JP2007319887A - Resistance welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resistance welding method for preventing a work to be welded from being in a hardened state in the resistance welding in which tempering can not be performed. <P>SOLUTION: Before performing the permanent welding, workpieces (an upper bar steel 1 and a lower bar steel 2) are heated to the predetermined temperature in advance using remaining heat, and the calorie of the entire workpieces (the upper bar steel 1 and the lower bar steel 2) is increased and hardly cooled to be a welding method with less "hardened state". In a case of bar steels of different diameters (a bar steel to be easily heated and cooled, and a bar steel to be hardly heated and cooled), the temperatures of both bar steels are substantially identical by the remaining heat (to be uniformly soaked), and the welding of high strength can be performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

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.

(Invention of Claim 1)
The welding method of the present invention is characterized in that, in resistance welding, a welding object is heated before performing main welding.

(Invention of Claim 2)
The welding method of the present invention relates to the invention described in claim 1 above, and heating to the object before performing the main welding uses a current of 70% to 75% of the main welding, and is substantially equal to the time of the main welding. It is characterized by time.

(Invention of Claim 3)
The welding method according to the present invention relates to the invention described in claim 2 and 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.

(Invention of Claim 4)
The welding method of the present invention relates to any one of the first to third aspects of the present invention, and is characterized in that the diameters of the welding objects are different.

  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 steel bar 1 and the lower steel bar 2 is performed by using the upper tool 5 and the lower tool 6 as shown in FIG. 4 after sandwiching the steel bar between the upper electrode 3 and the lower electrode 4 as shown in FIG. Energize between the electrodes while applying pressure.

As shown in the graph of FIG. 5, the energization current performed between the electrodes is performed by performing pre-preheating A ₁ using current of 70% to 75% of main welding A ₂ , performing main welding, and then performing post 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 using 72% current of the main welding (with KA ratio of 72%) was applied to the object before the main welding was performed. 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 is 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 of the temperatures become approximately the same (pre-heated) due to the pre-heat, 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 (4)

In resistance welding, a welding method characterized by heating an object to be welded before performing main welding. 2. The welding method according to claim 1, wherein the heating of the object to be performed before the main welding is performed using a current of 70% to 75% of the main welding for a time substantially equal to the time of the main welding. 3. The welding method according to claim 2, wherein 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 according to claim 1, wherein the welding objects have different diameters.

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