KR102126667B1 - Method for vertical narrow gas shield arc welding - Google Patents

Abstract

As a predetermined improvement condition, in a vertical narrow narrow gas shield arc welding method in which two thick steel sheets having a thickness of 10 mm or more are joined by one-layer welding or multi-layer welding using weaving, a predetermined amount of REM is contained. Using a welding wire and using a welding torch having a bent portion and a tip end defined by the bent portion, weaving of the first layer welding is performed, and at that time, when weaving the improved surface of the thick steel material , Under certain conditions, the leading end of the welding torch is then rocked toward the improved surface of the steel.

Description

Method for vertical narrow gas shield arc welding

The present invention relates to a narrow gas shield arc welding method, and more particularly, to a vertical narrow gas shield arc welding method applicable to butt welding of two thick steel materials.

Here, "narrow improvement" means that the improvement angle is 20 degrees or less and the improvement gap is 20 mm or less.

The gas shield arc welding used for welding welding of steel is generally a consumable electrode type in which a gas of CO ₂ alone or a mixed gas of Ar and CO ₂ is used for shielding the molten portion. Such gas shielded arc welding is widely used in the fields of manufacturing automobiles, construction, bridges, and electrical equipment.

However, in recent years, with the enlargement and thickening of the steel structure, the welding amount in welding in the manufacturing process, especially in the butt welding of steel materials increases, and furthermore, it takes a lot of time for welding construction, which increases the construction cost. Effect.

As a method of improving the above-described problem, it is possible to consider application of a narrow-line gas shielded arc welding in which multi-layer welding is performed by arc welding to improve a small gap with respect to the plate thickness. This narrower gas shielded arc welding has a smaller welding amount compared to a conventional gas shielded arc welding, so that it is possible to achieve high efficiency and energy saving of welding and further reduce construction costs.

On the other hand, electroslag welding is generally applied to high-efficiency welding in the vertical direction, but one-pass high-input heat welding is the basis, and in welding with a plate thickness exceeding 60 mm, excessive heat input may cause a drop in toughness. Is becoming. In addition, there is a limitation in plate thickness for one-pass welding, and it is currently the situation that welding with a plate thickness exceeding 65 mm has not been established.

For this reason, it is desired to develop a high-quality and high-efficiency welding method in which a narrow gas shield arc welding is applied to vertical welding.

As a welding method in which such narrow gas shield arc welding is applied to vertical welding, for example, Patent Document 1 discloses a double-sided multi-layer welding method targeting a double-sided U-shaped joint. In this welding method, lamination welding is performed by TIG welding using an inert gas, and the occurrence of slag and sputtering is suppressed by using the inert gas, thereby preventing lamination defects.

However, the non-consumable electrode type TIG welding greatly reduces the efficiency of the welding method itself in comparison with MAG welding or CO ₂ welding using a steel wire as a consumable electrode.

In addition, Patent Document 2 discloses a narrow vertical welding method in which weaving of a welding torch is performed to suppress sputtering and fusion defects.

However, in this welding method, since the weaving direction of the welding torch is not the improved depth direction, but the surface direction of the steel sheet, it is necessary to weave the welding torch before the molten metal is stretched, resulting in a welding current of about 150 A. It is necessary to set the low current of and suppress the amount of welding per one pass (heat input amount).

Therefore, when this welding method is applied to welding of a thick steel material having a large plate thickness, a small amount of multipath lamination welding is performed, and there are many lamination defects such as poor penetration, and welding efficiency is greatly reduced.

In addition, in Patent Document 3, as in Patent Document 2, a vertical welding method is disclosed in which weaving of a welding torch is performed to suppress fusion defects.

Although the surface angle (improvement angle) disclosed herein is wide from 26.3 to 52°, weaving of the welding torch here is also performed for the improved depth direction. For this reason, in the vertical welding method of patent document 3, it is possible to take a comparatively large amount of welding per pass.

However, since the amount of weaving in the improved depth direction is small and the composition of the weld metal and the welding wire is not considered, it is necessary to suppress the amount of welding per one pass (heat input amount), and the welding depth per pass is 10 mm. It becomes shallow.

Therefore, even when this welding method is applied to the welding of thick steel materials having a large plate thickness, it also becomes a small amount of multi-pass lamination welding, which increases the number of lamination defects such as poor penetration and decreases welding efficiency.

In addition, Patent Literature 4 discloses an electro-gas arc welding apparatus of two electrodes that enables one-pass welding of an extremely thick material.

By using the two-electrode gas arc welding device, it is possible to join thick steel materials up to a thickness of about 70 mm. However, since the amount of heat input is greatly increased to 360 kJ/cm by two-electrode formation, it is very satisfying to satisfy these properties when the heat effect on the steel sheet is large and high properties (strength, toughness) are required for the joint. It becomes difficult.

In addition, in the electro-gas arc welding apparatus of this two electrode, it is indispensable to form a backing strip of ceramic on the back side and a pressurizing mechanism of a water-cooled copper strip on the surface (welder side), which is inevitable. While there is no worry, the welding device becomes complicated.

In addition, in this two-electrode arc gas arc welding apparatus, since it is indispensable to form a pressing mechanism for the copper strip on the surface (welder side), one-pass welding is the basic, and multi-pass lamination welding is used to achieve low heat input. It is difficult to do.

Japanese Patent Application Publication No. 2009-61483 Japanese Patent Application Publication No. 2010-115700 Japanese Patent Application Publication No. 2001-205436 Japanese Patent Application Publication No. Hei 10-118771 Japanese Patent Publication No. 5884209

As described above, the present situation is that a high-quality, high-efficiency, vertically improved gas shielded arc welding method applicable to welding of thick steel materials has not yet been developed.

On the other hand, the welding automation technology (welding robot) has been made lightweight, high-functionality, and high-precision, and weaving of welding torches suitable for the improved shape and welding posture, which has been difficult so far, becomes possible, and by utilizing this, steel materials are improved. Welding construction (condition setting) suitable for a shape, a welding posture, and a welding material (wire) is becoming possible.

The present invention utilizes high-performance and high-precision welding automation technology to perform high-quality and high-efficiency welding of thick steel materials by weaving precise welding torches in accordance with improved shapes and welding postures. It is an object to provide an improved gas shield arc welding method.

However, the inventors repeatedly reviewed the above problems to solve the above problems, and first,

``Vertical direction narrow gas shield arc welding method of joining two thick steel materials having an improvement angle of 25° or less, an improvement gap of 20 mm or less, and a plate thickness of 40 mm or more by vertical multi-layer welding using weaving. In,

When welding the first layer, the angle of the welding torch is 25° or more and 75° or less with respect to the horizontal direction, and the welding heat input is 30 kJ/cm or more and 170 kJ/cm or less, and weaving depth with respect to the plate thickness direction. Is 15 mm or more and 50 mm or less, and when the width of the weld bead in super-layer welding is W, the maximum width of weaving in the direction of the plate thickness and the direction perpendicular to the weld line is (W-6) mm or more and W mm or less. By weaving the welding torch,

A method for vertically improved gas shield arc welding in which the bonding depth in the super-layer welding is 20 mm or more and 50 mm or less.

Was developed and disclosed in Patent Document 5.

With the technique of Patent Document 5 posted above, it has become possible to provide a high-quality and high-efficiency vertically improved gas shielded arc welding method applicable to welding of thick steel materials.

However, in the technique of Patent Document 5, when the improvement angle becomes smaller, depending on the composition of the welding wire, the arc crawls over the improvement wall surface, making the welding unstable, or sputtering occurs during welding, and welding defects are likely to occur. There was a problem of losing.

Therefore, the inventors, through further examination, to solve the above problems,

As a welding wire, while using a welding wire in which REM was added in a range of 0.015 to 0.100 mass%,

It is assumed that weaving is performed by a welding torch having more detailed control of welding conditions in a super-layer welding, that is, a bending portion and a tip portion defined by the bending portion. When weaving the improved surface of the thick steel material, the tip of the welding torch is shaken under appropriate conditions toward the improved surface of the thick steel material.

By this, even if the improvement angle becomes smaller, it is possible to prevent the gear from rising to the improved wall surface of the arc and to sufficiently melt the improved surface, and as a result, sufficient joint depth is secured while preventing occurrence of welding defects. It has been found that it is possible to achieve stabilization of the bead shape including suppression of sagging of molten metal, which is a problem in vertical welding of high currents, and furthermore, it is possible to achieve high toughness of the weld seam.

The present invention has been completed through further examination based on the above knowledge.

That is, the main structure of the present invention is as follows.

1. Vertical improvement gas shield that joins two thick steel materials with a thickness of 10 mm or more by one layer welding or multi-layer welding using weaving, with an improvement angle of 20° or less and an improvement gap of 20 mm or less. In the arc welding method,

REM: While using a welding wire containing 0.015 to 0.100 mass%,

It is assumed that weaving of the first layer welding is performed by a welding torch having a bent portion and a tip portion defined by the bent portion, and at that time, when weaving the improved surface of the thick steel material, the tip portion of the welding torch is The front end portion of the welding torch at the reference position is set to a position where the tip portion of the welding torch coincides with the direction of the welding line as viewed from the plate thickness direction of the thicker plate. The angle θ1 with respect to the horizontal direction is 10° or more and 45° or less, and the swing angle θ2 of the tip of the welding torch from the reference position is 5° or more and 60° or less,

The bonding depth in the first layer welding is 10 mm or more,

Method for vertical narrow gas shield arc welding.

2. The vertical narrow narrow gas shield arc welding method according to the above 1, wherein the joining is performed by one-layer welding and the improvement gap is 25% or less of the thickness of the thick steel material.

3. The vertical narrow narrow gas shield arc welding method according to the above 1, wherein the joining is made of multilayer welding, and the joining depth in the first layer welding is 10 mm or more and 70 mm or less.

4. In the weaving of the super-layer welding, the weaving pattern of the welding torch viewed in the direction of the welding line has a nose shape, and the method for vertically narrowing gas shield arc welding according to any one of 1 to 3 above.

According to the present invention, even when welding thick steels having a plate thickness of 10 mm or more in an improvement condition with a small improvement angle, stabilization of the bead shape and welding defects including suppression of sagging of molten metal, which is a problem in vertical welding, High-quality, high-efficiency, narrow-line gas shield arc welding can be performed while preventing occurrence, and a high-toughness welded seam can be obtained.

In addition, the welding method of the present invention has a smaller welding amount compared to a conventional gas shielded arc welding, and energy saving by high efficiency of welding can also be achieved, so that a significant reduction in welding construction cost can be achieved.

In addition, in the welding method of the present invention, the pressure mechanism of the water-cooled copper strip that prevents the molten metal from falling off, such as the electrogas arc welding apparatus shown in Patent Document 4, is unnecessary, and the complexity of the apparatus can be avoided. Since it is possible to suppress welding heat input per pass by welding construction in a multi-pass or predetermined improved shape, it is easy to secure desired mechanical properties in the heat-affected zone of the weld metal and steel.

1 shows examples of various improved shapes.
Fig. 2 shows the construction tips when constructing super-layer welding by the welding method according to one embodiment of the present invention in the V-shaped improved shape.
Fig. 3 is a schematic view showing a swinging state of a welding torch during weaving of an improved surface of a thick steel material.
Fig. 4 shows an example of an improved cross-section after performing super-layer welding in the V-shaped improved shape.
5 shows the weaving pattern of the welding torch viewed from the welding line direction in weaving of super-layer welding.

Hereinafter, the present invention will be described in detail.

1(a) to (c) show examples of various improved shapes. In the figure, reference numeral 1 denotes an improved surface of thick steel material, 2 is an improved surface of thick steel material, 3 is an improvement at the lower end of the steel material (in Y-type improvement), an angle of improvement with a symbol θ, an improvement gap with G, and a plate thickness with t H denotes the height of improvement at the lower end of the steel (in Y-type improvement).

As shown in the figure, the improvement shape to be targeted here can be either V-type improvement (including I-type improvement and レ-type improvement) or Y-type improvement, and as shown in Fig. 1(c). Likewise, it can also be made into a multi-stage Y-type improvement.

1(b) and (c), the improvement angle and the improvement gap in the case of Y-type improvement are the improvement angle and the improvement gap in the improvement at the lower end of the steel material. Here, the improvement of the lower end of the steel material is an area from the steel material surface that becomes the back surface (the surface on the welding device (welding torch) side is the surface, and the surface on the opposite side is the back surface) at the time of welding to about 20 to 40% of the plate thickness. Means

Moreover, FIG. 2 shows the construction tips at the time of constructing super-layer welding by the welding method which concerns on one Embodiment of this invention in the V shape improvement shape. In the figure, reference numeral 4 is a welding torch, 5 is a welding wire, and 6 is a backing strip material. In addition, illustration about the welding line, molten paper, and welding beads is omitted.

Here, as shown in Fig. 2, the present welding method is gas shield arc welding in which two thick steel materials having a predetermined plate thickness are abutted, and these thick steel materials are joined by vertical welding using weaving, It is based on the upward welding that moves the direction upward. Then, when weaving the improved surface of the thick steel material, the tip of the welding torch is rocked toward the improved surface of the thick steel material.

In addition, although the V-shaped improvement shape was shown as an example here, the other improvement shape is also the same.

Fig. 3 is a schematic diagram showing the swinging state of a welding torch when weaving the improved surface of a thick steel material, and Figs. 3(a) and 3(b) are respectively in the plate thickness direction (of the thick steel material in Fig. 2). It shows the state where the welding torch is in the reference position and the state where the welding torch is rocked at an angle of θ2 as seen from the back side (the side with the backing strip material), and FIG. 3(c) is the X arrow diagram of FIG. 3(a). . In addition, as shown in FIG. 3(a), the reference position is a position where the tip portion of the welding torch (center line, that is, the projecting direction of the welding wire) coincides with the welding line direction as viewed in the plate thickness direction. In Fig. 3 (a) and (b), it is assumed that the improved surface (not shown) of the thick steel material to be melted is on the left side toward the ground.

In the figure, 7 is a body part, 8 is a power feeding chip, 9 is a bent part, and 10 is a distal end part. Here, the tip part 10 is a part which becomes the welding wire (not shown) side rather than the bending part 9. Further, the bent portion 9 may be formed in either the main body portion 7 and the feeding chip 8 constituting the welding torch, but is preferably formed in the feeding chip 8 from the viewpoint of constructability and the like. .

Further, θ1 is the angle with respect to the horizontal direction of the tip of the welding torch at the reference position, θ2 is the swing angle of the tip of the welding torch from the reference position, θ3 is the bending angle at the bend of the welding torch, l is welding The length of the tip of the torch, each of which is relative to the centerline of each portion of the welding torch.

Moreover, FIG. 4 shows an example of the improved cross section after super-layer welding in the V-shaped improved shape. In the figure, reference numeral 11 is a welding bead, and symbol D denotes a joining depth in super-layer welding, and W denotes a welding bead width in super-layer welding (gap between improvements after super-layer welding).

In addition, the joining depth (D) in a super-layer welding is the minimum value of the weld bead height in a super-layer welding in the case where the steel surface serving as the back surface at the time of welding is the starting point (closest (lowest) super layer from the starting steel surface) Welding bead height).

Although the V-shaped improved shape is shown as an example here, D and W are the same even in other improved shapes.

Next, in the present welding method, the reason why the angle of improvement, the gap of improvement, and the plate thickness of the steel material is limited to the above range will be described.

Improvement angle θ: 20° or less

The smaller the improvement part of the steel material is, the faster and more efficient welding is possible, while defects such as fusion defects are likely to occur. In addition, welding when the improvement angle exceeds 20° can also be carried out by a conventional construction method. For this reason, in this welding method, it is targeted for cases where the construction is difficult with the conventional construction method, and the improvement angle is expected to be more efficient: 20° or less.

In addition, in the V-type improvement, when the improvement angle is 0°, it is called a so-called I-type improvement, and it is most efficient when it is 0° in terms of the amount of welding, and even if the improvement angle is 0° (I-type improvement) However, since the improvement is closed during welding due to welding heat deformation, it is preferable to set the improvement angle according to the plate thickness t (however, in the case of Y-type improvement, the improvement height (h) of the lower end of the steel) Do.

Specifically, the improvement angle is preferably in the range of (0.5 × t/20) to (2.0 × t/20)°, more preferably (0.8 × t/20) to (1.2 × t/20) ° range. For example, when the plate thickness t is 100 mm, the improvement angle is preferably in the range of 2.5 to 10°, more preferably in the range of 4 to 6°.

However, when the plate thickness t exceeds 100 mm, the upper limit of the suitable range exceeds 10°, but the upper limit of the suitable range in this case is set to 10°.

Improvement gap (G): 20 mm or less

The smaller the improvement part of the steel material, the faster and more efficient welding is possible. In addition, in the case where the improvement gap exceeds 20 mm, molten metal is liable to be stretched and construction is difficult. In order to countermeasure, it is necessary to suppress the welding current to be low, but welding defects such as slag mixing tend to occur. Therefore, the improvement gap is targeted at a case of 20 mm or less. It is preferably in the range of 4 mm or more and 12 mm or less. Moreover, in particular, when joining by one-layer welding which consists only of super-layer welding, it is more preferable that the improvement gap is 25% or less of the thickness of the steel material to be welded. More preferably, it is 20% or less.

Plate thickness (t): 10 mm or more

The thickness of the steel material is 10 mm or more. This means that if the thickness of the steel plate is less than 10 mm, even if a conventional welding method is used, for example, semi-automatic CO ₂ arc welding using a semi-flux cored wire, sound joints are suppressed while suppressing the amount of heat input. It is because it may be obtained. It is preferably 15 mm or more, and more preferably 20 mm or more.

In addition, in the case of targeting general rolled steel, the plate thickness is generally an upper limit of 100 mm. Therefore, it is preferable that the upper limit of the sheet thickness of the target steel is 100 mm or less.

In addition, high-strength steel (e.g., YP 460 ㎫ grade steel for shipbuilding (tensile strength 570 ㎫ grade steel) or TMCP steel SA440 (tensile strength 590 ㎫ grade steel) for construction) is particularly suitable as the steel to be welded. desirable. That is, the high-strength steel has strict welding heat input limitations, and is susceptible to cracking in the weld metal, and the joint strength and toughness required by the welding heat effect are not obtained. On the other hand, in this welding method, it is possible to efficiently weld at a heat input amount of 170 kJ/cm or less, and it is also possible to weld a 590 ㎫ class high-tensile steel sheet and a 590 ㎫ class corrosion-resistant steel that becomes a high-alloy system. Naturally, mild steel can be handled without problems.

In the above, in this welding method, the reason for limiting the angle of improvement, the gap of improvement, and the plate thickness of the steel was explained, but in this welding method, REM is used for the composition of the components of the steel material and the metal-based system to be welded materials. It is important to use a welding wire added.

Hereinafter, the component composition of the welding wire used in the present welding method will be described.

REM: 0.015 to 0.100 mass%

REM is an effective element for refinement of inclusions during steelmaking and casting and improvement of toughness of weld metal. In addition, REM is particularly advantageous when the welding wire is made to have a positive polarity (wire minus) or when the welding current is increased, thereby miniaturizing the volume and stabilizing the volume transition, and further, generating arcs on the improved surface. It also has the effect that it can be suppressed. By miniaturization of this volume and stabilization of volume transfer, sputtering can be suppressed and stable gas shield arc welding can be performed. Here, when the REM content is less than 0.015% by mass, the effect of miniaturizing the volume and stabilizing the volume transition is not obtained. On the other hand, if the REM content exceeds 0.100% by mass, cracks may occur in the manufacturing process of the welding wire, or lower the toughness of the weld metal. Therefore, the REM content of the welding wire is in the range of 0.015 to 0.100 mass%. It is preferably in the range of 0.025 to 0.050 mass%.

In addition, the components other than the above-mentioned REM are not particularly limited, and may be appropriately selected depending on the steel type or the like of the steel material to be welded. For example, when welding a high-tensile steel sheet as described above, in addition to the REM described above, C: 0.10 to 0.20 mass%, Si: 0.05 to 2.5 mass%, Mn: 0.25 to 3.5 mass%, P: 0.05 mass % Or less, S: 0.02 mass% or less, Al: 0.005 to 3.00 mass%, O: 0.008 mass% or less, and N: 0.008 mass% or less, and the remainder may be a component composition that becomes Fe and inevitable impurities.

In addition, the polarity of the welding wire to be used is preferably a wire minus (positive polarity) from the viewpoint of sufficiently obtaining the effect of miniaturization of volume and stabilization of volume transfer by addition of REM.

In addition, in the present welding method, it is important to use a welding wire to which the above-mentioned REM is added, and to efficiently weld while efficiently controlling superheated welding conditions with an appropriate amount of heat input suitable for the improved shape to obtain a predetermined joint depth. .

Hereinafter, this welding condition and a joining depth are demonstrated.

Angle θ1 with respect to the horizontal direction of the tip of the welding torch at the reference position: 10° or more and 45° or less

As shown in Fig. 3, by using a welding torch having a bent portion and a tip portion defined by the bent portion, weaving while swinging the tip portion of the welding torch toward an improved surface of the thick steel material, thereby feeding the chip and the thick steel material. It is possible to bring the wire tip closer to the improved surface while avoiding contact with the improved surface. In addition, since the tip of the wire also faces the improvement surface, direct melting of the improvement surface by arcing becomes possible. For this reason, even when the amount of heat input by welding per pass is suppressed, the improvement surface can be sufficiently melted to suppress the occurrence of welding defects. Further, by extending the arc heat input range by weaving the welding torch, it is possible to suppress the falling of molten metal and to stabilize the bead shape.

However, when θ1 is less than 10°, the above-described effect is not sufficiently obtained, and welding defects or sagging of molten metal occur. On the other hand, when θ1 exceeds 45°, the feeding resistance of the wire in the bent portion of the welding torch increases, making it difficult to continue welding stably, which also causes weld defects and molten metal sag. For this reason, the angle θ1 with respect to the horizontal direction of the tip of the welding torch at the reference position is set to be 10° or more and 45° or less. Preferably, it is 15 degrees or more and 30 degrees or less.

Rotation angle θ2 of the tip of the welding torch from the reference position: 5° or more and 60° or less

As described above, by using a welding torch having a bent portion and a tip portion defined by the bent portion, weaving while rotating the tip portion of the welding torch toward an improved surface of the thick steel material, thereby feeding the feed chip and the thick steel material It becomes possible to bring the wire tip closer to the improved surface while avoiding contact of the improved surface of the. In addition, since the tip of the wire also faces the improvement surface, direct melting of the improvement surface by arcing becomes possible. For this reason, even when the amount of heat input by welding per pass is suppressed, the improvement surface can be sufficiently melted to suppress the occurrence of welding defects. Further, by extending the arc heat input range by weaving the welding torch, it is possible to suppress the falling of molten metal and to stabilize the bead shape.

However, when θ2 is less than 5°, the above effect is not sufficiently obtained, and welding defects or sagging of molten metal occur. On the other hand, when θ2 exceeds 60°, the improved surface is excessively melted, and welding defects due to the undercut of the improved surface occur. For this reason, the swing angle θ2 of the tip of the welding torch from the reference position is 5° or more and 60° or less. Preferably, it is 10 degrees or more and 45 degrees or less.

Further, the bending angle θ3 in the bending portion of the welding torch and the length l of the tip portion of the welding torch are not particularly limited, but from the viewpoint of controlling θ1 and θ2 within the above range, θ3 is in the range of 10 to 45° , l is preferably in the range of 10 to 50 mm.

Bonding depth D in super-layer welding: 10 mm or more

In order to weld thick steel materials to be welded materials, in particular, plate thicknesses: 40 mm or more, as a predetermined improvement shape, it is necessary to set the bonding depth in super-layer welding to 10 mm or more. Moreover, since the welding heat is concentrated when the joining depth in super-layer welding is less than 10 mm, sagging of molten metal occurs. Therefore, the joining depth in super-layer welding is 10 mm or more. It is preferably 25 mm or more. In addition, the upper limit of the joining depth in super-layer welding is about 100 mm, which is the same as the upper limit of the plate thickness of steel materials.

However, in the case of performing multi-layer welding, particularly when the sheet thickness of the steel material to be welded is 80 mm or more, when the joining depth in super-layer welding exceeds 70 mm, welding heat input tends to be excessive, and high-temperature cracking occurs. However, there is a fear that welding defects such as poor fusion of the improved surface due to heat dissipation during welding and slag mixing may occur. Therefore, when performing multi-layer welding, it is preferable that the joining depth in super-layer welding is 10 mm or more and 70 mm or less. More preferably, it is 20 mm or more, 60 mm or less, and still more preferably 25 mm or more and 55 mm or less. In the case of single-layer welding, more preferably 15 mm or more and 65 mm or less.

The basic conditions have been described above, but in the welding method of the present invention, it is preferable to further satisfy the following conditions.

Weaving depth (L) with respect to the plate thickness direction in weaving of the welding torch: 10 mm or more and 70 mm or less

The present welding method is to perform weaving of the welding torch, but the weaving depth (L) for the plate thickness direction in the weaving of the welding torch and the maximum weaving width (M) for the plate thickness direction and direction perpendicular to the welding line to be described later. It is also important to properly control ).

Here, the weaving depth L with respect to the plate thickness direction and the maximum weaving width M with respect to the plate thickness direction and the direction perpendicular to the welding line in various weaving patterns are as shown in Figs. 5(a) to (d). It goes together.

In addition, the weaving depth (L) referred to herein and the maximum width (M) of weaving for the plate thickness direction and the direction perpendicular to the welding line, which will be described later, do not take into account the fluctuation of the tip of the welding torch, and the tip of the tip of the welding torch is described above. It is the maximum weaving width and the weaving depth of the welding wire tip obtained by assuming it is in the position. In addition, the weaving pattern referred to here is a trajectory of the tip of the welding wire when it is assumed that the tip of the tip of the welding torch is always at the above-mentioned reference position without considering the fluctuation of the tip of the tip of the welding torch.

Here, in the vertical upward welding based on the present welding method, since the bonding depth and the weaving width in the plate thickness direction are about the same, when the weaving depth in the plate thickness direction is less than 10 mm, the desired bonding depth is obtained. It becomes difficult. On the other hand, when the weaving depth with respect to the plate thickness direction exceeds 70 mm, not only is it difficult to obtain a desired bonding depth, but the amount of heat input to the weld is excessive, so that it is necessary to obtain desired mechanical properties in the heat-affected zone of the weld metal or steel. Besides being difficult, welding defects such as poor fusion of the improved surface due to heat cracking and heat dissipation during welding and slag mixing tend to occur.

Therefore, the weaving depth in the plate thickness direction is 10 mm or more and 70 mm or less. It is preferably 15 mm or more and 65 mm or less. In addition, in the case of single-layer welding, it is preferably 20 mm or more and 60 mm or less. Moreover, in the case of multilayer welding, it is preferably 25 mm or more and 55 mm or less.

Maximum width of weaving in the direction of the plate thickness in the weaving of the welding torch and the direction perpendicular to the welding line (M): (W-6) mm or more and W mm or less (W: welding bead width in super-layer welding)

In order to prevent un-melting of the improved surface, it is necessary to make the maximum weaving width in the plate thickness direction and the direction perpendicular to the welding line (W-6) mm or more. On the other hand, if the maximum width of weaving in the plate thickness direction and the direction perpendicular to the welding line exceeds W mm, there is a fear that the sagging of the molten metal occurs and welding is not established.

Therefore, it is preferable that the maximum width of weaving in the plate thickness direction and the direction perpendicular to the welding line is in the range of (W-6) mm or more and W mm or less. More preferably, it is a range of (W-4) mm or more and (W-1) mm or less.

Further, in the case of single-layer welding, W is an improvement width on the steel material surface that becomes the surface (surface of the welding device (welding torch) side) during welding.

Further, the weaving pattern of the welding torch is not particularly limited, and as shown in Figs. 5(a) to 5(d), the nose shape, V as seen in the welding line direction (consistent with the welding advancing direction and usually perpendicular direction) It can be shaped like a trapezoid, a trapezoid, or a triangle. For example, when the weaving pattern is in the shape of a nose or trapezoid, the weaving of point A → point B and point C → point D as shown in FIGS. 5(a) and (b) corresponds to weaving for the improved surface of thick steel It becomes. In this case, in the weaving from point A to point B, the tip of the welding torch is rocked toward the ground toward the improvement surface of the left thick steel material, while in the weaving from point C to point D, the tip of the welding torch is directed toward the ground It swings toward the improvement surface of the thick steel material on the right. In addition, in the weaving of B point → C point (in the case of trapezoid, D point → A viscosity is included), it is not necessary to swing the tip of the welding torch. In addition, the trajectory of the welding torch at each point in FIG. 5(a)-(d) where the direction of the welding torch changes (point B and C in FIG. 5(a)) may be rounded or rounded. You may do it.

However, in vertical upward welding, weaving at a point close to the welding surface side tends to cause the molten metal to sag and fall. Further, when the welding torch operation deviates from the improved surface, uniform melting of the improved surface is not obtained, and welding defects such as fusion defects are likely to occur. Particularly, in general trapezoidal and triangular weaving patterns that do not require a reversing operation, while the device load is small, the welding torch operation at a point close to the welding surface side (D point of trapezoidal weaving pattern in Fig. 5(b)) → Point A, point C of the triangular weaving pattern in Figure 5(d) → point A) are likely to cause sagging of molten metal. For this reason, from the viewpoint of suppressing the dripping of molten metal, it is preferable to use a weaving pattern of a nose shape or a V shape without a torch operation on the welding surface side.

In addition, in the V-shaped or triangular weaving pattern, when the improvement gap is large (for example, 6 mm or more), the welding torch operation deviates from the improvement surface (for example, point A in FIG. 5(c)). → in the operation of point B, the trajectory of the tip of the welding torch does not become parallel to the improved surface (the side closer to the welding torch), uniform melting of the improved surface is not obtained, and welding defects such as poor fusion It is easy to occur. Therefore, in such a case, it is optimal to set the weaving pattern of a nose shape, which is easy to operate the welding torch parallel to the improved surface.

Moreover, in the thickness direction, the deepest point of the front end of the welding wire during weaving (for example, points B and C in FIGS. 5(a) and (b), and FIGS. 5(c) and (d)) The distance (a) from the steel back surface of point B in) is usually about 2 to 5 mm.

In addition, when applying the nose-shaped weaving or trapezoidal weaving to the above-described improved shape, M ₁ , M ₂ , and M ₃ in FIGS. 5(a) and (b) are 2 to 18 mm and 0 to 10 mm, respectively. , 0 to 10 mm.

In addition, the frequency and stop time at the time of weaving (stop time at each point such as A point shown in Fig. 5) are not particularly limited, and for example, the frequency is 0.25 to 0.5 Hz (preferably 0.4 to 0.5 Hz). ), and the stop time may be about 0 to 0.5 seconds (preferably 0.2 to 0.3 seconds).

Regarding the conditions other than the above, there is no need to specifically specify, but when the average welding current is less than 270 A, the molten paper is small, and on the surface side, it becomes in the same state as multi-layer welding in which melting and solidification are repeated every torch weaving, resulting in poor fusion and slag mixing. Prone to occur On the other hand, when the average welding current exceeds 360 A, the sagging of the molten (welded) metal is liable to occur, and it is difficult to check the arc point by welding fume and sputtering, so adjustment during construction becomes difficult. For this reason, it is preferable that the average welding current is 270 to 360 A. Further, by setting the average welding current to 270 to 360 A, stable welding can be obtained while suppressing the generation of welding fume and sputtering, which makes it more advantageous in carrying out the present welding method.

For the conditions other than this, the normal method may be used, for example, welding voltage: 28 to 37 V (rise with current), welding speed (upward): 1 to 15 cm/min (preferably 4 to 9 cm/ Minutes), the wire protrusion length: 20 to 45 mm, and the wire diameter: 1.2 to 1.6 mm.

Moreover, the shielding gas composition is not particularly limited, and a gas of CO ₂ alone or a mixed gas of Ar and CO ₂ may be used.

In addition, in the case of multi-layer welding, it is preferable that the number of laminations until completion of welding is about 2 to 4 layers from the viewpoint of preventing lamination defects. The welding conditions in each layer other than the super layer are not particularly limited, and may be performed according to a regular method, and may be, for example, the same as the welding conditions of the super layer described above.

In addition, in the welding method of this invention, it is based on 1 pass welding per layer.

Example

The welding torches (θ3: 15°, l: 20 mm) having a bent portion in the feed chip as shown in FIG. 3 were used for the two steel materials having the improved shape shown in Table 1 under the welding conditions shown in Table 2, A vertically upward gas shield arc welding of narrow lines was performed.

Here, all of the steel materials are C: 0.04 to 0.06 mass%, Si: 0.1 to 0.2 mass%, Mn: 1.8 to 2.0 mass%, P: 0.01 mass% or less, S: 0.005 mass% or less, Al: 0.02 to 0.06 mass %, O: 0.003% by mass or less and N: 0.005% by mass or less, and the remainder was a component composition that became Fe and inevitable impurities. In addition, gas cutting was used for the improvement processing of the steel material, and treatment such as grinding was not performed on the improvement surface.

In addition, as the welding wire, a solid wire having a grade of 1.2 mmφ for a steel strength strength or a rank higher than that used was used. In addition, all of the component compositions of the welding wires other than REM shown in Table 2 are C: 0.10 to 0.20 mass%, Si: 0.6 to 0.8 mass%, Mn: 1.8 to 2.0 mass%, P: 0.01 mass% or less, S: It contained 0.005 mass% or less, Al: 0.005-0.03 mass %, O: 0.003 mass% or less, and N: 0.005 mass% or less, and the balance was made into the component composition which becomes Fe and inevitable impurities.

In addition, the welding current is 260 to 340 A, the welding voltage is 28 to 38 V (rises with the current), the average welding speed is 2.0 to 10.1 cm/min (adjusted during welding), and the average wire protrusion length is 30 mm, The welding length was 400 mm. Moreover, in any case, CO ₂ alone gas was used as the shielding gas, and a gas shielding system different from a conventional arc welding nozzle was formed to perform welding.

In addition, Nos. 9 to 11 and 14 are multi-layer welding, and in welding in each layer other than the super-layer, the gas to which weaving is applied with welding current in the range of 270 to 360 A and welding voltage in the range of 28 to 37 V Shield arc welding was performed to complete the weld seam. Further, Nos. 1 to 8, 12, 13, 15, 16, and 17 were welded one layer to finish the weld seam.

After the first layer welding, the bead width and the bonding depth were measured by observation of a cross-section macrostructure of 5 points selected at random. In addition, with respect to the bead width, the maximum value of the measured value was taken as the bead width (W) in super-layer welding, and with respect to the joining depth, the minimum value of the measured value was taken as the joining depth (D) in super-layer welding.

Moreover, the sagging of molten metal at the time of super-layer welding was visually evaluated as follows.

◎: no sagging of molten metal

○: Less than 3 points of sagging of molten metal

×: At least 3 points of molten metal sagging, or welding stop

Moreover, the ultrasonic joint inspection was performed about the weld seam finally obtained, and it evaluated as follows.

◎: No detection defect

(Circle): Only the defect with a defect length of 3 mm or less is detected.

X: A defect with a defect length exceeding 3 mm was detected.

Further, the welded seam finally obtained was subjected to a Charpy impact test in accordance with JIS Z 2242 (test temperature: 0°C) so that the center of the weld metal was in the notched position, and the absorption energy vE0 (J) at the test temperature was measured. By measuring, the toughness of the weld metal was evaluated by the following criteria.

◎: vE0 (J) is 47 J or more

○: vE0 (J) is less than 47 J, and more than 27 J

×: vE0 (J) is less than 27 J

Table 2 shows these results.

As shown in Table 2, in Inventive Examples Nos. 3 to 7, 9 and 10, there were no saggings of molten metal in the first layer welding, but there were two or fewer points. Moreover, even in the ultrasonic flaw detection, even if there were no detection defects, the defect length was 3 mm or less. In addition, in these examples of the invention, excellent toughness of the weld metal was obtained.

On the other hand, in Comparative Examples No. 1, 2, 8, 11 to 17, there were sagging of molten metals of three or more points, or a defect with a defect length of more than 3 mm was detected in ultrasonic flaw detection, and/or sufficient Toughness of the weld metal was not obtained.

1: Thick steel
2: Improvement of thick steel
3: Improvement of the lower part of steel
4: welding torch
5: welding wire
6: Backing strip material
7: main body
8: feed chip
9: bend
10: tip
11: welding bead

Claims (4)

Vertical angle narrow gas shield arc welding in which two thick steel materials with an improvement angle of 20° or less, an improvement gap of 20 mm or less, and a sheet thickness: 10 mm or more are joined by one-layer welding or multi-layer welding using weaving. In the way,
REM: While using a welding wire containing 0.015 to 0.100 mass%,
It is assumed that weaving of the first layer welding is performed by a welding torch having a bent portion and a tip end defined by the bent portion, and at that time, when weaving the improved surface of the thick steel material, the tip portion of the welding torch is Then, it is rocked toward the improvement surface of the steel material, and the position where the tip portion of the welding torch coincides with the direction of the welding line as viewed from the plate thickness direction of the steel material is used as a reference position, and the tip portion of the welding torch at the reference position The angle θ1 with respect to the horizontal direction is 10° or more and 45° or less, and the swing angle θ2 of the tip of the welding torch from the reference position is 5° or more and 60° or less,
The joining depth in the first layer welding is 10 mm or more,
Method for vertical narrow gas shield arc welding. According to claim 1,
A method for vertically narrowing gas shielded arc welding, wherein the joining is made by one-layer welding, and the improvement gap is 25% or less of the thickness of the thick steel material. According to claim 1,
A method of vertically narrowing the gas shielded arc welding method, wherein the joining is a multi-layer welding, and the joining depth in the first layer welding is 10 mm or more and 70 mm or less. The method according to any one of claims 1 to 3,
In the weaving of the super-layer welding, the weaving pattern of the welding torch seen in the direction of the welding line is in the form of a nose, a narrow narrow gas shield arc welding method.

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