JPH055582B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an upward single-sided welding method using a flux-cored wire, and more particularly to an upward single-sided welding method that can form a stable Uranami bead even with large groove fluctuations. It is something. [Prior Art] When welding the bottom of a ship in shipbuilding or constructing large blocks for bridges, welding points that must be performed in an upward position are often encountered. However, when welding in an upward position, burn-through of the weld metal tends to occur, often forcing welding to be interrupted. Therefore, there is a risk of welding defects occurring, and since welding (including repair welding) must be performed from the back side of the welded area in a downward position, welding work must be performed by entering the narrow area, resulting in extra steps and man-hours. will increase. Therefore, although various ideas and proposals have been made regarding methods for obtaining a good welded joint even in upward single-sided welding, there is still no known method that can be considered perfect in practical terms. One of the reasons for this is that the groove shape of the base material is not constant. In other words, if the gap between the base materials is too small, the underwave bead will not be formed, and on the other hand, if the gap is too large, a dent will occur in the underwave bead or a protrusion will occur on the front bead, which will lead to poor fusion in the next layer. The groove root width must be made as uniform as possible over the entire length of the weld line to avoid problems such as burn-through. For example, in JP-A-48-56543,
Attempts have been made to insert a thin steel plate into the gap with a width adjusted to cancel out variations in the groove width, but it is virtually impossible to form a thin steel plate that satisfies these conditions. It is possible. [Problems to be Solved by the Invention] In addition, when welding in a vertical or upward position, short arc welding using a solid wire is sometimes adopted as a welding method to prevent the surface bead from becoming convex. be. In short-circuit transition, stable transition is achieved by lowering the arc voltage and bringing the molten metal into contact.However, when using solid wire, the actual arc voltage is within a relatively narrow range of about 16 to 23V, and this range is If it comes off, the arc becomes unstable and it becomes difficult to perform continuous stable welding. In addition, the number of short circuits is relatively high, about 70 to 130 times, and when the number of short circuits decreases, the surface bead becomes convex or burns through. In this way, the range of welding conditions for short-circuit transition using solid wire is extremely narrow.
Furthermore, even in single-sided welding in an upward position, the limitation that the allowable gap range of the base metal is narrow (substantially 4±1 mm) is not relaxed. Therefore, even the above-mentioned improved method of performing short-circuit transition using a solid wire is not suitable for upward welding where the gap between the base materials is not constant, and is therefore impractical. Therefore, the present inventor has conducted various researches to provide a method that can stably perform continuous welding in an upward position even on a groove with gap fluctuations, and as a result has completed the present invention. Ivy. [Means for Solving the Problems] The method of the present invention that achieves the above object is based on
Using a flux-cored wire containing 10 to 30% flux, which is a sludge forming agent, based on the total weight of the wire, the receding angle of the wire is set in the range of 20 to 50 degrees, and the number of short circuits is set to 15 to 50 degrees. The gist is to perform upward welding at a rate of 50 times/second. [Function] The present invention is a method of upward welding using a flux-cored wire, and the filling ratio of flux to the weight of the wire is in the range of 10 to 30% (the meaning of % by weight, the same applies hereinafter). In other words, if the flux is less than 10%, the welding characteristics will be similar to that of solid wire, and the problems mentioned in the previous section will not be resolved, while if it exceeds 30%, feeding defects will occur due to insufficient wire strength. , the arc becomes unstable and the surface bead shape becomes poor. In addition, the slag forming agent in the flux is
50% or more, so that the slag can stably exhibit the effect of holding the surface bead. The slag forming agent used in the present invention includes those whose main purpose is to form slag, as well as those that remain as a result of slag, such as
Examples include TiO ₂ , ZrO ₂ , SiO ₂ , Al ₂ O ₃ , K ₂ O, Na ₂ O, and the like. The flux-cored wire described below is within the above range. FIG. 1 is an explanatory diagram of upward welding of the horizontal base material 1. At this time, the receding angle formed by the welding wire 4 and the perpendicular line H with respect to the welding progress direction (arrow B)
A ₁ must be set in the range of 20 to 50 degrees; if the receding angle A ₁ is less than 20 degrees, arc breakage is likely to occur; on the other hand, if it exceeds 50 degrees, arc condition monitoring and arc aiming are required. Position adjustment becomes difficult, which interferes with welding work and makes welding unstable. In the figure, reference numeral 2 represents weld metal, 3a and 3b slag, 5 a welding torch, 6 a weaver, and 7 a backing material, respectively. Flux-cored wire is usually used in a free flight state (granular transfer or atomized transfer), but by lowering the arc voltage, short-circuit transfer occurs, and the present invention actively utilizes this short-circuit transfer. be. Now, if the arc voltage is lowered under the condition of constant arc current, the number of short circuits will increase, but if the number of short circuits exceeds 50 times/second, there will be insufficient heat input and penetration into the base metal will be insufficient, making stable welding impossible. . On the other hand, if the number of short circuits is less than 15 times/second, the amount of heat input will be too large and the back bead will become concave, and in extreme cases, burn-through will occur. Weaving of the welding wire is carried out by oscillating the welding wire in the left and right direction of the groove as shown in Figure 4a, depending on the size of the gap between the base metals, but linear weaving as shown does not allow the molten metal to burn through. This tends to occur, making the front bead convex and the back bead concave. Therefore, in a preferred embodiment of the present invention, weaving is carried out in a two-dimensional plane including the left-right direction of the groove and the thickness direction of the base material, as shown in FIGS. As a result, there is less melting through of the molten metal, and the bead appearance is also good. [Example] Table 1 shows the welding results when base material SM41B (thickness 16 mm) was upwardly welded using wires with different flux filling ratios. The welding conditions are as follows. Welding conditions Current: 140-160A Voltage: 17-19V Speed: 6-9cm/min Bevel shape: Gap 6mm, 50° V-shaped bevel Shielding gas: Ar-20%CO ₂ Wire: YCW-2 Backing material :KL-3 Weaving conditions Amplitude W: 5 to 8 mm Amplitude D: 2 mm Flux composition: slag forming agent 60%, iron powder 10%, deoxidizing agent 30%

[Table] The results show that if the flux filling ratio is within the range of 10 to 30%, a welded part with good front bead shape and back bead shape can be obtained. Further, Table 2 shows the results of upward welding under the same welding conditions as above, when the flux filling ratio was 20% and the ratio of slag forming agent in the flux was varied. The composition of the flux other than the slag forming agent was 20% deoxidizing agent and the remainder was iron powder.

[Table] As a result, if the ratio of slag forming agent in the flux is 50% or more, the slag on the surface bead will be uniformly deposited.
The shape of the back bead can also be made good. Figure 3 is a graph showing the results of basic experiments, using solid wire (□ and ◇) and flux-cored wire (○ and △) as base material SM41B (thickness 12 mm).
mm) shows the relationship between the number of short circuits and arc voltage when downward welding is performed in a short-circuit transition state. The welding wire is
A wire with a diameter of 1.2 mm was used, the wire angle was set at right angles to the base material, and CO ₂ was used as the shielding gas. Welding current is 150A (□ mark), 130A (◇ mark), respectively.
160A (○ mark) and 140A (△ mark). As a result, when using a solid wire, if the arc voltage exceeds approximately 23V, the arc will become unstable and stable welding will not be possible, and if it falls below approximately 16V, there will be insufficient heat to melt the wire, causing arc breakage. It was hot. On the other hand, when flux-cored wire is used,
In the above current range, free writing occurs under high voltage conditions, generating large spatter and deteriorating workability. However, by lowering the voltage, stable short-circuit transition can be performed, and the number of short-circuits is 15 to 50. It was possible to obtain a good welded part at a speed of 1000 times per second. Figure 2 is a graph showing the relationship between the number of short circuits and the allowable gap range in single-sided upward welding, and the appropriate number of short circuits in solid wire is 60 to 130 times/
The tolerance is relatively wide, about seconds, but the allowable gap range between the base materials is very narrow, about 4±1 mm. On the other hand, with flux-cored wire, the allowable range for the number of short circuits is narrower at 15 to 50 times/sec, but the allowable gap range is wider at 3 to 12 mm, making it more adaptable to large gap fluctuations. I understand. If the gap is less than 3 mm, the back bead may not come out, or even if it does come out, it will be concave. If the gap is less than 1 mm, poor fusion will occur, and if the gap exceeds 12 mm, the slag will not have a bead retention effect against the increase in heat input. As expectations are lost, the top bead becomes convex, and as the gap widens further, burn-through occurs. A preferred weaving pattern of the present invention is the fourth weaving pattern.
As illustrated in Figures b and c, welding torch 5
Since the receding angle A ₁ as shown in Fig. 1 is given to ), the inclination angle A ₂ (90−A ₁ ) as shown in the same figure is given. If this inclination angle A ₂ is equivalent to the inclination angle A ₃ of the crater, stable welding is possible because there is no change in the wire protrusion length during weaving.In practice, this inclination angle A ₂ should be set at 10 to 60. It is preferable to set it as degree. Further, the amplitude W in the left-right direction of the weaving groove [Fig. 4b] is preferably in the range from base material gap +4 mm to base material gap -2 mm, and the amplitude W
If it is too small, the weld metal will not bridge between the gaps, resulting in insufficient penetration into the surface of the base metal, making it impossible to weld; on the other hand, if it is too large, it will cause instability of the arc. FIG. 5 is a graph showing the relationship between the thickness direction amplitude D of weaving and the bead shape. as base material
SM41B, flux-cored wire YCW-24 with the above components as welding wire, solid flux type KL-3 as backing material, as shielding gas
Upward welding was performed using CO ₂ and a setback angle of 40 degrees. The groove was a 50° V-shaped groove with a gap of 6 mm. The ○ mark in the figure indicates the back bead extra height.
The △ mark indicates the height of the center of the front bead. As a result, when the amplitude D is 0 mm, it is not possible to prevent the surface bead from becoming convex even if the current and voltage are lowered to reduce heat input, or the movement of the wire is stopped at both ends of the weaving to improve bead conformity. On the other hand, if the amplitude D is made larger than 6 mm, the arc becomes unstable because the throat thickness of the initial welding layer is exceeded, and the back bead becomes concave. Therefore, the appropriate range of amplitude D is
It is preferable to set it within 0.5 to 6 mm. For a power supply with constant voltage characteristics that allows the number of short circuits to be 15 to 50 times/second, it is better to use a transistor than a thyristor. This is because the thyristor type can only adjust the average voltage when a short circuit and an arc occurs, whereas the transistor type can also adjust the voltage when an arc occurs, making it possible to increase the number of short circuits. There are no particular restrictions on the backing material, but it is convenient to use the normally used backing material for carbon dioxide gas welding, and in terms of materials, either ceramic type or flux molded type may be used. , there is no need to prepare anything special for upward welding. Furthermore, there are no restrictions on shielding gas,
For example, when CO ₂ or Ar-CO ₂ is used, optimal welding workability can be obtained when the flux is filled with 50% or more of TiO ₂ as a slag material. Table 3 shows the results of observing the back and front bead shapes when upward welding was performed under various welding conditions.
In experiment numbers 1 to 16, SM50A (thickness 16 mm) was used as the base material.
mm) Ar-20% CO ₂ as shielding gas, KL-3 as backing material, YCW- as solid wire
2. Using YFW-34 as the flux-cored wire, set the receding angle of 30 to 30 to the base material with a 50° V-shaped groove.
Upward welding was performed at 40 degrees. Also experiment number 17-22
Shows an example where upward welding is performed by changing the base material, wire, etc.

[Table] Experiment numbers 1 to 5 are conventional examples using solid wire, and it is not possible to obtain a good bead shape unless the number of short circuits is within the range of 70 to 130 times/second.
A good bead shape cannot be obtained unless the gap is about 4 mm. Experiments Nos. 6 to 8 are comparative examples for the present invention. When the gap is too narrow (Experiment No. 6), the back bead becomes concave, and when the number of short circuits is small (Experiment No. 7), the arc becomes unstable. When the number of short circuits was high (Experiment No. 8), the back bead became concave and the heat input was insufficient, resulting in poor fusion. Experiment numbers 9 to 14 are examples of the present invention, and showed good bead shape and welding work performance. Experiments Nos. 15 and 16 are comparative examples in which weaving conditions were changed; when the amplitude D (amplitude in the thickness direction of the base material) is too high (Experiment No. 15), the arc becomes unstable and the bead shape is poor. On the other hand, when the amplitude D was 0 (experiment number 16), the top bead had a convex shape even if the stopping time was set at both ends of the amplitude W. Experiment number 17 shows an example in which the base material was changed to 60HT and the flux-cored wire was also changed to 60HT, and experiment numbers 18 and 19 show examples in which the groove angle was changed.
Good bead shapes were obtained in all cases. Experiment number 20 shows an example in which the shielding gas was changed to CO ₂ .
Experiment No. 21 shows an example in which the backing material was changed to FBB-3, and a good bead shape was obtained in these examples as well. In experiment number 22, the slag forming agent in the flux was BaF ₂ ,
In this example, a 1.8 mm diameter self-shielded arc welding wire was used without gas shielding, instead of using a fluoride-based wire such as LiF, and even in this case, a good bead shape could be obtained. [Effects of the invention] According to the present invention, it is now possible to perform stable and continuous upward welding even for base materials with large gap fluctuations, and automation of upward single-sided welding is promoted, which can be used for joints of ship bottom blocks, bridges, etc. It has become possible to demonstrate good welding workability even in large block joints.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of upward welding, Fig. 2 is a graph showing the relationship between the number of short circuits and allowable gap, Fig. 3 is a graph showing the relationship between arc voltage and the number of short circuits, and Figs. 4 a- c is an explanatory diagram showing the locus of movement of weaving, and FIG. 5 is a graph showing the relationship between the amplitude in the plate thickness direction and the bead shape.

Claims (1)

[Claims] 1. Using a flux-cored wire containing 10 to 30% of the total weight of the wire, 50% by weight or more of flux is a slag forming agent, and the receding angle of the wire is 20 to 30% by weight.
While setting the range of 50 degrees, the number of short circuits is 15 to 50 times/
An upward single-sided welding method characterized by upward welding in a range of seconds. 2. The upward single-sided welding method according to claim 1, in which the flux-cored wire is weaved and welded within a two-dimensional plane including the left-right direction of the groove and the thickness direction of the base material.