JPH1037386A - Deformed steel bar having joint and used for reinforced concrete, the joint, and forming method for joint of deformed steel bar used for reinforced concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the strength of the joint of a deformed steel bar for reinforced concrete over the strength of a base material without thickening the joint and the jointed part of the deformed steel bar. SOLUTION: Only the surface projections 3 and 3a of the end of a deformed steel bar 1 for reinforced concrete are deformed to a flat state at a cold plastic working process, and the processed ends 6 and 6a are formed to have an approximately cylindrical shape of approximately the same diameter as the base 2 of the deformed steel bar 1. Then, external threads 7 and 7a are formed on the processed ends 6 and 6a at a cold plastic working process via thread rolling for use as joints 4 and 4a. In this case, the joints 4 and 4a are jointed to each other and hardened via the cold plastic deformation of the surface projections 3 and 3a, and the cold formation of the external threads 7 and 7a. The strength of the joints 4 and 4a is thereby increased over base material strength without being thickened. According to this construction, the surface projections 3 and 3a can be plastically deformed and the external threads 7 and 7a can be formed under a relatively small force, and the strength of the joints 4 and 4a more than the base material strength becomes available without thickening the joints 4 and 4a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deformed steel bar for a reinforced concrete having a joint for connecting a steel bar for a reinforced concrete (deformed steel bar), a joint thereof, and a method of forming a joint of the deformed steel bar for a reinforced concrete.

[0002]

2. Description of the Related Art Conventionally, deformed steel bars used for pillars of concrete buildings, etc., require increasing connection of deformed steel bars due to an increase in height of buildings, and a gas pressure welding method is known as such a connecting method. In the gas pressure welding method, specially shaped steel bars are butt-joined by pressing from both sides while heating the burner, but such gas pressure welding method requires special skills,
It has the drawback that good connections cannot be made unless it is a skilled worker, and also has the drawback that work must be interrupted during strong winds or rainfall.

Accordingly, a screw rebar has been invented. In a screw rebar (torque method), a screw-shaped rebar is screwed and connected with a coupler and both nuts. In a screw rebar (grout method), a solvent is used only with a coupler (grout material). ) Is filled and connected from the injection port.For such threaded reinforcing bars, special tools that apply high torque and expensive grout material are required in terms of construction work, and in the case of manufacturing, the reinforcing bar In order to obtain a screw shape, it requires high technology and troublesome labor, and has the drawback of increasing costs.

[0004] Further, only the end of the deformed steel bar is hot forged and formed into a larger diameter than the deformed steel bar, then cut to a predetermined size, and then threaded with material removal. In this case, a screw part made of a different material with higher strength is joined by friction welding, and the former cannot obtain the required strength unless the screw part has a large diameter, and the latter has the required strength. Although it can be obtained, there is concern about complete joining and unification due to joining of different materials, the diameter of the joint is large, the joint becomes thicker in any joint, and the gap between rebar and concrete in construction In that it has limitations in terms of fog thickness.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a deformed concrete for reinforced concrete having a joint portion capable of improving strength without increasing the thickness of the joint portion and the joint, and reducing the processing cost and stabilizing the quality. It is an object of the present invention to provide a method of forming a bar and a joint thereof, and a joint of a deformed bar for reinforced concrete.

[0006]

SUMMARY OF THE INVENTION The present invention is based on the above-mentioned prior art, and requires a special tool or expensive grout material at the time of construction of a thread reinforcing bar, or a problem which requires advanced technology and troublesome labor at the time of manufacturing, or Considering the problem of poor workability, poor handling, or the thickening of the connecting part when processing only the end of the deformed bar, only the surface protrusion of the deformed bar end for reinforced concrete is almost flattened by cold plastic working. After forming such a machined end into a substantially cylindrical shape having substantially the same diameter as the base portion of the deformed steel bar, an external thread is formed at the machined end by cold plastic working by thread rolling. By forming the joint with the joint, the deformation of the surface protrusion due to the plastic deformation in the cold and the formation of the external thread causes work hardening to increase the strength beyond the base metal strength without making the joint thicker, and plastic deformation Due to surface bump Deformation and formation of the male thread of, and allow the formation of a relatively small machining force, in the manner to reduce its processing cost is obtained by solving cents above drawbacks.

Also, in view of the problem that the joint becomes thicker, by not increasing the thickness of the joint as described above, the strength of the joint combining the connecting members is increased without increasing the thickness.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Reference numeral 1 denotes a deformed steel bar for embedding reinforced concrete. As shown in FIG.
Formed on the surface of the steel bar, which is the base 2 having a circular cross section, are ribs protruding in the axial direction and surface protrusions 3, 3a..., Such as bushes, protruding in the circumferential direction at regular intervals over the entire length. Joints 4 and 4a are formed at both ends of the deformed steel bar 1, and the joints 4 and 4a of the deformed steel bar 1 are connected by a connecting member 5 at a construction site or the like.

The deformed steel bar 1 shown in FIG. 2 (a) shows a non-processed state. At both ends Y of the deformed steel bar 1 (locations where the joints 4 and 4a are formed), surface protrusions 3, 3a. Only the middle X) is subjected to cold plastic working to form the joint portions 4 and 4a.

As shown in FIG. 2 (b), the joints 4, 4a are formed by cold plastic working to form surface protrusions 3, at both ends of the deformed steel bar 1.
3a... Are substantially flattened (two-dot chain line indicating the flattened state of the surface projections 3, 3 a...). After being formed into a substantially cylindrical shape having a diameter D1, as shown in FIG. 2 (c), an average diameter D2 is applied to the machined ends 6, 6a by cold plastic working by thread rolling.
Form external threads 7, 7a which are almost the same as the diameter D of the base 2 and the diameter D1 of the machined ends 6, 6a.

The shape and arrangement of the brushes are shown in FIGS.
In the case of a so-called horizontal brush as shown in the figure, it is preferable that the brushes on both sides which are divided into semicircles by a rib (up and down in the figure) are not arranged on the same circumference but are staggered at a predetermined interval. Since the uniform strength can be obtained as compared with those arranged on the same circumference, the former is better. However, the present invention is not limited to such a method.
When the plastic deformation of 3a is performed, it may be a continuous brush which can be uniformly work-hardened over the entire joints 4 and 4a.

The connecting member 5 is formed as a coupler 9 (long nut) having a screw hole 8 in which a screw thread is formed. The coupler 9 is rotated to connect the two deformed steel bars 1 and 1a. The both ends of the coupler 9 are fastened with nuts 10 and 10a to connect the deformed bars 1 and 1a.

Although the connecting member 5 has been described as including one coupler 9 and two nuts 10 and 10a, the connecting member 5 is not limited to such a system, but may be another type of connecting member. The shape is not limited at all, as long as the base portions 2, 2a of the joint portions 4, 4a are substantially cylindrical.

Next, the method of forming the joints 4 and 4a will be described with reference to FIGS. 2 and 3. First, as shown by the dashed line in FIGS. In the deformed steel bar 1, only the surface protrusions 3, 3 a... (Indicated by X in the drawing) at both ends Y, where joints 4, 4 a are formed, are drawn, rolled, cold-pressed, or the like. Cold plastic working,
That is, by the process of plastic deformation at a temperature below the recrystallization temperature,
As shown by the solid line at the left end in FIG. 2 (b) and FIG. 3, while maintaining the diameter D of the base 2, it is plastically deformed, crushed and compressed so as to be substantially flattened. And has a substantially cylindrical shape with a smooth surface having a diameter D1 substantially the same as the diameter D of the surface.

In FIG. 2 (b), the portion indicated by the two-dot chain line corresponds to FIG.
The surface projections 3, 3a... shown in (a) are crushed by the above-mentioned cold plastic working and are almost flattened. The cold plastic working of the crushed surface projections 3, 3a. Substantial material movement is due to the local processing of one end Y of the deformed steel bar.
As shown in FIG. 2 (b), the length of the deformed steel bar 1 is slightly longer in the length direction than in the non-machined state shown in FIG. 2 (a) so that it can be absorbed, and the surface protrusions 3, 3a. Work hardening increases static strength, impact strength and fatigue strength.

Next, plastic deformation is applied only to the surface layers of the processed end portions 6 and 6a by cold plastic working such as thread rolling, and the two-dot chain lines in FIGS. 2 (c), 4 and 3 are used. As shown,
The external threads 7, 7a whose average diameter D2 is almost the same as the diameter D of the base 2 and the diameter D1 of the processing ends 6, 6a are formed.

In the plastic deformation by cold plastic working such as rolling, in the case of threading by cutting, the crystal structure aligned in the axial direction obtained at the time of forming the material is interrupted. Male screw 7, 7a due to material swell
As a result, a continuous fibrous structure is obtained, and work hardening increases static strength, impact strength, and fatigue strength.

The maintenance of the continuity of the crystal structure by the plastic deformation is the same in the crushing step of the first step.
Through the crushing step of the step and the screw forming step of the second step, the strength of the joint portions 4 and 4a is set to be equal to or higher than the base material strength of the non-processed portion other than the joint portions 4 and 4a or the non-processed deformed bar 1. I have.

Further, the deformed steel bar 1 shown in FIGS.
Since the surface protrusions 3, 3a,... Are simply shown in the drawing, the non-formed portion A of the flattened state shown by the two-dot chain line in FIG. B is slightly larger than B, that is, on the same circumference, the width B of the flattened state does not seem to be the same as or larger than the part without the bulge (the non-formed part A of the bulge). As shown in the detailed view of FIG. 5, since the brush width B is wider than the non-molded portion A of the brush, a semicircular portion of the
However, since the work is hardened wider than the non-molded portion A of the brush, the strength of the portion interrupted in the radial direction on the same circumference is supplemented.

[0020]

Next, examples of the present invention are as follows.
Base material types SD295A and SD345, D25
The first step is drawn using a deformed steel bar (horizontal bar).
The second step was performed by thread rolling. As a result, the tensile strength of the joint was improved by about 10% with respect to the base metal strength in any of the deformed steel bars.

[0021]

According to the present invention, only the surface projections 3, 3a at the end of the deformed steel bar 1 for reinforced concrete are deformed by cold plastic working so as to be substantially flattened. Is formed into a substantially cylindrical shape having substantially the same diameter as the base portion 2 of the deformed steel bar 1, and the male screws 7, 7a are formed at the machined ends 6, 6a by cold plastic working by thread rolling. Joint part 4,
4a, the surface protrusions 3, 3a... Due to plastic deformation and the formation of the male screws 7, 7a are work-hardened to improve the strength compared to the non-processed portion (base material). The connecting member 5 can be made thinner without increasing the thickness of the portions 4 and 4a, and there is less restriction on construction such as a reinforcing bar interval and a cover thickness at a construction site than a conventional one.

Further, since the two joints 4, 4a are connected by the connecting member 5, in the embodiment, the connecting member 5 is formed as a coupler 9 having a screw hole 8, and the coupler 9 is connected to the joint 4, 4, 4a. Because the screws are screwed together, the deformed bars 1 and 1a can be connected simply by rotating the coupler 9 without rotating the deformed bars 1 for connection, and the connection work is easy and the construction efficiency is dramatically improved. It can be made, and the connection state can be strengthened.

Also, only the surface projections 3, 3a at the end of the deformed steel bar 1 for reinforced concrete are deformed by cold plastic working so as to be substantially flattened. The process ends 6, 6a are formed by a step of forming a substantially cylindrical shape having substantially the same diameter as the base 2 and a cold plastic working by thread rolling.
Forming the external threads 7, 7a on the joints 4, 4a
, The strength of the base metal is equal to or greater than the strength of the base metal, so that only the surface projections 3, 3a... Of the deformed steel bar 1 are cold-worked only. ,
3a... Or processing only on the surface of the base 2, requires only a small amount of processing power, simplifies equipment and reduces processing costs, and furthermore, due to plastic deformation of the surface projections 3, 3 a. The surface of the deformed steel bar 1 can be work-hardened without increasing the thickness of the joints 4 and 4a, and the strength of the joints 4 and 4a can be improved to be equal to or greater than the base metal strength.

Further, since the male screws 7 and 7a are formed by cold plastic working, the metal flows obtained in the forming of the material are arranged in the axial direction as in the case of forming the male screws by cutting. A continuous fibrous structure can be obtained without interruption of the connection of the continuous crystal structure, and work hardening improves static strength, impact strength and fatigue strength, and reduces the strength of the joints 4 and 4a. Its practical effect is extremely large, for example, it can be improved.

[Brief description of the drawings]

FIG. 1 is a front view of a deformed steel bar joint for reinforced concrete having a joint portion according to the present invention.

FIG. 2 is a process chart showing a method of forming a joint portion of a deformed steel bar for reinforced concrete.

FIG. 3 is a front view showing a process of processing a joint portion of a deformed steel bar for reinforced concrete.

FIG. 4 is an enlarged end view of FIG. 2 (c).

FIG. 5 is a front view showing a detailed form of a deformed steel bar for reinforced concrete.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deformed steel bar 2 Base part 3, 3a ... Surface protrusion 4, 4a Joint part 5 Connecting material 6, 6a Machined end part 7, 7a Male screw 8 Screw hole 9 Coupler 10, 10a Nut

Claims (3)

[Claims] 1. A method according to claim 1, wherein only the surface projection of the end of the deformed steel bar for reinforced concrete is deformed so as to be substantially flat by cold plastic working, and the processed end is substantially the same diameter as the base of the deformed steel bar. A deformed steel bar for reinforced concrete having a joint portion, wherein after forming into a cylindrical shape, a male screw is formed at the machined end by cold plastic working by thread rolling to form a joint portion. 2. The deformed steel bar joint for reinforced concrete according to claim 1, wherein the two joint portions are connected by a connecting member. 3. The surface projection of the deformed bar for reinforced concrete is deformed so as to be substantially flat by cold plastic working, and the processed end is substantially the same diameter as the base of the deformed bar. For reinforced concrete, comprising a step of forming a cylindrical shape, and a step of forming a male screw at the processed end by cold plastic working by thread rolling, wherein the strength of the joint portion is made equal to or greater than the base material strength. Method of forming joints of deformed steel bars.