JPS6252667B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding method, and more particularly to an arc welding method in which molten metal in a molten pool is agitated during welding to improve the properties of the weld.

It is known that the arc or molten metal is vibrated ultrasonically, magnetically, or mechanically during welding in order to improve properties such as refining grains in the weld zone and preventing blowholes and hot cracking. There is.

Among these, those that apply magnetic vibration to the molten metal itself have conventionally used direct current or commercial frequency alternating current as the magnetizing current for direct current welding, and therefore have the following drawbacks. That is, (1) it only targets DC welding, and therefore does not cover AC welding, which is the most commonly used process, so it has little industrial value.

(2) When a DC magnetic field is applied to a DC welding current, the molten pool only oscillates in the same direction, so there is little effect on improving properties.

(3) Applying a magnetizing force directly to the welding current at a commercial frequency alternating current causes the oscillation direction of the molten pool to change every 1/50 or 1/60 seconds, but the molten metal has no inertia. Because of its large size, it is difficult to oscillate in short periods, and therefore the effect of improving properties is small.

The present invention was proposed in view of the above circumstances, and aims to provide an arc welding method that refines the crystal grains of molten metal and prevents the generation of blowholes. When flowing an electric current to generate an arc and shaking the molten metal by passing a magnetizing current through a magnetizing coil, the magnetizing current is made variable at any frequency from direct current to commercial frequency, and the welding current itself is pulsed. It is characterized by its fluidity.

An embodiment of the present invention will be explained with reference to the drawings.
Figure 1 is a block diagram showing the circuit, Figure 2A
is a partially enlarged view of Figure 1, and Figure B is B-B of Figure A.
Figure C is a perspective view of Figure B, Figure D is a plan view along Figure C.
is an explanatory diagram showing the relationship between the welding current, magnetizing current, magnetic field lines, and molten pool rotating direction in Figure A, Figures 3A and B are line diagrams showing the DC welding current and rectangular wave magnetizing current, respectively. Diagrams showing the relationship between the frequency of the magnetizing current and the number of blowholes in the case of welding using the welding current and magnetizing current shown in Figures 3A and B, and Figure 5A showing the waveform of a pulsating welding current obtained by superimposing a pulse train on direct current. Figures B and C are cross-sectional views showing the molten pool at B and C in Figure A, respectively. Figure 6 shows the case where the welding current and magnetizing current are synchronized in a rectangular waveform; A perspective view of the molten pool, B in the same figure is a waveform diagram of the welding current, C1, C2, and C3 in the same figure are waveform diagrams showing the magnetizing current, respectively, and Figure 7 is the welding shown in Figure 6 (i) without stirring. FIG. 3 is a diagram showing the change in the number of blowholes in the case of (ii) the case where the welding current and the magnetizing current are not synchronized, and (iii) the case where they are synchronized.

First, in Fig. 1, 1 is the material to be welded, 2 is the welding wire, 3 is the welding power source, 4 is the welding current power supply cable, and 5 is a control device that controls welding conditions such as welding current, welding voltage, frequency, and pulse value. , 6 is a magnetizing coil attached to the welding torch and wound around the welding wire 2 as an axis; 7 is a magnetization condition control device for controlling magnetization conditions such as magnetization current and frequency; 8
9 is a welding current, and 10 is a molten pool.

In such an apparatus, first, as shown in FIG. 2, when welding is carried out by setting the welding current and magnetizing current to direct current, magnetic lines of force 8 are generated in the same direction as the welding wire 2, as shown by the solid line, and the molten pool 10 and passes through the material to be welded 1 and heads downward. On the other hand, as shown by the broken line, the welding current 9 flows horizontally from the arc column to the base metal, melts the base metal due to arc heat, and creates a molten pool 1.
form 0.

Therefore, in the molten pool 10, as shown in Figures B and C, the molten metal rotates in the circumferential direction indicated by the arrow 11 according to Fleming's left-hand rule, and the direction of rotation is as shown in Figure D. As shown, the welding current and magnetizing current differ in direction.

Therefore, for example, when a DC welding current is applied as shown in Figure 3A, and a rectangular wave current as shown in Figure 3B is applied as a magnetizing current, the molten pool moves to the right according to the alternating cycle of the magnetizing current. Rotates alternately clockwise and counterclockwise.

At this time, changing the magnitude or frequency of the magnetizing current depending on the welding conditions is effective for swinging the molten metal, and the magnetizing current may be a sine wave instead of a rectangular wave.

Figure 4 shows an example of the number of blowholes in a weld when the frequency of the magnetizing current is changed. When there is no stirring, at around 5 to 15Hz, there are fewer blowholes, and when the frequency is higher, the molten metal becomes more inert due to the inertia. rotation is reduced and the blowhole prevention effect is degraded.

Next, as shown in FIG. 5A, if a rectangular wave pulsating current is used, which is a rectangular wave superimposed on the DC welding current,
At time B, the base current 12 flows and the arc force is weak, so as shown in FIG. A peak current 16 flows and a strong arc force acts, and the molten pool becomes deeply concave just below the arc, as shown in FIG.

At this time, when a rectangular wave magnetizing current as shown in Fig. 3B is applied, in addition to the vertical movement of the molten metal due to the rectangular wave pulsating welding current, a rotating force based on the rectangular wave magnetizing current acts. As shown in FIG. 6A, the stirring power of the molten metal is doubled.

As shown in C1, C2, and C3 in the same figure, the magnetizing current has a direct current, a square wave alternating current, a pulse train waveform, etc., but in any case, when the magnetizing current frequency is synchronized with the welding current frequency, the rotation of the molten metal is The motion and stirring effects are significant.

Figure 7 shows the number of blowholes corresponding to each of the following weldings: (i) without stirring, (ii) when welding current and magnetizing current are not synchronized, and (iii) when welding current and magnetizing current are synchronized. This shows that (ii) is more effective in reducing blowholes than (i), and (iii) is more effective than (ii) in reducing blowholes.

In short, according to the present invention, when a welding current is passed through the welding wire and the material to be welded to generate an arc and the molten metal is oscillated by passing a magnetizing current through the magnetizing coil, the magnetizing current is varied from direct current to commercial frequency. By making the welding current itself variable to any arbitrary frequency and making the welding current itself a pulsating flow, an arc welding method that improves the properties of the welded part is obtained.
The present invention is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit according to an embodiment of the present invention, FIG. 2A is a partially enlarged view of FIG. 1, and FIG.
is a plan view taken along line B-B in figure A, and figure C is a plan view along line B in figure A.
Figure D is an explanatory diagram showing the relationship between the welding current, magnetizing current, magnetic field lines, and molten pool rotation direction in Figure A, and Figures A and B show DC welding current and rectangular wave magnetizing current, respectively. Figure 4 is a diagram showing the relationship between the frequency of the magnetizing current and the number of blowholes in the case of welding using the welding currents and magnetizing currents in Figures 3A and B, and Figure 5A is a diagram showing the relationship between the frequency of the magnetizing current and the number of blowholes in the case of welding using the welding currents and magnetizing currents shown in Figures 3A and B. Figure 5A is a diagram in which a pulse train is superimposed on the direct current. Figures B and C are cross-sectional views showing the molten pool at B and C in Figure A, respectively. Figure 6 shows the case where the welding current and magnetizing current are synchronized in a rectangular waveform. Figure A is a perspective view of the molten pool, Figure B is a waveform diagram of the welding current, and Figures C1 and C are
2 and C3 are waveform diagrams showing the magnetizing current, respectively.
The figure shows the welding shown in Figure 6 (i) without stirring;
(ii) A diagram showing the change in the number of blowholes when the welding current and the magnetizing current are not synchronized, and (iii) when they are synchronized. 1... Material to be welded, 2... Welding wire, 3... Welding power source, 4... Power supply cable, 5... Control device,
6... Magnetizing coil, 7... Control device, 8... Lines of magnetic force, 9... Welding current, 10... Molten pool, 11...
...Rotation direction, 12... Base current, 14... Pushing force, 16... Peak current, 17... Pushing force.

Claims (1)

[Claims] 1. When welding current is passed through the welding wire and the material to be welded to generate an arc, and the molten metal is oscillated by passing a magnetizing current through the magnetizing coil,
An arc welding method characterized in that the magnetizing current is variable at any frequency from direct current to commercial frequency, and the welding current itself is a pulsating flow.