JPS62144878A - Magnetic agitation welding method for tube panel - Google Patents

Abstract

PURPOSE:To uniformly weld both faces of the deformed material of a tube and fin, etc. and to obtain a good back bead by generating an alternating magnetic field by passing the alternating current in the limited frequency by fitting a magnetized coil to a welding torch and by welding a molten metal with performing its magnetic agitation. CONSTITUTION:An alternating magnetic field is generated on the weld zone when 0.5-20Hz alternating current is passed to a magnetized coil 13 from an alternating current rectangular wave power source 17. Then, a molten metal 14 is produced when DC welding current is passed with feeding a welding electrode 12 overthere. Lorentz's force is then caused between the welding current passing inside the molten metal 14 and alternating magnetic field, the molten metal 14 is smoothly melted and solidified with molten metal 14 being stirred and a good penetration shape is obtd. Also, the arc force and heat concentration in the vertical direction are relaxed by the agitation and the burning breakdown onto a water cooling copper strap 4 is prevented as well. The similar effect is obtainable by fitting a magnetized coil 13 to the water cooling copper strap 4 as well.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Ti magnetic stir welding method for tube panels;
This is particularly relevant to the production of tube panels for power generation and other boilers.

[Conventional technology]

Conventionally, as a tube panel for a boiler, one shown in FIG. 5, for example, is known. 1 in the figure is a large number of long tubes. A large number of long fins 2 are arranged between these tubes 71, and the tubes 1 and fins 2 are connected by weld beads 3. Hereinafter, a method of welding the tube 1 and the fin 2 will be explained.

Conventional method 1 See FIG. 6. The figure shows a part of the cross section of the tube panel. However, 3a, 3b, 3C13 in the figure
d shows weld beads at different locations. That is, in conventional method 1, after first forming weld beads 3a and 3b in sequence, the tube 1 and fin 2 are reversed, and then weld bead 3C13 is formed.
In this method, welding is completed by forming d.

Conventional method 2 Refer to FIG. 7. However, in the figure, 4 indicates a water-cooled copper dowel, 5 indicates a cooling water inlet, and 6 indicates a cooling water outlet. That is, conventional method 2 is a method in which the burn-through of molten metal arc-welded from above is caught by the water-cooled copper dowel 4, and at the same time, the tube 1 and the b-fin 2 are joined while forming the Uranami bead shape. .

Conventional method 3 Refer to FIG. That is, conventional method 3 is a method in which a fixed backing material 7 is installed over the entire length of the weld line. In addition, as a material for the backing material 7, copper dowel, flux backing for backing, etc. are used.

[Problem that the invention seeks to solve]

However, the conventional technology has the following problems.

(1) In the case of conventional method 1, weld beads 3a to 3d are formed in many locations. Further, since the tube 1 and the fins 2 must be reversed, work efficiency is reduced.

(2) In the case of conventional method 2, welding man-hours are reduced compared to conventional method 1. However, the back wave of the weld bead is influenced by the water-cooled copper weld 4, and the arc force causes the water-cooled copper weld 4 to
Since the damage is severe, it is not possible to obtain a good Uranami bead.

In addition, due to fluctuations in the aiming position of the welding electrode, tube 1
However, there are drawbacks such as excessive accumulation and a tendency to cause insufficient accumulation.

(3) In the case of Conventional Method 3, the copper backing material used for single-sided welding is severely damaged due to the arc force. In addition, other backing materials are expensive.

The present invention has been made in view of the above circumstances, and is a method for magnetic stirring welding of tube panels, which can avoid excessive or insufficient penetration of the tube and damage to the backing material and obtain a good uranami bead. The purpose is to provide

[Means for Solving the Problems] The present invention involves attaching a magnetizing coil to a welding torch or backing material, passing an alternating current of 0.5 to 20 Hz through the magnetizing coil to generate an alternating magnetic field, and melting. By welding the metal while magnetically stirring, it is possible to form a good uranami bead.

[Effect]

According to the present invention, by magnetically stirring the molten metal, it is possible to evenly melt both sides of the profiled material (different heat capacities), thereby achieving uniform and good penetration and a Uranami bead. In addition, a good Uranami bead can also be obtained by preventing damage to the backing material (copper pad) due to arc concentration.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 Please refer to FIG. The figure shows one implementation situation using submerged arc welding. Here, the same members as those in the prior art are given the same reference numerals and the description thereof will be omitted.

11 in the figure is a welding nozzle that feeds the welding nozzle 12 from the inside to the welding location. A magnetizing coil 13 is provided at the tip of this welding nozzle 12 . This magnetizing coil 13 causes the molten metal 14 between the tube 1 and the fin 2 to
is magnetically stir welded. A welding power source 16 is electrically connected to the welding nozzle 11 via a welding electric wire 15.

Note that the tube 1 and the welding power source 16 are also electrically connected by a welding wire 15. The magnetizing coil 13 is connected to an AC rectangular wave power source! 17 are electrically connected.

Next, the principle of magnetic stir welding will be described using FIG. 1.

First, when a rectangular wave current flows through the magnetizing coil 13 from the AC rectangular wave power source 17, an alternating magnetic field is generated at the welded portion of the lower part of the magnetizing coil 13. Here, when a DC welding current is applied thereto while feeding 7 the welding electrode 12, molten metal 14 is formed. Then, a Lorentz force is generated between the welding current flowing radially within the molten metal 14 and the alternating magnetic field, and the molten metal 1
5 is stirred. Therefore, the surface of the tube 1 and the end surface of the fin 2 of the material to be welded are smoothly melted and solidified by the stirred molten metal 14, and a good welded shape is obtained. Also,
Since the arc force and heat concentration in the vertical direction are layered by stirring, seizure damage to the water-cooled copper pad 4 is also prevented.

Therefore, according to the first embodiment, by reducing excessive accumulation and insufficient accumulation in the tube 1, and preventing loss due to arc force and heat concentration of the water-cooled copper butt (backing material) 4, good back wave can be achieved. A bead can be obtained.Also, high efficiency welding is possible by single-sided welding.Furthermore, unlike conventional method 1, there is no need to reverse the tube or fin, so workability is good.

In fact, when the magnetic stirring effect was investigated, the results shown in FIGS. 9 to 14 were obtained.

FIG. 9 is a characteristic diagram showing the relationship between magnetic field strength and magnetic field frequency (AC rectangular wave). In the figure, the O mark indicates a case where the bead shape is flattened, and the X mark indicates a case where the same effect does not exist. However, the welding conditions were: welding method: latent arc welding (heat-on-plate), welding current: 2650 A, welding voltage: 32 V, and welding speed: 300 tm/min.

Figures 10 and 11 show microscopic photographs of the metal structure of a cross section of a weld bead, respectively. Figure 10 shows the case without magnetic stirring, and Figure 11 shows the case with magnetic stirring (300 Gauss, 5 Hz). It is. It is clear from FIG. 11 that when magnetic stirring is present, the weld bead becomes shallowly depressed. Therefore, it can be seen that the damage caused by seizure to the water-cooled copper dowel is reduced, and that a good Uranami bead can be obtained because the molten metal is solidified while being stirred.

12 to 14 each show a microscopic photograph of the metal structure of a cross section of a welded portion of a tube panel. Specifically, the first
Figures 2 and 13 are the conventional method (11 ki)! (if there is no stirring)
, and FIG. 14 shows the case where there is magnetic stirring according to the method of the present invention (magnetic field strength: 150 Gauss, 5 Hz). From these figures, it was confirmed that in the conventional case, Uranami failure (as shown in Figure 12) and failure due to excessive accumulation in the tube (as shown in Figure 13) were confirmed.
In the case of the present invention, penetration was good and the underwave bead was also good (as shown in Figure 14).

Example 2 Please refer to FIGS. 2 to 4. Here, FIG. 2 shows the welding method shown in FIG. 1 in which the magnetizing coil 13 is integrated with the opposite side of the welding nozzle 11, that is, with the water-cooled copper dowel 4. 3 is a partially enlarged view of FIG. 2, and FIG. 4 is a side view of FIG. 3.

21 in the figure is an electromagnetic pole. Note that the principle and effects of magnetic stir welding are the same as in Example 1.

〔Effect of the invention〕

As detailed above, according to the present invention, there is provided a highly reliable magnetic stirring welding method for tube panels that can form a good uranami bead while avoiding excessive or insufficient penetration of the tube and damage to the backing material. can be provided.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the magnetic stirring welding method for tube panels according to Example 1 of the present invention, FIG. 2 is an explanatory diagram of the magnetic stirring welding method for tube panels according to Example 2 of the present invention, and FIG. Figure 2 is a partially enlarged view, Figure 4 is a side view of Figure 3, Figure 5 is a side view of Figure 3, and Figure 5 is a side view of Figure 3.
The figure is a perspective view of a tube panel for a boiler, Figures 6 to 8 are cross-sectional views showing conventional welding methods, and Figure 9 is a characteristic diagram showing the relationship between magnetic field strength and magnetic field frequency according to the method of the present invention. , Fig. 10 is a microscopic photograph of the metal structure of a cross section of a weld bead without magnetic stirring, Fig. 11 is a microscopic photograph of a metal structure of a cross section of a weld bead with magnetic stirring, Figs. Figure 13 is a microscopic photograph of the metallographic structure of a cross section of a panel tube welded area when there is no magnetic stirring by the conventional method, and Figure 14 is a metallographic structure of a cross section of a panel tube welded area when there is magnetic stirring by the method of the present invention. FIG. DESCRIPTION OF SYMBOLS 1...Tube, 2...Fin, 4...Water-cooled copper dowel, 5...Cooling water inlet, 6...Cooling water outlet, 11...
... Welding nozzle, 12... Welding electrode, 13... Magnetizing coil, 14... Molten metal, 16 Welding power source, 17...
- AC square wave generation power supply, 21...electromagnetic pole. Applicant Sub-Agent Patent Attorney Takehiko Suzue No. 5 Figure 6 Country No. 7 r figure,'? To 11f high Iza 171- Koni = 1g Ko,

Claims (1)

[Claims] In the magnetic stirring welding method for tube panels used in boilers, etc., which welds together irregularly shaped materials such as tubes and fins, a magnetizing coil is attached to the welding torch or backing material, and this magnetizing coil is heated at an alternating frequency of 0.5 to 20 Hz. A magnetic stirring welding method for tube panels, which is characterized in that a current is passed to generate an alternating magnetic field, and molten metal is welded while being magnetically stirred.