JP4873137B2 - Resistance welding method - Google Patents

Description

  The present invention relates to resistance welding used for joining welding objects such as reinforcing bars, wire mesh, bar steel, and steel bars.

  In resistance welding, the temperature of the object to be welded rises and falls abruptly, so that the object becomes baked and the hardness of the object is improved, but the toughness deteriorates, so that the object becomes brittle. there were.

In order to solve this problem, a technique of performing “tempering” after welding (for example, Non-Patent Document 1) is disclosed.
Masanobu Hamasaki "Easy Resistance Welding" Published by Sangyo Publishing Co., Ltd. September 30, 2005, 20th edition, pages 84-85

  However, the above-mentioned “tempering” technique takes time because it is heated after welding, and there is a problem that the tempering process cannot be performed in spot welding performed in a short time.

  Also, when welding objects with different diameters, welding objects with small diameters have the characteristic that they are easy to heat and cool, and welding objects with large diameters have the characteristics that they are difficult to heat and difficult to cool. It has been difficult to weld a welding object like a welding object of the same diameter.

The welding method of the present invention is characterized in that, in resistance welding, a welding object is heated before performing main welding. The welding method of the present invention is characterized in that the heating to the object performed before the main welding is performed at a time approximately equal to the time of the main welding using a current of 70% to 75% of the main welding.

The welding method of the present invention is characterized in that after the main welding, post-heating is applied using a current of 70% to 75% of the main welding at regular time intervals. The welding method of the present invention is characterized in that the diameters of the welding objects are different.

(Invention of Claim 1)
The welding method of the present invention includes welding for performing pre-preheat (A1), pause until main welding (A2), main welding (A2), pause until post-welding (A3), and post-welding (A3). The preheat (A1) uses 70% to 75% current of the main welding (A2), and the post welding (A3) uses 70% to 75% of the main welding (A2). The current is used, the time for performing the pre-residual heat (A1) is Cy ₁ , the rest time until the main welding (A2) is Cy ₂ , the time for performing the main welding (A2) is Cy ₃ , and the time for the post-welding (A3) Cy ₁ = Cy ₂ = Cy ₃ = Cy ₄ = Cy _5, where Cy _{4 is} the rest time and Cy ₅ is the time for post welding (A3).

(Invention of Claim 2)
The welding method according to the present invention relates to the invention according to claim 1, characterized in that no quenching occurs by making the temperatures of the upper bar (1) and the lower bar (2) having different diameters the same .

  In the welding method of the present invention, the object to be welded is preliminarily heated. Therefore, even if only the main welding is performed, it is difficult for “burning” to enter the object, and it is possible to make the object less brittle.

  Moreover, even if it is a welding object having a different diameter, it enables welding having the same strength as the welding object having the same diameter.

  Hereinafter, examples will be described in detail as the best mode for carrying out the welding method of the present invention.

  FIG. 1 is an explanatory view showing a state before assembling the upper steel bar 1 and the lower steel bar 2, FIG. 2 is a perspective view in which the upper steel bar 1 and the lower steel bar 2 are crossed, and FIG. FIG. 4 is a front view when welding is performed, and FIG. 5 shows a relationship between current and time during welding.

[Preparation of steel bar]
First, as shown in FIG. 1, the upper steel bar 1 and the lower steel bar 2, which are objects to be welded, are crossed, and the upper welded part 10 of the upper steel bar 1 and the lower welded part 20 of the lower steel bar 2 are brought into contact with each other.

  As shown in FIG. 2, the contact of the steel bar is not only crossed in a cross but also a matter that can be appropriately performed by those skilled in the art.

[Welding method]
The welding of the upper bar 1 and the lower bar 2 is performed by using the upper tool 5 and the lower tool 6 as shown in FIG. 4 after sandwiching the bar between the upper electrode 3 and the lower electrode 4 as shown in FIG. Energize between the electrodes while applying pressure.

Energization current conducted between the electrodes, as shown in the graph of FIG. 5, before subjected to residual heat A ₁ using 70% to 75% of the current of the welding A _2, after the welding, the rear welding ( is performed tempering) the _{a 3} with 70-75% of the current of the welding.

The time for performing the pre-remaining heat A ₁ is Cy ₁ , the rest time until the main welding A ₂ is Cy ₂ , the time for performing the main welding A ₂ is Cy ₃ , the rest time until the rear welding A ₃ is Cy ₄ , and the rear welding A ₃ It is preferable to set Cy ₅ to be Cy ₅ and Cy ₁ ≈Cy ₂ ≈Cy ₃ ≈Cy ₄ ≈Cy ₅ .

[Effect of front residual heat]
Table 1 shows the test results of the pre-welding of the present invention.

  The test uses D10 (JIS) steel bar (steel bar with a diameter of 10 mm) and D13 (JIS) steel bar (steel bar with a diameter of 13 mm) as test specimens, and pressurizes at 5.9 KN. Cross welding was performed using a typical resistance welder (D welder φ25).

The units described in Table 1 are as shown below.
KA: (kiloamperes) current.
CY: (cycle) Frequency in West Japan = 60 Hz
15 CY = 15 cycles / 60 Hz = 0.25 seconds E: (Joule) energy. E = A ² × cy
KN: (Kilonewton) tensile strength.

表１に記載した通り、試験結果は、本溶接を行う前に行う対象物への加熱が、本溶接の７２％の電流を用いたもの（ＫＡ比を７２％としたもの）の引っ張り強度が３６．３ＫＮという最も大きい値を示した。

As shown in Table 1, the test results show that the tensile strength of the object to be heated before the main welding is performed using 72% of the current of the main welding (KA ratio is 72%). The largest value of 36.3 KN was shown.

  Assuming that 36.3KN is the maximum welding strength and 100%, as shown in Table 1, since the one with 70% KA ratio is 36.1KN, the strength ratio is 99% and KA ratio is 75%. Is 35.7 KN, so the intensity ratio is 98%.

  Since the strength ratio of the latter half of the 90% is preferable, the heating to the object performed before the main welding is preferably performed using the current of 70% to 75% of the main welding.

In this welding method, even if resistance welding (for example, spot welding) in which Cy ₃ (main welding time) is small and rapidly cooled by performing pre-preheating, the amount of heat of the entire bar (welding object) Therefore, the temperature of the welded portion (upper welded portion 10, lower welded portion 20) can be raised to a predetermined temperature in advance, and the welded object is difficult to cool, and “baked” is formed on the welded object. It becomes possible to weld without entering.

The heating to the object to be performed before the main welding using the current of 70% to 75% of the main welding is performed with a steel bar having a different diameter such as a D10 steel bar and a D13 steel bar (a D10 steel bar that is easy to heat and cool). In the case of a D13 steel rod that is difficult to heat and cool, both the temperatures become the same (pre-heated) due to the pre-stress, and high strength welding becomes possible.

  Further, as shown in FIG. 5, after the main welding under the same conditions as the pre-preheating after the main welding, after applying the post-heating and lowering the temperature, welding with less “quenched state” of the welding object becomes possible. .

  The welding object is not limited to a reinforcing bar, a wire mesh, a steel bar, and a steel bar, but may be any metal as long as it is a “quenched state” and can be appropriately performed by those skilled in the art.

It is explanatory drawing which shows the state before an assembly which shows the upper bar 1 and the lower bar 2. It is a perspective view which shows the state which made the upper bar 1 and the lower bar 2 cross. It is a perspective view which shows the state which pinched | interposed the crossed steel bar between the upper electrode 3 and the lower electrode 4. FIG. It is a front view which shows the state which welds. It is a graph which shows the electric current and time of a welding place.

Explanation of symbols

1 Upper Bar 10 Upper Weld 2 Lower Bar 20 Lower Weld 3 Upper Electrode 4 Lower Electrode 5 Upper Tool 6 Lower Tool

Claims (2)

Pre-preheat (A1), pause to main welding (A2), main welding (A2),
A welding method for performing a pause until post-welding (A3) and post-welding (A3),
The front residual heat (A1) uses 70% to 75% of the current of the main welding (A2),
Post-welding (A3) uses 70% to 75% of the current of main welding (A2),
The time for performing the pre-residual heat (A1) is Cy ₁ , the rest time until the main welding (A2) is Cy ₂ ,
The time for performing the main welding (A2) is Cy ₃ , the rest time until the post-welding (A3) is Cy ₄ ,
If the time for performing post-welding (A3) is Cy ₅ ,
Cy ₁ = Cy ₂ = Cy ₃ = Cy ₄ = Cy ₅ By making the temperature of both the upper steel bar (1) and the lower steel bar (2) with different diameters the same ,
The welding method according to claim 1, wherein no burning occurs.

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