JPS6015068A - Arc welding method - Google Patents

Abstract

PURPOSE:To diffuse heat input to a sheet to form a continuous bead and to weld without defect in arc welding the sheet by welding while oscillating a torch that supplies a welding wire in longitudinal direction along a weldment. CONSTITUTION:A MAG welding is performed using a small diameter welding wire and using mixed gaseous mixture of Ar gas and CO2 gas as shield gas. The sheet thickness of the weldments 1, 2 is less than 2-3 times diameter of the welding wire. The weldments 1, 2 are arranged in the form of a lap joint, and a tack welding 5 is made at plural places at a proper interval along a weld line. A welding torch 6 is so held by an adjusting device that the tip of a welding wire 7 obtains proper height from the weldment 1 on the weld line. The welding is performed by oscillating the welding torch 6 with an oscillating device along the weld line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an arc welding method for welding thin plates without droplets or undercuts.

[Technical background of the invention]

Along with the trend towards smaller and lighter 4K equipment such as switchboards and transformers, the casings are becoming thinner, and recently steel plates with a thickness of around 111111 have also been used. The welded parts of body plates are required not only to have a tight seal with the outside, but also to have sufficient mechanical strength. Conventionally, welding of thin plates like the one described above relies on acetylene gas welding or TIG welding. However, the former has large heat input, which causes distortion and limits the shape of the joint that can be used, while the latter has good heat concentration, so there are fewer restrictions on the shape of the joint, but the welding speed is slow and the use of CO2 gas The problem is that it is inefficient compared to the melt electrode welding method using shielding gas.

Therefore, in recent years, welding wire has been made thinner to improve arc stability in the small current range and the appearance of the weld bead.
A melt electrode type arc welding method (MAG welding) using a suitably mixed gas of Ar gas and CO2 gas as a shielding gas has been developed and has been widely adopted for welding thin steel plates.

[Problems with background technology]

However, even if MAG welding is used for welding thin plates, it is not possible to make the diameter of the welding wire extremely thin due to problems with welding wire feedability, and the amount of weld metal per unit plate thickness is not suitable for welding thick plates. The amount is much higher than that, and the entire thickness of the plate is heated to near its melting point at once. Therefore, the plate is thin < -x
The longer the plate itself melts, the more difficult it becomes to maintain its original shape.

In other words, the plate itself may melt or undercut. This phenomenon becomes noticeable when a joint gap exists between the two thin steel plates to be welded. For example, when welding a lap joint as shown in Figure 1, where there is a gap 4 between the welded materials 1 and 20 that is more than 1/2 to 1/3 of the plate thickness of the welded materials 1, The amount of weld metal in the weld bead 3 increases, and the molten weld bead 3 cannot be supported by the surface tension of the thin plate 1, and the amount of heat input to the welded material 1 also increases, synergistically Material 2 exhibits a phenomenon of melting and falling,
The weld bead 3 does not continue and a healthy bead shape cannot be obtained. Therefore, it is necessary to bring the materials to be welded 1 and 2 into close contact with each other so that no gap 4 is formed. Manual welding, in which the operator performs welding while observing with the naked eye, is a very troublesome task, but if necessary, the welding process is performed while adjusting the gap 4 by hitting the workpiece 1.2 with a hammer to make the gap 4 smaller. It can be carried out. - When welding is performed automatically without the intervention of a manual worker, it is difficult to adjust the welding material 1.2 in advance so as not to create a gap 4. In other words, in sheet metal processing, it is difficult to assemble the welded materials 1 and 2 with accurate dimensions, and as welding progresses, the welded materials 1 and 2
, 2 due to the thermal expansion of the material to be welded.

This is because the gap 4 between the two tends to widen. It is conceivable to use a strong jig to restrain the parts so that there are no gaps, but this would be cumbersome and inefficient to attach and remove, and the workpieces that could be used were limited to simple shapes. Therefore, it is generally difficult to continuously and automatically perform arc welding on lap joints of thin plates without operator intervention.

[Purpose of the invention]

The present invention is suitable for performing arc welding on thin plates.

To provide an arc welding method capable of performing arc welding that can easily form a reliable force by continuing the weld build by diffusing heat input to a thin plate to prevent the occurrence of welding defects such as melt dripping.

[Summary of the invention]

The arc welding method of the present invention performs welding while swinging a welding torch that supplies a welding wire in the same direction as the welding progress direction along the welding line of the welded material. It is characterized by reducing the amount of welding and human heat loss associated with one pass of the welding arc, and promoting the diffusion of heat input during second and subsequent passes through the weld bead formed by one pass of the welding arc. shall be.

[Embodiments of the invention]

Embodiments of the present invention illustrated in the drawings will be described below.

FIGS. 2 and 3 show an embodiment of the arc welding method of the present invention. This embodiment shows the configuration of a lap joint between a thin steel plate material 1 and a thin steel plate material 2. Arc welding is performed in Note that this arc welding is performed by MAG welding using a small-diameter welding wire and a mixed gas of Ar gas and CO2 gas as a shielding gas. Further, the plate thickness of the materials to be welded 1 and 2 is 2 to 3 times or less the diameter of the welding wire. When performing arc welding, the material to be welded 1 and the material to be welded 2 are arranged in the form of a lap joint, and tack welds 5 are performed in advance at multiple locations along the weld line at appropriate intervals between the two. I'll keep it. The welding torch 6 has a welding wire 7, which is supplied to the welding part of the workpiece 1.2, has a tip 8t, and is connected to the welding wire 7 through a welding cable connected to the tip 8. It is connected to the positive side of the type welding power source. The welding torch 6 holds the welding wire 7 by an adjustment device (not shown) so that its tip is at an appropriate height above the welding line between the welding materials 1 and 2 and from the welding material 1. In addition,
This adjustment device can move at a predetermined speed in the direction of the welding line, and is equipped with a swinging device that swings the welding torturro in the direction of the welding line along the welding line.The swinging period and movement speed during swinging are free. It is now possible to change it to . Materials to be welded 1, 2
Connect either one to the negative side of the welding power source. In the case of a lap joint, the position of the welding torch 6 should be kept within a range that is not more than 1.5 times the plate thickness of the welded material 1 in the direction perpendicular to the welding line and along the plate surface of the welded material 1. . The reason for this is that if the welding wire 7 moves further to the left from the welding line of the lap joint (perpendicular to the left direction with respect to the direction of welding progress, to the left in FIG. 3), the welding wire 7 will reach the workpiece l. The welding arc does not fly, droplets do not transfer to the welded material 1, and when it moves away to the right, the penetration into the welded material 2 is incomplete, and the end face of the welded material 1. It does not melt and remains in a divided state next to the weld bead, making satisfactory welding impossible in either case. When welding, pay attention to the length of the wire protrusion, that is, the distance between the tip 8 and the material to be welded. To prevent the 8-hair arc from creeping up, the appropriate distance is 10ft of the Y wire diameter! It is held by an adjustment device (not shown) to a certain degree. When performing arc welding, the welding torch 6 is moved forward at a constant speed along the welding line while swinging the welding torch 6 in the same direction as the welding line along the welding line of the workpiece 1.2. . Welding wire 7 integrated with welding torch 6
Also, while moving forward while repeating the forward and backward movement,
The material to be welded 1.2 is replenished by a welding wire feeding device (not shown) to compensate for the amount consumed due to the generation of welding arc.
During this process, a weld bead 3 is continuously formed along the weld line. The process of forming the weld bead 3 is as follows. When the welding movement speed is a (am/sec), the oscillation is b (4), and the oscillation frequency is n (Hz), the welding torch 6 starts moving in the welding direction and then moves in the opposite direction. The forward movement of the welding torch 6 in the forward movement until it starts retreating lasts n seconds, and the moving distance 11 during that time is l, = Kojub (aa)
, the welding torch 6 continues to retreat for 3 seconds until the next advance starts, and its retreat distance is 1t=b-'' (tomo).Then, the welding bead 3 including the retreating section of the welding torch 6 continues for 3 seconds until the next advance starts. The weld bead 32 from the backward stroke is layered on the weld bead 31 from the stroke, and the weld bead 31 from the forward stroke is further layered on top of that.Here, the welding torch 6
so that 172 of the forward distance becomes the backward distance, that is, 0.
If the welding movement speed, oscillation, and oscillation (number of oscillations) are selected so that the relationship = 3a is established, the welding bead 3 will include a backward stroke over the entire line, and the entire line will be a uniform forward welding bead. 31 Retracted weld bead 3
2. The forward weld bead 31 is laminated. At this time, the welding speed S1 in the forward stroke is s, = (-!+b)/-! -=4
a, the welding speed S2 in the backward stroke is 2n 2n S2 = (-earth b) / earth = 2a, and the welding torch 6 is not swung by 2n 2n, that is, the welding speed a is used to weld the materials l and 2.
Compared to when welding, the heat input associated with one passage of the welding arc is 1/4 and 1/2, respectively.

Furthermore, since the thickness of the welding bead 3 is inversely proportional to the welding speed, the bead thickness of the forward welding bead 31 and the backward welding bead 32 is equal to the welding bead thickness at a normal welding speed a where the welding torch 6 cannot be oscillated. 1/4, 1/2. According to this welding method, the heat input welding bead 32 per unit length of the welded material 1 due to the first forward welding bead 31 is also 1/1 of that of the conventional method.
The heat input decreases to 2, and the material to be welded is laminated on top of the first advancing weld bead 31, whose temperature has already risen. However, since the lamination is completed within seconds, the temperature increase due to the advancing weld bead 31 is due to the welding material 1. .2, the temperature rise during the backward welding bead 32Ia layer of the workpiece 1 is lower than the temperature rise due to heat input of (1/4 + 1/2) in the conventional method. Therefore, the backward weld bead; 32 can be stacked. A second forward weld to the backward weld bead 32 whose temperature has similarly increased can also be laminated.

FIG. 4 schematically shows this.

In the normal rocking method, which is parallel to the surfaces of the welded materials 1 and 20 and perpendicular to the weld line, the heat input to the welded materials becomes locally wavy, and the welded materials 1 and 20 in the process of approaching the welded materials 1, 20 The heat input per unit length is at the same level as in the welding method without rocking, and as a result, the welded material 1 melts and undercuts occur in a wave-like manner, as shown in Figure 2. Lap welding of thin plates with such a gap 4 is not possible.

In the above embodiments, the case of a lap joint is taken as an example, but the case is not limited to this, and in the case of a butt joint of thin plates shown in FIG. 5 or a fillet joint of thin plates shown in FIG. Welding can be performed in exactly the same way in the case of edge joints of thin plates as shown. The oscillating motion of the welding torch 6 along the front and back direction of the welding line is not limited to the one that draws a zigzag trajectory as in the above embodiment, but the same effect can be obtained even if the welding torch 6 oscillates in a long oval shape in the direction of the welding line. is obtained.

〔Effect of the invention〕

As explained above, when welding thin plates, the arc welding method of the present invention increases the heat transfer effect of the weld bead formed with low heat input to the workpiece and dissipates heat due to the time difference. By giving the effect of substantially reducing the heat input per unit length to the material, welding defects such as melt drop in the material to be welded can be prevented, a continuous weld bead can be formed, and welding can be performed reliably. I can do it. In particular, even when there is a gap in the welded part of a thin plate, welding can be easily and reliably performed and it is effective, and furthermore, the work can be automated.

[Brief explanation of drawings]

FIG. 1 is a side view showing a lap joint type welded structure. 2 and 3 are respectively a front view and a side view of an embodiment of the arc welding method of the present invention, and FIG. 4 is an explanatory diagram partially sectionally showing a weld bead in the same embodiment. FIG. 5, FIG. 6, and FIG. 7 are side views showing welded joints to which the arc welding method of the present invention can be applied. 1.2 Material to be welded 3, 31.32...Weld bead 4
Gap 6... Welding torch 7 - Welding wire 8 Tip

Claims (1)

[Claims] (1) An arc welding method characterized by performing welding while swinging a welding torch that supplies welding wire back and forth along the welding line of the material to be welded.