JP2008045726A - Projection bolt for circular cross-section member, and its welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection bolt for a circular cross-section member, and its welding method ensuring sufficient welding strength and carrying out welding with no rust formation. <P>SOLUTION: The projection bolt 10 having a shank 11, a flange part 12 and a circular welding projection 13 is welded to the outer cylindrical surface 21 of the circular cross-section member 18. The flange part 12 is provided with a narrow part 16 formed by making a width dimension in the circumferential direction of the circular cross-section member 18 smaller than a flange part dimension in the axial direction of the circular cross-section member 18, and the height of the welding projection 13 is set to a value that can reduce a clearance between the surface 29 of the flange part 12 and the outer cylindrical surface 21 by recessing the outer cylindrical surface 21 of the circular cross-section member 18 when the welding projection 13 is melting. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a projection bolt for a circular cross-section member and a welding method thereof.

A projection bolt composed of a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion is formed into a flat steel plate component. It is known to weld by electric resistance welding.
JP-A-7-2223078

  In the welding as described above, the molten metal of the welding protrusion expands along the surface of the flat steel plate part, and therefore, by applying a predetermined pressure and melting, between the flange portion and the steel plate part. No voids are generated.

  However, when the projection bolt having the above-described configuration is welded to the outer cylindrical surface of an iron pipe member or a solid round bar member having a circular cross section, there are the following problems. This point will be described with reference to FIG. The projection bolt 1 includes a shaft portion 2 provided with a male screw as described above, a flange portion 3 provided integrally with the shaft portion 2, and a circular welding protrusion 4 provided at the center of the flange portion 3. It is composed of The welding projection 4 in FIG. 4A has a diameter that is substantially the same as the diameter of the shaft portion 2, and a thickness t that is set to be substantially the same as or thinner than the thickness of the flange portion 3. Yes.

  When the projection bolt 1 having such a welding protrusion 4 is electrically resistance-welded to the outer cylindrical surface 6 of the pipe material 5 as shown in FIG. Reference numeral 7 indicates a welded portion illustrated in black. In such normal welding, since the diameter of the welding projection 4 is substantially the same as the diameter of the shaft portion 2, the entire welding projection 4 is welded even if it is welded to the cylindrical outer cylinder surface 6.

  However, in the case of the projection bolt as shown in FIG. 5A, there is a problem that the gap 8 is formed from the welded portion 7 in the circumferential direction. The gap 8 gradually increases in size as the gap 8 moves away from the welded portion 7 in the circumferential direction. Further, the welding projection 4 of the projection bolt 1 shown in FIG. 5B is a flattened version of the welding projection 4 shown in FIG. When welded, since it is a cylindrical surface, the melted portion is limited to the central portion, and as shown in FIG.

  When such a gap 8 is formed, when the lateral force in FIG. 6C acts on the shaft portion 2, the shaft portion 2 is tilted to the left and right. Therefore, sufficient welding strength cannot be secured against such external force. Further, when the void 8 exists, impurities in the void portion are carbonized due to the heat of fusion and remain in the void 8, and carbides and the like cannot be removed even in the cleaning process, and thus rust is easily generated from this portion. There is a problem. When such a void portion is immersed in salt water and a rusting test is performed, it is confirmed that rusting occurs early. In addition, in the undercoating such as electrodeposition coating, the paint sealed into the gap 8 cannot be fully penetrated by the air sealed in the gap 8, so that the air enclosed after the overcoating is expanded and the so-called coating swelling is caused. Occurs and the coating film in this part is peeled off.

  The present invention has been provided to solve the above-mentioned problems, and aims to provide a projection bolt for a circular cross-section member capable of ensuring sufficient welding strength and capable of welding without rusting, and a welding method thereof. To do.

Means to solve the problem

  The invention according to claim 1 includes a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. And a projection bolt welded to the outer cylindrical surface of the circular cross-section member, wherein the flange portion has a narrow width in the circumferential direction of the circular cross-section member that is smaller than the flange size in the axial direction of the circular cross-section member. And the height of the welding projection is such that when the welding projection is melting, the outer cylindrical surface of the circular cross-section member is recessed to reduce the gap between the flange surface and the outer cylindrical surface. This is a projection bolt for a circular cross-section member, which is set to a value that can be used.

The invention's effect

  Since the welding current is initially energized after a predetermined time has passed after the welding projection is pressed onto the outer cylinder surface, the welding projection is recessed into the outer cylinder surface while achieving initial melting. And the space between the outer cylinder surface can be reduced. That is, a depression is formed in the outer cylinder portion by pressing the welding projection against the outer cylinder surface. When the dent phenomenon and melting of the welding protrusion proceed simultaneously, the gap further shrinks, and when the welding protrusion finally melts completely, the gap disappears and the surface of the flange portion becomes the outer cylindrical surface. To be in close contact with each other. The height of the welding projection, that is, the thickness, is set so that an indentation plastic deformation is imparted to the outer cylindrical surface and an appropriate welding depth is obtained by a predetermined amount of melting.

  Moreover, since the flange part length of the circumferential direction of a circular cross-section member becomes short by forming the said narrow part, the space | gap dimension between the outer-end part of a flange part and an outer cylinder surface is made small. Therefore, the surface of the flange portion is easily adhered to the outer cylinder surface, which is effective for eliminating the gap.

  Therefore, even if an external force in the circumferential direction of the circular cross-section member acts on the shaft portion of the welded projection bolt, the gap does not exist, so that the shaft portion is not inclined and sufficient welding strength can be ensured. Further, by eliminating the voids, it is possible to prevent the occurrence of rust as described above and peeling of the coating film.

  Furthermore, since the void is removed by making the outer cylinder surface concave, good void removal is performed for thin pipe materials and solid round bars with low hardness. Can do.

  A second aspect of the present invention is the projection bolt for a circular cross-section member according to the first aspect, wherein the welding projection has a diameter substantially equal to the diameter of the shaft portion.

  Since the diameter of the welding protrusion is set as described above, the surface pressure of the welding protrusion end surface with respect to the outer cylinder surface is increased, and thereby the depression to the outer cylinder surface, that is, the biting is reliably performed, The reduction in the size of the gap proceeds reliably.

  A third aspect of the present invention is the projection bolt for a circular cross-section member according to the first or second aspect, wherein the narrow portion is formed by cutting out both sides of a circular flange portion.

  Since it is a so-called oval shape with both sides of the circular flange portion cut off, it is easy to narrow the width over the circumferential direction, and the oval shape allows the axial direction of the circular cross-section member to be The directionality of the flange portion can be exactly matched to each of the circumferential directions.

  In the invention according to claim 4, the ratio of the dimension in the circumferential direction of the circular cross-section member to the dimension in the axial direction of the circular cross-section member is set to 0.7 to 0.5 on the current-carrying surface of the flange portion in close contact with the electrode end surface. The projection bolt for a circular cross-section member according to any one of claims 1 to 3.

  The end surface of the electrode is in close contact with the flange surface opposite to the welding projection, and the welding current is supplied. It is important for good welding that the current-carrying surface is properly secured. Since the ratio is set to 0.7 to 0.5, a sufficient conduction area in the width direction of the narrow portion (circumferential direction of the circular cross-section member) can be secured, and the welding current over the entire circumference of the welding protrusion. The current density can be ensured uniformly. If the conduction area in the width direction of the narrow width part (circumferential direction of the circular cross-section member) cannot be secured sufficiently, the current density in this part cannot be secured properly due to the lack of the conduction area in this part, and welding Variations in the heat generation distribution over the entire circumference of the projection for use will result in failure to form a normal initial melt. Further, the pressing force from the electrode to the flange portion is surely applied, and an uneven load is not applied in the pressurizing and melting processes.

  The invention according to claim 5 includes a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. In addition, a projection bolt welded to the outer cylindrical surface of the circular cross-section member is prepared, and the width of the circular cross-section member in the circumferential direction is smaller than the flange dimension in the axial direction of the circular cross-section member at the flange portion. The gap between the surface of the flange portion and the outer cylinder surface is reduced by pressing the welding projection on the circular cross-section member and denting the outer cylinder surface of the circular cross-section member, and proceeds with this pressurization. A welding method for a projection bolt for a circular cross-section member, wherein the gap is eliminated by melting the welding projection to be adhered and the surface of the flange portion is brought into close contact with the outer cylindrical surface.

  The operational effects of the present welding method are the same as the operational effects of the invention of the projection bolt according to claim 1.

  The above-mentioned invention is a case where it is easy to dent by pressurizing the welding protrusion, such as a thin pipe material or a solid round bar material with low hardness. The gap is erased. On the other hand, the invention described below is an invention suitable for the case of a pipe material having a large thickness or a solid round bar material having a high hardness without the ease of depression as described above.

  The invention according to claim 6 includes a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. And a projection bolt welded to the outer cylindrical surface of the circular cross-section member, wherein the flange portion has a narrow width in the circumferential direction of the circular cross-section member that is smaller than the flange size in the axial direction of the circular cross-section member. The volume of the welding projection is a value that allows the molten material of the welding projection to flow in the circumferential direction of the circular cross-section member and fill the gap between the surface of the flange portion and the outer cylinder surface This is a projection bolt for a circular cross-section member.

  When the welding projection is pressurized to the outer cylinder surface and a welding current is applied, the welding projection is melted and the gap between the surface of the flange portion and the outer cylinder surface is reduced. Simultaneously with the reduction of the gap, the molten metal flows in the circumferential direction of the circular cross-section member, filling the gap. The volume, that is, the thickness of the welding protrusion is set to a value that allows the molten material to flow in the circumferential direction and fill the gap.

  Moreover, since the flange part length of the circumferential direction of a circular cross-section member becomes short by forming the said narrow part, the space | gap dimension between the outer-end part of a flange part and an outer cylinder surface is made small. Therefore, the molten metal is easily filled in the gap, which is effective for eliminating the gap.

  Therefore, even if an external force in the circumferential direction of the circular cross-section member acts on the shaft portion of the projection bolt, there is no gap, so that the shaft portion is not inclined and sufficient welding strength can be ensured. Further, by eliminating the voids, it is possible to prevent the occurrence of rust as described above and peeling of the coating film.

  Furthermore, since void removal is performed using the flow of molten metal, good void removal can be performed for thick pipe materials, solid round bars with high hardness, and the like.

  A seventh aspect of the present invention is the projection bolt for a circular cross-section member according to the sixth aspect, wherein the diameter of the welding protrusion is substantially the same as the diameter of the shaft portion.

  Since the diameter of the welding protrusion is set as described above, the surface pressure of the welding protrusion end surface with respect to the outer cylinder surface is increased, thereby favorably starting the flow of the molten metal in the circumferential direction, The erasure of the void proceeds reliably.

  The invention according to claim 8 is the projection bolt for the circular cross-section member according to claim 6 or 7, wherein the narrow portion is formed by cutting out both sides of the circular flange portion.

  Since it is a so-called oval shape with both sides of the circular flange portion cut off, it is easy to narrow the width over the circumferential direction, and the oval shape allows the axial direction of the circular cross-section member to be The directionality of the flange portion can be exactly matched to each of the circumferential directions.

  According to the ninth aspect of the present invention, the ratio of the dimension in the circumferential direction of the circular cross-section member to the dimension in the axial direction of the circular cross-section member is set to 0.7 to 0.5 on the current-carrying surface of the flange portion closely contacting the electrode end surface. It is the projection bolt for circular cross-section members in any one of Claims 6-8.

  The end surface of the electrode is in close contact with the flange surface opposite to the welding projection, and the welding current is supplied. It is important for good welding that the current-carrying surface is properly secured. Since the ratio is set to 0.7 to 0.5, a sufficient conduction area in the width direction of the narrow portion (circumferential direction of the circular cross-section member) can be secured, and the welding current over the entire circumference of the welding protrusion. The current density can be ensured uniformly. If the conduction area in the width direction of the narrow width part (circumferential direction of the circular cross-section member) cannot be secured sufficiently, the current density in this part cannot be secured properly due to the lack of the conduction area in this part, and welding is performed. Variations in the heat generation distribution over the entire circumference of the projection for use will result in failure to form a normal initial melt. Further, the pressing force from the electrode to the flange portion is surely applied, and an uneven load is not applied in the pressurizing and melting processes.

  The invention according to claim 10 has a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. In addition, a projection bolt welded to the outer cylindrical surface of the circular cross-section member is prepared, and the width of the circular cross-section member in the circumferential direction is smaller than the flange dimension in the axial direction of the circular cross-section member at the flange portion. A projection for a circular cross-section member that fills the gap between the surface of the flange portion and the outer cylinder surface by providing a portion and causing the molten material of the welding protrusion to flow in the circumferential direction of the circular cross-section member It is a welding method of a bolt.

  The operational effects of the present welding method are the same as the operational effects of the invention of the projection bolt according to claim 6.

  Next, the best mode for carrying out the projection bolt for a circular cross-section member of the present invention and its welding method will be described.

  FIG. 3 shows the projection bolt welded in the first embodiment. In the following description, the projection bolt may be simply expressed as a bolt.

  The iron projection bolt 10 includes a shaft portion 11 provided with a male screw, a flange portion 12 provided integrally with the shaft portion 11, and a circular welding protrusion 13 provided at the center of the flange portion 12. Have. The end surface of the welding protrusion 13 is a spherical surface 14.

  The dimensions of each part of the bolt 10 are as follows.

The diameter of the shaft portion 2 is 6 mm (mountain diameter 6 mm, valley diameter 5 mm), the thickness of the flange portion 12 is 1.2 mm, the diameter of the base portion on the flange side of the welding projection 13 is 6.5 mm, and the welding projection 13 The diameter of the spherical surface 14 is 5.7 mm, the height dimension of the welding projection 13 is 1.3 mm, the radius of the spherical surface 14 is 130 to 150 mm, and the volume of the welding projection 13 is 38 mm ³ .

  As will be described later, the circular cross-sectional member is a hollow pipe member having a circular cross section or a solid round bar member having a circular cross section, and has an axis (OO) in its longitudinal direction.

  In FIG. 3B, the vertical direction in the figure is the axial direction of the circular cross-section member, and the horizontal direction in the figure is the circumferential direction of the circular cross-section member. The flange portion 12 is circular, and both sides thereof are cut out in a straight line shape to form an oval shape. The excision is indicated by reference numeral 15. By cutting in this way, the narrow portion 16 is formed, and the linear cut portion 15 is in the same direction as the axial direction of the circular cross-section member. The circular portion of the flange portion 12, that is, the dimension of L is 13 mm, and the width W of the narrow portion 16 (circumferential direction of the circular cross-section member) is 10.5 mm.

  Further, the flange surface opposite to the side on which the welding protrusion 13 is formed is a current-carrying surface 17 in close contact with the electrode end surface. In the energization surface 17, the ratio of the dimension W1 in the circumferential direction of the circular cross-section member to the dimension L1 in the axial direction of the circular cross-section member is set to 0.64. That is, the ratio 0.64 is set by W1 / L1 = 2.25 mm / 3.5 mm.

  The ratio is preferably set between 0.7 and 0.5. If this ratio exceeds 0.7, the length of the flange portion in the circumferential direction becomes excessive, the gap between the outer cylinder surface 21 becomes too wide, and it becomes difficult to eliminate the gap. If this ratio is less than 0.5, the dimension of the conductive surface 17 in the circumferential direction becomes too small, and it becomes difficult to ensure a normal energization area of the welding current.

  The bolt 10 has the narrow portion 16 formed by the cut portion 15 as described above, but this is an expression for explanation, and in actuality, an oval female shape is formed on the mold. It is manufactured by plastic working.

  In addition, as shown with a dashed-two dotted line in FIG.3 (D), the case where the surface of the flange part 12 is the gentle taper surface 9 may be sufficient. The spherical surface 14 may be a tapered surface 19 having a gentle inclination angle. The state of contact with the outer cylindrical surface of the circular cross-section member, whether it is the spherical surface 14 or the tapered surface 19, is point contact or surface contact close thereto, and it is possible to increase the current density at the initial stage of energization. .

  A state in which the bolt 10 having the above dimensions is welded to the pipe material 18 will be described with reference to FIG. The pipe member 18 used here is a member for reinforcing body rigidity that is installed between the left and right front pillars of the automobile body.

  Here, the circular cross-section member is a hollow pipe member 18 made of steel, the outer diameter thereof is 60 mm, and the thickness of the plate member is 2 mm. As shown in FIG. 1, the projection bolt 1 is welded to a straight pipe member 18 made of steel. The axis of the pipe member 18 is indicated by the symbol OO. As shown in FIG. 1D, positioning is performed so that the axis OO of the pipe member 18 and the width direction of the narrow portion 16 (circumferential direction of the pipe material 18) are orthogonal to each other, and welding is performed. By pressurizing and energizing the protrusion 13 to the outer cylindrical surface 21 of the pipe member 18, the welding protrusion 13 and a part of the pipe member 18 are melted by Joule heat and welded.

  Either the spherical surface 14 or the tapered surface 19 of the welding protrusion 13 makes point contact with the outer cylindrical surface 21. When the welding protrusion 13 is pressed against the outer cylindrical surface 21, the point contact exhibits surface contact close to point contact. In addition, by forming a slightly round flat portion at the sharp apex 32 of the tapered surface 19 shown in FIG. 3D, it is easy to perform mold molding so as not to reduce the current density of the welding current. can do.

  In order to perform such pressurization and welding current application, a receiving hole 23 is provided at the center of the rod-like movable electrode 22 that moves forward and backward, and a permanent magnet 24 that holds the bolt 1 is fixed at the back thereof. ing. The shaft portion 11 is inserted into the receiving hole 23 and is further attracted by the permanent magnet 24, so that the bolt 10 is held by the movable electrode 22. The fixed electrode 25 is a V-block type that can support the pipe material 18 in a stable state, and the pipe material 18 is placed on a V-groove portion 27 formed by left and right inclined surfaces 26 and 26. Yes. The relative positions of the movable electrode 22 and the pipe material 18 are set so that the axis XX of the movable electrode 22, that is, the axis of the shaft portion 11 is orthogonal to the axis OO of the pipe material 18.

  The pipe member 18 shown in FIG. 1 has a straight shape, but may be curved depending on the application of the pipe member 18.

  FIG. 1A shows that the movable electrode 22 holding the bolt 10 has advanced with respect to the pipe material 18 placed on the fixed electrode 25, and the spherical surface 14 of the welding projection 13 is pressed against the outer cylinder surface 21. It is a state that has been. In this state, the central portion of the spherical surface 14 is in point contact with or close to the outer cylindrical surface 21. Thereafter, when energization of pressurization and welding current proceeds, welding is performed as shown in FIGS.

  FIG. 1 (E) shows a case where the circular cross-section member is formed of a solid round bar, and the process in which the outer cylinder portion is deformed and welded is described with reference to FIG. It is the same.

  The welding process will be described with reference to FIG.

  The dimensions of each part of the used bolt 10 are as described above, and the pipe material 18 has the dimensions described in FIG. The applied pressure applied from the movable electrode 22 is 200 kgf, the current value is 9200 amperes, and the energization time is 15 cycles (1 cycle = 1/60 seconds).

  FIG. 2A shows a state in which the movable electrode 22 has advanced and its flat end face is in close contact with the conducting surface 17 of the flange portion 1, and the spherical surface 14 of the welding projection 13 is pressed against the outer cylindrical surface 21. The initial stage of energization of the welding current. At this stage, the portion of the welding protrusion 13 starts to bite into the outer cylindrical surface 21 by the pressure applied from the welding protrusion 13. When the depression of the welding projection 13 is started, the spherical surface 14 of the welding projection 13 is also slightly melted, so that the steel plate of the pipe material 18 is easily softened, and the biting is performed. Promoted. The weld formed in this way is shown in black and is indicated by the reference numeral 20. However, at this stage, the gap C1 between the surface 29 of the flange portion 12 and the outer cylindrical surface 21 remains as a large value, and is specifically observed to be about 1.0 mm.

  In addition, although “bite” and “dent” are used as terms in this description, both are synonymous and mean that the plate material of the pipe material 18 is dented by the advancement of the welding protrusion 13. is doing. Due to such depressions, a slight bulge 28 is formed inside the pipe member 18.

  Next, when pressurization and energization further progress, as shown in FIG. 2B, softening of the pipe material 18 progresses, and the biting phenomenon due to the welding projections 13 also progresses. At this time, melting has also progressed to the pipe material 18 side, but about 1/2 of the height of the welding projection 13 becomes a molten metal, and the melting range becomes large over both width and depth. As the amount of biting increases, the gap C1 changes to a reduced gap C2 as shown in FIG. Since the depression of the welding protrusion 13 becomes large, the bulging amount of the bulging portion 28 is larger than that in FIG. (B) The bulging amount I in the figure is mainly caused by the state in which the molten metal of the welding projection 13 or the molten metal of the pipe material 18 expands in the surface direction, the size of the remaining gap C2, and the like. However, it is observed that the bulge amount 1 is in the range of about 0.7 mm to 1.0 mm in the stage of FIG.

  Next, at the stage shown in FIG. (C), since the pressurization and melting reach the final stage, the melt width in the surface direction and the melt depth in the thickness direction of the welded portion 20 are further expanded, and bulges with it. The bulging amount I of the portion 28 is also the maximum value. By such pressurization and melting, the gap C2 in FIG. (B) disappears as shown in FIG. That is, the surface 29 of the flange portion 12 is in close contact with the outer cylindrical surface 21. Here, as described above, since sufficient pressurizing force is applied for a long time, as indicated by reference numeral 31, the corner portion of the cut portion 15 is in a state of biting into the outer cylindrical surface 21. Therefore, the welding part 20 is reliably formed in the center part of the flange part 12, and the space | gap C2 is erase | eliminated in the press-contact state.

  (C) In the final stage as shown in the figure, as is clear from the comparison between the figures (B) and (C), the fusion area is larger than the area of the welding projections 13 and stable welding is achieved. It is recognized that it is formed. Further, the bulging amount I of the bulging portion 28 in FIG. 8C was in the range of about 0.9 mm to 1.2 mm. And (D) figure is the figure which cut the pipe material 18 in half and it was the figure seen from the inside, and identifies the bulging part 28 and the welding part 20 which received the heat influence from the bulging shape and the mode of discoloration. can do.

  FIG. 2E is a cross-sectional view of the welded portion cut along the axis OO direction of the pipe material 18. As is apparent from this figure, the welding in the direction orthogonal to the circumferential direction of the pipe member 18 is normally performed over the entire longitudinal direction of the flange portion 12.

  The effects of the first embodiment are listed as follows.

  After pressurizing the welding projection 13 to the outer cylindrical surface 21 of the pipe material 18, when a predetermined time elapses, initial welding current is applied, so that the welding projection 13 performs the initial melting while the pipe material 18 is kept inside. So that the gap C1 between the surface 29 of the flange portion 12 and the outer cylinder surface 21 can be reduced. That is, when the welding projection 13 is pressed against the outer cylindrical surface 21, a depression is formed in the plate material of the pipe material 18. When the dent phenomenon and the melting of the welding protrusion 13 proceed simultaneously, the gap is further reduced to become the gap C2, and when the welding protrusion 13 is finally melted, the gap disappears and the flange portion 12 is removed. Is brought into close contact with the outer cylindrical surface 21. The height, that is, the thickness of the welding protrusion 13 is set so that an indentation plastic deformation is imparted to the outer cylindrical surface 21 and an appropriate welding depth is obtained by a predetermined melting amount.

  Moreover, since the flange part length of the circumferential direction of the pipe material 18 becomes short by forming the said narrow part 16, the space | gap dimension (from C1) between the outer-end part of the flange part 12, and the outer cylinder surface 21 is shortened. Is slightly smaller). Accordingly, the surface 29 of the flange portion 12 is easily adhered to the outer cylinder surface 21, which is effective in eliminating the gap.

  Therefore, even if an external force in the circumferential direction of the pipe material 18 acts on the shaft portion 11 of the welded projection bolt 10, the gap does not exist, so that the shaft portion 11 is not inclined and sufficient welding strength is ensured. it can. Further, by eliminating the voids, it is possible to prevent the occurrence of rust as described above and peeling of the coating film.

  As a result of cleaning the test piece having no gap in this way, it was confirmed that no impurities remained in the peripheral portion of the flange portion 12. The cleaning liquid used here is a cleaning liquid used in the cleaning process of the white body of an automobile. In addition, as a result of conducting a rusting test for 24 hours by applying salt water to the bolt welded portion of the unpainted pipe material 18 washed in this manner, no rusting was observed. Furthermore, the throwing power of the electrodeposition coating at the bolt welded portion was good, and a top coating without air bulging or peeling was achieved.

  A tensile tester as shown in FIG. 4 was prepared and a tensile test was performed. In the testing machine 33, the support pieces 35 are firmly attached to the left and right stationary members 34, and the outer cylindrical surface 21 of the pipe material 18 is brought into close contact with the receiving surface 36. In this state, the test is performed by pulling up the pulling piece 37 into which the shaft portion 11 is screwed in the direction of the arrow line 38. As a result, the trough diameter portion of the shaft portion 2 was broken by a pulling load of 1.4 tons. This confirms that the M6 bolt has a welding strength in the pulling direction that exceeds that at which the M6 bolt breaks.

  Further, as a result of smashing the tip end portion of the shaft portion 11 of the welded bolt 10 over the axial direction and the circumferential direction of the pipe member 18 with a hammer, the shaft portion 11 was bent without being able to endure, but the pipe of the flange portion 12 No change was observed in the relative position to the material 18.

  Furthermore, since the gap is removed by making the plate material of the pipe material 18 hollow, good void removal is targeted for the thin pipe material 18 or the solid round bar material with low hardness. It can be performed.

  The diameter of the welding protrusion 13 is approximately the same as the diameter of the shaft portion 11.

  Since the diameter of the welding protrusion 13 is set as described above, the surface pressure of the end face of the welding protrusion with respect to the plate material of the pipe material 18 is increased, so that the depression into the outer cylindrical surface 21 is reliably performed. The reduction in the amount of the gap proceeds reliably.

  The narrow portion 16 is formed by cutting out both sides of the circular flange portion 12.

  Since the shape of the circular flange portion 12 is cut off on both sides and is a so-called oval shape, the width of the pipe material 18 can be easily reduced in the circumferential direction. The directionality of the flange portion 12 can be exactly matched to each of the axis OO direction and the circumferential direction. Further, such an oval shape can be easily obtained by mold molding, which is effective for improving productivity.

  The ratio of the dimension in the circumferential direction of the pipe material 18 to the dimension in the axial direction OO of the pipe material 18 is set to 0.7 to 0.5 for the current-carrying surface 17 of the flange portion 12 that is in close contact with the electrode end surface. .

  The end surface of the movable electrode 22 is in close contact with the flange surface on the side opposite to the welding protrusion 13 so that a welding current is applied. It is important for good welding that the current-carrying surface 17 is normally secured. Since the said ratio is set to 0.7-0.5, the conduction | electrical_connection area in the width direction (circumferential direction of the pipe material 18) of the narrow part 16 can fully be ensured, and the perimeter of the welding protrusion 13 is sufficient. A uniform current density of welding current can be ensured. If the conduction area in the width direction of the narrow portion 16 (circumferential direction of the pipe material 18) cannot be secured sufficiently, the current density in this portion cannot be secured properly due to the lack of the conduction area of this portion, Variations in the heat generation distribution over the entire circumference of the welding protrusion 13 occur, and normal initial melting is not formed. In addition, the applied pressure from the movable electrode 22 to the flange portion 12 acts reliably, and an unbalanced load does not act during the pressurization or melting process.

  The invention according to claim 5 includes a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. In addition, a projection bolt welded to the outer cylindrical surface of the circular cross-section member is prepared, and the width of the circular cross-section member in the circumferential direction is smaller than the flange dimension in the axial direction of the circular cross-section member at the flange portion. The gap between the surface of the flange portion and the outer cylinder surface is reduced by pressing the welding projection on the circular cross-section member and denting the outer cylinder surface of the circular cross-section member, and proceeds with this pressurization. A welding method for a projection bolt for a circular cross-section member, wherein the gap is eliminated by melting the welding projection to be adhered and the surface of the flange portion is brought into close contact with the outer cylindrical surface.

  The effect of the invention of the present welding method is the same as the effect of the invention of the projection bolt described above.

  FIG. 5 shows a second embodiment.

  Example 1 is a case where a depression can be easily formed by pressurizing a welding protrusion, such as a thin pipe material or a solid round bar material with low hardness, and such depression deformation is utilized. The voids are erased.

  On the other hand, Example 2 described below does not have the tendency to dent as described above, and is suitable for a thick pipe material or a solid round bar material with high hardness. Therefore, Example 1 and Example 2 have the same aim of eliminating the gap, but are different in the melt deformation state of the welding protrusion 13 by pressurization / energization.

  The pipe member 18 shown in FIG. 5 has a thickness of 4 mm, and is hardly depressed by the normal pressure of the welding protrusion 13. The other dimensions of the bolt 10, the outer diameter of the pipe material 18, the structure of the movable electrode 22, and the pressurization energization conditions are the same as in the previous embodiment.

  In FIG. 5A, the spherical surface 14 is pressed against the outer cylindrical surface to make point contact or surface contact close thereto. When pressurization and energization are performed here, melting starts from the center of the spherical surface 14, and the spherical surface 14 melts at the initial stage of energization, as shown in FIG. As this melting, the liquid metal or the fluidized metal softened by high heat moves in the circumferential direction as indicated by reference numeral 39. At this stage, the gap C1 is reduced to C2.

  Further, when the pressurization and the energization are continued, as shown in FIG. (C), the amount of the fluid metal is increased by completely melting the welding projection 13 and, at the same time, the gap C2 is C3. Therefore, the fluidized metal 39 behaves so as to fill the space C3 from the inside.

  Then, when the pressurization and energization reach the final stage, the fluid metal 39 is strongly sandwiched between the flange portion 12 and the outer cylindrical surface 21 as shown in FIG. It will be in the state extruded to the edge part of the part 12, and a space | gap is filled up.

  FIG. 5E is a cross-sectional view of the pipe member 18 cut in the axial direction. In this direction, the welded portion 20 is formed over the entire length of the flange portion 12.

  As can be seen from FIGS. (C) and (D), a slight bulging portion 28 occurs even in the thick pipe material 18. Such a phenomenon is because the local portion of the pipe material 18 is softened at a high temperature, but it is determined that this degree of swelling does not affect the behavior of the fluid metal 39.

The volume of the welding protrusion 13 is 38 mm ³ , but when the diameter of the pipe material 18 is reduced from 60 mm in the embodiment to, for example, 40 mm, the height of the welding protrusion 13 is increased to increase the volume. For example, it is desirable to increase the gap to 45 mm ³ so that the widened gap can be easily filled.

  In Example 2, since the voids are removed using the flow of the molten metal, good voids are removed for thick pipe materials, solid round bars with high hardness, and the like. be able to.

  Other functions and effects are the same as those of the first embodiment.

  As described above, according to the present invention, since the projection bolt for a circular cross-section member capable of ensuring sufficient welding strength and capable of welding without rusting and the welding method thereof, the vehicle body welding process of an automobile and home electrification are provided. It can be used in a wide range of industrial fields such as sheet metal welding processes for products.

It is sectional drawing and a top view which show the state in which it is bolt-welded. It is sectional drawing which shows a welding process. It is each part external view of the volt | bolt in an Example. It is a side view which shows the testing machine of a tension test. It is sectional drawing which shows the welding process in another Example. It is a figure which shows a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Projection bolt 11 Shaft part 12 Flange part 13 Welding protrusion 15 Cut part 16 Narrow part 17 Current supply surface 18 Pipe material 20 Welding part C1 Cavity C2 Cavity C3 Cavity OO Pipe material axis XX Axis of movable electrode, Shaft portion axis 21 Outer cylindrical surface 22 Movable electrode 28 Swelling portion 29 Flange portion surface 30 Void 39 Fluid metal

Claims (10)

  The outer cylinder of the circular cross-section member has a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. A projection bolt welded to a surface, wherein the flange portion is provided with a narrow portion in which a circumferential width dimension of the circular cross-section member is smaller than a flange dimension in the axial direction of the circular cross-section member; Is set to a value that can reduce the gap between the surface of the flange portion and the outer cylinder surface by denting the outer cylinder surface of the circular cross-section member when the welding projection is melting. A projection bolt for a circular cross-section member.   The projection bolt for a circular cross-section member according to claim 1, wherein a diameter of the welding protrusion is substantially the same as a diameter of the shaft portion.   The projection bolt for a circular cross-section member according to claim 1 or 2, wherein the narrow portion is formed by cutting out both sides of a circular flange portion.   The current-carrying surface of the flange portion that is in close contact with the electrode end surface has a ratio of the dimension in the circumferential direction of the circular cross-section member to the dimension in the axial direction of the circular cross-section member set to 0.7 to 0.5. The projection bolt for circular cross-section members according to any one of Items 3.   The outer cylinder of the circular cross-section member has a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. A projection bolt to be welded to the surface, and the flange portion is provided with a narrow portion in which a circumferential width dimension of the circular cross-section member is smaller than a flange dimension in the axial direction of the circular cross-section member, and the welding protrusion The circular cross-section member is pressed to reduce the outer cylinder surface of the circular cross-section member, thereby reducing the gap between the surface of the flange portion and the outer cylinder surface. A welding method for a projection bolt for a circular cross-section member, wherein the gap is eliminated and the surface of the flange portion is brought into close contact with the outer cylinder surface.   The outer cylinder of the circular cross-section member has a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. A projection bolt welded to a surface, wherein the flange portion is provided with a narrow portion in which a circumferential width dimension of the circular cross-section member is smaller than a flange dimension in the axial direction of the circular cross-section member; The volume of the welding projection is set to a value that allows the molten material of the welding protrusion to flow in the circumferential direction of the circular cross-section member and fill the gap between the flange surface and the outer cylindrical surface. Projection bolt for circular section member.   The projection bolt for a circular cross-section member according to claim 6, wherein a diameter of the welding protrusion is substantially the same as a diameter of the shaft portion.   The projection bolt for a circular cross-section member according to claim 6 or 7, wherein the narrow portion is formed by cutting out both sides of a circular flange portion.   The ratio of the circumferential dimension of the circular cross-sectional member to the axial dimension of the circular cross-sectional member of the energizing surface of the flange portion that is in close contact with the electrode end surface is set to 0.7 to 0.5. Item 9. The projection bolt for a circular cross-section member according to any one of Items 8.   The outer cylinder of the circular cross-section member has a shaft portion provided with a male screw, a flange portion provided integrally with the shaft portion, and a circular welding protrusion provided in the center of the flange portion. A projection bolt to be welded to the surface, and the flange portion is provided with a narrow portion in which a circumferential width dimension of the circular cross-section member is smaller than a flange dimension in the axial direction of the circular cross-section member, and the welding protrusion The molten material is caused to flow in the circumferential direction of the circular cross-section member to fill the gap between the surface of the flange portion and the outer cylinder surface.

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