JPH02241677A - Method for joining bar materials - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is applicable to reinforcing bars, pipes,
The present invention relates to a method for joining strips such as steel bars and shaped steel using diffusion bonding, which allows the work to be carried out easily and ensures reliable joint quality in a short period of time.

(Conventional technology) Conventionally, gas pressure welding and arc welding have been used to join strips such as reinforcing bars, pipes, steel bars, and shaped steel, but gas pressure welding is mainly used to join reinforcing bars. Widely used.

The gas pressure welding method is a method of joining by repeating the process of applying pressure while heating several times after abutting the joining surfaces to form a shape with sufficient bulge in the joining part.

Therefore, in the "Standard specifications for gas pressure welding of reinforcing bars" by the Japan Pressure Welding Association (Incorporated Association), regarding the bulge shape of the joints 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.

(i) In order to obtain a joint shape with sufficient bulge, an operator visually monitors the shape during welding and determines the heating temperature and pressurization timing of the reinforcing bars 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) Since the joint has a large bulge, 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, Japanese Patent Laid-Open No. 62-9785 and Japanese Patent Laid-Open No. 62-62- There is a method for joining reinforcing bars disclosed in Japanese Patent No. 16872.

The former improvement method involves inserting a piece of metal for joining between the end faces of the joint, heating it, and then applying pressure in the radial direction, rather than directly joining the joint parts.The latter method involves applying powder between the joint end faces. This is a method in which granular bonding metal is filled, heated, and then pressurized in the radial direction.

In these methods, by applying pressure in the radial direction to the reinforcing bars, that is, by not applying pressure in the axial direction to the reinforcing bars, the bulge of the joint does not become excessive, so stress concentration does not occur at the joint, and It is said that cracks in the concrete will not occur.

However, these methods also have the following drawbacks.

(i) Since the device is in close proximity to or in contact with heated reinforcing bars and joining metals, there is a problem that the device becomes hot, 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 using a low melting point metal material to suppress the heating temperature, the joint strength, bending strength, fatigue strength, etc. will decrease because the joint will be a joint with a low melting point metal material that is a different metal. There's a problem.

In addition, the present applicant has published “Unexamined Japanese Patent Publication No. 62-97784
A pair of clamp mechanisms connected by a connecting body clamp the two tubes to be welded with the insert material in between, and in this state, heat the vicinity of the abutting portions of the tubes to be welded.
As a result, excellent welding quality can be easily obtained, and a means that greatly contributes to improving construction efficiency has been provided.

(Problem H to be solved by the invention) According to this means, strips can be welded with a simple and inexpensive device, long-term heating at high temperatures is not required, and sufficient strength of the welded part can be maintained. can be secured. therefore,
The problems shown in (i) to 1ii) above can be solved.

But above! 1! Regarding the plan, there is a need to improve the quality of the welded part of the − layer, that is, to improve the joint shape, and to improve work efficiency, that is, to shorten the welding time. However, there has been a demand for a method for joining strips that can ensure sufficient joint strength by stabilizing the quality of the joint and further shorten the joining time.

The purpose of the present invention is therefore to provide a method for joining strips that can improve the shape of the joint with a simple device and method, stabilize the quality of the joint, ensure sufficient strength of the joint, and shorten the joining time. Our goal is to provide the following.

(Means for Solving the Problems) As a result of various studies in order to solve the above problems, the present inventors found that: (1) applying an initial load to the joining surface of the insert material; and (2) applying the initial load to the joint surface after applying the initial load. By heating the area nearby and applying pressure to the welded material multiple times during heating, the unwelded area is reduced and the oxide film on the joint surface is destroyed and removed, resulting in better welding. The present invention was completed by discovering that high quality parts can be obtained in a short period of time.

Here, the gist of the present invention is that when joining strips, (i) an insert material is held between the joining surfaces of the strips, and (i) the axis of the strips is aligned with respect to the joining surface. Applying an initial load in the direction to impart strain to the insert material, and then (iii) pressurizing the vicinity of the joint part once or twice or more in the axial direction of the strip material under heating to perform diffusion bonding. This is a method for joining strips characterized by the following.

In the present invention, the strip material includes reinforcing bars, pipes, steel bars, shaped steel, etc., but any strip material that can be joined by holding the insert material between the surfaces to be joined 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 foil between strips, by spot welding to the joint surface in advance, or by spraying powdered amorphous metal onto the joint surface. etc.

Furthermore, adding a certain initial load to the joint surface is not done with the purpose of simply sandwiching the insert material without adding any load, but is done with the purpose of actively applying a load to the joint surface and straining the insert material. is the purpose, 100 to 1
It is desirable to apply a load of about 200 kgf/-.
More preferably, the range is 200 to 800 kgf7cm'.

Further, when pressurizing is performed once or twice or more during heating, it is desirable that the pressure is 200 kgf/cm'' or more.

Heating methods include a method using a high-frequency heating coil, a method using gas heating, and the like. In either case, the heating device can be miniaturized, so on-site joining work is easy.

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 insert material. In order to prevent an undesirable alloy layer of the insert material from remaining on the joint surface after joining, the thickness is desirably 100 microns or less.

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

(Function) According to the joining method of the present invention, a constant initial load is applied to the joining surface into which the insert material is inserted in the axial direction of the strip, and then the vicinity of the joint is heated under heating. 1 in the axial direction
By applying pressure once or twice or more, it is possible to eliminate gaps caused by irregularities on the surface of the joining surfaces, melt the insert material while destroying the oxide film of the insert material, and perform liquid phase diffusion bonding in a short time.

By applying an initial load to the joint surface using an insert material, it is possible to prevent defects occurring in the joint portion due to irregularities on the surface of the joint surface. In addition, since the molten insert material uniformly wets the joint surface, the diffusion of elements in the insert material makes it easy to obtain a joint structure that is the same as the base metal structure on all joint surfaces, resulting in stable and good quality. It is possible to obtain a joint having a high joint strength.

In addition, by applying pressure once or twice during heating, the unbonded area is reduced and the oxide film on the bonding surface is destroyed and removed, resulting in even better bond quality in a shorter time. .

Furthermore, since the bonding is performed by liquid phase diffusion, there is no need for large pressurized deformations to ensure bonding strength, unlike gas pressure welding.

In other words, the initial pressurization only takes a short time, and as a result, the joint does not have an excessively bulging shape as in gas pressure welding, which reduces fatigue strength due to stress concentration at the joint and cracks after concrete is placed and hardened. can also be prevented.

Furthermore, when reinforcing bars are joined by the method according to the present invention,
Figure 5 shows the changes in the load applied to the joint surface and the measured values of the reinforcing steel surface temperature at the joint.The joining conditions in the example shown in Figure 5 are shown in Table 1.As the insert material, Fe
It is amorphous.

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

FIG. 1 is a schematic explanatory 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 workpieces 4 to be butted together with the insert material 5 sandwiched between the joining surfaces. The head 2 moves along the connecting body 1 by the jack 6 to apply a load to the joint surface in the axial direction of the workpiece 4.

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) and the second peak diagram show an example of an apparatus using a high-frequency heating coil 71 as a heating method.
Figure a) is a front view, and Figure 2(b) is a side view. In this device, the clamp mechanism 3 is made large enough to match the outer diameter of the material 4 to be welded, and the material 4 to be welded can be fixed with a fixing bolt 8 and a pin 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. Note that as a method for 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, FIG. 3(a) and FIG. 3(b) show an example of an apparatus using gas heating as the heating method.
The figure is a front view, and Figure 3(b) is a side view.The holding mechanism for the 0-strip material is the same as in Figures 2(a) and 2(b), but a ring burner 72 is attached as a heating device. Diffusion bonding is performed using a strong reducing flame in 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 set in the clamping mechanism 3, an amorphous metal body 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 2.

Table 2 The head 2 was moved by a hydraulic jack so that a load of 600 kgf/cd was applied in the axial direction of the reinforcing bars to the joint surface of the reinforcing bars sandwiching the amorphous metal material with a thickness of 25 microns, and the initial load was Added. The magnitude of the load was measured and controlled using a load cell.

Simultaneously with the application of this initial load, the vicinity of the joint was heated to 1200 to 1250° C. using strong reducing flame gas using a ring burner 72 provided above the joint.

Then, during this heating, pressure was applied to the materials to be joined multiple times. In this example, pressure was applied during heating twice in total, and the first time was applied 5 seconds after the start of heating. Start,
Pressure was applied for about 30 seconds. Also, the second pressurization is 4 times after the start of heating.
It was carried out for 5 seconds from 0 seconds until the completion of heating. Both pressurizations were carried out by adjusting the hydraulic jack so that a load of 300 kgf/cm'' was applied to the joint surfaces.

In this example, pressure was applied twice during heating, but the number of times of pressure application may be one as long as a butt state with no gaps etc. is obtained, or three or more times as long as the joint does not become large. It goes without saying that it is okay to pressurize.
The pressurizing conditions for the first pressurization and the final pressurization (corresponding to the second pressurization under the conditions of this example) are preferably within the range shown in Table 3.

Table 3 (Note) *: Indicates the elapsed time after the start of heating.

After heating for 45 seconds, the ring burner 72 is removed from the joint.
By moving away or stopping the gas supply, the temperature of the joint decreases and the joint stress decreases rapidly.

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 energization is stopped to reduce the temperature of the joint.

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 800 to 1300 degrees Celsius for the amorphous metal material normally used. That's about it.

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 tests conducted by the inventors as described above are shown in Tables 4 and 5. Table 6 also shows the bonding time in this test. Heating was performed using a ring burner, and Pressurization was performed twice.

The pressurizing force, pressurizing time, and pressurizing timing are summarized in Table 4.

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 4 also shows the results of the tensile test and the results of measuring the dimensions of the joint after joining.

In addition, as a comparison material, a test was conducted on a sample obtained by the conventional gas pressure welding method, and the results are also described.

Table 5 Table 6 From these results, the joints obtained by the method of the present invention fully satisfy the tensile test value specified in JIS G31125D35, and all fractures occurred in the base material, so It was found that the bonding strength was sufficient to exceed that of the materials used. Regarding the shape of the joint, as schematically shown in Figure 4, the reinforcing bar diameter is d, the joint diameter is D, and the length of the joint in the longitudinal direction is L. The results show that the bulge at the joint is smaller compared to the conventional method (gas pressure welding method).

Note that the conditions determined here are for the case where the materials shown 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 5, when bending tests were conducted on round bars, all 12 bars were bent to a bending opening of 180° using the method of the present invention, and the joints had sufficient bending ductility. It became clear that there was.

Further, as shown in Table 6, according to the method of the present invention, the joining time was 45 seconds, which was a significant reduction in the joining time compared to the gas pressure welding method (60 to 75 seconds).

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 of the Invention) As described above, the joining method according to the present invention uses a device with a simple structure and easy operation, inserts the insert material between the joining surfaces, and sets the initial load, heating time, pressurizing timing, etc. By doing so, it is possible to easily and reliably join, which eliminates the instability of quality due to differences in work skill level and inconsistent work conditions, which were problems with the conventional gas pressure welding method. I was able to resolve it.

In addition, since the bulge of the joint can be reduced, the stress concentration that occurs at the shoulder of the joint can be alleviated. Cracks can be reduced.

Furthermore, the bonding time was significantly shortened, resulting in a significant improvement in bonding efficiency compared to gas pressure welding.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle of the present invention; Fig. 2(a) and Fig. 2Cb1 are a front view and a side view, respectively, showing an example of the device of the present invention using a high-frequency heating coil as a heating method; Figures 3(a) and 3(b) are a front view and a side view, respectively, showing an example of the device of the present invention using gas heating as the heating method; Figure 4 is a schematic diagram of the bulge shape of the joint. and FIG. 5 are graphs showing the pressure applied to the end face of the materials to be joined and the temperature in the vicinity of the materials to be joined over time in one embodiment of the present invention. DESCRIPTION OF SYMBOLS 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: bottle,
10 Niji-l Revonx, 11: Load cell
71: High frequency heating coil 72: Ring burner

Claims (1)

[Claims] When joining strips, (i) an insert material is sandwiched between the joining surfaces of the strips, and (ii) an initial load is applied to the joining surface in the axial direction of the strips to bond the insert material. A method for joining strips, comprising applying strain, and then (iii) performing diffusion bonding by applying pressure in the axial direction of the strip once or twice or more in the vicinity of the joining portion under heating.