JPH0446674B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a resistance welding method for welding intersections of reinforcing bars, particularly cross-overlapping sections thereof. [Prior Art] When constructing a reinforced concrete structure, conventional reinforcement work involves arranging reinforcing bars one by one and then binding and fixing their intersections with wire or wire. This type of reinforcing work is hard labor and extremely inefficient, and is considered the most unexplored field in the construction industry. Therefore, there is a strong need to shorten the construction period and save labor. One possible way to achieve this is to manufacture prefabricated reinforced steel structures in the form of a mesh or lattice of a certain size on the factory side. However, the conventional method of tying the reinforcing steel prefabricated structures using wires, etc. is extremely dangerous as there is a high risk that the prefabricated structures will collapse when the prefabricated structures are transported by crane. Therefore, it is necessary to fix the intersection using a method that guarantees a predetermined strength.
Manual welding takes a lot of time and is not efficient. Therefore, a method has been adopted in which a resistance welding device is used to apply pressure to the intersection, and then a current is passed between both reinforcing bars to heat the intersection, thereby deforming the intersection under pressure and joining the reinforcing bars. However, the surface of the reinforcing steel is covered with so-called black scale (iron oxide), or is not clean due to rust, dirt, oil, etc., and if it is joined in that state, black scale and other substances may form in the joint. There was a problem in that it contained impurities, which significantly reduced the bonding strength. Therefore, it is not preferable to remove the black scale with a grinder or the like in order to obtain joint strength, since this not only damages the ribs and knots of the deformed reinforcing bars but also reduces the strength of the base material. Therefore, if a certain level of joint strength is required, round steel of 12 mm or less is used for the wire (JISG3551...1980). However, the use of deformed reinforcing bars for wire rods is only recent.
Due to the above-mentioned reasons, there is no high-strength bonding strength. [Problems to be Solved by the Invention] The present invention solves the above-mentioned conventional problems, and it is possible to arbitrarily obtain the joining strength of reinforcing bar intersections, and to do so with high quality and high efficiency. The purpose is to obtain a resistance welding method that allows [Means for Solving the Problems] The method of resistance welding reinforcing bars according to the present invention involves applying current between the upper and lower reinforcing bars arranged in a cross-like manner while bringing them into pressure contact. In the method of joining by heating and deforming parts, before final pressurization or pressure welding, one of the reinforcing bars is slowly brought closer to each other while both reinforcing bars are energized, or pressurization and separation are repeated. This creates a flash between both reinforcing bars and cleans the joint surface. [Function] The method of resistance welding reinforcing bars according to the present invention generates flash between both reinforcing bars before they are finally joined by pressurization or pressure welding, so that black scale etc. on the joint surface of the intersection of reinforcing bars is prevented. The flash melts and scatters, thereby cleaning the joint surfaces. When the bonding surfaces are clean, pressure bonding is performed. In addition, since the flashing operation in this case is performed only for the purpose of removing black scale etc. from the joint surface, there will be no abnormal ridges or cross-sectional defects at the joint, as seen in Figure 9. From the shape of the cross-section of the joint, it has been confirmed that the state of fusion between the upper and lower reinforcing bars is extremely good. [Examples] Hereinafter, some examples of the method of the present invention will be described in detail. Figure 1 is a plan view of the reinforced prefabricated structure;
The figure is a sectional view of one of the reinforcing bar intersections A. This reinforcing prefabricated structure 10 is constructed by simply temporarily assembling upper reinforcing bars 1 and lower reinforcing bars 2 in a lattice shape in advance to a predetermined size, and applying the method of the present invention to the intersections of both reinforcing bars 1 and 2 to complete the structure. It is to be joined to. First, when applying the method of the present invention, the upper reinforcing bar 1 and the lower reinforcing bar 2 are clamped with corresponding power supply blocks 11, 12 and clamp arms 13, 14, respectively, as schematically shown in FIG. Each of the clamp arms 13 and 14 is pivotally connected to a welding device main body (not shown) so as to be pivoted to the lower side of the upper reinforcing bar 1 and the lower reinforcing bar 2 by a cylinder device (not shown) during clamping. In addition, the clamp arm 14 on the lower reinforcing bar side
is designed to lift the clamped lower reinforcing bar 2 toward the upper reinforcing bar 1 side by a cylinder device (not shown) that is separate from the above, and thereby, the lower reinforcing bar 2 is lifted against the upper reinforcing bar 1 at the intersection A. Can be strongly pressed. Next, after both reinforcing bars 1 and 2 were clamped as described above, welding tests were conducted on the four examples according to the process order shown in Table 1. Note that the case of the conventional method described above is added for reference.

[Table] However, the sample material used was JISG3112 SD35-D29 (nominal diameter (d) 28.6 mm). The welding conditions for each process are shown in Table 2.

[Table] As shown. Embodiment 1 is shown in FIGS. 3 to 6.
The welding conditions in Table 2 corresponding to items 4 to 4 are shown in a monitor diagram. Note that FIG. 7 is a monitor diagram of welding conditions in the conventional method. Furthermore, the operations in each embodiment are as follows. Example 1 In this example, first, with a welding voltage applied between both reinforcing bars 1 and 2, lower reinforcing bar 2 is gently lifted up and brought closer to upper reinforcing bar 1, and a flash occurs between both reinforcing bars 1 and 2. The black scale on the contact surface is melted and removed.
After cleaning the joint surfaces, they were pressed and heated in the same manner as in the conventional method to perform pressure welding. Example 2 First, both reinforcing bars 1 and 2 are pressurized and heated, then the lower reinforcing bar 2 is once separated from the upper reinforcing bar 1, and the lower reinforcing bar 2 is gently brought closer to the upper reinforcing bar 1 again as in Example 1. As a result, flash occurs between both reinforcing bars 1 and 2. This flashing melts and removes black scales and the like on the contact surfaces, thereby cleaning the joint surfaces. After that, both reinforcing bars 1,
2 were welded together by pressure welding. Example 3 After applying pressure to the lower reinforcing bar 2 to the upper reinforcing bar 1 while applying welding voltage between both reinforcing bars 1 and 2, and then repeating the operation of separating the lower reinforcing bar 2 from the upper reinforcing bar 1 several times, both reinforcing bars 1 and 2 were joined by pressure contact. In this case, when the lower reinforcing bar 2 is pressed against the upper reinforcing bar 1, electricity is applied between both reinforcing bars 1 and 2, and the joint portion is heated. Further, when the lower reinforcing bar 2 is separated from the upper reinforcing bar 1, flashing occurs, and black scales on the joint surface are melted and scattered. By repeating the above operations, the joint surfaces are cleaned. Example 4 After performing the pressurization and separation in Example 3, the lower reinforcing bar 2 is gently brought closer to the upper reinforcing bar 1 to generate flash between both reinforcing bars 1 and 2, and to clean the joint surface.
Thereafter, both reinforcing bars 1 and 2 were pressed together and joined. Regarding the joint strength of reinforcing bar intersections according to each of the above examples, excellent results were obtained in terms of shear strength as shown in Table 3.

〔Effect of the invention〕

As described above, according to the present invention, by generating flash between both reinforcing bars before they are finally joined by applying pressure or pressure welding, black scale etc. on the joint surface of the intersection of reinforcing bars can be removed by flashing. Blow it away,
Since the joint surfaces are cleaned and then joined, the joining strength is significantly improved, and the ribs and knots of the deformed reinforcing bars are not damaged, making it possible to efficiently obtain highly reliable joints.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a reinforced prefabricated structure to which the method of the present invention is applied, Fig. 2 is a sectional view of one reinforcing bar intersection A, and Figs. Table 2 is a monitor diagram of welding conditions, Figure 7 is a monitor diagram of welding conditions in the conventional method, Figure 8 is an explanatory diagram of the shear test method for evaluating the strength of the joint, and Figure 9 is a schematic diagram of the joint. FIG. 1...Top reinforcing bar, 2...Bottom reinforcing bar.

Claims (1)

[Scope of Claims] 1. In a method in which upper reinforcing bars and lower reinforcing bars arranged in an intersecting manner are brought into pressure contact with each other, current is applied between both reinforcing bars, and the intersections of the reinforcing bars are heated and deformed to join them. Before applying pressure or pressure welding, connect the reinforcing bars once.
A method for resistance welding reinforcing bars, which is characterized by causing flashing by lightly touching both reinforcing bars after they have been separated. 2. With the upper reinforcing bars and the lower reinforcing bars arranged in a cross shape being pressed together, electricity is applied between both reinforcing bars to heat and deform the intersection of the reinforcing bars, and then both the reinforcing bars are slowly pulled apart,
A resistance welding method for reinforcing bars, which involves repeating this process several times, which causes flashing, and then finally performing pressure welding. 3. A method of resistance welding reinforcing bars according to claim 2, characterized in that flashing is caused by lightly contacting both reinforcing bars before final pressure welding.