JP2670909B2 - High-strength one-turn auxiliary bar and welding machine electrode for its production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a high-strength 1-turn auxiliary bar welded by butt welding using a high-strength wire rod having a predetermined length for shear reinforcement of reinforced concrete columns, beams, etc., and welding for manufacturing the 1-turn auxiliary bar. Machine electrodes.

[0002]

2. Description of the Related Art Reinforcing bar cages used for reinforced concrete columns, beams, etc. consist of a group of main reinforcements and auxiliary reinforcements for shear reinforcement surrounding the main reinforcements. As is well known, as a well-known form, a plurality of bend-formed auxiliary turns of one turn are provided at predetermined intervals at right angles to the axis line around a main bar group of a predetermined length arranged according to the shape of a formed pillar, beam, etc. In some cases, the wire is wound, and in some cases, a long wire is continuously bent and wound multiple times to form a spiral, which is arranged at a predetermined pitch over substantially the entire length of the main bar group. However, one turn, which is lighter than the multi-turn spiral muscle, has been favored from the viewpoint of arranging work, and has been the mainstream in the past.

Recently, when a high-strength wire having the same mechanical properties as a steel bar specified in the PC steel bar standard is used as the auxiliary bar, the ultimate shear strength is improved, so that the auxiliary bar made of the high-strength wire is used. The increase in the use of steel is increasing, and it is possible to replace not only the direct benefit of the improvement of the ultimate shear strength but also a secondary advantage, that is, a smaller diameter for obtaining the same ultimate shear strength, and thus the column・ We have obtained such things as the finished cross-sectional dimensions of beams can be reduced. In this case, the usage pattern is exclusively spiral arrangement. Because high-strength wire rods usually rely on heat treatment as a means of imparting high strength to the raw material wire rod, and the welding that is indispensable for forming one-turn auxiliary muscles is high-strength wire rods that have been applied by heat treatment. Because there was a fear of impairing the mechanical properties of.

More specifically, the electrode of the welding machine in the case of forming a one-turn auxiliary bar from a normal hot-rolled wire is
As shown in FIG. 1 (a), a split type electrode R'consisting of two pieces shown as r'and r ', which are opposed to each other, is used, and both ends of a wire rod W'cut to a predetermined length correspond to the wire rod diameter. The groove 3'provided by the above is tightly gripped and butt welded.
Although it is formed in one turn with a welding bulge as indicated by 1'in (b), the mechanical properties of the hot-rolled wire itself are low, for example, tensile strength; 60 kgf / mm ² , so the heat effect during welding Does not matter at all.

On the other hand, if a high-strength wire that has undergone in-line quenching and tempering under strict control is to be welded in order to form an auxiliary bar for one turn, it is the same as during quenching during welding. Or more fever,
It will have a thermal effect on the imparted mechanical properties. It may be possible to reheat the weld to address this, but the cost and effort involved is not very acceptable to the user, the construction industry. Therefore, the pillar,
When high ultimate ultimate shear strength is required for beams and the like, the current situation is that the reinforcement of the spiral auxiliary muscles is exclusively used as described above.

However, high shear ultimate proof strength is required for all columns, beams, etc. as a seismic resistant structure, and in addition, in view of workability of bar arrangement and finished dimensions of columns, beams, etc. Was about to be sought after.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-strength one-turn auxiliary bar, which does not deteriorate the mechanical properties of a welded part, at low cost and easily even when welding is performed using a high-strength wire. It is an issue.

[0008]

According to the first invention of the present application, as a high-strength one-turn auxiliary bar formed by butt-welding both ends of a high-strength wire cut into a predetermined length, the welds are parallel to both sides of the welding bulge. It is characterized in that it has a swelled portion that is uniform in the circumferential direction and is inclined in the direction of the portion. The bulged portion is formed by so-called warm forging so as to bulge in the entire circumferential direction by the pressing force in the direction in which the wire rods in a portion that does not become as hot as the tip end face during butt welding are pushed together. Therefore, the presence of the bulging portion has the effect of compensating for the deterioration on the joint surface over the area and with the warm forging metal structure that hardly deteriorates the heat-treated mechanical properties.

The second invention of the present application uses high-strength wire as a raw material, and both ends of the raw material are tightened as electrodes of a welding machine used when manufacturing the high-strength one-turn auxiliary bar of the first invention by butt welding. In the case of a split mold in which each electrode to be gripped is composed of two pieces facing each other, a predetermined angle is formed at the welding direction side opening in the wire rod holding groove of a predetermined dimension provided in each piece corresponding to the diameter of the wire rod. The feature is that a taper portion that widens in the end face direction is provided.

That is, by providing a taper portion that widens toward the end face at a predetermined angle in the opening on the welding direction side in the wire gripping groove, both electrodes are moved toward each other to press and weld both end faces of the wire. In doing so, there is an action of surely guaranteeing the formation of the enlarged portion, which is the feature of the first invention of the present application, and the uniform overhang formation of the enlarged portion in the entire circumferential direction. Even if both electrodes are moved toward each other with a predetermined pressing force without providing this tapered portion and there is a gap for forming the enlarged portion, the enlarged portion buckles only in one direction due to the cut shape of both end faces of the wire. There is a fear of being formed into a state. The tapered portion according to the present invention acts as an anvil.

[0011]

[Experimental Example] A high-strength wire was used as a test material, and the end faces of two members cut by a hydraulic cutter were butt-welded using a welding machine equipped with the electrode according to the present invention, and the obtained test sample was subjected to various tests. Attached. Some of them are disclosed below.

A) Preparation of Specimen Specimen: Heat-treated deformed PC steel bar Class D, wire diameter 13.12 mm The mechanical properties of the specimen (n = 5) are shown in Table 1.

[0013]

[Table 1]

Welding machine: hydraulic pressure butt welding machine Welding electrode: The electrode of the present invention was used. One piece of the split type electrode used is shown in FIG. Reference numeral r denotes one piece of the split electrode, and a taper portion 4 that expands toward the end face at a predetermined angle is provided in the welding-side opening of the groove 3 formed to a predetermined depth corresponding to the wire diameter of the sample material. There is. Welding conditions: Welding was performed under the setting conditions shown in Table 2.

[0015]

[Table 2]

According to the above, ten test pieces were prepared. 2
When the members were welded, the electrodes were gripped by the electrodes so that the cut marks on both end faces were positioned so as to be axially symmetric, according to practical use. The maximum temperature during welding was measured with a radiation thermometer. The average value was 986 ° C. The maximum temperature of each sample is shown in Table 3 below.

B) Specimen Nos. 1 to 10 obtained as described above
All have a diameter of 32.3 mm, as shown in FIG.
A welded portion 10 was formed on each side of a welded bulge 1 having a width of 3.8 mm, which was inclined in the direction of the parallel portion and had an enlarged portion 2 having a maximum diameter of 21 mm and a length of 9 mm.

[0018]

[Table 3]

Each of the specimens obtained as described above was subjected to the following accuracy test. (1) Tensile test: Each specimen was subjected to a tensile test according to JIS standard to examine the mechanical properties. In the test, all specimens fractured in parallel. The test results are shown in Table 3.
In addition, a load elongation diagram for the sample No. 1 is illustrated in FIG.

The test results of the specimen shown in Table 3 are compared with Table 1 showing the mechanical properties of the specimen. Regarding the yield stress and tensile strength, it was confirmed that the numerical values of the specimens were almost the same as those of the specimens. Although the elongation at break is slightly reduced, it has passed the JIS standard for PC steel bars.

(2) Hardness measurement test: Specimen No. 10 including the welded portion was half-cut and the cut surface was subjected to a micro Vickers hardness test (Load: 500 g). The measurement position direction is indicated by an arrow in FIG. The measurement results according to the symbols (a) to (d) attached to the arrows are shown as (a) to (d) in FIG. From the observation of each figure, the characteristic point is the softened part (HV30
0) is located in the enlarged portion, and the welded portion 10 maintains substantially constant hardness (HV500 to 550) over the entire cross section.

[0022]

[Table 4]

(3) Metallographic Microscopic Observation Test: Specimen N
Each position of the cross section of o.10 was observed by taking a metallographic micrograph. The observation results are shown in Table 4 above.

From the above experimental results, although the enlarged portion of the high-strength one-turn auxiliary muscle H of the present invention has a slightly hardened portion, the strength deterioration is compensated by the size of the cross-sectional area of the enlarged portion, so that the entire welded portion It was confirmed that a high-strength one-turn auxiliary muscle that substantially maintains the mechanical properties of the high-strength wire material was obtained. At the same time, it was confirmed that the tapered electrode according to the present invention used in the welding machine can easily form the bulged portions which are circumferentially uniform on both sides of the welding bulge.

The present inventor carried out a welding experiment similar to the above using high-strength wire rods having wire diameters of 9.2 mm and 11 mm. It has been confirmed that the present invention can be carried out regardless of the wire diameter.

[0026]

Industrial Applicability According to the present invention, a reinforcing bar cage for construction and construction can be knitted with a high-strength one-turn auxiliary bar using a high-strength wire, which contributes to the improvement of the ultimate shear strength. Therefore, when designing the same ultimate shear strength as in the prior art, auxiliary bars with a small wire diameter are sufficient, and the finished dimensions of columns, beams, etc. can be reduced. Further, when welding for one turn, only the electrode of the welding machine is changed to the electrode according to the present invention, and no post-treatment is required. Therefore, it is possible to manufacture and provide a high-strength one-turn auxiliary bar at low cost.

At the same time, the use form of the lightweight high-strength 1-turn auxiliary bar replacing the high-strength spiral auxiliary bar that handles the entire length of the main bar, which is heavy, is the same as the conventional 1-turn auxiliary bar made of hot-rolled material. It will allow familiar bar operators to follow the conventional method, and will be prized for its ease of workability.

[Brief description of the drawings]

FIG. 1 (a) is a front view showing a state in which a conventional one-turn auxiliary bar is manufactured by welding a hot rolled material, and FIG. 1 (b) is a front view of a welded portion of the auxiliary bar obtained in (a). It is a figure.

FIG. 2 is a plan view and a side view showing one side of the split electrode of the welding machine for producing a high-strength one-turn auxiliary bar according to the present invention.

FIG. 3 is a front view showing a welded portion of the high-strength one-turn auxiliary muscle of the present invention.

FIG. 4 is a load elongation diagram in a welded portion tensile test of a high-strength one-turn auxiliary muscle.

FIG. 5 is an axial cross-sectional view showing a weld hardness measurement position of a high-strength one-turn auxiliary muscle.

6 (a) to 6 (d) are diagrams showing hardness measurement results at respective positions of a longitudinal section and a transverse section of a welded portion according to FIG.

[Explanation of symbols]

 W. . . High-strength wire H. . . High-strength one-turn assist muscle R. . . Electrode r. . . One piece of split type electrode 10. . Weld 1. . . Welding bulge 2. . . Huge section 3. . . Groove for holding wire 4. . . Tapered part

Claims (2)

(57) [Claims] 1. A welded portion of a one-turn auxiliary bar formed by butt-welding both ends of a high-strength wire cut into a predetermined length is provided on both sides of a welding bulge with swelled portions uniformly inclined in the circumferential direction in the parallel direction. High-strength one-turn auxiliary muscle characterized by being. 2. Each of the electrodes of the welding machine used when butt-welding both ends of a high-strength wire cut into a predetermined length to form an auxiliary bar for one turn, is relative to each other so that the wire can be clamped and held. In the case of a split mold composed of two facing pieces, a taper portion that widens in the end face direction at a predetermined angle is provided at the welding side opening of the wire gripping groove of each piece provided with a predetermined dimension corresponding to the wire diameter. An electrode of a welding machine for manufacturing a high-strength one-turn auxiliary bar, which is characterized by being provided.