JPH0221911B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a high-speed MIG welding method that uses a higher current than conventional MIG welding to achieve deep penetration at high speed and to obtain a bead shape without defects such as poor fusion and overlap. This relates to arc welding. (Prior art and problems) Conventionally, multi-electrode MIG welding has been used with the main purpose of improving welding efficiency and weld toughness, but increasing the welding speed reduces the amount of deposit per unit weld length and The depth of penetration decreases. On the other hand, from a practical standpoint, a certain amount of welding amount and penetration depth are always required, so the higher the welding speed, the higher the amount of production wire fed and the higher the welding current, which requires higher current welding. . Figure 1 shows conventional multi-electrode MIG welding. In the figure, 3 is a first electrode, and 4 is a second electrode, which allows shielding gas 10 to flow out from the outer peripheries of power supply chips 11, 12 and welding wires 1, 2 to create an arc between welding wires 1, 2 and base metal 5. This generates heat and performs welding using that heat. At this time, high current welding involves a strong plasma airflow, which blows the molten metal 6 directly below the arc in the direction of the arrow 7, and rapidly towards the already solidified bead 8, which is out of the reach of the arc heat. Because it is pushed away by
Compatibility with the base material 5 deteriorates, resulting in undercuts and humping beads. Further, a part of the molten metal directly under the arc rapidly solidifies at a portion 9, and since the molten metal directly under the arc is extremely reduced in the rapidly solidified portion 9, the solid surface of the base material is exposed directly under the arc. This solid surface has a fast cooling rate and poor wettability with molten metal, which causes fusion defects at the bottom of the bead. In addition, since the bottom of the bead is extremely narrow and elongated, and the top of the bead is also narrow and convex, problems such as hot cracking, undercutting of the bead, undercutting, and irregular beads occur. In order to deal with such problems from the viewpoint of welding means, for example, in Japanese Patent Application Laid-open No. 71744/1983, as a means of improving the quality and efficiency of DC gas shielded arc welding, the first electrode has a small diameter. A DC gas-shielded arc welding method using a large-diameter wire as the second electrode has been proposed. This method uses small-diameter MIG welding with the first electrode to form a shallow weld with a small current, and then uses preheating of the first electrode to achieve sufficient penetration using high current MIG welding with the second and subsequent electrodes. This is to ensure depth.
However, this method introduces the following new drawback. That is, since high current MIG welding is used for the second and subsequent electrodes, the arc becomes unstable due to magnetic blowing in high current MIG, and various defects such as poor fusion occur in welding. Although this welding method uses a large diameter wire to reduce the arc pinch force, it has the disadvantage that the arc is not rigid and is therefore extremely susceptible to magnetic blowing and deflection of the arc. . Furthermore, since preheating of the first electrode is utilized and penetration is achieved with a large current, the welding heat input to the base metal increases. Therefore, the SR of weld metal
Problems such as embrittlement occur. On the other hand, a general method that does not use such a large diameter wire
In the MIG welding method, relatively small diameter wire (0.8 to 2.0 mm
Since welding is performed using a small current using a welding device (φ), the amount of metal deposited per unit time is small, the penetration depth is shallow, and the bead shape is poor and various defects are likely to occur. In addition, as a welding method to deal with magnetic blow, welding using AC arc was published in Japanese Patent Application Laid-Open No. 56-168968.
This method is proposed in Japanese Patent Application Laid-Open No. 56-168969, but this method reduces magnetic blowing, but it also uses a thicker wire to create a softer arc and uses a cored wire. Because of this, the arc spreads and insufficient penetration tends to occur. In addition, because a large diameter wire is used, the amount of wire melted is small, and although a large current is used, there is no difference from the normal MIG welding method that uses a small diameter wire, and high efficiency can be achieved. I can't. (Objective of the Invention) The present invention provides a high-speed arc welding method that eliminates all the disadvantages and drawbacks of the conventional methods as described above. (Structure of the Invention) The present invention uses one power supply chip that can feed two welding wires with one feed motor in a gas shielded arc welding method that mainly uses inert gas such as Ar or He. The welding wires used above all have a diameter d in the range of 1.0 to 3.2 mmφ, and the gist is a high-speed arc welding method characterized by welding with a high current in the range of 1000 to 2500 A per feeding chip. be. Next, the present invention will be explained in detail based on the drawings. FIGS. 2 and 3 are explanatory diagrams showing embodiments of the high-speed arc welding method of the present invention, and both show longitudinal cross-sectional views in the weld line direction at the center of the weld. First, the second
In the figure, 3 is an electrode, 1-1 is a first welding wire,
1-2 is a second welding wire, 10 is a shielding gas,
11 is a power supply chip, and welding wires 1-1, 1
-2 are configured such that they can be fed by a single feeding motor (not shown). The first welding wire 1-1 has the effect of preheating the base metal 5 in the thickness direction while digging down the base metal 5, but the arc generated by the first welding wire 1-1 Molten metal 6' is blown in the direction of arrow 7.
The second welding wire 1-2 is the first welding wire 1-1.
An arc is generated in the molten pool 6' formed by the arc heat, and deflected in the advancing direction due to the interaction by the current of the first welding wire 1-1 of the same polarity, as shown by the arrow 7.
A reaction force against the backward flow of molten metal shown in FIG. 1 is generated to prevent the molten pool 6' generated by the first welding wire from being blown backward. As a result, good molten metal 8 is formed without generating welding defects such as poor fusion, and penetration that is even greater than that achieved by the first welding wire 1-1 is obtained. Furthermore, as shown in the embodiment example of FIG. 2, it is expected that the above effect will be further improved by using a center shield gas nozzle 13 and a power supply chip in which the protruding lengths of the first welding wire and the second welding wire are changed. Ru. That is, the arc length is changed by the voltage drop difference between the first welding wire 1-1 and the second welding wire 1-2 caused by the shielding gas discharged from the center shielding gas nozzle 13 and the inclination of the chip.
The molten metal 6' generated by the arc at -1 is indicated by the arrow 7.
Since the blowing in the direction is suppressed, there is no backward movement of the molten metal 6, and stable deep penetration and defect-free weld metal 8 in a good shape can be obtained. Furthermore, since the same power feeding chip is used, there is also the advantage that the wire spacing can be made closer and the device can be made more compact. In this embodiment, the present invention sets the diameter d of the two welding wires to 1.0 to 3.2 mmφ, and uses a large current of 1000 to 2500 A as the welding current to feed the wires at high speed under spray arc conditions. This makes it possible to obtain deep penetration by utilizing the hard arc characteristics that are narrowed by pinch force under a high current density arc. The arc stiffened by such pinch force does not generate magnetic blow unlike when using large diameter wire even under high current, and the stable arc shape method prevents welding defects such as insufficient penetration. Hard to occur. Furthermore, due to the high current and high current density, the amount of wire melted is extremely large. Therefore, the amount of welding is greater than when submerged arc welding or conventional MIG welding is performed with the same heat input, resulting in extremely high efficiency welding. The reason why the diameter d of the welding wire is set to 1.0 to 3.2 mmφ is that if the diameter of even one of the two wires exceeds 3.2 mmφ, the electrical resistance heat generated from the tip of the tip to the melted tip of the wire will It is much lower than the small diameter, so we cannot expect an increase in the amount of welding, and we cannot expect to increase the pinch force necessary to stabilize the arc, and the solidification position of the bead toe does not increase the welding speed. As the molten pool moves forward, the molten pool is pulled behind the bead, causing undercuts and humping beads. On the other hand, if even one of the two wires has a diameter of less than 1.0 mmφ,
The maximum allowable current value becomes low, making it difficult to increase the amount of wire welding. Welding current I (A) per power supply chip 1000
~2500A is because there are two wires per power supply chip, so even if the diameter of those wires is 3.2mm or less,
Even when a current of 2500A, which is twice the allowable value for one power supply chip and one wire, is applied, arc instability due to excessive pinch force does not occur, and there is no puckering phenomenon, resulting in bead irregularities, poor fusion, etc. Because it does not cause any defects,
This is because if it is less than 1000A, a sufficient current density cannot be obtained, resulting in a decrease in efficiency, and a sufficient pinch force cannot be obtained, resulting in a decrease in penetration. In this case, especially in FIG. 2, the small diameter wire is used as the first welding wire 1-1 as the second welding wire 1-1.
2, if the diameter of each wire is different from that of the large diameter wire, deep penetration can be obtained by the thinly narrowed hard arc with high current density of the first welding wire 1-1, and the molten metal 6' is 7, but by using a wire with a larger diameter than the first welding wire 1-1 for the second welding wire, the current density is lowered and the pinch force is reduced to spread the arc. The molten metal blown in the direction of the arrow is suppressed, resulting in a good bead shape. Although the case where the first welding wire 1-1 has a small diameter has been described here, the first welding wire 1-1 has a small diameter.
If a large diameter wire is used for -1, the penetration depth will be:
Although it is less than when using small diameter wire,
A weld with a rounded tip produces a wide bead. Therefore, which welding wire to use, a small-diameter wire or a large-diameter wire, may be selected depending on the purpose of use, such as whether sufficient deep penetration is required or whether a wide bead is obtained. Furthermore, instead of changing the wire diameter, the wire feeding speed ratio can also be changed. In this case, not only the same effect as when the wire diameter is different can be obtained, but also the composition of the weld metal can be adjusted. A desirable feeding ratio is 1:0.5-1.5. It goes without saying that both the diameter of the wire and the feeding ratio can be changed at the same time. Furthermore, the present invention can of course be applied to multi-electrode high-speed arc welding with two or more electrodes as shown in Fig. 3, but it is also possible to apply the present invention to a hard arc that is narrowed by a pinch force under a high current density arc. Because of this, it can be used without the need for special magnetic blowing treatment, which has been a problem with conventional multi-electrode magnetic blowing and resulting poor fusion, and since there is little mutual interference of arcs, it is possible to In other words, the distance between the first electrode 3 and the second electrode 4 can be set within 60 mm. Further, although the above figure shows only an example in which the welding wires are arranged in the welding progress direction via the same power supply chip, this is not necessarily the case; for example, when the groove width is wide, the weld metal If the purpose is to widen the range,
Although not shown, two
The desired purpose can be achieved by using an electrode equipped with a power supply chip with one or more wire feed holes for one or more of the electrodes or all of them as necessary. . Next, the effects of the present invention will be explained in more detail with reference to Examples. Example 1 A 60 kg class high tensile strength steel HT60 steel with a plate thickness of 32 mm was processed into the groove shape shown in Table 1 as a test material, and the high speed arc welding method of the present invention and the conventional gas shielded arc were used. 3 each of both welding methods (MIG welding)
The test was carried out using the electrode method under the conditions shown in Table 1. As is clear from the table, the method of the present invention dramatically improves the welding speed and number of passes compared to the MIG welding method. Furthermore, looking at the amount of penetration, in the case of the method of the present invention, the penetration is deep, so the root face of 7 mm shown in Table 1 can be used, but in the case of the conventional MIG welding method, the penetration is deep and the root face of 7 mm can be used. For related reasons, route face 3 shown in Table 1
Since it can only be used up to mm, the groove cross-sectional area becomes wide and welding efficiency also decreases. By feeding such small diameter wires at high speed from the same power supply chip and welding under high current density, weld metal without fusion defects and initial layer cracks was obtained with high efficiency. Example 2 The test material was X-65 steel, steel pipe outer diameter 1020 mm (40
inch), after tack welding a material with an inner thickness of 32 mm, using the method of the present invention.
Both SAW welding methods were performed using the two-electrode method under the welding conditions shown in Table 2. According to the method of the present invention, as is clear from the same table, the number of passes is significantly smaller than that of the SAW welding method.
Efficiency has been dramatically improved, including faster welding speeds. Furthermore, since the present invention uses deep penetration welding, the root face can be made large, and the groove cross-sectional area can therefore be made small, and the amount of melted wire can be extremely large even with low heat input, and as a result, the number of passes can be reduced. In addition to having many advantages such as , since one molten pool is formed by two welding wires, the composition can be controlled by using different types of wires, and good toughness can be easily obtained. Moreover, even if the root face was increased to 7 mm, no initial layer cracking was observed. Example 3 Both the method of the present invention and the SAW method were carried out under the welding conditions shown in Table 3 using a 2-electrode method using 2.5Ni steel, a 32 mm material, which is a low-temperature steel, as a test material. As is clear from the same table, according to the method of the present invention, the welding speed is faster than SAW, the number of passes is significantly smaller, and the efficiency is dramatically improved. Furthermore, since the wire diameter and feeding ratio can be changed, the nugget shape in the initial layer can be improved and the composition of the weld metal can be adjusted, and an extremely good bead shape can be obtained. Since the tip cross-sectional area can be reduced and deep penetration can be achieved, the root face can be made larger. Furthermore, even if the welding heat input is low, the amount of wire melting is extremely large, and as a result, the number of welded layers can be reduced. In this way, by changing the wire diameter and feeding ratio, weld metal with no initial layer cracking, sound, uniform and beautiful appearance was obtained with high efficiency.

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【table】 [Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the welding state of the conventional gas-shielded arc welding method, FIGS. 2 and 3 are explanatory diagrams showing embodiments of the high-speed arc welding method of the present invention, and FIG. 4 and FIG. FIG. 5 is a schematic diagram showing the dimensions and shape of the welding groove used in the example. 1, 2... welding wire, 1-1, 2-1... first welding wire, 1-2, 2-2... second welding wire,
3, 4...electrode, 5...base material, 6...molten metal, 6'...
Molten pool, 7... Direction of force applied to molten metal by arc, 8... Weld metal, 9... Rapid solidification section, 10... Inner shield gas, 11, 12... Power supply chip,
13...Center shield gas nozzle.

Claims (1)

[Claims] 1. In a gas-shielded arc welding method mainly using an inert gas such as Ar or He, one or more power supply chips capable of feeding two welding wires with one feed motor are used. , the welding wires all have a diameter d
Range of 1.0 to 3.2mmφ, 1000 per power supply chip
A high-speed arc welding method characterized by welding with high currents in the range ~2500A. 2. The high-speed arc welding method according to claim 1, wherein the welding wire diameters are different. 3. The high-speed arc welding method according to claim 1 or 2, characterized in that the feeding ratio of the welding wire is made variable.