JPH0453624B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a magnetic blow prevention arc welding method for preventing the magnetic blow phenomenon that occurs during arc welding of steel plates. [Prior Art] When performing arc welding of thin steel plates using a DC power source, a so-called magnetic blow phenomenon occurs in which the arc receives a magnetic force due to the magnetic field created by the welding current and is displaced in that direction. When arc welding is performed at the center of a steel plate with a large area, the welding current is widely distributed throughout the steel plate and converges at the arc generation point from all sides, so it is not as noticeable. However, when arc welding is performed at the edges of the steel plate, magnetic blowing The phenomenon is noticeable and the arc is displaced toward the center of the steel plate. As a result, the arc is disturbed at the ends of the steel plate, particularly at the end of the weld, resulting in incomplete welding and welding defects. In order to prevent such a magnetic blow phenomenon that causes welding defects, conventionally, a magnetic material or an electromagnetic coil was placed near the arc generating part of the electrode, as described in, for example, Japanese Patent Application Laid-open No. 47-27146. A method has been used to control the arc by arranging it and moving it in the same direction and at the same speed as the electrode, and varying the strength of the magnetic force acting on the arc. [Problems to be Solved by the Invention] However, in the above-mentioned conventional arc welding method in which a magnetic material or an electromagnetic coil is placed near the arc generating part of the electrode, the material, size, shape, etc. of the magnetic material may be changed depending on the welding conditions. In addition, it was necessary to change the size of the electromagnetic coil, the number of turns, the strength of the current, etc., which caused problems such as complicated control. [Means for Solving the Problems] The present invention aims to provide means for solving the above-mentioned conventional problems. In the arc welding method, a magnetic blow-preventing arc electrode is provided before and after an arc welding electrode, and at the welding start end, at least the above-mentioned arc welding electrode and the magnetic blow-preventing arc electrode provided in front of the electrode are connected in the same direction. magnetic blow prevention, characterized in that welding is carried out while applying current to the welding end, and at least the above-mentioned arc welding electrode and a magnetic blow prevention arc electrode provided behind the electrode are welded while being energized in the opposite direction. Related to arc welding method. The present invention will be explained below based on the drawings. FIG. 1 is an explanatory diagram showing the configuration of an example of the tip portion of a welding torch for carrying out the present invention. Arrow A
The direction is the welding direction, an arc welding electrode 22 is attached to the tip of the welding torch 1, and magnetic blow-prevention arc electrodes 21 and 23 are installed before and after the arc welding electrode 22 with the welding direction as a reference. It is provided. The arc welding electrode 22 is a consumable electrode that has an Ar gas flow path 3 around it, and has the role of welding steel plates together, which are the materials to be welded. selected. on the other hand,
The magnetic blow prevention arc electrodes 21 and 23 are also tungsten electrodes having an Ar gas flow path 3 around them.
The purpose is not to weld, but to control the magnetic field created by the welding current, and to heat the area in front of the welding direction to a temperature exceeding the magnetic transformation point of the steel, e.g. 760°C or higher, to make the steel plate non-magnetic and make it difficult for magnetic lines of force to pass through it. It is preferable to use tungsten or a tungsten alloy, which is not easily consumed. [Function] The arc welding method of the present invention using the welding torch configured as described above will be described below. FIG. 2 is an explanatory diagram showing how to use a welding torch at the welding start end of the steel plate 4. At the welding start end of the steel plate 4, the arc welding electrode 22 and the magnetic blow prevention arc electrode 21 are used as positive electrodes and welding current is passed in the same direction. This is the case. The solid arrow i represents the welding current, the broken arrow H represents the strength of the magnetic field generated by the welding current, and the white arrow f represents the force acting on the arc 5. As shown in the figure, when welding current is passed in the same direction through the arc welding electrode 22 and the magnetic blow prevention arc electrode 21, the arc 5 of the arc welding electrode 22 and the arc 5 of the magnetic blow prevention arc electrode 21 are An attractive force acts between them, resulting in a stable arc. In addition, the magnetic blow-preventing arc electrode 21 has the effect of making the steel plate 4 non-magnetic and making it difficult for the lines of magnetic force to pass through it by heating the front region in the welding direction to a temperature higher than the magnetic transformation temperature of the steel (hereinafter referred to as preheating effect). The influence of the magnetic field on the arc 5 is weakened. FIG. 3 is an explanatory diagram showing how to use the welding torch at the end of welding of the steel plate 4. At the end of welding of the steel plate 4, the arc welding electrode 22 and the magnetic blow prevention arc electrode 23 are used as positive and negative electrodes, respectively, and welding is performed in the opposite direction. This is the case when current is passed through. As in the case of FIG. 2, the solid arrow i represents the welding current, the broken arrow H represents the strength of the magnetic field generated by the welding current, and the white arrow f represents the force acting on the arc 5. As shown in FIG. 3, when welding current is passed in opposite directions through the arc welding electrode 22 and the magnetic blow prevention arc electrode 23, an arc 5 of the arc welding electrode 22 and an arc 5 of the magnetic blow prevention arc electrode 23 are generated. A mutually repulsive force acts between them, and the displacement of the arc toward the center of the steel plate, which conventionally occurs, is alleviated, and the arc 5 of the arc welding electrode 22 reaches the welding end of the steel plate 4. The magnetic blowing phenomenon is not so remarkable in areas other than the welding start end and welding end end mentioned above.
Although it is not necessary to energize the magnetic blow prevention arc electrode 21, in the case where the preheating effect of the magnetic blow prevention arc electrode 21 as explained in FIG. 2 is expected to completely prevent the occurrence of the magnetic blow phenomenon. may be energized. Note that the farther the magnetic blow prevention arc electrodes 21 and 23 are from the arc welding electrode 22, the weaker the magnetic blow prevention effect becomes. When the arcs of the arc electrodes 21 and 23 are brought closer to the arc of the arc welding electrode 22, the effect of preventing magnetic blowing becomes significant. The angle of inclination is preferably about 15 degrees with respect to the arc welding electrode 22 held vertically. [Example] The following will explain based on an example. Using the welding torch 1 shown in FIG.
Arc welding was performed using a steel plate of mm as a specimen.
The groove shape is I-shaped, the interval is 1.5mm, and the welding length is 300mm.
It is. Table 1 shows the chemical composition of the test materials, and Table 2 shows the welding conditions. In Table 2, pole No. 2 in the "Electrode" column is a consumable electrode that is an electrode for arc welding, and poles No. 1 and 3 are arc electrodes for magnetic blow prevention, and pole No. 1 is a consumable electrode. Pole No. 3 represents the tungsten electrode provided in front of the consumable electrode. Further, the symbol and before the electrode name indicate that the electrode is a negative electrode and a positive electrode, respectively. In addition, pole No. 1 of the tungsten electrode is 100 mm from the welding start end to the welding end end.
The current was applied from 100 mm before the end of welding to the end of welding for pole No. 3. Furthermore, the tungsten electrodes (Pole Nos. 1 and 3) were all tilted 15 degrees in the direction to bring the arc closer to the arc of the consumable electrode held vertically.

【table】

〔Effect of the invention〕

As explained above, when performing arc welding from one end of a steel plate to the other, the welding method of the present invention, in which magnetic blow-preventing arc electrodes are provided before and after the arc welding electrode, allows the arc to It is possible to completely prevent the occurrence of the magnetic blow phenomenon that causes displacement in the direction, and thereby it is possible to prevent the occurrence of welding defects due to the magnetic blow phenomenon.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an example of the tip of a welding torch for carrying out the present invention, FIGS. 2 and 3 are explanatory diagrams of an example of the arc welding method of the present invention, and FIG. FIG. 3 shows how to use the welding torch at the welding start end, and FIG. 3 shows how to use the welding torch at the welding end. 1... Welding torch, 21, 23... Arc electrode for magnetic blow prevention, 22... Electrode for arc welding, 3
...Ar gas flow path, 4...steel plate, 5...arc.

Claims (1)

[Claims] 1. In a steel plate arc welding method in which welding starts from one end of the steel plate and ends at the other end, magnetic blow-prevention arc electrodes are provided before and after the arc welding electrode, and at least the above-mentioned arc welding electrode is provided at the welding start end. Welding is carried out while applying current in the same direction to an electrode and a magnetic blow prevention arc electrode provided in front of the electrode, and at the end of welding, at least the above-mentioned arc welding electrode and a magnetic blow prevention arc provided behind the electrode are welded. A magnetic anti-blow arc welding method characterized by welding while applying current to the electrode in the opposite direction.