JPS5961576A - Resistance welding of pipe - Google Patents

Abstract

PURPOSE:To weld a pipe end cut at right angles to a bent or curved face by connecting - electrode of a DC resistance welding machine to the cut end of a pipe and connecting + electrode to the pipe body or plate face and pressure welding by applying current. CONSTITUTION:The small diameter side of a pipe 2, an object to be welded, is clamped in vertical position by the lower electrode of a rectification type DC resistance welding machine, and the body of large diameter side of the pipe 1 is placed on its upper end in horizontal position, and welded by conducting while pressing down the pipe body by an upper elecrode 3. The pipe 1 is connected to + electrode, and pipe 2 is connected to - electrode, and welding current smaller than the case of AC power source is applied. Then, the contact end of the pipe 2 is softened without scattering and a small weld zone is formed, and the circular welded area expands to left and right with descent of the upper electrode 3, and almost whole periphery is welded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pipe resistance welding method, which reliably welds the cut end of a pipe cut at a right angle to a mating pipe body or bent plate.

Resistance welding includes spot welding, seam welding, projection welding, heart welding, flash welding, and percussion welding. No matter which welding method is used, there is no way to reliably weld the entire length of the cut end of the pipe to the pipe heir or bent plate on the other side. If that was necessary, arc welding was the only option.

Spot welding and seam welding have different purposes because they are lap welds.

In projection welding, the welding surface and flow concentrate on the first protrusion (projection) that comes into contact, and welding occurs only there, so only a portion of the 1M pipe can be welded. Butt welding involves attaching the ends of the rod, extruding the outer skin to the outer periphery, and attaching the high-temperature part of the core, so it would be fine to weld the ends of the pipe together, but welding the ends of the pipe and the pipe body was unthinkable. .

Flash welding can also be used for butt welding pipe ends, but it cannot be used for welding pipe ends to plate surfaces.

Percussion welding involves instantly melting and crimping small protrusions, and cannot be used to weld the entire circumference of pipe ends.

The above is the common sense opinion of welding engineers.

The present invention has finally achieved its purpose after about several years of research and experimentation to solve the above-mentioned difficult problem. At the same time, what is the heat generation phenomenon in DC resistance welding? We discovered the important fact that there is a large difference between the polarities (+) and (-). The heating cuff of the arc in arc welding5 (tIIN) has been known for a long time.However, it was surprising that resistance welding, which does not generate an arc, had such a polarity effect. Conventionally, power sources for resistance welding have only used DC illumination sources for energy saving and spot welding of light alloys, and have mostly been AC 1! sources, so this phenomenon has not been understood. .

First, to explain the main points of this invention, place the cut end of the pipe cut perpendicularly to the y-axis against the pipe body or plate surface of the other party, and place the (-) electrode of the DC resistance welding machine on the cut end side of the pipe. (+
) This is a resistance welding method for pipes, which is characterized in that an electrode is connected to the pipe body or the plate side, and the two are crimped while flowing a welding current.

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1.2 shows the welding object, the small-diameter pipe, being clamped in a vertical position by the lower electrode of a rectifying DC resistance welding machine, and the large-diameter pipe being placed on the upper end in a horizontal position. Top 1! An example is shown in which the welding current is applied while the electrode 3 is being pressed down.

3 is a fixed t% and a flexible electrode that grips the vipco,
7 is a working fluid pressure cylinder for the movable electrode, 6 is a fluid pressure cylinder for driving the upper electrode 3, and S is a transformer with a rectifying element in place of a conventional AC power transformer.

Figures 3 to 6 show the welded pipes 1 and 1 of Figure 1.2 taken out and their states before and after welding.

As shown in Figures 3 and 4, when the cut end of the pipe is applied to the body of the pipe and welding current is applied, the current flows concentrated at the two points that are in contact from the beginning, creating a small weld. The vibrator/body 1 has a large heat capacity, and the tip of the pie goo has a small heat capacity in comparison. In order to weld materials with such differences in heat capacity, conventional methods have been used, such as a capacitor storage type, power source, or AC power source, in which a large current is applied instantaneously to reach the welding temperature on the high heat capacity side of the source, and crimping is performed at the same time. It is being

However, when welding one end of a pipe that has been cut at right angles as shown in Figure 3.4, the initial contact part will scatter due to the application of a large instantaneous current, making it impossible to obtain a good weld. In some cases, resistance welding has been performed by crushing the end face and processing it into a shape that fits the nine-piece barrel, but even then, this is limited to the combination of pipes with relatively thick walls and small outer diameters.

According to this invention, the pipe 1 is connected to the (+) terminal, and the pipe is connected to the (-) terminal, so that a smaller welding current is passed than in the case of an AC power supply. Then, the contact end of the pie goo softens without scattering, and at first a small welded area as shown in Fig. 4, 9 is formed, and as the upper electrode 3 descends, the arc-shaped welded area expands to the left and right, and as shown in Fig. 6. Therefore, it is possible to weld completely solid materials.

Note that if the pipe is sufficiently woody, it will be completely welded all around, but the smaller the difference in diameter, the larger the unwelded part IO in Figure 6 will remain (it cannot be seen from the outside). Although cracking is unavoidable due to the shape of the welded product, it is not an improvement at all in terms of strength.

For a strength test, when the pipe L side is fixed and the pipe λ side is pushed down, not the welded part but the adjacent pipe base material breaks.

Next, the experimental data of the present invention and the W1 case obtained by welding the same welded object using a conventional AC resistance welding machine are shown.

(I)〈Welded object Material Outer diameter Thick walled pipe/STKM 22.1m O.9 pipe, Z 12.7 0.9 Welding conditions〉 Pressure welding current Welding time 350ky
18000A 11 Hz test results〉Tensile strength
The broken tube weighed 1900 kg and the base material did not weld at all with AC power supply.

(■) <Welded object> Material Outer diameter Thick walled tube/STKM 2 B, 61nll
j, 27111 Pipeco # 22.2
1.2 Welding conditions> Pressure force Welding current Current application time Invention 450 kg 22000 A 11 Hz AC WL source 450 kl 26500 A 1
5 Hz test results> Tensile strength Breaking tube location Invention 2500ky Base metal AC power supply 700 Welded part (■) <Welded product> Material Outer diameter Thick pipe/STKM 34mm 2.3mm
Pipe, 2 21.7 1.9 Welding conditions> Pressure welding current Current application time Invention
1500kg27000A 15Hz AC power supply
1500 54000 1M〈Test results〉
Tensile strength Break point: Invention 3500kg
Base metal AC lightning source 1 source 2500 ky Welding part Compared to the above embodiment in which the pipe end is welded to the pipe body, according to the present invention, it is easier to weld the pipe end to the flat plate surface. The next experimental data is the welding of the pipe and flat plate shown in Figure 7.

(■) Welded product> Material Outer diameter Thickness flat plate/a 5PCC1゜2mm Vipco STKM 25.4*am 1.2〈
Welding conditions〉 Pressure force Welding current Current application time 50
0 kg 500[]OA 13 Hz〈
Test results〉 Tensile strength: 2000 kg at fracture tube Base material: With AC power source, welding is not possible unless a projection is made on the flat plate la side.

The next experimental data is the welding of the square pipe/h and the round pipe in Fig. 8. In addition, all of the following experiments cannot be welded using an AC power source.

(■) <Welded object Material Outer diameter Thick square pipe/b 5TKR21mm (square) 16 dragon pipe If 19 1.6 <Welding conditions>
Pressure force Welding part, flow Current application time 5 [[kg240[
] OA 6 Hz <Test results> Tensile strength Breaking tube 2400ky Base material The following experimental data is the welding of the square vibrator/b and the cover plate 10 in FIG.

(■) Welded item〉 Material Dimensions Thickness square A (Eve/b 5TKR20X20+n+++
1.2mrA cover plate 10 5PCC20X30
1.2 Welding conditions〉 Pressure force Welding current Current conduction time 450ky21000A 6Hz Test results〉 Tensile strength Water pressure test 320ky
No abnormality at 5ky/cr/l The next experimental data is the 10th
The vibrator/C shown in the figure and the cover plate 10 are welded together.

(■) Welded object> Material Outer diameter Inner thickness Vibe/c STKM 2B, 4 dragons 12 cap plate/θ 5PCC2B 1.6 <Welding conditions> Pressure force Welding current Current conduction time 400 kp
20000A 6 Hz (Test results) Tensile strength Water pressure test 450 kg 5 ky/d No abnormality The next experimental data is the T-shaped welding of square pipes/b in Fig. 11.

Welded parts〉 Material Dimensions Thick walled square pipe/d 5TKR21X21? III+ 1.
6mm square pipe/g 5TKR19X19 1,6
1. Welding conditions> Pressure force Welding current Current application time 60
0kg 2500OA, 7Hz <Test results> Tensile strength Breaking tube 1500ky Base material In this way, welding objects that cannot be welded at all with conventional AC power welding machines can be resistance welded with perfect strength. Jin's invention uses DC as the power source, with the end of the pipe being (-) and the other end being (+)! If we consider the reasons why we were able to achieve such excellent results simply by connecting to the poles, we can think of the following points.

(α) With an AC power source, the current value periodically drops to zero and there is a cooling period during which heat is generated, but with a DC power source, the current value never drops to zero, so the welded part generates continuous heat.

(h) 1t due to the pinch effect of DC current ($ flux)
Since the first stream tends to concentrate at one point, localized heating is achieved, and the heat generation effect is excellent.

<c> When energizing, a transient current (2 to 3 times the steady current) flows with AC t'fI, but with a DC power supply, excessive current does not occur, and the contact resistance of the welded butt works, so that the current decreases. is automatically low at first and gradually increases, thereby preventing initial dust (scattering of molten metal) and self-controlling the necessary welding wrinkle flow.

(d) Use of differences in heat generation due to polarity of DC power supply.

The above may work synergistically to make perfect resistance welding possible over a wide range of welding targets with greatly different heat capacities, such as T-welds at the ends of pipes, as in the above example.

Similarly, even if a direct current power source is used, if the electrode connection method of the present invention is reversed, that is, the pipe end side is connected to (+) and the other side is connected to (-), the effects of this invention cannot be obtained at all.

Note that the embodiments of the invention are not limited to the illustrated example, but can be applied to any case where the cut ends of round pipes and various square pipes are welded to a vibrator body, flat plate, bent plate, curved plate, etc. such as T-shaped welding. Applicable to Welded objects are not limited to steel. A rectifier type DC power source is usually used, but it is not limited to this.

This invention achieved a revolutionary result in resistance welding technology in that even the end of a thin pipe with a wall thickness of less than 1 inch can be resistance welded all around to other pipe bodies and plate surfaces. In addition, in resistance welding, we demonstrated that it is possible to use the polarity effect to balance the heat generation of both welding materials, which have different heat capacities, just like the polarity effect in arc welding, and we found a way to greatly expand the applications of resistance welding by using a DC power source. I opened it.

Using the DC power supply and polarity effect, the end of a pipe cut at right angles can be welded not only on flat surfaces, but also on curved and bent surfaces. It is. Moreover, stable and high quality welds can be obtained. And the current value used is AC 1! 20% compared to the source
The energy saving effect is also significant.

[Brief explanation of drawings]

Figure 1.2 is a front and side view showing one embodiment of the present invention, and Figure 5.4 is an elevational view showing the relative positions of both pipes, which are the welded objects in Figure 1.2, at the start of welding. Plan view, Section 5.6
The figures are also an elevation view and a plan view when welding is completed, and Figures 7 to 11 are perspective views of welded products of various shapes to which the present invention is applied. L... Torso side vibe, K... Cut end side vibe, 3...
・(→electrode, da, 3...(→electrode. Patent applicant Nippon Welding Co., Ltd. Decoy Agent Patent attorney Fuku 1) Nitō ′-Hitofu・ Same agent Patent attorney Fuku 1) Kenzo X4,
-7ノ

Claims (1)

[Claims] Place the cut end of the pipe cut perpendicular to the axis on the pipe body or plate surface of the other party, and place the (-) electrode of the DC resistance welding machine on the cut end side of the pipe, (→Place the electrode on the curved side of the pipe body or plate side) A resistance welding method for pipes, which is characterized by connecting them and making them legitimate while flowing welding current.