JP3569856B2 - Stud welding method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stud welding method using a metal welding dowel used for a connecting member between a steel part and a concrete part.
[0002]
[Prior art]
When combining steel and concrete parts to form a composite structure of steel and concrete, such as when forming a concrete floor on a steel beam of a building or a concrete floor on a steel bridge, A welding dowel made of metal is generally used as a connecting member for firmly connecting the two.
The welding dowel has a structure in which a welding part is provided at the tip of a rod-shaped shaft part with an enlarged head, and it is fixed to a steel part at predetermined intervals by stud welding, and concrete is placed on it. Forming part. The welded dowel fixed to the steel part of the formed composite structure of steel and concrete has the function of resisting the tensile stress in the axial direction of the concrete at the head, and the shaft part resisting the shear stress of the concrete. Has the function of resisting.
[0003]
However, such a welding dowel in which the cross-sectional area of the shaft portion and the welded portion provided at the end thereof are the same in size has a problem in that the support characteristics against shear stress are not sufficient. That is, the properties required for the shear stress of the welding dowel are that the welded portion to the steel portion is not broken and that the amount of breaking deformation of the shaft portion is sufficiently large. However, in the above-mentioned welding dowel, if the cross-sectional area of the shaft is increased to increase the fracture resistance of the welded portion, the rigidity of the shaft is increased and the amount of fracture deformation is insufficient, and the concrete portion is damaged, such as cracking. Cause. Conversely, when the cross-sectional area of the shaft portion is reduced to increase the amount of fracture deformation, the fracture strength of the welded portion is reduced and the bonding strength between the steel portion and the concrete portion is reduced.
As a solution to such a problem, a welding dowel comprising a shaft portion and a welding portion having a larger cross-sectional area than the shaft portion has been proposed. (JP-A-5-156720)
[0004]
This is because, as compared with the shear fracture of a general welding dowel whose shaft portion has the same diameter up to the tip as shown in FIG. It is a demonstration. Then, a welding dowel 1 having the same diameter up to the tip of the shaft as shown in FIG. 8 is stud-welded to the material 2 to be welded, and a welding dowel 1 having an enormous tip as shown in FIG. When the resistance to shear fracture of the stud-welded steel 2 was measured, the characteristics were as shown in FIG. That is, according to the characteristics of the welding dowel of FIG. 8 shown by the dotted line and the characteristics of the welding dowel of FIG. 9 shown by the solid line, the initial rigidity of the welding dowel of FIG. 9 is greatly increased and the maximum proof stress is slightly increased. In addition, the shear failure becomes a form of tensile failure, and the failure mode becomes ductile fracture. Further, since the shear fracture is a tensile fracture and a fracture at the shaft portion, the fatigue resistance is also improved.
It is known that the shear deformation (deformability) at the time of destruction is substantially the same. Further, in the range where the shearing force is small, the improved welding dowel of FIG. 9 also has a feature that the amount of deformation is smaller. And in the welding dowel of FIG. 8, the shear fracture part appears in a welding part.
[0005]
[Problems to be solved by the invention]
However, although the proposed welding dowel has improved support properties against shear stress, it introduces a new problem that the welding dowel must be configured in a special shape. That is, there is a drawback that the material to be used increases and a process for enlarging the tip of the shaft portion of the welding dowel is required, so that a significant cost increase cannot be avoided.
Accordingly, an object of the present invention is to provide a stud welding method capable of improving the support characteristics against shear stress and solving such a structural problem of the welding dowel.
[0006]
[Means for Solving the Problems]
That is, the present invention is a stud welding method in which a metal welding dowel 1 having a shaft portion 3 and a welding portion 4 is gripped by a stud welding machine 20 and fixed to a workpiece 2 by welding.
This method has a flat bottom surface 9 and a recess 22 in which a through hole 10 or a bottom portion 23 having a thickness enough to melt and penetrate during arc stud welding remains. A metal enlarged block body 7 having a size such that the recessed portion 22 does not generate an arc between the shaft portion 3 and the welded portion 4 of the welding dowel 1 at the time of arc stud welding but can be welded to the welding dowel 1 is prepared. And the bottom surface 9 of the enlarged block body 7 is arranged in contact with the surface of the workpiece 2.
[0007]
Further, an inert gas supply jig (11) having an insertion hole (12) through which the welding dowel (1) is inserted and blowing out an inert gas from the bottom is provided with a through hole (7) of the enlarged block body (7). 10) or the recess (22), and insert the welded part (4) of the welding dowel (1) inserted through the insertion hole (12) into the through hole (10) or the recess (22). Then, the tip is brought into contact with the surface of the material to be welded (2) or the surface of the bottom (23) . Next, in this state, the inert gas is supplied from the inert gas supply jig (11) into the through hole (10) or the recess (22), and the stud welding machine (20) is started to perform stud welding. Thus, the welding dowel (1) is fixedly welded to the workpiece (2) and the enlarged block (7).
In a preferred embodiment of the above method, an inert gas supply jig (11) is pressed against the upper surface of the jig (11) by a pressing body (17) connected to a stud welding machine (20).
[0008]
In another preferred embodiment of the above-described method, a gap 12 a for flowing gas is provided between the insertion hole 12 of the inert gas supply jig 11 and the shaft 3 of the welding dowel 1.
In still another preferred embodiment of the above method, at least the periphery of a portion of the welding dowel 1 inserted into the through hole 10 or the recess 22 of the enlarged block body 7 is covered with the flux layer 6a.
In still another preferred embodiment, an amorphous foil 24 or an amorphous powder is applied or sprayed on the bottom surface 9 of the enlarged block body 7. Diffusion welding is performed between the bottom surface 9 of the enlarged block body 7 and the workpiece 2 due to the amorphous state.
[0009]
[Action]
According to the stud welding method of the present invention, despite the simple structure of the welding dowel, the same effect as that described in the above-mentioned JP-A-5-156720, that is, with respect to the expected maximum shear stress, This has the effect that the welded portion is not broken, and the amount of breakage deformation of the shaft can be sufficiently increased.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a partially cutaway front view for explaining a stud welding method of the present invention, and FIG. 2 is an exploded perspective view showing a main part thereof. In these figures, first, each component used in the stud welding method of the present invention will be described. The welding dowel 1 is made by cutting or forging a metal material such as steel, for example, and the shaft portion 3 and the welding portion 4 are aligned with the axis. They are integrally formed in order in the direction. Further, a head 5 having a larger cross-sectional area is integrally formed at the end of the shaft 3 opposite to the weld 4. In addition, these can also be mutually fixed by welding. Further, the shaft 3 and the weld 4 other than the head 5 may be integrally formed by cutting, and the head 5 may be welded thereto.
[0011]
The shaft 3, the weld 4, and the head 5 of the welding dowel 1 are formed rotationally symmetric with respect to the axis. However, the cross section of the shaft 3 or the head 5 may be, for example, a rectangle such as a square, or a polygon such as a pentagon or a hexagon.
Further, the welded portion 4 has a truncated conical shape whose cross section decreases toward the tip, and a hemispherical recess is formed at the center of the tip, and a spherical electrode 6 made of, for example, aluminum is driven into the recess. It is fixed. The ratio between the diameter and the length of the shaft 3 is preferably about 1: 3.5 to 1:15.
[0012]
The enlarged block body 7 can be made by cutting the same material as the welding dowel 1, for example, a metal material such as steel. The enlarged block body 7 is formed in a ring shape having a flat top surface 8 and a bottom surface 9, and has a through hole 10 having a circular cross section at the center.
The insertion hole 10 of the enlarged block body 7 has an inside diameter that is large enough not to generate an arc between the shaft portion 3 or the welded portion 4 of the welding dowel 1 during arc stud welding, but to be able to be welded to the welding dowel 1. The gap between the inner peripheral surface of the hole 10 and the shaft 3 is usually about 2 to 3 mm. Further, the ratio of the diameter of the shaft portion 3 of the welding dowel 1 to the outer diameter of the enlarged block 7 is about 1: 2 to 1: 3, and the height ratio is 1: 0.5 or more.
[0013]
An inert gas supply jig 11 is arranged so as to cover the upper part of the through hole 10 of the enlarged block 7. The inert gas supply jig 11 is made of a heat-resistant material such as a ceramic material, is formed in a ring shape having a circular cross-section insertion hole 12 through which a welding dowel is inserted at the center, and is formed of an argon gas or a carbon dioxide gas. Such an inert gas is introduced into the inside from the pipe 13 through the inlet 14, and is blown out from the outlet 15 at the bottom. Further, steps 16 and 16a are formed on the upper and lower portions of the inert gas supply jig 11, respectively. A pressing ring 18 of a pressing body 17 is fitted into the step 16 and the enlarged block is inserted into the step 16a. The upper edge of the through hole 10 of the body 7 is fitted.
The insertion hole 12 has an inner diameter capable of securing a slight gap 12a between the shaft portion 3 of the welding dowel 1 and the inert gas and generated gas supplied during welding are discharged to the outside by the gap 12a. Is done.
A connecting portion 19 extends vertically from the pressing ring 18, and a distal end portion of the connecting portion 19 is detachably connected to a stud welding machine 20 by a screw connection or the like.
[0014]
In this example, in order to separate the inert gas supply jig 11 from the welding dowel 1 after stud welding, the inert gas supply jig 11 is configured to be able to be divided into, for example, two parts around the axis. However, when the head 5 of the welding dowel 1 is not enlarged beyond the shaft 3, such a dividing means is not necessary.
On the other hand, power is supplied to the stud welding machine 20 from an arc stud welding machine body (not shown), and the chuck 21 holds the head 5 of the welding dowel 1 in a detachable manner.
FIG. 3 is a cross-sectional view showing another example of the enlarged block body 7. A concave section 22 having a circular cross section that opens upward is formed at the center of a block having a flat top surface 8 and a bottom surface 9. The concave portion 22 is formed by processing a cylindrical metal block and leaving a bottom portion 23 having a thickness such that it melts during arc stud welding and penetrates. 3 is used in the same manner as in FIG. The arc stud welding at this time occurs between the welding dowel 1 and the bottom 23 of the recess 22, and the seat 23 is melted. As a result, the welding dowel 1, the workpiece 2 and the enlarged block 7 are integrally joined.
[0015]
FIG. 4 is a partially enlarged view showing another example of the welding dowel 1 used in the present invention. The welding dowel 1 is formed on a tapered welding portion 4 whose sectional area decreases toward the tip and a lower outer peripheral surface of a shaft portion 3 extending upward from the welding portion 4 using a flux material similar to the material forming the electrode 6. The thin flux layer 6a is coated. In order to cover such a flux layer 6a, for example, there is a method of dipping the tip portion 4 or the like into a molten liquid of a flux material. The coating of the flux layer 6a is performed on at least a portion of the enlarged block body 7 to be inserted into the through hole 10 or the concave portion 22. In addition, the coating can be applied to either the tip portion 4 alone or a part of the shaft portion 3 above the tip portion 4.
By the coating of the flux layer 6a, the flux is evaporated from the surface during welding. Therefore, it is effective when the amount of evaporation flux is insufficient with only the electrode 6. Particularly, in the welding method of the present invention, it is suitable when the volume of the distal end portion 4 of the welding dowel 1 is large.
[0016]
Next, a method for welding a welding dowel using the above components will be described.
In FIG. 1, first, the bottom surface 9 of the enlarged block body 7 is placed on the surface of the portion to be stud-welded of the body 2 to be welded via the amorphous foil 24 or amorphous powder or in contact therewith without interposing them. Next, the inert gas supply jig 11 is placed thereon. The amorphous foil at this time enables diffusion welding. Next, the welding dowel 1 is gripped by the chuck 21 of the stud welding machine 20 connected to the arc stud welding machine body (not shown). Then, the tip 4 of the welding dowel 1 is inserted into the through hole 10 of the enlarged block 7 as shown in the figure, and the electrode 6 at the tip is brought into contact with the surface of the workpiece 2. On the other hand, an inert gas is blown from the inert gas supply jig 11 into the through-hole 10.
When the stud welding machine 20 is started in this state, first, electricity is supplied for a short time between the contact surface between the electrode 6 provided at the tip portion 4 of the welding dowel 1 and the workpiece 2, and then the welding dowel 1 is automatically slightly And a gap is formed between the tip 4 and the workpiece 2 to start arc discharge.
[0017]
The welding is performed in an atmosphere of an inert gas, and the supplied inert gas and generated gas are supplied from a gap 12 a formed by the shaft portion 3 of the welding dowel 1 and the insertion hole 12 in the inert gas supply jig 11. Released outside.
When the arc discharge is started, the inner diameter of the through hole 10 of the enlarged block 7 is set so as not to cause an arc between the shaft portion 3 and the welded portion 4 of the welding dowel 1 as described above. The discharge continues well between the welding dowel 1 and the workpiece 2.
Due to the continuation of the arc discharge, the distal end portion 4 of the welding dowel 1 is melted, a molten pool is formed in the through hole 10, and the welding dowel 1, the workpiece 2 and the enlarged block 7 are connected by the molten pool. Next, by lowering the welding dowel 1 and pressing it against the to-be-welded body 2, the welding dowel 1 and the to-be-welded body 2 and the enlarged block 7 are integrally joined. This welding time is usually about 1 second, and is completed in an extremely short time.
[0018]
FIG. 5 is a partially cutaway front view showing the welded jewel 1 thus welded, the welded body 2 and the enlarged block body 7 in a joined state. The tip 4 of the welding dowel 1 disappears due to melting, and as a result, the shaft 3 of the welding dowel 1 and the welded body 2 and the enlarged block 7 are bridged and integrated, and the lower part is integrally enlarged. Almost the same state is achieved as when the welding dowel 1 of the shaft 3 is joined to the workpiece 2. Therefore, a sufficient resistance to shear stress is ensured.
FIG. 6 shows a state in which concrete is cast at a place where the welding dowel 1 and the enlarged block body 7 are integrally joined to the workpiece 2 as shown in FIG. 5 to form a composite of the workpiece 2 and the concrete layer 30. FIG.
The above-described welding method is the same when the enlarged block body 7 shown in FIG. 3 is used.
[0019]
【The invention's effect】
Since the stud welding method of the present invention is configured as described above, despite the simple structure of the welding dowel, the welded portion is not broken against the expected maximum shear stress, and the initial rigidity is high. since the breaking position becomes a shaft, for a number of times repeated load of (10 ⁸ order of), greatly improved fatigue strength.
[Brief description of the drawings]
FIG. 1 is a partially cutaway front view for explaining a stud welding method of the present invention.
FIG. 2 is an exploded perspective view showing a main part of FIG. 1; FIG. 3 is a sectional view showing another example of an enlarged block body 7 used in the present invention;
FIG. 4 is a partially enlarged view showing another example of the welding dowel 1 used in the present invention.
FIG. 5 is a front view of a partially welded state of the welded dowel 1 to be welded 2 and the enlarged block 7 welded together;
FIG. 6 is a partial cross-sectional view showing a state where concrete is poured into a place where the welding dowel 1 and the enlarged block 7 are integrally joined to the workpiece 2 as shown in FIG. 5;
FIG. 7 is a breaking characteristic curve of shear force and slip between another conventional welding dowel shown in FIG. 8 and the welding dowel shown in FIG. 9;
FIG. 8 is a cutaway explanatory view of another conventional welding dowel.
FIG. 9 is a cutaway explanatory view of a welding dowel with an enlarged front end portion of a shaft portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Welding dowel 2 Workpiece 3 Shaft part 4 Tip part 5 Head part 6 Electrode 6a Flux layer 7 Enlarged block body 8 Top surface 9 Bottom surface 10 Through hole 11 Inert gas supply jig 12 Insertion hole 12a Gap 13 Pipe 14 Inlet 15 Blowing Outlet 16 Step 16a Step 17 Pressing body 18 Press ring 19 Connecting part 20 Stud welding machine 21 Chuck 22 Depression 23 Bottom 24 Amorphous foil 30 Concrete layer

Claims (5)

In a stud welding method, a metal welding dowel (1) having a shaft part (3) and a welding part (4) is gripped by a stud welding machine (20) and fixed to a workpiece (2) by welding.
It has a flat bottom surface (9) and a recess (22) in which a through hole (10) or a bottom (23) thick enough to melt and penetrate during arc stud welding remains, and The size of the hole (10) or the recess (22) that can be welded to the welding dowel (1) that does not cause an arc between the shank (3) and the welding part (4) of the welding dowel (1) during arc stud welding. A metal enlarged block body (7) having the following is prepared, and the enlarged block body (7) is arranged with the bottom surface (9) in contact with the surface of the material to be welded (2). An inert gas supply jig (11) having an insertion hole (12) through which an inert gas is blown out from the bottom is provided with a through hole (10) or a concave portion (22) of the enlarged block body (7). ) And insert the welded part (4) of the welding dowel (1) inserted through the insertion hole (12) into the through hole (10) or the recessed part (22) and cover the tip. By contacting the surface of the welding material (2) or the surface of the bottom (23) , the inert gas is supplied from the inert gas supply jig (11) into the through hole (10) or the recess (22). A stud welding method in which the welding dowel (1) is welded and fixed to the workpiece (2) and the enlarged block (7) by starting the welding machine (20) and performing stud welding. The stud welding method according to claim 1, wherein the upper surface of the inert gas supply jig (11) is pressed by a pressing body (17) connected to the stud welding machine (20) during the stud welding. The stud welding method according to claim 1 or 2, wherein a gap (12a) through which gas flows is provided between the insertion hole (12) of the inert gas supply jig (11) and the shaft part (3) of the welding dowel (1). The stud welding method according to any one of claims 1 to 3, wherein at least the periphery of a portion of the welding dowel 1 inserted into the through hole 10 or the recess 22 of the enlarged block body 7 is covered with the flux layer 6a. The stud welding method according to any one of claims 1 to 4, wherein an amorphous foil (24) or an amorphous powder is disposed on at least the bottom surface (9) of the enlarged block body (7).

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