JP2672171B2 - Enclosed arc welding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an enclosed arc welding method for enclosing welding a rod-shaped material to be welded such as a reinforcing bar, and particularly to supplying a shielding gas from the outside using a flux-cored wire. The present invention relates to an enclosed arc welding method by self-shielded arc welding in which welding is performed without welding.

[Prior Art] In the reinforcement arc welding method for reinforcing bars, two reinforcing bars to be joined are arranged with an appropriate groove interval, and the outer peripheral portion of the area between the grooves is covered with a copper wire having an appropriate shape. Surround with gold. Then, a welding electrode such as a covered arc welding rod is inserted into the groove space formed by the groove surface of the reinforcing bar and the copper metal and the arc formation is started from the bottom thereof. Then, the arc is used to melt the welding rod, melt the groove surface of the reinforcing bar, and fill the groove space with the weld metal while excluding generated slag outside the groove to complete the joint. This enclosed arc welding method is extremely excellent as a method of jointing a reinforcing bar to narrow areas.

On the other hand, in the self-shielded arc welding method, the welded portion is shielded by the slag generated by using the flux-cored wire, and the reinforcing bar is welded without supplying the shield gas from the outside. The flux-cored wire has a steel sheath filled with a flux composed of a gas generating agent, a slag forming agent, a deoxidizing agent, a denitrifying agent, and the like for shielding the atmosphere. This self-shielded arc welding method has advantages in that the welding device is simple, easy to carry, and hardly affected by wind, and thus is suitable for outdoor welding.

Reinforcing bar joint work is generally done outdoors,
Especially in high-rise construction work, it is necessary to perform welding in a strong wind environment where the wind speed exceeds 10 m / sec.
Therefore, in the joint construction method using the carbon dioxide arc welding method, it is necessary to provide a large-scale windbreak means, and therefore the work is complicated and the workability is poor.

On the other hand, the self-shielded arc welding method has excellent wind resistance and does not require a shielding gas. In addition to reducing the gas cost, the construction procedure is simplified and the construction cost is significantly reduced. be able to. In addition, this self-shielded arc welding method is excellent in efficiency, so that welding time can be shortened compared to manual welding, and in addition to shortening the total work time compared to carbon dioxide welding method. Can be planned. Furthermore, in addition to being excellent in joint performance, the present welding method has an advantage that a welding jig is not necessary since it is sufficient to simply lock the material at the groove with an adhesive tape or the like. Therefore, applying the self-shielding arc welding method, which has excellent wind resistance, to the enclosed arc welding method, which is suitable for fitting joints in narrow spaces, is basically the same as in high-rise construction work. It can be said to be a means that enables high-efficiency and high-quality welding work in places where the environment is narrow and the influence of wind is strong.

[Problems to be Solved by the Invention] However, even if the conventional self-shielded arc welding method is simply applied to the enclosed arc welding method, the intended purpose cannot be achieved.

In other words, even if the self-shielded arc welding flux-cored wire is inserted into the groove space surrounded by the pair of reinforcing bars and the copper plate to melt the wire and the groove surface of the reinforcing bar, The generated slag is caught in the molten metal, and due to the presence of the slag, fusion failure is likely to occur in the joint portion.

The present invention has been made in view of such problems, it is possible to prevent the inclusion of slag, to avoid the occurrence of poor fusion of the joint portion, the advantages of both closed arm welding and self-shield arc welding It is an object of the present invention to provide an enclosed arc welding method capable of sufficiently exhibiting the above.

[Means for Solving the Problems] The method for enclosing arc welding according to the present invention is to provide a pair of materials to be welded, each of which has a rod shape and whose joint surface is substantially perpendicular to its axial direction, between the joint surfaces. This material is made of a refractory material with a softening point of 1100 ° C or higher, which is placed with a predetermined groove space.
It is placed so as to contact the side surface of one welded material and to surround a part of the groove space with a predetermined gap provided between the welded material and the other welded material. In the enclosed arc welding method of arc welding between the joint surfaces using, the flux-cored wire is a metal fluoride: 20 to 30
% By weight, metal carbonate: 2 to 10% by weight, Al: 8 to 15% by weight, Mg: 5 to 10% by weight, Mn: 0.5 to 8% by weight, and iron content: 35 to 60% by weight. Fluoride / iron ratio
Flux adjusted to 0.4 to 0.7 is applied to the steel shell to 17 to
It is characterized by being filled with a flux rate of 23% by weight.

In addition, the joint surface is substantially perpendicular to the axial direction of the rod-shaped material to be welded, when welding is carried out by the method of the present invention, an inclination that gives a restriction to the attachment position of the material and the insertion position of the molten material. In other words, it means that there is no problem in terms of construction without considering the directionality of welding.

Further, when this material is overlapped on the side surface of the material to be welded, it is not necessary to bring the material into contact with the material to be welded on the entire surface of the overlapped area, as long as it is in contact with part of the area. Good.

[Operation] In the present invention, the material to be welded is disposed with a predetermined groove space provided between the joint surfaces, and the material is disposed in contact with the side surface of the material to be welded. This material surrounds a part of the groove space and is arranged with a predetermined gap provided between the material and the material to be welded.
Then, for example, a bridging portion is formed by filling the weld metal from one of the materials to be welded in the vicinity of the material.

In this case, since this material is arranged on the far side of the groove,
At the start of welding, the ends of the joint surface of the materials to be welded do not burn out. In addition, a bridging portion can be easily provided between the joining surfaces of the materials to be welded by using this material.

Further, in the present invention, since self-shielded arc welding is performed using a flux-cored wire in which a flux having a predetermined composition is filled in a steel shell at a predetermined weight ratio, the generated slag has excellent fluidity. Therefore, since the generated slag floats upward and is discharged from the gap formed between this material and the material to be welded, the slag is not entrained and defects such as poor fusion occur in the joint portion. It never happens. Further, when self-shielded arc welding using a flux-cored wire of the above composition, the penetration in the groove surface of the material to be welded is large, a high-strength joint is obtained, and the arc is stable, so welding work It has excellent properties.

Furthermore, since this material is formed of a refractory material with a softening point of 1100 ° C or higher (Zegel cone SK01a or higher), hold the molten metal through the slag even if it comes in contact with molten metal melted by arc heat. It is possible to improve the soundness of the welding start portion where defects are most likely to occur. Therefore, since this material can be removed after welding, the appearance and properties of the welded portion can be easily visually observed, and the presence or absence of defects can also be determined. Moreover,
The contact surface of the weld that comes into contact with the refractory material is smooth and a beautiful weld can be obtained.

INDUSTRIAL APPLICABILITY The present invention can be applied to downward posture welding of reinforcing bars arranged horizontally. Moreover, in this case, since the slag generated during welding always floats above the weld metal,
This material may be installed so as to straddle the material to be welded, and the handling and welding operations are even simpler than in the case of vertical bars.

Next, the reason for limiting the composition of the flux component of the self-shielded arc welding flux-cored wire used in the present invention will be described.

Metal Fluoride Metal fluoride is both a shielding agent and a major slag-making agent. When the amount of metal fluoride is small, the workability is improved, but when the amount is too small, the shield becomes insufficient and defects such as pits and blow holes occur. Therefore, it is necessary to add the metal fluoride at least 20% by weight or more.

On the other hand, as the amount of metal fluoride added increases, the shielding effect improves, but the amount of spatter and fume increases, and welding workability deteriorates. In particular, when the content of metal fluoride exceeds 30% by weight, the melting point of the slag decreases, and the bead easily falls down in a welding position such as a horizontal position, which causes cold wrap.

Therefore, the amount of metal fluoride added is in the range of 20 to 30% by weight. In consideration of the metal shielding property and workability, the optimum addition amount of the metal fluoride is 22 to 26% by weight.

Although various types of metal fluorides can be used, fluorite (Ca
It is most desirable to use F _2). When a part of the amount of fluorite is replaced by LiF, K ₂ SiF ₆ , NaF, BaF, or the like, droplet transfer becomes smooth, and spraying can be improved. However, if the replacement amount by LiF or the like is excessive, the slag peeling property is impaired, and the spatter amount increases. Therefore, the replacement amount is preferably set to 10% by weight or less.

Metal carbonate Metal carbonate is a component that makes slag removability and slag viscosity favorable for welding work. Therefore, when the metal carbonate is added to the flux, a glossy bead surface is obtained, the dripping of the bead is improved, and a uniform and smooth bead shape is obtained. Furthermore, the metal carbonate also acts as a shield agent. In order to obtain such an effect, it is necessary to add the metal carbonate at least 2% by weight or more. If the content of the metal carbonate is less than 2% by weight, the slag tends to seize and the viscosity of the slag decreases, so that a uniform and smooth bead shape cannot be obtained.
The greater the amount of metal carbonate added, the better the slag removability, bead shape and shielding properties are improved. However, if it is added in excess of 10% by weight, the decomposition gas (CO ₂ ) generated at the time of welding will result in extremely large particles. Spatter occurs, which is not preferable in terms of workability.

Therefore, the addition amount of the metal carbonate is in the range of 2 to 10% by weight. In order to surely obtain the above effect, it is desirable to control the addition amount within a range as narrow as possible, and the optimum addition amount of the metal carbonate is 4 to 7% by weight.

The metal carbonates include, but are CaCO ₃ is the most suitable, in addition to CaCO _3, or can also be used BaCO ₃ or SrCO _3, etc. out of the CaCO _3.

Al Al acts as a deoxidizing agent and has an effect of fixing N invading into the deposited metal and preventing pits and blow holes. However, when the Al content is less than 8% by weight, pits and blowholes are generated, and a sound weld cannot be obtained. On the other hand, if the Al content exceeds 15% by weight, the amount of Al remaining in the deposited metal increases, so that the crystal grains become large and the ductility is remarkably impaired.

Therefore, the addition amount of Al is set in the range of 8 to 15% by weight.
The Al raw material is preferably metal Al or an alloy such as Fe-Al and Al-Mg.

Mg Mg forms a vapor to shield the weld and also acts as a deoxidizer. However, when the Mg content is less than 5% by weight, it is difficult to suppress pits and blow holes.
On the other hand, if the content of Mg exceeds 10% by weight, the addition becomes excessive, the viscosity of the slag is reduced, and the dripping of the bead is promoted. Further, the amount of fume is also undesirably increased significantly.

Therefore, the added amount of Mg is in the range of 5 to 10% by weight.
As the Mg raw material, Mg powder or Al-Mg, Si-Mg and
It is preferable to use an alloy such as Ni-Mg.

Mn Mn is added as a deoxidizing agent, and additionally has an effect of giving a proper tensile strength to the deposited metal. But,
If the Mn content is less than 0.5% by weight, sufficient tensile strength cannot be obtained. On the other hand, if the Mn content exceeds 8% by weight, the tensile strength becomes excessive and the bending ductility is significantly impaired.

Therefore, the added amount of Mn is set in the range of 0.5 to 8% by weight. As the Mn raw material, Mn powder or Fe-Mn and Fe-
It is preferable to use an alloy such as Si-Mn.

Iron Powder Since iron powder increases the fluidity of flux, it has the effect of stabilizing the flux rate. When iron powder is present in the wire, the iron powder has a function of conducting heat and a function of accelerating the melting of fluoride. Therefore, iron powder has the effect of stabilizing the arc and stabilizing the molten state. However, when the iron powder content is less than 35% by weight, formation of flux columns is observed, which is not preferable in terms of suppressing welding defects. In addition, there is a problem that spatter increases. On the other hand, if the iron powder content is more than 60% by weight, metal fluorides and the like are relatively reduced, and problems such as a decrease in shielding properties occur, which is not preferable.

Therefore, the amount of iron powder added is in the range of 35 to 60% by weight. The bulk specific gravity of the iron powder is desirably 2.5 to 3.7, and within this range, there is no restriction on the contained components.

Metal fluoride / iron powder ratio The present inventors investigated the relationship between the amount of metal fluoride, which is the main slag-making agent, and the melting phenomenon, and found that the ratio of metal fluoride / iron was good or bad in the state of arc generation. I found that there is a close relationship. An arc was formed stably when the metal fluoride / iron powder ratio was in the range of 0.4 to 0.7.

That is, the ratio of metal fluoride / iron powder is plotted on the horizontal axis in FIG.
The vertical axis indicates the amount of spatter and the total amount of N in the deposited metal, and as an example of the relationship between the ratio and the amount of spatter and the total amount of N in the deposited metal, as shown in FIG. It is spoiled, and the amount of spatter generated increases. On the other hand, this ratio
If it is less than 0.4, shielding failure or the like occurs, the total N content in the deposited metal increases, and the welding characteristics deteriorate. Therefore, the ratio is in the range of 0.4 to 0.7.

With respect to the flux, the desired welding performance can be obtained with the above composition. However, if necessary, the following components can be added to the flux to produce a flux-cored wire.

C C has the effect of improving toughness, so it can be added in the range of 0.2 to 0.4 wt% based on the total weight of the wire. If the C content is less than 0.2% by weight, the effect of improving the toughness is small, and if it exceeds 0.4% by weight, the tensile strength of the deposited metal becomes excessive and conversely the toughness decreases, which is not preferable.

Ni Ni, like C, has the effect of improving toughness, so
It can be added in the range of 0.2 to 3% by weight based on the total weight of the wire. When the Ni content is less than 0.2% by weight, this effect of adding Ni cannot be obtained, and when it exceeds 3% by weight, the tensile strength of the deposited metal becomes excessive and the toughness is impaired, which is not preferable.

Since the water in the wire has a function of improving the shielding property by synergistic action with the metal fluoride, the water content in the wire is preferably regulated to 400 to 2000 ppm. However, when the water content is less than 400 ppm, the effect is small,
If it exceeds 00 ppm, problems tend to occur in terms of pit resistance and crack resistance.

Flux rate The flux rate in the wire configuration (the weight of the flux relative to the total weight of the wire) is 17 to 23% by weight. If the flux rate is less than 17% by weight, the required amount of slag cannot be secured, thereby deteriorating workability. On the other hand, if the flux ratio exceeds 23% by weight, breakage is likely to occur during drawing in the manufacturing process of the flux-cored wire, and the manufacturing process becomes inefficient. Therefore, the flux rate needs to be 17 to 23% by weight.

The wire used in the present invention is one in which a flux mixed with the above components is filled in a steel outer shell,
Regarding the outer skin component, it is desirable to use a steel material having a Si content of 1% or less and a total N content of 100 ppm or less in order to achieve the performance of the present invention. By suppressing the above components in the outer skin, the arc characteristics are improved, and the amount of spatters generated can be further reduced. Therefore, the total amount of N is preferably 100 ppm or less in order to prevent the generation of pits and blow holes.

Further, the self-shielded arc welding flux-cored wire used in the present invention can be manufactured by the same manufacturing method as a normal flux-cored wire.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings. 2 (a) to 2 (e) are schematic diagrams showing an enclosed arc welding method according to the embodiment of the present invention in the order of steps, and FIG. 3 is a sectional view taken along line II-II of FIG. 2 (a). .

The upper reinforcing bar 11 and the lower reinforcing bar 12 have a joint surface substantially perpendicular to the axial direction. Therefore, when the reinforcing bars 11 and 12 are arranged vertically with their axial directions aligned, both joint surfaces Face substantially horizontally and in parallel. The copper metal plate 14 has a U-shaped horizontal cross section, and is arranged so as to hold the reinforcing bars 11 and 12 around a front space 15 formed between the upper reinforcing bar 11 and the lower reinforcing bar 12. Both rebars 11 and 12 are gripped by a pair of clampers (not shown) fixed to a copper abutment 14 so that their axes coincide at their opposite ends. 14 and a damper are disposed so as to face up and down.

There is a recess 1 in the copper metal 14 behind the groove 15 between the reinforcing bars 11 and 12.
6 is formed, and the material 13 is disposed in the recess 16 in contact with the side peripheral surface on the back side of the lower reinforcing bar 12. This material 13
Is fixed by being pressed against the lower reinforcing bar 12 from behind by a bolt 17 that horizontally penetrates the copper plate 14.

The material 13 is preferably a non-metal refractory material such as cordierite or forsterite.

After arranging the upper rebar 11, the lower rebar 12, the bar 13 and the copper plate 14 in this way, as shown in FIG. It is inserted into the groove space 15, and welding is started from the vicinity of the material 13 (the inner side of the open space 15). In other words, first, the material
Start the arc 5 to 6mm before 13
Immediately, the arc is moved to the corner portion between the joint surface of the lower reinforcing bar 12 and the material 13, and the semi-weaving is carried out while shortening the arc so that the molten metal has a rise. In this case, a self-shielded arc welding flux cored wire having the above-described composition is used as the welding wire 18.

Then, as shown in FIG. 2 (b), the molten metal 20 is laid on the joint surface of the lower reinforcing bar 12 using the base material 13.
In this case, the generated slag 21 floats on the molten metal 20. Then, the joint surface (upper groove) of the upper reinforcing bar 11 and the molten metal
When the distance from 20 becomes 2 to 3 mm, the semi-weaving is stopped, the arc is stopped, and the corner of the upper groove is melted and bridged.

After the upper rebar 11 and the lower rebar 12 are bridged, FIG. 2 (c)
As shown in Fig. 5, while performing semi-weaving, the generated slag is discharged to the outside of the groove using the gap between the upper reinforcing bar 11 and the bar 13, and the wires 18 are alternately turned upward and downward. Ensure the penetration between the groove side and the lower groove side. Thus, as shown in FIG. 2 (d) and FIG. 2 (e),
The lamination of the molten metal 20 is continued up to the forefront of the groove. Next, the arc is stopped, and after the molten metal 20 is cooled and solidified, the clamper is removed, the material 13 is separated from the welded portion, and the welding is completed.

In the method of the present embodiment, since the wire having the above-described composition is used as the self-shielded arc welding flux cored wire, the generated slag has excellent fluidity, and is easily discharged from the deposited metal in the groove space. You. Therefore,
Defects such as slag entrainment and poor fusion between the weld metal and the reinforcing bar are suppressed.

Further, a small piece of the refractory material 13 is brought into contact with the lower rebar 12 side in the inner part of the copper plate 14 to enable bridging of the weld metal 20 between the upper rebar 11 and the lower rebar 12. Then, an I-shaped groove formed at the joint surface between the upper reinforcing bar 11 and the lower reinforcing bar 12 is arc-welded in a horizontal direction. If welding is performed without using the material 13, it is difficult to form an appropriate bridging between the upper reinforcing bar 11 and the lower reinforcing bar 12 in the inner part of the I-shaped groove. Because of the welding posture, the molten metal 20 only spreads on the groove surface (joint surface) of the lower rebar 12 and does not easily reach the upper rebar 11. As described above, the small material 13 has a function of accumulating the molten metal 20 at the back of the groove and promoting bridging between the upper and lower rebars.

Further, since the material 13 is formed of a refractory material having a softening point of 1100 ° C. or higher, it does not completely melt even when it comes into contact with a metal melted by receiving arc heat, and can hold a weld metal. . After the welding is completed, the material 13 can be removed from the welded portion, and the appearance and properties of the exposed welded portion can be visually observed to determine the presence or absence of defects. Further, if a vitreous refractory is used as the material 13, a glossy and smooth surface can be obtained, and a beautiful welded portion can be obtained.

As described above, in order to form the bridging using the bar 13, the both ends of the lower bar 12 of the bar 13 in the circumferential direction are rebar.
The central angle θ with the axis of 12 must be 30 ° or more.

The distance d (mm) between the upper reinforcing bar 11 and the material 13 is 2 to
D / 2 mm is preferable. However, D (mm) is upper rebar 1
This is the distance between 1 and the lower reinforcing bar 12. If d is less than 2 mm, the escape of the slag 21 becomes poor, and the slag is likely to be involved. Further, in order to discharge the slag 21, high skill and strict monitoring of welding conditions are required. On the other hand, d is D /
When it exceeds 2, it becomes difficult to form a bridging portion by the molten metal 20. Therefore, it is difficult to complete the joint.

Next, a description will be given of a result of actually performing the vertical welding of the I groove by the method of the embodiment of the present invention.

Used reinforcing bar; SD35, SD40 (JIS) Reinforcing bar shape; JIS G3112 (Steel bar for reinforced concrete) Reinforcing bar diameter; D21 and D38 welding wire; In both cases of SD35 and SD40, the diameter is 2.0 mm and described in Table 3 below. Flux composition is used. Groove spacing: 10 mm and 14 mm for D22, 12 mm and 16 mm for D38; Cordierite with a width of 25 mm, a length of 20 mm and a thickness of 10 mm (softening point 1300 to 1400 ℃) Welding current; 290 to 310A for D38, 290 to 310A for D22.

Table 1 below shows the properties of the welds obtained when welding was performed under these welding conditions.

 All have sufficient strength and ductility.

Table 2 below shows a comparison of the welding results between the case of welding by the method of the embodiment of the present invention and the case of welding by the conventional method using a rebar having a diameter of D41.

As is clear from Table 2, according to the method of the present embodiment, the required time is approximately halved as compared with the conventional method, and the efficiency is extremely high.

In addition, as described above, since the joint surface can be horizontal-enclosed and arc welded, it is not necessary to assemble the rebar in consideration of its direction when pre-assembling the rebar,
Therefore, it is possible to quickly pre-assemble, and the merit of the pre-assembly method can be fully utilized. Also, since it is only necessary to form a joint surface substantially perpendicular to the axial direction of the reinforcing bar,
It is easy to form a groove shape.

Next, the results of conducting the enclosed arc welding using the flux composition wire shown in Table 3 below and examining the workability and mechanical properties thereof will be described.

As shown in Table 3, both workability and mechanical properties were excellent.

[Effects of the Invention] According to the present invention, the self-shielding arc welding method is combined with the enclosed arc welding method, and the flux composition and flux rate of the flux-cored wire to be used are set to predetermined values. The fluidity is high, and the occurrence of slag entrainment and poor fusion can be avoided. Therefore, the advantages of the enclosed arc welding and the advantages of the self-shielded arc welding can be effectively exerted, and the method of the present invention is extremely useful for the joint construction of the reinforcing bars of reinforced concrete structures such as high-rise buildings.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the metal fluoride / iron powder ratio, the amount of sputtering, and the total amount of N in the deposited metal, and FIGS. 2 (a) to 2 (e) are enclosures according to the embodiment of the present invention. Schematic diagram showing the arc welding method in the order of steps, FIG. 3 is II of FIG. 2 (a)
It is sectional drawing by the I-III line. 11,12; Reinforcing bar, 13,22; Material, 14; Copper metal, 15; Groove space, 2
3; recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-258489 (JP, A) JP-A-3-118993 (JP, A) JP-A 58-148095 (JP, A) JP-A 61- 169196 (JP, A) Japanese Patent Publication 7-108458 (JP, B2) Patent 2592951 (JP, B2) Patent 2530899 (JP, B2) Patent 2519308 (JP, B2)

Claims (3)

(57) [Claims] 1. A pair of materials to be welded, which are rod-shaped and whose joint surface is substantially perpendicular to the axial direction, are arranged with a predetermined groove space between the joint surfaces, and the temperature is 1100 ° C. or higher. This material consisting of a refractory material having a softening point is arranged so as to surround a part of the groove space, and then an enclosed arc for arc welding between the joining surfaces using a self-shielded arc welding flux-cored wire In the welding method, the flux-cored wire, metal fluoride: 20 to 30 wt%, metal carbonate: 2 to 10 wt%, Al: 8 to 15 wt%,
Mg: 5 to 10% by weight, Mn: 0.5 to 8% by weight, and iron content: 35
Enclosed in a steel shell with a flux ratio of 17 to 23% by weight, containing a metal fluoride / iron ratio of 0.4 to 0.7. Arc welding method. 2. The method according to claim 1, wherein the flux of the flux-cored wire contains 0.2 to 0.4% by weight of C based on the total weight of the wire. 3. The enclosed arc welding method according to claim 1, wherein the flux of the flux-cored wire contains 0.2 to 3.0% by weight of Ni with respect to the total weight of the wire.