JP2002180601A - Screw joint for steel rod and steel rod joining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw joint for screw-coupling steel rods with male screws on the outer peripheries of their ends with a coupler at 0 deg.C or lower without causing losseness, and a steel rod joining method. SOLUTION: The screw joint comprises the steel rods 2 and the coupler 3 fixed together by using a hardened material having a compression elastic modulus of 1500 N/mm2 or more obtained by injecting an acrylic adhesive A from a small through-hole 4 provided in the coupler 3, followed by filling in a gap between the steel rod 2 and the coupler 3 and hardening. The method of jointing the steel rods 2 comprises using the joint.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a threaded joint of a steel rod in which steel rods having an external thread on the outer periphery are screwed together with a coupler having an internal thread on the inner surface, and a method of joining steel rods.

[0002]

2. Description of the Related Art Conventionally, welding of steel bars (steel rods) used in civil engineering and construction work has been performed by welding. However, from the viewpoint of shortage of skilled welders and labor saving of construction work, a joint using a coupler and a joining method have attracted attention as a means to replace welding. This is a screw joint and a joining method in which an end surface of a steel rod (threaded rebar) formed with a male screw is abutted on the outer periphery of the end portion of the steel rod or the entire outer circumference, and a coupler having a female screw formed on the inner surface thereof is screwed with the end surface. This is a construction method that has a large labor saving effect at the construction site.

[0003] In the case of screwing using a coupler, the stress generated in the joint is transmitted by the screwing of a male screw and a female screw. Therefore, in the screw joint, the screwing length of the steel rod and the coupler is secured to a certain length or more. If so, a joint strength sufficiently exceeding the lower limit of the standard of the base steel bar should be achieved. But,
Actually, the dimensional accuracy of the thread of the steel rod is low, and a gap of a maximum of several millimeters, so-called "play" exists between the steel rod and the coupler. For this reason, the rigidity of the threaded joint is significantly lower than the standard value of the base steel bar. When such a steel rod having a threaded joint having a "gap" is used as a reinforcing material for concrete, there is a problem that the "gap" cracks the concrete near the screwed joint.

As a means for solving the above problem, Japanese Utility Model Laid-Open Publication No. 51-54420 discloses that a gap formed between a steel bar and a coupler is filled with an organic or inorganic curable substance called a grout material. There is proposed a method of curing and eliminating "play". An epoxy resin (adhesive) has been proposed as an organic grout material or a main component thereof (Japanese Utility Model Publication No. 55-4410-1).

[0005]

The epoxy resin is used as an organic grout material or as a main component thereof because the epoxy resin after curing has low water absorption, low curing shrinkage, and high mechanical strength. Depends on characteristics. However, when the temperature of the epoxy resin is lowered to 0 ° C. or less, the fluidity is extremely reduced, and the reactivity with the curing agent is lowered to prevent the epoxy resin from being cured. There was a problem that it could not be used. The present invention has been made in order to solve these problems, and a steel rod having an external thread on the outer periphery using an organic grout material that can be used at a low temperature of 0 ° C. or less (screw bar).
And a method for joining the steel rod and the steel rod.

[0006]

That is, according to the present invention, at least the ends of steel bars provided with male threads on the outer periphery of the ends are abutted with each other, and a coupler provided with an internal thread on the inner face is screwed into the male rod. In a threaded joint of a steel rod in which the formed gap is filled with an adhesive cured product, the cured product is a cured product of an acrylic adhesive having a compression modulus of 1500 N / mm ² or more. It is a screw joint.

[0007] Further, the present invention provides a method in which a male
Butt the ends of the threaded steel bars and insert the
Screw with the coupler provided on the surface, and insert between the male screw and female screw.
Fill the gap with acrylic adhesive and cure it,
A method of joining steel bars to fix the coupler to the
Compression elastic modulus of cured product of metal-based adhesive is 1500 N / mm ^Two
A method of joining steel bars, characterized by the above.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a steel rod having at least one end provided with a male screw at its outer periphery, which is screwed together with a coupler having a female screw provided on the inner surface thereof. This is a method of joining a threaded joint of a steel rod filled with a hardened material and joining the steel rod using the joint.

(Steel bar) The material of the steel bar used in the present invention,
The thickness and length are not particularly limited, but are preferably the material, thickness and length used as a reinforcing material for reinforced concrete. For example, the thickness is about 15 to 50 mm. Threads are engraved on the outer periphery of the steel bar at a part or end including the entire length and end. Thread pitch, height,
The nodal width and the radius of the nodal bottom are not particularly limited,
Generally, the pitch is 8 to 20 mm, the knot height is 1 to 5 mm, the knot bottom width is 4 to 15 mm, and the knot bottom radius is about 0.5 to 3 mm.

(Coupler) The material, thickness, wall thickness and length of the coupler used in the present invention are not particularly limited, but can be screwed together with a steel rod used as a reinforcing material for reinforced concrete. Material, thickness, thickness and length must be used. The coupler is provided with small through holes, which are injection ports for the acrylic adhesive, at appropriate locations. The diameter of the small hole may be about 5 mm.

(Acrylic Adhesive) The acrylic adhesive used in the present invention has a lower viscosity at a lower temperature than a conventional epoxy resin. It can be easily injected into the gap created between the male screw and the female screw of the coupler. In addition, since the acrylic adhesive has a higher polymerization (curing) rate at a lower temperature than a curing rate of the epoxy resin, it can be effectively used in winter in cold regions.

[0012] The acrylic adhesive refers to a composition of an acrylic monomer and / or oligomer and a polymerization initiator, the composition comprising the monomer and / or oligomer. The acrylic adhesive used in the present invention is preferably a two-component curing type from the viewpoint of workability, but may be a one-component curing type. In the case of the two-pack type, the acrylic monomer and / or oligomer, which is the main component of the adhesive, and the polymerization initiator, which is a catalyst, are mixed immediately before application, and injected into the gap between the steel rod and the coupler. Used as

The acrylic monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; methyl methacrylate,
Poly (meth) acrylates such as ethyl methacrylate, propyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate (meth) acrylate, polypropylene glycol dimethacrylate, trimethylolpropane trimethacrylate, acrylic acid, methacrylic acid, etc. No. These monomers may be used alone or in combination of two or more. These monomers may contain one or more oligomers or co-oligomers. These oligomers and co-oligomers containing no monomer can be used alone or in combination of two or more.

In addition to the monomers and oligomers, rubbers such as diene rubbers, acrylic rubbers, and urethane rubbers may be contained for the purpose of improving the impact resistance of the obtained cured product. Examples of the diene rubber include polybutadiene, chloroprene rubber, acrylonitrile / butadiene copolymer rubber, styrene / butadiene copolymer rubber, and hydrides thereof. A commercially available acrylic adhesive can also be used. Commercially available products include "Bolt Rock 3 (manufactured by Denki Kagaku Kogyo Co., Ltd.)" and "CF Putty R (Denki Chemical Industry Co., Ltd.)
Manufactured)).

As the polymerization initiator, an organic peroxide usually used as a catalyst for an acrylic adhesive can be used. For example, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide,
Examples thereof include di-t-butyl peroxide and lauroyl peroxide.

When the acrylic adhesive of the present invention is polymerized at a low temperature of 0 ° C. or lower, it is preferable to include a curing accelerator and start the polymerization by a redox reaction. As a curing accelerator, a condensate of butyraldehyde with a primary amine such as aniline or butylamine; amines such as N, N-dimethylaniline, triethylamine, diethanolamine, diethyltriamine, and triethylenetetramine; thiourea, ethylenethiourea Thioureas; and metal compounds such as cobalt naphthenate, copper naphthenate, and vanadium pentoxide. Preferred are condensates of butyraldehyde and primary amines such as aniline or butylamine.

The type and content of the polymerization initiator and the curing accelerator are adjusted according to the curing speed of the acrylic adhesive, but generally, 100 parts by mass of a main component comprising an acrylic monomer and / or oligomer. On the other hand, the content of the organic peroxide is 1.0 to 10 parts by mass, and the content of the curing accelerator is 0.1 to 10 parts by mass.
It is 0.5 to 5 parts by mass.

(Method of Injecting Acrylic Adhesive) A typical example of the injection method of the present invention is a case where a two-part curable acrylic adhesive is polymerized in a redox system using the above-described organic peroxide and a curing accelerator. Here is an example. That is, in the grout injection device, the piston is pushed with a hand gun, and the composition of the acrylic monomer and the organic peroxide sealed in the syringe A, and the composition of the acrylic monomer and the curing accelerator sealed in the syringe B are used. It is a method of extruding and injecting through a through hole of a coupler from a nozzle while mixing both compositions with a static mixer.

An organic peroxide is applied to the outer periphery of the steel rod and / or the inner surface of the coupler in advance, and the steel rod and the coupler are screwed together. Then, a composition of an acrylic monomer and a curing accelerator is passed through the coupler. It may be injected through a small hole. Also,
After applying a curing accelerator to the outer periphery of the steel rod and / or the inner surface of the coupler in advance and screwing the steel rod with the coupler, the composition of the acrylic monomer and the organic peroxide is injected through the through hole of the coupler. You may. The organic peroxide is microencapsulated by a coacervation method using gelatin, so that a one-liquid type in which an acrylic monomer, a microencapsulated organic peroxide, and a curing accelerator are mixed is used. You may.

(Acrylic resin cured product) The curing time of the acrylic adhesive depends on the type and content of the acrylic monomer, polymerization initiator, curing accelerator, and the like, and varies greatly depending on the curing temperature. It's hard to do,
From the viewpoint of workability, the gel time is adjusted to 15 minutes to 2 hours, and the complete curing time is adjusted to about 1 to 4 days.

The compression modulus of the cured product of the acrylic adhesive must be 1500 N / mm ² or more. When the threaded joint is pulled, a compression load is applied to the cured product of the acrylic adhesive filled in the gap between the male screw of the steel rod and the female screw of the coupler, so that the compression elastic modulus of the cured product of the acrylic adhesive is 1500 N / mm. If it is less than ² , the deflection of the threaded joint increases, which is not practical. Preferably, the cured product has a compression modulus of 1500 to 5500 N / mm ² . In addition,
The compression elastic modulus is a value measured at 25 ° C. according to JIS K 6911. The cured product has a compression modulus of 1500 N
In order to increase the ratio to / mm ² or more, a method of increasing the proportion of a monomer having a high glass transition temperature, such as methyl methacrylate, or adding an inorganic filler that does not easily react with the polymerization initiator may be used.

In a construction site, for example, when fixing a vertical steel bar and a horizontal steel bar, the crossing portion of the steel bars is changed to a method of binding with a wire, and a two-component curable acrylic adhesive is used. A method has been proposed in which an agent is applied, cured, and a steel bar is joined (Japanese Patent Laid-Open No. 4-131467). In this case, the cured product of the acrylic adhesive needs properties such as compression strength, tensile strength, refraction strength, and elongation, but it is sufficient that the compression strength is about 200 N / mm ² . Therefore, as a two-part curable acrylic adhesive,
Chlorsulfonated polyethylene, (meth) acrylate-based monomer containing organic peroxide (solution A),
What consists of NBR and a (meth) acrylate-based monomer (solution B) containing an amine-aldehyde condensate-based curing accelerator is used.

The specifications of a threaded joint in which a steel rod is screwed with a coupler by a tensile test are as follows. A tensile load is applied to the threaded joint to 95% of the yield strength of the steel rod as the base material,
Next, the load is changed to a compressive load, compressed to 2% of the yield strength, a tensile load is applied again, and a tensile load is applied until yielding. The modulus of elasticity of the base steel rod is E ₀ , the apparent elastic modulus E ₇₀ obtained by dividing the stress at 70% of the yield strength of the steel rod when a tensile load is first applied by the cross-sectional area, and the initial tensile load is The apparent elastic modulus E ₉₅ obtained by dividing the stress at 95% of the yield strength of the steel bar when added by the cross-sectional area, and 2% of the yield strength
When the amount of slip of the joint when compressed to δ is δ,
₇₀ / E ₀ > 0.9, E ₉₅ / E ₀ > 0.7, δ ≦ 0.3 m
m must be satisfied.

[0024]

EXAMPLE 1 As shown in FIG. 1, two end faces of a threaded bar 2 (diameter: 31.8 mm, thread pitch: 17.0 mm, node height: 2.4 mm) were butted together, and a steel coupler was used. 3 (length 185 mm, inner diameter 31.8 mm, wall thickness 9.6
mm, screw pitch 17.0mm, screw height 2.8mm)
Were screwed together and fixed to construct a threaded joint 1. The threaded joint 1 was left in a freezing room cooled to −10 ° C. and cooled to that temperature. Commercially available two-part curable acrylic adhesive A (“Bolt Lock 3”,
Using a manual grouting device, a small through-hole 4 of the
(5 mm in diameter), the adhesive was injected into the inner surface of the coupler, and continued until the adhesive A leaked from both ends of the coupler 3. The adhesive A enters a gap between the threaded bar 2 and the coupler 3 and a gap between butted surfaces of the end faces of the threaded bar 2 to fill the gap. After being left in a freezer at -10 ° C for 4 days to cure the adhesive A, the obtained threaded joint 1 was taken out of the freezer.

The tensile test of the threaded joint 1 was performed at room temperature. E ₇₀ , E ₉₀ , and δ were read from the test curve, and E ₇₀ / E ₀ , E
It was calculated ₉₅ / E _0. The results are shown in Table 1. FIG. 2A shows a schematic diagram of a stress-strain curve of a tensile test. Further, the threaded joint 1 was cut in the longitudinal direction, and it was confirmed that the cured product of the adhesive A was filled in the gap generated between the reinforcing bar and the coupler. Further, the acrylic adhesive A was poured into a plate-shaped mold, cured at 23 ° C. for 4 days, cut out of a test piece, and the compression modulus was determined at 25 ° C. according to JIS K6911. The results are shown in Table 1.

Example 2 A two-part curable acrylic adhesive B ("CF Putty R") shown in Table 1 was manufactured by Denki Kagaku Kogyo Co., Ltd.
Threaded joint 1 in the same manner as in Example 1 except that
And a test was conducted in the same manner as in Example 1. The stress-strain curve of the tensile test was the same as in Example 1. The results are shown in Table 1. Further, the threaded joint 1 was cut in the longitudinal direction, and it was confirmed that the cured product of the adhesive B was filled in the gap generated between the reinforcing bar and the coupler.

(Comparative Examples 1 and 2) Two-part curable acrylic adhesive C ("Bolt Rock 1", manufactured by Denki Kagaku Kogyo KK) and adhesive D ("SG350H", Nogawa Chemical) shown in Table 1 A threaded joint 1 was produced in the same manner as in Example 1 except that the same was used, and a test was conducted in the same manner as in Example 1. FIG. 2 (2) is a schematic diagram of a stress-strain curve of a tensile test.
It was shown to. In each case, the yield strength of the rebar base material was about 3
The slope changed around 0%. This is thought to be due to the fact that the threaded joint is greatly deformed because the compression modulus of the cured product is small, but this cannot be put to practical use. Further, the threaded joint 1 was cut in the longitudinal direction, and it was confirmed that the cured product of the adhesives C and D was filled in the gap generated between the reinforcing bar and the coupler.

From the results of Examples 1 and 2 and Comparative Examples 1 and 2, in the case of an acrylic adhesive, the adhesive is filled into the gap between the thread-bar rebar (steel rod) and the coupler at a temperature of -10 ° C. It can be seen that when the compression modulus is 1500 N / mm ² or more, the standard of the tensile test of the threaded joint can be satisfied. On the other hand, when the compressive strength is less than 1500 N / mm ² , the deformation is large and is not practical.

(Comparative Example 3) A two-part curing type epoxy adhesive ("Araldite AW2104", manufactured by Ciba Specialty Chemicals Co., Ltd.) shown in Table 1 was used at a temperature of -10 ° C. in the same manner as in Example 1. Tried to inject through the through hole of the coupler, but the viscosity was so high that it could not be injected.

Comparative Example 4 A two-part curing type epoxy adhesive ("Araldite AW2104", manufactured by Ciba Specialty Chemicals Co., Ltd.) shown in Table 1 was used in the same manner as in Example 1 to reduce the penetration of the coupler. After pouring at 20 ° C through the hole,
Immediately, the threaded joint 1 was moved to a freezer at −10 ° C. Thereafter, as in Example 1, it was left in the room at −10 ° C. for 4 days. A tensile test was performed in the same manner as in Example 1. The results are shown in Table 1. In the case of an epoxy-based adhesive, it is difficult to inject at a temperature of -10 ° C, and even if it can be injected, it cannot satisfy the standards of the book test because of insufficient curing.

[0031]

[Table 1]

[0032]

According to the screw joint and the joining method using the coupler of the present invention, the steel rod can be securely fixed even at a low temperature of -10 ° C., which cannot be fixed by the conventional screw joint and the joining method using the coupler. it can. Therefore, it is possible to greatly reduce the work time and labor for construction and civil engineering work in winter in cold regions.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a threaded joint of the present invention.

FIG. 2 is a schematic view showing one example of a stress-strain curve in a tensile test of a threaded joint. (1) is the case of the first and second embodiments.
(2) is the case of Comparative Examples 1 and 2.

[Explanation of symbols]

 1: threaded joint 2: threaded bar (steel bar) 3: steel coupler 4: small through hole (injection port) A: grout material (acrylic adhesive)

 ──────────────────────────────────────────────────の Continued on the front page (71) Applicant 000200264 Kawatetsu Techno-Research Co., Ltd. 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo (72) Inventor Shigeru Takano 1st Kawasakicho, Chuo-ku, Chiba-shi, Chiba (72) Inventor Tetsu Nariya 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Pref. Kawasaki Steel Research Institute Co., Ltd. (72) Inventor Masazumi Izawa 2-3-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo Kawasaki (72) Inventor Hideya Soma, 1135 Nakamura, Shibukawa-shi, Gunma Denki Kagaku Kogyo Co., Ltd. (72) Inventor Tsutomu Takeda 1135 Nakamura, Shibukawa-shi, Gunma Denki Kagaku Kogyo Co., Ltd. Inventor Hideo Kondo 10-13-13-1-1 Kanai, Nishi-ku, Sapporo-shi, Hokkaido Inside Toyohira Steel Corporation (72) Inventor Isao Takahashi Chiba Leaf Chuo-ku, Kawasaki-cho, address 1 Kawasaki Steel Te Techno Research Co., Ltd. in the F-term (reference) 2E164 AA02 BA02 BA25 BA27

Claims (2)

[Claims] 1. An end face of steel rods provided with male threads at least at the outer periphery of the ends is abutted with each other, and a coupler provided with an internal thread on an inner face is screwed together, and a gap formed between the male thread and the female thread is filled with a cured adhesive. A threaded joint for a steel rod, wherein the cured product is a cured product of an acrylic adhesive having a compression modulus of 1500 N / mm ² or more. 2. An end face of steel rods provided with male threads at least at the outer periphery of the ends is abutted with each other, a coupler is screwed into the gaps, and a gap formed between the male threads and the female threads is filled with an acrylic adhesive;
A method of joining a steel bar and a coupler by curing the same, wherein the compression modulus of the cured product of the acrylic adhesive is 15
A method for joining steel rods, wherein the method is at least 00 N / mm ² .