JP3274335B2 - Backing material for steel bar welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a T-type butt welding of a steel bar or the like to an end face of a steel bar such as a reinforcing bar, and more particularly to a steel bar having a diameter of, for example, 19 mm or more and 51 mm or more.
A technique suitable for a case of a large diameter up to a certain extent is provided.

[0002]

2. Description of the Related Art In recent years, the number of reinforcing steel bars used in a reinforced concrete structure has been increasing along with the increase in size and height of the building, and there is a tendency for the diameter to be longer and longer. As a conventional T-type butt welding method for steel bars such as reinforcing bars, an efficient arc stud welding method disclosed in Japanese Patent Application Laid-Open No. 3-169486 has been used. Problems such as poor cutting and poor fusion make welding difficult. In particular, in a welding position in which the bar is oriented horizontally, the diameter of the bar is limited to about 22 mm.

Therefore, in welding of a large diameter steel bar, as shown in FIG. 5, a steel plate 13 is tack-welded 17 to the side surface of a steel column 12, and furthermore, a steel bar 10 is disposed thereon and tack-welded 17, The gap 14 between the end of the bar and the steel column was build-up welded by arc welding. However, since the steel bar body is welded after the steel sheet is temporarily attached, there is a problem that the work required for welding increases and the efficiency is extremely poor.

On the other hand, the present inventors have already made the T
As a butt-welding method, a steel bar and a steel plate are fixed with a predetermined groove space provided, and the groove space is surrounded by a ceramic backing material having an opening at the top, and a welding wire is opened from the opening. We are developing an automatic arc welding method that inserts into the tip and welds from the bottom of the groove.

[0005] In arc welding, arc plasma is generated between a welding wire and a workpiece, and the heat is used to melt the welding wire to join the workpiece. For this reason, electrical conduction between the workpiece and the welding wire is indispensable, but in the above welding method, the groove bottom serving as the arc start position is made of ceramics, so it has no conductivity and cannot perform arc start. . Therefore, in order to provide conductivity between the groove bottom and the workpiece, an arc start is performed by spreading steel wool on the groove bottom. However, the method of laying steel wool has a problem that it takes much time and troubles the welding efficiency remarkably, and when it is not uniformly laid, the arc start fails. Furthermore, in the present method, there is no simple method for accurately maintaining the groove space between the steel bar and the steel plate when the steel bar is fixed, so that the groove width is likely to vary, which may cause welding defects.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned prior art, the present invention stabilizes the arc start in T-type butt welding of steel bars and further eliminates the variation in groove width when fixing the steel bars. It is an object to provide a backing material for finishing a joint part with high efficiency and high quality.

[0007]

In order to achieve the above object, a backing material for steel bar welding according to the present invention comprises a welding wire and a work to be welded by laying a U-shaped metal fitting on a groove bottom at a welding start position. It is characterized by providing conductivity between the steel bar and the steel plate to be able to perform a reliable arc start, and using the metal fittings to make the groove width of the steel bar and the steel plate uniform.

That is, the gist of the present invention is that a steel bar and a steel plate are fixed by providing a predetermined groove space, and the grooved space is surrounded by a backing material which is provided with an opening at the top and which is removed after welding is completed. A backing material for welding a steel bar and a steel sheet by inserting a welding wire from the opening into the groove , and a metal fitting for arc start is attached to the backing material bottom , and , The bracket is U-shaped and welded
The groove width is kept constant by being sandwiched between
It is a backing material for bar steel welding characterized by having. Here, after the welding is completed, the backing material to be removed is made of ceramics or copper, and can be divided into two by a dividing surface in the longitudinal direction of the steel bar.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The backing material for welding steel bars of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the backing material 1 has a cylindrical shape surrounding a steel bar, and has an opening 2 at an upper portion for inserting a welding wire. In order to perform a bead appearance inspection, the material of the backing material is preferably ceramics or copper which can be removed after welding without welding to the weld metal.

When a ceramic backing material is used, the ceramic can be pulverized and removed after welding is completed. A metal fitting 3 is attached to the bottom of the backing material, which has a U-shape as shown in FIG. 2. The gap between the steel bar end face and the steel plate is fixed when the steel bar is fixed, and the welding is performed at the start of welding. The tip of the wire, the steel bar and the steel plate are electrically connected to each other through the metal fittings, so that the arc start is reliably performed. The thickness of the metal fitting is preferably set to 1.0 mm or more in consideration of the strength of maintaining the gap, and is preferably set to 1.5 mm or less in order to eliminate unmelted residue during welding. In FIG. 2, reference numeral 16 denotes a fixing nail.

On the other hand, as shown in FIG. 3, the copper backing material can be easily removed after the welding is completed by dividing the copper backing material into two along the longitudinal dividing surface 15. By attaching the metal fitting 3 to the copper backing material in the same manner as the ceramic backing material, the gap between the steel bar end face and the steel plate is fixed when the steel bar is fixed, and the welding arc is directly applied to the copper backing material at the start of welding. Touching can be prevented, so that copper damage can be prevented.

The advantage of using a ceramic backing material is that the bead surface is finished smoothly because the ceramic melts during welding to form molten slag, and the advantage of using a copper backing material is that Since the material can be repeatedly used, the cost of the backing material can be reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as an embodiment of the present invention, a T-shaped butt welding of a 35 mm-diameter reinforcing bar and a 19 mm-thick SS400 material was performed using an automatic welding machine for welding steel bars. The welding method was arc welding of a carbon dioxide gas shield, and a wire for 60 kgf / mm ² was used as a welding wire.
FIG. 4 is a schematic diagram of the used apparatus, and a part of the apparatus is shown in cross section. The apparatus includes a mechanism (not shown) for moving the welding torch 4 and the welding torch in the steel bar diametric direction 5, moving in the groove width direction 6, and moving the torch up in the drawing direction 7, a clamp 8 for fixing the steel bar, a wire straightening machine 9 And so on.

The preparation process before welding will be described with reference to FIG. First, the backing material 1 with the arc start fitting of the present invention is attached to the end of the steel bar (rebar) 10 to be welded, and the groove 3 between the steel plate 11 and the reinforcing bar 10 is set to 8 by the fitting 3 inside the backing material.
The reinforcing bar was fixed with the clamp 8 while keeping the diameter at 8 mm. When the reinforcing bar was fixed, the reinforcing bar 10 was pressed against a steel plate in order to keep the groove width constant, and the reinforcing bar 10, the metal fitting 3, and the steel plate 11 were set so as to be in close contact with each other. As a result of measuring the groove interval at the time of fixing the reinforcing bar, the fluctuation of the groove interval was about ± 0.3 mm. However, the inner diameter of the backing material 1 is increased by 10% of the nominal rebar diameter so that it can be smoothly attached to the end of the rebar, and the thickness of the metal fitting 3 is 1.2 mm in consideration of the strength for holding the groove width. did.

Next, the welding torch 4 was placed at a predetermined position above the backing material. At this time, in order to form a predetermined angle so that the welding torch does not hit the steel plate, the wire straightening machine 9 was used to forcibly bend the welding torch so that the tip of the welding wire could aim at the center of the groove.

When the welding preparation was completed in this way, a current was supplied from a welding power source, and welding was performed from the back of the groove to the torch side. Table 1 shows the comparison between the case where the metal fitting for arc start of the present invention was used and the case where it was not used as a welding method.

[0017]

[Table 1]

First, when the metal fitting for arc start was used for the ceramic backing material, a stable arc state was maintained and an excellent bead appearance was obtained. In the tensile test, the base material was broken and good results were obtained. On the other hand, when the metal fitting for arc start was not used, the arc became unstable at the start of welding and a defect of poor fusion occurred at the groove bottom, resulting in HAZ fracture. In addition, since it becomes difficult to make the groove width uniform when the reinforcing bar is fixed, the amount of welding slightly changed.

On the other hand, when a copper backing material was used, the arc state was stable irrespective of the presence or absence of the arc-start fitting, and the base material was broken in the tensile test. However,
By using the metal fitting for arc start, it became possible to reduce the damage of the copper backing, and it became clear that it was effective in reducing the cost of the backing material.

[0020]

As described above, the use of the backing material for bar steel welding of the present invention reduces the gap fluctuation at the time of fixing the steel bar and stabilizes the arc start in the T-shaped butt welding of a steel bar such as a reinforcing bar and a steel plate. It has become possible to perform with high quality and high efficiency. Therefore, the present invention is extremely useful in welding of reinforcing steel bars of high-rise buildings, marine structures, and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a backing material for steel bar welding of the present invention.

FIG. 2 is a view showing a metal fitting for starting a backing material according to the present invention.

FIG. 3 is a view showing a split type backing material for steel bar welding according to the present invention.

FIG. 4 is a schematic view of a welding device used in the embodiment.

FIG. 5 is a diagram showing a conventional method of T-shaped butt welding of steel bars.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Backing material 2 Opening 3 Metal fitting 4 Welding torch 5 Bar steel diameter direction movement 6 Groove width direction movement 7 Torch lifting direction movement 8 Steel bar fixing clamp 9 Wire straightening machine 10 Reinforcing bar (steel bar) 11 Steel plate 12 Steel column 13 Steel column Steel plate 14 Groove 15 Dividing surface 16 Claw 17 Temporary welding

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Sanshiro Obata 2-6-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (56) References JP-A-6-262353 (JP, A) JP-A-2-37993 (JP, A) JP-A-3-193298 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 37/06 B23K 9/038

Claims (3)

(57) [Claims] 1. A steel bar and a steel plate are fixed by providing a predetermined groove space, and the groove space is surrounded by a backing material having an opening at an upper portion which is removed after welding, and a welding wire is connected to the opening. A backing material for performing welding between a steel bar and a steel plate by being inserted into a groove from below, wherein a metal fitting for arc start is attached to the bottom of the backing material , and the metal fitting has a U-shape.
And opened by being sandwiched between the steel bar and steel plate
Backing material for bar steel welding, characterized in that the tip width is kept constant . 2. The backing material for bar steel welding according to claim 1, wherein the backing material to be removed after welding is made of ceramics. 3. The backing material for bar steel welding according to claim 1, wherein the backing material to be removed after the welding is completed is made of copper and can be divided into two by a dividing surface in a longitudinal direction of the steel bar.