JPH11151578A - Butt welding method and welding machine for high strength wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a butt welding method and welding machine for a high strength wire rod having a weld zone whose breaking load is the same or higher than the base material. SOLUTION: In high strength wire rod welding in which a wire rod S to the welded is clamped by a split electrode 1 for butt welding, a position at a prescribed distance from the joining end of the wire rod S is clamped by the electrode 1, and the rod S is energized to be butt-welded. Then, a position at a prescribed distance from the joined part of the welded wire rod is clamped again by the electrode 1 and re-energized, with upset welding performed for a prescribed quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a concrete column,
The present invention relates to a butt-welding method and a welding machine for a heat-treated high-strength wire such as a reinforcing wire used for a beam or the like.

[0002]

2. Description of the Related Art For example, a reinforcing bar wire such as a concrete column or a beam uses a main bar and a hoop bar as an auxiliary bar for reinforcing the shearing which surrounds the main bar group. As the hoop streaks, there are a method in which a long wire is continuously wound around the main streaks, and a method in which hoops wound one turn at a time are arranged one by one around the main streaks. The former hoop using a long wire is advantageous in terms of strength in that there is no welded portion, but has difficulty in field work. For this reason, the latter method of arranging a one-turn hoop streak created in advance on site is often adopted. In this one-turn hoop streak, it is desirable that the breaking load of the welded portion is equal to or greater than that of the base material so as not to break at the welded portion.

[0003]

SUMMARY OF THE INVENTION However, the above 1)
The turn hoop streak is formed by forming a wire cut into a predetermined length into a predetermined shape and then butt-welding both ends of the wire, so the strength of the welded portion due to the heat effect of the welded portion is lower than that of the base metal. There is. When a low-strength wire is used when manufacturing a one-turn hoop, there is little problem because the strength change due to the thermal effect of the weld is small. However, when using a high-strength wire rod that has been subjected to heat treatment, such as a PC steel rod, the strength of the welded portion is reduced by the welding heat and the mechanical strength of the completed hoop streak is reduced. There is no point in using wires. Therefore, in order to guarantee the strength of the hoop, the welded portion may be reheat-treated to recover the mechanical properties, or a thicker wire may be used, but this is disadvantageous in terms of man-hour and economy.

On the other hand, as a countermeasure against earthquake, demands for improvement of shear strength of reinforced concrete columns and beams, and demand for use of high-strength wires having the same strength as steel bars specified in PC steel bar standards for hoop bars of auxiliary bars have also been required. Therefore, when such a high-strength wire is used, it is desired to develop a welding method in which the breaking load of the welded portion is equal to that of the base material.

Accordingly, the present applicant has disclosed the invention of "high-strength one-turn auxiliary bars and electrodes of a welding machine for producing the same" (JP-A-6-99286).

The present invention is a further development of the above-mentioned invention, and a butt welding method and a welding machine for a high-strength wire in which a rupture load at a welded portion is equal to or greater than that of a base material even in a reinforcing wire using a heat-treated high-strength wire. The purpose is to provide.

[0007]

In order to achieve the above object, a method for butt welding a high-strength wire according to the present invention comprises the steps of welding a high-strength wire by holding a wire to be welded with a split electrode and performing butt welding. In the above, after a predetermined distance from the joint end of the wire to be welded is gripped by the electrode and energized to perform butt welding, the electrode is further gripped at a predetermined distance from the joint of the welded wire. Then, a predetermined amount of upset is performed by supplying power again.

That is, in the butt welding method of the present invention, a normal butt welding is first performed on a reinforcing rod wire to form a normal welding bulge, and then a hot upset is further performed in the vicinity of the welding portion. In addition to making the diameter in the vicinity larger than the diameter of the base metal, the mechanical properties of the joint were reduced due to the high-temperature welding heat generated during the initial welding, and the fracture load of the weld was equal to or greater than that of the base metal. It is to be. The recovery of the mechanical properties of the weld is presumed to be due to an increase in the number of passive dislocations due to a tempering effect by heating during hot upset and a dynamic strain aging effect by warm working.

In the butt welding method for a high-strength wire according to the present invention, in the butt-welding of the high-strength wire, the parallel groove for gripping the wire to be welded and the opening at the weld joint side end of the parallel groove are expanded in a trumpet shape. And a butt-welding is performed by gripping a position at a predetermined distance from the joint end of the wire to be welded with the electrode and conducting butt welding by enlarging the welding portion to the wire to be welded. After the formation of the joint, a predetermined distance from the joint of the welded wire is grasped again by the same electrode, and current is supplied again to perform a predetermined amount of upset.

That is, when a butt wire is gripped by a split electrode having a grip portion whose end on the weld portion side is open in a trumpet shape and normal butt welding is first performed, the trumpet-shaped opening portion of the electrode is As a result, a hot-upset at the time of welding forms a spindle-shaped joint having an enlarged diameter of the welded portion following the opening of the electrode on both sides of the welding bulge. In this way, a spindle-shaped joint that is thicker than the base metal diameter is formed in the vicinity of the weld,
Even if the mechanical strength of the weld decreases due to welding heat, a break load equal to or greater than that of the base material can be obtained by increasing the cross-sectional area, and the break load of the base material can be assured as a whole hoop bar.

Further, in the welding method according to the present invention, after performing the normal butt welding, a hot upset is performed in the vicinity of the welded portion, and the mechanical properties of the welded portion generated by the welding due to high temperature welding heat are increased. The purpose of the present invention is to recover the decrease and improve the mechanical properties of the spindle type joint formed by the first welding. The mechanism is as described above.

In order to obtain the most desirable mechanical properties of the joint, the upset amount to be performed after the first welding is 0.1d to 0.1d, where d is the diameter of the wire rod to be welded.
8d, more preferably 0.4 to
0.5. If the upset amount is too small, the above effect cannot be sufficiently exhibited, and if it is too large, the strain aging effect cannot be obtained.

The butt welding machine for a high-strength wire according to the present invention includes a split electrode for gripping the wire to be welded, and the electrode grips a position at a predetermined distance from the welded end of the wire to be welded to join the wire. Butt welding of the wire by applying a current while applying pressure, the electrode is re-gripped at a position at a predetermined distance from the joint of the welded wire, and a current is applied by applying a pressure again while pressing the joint end. And a control means operable to perform the upset.

That is, in the butt welding machine of the present invention, the wire to be welded is first gripped by the split electrode at a predetermined distance from the joining end, and is moved by a predetermined distance in the direction of the welded portion while being energized to perform normal butt welding. Perform welding. When the welding is completed, the electrode opens the wire and moves in a direction away from the welded portion, grips the wire again at a predetermined position, moves again a predetermined distance in the direction of the welded portion while energizing and heating the wire again, It operates to upset the welded wire by a predetermined amount. Since such an operation is automatically performed by the control means, labor saving and uniform welding can be performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings. FIG. 1 is a diagram for explaining a working process of butt welding of a high-strength wire rod according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of an electrode shape thereof, and FIG. FIG. 4 is a block diagram showing a control unit of the high-strength wire butt welding machine according to the embodiment of the present invention, and FIG. It is a flow chart which shows operation of butt welding of a high intensity wire of an embodiment of the present invention.

The electrode 1 shown in FIG. 2 has a symmetrical pair provided with a parallel groove 3 for holding a wire to be welded (hereinafter referred to as a wire) having a diameter approximate to the diameter of the wire and an opening 4 having a welding-side end opened in a trumpet shape. Of the holding members 1a and 1b. Gripping members 1a, 1
b is made of a conductive material such as a copper alloy and is driven to open and close to grip and release the wire to be welded. Then, as shown in FIG. 1, the two electrodes are driven so as to hold both sides of the welded portion of the wire and press the welded portion of the wire by pressure, and a current is applied between the two electrodes to heat the welded portion. Butt welding is performed by pressing.

The control means 10 shown in FIG. 4 includes a CPU 11, a setting section 12 for setting the position of the electrode and the amount of upsetting, and a control section for detecting the electrode position, applying pressure to and driving the electrode, and controlling the voltage and current of the electrode. 13 A standby position setting unit 14 for setting the electrode standby position T0 in the setting unit 12;
Welding upsetting unit 15 for setting upsetting amount T1-T2 of welding (T1: electrode position when the welded portion is cold pressed, T2: electrode position after welding), and when starting upset Upset initial position setting unit 1 for setting electrode position T3
6 and an upset amount setting unit 17 for setting an upset amount T3-T4 (T4: electrode position after upset). Further, an electrode current setting unit 22 for setting an electrode current during welding and an electrode current value during upsetting is provided. Appropriate values are determined experimentally for the welding current and the upset current depending on the wire diameter, material, and the like of the work. The control unit 13 includes an electrode position detection unit 18 and an electrode control unit 19
And a power supply controller 20. The electrode control unit 19 moves the electrode 1 to the position of the numerical value set in the setting unit 12 by the electrode moving unit 24 based on the position signal of the electrode position detecting unit 18, and opens and closes the electrode by the electrode opening and closing unit 23. And release it.

Hereinafter, the operation of the butt welding machine of the present invention will be described with reference to the flowcharts of FIGS. 1, 3, 4 and 5. First, a predetermined numerical value adapted to the diameter of the wire to be welded is set in the setting unit 12 (step 1). That is, the standby position T0 of the electrode when the workpiece is set on the electrode, the upsetting amount T of welding.
1-T2, the electrode position T3 at the start of the upset and the upset amount T3-T4 are set to the standby position setting unit 1 respectively.
4, welding upsetting section 15, upset initial position 16,
It is input to the upset amount setting unit 17. Further, a welding current value corresponding to the wire diameter of the wire to be welded is input to the electrode current setting unit 22.

Next, when the start switch 15 is pressed (step 2), the electrodes 1 and 1 on both sides are moved to the set standby position T0 of FIG. 1A via the CPU 11 and the electrode controller 19 (step 3). ). At this time, the electrode 1 is in an open state. At this point, a wire to be welded (hereinafter referred to as a work) S is mounted on the parallel groove 3 of the electrode 1 with the welding point being the center between the electrodes (step 4), and the electrode open / close switch 26 is closed (step 5). The electrodes 1, 1 on both sides are closed via the CPU 11, the electrode control unit 19, and the electrode opening / closing means 23, and
The grip S is held. When the electrodes 1 and 1 grip the work S,
Pressure is applied to press the welded portion of the work S through the electrode moving means 24 (Step 6). Thereby, the welded end of the work is crushed, and the electrode slightly moves in the direction of the welded portion and moves to the position of T1 (step 7) (FIG. 1 (b)),
This T1 is stored in the CPU 11. At the same time CPU1
1. The welding current input to the electrode current setting unit 22 is applied to the electrodes 1 and 1 on both sides from the power supply 25 via the power supply controller 20, and the contact surface is resistance-heated (step 8).
When the work S between the electrodes 1 and 1 on both sides is heated and softened, the electrode 1 moves forward because it is pressed in the welding direction by the electrode moving means 24 (step 9). Further, since the welding upset amount T1-T2 has been input to the welding upset setting section 15, the electrode moves to the position T2 in FIG. 1C (step 10), stops at the position T2, and sets. Is completed (step 11), and a weld bulge 5 as shown in the figure is formed. When the butt welding is completed, the power flowing to the electrodes via the power controller 20 is turned off.
(Step 12).

The butt welding according to the present invention is further characterized in that the work S after the completion of the welding is hot-upset as follows. After the above welding is completed, the power supply is OF
When the switch is set to F, the electrode is opened via the electrode opening / closing means 23, and the grip of the work is released (step 13). Then, the electrode retreats through the electrode moving means 24 (step 1).
4) Move to the position T3 input to the upset initial position 16 (step 15) (FIG. 1 (d)). When the electrode stops at the position T3, the electrode 1 is closed via the CPU 11 and the electrode opening / closing means 23, and the workpiece is grasped again (step 1).
6) Pressure is applied in the welding direction via the electrode moving means 24 (step 17), and the power of the electrode 1 is turned on via the power controller 20 (step 18). Electrodes 1, 1
When a current flows between the electrodes 1 and 1, the work S between the electrodes 1 and 1 is heated. At this time, the electrode current setting unit 22 is set so that a current smaller than the welding current flows, so that the temperature becomes a low temperature at which upsetting is possible. Has been.

Since the electrode is pressurized in the welding direction and the upset amount T3-T4 is input to the upset amount setting section 17, when the work S is heated and softened, the electrode 1 advances while upsetting the work. (Step 1
9), move to the position of the interval T4 in FIG. 1 (e) (step 20) (FIG. 1 (e)). When the electrode 1 moves to the position of T4, the power is turned off (step 21), and the upset of the predetermined amount of upsetting is completed.

When the upset is completed, the electrode opening / closing means 2
The electrode is opened via 3 to release the gripping of the work (step 22). Then, the electrode retreats via the electrode moving means 24 (Step 23), and moves to the position T0 input to the upset standby position setting unit 14 (Step 2).
4) (FIG. 1 (a)). At this position, the work S is removed from the electrode 1 (step 25), and the welding operation of the present invention is completed (step 26).

As described above, the apparatus and method of the present invention are significantly different from the conventional butt welding of high-strength wire rods in that hot upset is performed again in the vicinity of the welded portion, in addition to normal butt welding. That is, when the heat-treated high-strength wire is butt-welded by a conventional welding method, the mechanical properties of the welded portion are reduced by welding heat, and the wire is broken at a load lower than the breaking load of the base material. On the other hand, in the present invention, after normal butt welding, hot upset processing is performed again on the vicinity of the welded portion, so that dislocations generated during welding are immobilized or fixed due to dynamic strain aging effect, resulting in high temperature generated by welding. Of the mechanical properties due to the welding heat is recovered, and the upset makes the diameter near the weld larger than the base metal diameter and increases the cross-sectional area, so the fracture load of the weld is equal to or greater than that of the base metal Can be

Further, since the gripping members 1a and 1b of the electrode 1 have the openings 4 whose diameters are enlarged on the welding portion side as shown in FIG. 2, the welding bulges as shown in FIG. A tapered portion 6 is formed on both sides of 5 so that the joining portion has a spindle shape. This is because the opening 4 forms a die, and the heated wire between the electrodes on both sides forms a spindle shape in accordance with the die. As a result, the diameter of the wire near the weld becomes larger than the diameter of the base metal. Equivalent or better is obtained.

Further, in the present invention, since the hot upset process is further performed on the vicinity of the welded portion after the welding, the reheating of the upset process produces a dynamic strain aging effect at the joint portion, and the dislocation generated at the time of welding as described above. Is immobilized or fixed, and the deterioration of the mechanical properties due to the high welding heat is recovered. Also,
As shown in FIG. 1 (d), the shape of the joint portion is such that two-stage tapered portions 6 and 7 are formed, and the diameter of the joint portion is larger than the diameter of the base material.
As a result, the butt-welded hoop reinforces the breaking load of the welded portion more than the breaking load of the base metal,
The use of small-diameter wires becomes possible, and the weight can be reduced.

[0026]

EXAMPLE A butt welding experiment was carried out using a heat-treated PC steel rod having a diameter of 13.12 mm by the method of the present invention and the conventional method. Table 1 shows the mechanical properties of the wire. That is,
The breaking load of the base material is about 20 tons and the tensile strength is about 149k
gf / mm ² .

[0027]

[Table 1]

Butt welding was performed by the method of the present invention and the conventional method and compared. The method of the present invention was carried out using electrodes having openings of the shape shown in FIG.

[0029]

[Table 2]

Table 3 shows a comparison result of a tensile rupture test of the test piece subjected to the butt welding of the present invention under the above conditions and the test piece subjected to the butt welding of the conventional method at a gauge length of 10 d.

[0031]

[Table 3]

As can be seen from the table, all the test pieces of the method of the present invention were broken at the base material, and the breaking load was 20.55 ton on average.
The breaking elongation of the base material shown in Table 1 was 20.08 ton, and the breaking elongation was the same as that of the base material. In contrast, all conventional methods break at the weld or at the joint near it,
The breaking load varied widely and reached an average of 16.84 ton, only 83% of the breaking load of the base material, and the breaking elongation was smaller than that of the base material.

Table 4 shows the results of microscopic observation of the cross section of the joint of the test pieces. Table 4 shows the positions (a) to (d) of the axis at a distance of 0 to 10 mm from the welding surface shown in FIG.
Is a result of microscopic observation. As can be seen from the table, the butt welding method of the present invention has a structure equivalent to that of the base material at a position 5 mm from the welding surface.

[0034]

[Table 4]

Although details are omitted, many experimental results
The amount of the upset after the butt welding may be 0.1d to 0.8d, where d is the diameter of the wire to be welded,
0.4 to obtain the most desirable mechanical properties of the joint
d to 0.5d was found to be desirable.

As described above, in the welding machine and the welding method of the present invention, after performing ordinary butt welding on a wire,
Furthermore, since the hot upset is performed in the vicinity of the welded portion, the reduction in mechanical properties due to welding heat can be recovered, and at the same time, the diameter of the joint becomes larger than the base material diameter due to the upset. It can be equal to or greater than that of the material. Thereby, a wire rod having a smaller diameter than the conventional welding method can be used, and the weight can be reduced.

Further, by using a split electrode having an opening in which the welding side end of the wire gripping portion of the electrode is enlarged in diameter,
Since a spindle-type joint with an enlarged welded portion is obtained, even if the mechanical strength of the welded portion is reduced, a fracture load equal to or greater than that of the base material can be obtained by increasing the cross-sectional area. The breaking load of the material is guaranteed.

Further, since the welding machine of the present invention automatically performs the above-mentioned welding and the upset after the welding by setting the conditions, labor can be saved and mass production becomes easy.

In the above embodiment, an electrode having an opening at the welding end is used. However, an electrode having only an ordinary parallel groove without such an opening may be used after the welding according to the present invention. By performing the upset, it is possible to recover the mechanical properties of the joining portion and to increase the diameter.

[0040]

As described above, according to the butt-welding method and the welding machine for a high-strength wire of the present invention, even in a one-turn hoop streak using a high-strength wire, the breaking load of the base material is equal to or more than that. Butt welding having a breaking load at the welded portion can be performed, so that a wire rod having a smaller diameter than a rebar wire rod by a conventional welding method can be used, and it is lightweight and economical.

Further, since a highly reliable one-turn hoop streak having a high breaking load can be obtained, it can be replaced with a continuously wound hoop streak, which facilitates on-site processing and reduces man-hours and costs.

[Brief description of the drawings]

FIG. 1 is a view showing an operation stage of butt welding of a high-strength wire rod according to an embodiment of the present invention.

FIG. 2 is a view showing an example of an electrode shape of a butt welding machine for a high-strength wire rod according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a position of a test piece obtained by butt welding according to an embodiment of the present invention, which is observed with a microscope.

FIG. 4 is a block diagram illustrating a control unit of the high-strength wire rod butt welding machine according to the embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the high-strength wire rod butt welding machine according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 electrode 1a gripping member 1b gripping member 3 parallel groove 4 opening 5 welding bulge 6 shoulder 7 second shoulder 10 control unit 11 CPU 12 setting unit 13 control unit 14 standby position setting unit 15 welding upsetting unit 16 upset initial Position 17 Upset amount setting section 18 Electrode position detection section 19 Electrode control section 20 Power supply controller 21 Start switch 22 Electrode current setting section 23 Electrode opening / closing means 24 Electrode moving means 25 Power supply 26 Electrode opening / closing switch S Work (wire to be welded)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI E04G 21/12 105 E04G 21/12 105E

Claims (4)

[Claims] When welding a high-strength wire rod by gripping a wire to be welded by a split electrode and performing butt welding, a position at a predetermined distance from a joint end of the wire to be welded is gripped by the electrode and energized to butt. A butt-welding method for a high-strength wire rod, wherein after welding is performed, the electrode is further gripped at a predetermined distance from the joint portion of the welded wire rod, and is again energized to perform a predetermined amount of upset. . 2. A butt welding of a high-strength wire using a split electrode having a parallel groove for gripping a wire to be welded and an opening whose welding end of the parallel groove is enlarged in a trumpet shape. After gripping a position at a predetermined distance from the joining end of the wire to be welded, conducting butt welding by conducting electricity, forming a spindle type joint having a welded portion enlarged in the wire to be welded, and further using the same electrode. A butt-welding method for a high-strength wire rod, comprising re-gripping a position at a predetermined distance from a welded portion of the welded wire rod, and supplying electricity again to perform a predetermined amount of upset. 3. The upset amount performed after the butt welding is 0.1 d to 0.8, where d is the diameter of the wire to be welded.
The butt welding method for a high-strength wire according to claim 1 or 2, wherein d is used. 4. A butt-welding of the wire by providing a split electrode for gripping the wire to be welded, the electrode gripping a position at a predetermined distance from a joint end of the wire to be welded, and energizing while applying pressure to the joint end. And a control means for re-gripping the electrode at a predetermined distance from the welding portion of the welded wire, applying a current while pressing the bonding end again, and performing a predetermined amount of upset. Butt welding machine for high strength wire rods.