KR20050088884A - Improvement in gas metal arc welding uitlizing external electromagnetic force - Google Patents

Abstract

The present invention relates to the improvement of the gas metal arc welding method, and more particularly to a gas metal arc welding method that can improve the welding efficiency and welding quality by using an external electromagnetic force.

The present invention provides a gas metal arc welding method characterized in that when welding by the gas metal arc welding method, a magnetic force of about 300 Gauss is applied to the tip of the welding wire, and the welding is performed using the welding wire as the S pole. The magnetic force is applied to the metal displacement volume formed at the tip of the welding wire during welding to reduce the spatter, improve the shape of the weld bead, and improve the welding efficiency and welding quality.

Description

Gas metal arc welding method using external electromagnetic force {IMPROVEMENT IN GAS METAL ARC WELDING UITLIZING EXTERNAL ELECTROMAGNETIC FORCE}

The present invention relates to the improvement of the gas metal arc welding method, and in particular, by welding in the state of applying the appropriate external electromagnetic force to the tip of the welding wire during welding, to reduce the spatter, improve the bead shape, improve the welding efficiency and welding quality It relates to a gas metal welding method using an external electromagnetic force that can be made.

Gas metal arc welding (GMAW) related to the present invention uses a welding method to continuously supply the electrode electrode wire while using a separate protective gas, and to generate an arc at the tip to transfer the volume to the molten area. Say. The gas metal arc welding method is classified into various welding methods according to the type of protective gas.

In Korea, welding using CO ₂ gas with low gas price and deep penetration is most widely used, but welding quality is poor and smoke, sputter generation is disadvantageous, and high-speed welding by automation is difficult. The rise in production costs due to the need for treatment has been pointed out as a problem.

In the case of welding using CO ₂ gas, it is known to perform repelling transter, and it is known that a large amount of spatters are generated due to such repulsion. There are several theories about the causes of repulsion in CO ₂ gas atmospheres, including the Cathode Jet theory and the Plasma Buoyance Force theory. Therefore, in order to expand the application of the CO ₂ gas welding, it is required to establish a way to improve the welding quality by reducing the spatter generation.

Currently, various researches for reducing spatter generation have been conducted, such as a study on welder characteristic control through welder waveform control, a study on welding material, and a study on ultrasonic vibration, but the effect is still insufficient.

The present invention has been studied in the background, by applying an external electromagnetic force to the force acting on the volume during welding by the gas metal arc welding method to minimize the spatter generation, improve the shape of the bead through the analysis of the change of the volume transition welding An object of the present invention is to provide a gas metal welding method using an external electromagnetic force to improve efficiency and welding quality.

Hereinafter, the present invention for achieving the above object will be described in detail with reference to the accompanying drawings and embodiments.

In arc welding, the metal transition phenomenon appears in various forms depending on the welding material, the protective gas, and the welding conditions, because the magnitude and direction of the forces acting on the volume of the wire tip change as the welding parameters change. Figure 1 shows the forces acting on the volume. When welding to the base material 2 using the welding wire 1 by the gas metal arc welding method, the forces acting on the volume 3 formed at the end of the welding wire 1 are largely gravity, surface tension, electromagnetic force, There are repulsive forces, and the surface tension is hardly affected by the current, and the remaining forces are greatly affected by the magnitude of the welding current. In particular, the electromagnetic force increases linearly as the welding current increases, becoming the largest force above 250A. Therefore, the surface tension acts as the largest force in the low current region, but the electromagnetic force plays a leading role in the high current region.

According to the classification of high-speed cameras presented by the International Insitute of Welding (IIW), the metal transition modes generated by gas metal arc welding are classified into three modes: granular displacement, short-circuit and spray transition. This transition mode has a great influence on the welding quality, such as arc stability, penetration depth and spatter generation amount, depending on the welding current, welding voltage, welding wire feeding speed, arc length and type of protective gas.

The present invention is equipped with an electromagnetic force source such as the solenoid 5 at the tip of the welding torch 4 as shown in FIG. 2 to perform welding while applying an external electromagnetic force of an appropriate magnitude by the solenoid to the welding portion. It is done.

The force acting between the stimulus and the stimulus is called a magnetic force, and the magnetic field refers to any space in which the magnetic force generated around the stimulus or around the conductor through which current flows. When the solenoid 5 made of a long cylindrical wire wound to supply an external magnetic field is mounted and operated at the tip of the torch 4, a magnetic force line 6 and a magnetic field as shown in FIG. 2 are formed. In the case of flowing the voltage and current of 12V, 0.13A with different polarity, the magnetic flux density acting on the tip of the welding wire located in the welding part is about 300 Gauss, and the theoretical distribution of the two-dimensional magnetic field is shown in FIGS. same.

In the following, the present invention will be described in more detail through examples.

(Example)

1. Experimental Materials and Devices

(1) experimental material

The base material was a general structural rolled steel, and the weld base material (see Table 1) was machined to a size of 100 (W) x 200 (L) x 10 (t) mm. The welding wire used a 1.2 mm diameter, solid wire for mild steel CO ₂ welding (see Table 2). The protective gas was CO ₂ gas and the flow rate was 15 L / min.

(2) experimental device

The experimental apparatus used a 400A class welder, a wire feeder, and an automatic welding trolley. As for the external magnetic field supply, a solenoid (see Table 3) wound with a long cylindrical shape and a DC power supply, such as the solenoid 5 of FIG. 2, were used.

2. Experimental method

The bead on plate CO ₂ welding (see Table 4) was performed by changing the direction and size of the magnetic flux density as shown in Table 5 while all welding parameters were the same, and the intensity of the magnetic flux density was Gaussian at the end of the welding wire. Measurement was made using a Gauss meter.

<Table 1>

Ingredient of base material

<Table 2>

Welding wire components

<Table 3>

Solenoid properties

<Table 4>

Bead on Plate CO ₂ Welding Conditions

In Table 4 above, CTWD stands for Contact Tip to Workpiece Distance and means the distance from the end of the welding wire to the base metal.

<Table 5>

Example Conditions

3. Experimental Results

(1) Bead appearance and macro photograph

For specimens 3 and 5, which supplied a magnetic flux density of 500 Gauss, no particular difference was found with specimen 1 that did not supply a magnetic flux density.However, specimen 2, which supplied a magnetic flux density of 300 Gauss (S pole) was not found. It was found that spatter scattering and the size of each spatter were significantly reduced than those of the first specimen.

Analysis of the penetration depth, bead, width, and dent height of the specimen through macro photography resulted in the results shown in Table 6. The penetration depth was found to be mostly shallower than that of the first specimen without the magnetic field, but the depth of the second specimen was appear. The highest specimen was found in Psalm 1, which did not have a hull height. Figure 5 shows the bead appearance and cross-sectional shape of the above welding test results.

<Table 6>

Penetration depth, bead width, tooth height

(2) spatter collection

The spatter generation ratio (SGR%) was calculated by measuring the amount of spatter generated during welding under the same welding conditions, and the results are shown in Table 7.

<Table 7>

Spatter Rate

4. High speed photography of metal transition

Figure 6 shows the results of high-speed imaging of metal transition during welding. In the case of welding without a magnetic field, the volume moves without direction in the wire tip as in (a), but in the case of applying an external magnetic field (b), ( It can be observed that the volume rotates in a constant direction at the tip of the wire as in c). That is, as shown in (b) and (c), when the wire tip is the S pole, the volume is shifted while rotating clockwise, and in the case of the N pole, the volume is shifted while being rotated counterclockwise.

5. Welding waveform

The waveforms for 0.5 seconds from 15 seconds to 15.5 seconds of the total welding time of 25 seconds were divided into 2500 measurements. The results of the measurement are shown in Table 8.

When a short circuit occurs, the current passing through the bridge causes the accumulation of thermal energy, causes an explosion, and generates an arc. The instantaneous shock waves scatter molten metal in the bridge and the molten pool and become a spatter. The largest number of arc shorts was found in the first experiment without the magnetic field, while the second was the shortest.

<Table 8>

Welding waveform measurement result

As can be seen from the above welding waveform measurement result, when the magnetic field is applied, the volume is rotated and the number of short circuit is reduced, and when the magnetic flux density of 300 Guass S pole is applied to the wire end, the amount of spatter is significantly reduced. Can be.

As described above, according to the present invention, the bead appearance, displacement mode, short-circuit, spatter generation amount, and the like during gas metal arc welding using magnetic force generated by an external magnetic field were analyzed.

That is, in the above experimental example, the bead appearance is cleaner than when the low magnetic flux density of about 300 Gauss is applied to the welding wire tip during welding, especially when the wire tip is S pole, and the penetration depth is also higher. We checked the depth.

In addition, as a result of measuring the amount of spatter generated during welding, the spatter generated was much less than the case where the low magnetic flux density of 300 Gauss was applied to the tip of the wire. In the case of S-pole, spatter generation amount was small.

In addition, as a result of the welding waveform measurement, when the magnetic flux density of 300 Guass S pole was applied to the wire end, the number of short circuits was the lowest, which is considered to be the cause of reducing the spatter generation.

In addition, when high-speed imaging of the metal transition during welding gave a magnetic field, the volume rotated at the tip of the wire, and as the magnetic flux density increased, the rotational speed increased, which seems to have played a significant role in reducing the number of short circuits. .

Therefore, it was confirmed that an optimum welding result can be obtained when the welding is performed by applying a 300 Gauss S-pole magnetic field to the tip of the welding wire.

On the other hand, when the magnetic flux density of 500 Gauss or more is given in the above experimental example, it is determined that the amount of spatter cannot be reduced because the centrifugal force acts as the volumetric rotational speed becomes too high, causing the volume to bounce outward.

The magnetic flux density value of the external magnetic force mentioned above is limited to a specific experimental example, and according to the change in the scale or characteristics of the related welding device, the external magnetic force of the above-mentioned effect is applied to the welding device in the range of 50 to 3000 Gauss. It may be chosen to be the optimal value.

As described above, the present invention is expected to be usefully applied industrially since it can greatly improve the quality and efficiency of gas metal arc welding in a simple and efficient manner without additional cost.

1 is a front view showing the forces acting on the volume of the tip of the welding wire during welding;

2 is a perspective view of an essential part of a device for carrying out the welding method of the present invention;

3 and 4 are two-dimensional distributions of the magnetic field acting on the tip of the welding wire during welding by the method of the present invention,

5 is a view showing a comparison of the shape of the weld bead when welding is performed by the conventional method and the method of the present invention,

Figure 6 is a comparative photograph showing a high-speed photographing of the metal transition phenomenon appearing when welding by the conventional method and the method of the present invention.

Explanation of symbols on main parts of drawing

1: welding wire 2: base material

3: volume 4: torch

5: solenoid 6: magnetic field lines

Claims (3)

In the welding by the gas metal arc welding method, welding is performed by applying an external magnetic force to the leading end of the welding wire. The method of claim 1, wherein the strength of the external magnetic force is in a range of 50 to 3000 Gauss. The gas-metal arc welding method according to claim 1 or 2, wherein the welding is performed by using the welding wire as the S pole.