JPH0117793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for arc welding by pulling out a wire loaded in a pail pack, which can obtain a good weld bead that does not meander, has good contact energization by a contact tip, and has a good arc condition. The purpose is to provide a method.

Traditionally, some of the wires used for semi-automatic and automatic welding such as CO ₂ gas shield welding and MIG welding are made by looping a continuous wire into a cylindrical container with a diameter of 500 mm to 800 mm called a pail pack. There are packaging types that can be loaded with weights ranging from several tens of kilograms to several hundred kilograms. When using the wire loaded in this pale pack,
A wire drawing device incorporating a straightening roller, a guide tube, etc. is installed on top of the pail pack loaded with wire, and the wire that has been plastically deformed into a loop shape and has a bend is sequentially pulled out from the pail pack, and the wire is pulled out by the straightening roller. It is taken out while being straightened. This is shown in Figure 1 a and a.
To explain using b, which is a cross-sectional view taken along line A-A',
The wire W is loaded in a flower pattern between the outer tube 1 and the inner tube 2 of the pail pack as shown in Figure b to prevent it from getting tangled when being pulled out, but the wire W is loaded in a loop shape to make it easier to load it into the pail pack. Since the wire is curved, it is supposed to be straightened as much as possible by the straightening roller 5 installed in the wire drawing device as shown in Figure 1A, when the wire is used. In reality, correction is difficult and often cannot be done adequately. For this reason, conduit tube 6,
The wire coming out of the welding torch 3 via the wire feeding device 9 has a curved line.

FIG. 2 is a diagram showing the bent state of the wire W when the wire W coming out from the welding torch 3 is left standing in the longitudinal direction of the wire in a natural state without applying any external force on the plane 8. has a flat spiral shape as shown in the figure. a is a front view, b is a plan view seen from above, and c is an end view seen from the longitudinal direction of the wire,
l ₁ and l ₂ in the figure indicate the respective pitches and wave widths of the wire W exhibiting a wavy shape in the plan view b,
Further, l ₃ indicates the height of the wire W rising from the plane 8 in the front view a and the end view c. For example, a bobbin-wound supply wire with a diameter of 1.2 mm is plastically deformed and bent, then 200 kg is loaded at a wire charging speed of 110 m/min and a pail pack rotation speed of 110 revolutions/min, and after being left for 2 weeks, it is passed through a straightening roller and then When taken out by the welding torch of a semi-automatic welding machine, the pitch l ₁ = 2300 mm, the wave width l ₂ = 300 mm, and the rise height l ₃ = 5 mm. The one that comes has a large bend.

The shape that appears on the weld line when welding with such a wire will be explained with reference to FIGS. 1a and 3. A wire of a certain size and shape is bent into a loop and is loaded in a pail pack, and is continuously pulled out, passes through a conduit tube 6 and a wire feeder 9, and comes out from the tip of a welding torch 3. However, at this time, the wire W comes out bent as shown in Figure 3 a, so
The tip of the wire deviates from the target position P on the steel plate 7 to be welded, which is located at a predetermined distance from the torch 3, and performs a circular motion on the steel plate 7 to be welded. If the locus of the circular motion is developed on the steel plate to be welded, theoretically it will become a wavy locus as shown in Figure 3b, where l indicates the width of the wave. In reality, the wire coming out of the welding torch experiences contact resistance from the inner surface of the conduit tube and the inner surface of the contact chip, so the twist is not in a completely open state, but is determined by the balance between the contact resistance and the recovery force of the twist.
When the force for recovery becomes large, the tip of the wire becomes a locus in which sudden swings occur at one time, as shown in FIG. 3c. In fact, when a welding test was conducted using a conventional wire with a diameter of 1.2 mm and a wire protrusion length of 30 mm, the center line of the weld bead deviated from the intended position by 2 mm to 8 mm (=width l of the wave), resulting in a meandering bead.

The wire loaded in the conventional pail pack was used while being straightened to be as straight as possible by one set of a pulling device or two sets of orthogonal straightening rollers, but due to the above-mentioned reasons, the weld bead The fundamental defect of meandering could not be prevented, and it was unsuitable for welding in places where the straightness of the weld bead is important. Despite this, the reason why Pail Pack wrapping wire is in demand today is that it can load up to 300 kg of wire, so long beads do not break midway, the number of wire replacements is reduced, and welding costs are lower. This is because it has the great advantage of being inexpensive.

In order to solve the problem of the weld bead meandering when the wire is pulled out while the pail pack is fixed, as mentioned above, a method has been put into practical use in which the wire is pulled out while rotating the pail pack. Alternatively, a complicated control device is required to drive or stop the pail pack when welding is stopped. Therefore, there were drawbacks such as high equipment costs.

On the other hand, as another countermeasure, a method is available in which the wire is loaded with a reverse twist when loading it into the pail pack, and this counterbalances the twist when it is pulled out to prevent the tip of the drawn wire from swinging as much as possible. However, since the reversely twisted wire passes through the contact chip in a substantially straight line, it has the disadvantage that it tends to cause arc instability due to poor conduction of electricity when the contact chip contacts the inner surface of the wire through hole.

The present invention solves the problems of the prior art described above. The arc welding method of the present invention has substantially no plastic bending deformation in the longitudinal direction of the wire.
The method is characterized in that the small diameter wire loaded in the pail pack is pulled out with linearity inherent in it, passed through a conduit tube and a wire feeding device, and then welding current is applied using a contact tip with a curved through hole. The welding method of the present invention will be described in detail below.

As is well known, in the loading process of this type of wire, the wire that has gone through the plating process and the skin pass process is
The wire is wound onto a bobbin with a capacity of 300 kg, and the wire is pulled out from this bobbin and loaded into a pail pack to produce a product. Wrap the wire around a rotating shaft with an appropriate diameter two to three times so that the wire has a diameter between the diameters of the cylinder and the inner cylinder, press it with guide rollers arranged oppositely, and bend it even here. The wire that has passed through the rotating shaft is further passed through a curved guide nozzle and guided to the pail pack, but in the process of loading the wire into the pail pack used in the welding method of the present invention, the wire is wound around the shaft. The rotary shaft is stopped and is simply held down by the rotating shaft and an endless belt placed opposite it (to provide driving force), or the shaft is also made into an endless belt and held down by two endless belts,
It is guided to the pale pack through a straight nozzle. In this way, the wire can be guided into the pail pack in a straight line. If the wire is wound around the shaft only once, the wire will form a large circle with a diameter of about 3 m in the open state, so it can be considered to have substantially linearity.

According to this method, when taking out the wire from the pail pack, the wire is pulled out from the welding torch without having to be straightened into a straight line using complicated and excessive straightening rollers. When left in a natural state, the wire does not have a large bend as in conventional wires, but instead becomes a substantially straight wire. For example, straighten a 1.2 mmφ bobbin-wound supply wire into a straight line, load 200 kg at a wire loading speed of 110 m/min, and a pail pack rotation speed of 110 rpm. After leaving it for 2 weeks, the wire on the top of the pail pack is straightened without a straightening roller. The straightness of the wire when taken out by the welding torch of a semi-automatic welding machine is pitch l ₁ = 3000 when it is left in a natural state on a flat surface without applying any external force.
mm, the wave width l ₂ = 50 mm, and the rising edge l ₃ = 0, making it almost linear.

Figure 4 shows the results of welding using such a wire. As shown in Figure a, the wire W coming out of the welding torch 3 hardly swings, so the tip of the wire does not deviate from the target welding position P on the steel plate 7 to be welded, which is a predetermined distance away from the welding torch 3. As shown in FIG. b, the trajectory of the wire tip on the steel plate 7 to be welded is in a substantially straight line. Note that the dotted line 4 in Figure a shows the trajectory of the wire in the prior art for comparison. for example
Wire protrusion length 30 using the inventive wire with a diameter of 1.2 mm
When welding was carried out at mm, there was almost no deviation of the center line of the weld bead, and even if there was, it was less than 1 mm, and it was almost straight.

The welding method of the present invention is characterized in that such a wire is used, and a contact tip for contacting and energizing the wire has a curved wire through hole. The reason for this is that when the wire with the above-mentioned linearity is fed and brought into contact with the contact chip to energize, if the wire through-hole of the contact chip is straight, the inner surface of the wire through-hole and the wire This is because insufficient contact will result in poor conduction and the arc will become unstable. In severe cases, sparks may occur within the through hole, resulting in welding and stopping wire feeding. The curved shape of the through hole may be any shape as long as it allows sufficient contact energization. An example is shown in FIG. In the contact chip 10 shown in FIG. 5, the center lines 11' and 12' of the wire entrance 11 and wire exit 12 of the through hole are bent at an angle .theta.. In order to obtain a good arc condition, it is preferable that the bending angle θ is in the range of 1° to 10°.
This is because if θ is less than 1°, contact failure will occur and the arc will become unstable, just like in the case of a straight through hole, and if θ exceeds 10°, the contact resistance between the wire and the through hole will increase. This is because wire feeding performance deteriorates, and the wire pulled out from the tip of the contact tip is bent more than necessary, making welding defects such as blowholes more likely to occur due to poor gas shielding.

FIGS. 6 and 7 are diagrams showing arc conditions in actual welding using welding current and welding voltage. FIG. 6 shows the arc state when welding a wire with inherent linearity by applying welding current using a contact tip with a straight through hole, a shows the welding current, and b shows the fluctuation state of the welding voltage. Note that the wire used at this time was 1.2 mm, and the hole diameter of the contact chip through hole was 1.3 mm. Further, FIG. 7 shows the arc state when the welding method of the present invention is used, that is, when welding is carried out by contact energization using a contact tip with a bent through hole, a shows the welding current, and b shows the fluctuation state of the welding voltage. The wire used at this time was 1.2 mm, the contact tip had the shape shown in FIG. 5, the diameter of the through hole was 1.3 mm, and the bending angle θ was 5°. In both FIGS. 6 and 7, CO ₂ gas-shielded arc welding was performed using the apparatus shown in FIG. 1 (however, the straightening roller 5 was not used in FIG. 7) under the following welding conditions.

Welding current: 200A Welding voltage: 27V Welding speed: 65cm/min Wire protrusion length: 20mm CO ₂ flow rate: 20l/min From Figure 6, when a wire with inherent linearity is welded by contact energization with a contact tip with a straight through hole, It was found that the welding current and voltage were unstable and the arc condition was extremely poor.
It can be seen from the figure that even if the wire has inherent linearity, if the through hole of the contact tip that conducts contact current has a bend, both the welding current and voltage will be stable and the arc condition will be good. If the wire through hole of the contact chip is curved, the wire will naturally protrude in the curved direction, but since there is no bend, the wire protrudes in a constant direction and does not move in a circular motion as in the conventional case.

According to the present invention, there is no deviation from the target welding position, so welding defects such as poor fusion do not occur, and there is no need for rework due to bead meandering.
Furthermore, the wire used in the present invention does not undergo plastic deformation (bentness) and has a small diameter even if it is straight when loaded into the pail pack. Since the wire can be wound into a loop of a size of No tangles occur. Furthermore, since it can be freely loaded into a pail pack of any size, there is no need to limit the size of the pail pack, and a conventional size pail pack can be fully loaded. Note that the small diameter wire in the present invention refers to a wire with a diameter of 3.2 mm or less. Further, in the present invention, "substantially no plastic deformation" includes bends with a diameter several times the outer diameter of the pail pack that are unavoidably generated in the wire during the process of loading the wire into the pail pack. As long as the wire is loaded into the pail pack with substantially no plastic deformation and inherent straightness, the wire may have the above-mentioned reverse twist.

The effects of the present invention are summarized as follows. (1)
The weld bead becomes substantially straight, and a good weld bead without meandering can be obtained. (2) No correction mechanism is required when pulling out the pail pack, improving welding efficiency. (3) The wire pulled out from the pail pack is fed to the welding area through a conduit tube, but as it passes through the conduit tube, the linearity of the wire makes the frictional resistance extremely small, resulting in good feeding. You can get sex. (4) Since the welding current is applied using a contact tip having a bend in the through hole, even if the wire has inherent straightness, the current conduction state is good, the arc state is extremely good, and a good weld bead without meandering can be obtained.

[Brief explanation of drawings]

Figure 1a is a cross-sectional view showing the state of the wire loaded in the pail pack when it is pulled out, Figure b is a cross-sectional view taken along the line A-A' of the pail pack in Figure a, and Figure 2 is the wire coming out of the welding torch. A is a front view, b is a plan view, and c is an end view, showing the bending state of the wire when the wire is left standing in the longitudinal direction in a natural state without applying any external force on a plane. Figure 3 is a diagram showing the state when welding using wire in the conventional technology, where a shows the deviation of the wire tip from the welding target position, and b and c show the beat locus on the steel plate to be welded. Figure 4 shows the state of welding according to the present invention, where a shows the state of the wire coming out of the welding torch, and b shows the bead locus on the steel plate to be welded. Fig. 5 is a schematic cross-sectional view of a contact tip, and Fig. 6 is a diagram showing the arc state when a wire with inherent linearity is welded by contact energization with a contact tip with a straight through hole, and a is a welding current. FIG. 7 is a waveform diagram showing the arc state when welding by the welding method of the present invention, a is the welding current, and b is a waveform diagram showing the fluctuations in the welding voltage. 1...Outer cylinder of the pale pack, 2...Inner cylinder, 3...
...Welding torch, W...Welding wire, 10...Contact chip with bent through hole.

Claims (1)

[Claims] 1. A method of arc welding by drawing out a small diameter wire loaded in a pail pack, in which the wire loaded in the pail pack is pulled out in a state in which there is no substantial plastic bending deformation in the longitudinal direction of the wire and there is inherent linearity. An arc welding method characterized in that the wire is pulled out from the wire, passed through a conduit tube and a wire feeder, passed through a contact tip with a curved through hole, brought into contact with the contact tip, and energized to perform welding. .