JPS6111718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for joining reinforcing bars, etc. by gas pressure welding, and more specifically, the present invention relates to a method for joining reinforcing bars, etc. by gas pressure welding, and more specifically, to join reinforcing bars, steel bars, steel pipes, shaped steel, etc. used in civil engineering and building structures, by joining joints and bases. The present invention relates to a joining method for joining materials by gas pressure welding without creating geometrically discontinuous parts such as notches where materials are connected.

Conventionally, gas pressure welding has been used to join reinforcing bars in civil engineering and building structures. This method is
This is a method in which metal atoms are diffused between the end faces by pressurizing the end faces of reinforcing bars and heating them with a mixed gas of acetylene and oxygen, thereby bonding the end faces together. According to this gas pressure welding method, the end faces can be easily bonded by diffusion of metal atoms, etc., and the cross-sectional area of the joint can be increased by the pressure applied during bonding, thereby increasing the strength of the joint. However, in order to increase the cross-sectional area of the joint, sharp notches often occur where the joint and the base metal connect, and furthermore, as the diameter of the joint increases, the grain size of the joint decreases. It becomes bulky and loses its strength, especially when used at low temperatures in cold regions, and often breaks from this part.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and specifically, when the end faces of reinforcing bars are pressure-welded and the diameter of the joint is increased, notches, etc. occur at the connection between the joint and the base metal. On top of that, without letting
We propose a gas pressure welding method that produces joints with excellent toughness and mechanical properties at low temperatures and a large cross-sectional area.

The method of the present invention will be explained in detail below.

First, steel bars, steel pipes, etc. are butted together and pressurized from the axial direction, and in this state they are heated with a mixed gas containing acetylene, propane, oxygen, etc. At this time, first, the end faces are heated by applying a high axial pressure of 5 to 6 Kgf/mm ² and heated by a reducing flame to press the end faces together, and then, in the final step, the end faces are pressed together in the axial direction and in the direction orthogonal to the axial direction. A large-diameter joint is formed in a three-dimensional stress state by applying pressure from

Therefore, the diameter of the joint is increased to increase the strength of the joint, and the structure becomes fine grained, so that the fatigue strength of the joint is improved to the same level as that of the base material.

First, FIG. 1 shows an example of a conventional gas pressure welding method, and FIG. 2 shows an example of a gas pressure welding method according to the present invention. As is clear from Figure 1, in the conventional method, 3 to 4 Kgf/
An axial pressure of mm ² is applied, and in this state, the metal atoms are diffused between the end faces by heating with a strong reducing flame for about 1 minute. Then, in step B, the adhesion between the end faces is improved and the metal In order to promote atomic diffusion, pressurize again by applying axial pressure of 3 to 4 Kgf/mm ² for several seconds.
Gas pressure welding.

Next, after gas pressure welding in this way, the gas flame was switched from a strong reducing flame containing too much acetylene gas to a standard flame with a flow rate ratio of 1:1 of acetylene and oxygen, and this standard flame was used to tear off the end face of the reinforcing steel. Sandwich the reinforcing bar diameter from 1.0 to
After heating 1.5 times the width for about 30 seconds to 1 minute to perform so-called width baking (step C), and finally in step D, the axial pressure is increased to 3 to 4 Kgf/mm ² and the standard flame is heated to 5. Heat for about 10 seconds to expand the diameter of the joint to about 1.4 times the diameter of the reinforcing bar, increasing the strength of the joint.

On the other hand ^, in the method of ^the present invention, as shown in FIG.
Heating with reducing flame under 6Kgf/mm ² and press-welding the end faces. In other words, in process A', the axial pressure is high and the end faces are in close contact, so the diffusion of metal atoms is sufficiently promoted, and the distance between the end faces is improved even without increasing the axial pressure in process B, as in the conventional method. Good gas pressure welding can be achieved by heating for about 30 seconds to 1 minute, and then the process can immediately proceed to widening by standard flame heating (C' step) and large diameter joint part formation (D' step).

In this step C', width printing is performed in the same manner as in step C of the conventional method. Also, in the D′ process,
A large-diameter joint is formed in the same manner as in step D of the conventional method, but at this time, in order to give the large-diameter joint a forging effect and to refine the structure, the large-diameter joint is formed as shown in Figures 3 and 3. Cover it with the cylindrical jig shown in Figure 4, and
The axial pressure is increased to about 5 to 6 Kgf/mm ² , and a pressing force from a direction perpendicular to the axis (that is, radial direction) is applied to the joint along with the axial pressure. This force from the radial direction can be generated by restraining the reinforcing bars from the radial direction using a cylindrical jig and applying axial pressure. In other words, when the jig is in a restrained state, the radially outward (that is, radial) stress generated by the axial pressure is restrained, so a force directed toward the center in the radial direction is generated as a reaction force, and this force acts on the joint. Therefore, when the axial pressure is increased to 5 to 6 Kgf/ ^mm2 , a correspondingly large force is applied from the radial direction, and these forces give the joint a forging effect and create a fine structure. obtained, and the toughness is improved.

In addition to increasing the radial force in relation to the axial pressure, when increasing only the radial force, it is also possible to apply pressure toward the radial center as an external force to the jig as described later.

In addition, in order to generate force from the radial direction as a reaction force as described above using a cylindrical jig, the length should be about 2 to 4 times the diameter of the reinforcing bar, etc., and the material should usually be 40 to 50 mm.
Constructed of Kgf/mm ^2nd grade steel. In addition, when using the cylindrical jig, install it in advance in a place where it will not interfere with the pressure welding work, and then install it in the final stage.
It is also possible to slide the cylindrical jig to a predetermined position and attach it to the reinforcing bar in step D'.

Further, the cylindrical jig 1 is usually configured as shown in FIGS. 3 and 4, and the inner surface 1a is configured as a smooth curved surface to prevent notches from occurring at the joint.
In particular, the inner diameter of the corresponding portion 1b of the joint portion is expanded to swell.

Therefore, when pressurizing with a high axial pressure in step D', the diameter of the joint expands as in the shape of the bulging part 1b, while the stress directed outward in the radial direction at that time increases in the bulging part 1b. A force directed toward the center in the radial direction as a reaction force due to restraint (opposite direction to the previous stress)
In other words, the joint is formed under the action of the axial pressure and this radial force.

Although the cylindrical jig 1 is not shown in FIGS. 3 and 4, it generally has at least two
Furthermore, these divided pieces are constructed so that they can be opened and closed freely with hinges, etc., so that eccentricity does not occur at the joint part.
It is preferable to provide a holding groove 2 on the inner surface, and to align and guide the vertical ribs of the reinforcing bar in this holding groove 2.

As described above, in the method of the present invention, metal atoms are first diffused by heating under high axial pressure, and then, in the final step, a joint is formed using a cylindrical jig with a partially expanded protrusion. In general, since pressure is applied not only in the axial direction but also in the direction orthogonal to the axis, the joint can have a large cross-sectional area, and the shape can be kept constant by being regulated by the shape of the cylindrical jig, increasing the strength of the joint. Not only does it notch, it also improves the toughness of the joint, making it possible to improve the joint's fatigue strength and mechanical strength at low temperatures, such as -100°C, to the same level as the base metal. can. That is,
A bulging portion is provided on a part of the inner wall surface of the cylindrical jig, the cylindrical jig restrains the jig, and in this state pressure is applied from the axial direction and the radial direction. Therefore, the diameter of the joint can be increased to increase its strength, and the structure of the joint can be made finer due to the forging effect, improving its toughness. At this time, when increasing only the force in the radial direction to enhance the forging effect, pressure is actively applied from the outside of the cylindrical jig using a hydraulic pump or the like.

Therefore, the preferred ranges of the implementation conditions for each step of the method of the present invention are as follows.

(1) In the A′ process, the axial pressure is 5 to 6 Kgf/mm ² per unit cross-sectional area, and the acetylene mixed gas is 18 to
20/min, oxygen 14-16/min, heating time 30 seconds-1
minutes.

(2) In the C' process, heating time is 30 seconds to 1 minute with a standard flame using a mixed gas of acetylene 14-16/min and oxygen 14-16/min, and the width heating range is the diameter of the reinforcing bar, etc.
The range is 1.0 to 1.5 times.

(3) In step D', a plurality of divided cylindrical jigs shown in FIGS. 3 and 4 are applied to the pressure-welded portion, and pressure is applied for 10 to 30 seconds. In this case, the cylindrical jig is provided with a protrusion in the large-diameter joint forming part, and the inside of the jig is smoothed to prevent notches, and then an auxiliary force source is used to form the cylindrical jig. The structure is such that the joint can be forged by applying pressure from the outside of the shaped jig. When using this auxiliary pressure source, it is preferable to pressurize the pressurized material such as reinforcing steel with the main pressurization device, then reduce the pressure, and then repressurize it with the auxiliary pressure source so that the desired shape can be obtained. .

In addition to reinforcing steel, the method of the present invention can be applied to any of these pressure welding materials. For example, when combined with an inner club that clamps the inner surface of steel pipes, it is possible to join steel pipes for various pipelines on-site. It can also be applied to on-site joints.

As explained in detail above, in the method of the present invention, first, heating is performed with a reducing flame while applying high axial pressure, so that metal atoms diffuse sufficiently between the end faces to form a pressure bond, and then, after baking, Finally, the joint of the press-welded material is covered with a cylindrical jig, and the joint is formed by applying axial pressure and force from a direction perpendicular to the axial direction, so the shape of the large-diameter joint remains constant and the notch etc. will not occur. Furthermore, a forging effect is imparted to the joint, the structure becomes finer, and toughness and mechanical properties at low temperatures can be improved.

[Brief explanation of the drawing]

Fig. 1 is a process diagram for gas pressure welding using a conventional method, Fig. 2 is a process diagram for gas pressure welding using an example of the method of the present invention, and Figs. 3 and 4 are diagrams of a cylindrical jig. FIG. 3 is a longitudinal cross-sectional view and a cross-sectional view of an example. Code 1...Cylindrical jig, 1a...Inner surface, 1b...
...bulge, 2...posture holding groove.

Claims (1)

[Claims] 1. The end surfaces of a pair of press-welded materials such as reinforcing bars are butted together, heated with a reducing flame while applying axial pressure, and pressed together, and then this press-welded part is heated with a standard flame to form a large-diameter joint, When pressure welding materials are gas pressure welded, first apply 5 to 6 kgf/mm ² to the butted end surfaces.
After applying axial pressure of , by applying an axial pressure of 5 to 6 Kgf/mm ² to the pressure welding part in this state,
A joining method using gas pressure welding for reinforcing bars, etc., characterized by forming a large-diameter joint with a finer structure by forging under the conditions of applying axial pressure and a force perpendicular to the axial direction.