JPH0275478A - Method for joining bar materials - Google Patents

Abstract

PURPOSE:To easily and surely join the title materials by holding insert material between the joining faces and applying initial load on these faces and subjecting the vicinities of the joining faces to heating and diffusion joining. CONSTITUTION:The materials 4 to be joined are abutted on each other in a state with the insert material 5 held between the joining faces by clamp mechanisms 3 fixed on a connecting body 1 and a head 2. The head 2 is moved along the connecting body 1 by a jack 6 to apply load on the joining faces. Heating equipment 7 is placed on a joining part and the vicinity of the joining part is heated and subjected to diffusion joining. As a heating method, a high-frequency heating coil 71 is placed on the joining part and the vicinity of the joining part including the coil is surrounded by a seal box 10 and resistance joining is carried out in a nonoxidizing atmosphere by inert gas shielding such as Ar and N. In addition, a ring burner 72 is placed on the joining part and resistance joining in a reducing atmosphere is carried out by intense reducing flames by a heating method using gas heating. By this method, the initial load stress, heating time, etc., are set and easy and sure joining is carried out and the quality can be stabilized.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention applies diffusion bonding to joining work of strips such as reinforcing bars, pipes, steel bars, and shaped steel, which is performed at construction sites and other on-site work. The present invention relates to a method for joining strips, which allows easy work and ensures reliable joint quality.

(Prior Art) Gas pressure welding and arc welding are used as methods for joining strips such as reinforcing bars, pipes, steel bars, and shaped steel, but gas pressure welding is mainly used.

The gas pressure welding method is a method in which the joining surfaces are butted together, and then the process of applying pressure while heating is repeated several times to create a shape with sufficient bulge in the joint.

Therefore, in the Japan Pressure Welding Association's Standard Specifications for Gas Pressure Welding of Reinforcing Bars, the diameter of the joint is 1.4-1.
6 times the longitudinal bulge length of the joint is 1.
The bonding conditions are specified to obtain a sufficient bulge of 2-1.5 times.

However, this gas pressure welding method has the following drawbacks.

(1) In order to obtain a joint shape with sufficient bulge, workers visually monitored the shape during jointing and determined the heating temperature of the reinforcing bars and the timing of pressurization based on experience. Therefore, the work requires a high degree of skill, and the quality of the joint is unstable because the working conditions are not constant.

(ii) Due to the large bulge of the joint, stress concentration occurs at the shoulder of the joint, reducing fatigue strength.

Furthermore, after being embedded in concrete, cracks occur in the concrete around the joint due to stress concentration at the shoulder of the joint.

As an improvement method for the above-mentioned gas pressure welding method, where stress concentration occurs due to the shape of the joint and cracks occur after concrete is placed and hardened, JP-A-62
There are methods for joining reinforcing bars disclosed in Japanese Patent Application Laid-open No. 1978-9785 and Japanese Unexamined Patent Publication No. 16872/1983.

The former method does not directly join the joints, but instead inserts a metal piece between the end faces of the joint, heats it, and then applies pressure in the radial direction.The latter method creates a powder bond between the joint end faces. This is a method in which metal is filled, heated, and then pressurized in the radial direction.

These methods do not apply pressure in the axial direction to the reinforcing bars, so the bulge of the joint does not become excessive, so stress concentration does not occur at the joint, and cracks in the concrete do not occur.

However, these methods also have the following drawbacks.

(i) Since the device is close to or in contact with heated reinforcing bars and joining metals, there is a problem that the device becomes high temperature, and countermeasures such as using heat-resistant materials are required.

(ii) It is necessary to melt not only the joints of reinforcing bars but also the joining metal, which requires heating at high temperatures for a long time.

(iii) When a low melting point metal is used to suppress the heating temperature, the joint is a joint between dissimilar metals, which poses a problem in that the joint strength, bending strength, fatigue strength, etc. are reduced. - (Issues to be solved by the invention i! Il) The problems to be solved by the present invention are as follows.

(i) Since the bulge of the joint is excessive, the bulge of the joint should be kept as small as possible (
to do.

(ii) The joining work can be easily performed and the instability of joint quality caused by differences in skill levels and inconsistent working conditions can be eliminated.

As described above, there has been a desire for a method for joining strips that can improve the shape of the joint with a simple device and method, and also ensure sufficient joint strength by stabilizing the quality of the joint.

(Means for Solving the Problem) Here, the present invention fixes the strips on both sides with the insert material sandwiched between the joint surfaces, applies a certain initial load to the joint surfaces, and then heats the vicinity of the joint. This is a method for joining strips, characterized by diffusion joining.

Examples of the strip material include reinforcing bars, pipes, steel bars, shaped steel, etc., but any strip material that can be joined by sandwiching the surfaces to be joined with insert materials may be used.

As the insert material, a low melting point material such as an amorphous metal is desirable in order to shorten the time for diffusion bonding and to prevent quality deterioration due to oxides remaining in the bonded portion after bonding.

The insert material can be clamped to the joint surface by sandwiching the foil between strips, by spot welding the insert material to the joint surface in advance, or by spraying powdered amorphous metal onto the joint surface ( There are methods etc.

Furthermore, the purpose of adding a certain initial load to the joint surface is to actively apply load to the joint surface and strain the insert material, rather than simply sandwiching the insert material without applying any load. , it is desirable to apply a load of 300 kg/cd or more.

Heating methods include methods using high-frequency heating coils and methods using gas heating. In either case, the heating device can be made smaller, so on-site welding work is easy and the efficiency is equivalent to conventional pressure welding work. Excellent.

Regarding the bonding atmosphere, in the case of high frequency heating, under vacuum,
It is desirable to use a non-oxidizing atmosphere such as argon, nitrogen, or helium, and in the case of gas heating, it is desirable to use a strong reducing flame to create a reducing atmosphere.

Furthermore, the diffusion bonding time largely depends on the thickness of the Innocert material. In order to prevent the brittle alloy layer of the insert material from remaining on the joint surface after joining, the thickness is desirably 100 microns or less.

As a device for applying a load to the joint surface, there is a method of incorporating a hydraulic jack or the like into the strip clamping device.

(Function) According to the joining method of the present invention, by applying a certain initial load to the joining surface into which the insert material is inserted and then heating it, the insert material is melted while eliminating gaps caused by irregularities on the surface of the joining surface. Perform liquid phase diffusion bonding.

By applying an initial load to the joint surface using an insert material, it is possible to prevent defects that occur in the joint portion due to surface irregularities of the joint surface. In addition, since the molten insert material uniformly wets all the joint surfaces, the diffusion of elements in the insert material allows the same joint diameter as the base material & l weave to be obtained on all the joint surfaces, resulting in stable and good quality. It is possible to obtain a joint having a high joint strength.

Furthermore, because the bonding is performed by liquid phase diffusion, there is no need for large pressure deformations to ensure bonding strength, as is the case with gas pressure welding.
Therefore, unlike gas pressure welding, the joint does not have an excessively bulging shape, and it is possible to prevent a decrease in fatigue strength due to stress concentration at the joint and cracks after concrete is placed and hardened.

(Example) Hereinafter, specific examples of the present invention will be described using the drawings.

FIG. 1 is a diagram showing the principle of the present invention. A clamp mechanism 3 fixedly connected to the connecting body 1 and the head 2 causes the materials to be joined 4 to be butted together with the insert material 5 sandwiched between the joining surfaces. The head 2 is connected to the connecting body 1 by the jack 6.
A load is applied to the joint surface by moving along the .

Furthermore, a heating device 7 is placed at the bonding portion to heat the vicinity of the bonding portion to perform diffusion bonding.

Fig. 2(a) shows an example of an apparatus using a high-frequency heating coil as a heating method, and Fig. 2(a) is a front view, and Fig. 2(a) is a side view. In this device, the clamp mechanism 3 is made large enough to match the outer diameter of the workpieces 4, and the workpieces 4 are fixed by fixing bolts 8 and pins 9. Furthermore, the connecting body 1 is provided with a load cell 11 for measuring the load applied by the hydraulic jack 6 to the joint surface.

As a method of measuring the joint load, there is also a method of directly measuring the hydraulic pressure of the hydraulic jack 6 and managing the joint load.

In addition, in the illustrated example, a high frequency heating coil 71 is used as a heating device.
is placed at the joint, the vicinity of the joint including the coil is surrounded by a seal box 10, and the vicinity of the joint including the coil is shielded with an inert gas such as argon or nitrogen, thereby performing diffusion bonding in a non-oxidizing atmosphere.

On the other hand, Figures 3(a) and 3(b) show an example of an apparatus using gas heating as the heating method, with Figure 3(a) being a front view and Figure 3(b) being a side view. The holding mechanism for a certain 0-strip material is the second one.
Same as the figure, but with a ring burner 72 as a heating device.
is placed on the joint, and diffusion bonding is performed using a strong reducing flame to create a reducing atmosphere.

A joining operation using this device will be explained based on an example.

First, a reinforcing bar serving as the material to be joined 4 was placed in the clamping mechanism 3, an amorphous metal material was sandwiched as an insert material 5 on the joint surface, and the reinforcing bar was fixed by tightening the fixing bolt 8 of the clamping mechanism 3.

The reinforcing bars and insert materials used here are shown in Table 1.

Table 1 The head 2 was moved by the hydraulic jack 6 so that a load of 400 kg/- was applied to the joint surface of the reinforcing bars sandwiching the amorphous metal material with a thickness of 25 microns. The load was measured and controlled using a load cell.

After applying the constant load, a ring burner 72 installed on the joint is used to heat the vicinity of the joint with strong reducing flame gas.
Heated to 200-1250°C.

The bonding stress applied to the bonding surface temporarily increases due to thermal expansion of the reinforcing bars due to this temperature rise, but the bonding stress decreases due to plastic deformation due to softening of the material.

After heating for one minute, by moving the ring burner 72 away from the joint or stopping the gas supply, the temperature of the joint decreases and the joint stress sharply decreases.

Thereafter, the bolt 8 of the clamp mechanism 3 is loosened and the reinforcing bar is removed from the device.

On the other hand, when using a high-frequency heating coil as a heating method, non-oxidizing gas is blown into a seal box installed near the joint to create a non-oxidizing atmosphere, and then the high-frequency heating coil is energized to heat the vicinity of the joint. be done.

After energization for a certain period of time, the temperature of the joint decreases by stopping the energization.

The above is an example of joining with reinforcing bars, but the heating temperature is not constant because the melting point changes depending on the composition of the amorphous metal material used as the insert material, but it is around 900-1300°C for the amorphous metal commonly used. It is.

On the other hand, the initial stress applied to the bonding surface and the heating time also vary depending on the type and composition of the materials to be bonded, the surface roughness of the bonding surface, the insert material, etc. for diffusion bonding.

In addition, the conditions are determined because it is necessary to ensure the bonding strength and to minimize the bulge in the bonded portion.

The results of the preliminary tests conducted by the inventors as described above are shown in Table 2, which includes the initial stress applied to the joint surface to determine the joining conditions, and the number of inserts (25 micron thick) inserted. A bonding test was conducted by changing the conditions of , and heating time. The heating method used was gas heating using a ring burner.

Thereafter, a tensile test was conducted on the tensile test piece including the joint portion according to the tensile test method specified in JIS G3112 Steel Bars for Reinforced Concrete. Table 2 also shows the results of the tensile test and the results of measuring the dimensions of the joint after joining.

As a comparative material, tests were also conducted using the conventional gas pressure welding method, and the results are also listed.

From these results, the joint made by the method of the present invention sufficiently satisfies the tensile test value specified in JIS G31125D35 by setting the initial stress to 300 kir/- or more and the heating time to 30 seconds or more. It was found that the fracture position also had sufficient bonding strength with the base metal.

Regarding the shape of the joint, as shown schematically in Figure 4, if the diameter of the reinforcing bar is d1, the diameter of the joint is D, and the bulge length in the longitudinal direction of the joint is L, then from Table 2, the shape of the joint is It has been found that the bulge of the joint can be kept small by setting the applied initial stress to 1000 kg/- or less.

Note that the conditions determined here are for the case where the materials listed in Table 1 are used, and if the materials to be joined and insert materials are changed,
Needless to say, the bonding conditions will change.

In addition, as shown in Table 3, using a rod-shaped test piece prepared under the conditions adopted in the example (condition 7 in Table 2) and with the bulge removed at the joint, bending around the joint was performed. angle 1
As a result of conducting an 80' bending test on 10 test pieces each,
With the method of the present invention, all the results were good with no cracks, but with the conventional gas pressure welding method, there was one joint fracture and one joint with cracks, and oxides remained on the fracture surface. Was.

In addition, although reinforcing bars have been explained in the examples as materials to be joined to which the method of the present invention is applied, the present invention is not limited thereto, and can also be applied to tubular strips, steel bars, shaped steel, etc. .

(Effects) As described above, the bonding method according to the present invention uses a device with a simple structure and easy operation, inserts the insert material between the bonding surfaces, and sets the initial applied stress, heating time, etc.
Since it is possible to perform bonding easily and reliably, it eliminates the instability of quality caused by differences in work skill level and inconsistent work conditions, which were problems with the conventional gas pressure welding method. done.

Furthermore, since the bulge at the joint can be reduced, the stress concentration that occurs at the shoulder of the joint can be alleviated, preventing damage due to a decrease in fatigue strength and cracking of the concrete around the joint, which have been problems in the past. You can.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of the present invention; Fig. 2 (δ) and Fig. 2 (b) are a front view and an example of the device of the present invention using a high-frequency heating coil as a heating method, respectively; Side view; FIGS. 3(a) and 3(b) are a front view and a side view, respectively, showing an example of the apparatus of the present invention using gas heating as a heating method; and FIG. 4 is a view of the joint. It is a typical explanatory view of a bulging shape. 1: Connecting body, 2: Head, 3: Clamp mechanism, 4: Joined material, 5: Insert material, 6: Jacket, 7: Heating device,
71; High frequency heating coil, 72; Ring burner, 8: Fixing bolt, 9: Tong, lO: Seal box, 11; Load cell applicant Kajima Corporation (1 other person) agent Patent attorney Akira Hirose - 42 (1) f5 Rimo 3 (Q) TM No. 4 concave 2 (b) concave L3 (b) WJ

Claims (1)

[Claims] In joining strips, (i) insert material is held between the joining surfaces, (ii) initial load is applied to the joining surfaces, and (iii)
) A method for joining strips, characterized by diffusion joining by heating the vicinity of the joint.