which the weld has both sound joint characteristics and sufficient strength. Hereinafter, in the present embodiment, a reason for forming a protrusion that protrudes toward the welded member 2 with which the spot welding electrode 3 abuts is formed on the welded member 1 with which the spot welding electrode tip 3 does not abut. Will be explained.

FIG. 2 is an explanatory diagram schematically showing a situation in which normal resistance spot welding is performed.
As shown in the figure, in normal spot welding performed by placing a pair of spot welding electrode tips 3-1 and 3-2 facing each other with two overlapped members to be welded 1 and 2 being welded, Of the members 1 and 2, the portion sandwiched between the spot welding electrode tips 3-1 and 3-2 is pressurized. As a result, the portion sandwiched between the spot welding electrode tips 3-1 and 3-2 becomes the energization path 6 (see the portion with a broken line in FIG. 2), and sufficient dimensions are generated due to resistance heat generation at the interface of the welded members 1 and 2. The nugget 7 having is formed, and the welded members 1 and 2 are reliably welded.

  On the other hand, in FIG. 3, a support member (for example, a back bar electrode or a back bar such as a block) for supporting the welded members 1 and 2 is disposed on the side facing the spot welding electrode tip 3-1. It is explanatory drawing which shows typically the condition which performs the one-side resistance spot welding, pressurizing only from the to-be-welded member 2 side.

  As shown in the figure, in one-side resistance spot welding, the applied pressure is not concentrated directly below the spot welding electrode tip 3-1, and the electrode 3 'on the other side of the spot welding electrode tip 3-1 is the electrode 3 as shown in FIG. It is arranged at a location away from the opposing position of -1. For this reason, since the welded members 2 and 1 urged by the spot welding electrode tip 3-1 are bent and deformed as shown in the figure, the current no longer converges on the interface between the welded members 1 and 2. . For this reason, the current density of the member 2 to be welded is higher than the current density of the member 1 to be welded, and the nugget 7 is formed in preference to the inside of the member 2 to be welded rather than the interface between the members 1 and 2 to be welded. , Welding quality will be inferior.

  On the other hand, in this Embodiment, it protrudes toward the to-be-welded member 2 side which the electrode tip 3-1 for spot welding contacts the to-be-welded member 1 to which the electrode tip 3-1 for spot welding does not contact | abut. Therefore, since the enlarging of the energization path 6 in the member 1 to be welded is suppressed and heat can be effectively generated at the interface between the members 1 and 2 to be welded, the nugget is formed at the interface between the members 1 and 2 to be welded. 7 can be formed reliably and a sound weld can be obtained.

  In FIG. 4, a protruding portion that protrudes toward the welded member 1 that does not contact the spot welding electrode tip 3-1 is formed on the welded member 2 that contacts the electrode tip 3-1 for spot welding. FIG. 6 is an explanatory diagram schematically showing a situation in which one-side resistance spot welding is performed.

  In this case, as shown in the figure, in the member 2 to be welded, not only the energization path 6 is restricted at the contact portion with the spot welding electrode tip 3-1, but also the energization path 6 is restricted at the protrusion 4. In combination with this, the current density is increased in the entire protrusion 4 and the amount of heat generation is increased. For this reason, after the projection 4 starts energization by pressurization, it collapses early, and thereafter the welding phenomenon similar to the case where the projection 4 is not formed, that is, the energization path 6 in the member 1 to be welded is expanded. Therefore, a healthy nugget cannot be formed at the interface between the members 1 and 2 to be welded.

  In FIG. 5, a protrusion that protrudes toward the welded member 2 with which the spot welding electrode tip 3-1 contacts is formed on the welded member 1 with which the spot welding electrode tip 3-1 does not contact. FIG. 6 is an explanatory diagram showing a situation where one-side spot welding is performed. Moreover, FIG. 6 is explanatory drawing which shows the condition when this one-side spot welding is complete | finished.

  As shown in FIG. 5, when one-side resistance spot welding is performed by forming a protruding portion 4 that protrudes toward the welded member 2 on the welded member 1, the energization path 6 in the protruding portion 4 is connected to the welded member 1. Enlarged inside. For this reason, as shown in FIG. 4, the temperature rise of the protrusion 4 is reduced compared to the case where the protrusion 4 that protrudes toward the member 1 to be welded is formed on the member 2 to be welded, and the protrusion 4 collapses. Is less likely to occur. For this reason, the effect of providing the protrusions 4 is maintained until the end of energization, so that a healthy nugget 7 is formed at the interface between the members to be welded 1 and 2 as shown in FIG.

  The shape of the protrusion 4 is not particularly limited, but the shape in which the cross-sectional area gradually increases from the top to the bottom, for example, a hemispherical shape or a truncated cone shape, This is desirable because the energization path is expanded toward the bottom of the protrusion 4 to prevent the protrusion 4 from collapsing. In particular, the shape of the protrusion 4 is preferably a hemispherical shape. When the shape of the projection 4 is a truncated cone, if the flat portion at the top is too large, the contact area of the members to be welded 1 and 2 increases, and the current density does not increase, so that a healthy nugget is difficult to form. . Therefore, in this case, it is desirable to suppress the diameter of the top flat portion to 1.5 times or less the required nugget diameter.

  Furthermore, it is desirable to set the bottom of the protrusion 4 to be larger than the required nugget diameter. That is, since the contact portion by the protrusion 4 is the energization path 6, it is difficult to obtain a nugget diameter larger than that.

  What is necessary is just to set the height of the projection part 4 suitably according to the quality requested | required after welding. That is, if the height of the protrusion 4 is set high, the protrusion 4 may remain after welding. In this case, a gap remains between the members 1 and 2 to be welded. When importance is attached to the electrodeposition paintability in the vicinity of the welded portion, it is advantageous to leave a gap between the members to be welded 1 and 2 after welding because the electrodeposition paint can easily enter the gap. Therefore, in such a case, it is desirable to set the height of the protruding portion 4 as high as, for example, more than 2 mm so that a gap remains between the welded members 1 and 2. On the other hand, when the function and appearance in the vicinity of the welded portion are emphasized and it is required that no gap remains between the welded members 1 and 2 in the vicinity of the welded portion, the height of the protruding portion 4 is, for example, 2 mm. It is desirable to set it as low as below.

  As described above, since the protrusion 4 is crushed along with energization, if the height of the protrusion 4 is too low, the contact area of the members 1 and 2 to be welded increases, and the molten portion is formed without increasing the current density. It becomes difficult to be done. Therefore, it is desirable to set the height of the protrusion 4 to 0.5 mm or more.

  Thus, the 1st to-be-welded member 1 and the 2nd to-be-welded member 2 are joined by performing one-side resistance spot welding, and also the 1st to-be-welded member 1 and the 1st to-be-welded by normal resistance spot welding. By joining the three members 5, the welded structure member 0 in which the first welded member 1, the second welded member 2, and the third member 5 are joined by welding is manufactured.

Therefore, according to the present embodiment, without using the back bar or the back bar electrode, even if the members to be welded 1 and 2 are metal plates having low rigidity such as steel plates having a plate thickness of 3 mm or less, the members to be welded are not welded. A large nugget can be stably formed on the interface of the members 1 and 2 to be welded by one-side resistance spot welding in which pressure is applied from one side of the members 1 and 2. For this reason, as shown in FIG. 1, since the third member 5 exists, the spot welding electrode is located at a position opposite to the position where the spot welding electrode tip 3 contacts in the first welded member 1. The welded structural member 0 having a structure in which the tip cannot be brought into contact can be reliably manufactured so that the welded portion has both sound joint characteristics and strength.
(Embodiment 3)
Next, a third embodiment will be described.

  Fig.7 (a) is explanatory drawing which shows the structure of the welding structure member 11 manufactured by this Embodiment, and FIG.7 (b) is AA sectional drawing in Fig.7 (a). FIG. 8 is a perspective view showing the welded structural member 11 in a see-through state.

  In the present embodiment, the welded structural member 11 includes a first welded member 8, a second welded member 10, and a third welded member 9, and the first welded member 8 includes The second welded member 10 is similar to the first embodiment in that it has a structure in which the spot welding electrode tip cannot be brought into contact with the position where the spot welding electrode tip 3 comes into contact. And the third member 9 to be welded constitute a main body having a closed cross-sectional structure, and the first member to be welded 8 is disposed inside the main body and functions as a reinforcing member for reinforcing the main body. Is different.

  That is, as shown in FIGS. 7A and 7B, the welded structural member 11 includes a third welded member 9 having a hat-shaped cross section and a second member that is a flat plate-like closing member. It has a closed cross-sectional structure in which a first member to be welded 8 is disposed inside a main body having a hollow cross section composed of the member to be welded 10. The first member to be welded 8 includes flanges 8a and 8b formed by bending in opposite directions at both ends thereof. One flange 8 a is formed with a protrusion 4 that protrudes toward the second member to be welded 10.

  In the assembly of the welded structural member 11, first, the first flange 8a having the projection 4 is directed to the open side (the upper side in FIG. 7A) of the third welded member 9, and the first The member to be welded 8 is disposed inside the third member to be welded 9, and then the bottom 9a of the third member to be welded 9 and the flange 8b of the first member to be welded 8 are joined by ordinary spot welding or the like. To do.

  Thereafter, the flange 8a and the second welded member 10 are overlapped with each other via the protrusion 4, and the second welded member 10 side is placed by the spot welding electrode tip 3 provided on the second welded member 10. One-side resistance spot welding is performed between the electrode tip 3 for spot welding and an electrode (not shown) provided on the bottom 9a of the third member 9 to be welded. Thus, the first welded member 8 and the second welded member 10 are joined by welding.

  Before or after one-side resistance spot welding, a pair of spot welding electrode tips (not shown) with the flanges 9b, 9b of the third welded member 9 and the second welded member 10 overlapped. Joining is performed by ordinary spot welding in which pressure is applied and current is sandwiched between.

Thus, as shown in FIG.
(A) a third welded member 9 having a hat-shaped cross section;
(B) a second welded member 10 which is joined by welding via the flanges 9a and 9b of the third welded member 9 and functions as a closing member;
(C) While being welded to the second welded member 10 via the flange 8a, the flange 8b is welded to the inside of the main body having a closed cross-sectional structure constituted by the third welded member 9 and the second welded member 10. As a reinforcing member of the main body, a surface parallel to the surface portion is arranged in a direction perpendicular to the longitudinal direction of the third welded member 9 by being welded to the third welded member 9 via A welded structural member 11 having a functioning first welded member 8 is manufactured.

When the welded structural member 11 is manufactured, when the flange 8a of the first welded member 8 is welded to the second welded member 10, the accuracy of the bending process of the flange 8a if the protrusion 8 does not exist on the flange 8a. In some cases, as shown in FIG. 9, the bent portion 8c of the flange 8a preferentially contacts the second member to be welded 10 and sparks are generated at that location, so that welding may be impossible. Moreover, as shown in FIG. 10, the end surface 8d of the flange 8a may contact the 2nd to-be-welded member 10, and a spark may generate | occur | produce. Accordingly, when the welded structural member 11 is manufactured by one-side resistance spot welding, the protruding portion 4 is convex toward the second welded member 10 side on the flange 8a of the first welded member 8. It is indispensable to form.
(Embodiment 4)
FIG. 11 shows the present embodiment in which the first welded member 12 that is a reinforcing member different from the first welded member 8 that is the reinforcing member in the above-described third embodiment is provided inside the main body of the closed section. It is explanatory drawing which shows the welding structure member 13 of.

  The welded structural member 13 is formed so that the surface parallel to the surface portion 12a of the first welded member 12 functioning as a reinforcing member is parallel to the longitudinal direction of the hat-shaped third welded member 9. 1 to-be-welded member 12 is provided inside the main body.

  Also in this welded structure member 13, similarly to the welded structure member 11 shown in FIGS. 7 to 8, the flat plate-like second welded member 10 and the first welded member 12 are joined to each other by the one-side resistance spot welding. By superimposing via a protruding portion (not shown) that protrudes toward the second member to be welded 10 provided on the flange portion 12b of the member to be welded 12, the members are reliably joined.

  In the above description of the third and fourth embodiments, the case where the first welded members 8 and 12 that function as the reinforcing members are formed of a single member is taken as an example. For example, as illustrated in FIG. 12, the first member to be welded 16 that functions as a reinforcing member may be formed by joining two plate-like constituent members 14 and 15 by welding.

  As the welded structural members 11 and 13 provided by the third and fourth embodiments, for example, various members such as side members and cross members constituting an automobile body, pillars such as A pillars and B pillars, side sills, and roof rail sides Such a strength member of the monocoque body is exemplified. That is, the present invention can reliably and inexpensively manufacture the strength members of these automobile bodies having a closed cross-section structure, in which a reinforce, which is a separate component, is disposed. Is particularly suitable.

  Moreover, the material of the 1st-3rd to-be-welded member should just be a metal material in which resistance spot welding is possible, for example, steel, an aluminum alloy, etc. are illustrated. In addition, the first to third members to be welded may have surface-treated surfaces, and for example, galvanized steel materials, organic resin-coated steel materials, and the like can be used.

  Thus, according to Embodiments 1 to 4, without using a back bar or a back bar electrode, even if the member to be welded is a metal plate with low rigidity, such as a steel plate with a plate thickness of 3 mm or less, A welded structure member in which a large nugget is stably formed at the interface of the member to be welded by using one-side resistance spot welding that pressurizes from one side of the member to be welded, whereby the welded portion has both sound joint characteristics and strength. Can be manufactured.

Furthermore, the present invention will be described more specifically with reference to examples.
As shown in FIG. 13, a 590 MPa-grade steel plate 17 having a thickness of 1.4 mm and a 590 MPa-grade plate thickness 1. mounted on support bases 19, 19 serving also as copper electrodes spaced apart by 30 mm. The 6 mm steel plate 18 is completely overlapped and fixed in a size of 30 mm × 100 mm, and the spot welding electrode tip 3 is brought into contact with a predetermined position of the steel plate 17 to pressurize the steel plates 17 and 18. One-side resistance spot welding was performed.

  When performing this one-side resistance spot welding, the protrusion 4 formed on the steel plate 18 so as to protrude toward the steel plate 17 has a curved surface with a radius of curvature of about 8 mm, a height of about 1 mm, and a bottom portion. A hemisphere having a diameter of about 8 mm. The electrode tip 3 for spot welding was composed of a chromium copper electrode having a tip radius of curvature of 100 mm and a thickness of 16 mm.

  As the evaluation of the welded portion, the tensile shear strength was measured, and the nugget diameter at the joint interface was measured from the fractured portion after the tensile test. Moreover, the penetration depth of the steel plate 18 was measured from the cross section of the weld.

  The results (the strength of the weld, the nugget diameter, and the penetration depth of the steel plate 18) are shown in Table 1 together with the welding conditions (pressing force, current, and energization time).

  No. in Table 1 No. 1 is a comparative example using a steel plate without the protrusions 4. 2 is a comparative example in which the steel plate 17 is provided with a protrusion 4 that is convex toward the steel plate 18 side.

  In contrast, No. 1 in Table 1 was obtained. 3 is an example of the present invention in which the protruding portion 4 that is convex toward the steel plate 17 side is provided on the steel plate 18. No. 3 is No.3. Compared with 1 and 2, it can be seen that the joint strength is high, the penetration of the steel plate 18 is deeper, and a sound weld is obtained. In Table 1, No. 4 is an example of the present invention in which the protrusions 4 are formed on both the steel plate 17 and the steel plate 18 and these protrusions 4 and 4 are overlapped and welded. No. 4 is also No.4. Compared with 1 and 2, it can be seen that the joint strength is high, the penetration depth of the steel plate 18 is deeper, and a sound weld is obtained.

  The same steel plates 17 and 18 as in Example 1 were used, and the shape of the protrusion 4 was changed as shown in Table 2, and welding was performed under the same welding conditions as in Example 1. The results (the strength of the weld, the nugget diameter, and the penetration depth of the steel plate 18) are shown in Table 2 together with the specifications (shape, height, size, and top size) of the protrusions.

  No. in Table 2 Nos. 5 to 7 are examples of the present invention. In Nos. 5 and 6, the protrusion 4 has a spherical shape. Reference numeral 7 denotes a truncated cone shape. No. In any of the inventive examples 5 to 7, a high joint strength and a deep penetration depth of the steel plate 18 were obtained. In contrast, no. No. 8 is No. 7 is a comparative example in which the same protrusion as 7 is provided on the steel plate 17 in contact with the spot welding electrode tip 3 toward the steel plate 18 side, and the joint strength is low.

  Three steel plates were stacked and welded. The used steel plate is a steel plate having an upper steel plate 17 and an intermediate steel plate (not shown) having a thickness of 1.4 mm with a 590 MPa class, and a lower steel plate 18 having a thickness of 1.6 mm with a 590 MPa class. . The welding conditions are the same as in Example 1.

  After welding, the strength of the steel plate 18 and the intermediate steel plate was evaluated by a tensile test. The results (the strength of the weld, the nugget diameter, and the penetration depth of the steel plate 18) are shown in Table 3 together with the specifications (shape, height, and size) of the protrusion.

  No. in Table 3 No. 9 is an example of the present invention in which only the lower steel plate 18 is provided with the protrusion 4 directed toward the intermediate steel plate, and it can be seen that a high bonding strength was obtained. On the other hand, in Table 3, No. No. 10 is a comparative example in which any steel plate was welded without forming a protrusion, and the lower steel plate 18 and the intermediate steel plate were not joined.

  A welded structure member having a closed cross section composed of the first welded member 1 and the third member 5 having the structure shown in FIG. 1 is manufactured, and then the second welded member 2 and the first welded member. 1 was spot-welded on one side to evaluate the quality of the weld.

  First, a hat-type first welded member 1 made of a 590 MPa class galvannealed steel plate having a thickness of 1.8 mm, a length of 300 mm, a flange width of 20 mm, a depth of 80 mm, and a hat bottom width of 80 mm. And a third member 5 that is a closing member made of a 590 MPa class galvannealed steel plate having a thickness of 1.4 mm, a width of 120 mm, and a length of 300 mm, as shown in FIG. The flange portion 1b was joined by ordinary spot welding using a pair of spot welding electrode tips.

  The first member 1 to be welded is formed in advance by pressing so as to face the outer side of the bottom of the hat member, and the protrusion 4 on the curved surface having a bottom diameter of 10 mm and a height of 1 mm is formed. Two types were prepared which do not form a part.

  Next, a second welded member 2 having a rectangular shape of about 100 mm × about 50 mm and made of a 590 MPa class alloyed hot-dip galvanized steel sheet is overlaid as shown in FIG. 3 was pressed against the second member 2 to be welded from above to perform one-side spot welding.

  As a spot welding electrode tip in contact with the second member 2 to be welded, a chromium copper electrode having a tip radius of curvature of 100 mm and a thickness of 16 mm was used. The welding conditions were a pressurizing force of 588 kN, energization time of 15 cycles, and a current of 9 kA. Further, as shown in FIG. 1, an electrode 3 ′ was placed on the bottom surface of the hat-shaped third member 5 during welding.

After welding, a peeling test was performed by hitting the joining portion between the first welded member 1 and the second welded member 2 with a chisel, and the diameter of the welded portion remaining in a button shape was measured.
As a result, a button diameter of about 6 mm was obtained when the protrusion was present, and it was confirmed that the button was bonded well. On the other hand, when the protrusion was not provided, the first test was performed by a peel test. The member 1 to be welded and the second member 2 to be welded easily peeled off.

  The welded structure member 11 having the structure shown in FIGS. 7 and 8 is manufactured, and the weld quality of the welded portion between the first welded member 8 that is a reinforcing member and the second welded member 10 that is a closing member. Evaluated.

  First, the plate thickness is 1.6 mm, the length is 300 mm, the flange width is 20 mm, the depth is 80 mm, the hat bottom width is 80 mm, and it is made of a 590 MPa class galvannealed steel sheet. A hat-shaped third member 9 to be welded, a plate thickness of 1.6 mm, a square shape of about 75 mm × about 75 mm, a flange having a width of 20 mm by bending on each of four sides, and a 590 MPa class A first welded member 8 which is a reinforcing member made of an alloyed hot-dip galvanized steel sheet was produced.

  Next, the first member to be welded 8 is installed as a reinforcing member at the center in the longitudinal direction of the third member to be welded 9 as shown in FIGS. Three flanges in contact with the member 9 to be welded were joined by ordinary spot welding using a pair of spot welding electrode tips.

  In addition, the second member to be welded 10 which is a closing member made of a 590 MPa class galvannealed steel plate having a plate thickness of 1.2 mm, a width of 120 mm, a length of 300 mm and a 590 MPa class is shown in FIG. As shown in FIG.

  Next, one-side resistance spot welding was performed from the second welded member 10 side at a location where the first welded member 8 and the second welded member 10 are in contact. Here, the first member 8 to be welded is prepared in two types: one in which the protrusion 4 is formed on the flange 8a so as to be convex toward the second member 10 to be welded, and one in which the protrusion is not formed. did.

  As a spot welding electrode tip in contact with the second member to be welded 10, a chromium copper electrode having a tip radius of curvature of 100 mm and a thickness of 16 mm was used. The welding conditions were a pressure of 588 kN, energization time of 12 cycles, and a current of 10 kA. The protrusion 4 has a curved shape with a bottom portion having a size of 10 mm and a height of about 1 mm. Moreover, the electrode was installed in the bottom face of the hat-shaped 3rd to-be-welded member 9 in the case of welding.

The third welded member 9 is disassembled after welding, and a peel test is performed by hitting the joining portion between the first welded member 8 and the second welded member 10 with a chisel, and the diameter of the welded portion remaining in a button shape Was measured.
As a result, a button diameter of about 5 mm was obtained when the protrusion was present, and it was confirmed that the button was bonded well. On the other hand, when the protrusion was not provided, the first test was performed by a peel test. The member to be welded 8 and the second member to be welded 10 were easily separated. Moreover, the nugget was not formed in the junction location of the 1st to-be-welded member 8 and the 2nd to-be-welded member 10. FIG.

It is explanatory drawing which shows typically the point which enforces the manufacturing method of the welded structure member of Embodiment 2. FIG. It is explanatory drawing which shows typically the condition which performs normal resistance spot welding. While applying a pressure only from the side of the member to be welded without arranging a supporting member (for example, a back bar electrode or a back bar such as a block) on the side facing the spot welding electrode tip. It is explanatory drawing which shows typically the condition which performs one side resistance spot welding. A situation in which one-side resistance spot welding is typically performed by forming a protruding portion that protrudes toward the welded member that does not contact the spot welding electrode on the welded member that contacts the electrode tip for spot welding. It is explanatory drawing shown. It is explanatory drawing which shows the condition which forms the projection part which becomes convex toward the to-be-welded member side which the electrode for spot welding contacts on the to-be-welded member which the electrode tip for spot welding does not contact, and performs the one-side spot welding is there. It is explanatory drawing which shows the condition when one side spot welding is complete | finished. Fig.7 (a) is explanatory drawing which shows the structure of the welding structure member manufactured by Embodiment 3, and FIG.7 (b) is AA sectional drawing in Fig.7 (a). It is a perspective view which shows a welding structure member in a see-through state. It is explanatory drawing which shows the condition where the bending part of a flange contacts preferentially, a spark generate | occur | produces in the location, and welding becomes impossible. It is explanatory drawing which shows the condition which contacts on the end surface of a flange, a spark generate | occur | produces in the location, and welding becomes impossible. FIG. 10 is an explanatory view showing a welded structure member according to a fourth embodiment. It is explanatory drawing which shows the 1st to-be-welded member which is a reinforcement member comprised by joining two structural members by welding. It is explanatory drawing which shows the condition which enforces the welding method of the welding structure member of Embodiment 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 0 Welding structure member 1 1st to-be-welded member 1b, 1b Flange part 2 2nd to-be-welded member 3, 3-1, 3-2 Electrode tip 3 'for spot welding 3 Electrode 4 Projection part 5 6 energizing path 7 nugget 8 first welded member 8a, 8b flange 9 third welded member 9a bottom 9b flange 10 second welded member 11 welded structural member 12 first welded member 12a surface 13 welded structure Member 14, 16 Component member 17, 18 Steel plate 19 Support stand

Claims (5)

The second workpiece is contacted via a spot welding electrode tip that is in contact with the surface of the second member to be welded, which is in contact with the first member to be welded or overlaid via one or more welding members. A method of manufacturing a welded structural member in which the first welded member and the second welded member are welded by performing one-side resistance spot welding to energize the welded member,
The first welded member is a protrusion that protrudes toward the second welded member at a position opposite to the position of the second welded member with which the spot welding electrode tip abuts. A method for manufacturing a welded structure member, comprising: a step of supplying a current to the first welded member through the protrusion. The second member to be welded via a spot welding electrode tip that abuts on the surface of the second member to be welded, which is superimposed on the first member to be welded that forms a main body having a closed cross-sectional structure together with the third member. A method of manufacturing a welded structural member in which the first welded member and the second welded member are welded by performing one-side resistance spot welding to energize the welded member,
The first welded member is a protrusion that protrudes toward the second welded member at a position opposite to the position of the second welded member with which the spot welding electrode tip abuts. A method for manufacturing a welded structure member, comprising: a step of supplying a current to the first welded member through the protrusion. The second workpiece is placed via a spot welding electrode tip that is disposed to overlap the first workpiece and contacts the surface of the second member to be welded together with the third member and has a closed cross-sectional structure. A method of manufacturing a welded structural member in which the first welded member and the second welded member are welded by performing one-side resistance spot welding to energize the welded member,
The first welded member is a protrusion that protrudes toward the second welded member at a position opposite to the position of the second welded member with which the spot welding electrode tip abuts. A method for manufacturing a welded structure member, comprising: a step of supplying a current to the first welded member through the protrusion.   The method for manufacturing a welded structure member according to claim 3, wherein the first welded member is a reinforcing member that is disposed inside the main body and reinforces the main body.   The said projection part is a manufacturing method of the welded structure member described in any one of Claim 1- Claim 4 which has a shape where a cross-sectional area increases toward the bottom part from the top part.

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