KR102049215B1 - Vertical narrow gap gas shielded arc welding method - Google Patents

Abstract

Superlayer welding conditions, in particular, welding torch angle, welding heat input amount, and weaving conditions are controlled appropriately, and the depth of joining in superlayer welding is set to 20 mm or more and 65 mm or less, and welded to the thick steel material at the time of final layer welding. As the covering material for the improvement of the thick steel material from the torch side, a cooling plate capable of sliding movement in the upward direction is applied, and welding is performed while the cooling plate moves upward in accordance with the welding torch upward movement.

Description

VERTICAL NARROW GAP GAS SHIELDED ARC WELDING METHOD}

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

In the present invention, "improved improvement" means that the minimum improvement width between steels of which the improvement angle is 25 degrees or less and the welded material is 50% or less of the plate thickness of the steel.

Steel gas shielded arc welding used for welding is a fusing electrode expression common to use a CO ₂ gas alone, or a mixed gas of Ar and CO ₂ in the molten parts of the shield. Such gas shielded arc welding is widely used in the manufacturing fields of automobiles, buildings, bridges, shipbuilding, and electrical equipment.

However, in recent years, with the increase in size and thickness of steel structures, the amount of welds in the welding process, in particular, butt welding of steel materials, increases, and further, a large amount of time is required for welding construction, resulting in an increase in construction cost. Doing.

As a method of improving this, application of the narrow-line gas shielded arc welding which welds the improvement of the small clearance with respect to the plate | board thickness by the arc welding method is considered. Since the welding amount of the narrow-improved gas shielded arc welding is smaller than that of the conventional gas shielded arc welding, it is expected that high welding efficiency and energy saving can be achieved, and further, construction cost will be reduced.

On the other hand, although electroslag welding is normally applied to the vertical high efficiency welding, 1 pass high heat input welding is the basic, and in welding with plate | board thickness exceeding 60 mm, heat input becomes excessive and a toughness may fall. It is becoming. Moreover, 1-pass welding has a limit of plate | board thickness, and it is a present situation that the welding of plate | board thickness exceeding 65 mm is not technically established yet.

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

As a welding method in which such narrow-impedance gas shielded arc welding is applied to vertical welding, for example, Patent Document 1 discloses a double-sided multilayer welding method targeting a double-sided U-shaped improved joint. In this welding method, lamination welding by TIG welding using an inert gas is performed. By using an inert gas, the generation of slag and sputter is suppressed and the lamination defect is prevented.

However, the non-fusing electrode expression, TIG welding, consumption as compared with the MAG welding and CO ₂ welding using the electrodes of steel wire, that the welding process itself, efficiency drops significantly.

Moreover, Patent Document 2 discloses a method for vertically welding a narrow line in which weaving of a welding torch is performed in order to suppress sputtering and fusion defects.

However, in this welding method, since the weaving direction of the welding torch is not the improvement depth direction but the steel plate surface direction, it is necessary to weav the welding torch before the molten metal sags, and as a result, the welding current is about 150 A. It is necessary to set a low current of and to suppress the amount of deposition (heat input amount) per one pass.

Therefore, when this welding method is applied to the welding of a thick steel plate with a large plate thickness, a small amount of multi-pass lamination welding is performed, and a large number of lamination defects, such as penetration defects, increase welding efficiency significantly.

In addition, Patent Document 3 discloses a vertical welding method for weaving a welding torch in order to suppress a fusion defect similarly to Patent Document 2.

Although the plane angle (improvement angle) disclosed here is wide at 26.3-52 degrees, the weaving of the welding torch here is implemented also in the improvement depth direction. For this reason, in the vertical welding method of Patent Document 3, it is possible to take a relatively large amount of deposition per pass.

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

Therefore, when this welding method is applied to the welding of a thick steel plate with a large plate thickness, a small amount of multi-pass lamination welding is also performed, and the lamination defects such as penetration defects increase, and welding efficiency falls.

In addition, Patent Document 4 discloses a two-electrode electrogas arc welding device that enables one-pass welding of an extremely thick material.

By use of the electrogas arc welding apparatus of this two electrode, joining of the thick steel material to plate | board thickness: about 70 mm is attained. However, the amount of heat input is greatly increased by about 360 kJ / cm by the two-electrode formation. For this reason, when the heat influence to a steel plate is large and a high characteristic (strength, toughness) is required for a joint, it becomes very difficult to satisfy such a characteristic.

Moreover, in the electrogas arc welding apparatus of this two electrode, since the arc of a back electrode is hard to be seen, there exists a problem that prevention of a welding defect becomes difficult. Moreover, in the electrogas arc welding apparatus of this two electrode, it is difficult to provide a copper strip in an improvement from problems, such as improved dimensional accuracy, and for this reason, it is difficult to aim at low heat input as a multipass laminated welding.

Japanese Unexamined Patent Publication No. 2009-61483 Japanese Unexamined Patent Publication No. 2010-115700 Japanese Unexamined Patent Publication No. 2001-205436 Japanese Unexamined Patent Publication No. 10-118771

As described above, a high quality and highly efficient vertical narrowing gas shielded arc welding method that can be applied to welding thick steel materials has not been developed yet.

On the other hand, the light weight, high performance, and high precision of welding automation technology (welding robot) are advanced, and the weaving of the welding torch suitable for the improved shape and welding posture which has been difficult until now becomes possible, and by utilizing this, steel materials, improved shape, welding posture and Welding construction (condition setting) suitable for a welding material (wire) is attained.

The present invention provides a high quality and highly efficient vertical narrowing gas shielded arc which can be applied to welding thick steels, especially thick steels having a plate thickness of 40 mm or more, by utilizing a highly functional and high precision welding automation technique. It is an object to provide a welding method.

By the way, in order to solve the said subject, the inventors earnestly studied about the welding conditions at the time of applying a vertical narrowing gas shielded arc welding to a thick steel material.

As a result, when performing narrow line gas shielded arc welding in the vertical direction of a thick steel material, in order to obtain the desired mechanical characteristic in a weld metal and a heat affected part, and to realize high efficiency of welding, it is set as narrow line and the welding amount. It was found that it is important to control the amount of heat input for welding per pass and to control the welding depth (welding depth) in the predetermined range while reducing the pressure.

Thus, the inventors have further studied the welding conditions for performing the above welding. As a result, the bead shape including suppression of sagging of the molten metal which becomes a problem in vertical welding by appropriately controlling the welding conditions of the first layer, in particular, the welding torch angle and the weaving condition, by setting the improvement condition as a predetermined condition. The above-described joint depth in superlayer welding was achieved while stabilizing and preventing generation of weld defects. And by this, even if it was a thick steel material whose plate | board thickness is 40 mm or more, the knowledge that a desired mechanical characteristic was acquired and it became possible to perform high quality and highly efficient vertical direction narrowing gas shielded arc welding was possible.

In addition, when performing the vertical gas shielded arc welding as described above, depending on the welding conditions of the final layer welding, the problem that the appearance of the bead of the welded joint finally obtained tends to deteriorate easily, the inventors have found this point. In order to solve this problem, further studies were conducted.

As a result, during the final layer welding, a cold plate capable of sliding movement in the upward direction is applied to the thick steel material as a covering material for improving the thick steel material from the welding torch side, and the cooling plate is placed in accordance with the upward movement of the welding torch. By welding while moving up, the knowledge that the beautiful bead appearance was obtained easily was acquired.

This invention is completed based on the said knowledge, after further examining.

That is, the summary structure of this invention is as follows.

1. The vertical narrowing gas shield which joins the two thick steel materials whose plate | board thickness is 40 mm or more by the improvement angle to 25 degrees or less, and the improvement gap to 20 mm or less by single layer welding or multilayer welding using weaving. In the arc welding method,

At the time of first layer welding, 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 300 kJ / cm or less, and the weaving depth in the plate thickness direction is 15 mm or more. When the weld bead width in the first layer welding is 63 mm or less and W is the maximum width of the weaving in the plate thickness direction and in the direction perpendicular to the welding line, the width of the welding torch is (W-6) mm or more and W mm or less. Weaving is carried out, and the joining depth in the superlayer welding is made 20 mm or more and 65 mm or less,

In the final layer welding, a cold plate capable of sliding movement in an upward direction is applied to the thick steel material as a covering material for improvement of the thick steel material from the welding torch side, while moving the cold plate upward in accordance with the upward movement of the welding torch. The method of vertical narrowing gas shielded arc welding which performs welding.

2. The said vertical direction narrowing gas shielded arc welding method as described in said 1 in the weaving of superlayer welding WHEREIN: The weaving pattern of the welding torch seen from the welding line direction is a U-shape.

3. The said vertical direction narrowing gas shielded arc welding method as described in said 1 or 2 whose sum of S amount and O amount of the weld metal in the said superlayer welding is 450 mass ppm or less, and N amount is 120 mass ppm or less.

4. The vertical direction narrowing gas shielded arc welding method in any one of said 1-3 whose sum total of Si amount and Mn amount of the welding wire used by said superlayer welding is 1.5 mass% or more and 3.5 mass% or less.

5. The method for vertical narrowing gas shielded arc welding as described in any one of said 1-4 whose sum total of Ti amount, Al amount, and Zr amount of the welding wire used by said superlayer welding is 0.08 mass% or more and 0.50 mass% or less.

6. The vertical narrow narrow gas shielded arc welding method according to any one of 1 to 5 above, wherein a gas containing 20 vol% or more of CO ₂ gas is used as the shield gas of the superlayer welding.

7. The method for vertically narrowing gas shielded arc welding in any one of said 1-6 whose average welding current of said superlayer welding is 270 A or more and 360 A or less.

According to the present invention, even when welding a thick steel material having a plate thickness of 40 mm or more, high quality and high quality, while preventing bead-shaped stabilization and welding defects including suppressing sagging of molten metal, which is a problem in vertical welding, is prevented. Efficient narrowing gas shielded arc welding can be performed.

In addition, the welding method of the present invention has a smaller welding amount than conventional gas shielded arc welding, and can also achieve energy saving due to high efficiency of welding. Thus, the welding construction cost can be significantly reduced. It is possible to obtain a beautiful bead appearance easily.

1 shows examples of various improved shapes.
FIG. 2: shows the example of the construction method at the time of constructing superlayer welding by the welding method which concerns on one Embodiment of this invention in V-shaped improved shape.
FIG. 3: shows the example of the improved cross section after performing superlayer welding by the welding method which concerns on one Embodiment of this invention in V-shaped improved shape.
Fig. 4 shows an example of the weaving pattern of the welding torch seen from the welding line direction in the weaving of the first layer welding, wherein (a) is a U-shape, (b) is a trapezoid, (c) is a V-shape, and (d) It's a triangle.
FIG. 5: shows in figure an example of the construction method at the time of constructing final layer welding by the welding method which concerns on one Embodiment of this invention.
6 is a photograph after performing superlayer welding in Inventive Example (No. 7), wherein (a) shows the overall appearance and (b) shows an improved cross section.

Hereinafter, the present invention will be described in detail.

(A)-(c) of FIG. 1 shows an example of various improvement shapes. In the figure, reference numeral 1 denotes an improved surface of the thick steel, divalent thick steel, and 3 represents an improvement of the lower end of the steel (in the Y-shaped improvement), the angle of improvement is represented by the symbol θ, the gap is represented by G, and the plate thickness is t. Denotes the improvement height of the steel lower end portion (in the Y-type improvement).

As shown in the figure, the improved shape targeted here can be either V type improvement (including type I improvement and レ type improvement) and Y type improvement, and are shown in Fig. 1C. As described above, it is also possible to achieve a Y-stage improvement in multiple stages.

In addition, as shown to (b) and (c) of FIG. 1, the improvement angle and improvement gap in case of Y type improvement are set as the improvement angle and improvement gap in improvement of a steel lower end part. Here, the improvement of the lower end of the steel means an area from the steel surface which becomes the back surface (the surface on the welding device (welding torch) side to the surface and the surface on the opposite side to the back surface) at the time of welding from about 20 to 40% of the plate thickness. Means.

Moreover, FIG. 2 shows the construction method at the time of constructing superlayer welding by the welding method which concerns on one Embodiment of this invention in the V-shaped improvement shape. In the figure, 4 is a welding torch, 5 is a welding wire, 6 is a backing strip material, and (phi) is an angle of a welding torch with respect to a horizontal direction. In addition, illustration is abbreviate | omitted about a welding line, a molten paper, and a welding bead.

Here, as shown in FIG. 2, the present welding method advances gas shielded arc welding in which two thick steels of a predetermined plate thickness are faced to each other and these thick steels are joined by vertical welding using weaving. It is based on an upward welding with the direction upward.

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

3 shows the improved cross section after performing superlayer welding by the welding method which concerns on one Embodiment of this invention in V-shaped improved shape. In the figure, reference numeral 7 denotes a welding bead (welding bead in the first layer welding), the symbol D denotes the joint depth in the first layer welding, and the W bead width in the first layer welding (the gap between the improvement after the first layer welding). Indicates.

In addition, the joining depth D in the first layer welding is the minimum value of the weld bead height in the first layer welding in the case where the steel surface serving as the back surface at the time of welding is used as the starting point (the lower layer (lower) closest to the starting steel surface). Weld bead height in welding).

Here, although the V shape improvement shape was shown as an example, D and W are the same also in another improvement shape.

Next, in the welding method of this invention, the reason which limited the bottom part improvement angle, the bottom part gap, and the plate | board thickness of steel materials to the said range is demonstrated.

Improvement angle θ: 25 ° or less

The smaller the improved part of the steel, the faster and more efficient welding is possible, while defects such as poor fusion are likely to occur. Moreover, welding when the improvement angle exceeds 25 degrees can also be implemented with the conventional construction method. For this reason, in this invention, when the construction is difficult by the conventional construction method and further high efficiency is anticipated, it aims at the case where the improvement angle: 25 degrees or less.

In addition, in V type improvement, when the improvement angle is 0 degree, it is called so-called I type improvement, and when it is 0 degree in terms of welding amount, it is most efficient, and the improvement angle may be 0 degree (I type improvement), Since the improvement is closed during welding due to the welding heat deformation, it is preferable to set the improvement angle according to the plate thickness t (the improvement height h of the lower end of the steel in the case of Y-shaped improvement). .

Specifically, the improvement angle is preferably (0.5 x t / 20) ° or more and (2.0 x t / 20) ° or less, more preferably (0.8 x t / 20) ° or more, (1.2 x t / 20) degrees or less. For example, when plate | board thickness t is 100 m, the improvement angle is 2.5 degrees or more and 10 degrees or less are preferable, More preferably, it is 4 degrees or more and 6 degrees or less.

However, when the plate | board thickness t exceeds 100 mm, the upper limit of a preferable range will exceed 10 degrees, but the upper limit of a preferable range in this case shall be 10 degrees.

Improvement gap G: 20 mm or less

The smaller the steel improvements, the faster and more efficient the welding is possible. Moreover, in the case where the improvement gap exceeds 20 mm, the molten metal tends to be liable and construction is difficult. As a countermeasure, the welding current needs to be kept low, but welding defects such as slag mixing tend to occur. Therefore, the improvement gap is intended for the case of 20 mm or less. Preferably they are 4 mm or more and 12 mm or less.

Plate thickness (t): 40 mm or more

The plate thickness of steel is 40 mm or more. This is because if the plate thickness of steel materials is less than 40 mm, even if it uses the conventional welding method, for example, electrogas arc welding of patent document 4, a big problem does not arise in the performance, such as the strength and toughness of a joint. to be.

In addition, in the case of using a general rolled steel material, the plate thickness is generally the upper limit of 100 mm. Therefore, it is preferable to make the plate | board thickness of steel materials into 100 mm or less. Moreover, in the case of single layer welding, it is preferable to set it as 65 mm or less.

In addition, the steel to be used as the welded material is particularly preferably high tensile strength steel (for example, ultra-fine YP460 MPa steel (tensile strength 570 MPa steel) or construction TMCP steel SA440 (tensile strength 590 MPa steel)). . The high tensile strength of steel is severe in welding heat input limitation, and it is not easy to generate cracks in the weld metal, and thus the joint strength and toughness required by the welding heat influence are not obtained. In contrast, in the welding method of the present invention, welding can be efficiently performed at a heat input amount of 300 kJ / cm or less, and welding of a 590 MPa class high tensile strength steel sheet and a 590 MPa class corrosion resistant steel which is a high alloy system is also possible. Naturally, it can cope with mild steel without any problem.

As mentioned above, although the reason which limited the improvement angle, the improvement gap, and the plate | board thickness of steel materials was demonstrated in the welding method of this invention, in the welding method of this invention, the heat input amount suitable for the above-mentioned improved shape and plate | board thickness of the steel materials. In order to weld efficiently, it is important to make the junction depth in superlayer welding into a predetermined range, controlling a superlayer welding condition suitably.

Hereinafter, the reason for limitation of the junction depth in these superlayer welding and the superlayer welding conditions are demonstrated.

Bonding depth D in superlayer welding: 20 mm or more and 65 mm or less

Plate thickness: In order to weld a thick steel material of 40 mm or more especially by multi-layer welding of 2 passes or more, it is necessary to make the joining depth in superlayer welding more than 20 mm. If the welding depth in the first layer welding is less than 20 mm, the heat of welding is concentrated, so that the molten metal sags. On the other hand, when the joint depth in superlayer welding exceeds 65 mm, not only the welding heat input becomes easy to be excessive, but also welding defects such as high temperature cracking, poor fusion of an improved surface due to dispersion of heat during welding, and slag mixing. This happens. Therefore, the joining depth in superlayer welding shall be 20 mm or more and 65 mm or less. Preferably they are 25 mm or more and 60 mm or less. In the case of single layer welding, the joint depth D in the initial layer welding is about the same as the plate thickness (40 mm or more).

Angle of welding torch (tip of feed tip) φ: 25 ° or more and 75 ° or less with respect to the horizontal direction

By making the angle of the welding torch closer to the horizontal than the vertical, the arc becomes the back side of the welding bead surface, and the sagging of the molten metal can be suppressed. Here, when the angle of a welding torch is less than 25 degrees with respect to a horizontal direction, formation of a welding bead is difficult. On the other hand, when the angle of a welding torch exceeds 75 degrees with respect to a horizontal direction, it becomes difficult to suppress slack of molten metal. Therefore, the angle of a welding torch needs to be 25 degrees or more and 75 degrees or less with respect to a horizontal direction. Preferably it is 30 degrees or more and 45 degrees or less.

Weld heat input: 30 kJ / cm or more and 300 kJ / cm or less

In multilayer welding, by increasing the heat input amount (= welding amount) per one pass, the number of passes can be reduced, and weld lamination defects can be reduced. However, when the amount of heat input of the weld is too large, it becomes difficult to secure the strength and toughness of the weld metal, and it becomes difficult to secure the toughness by suppressing softening of the steel heat affected zone and coarsening of grains. In particular, when the weld heat input exceeds 300 kJ / cm, in order to secure the properties of the weld metal, a dedicated wire in consideration of steel dilution becomes indispensable, and in steel materials, a steel material of a design that can withstand the heat input of the weld is required. On the other hand, in order to secure a molten metal and obtain a weld part without welding defects, it is advantageous to have a large amount of welding heat input. If the welding mouth gap is less than 30 kJ / cm in the narrowing line, the melting of the improved surface is insufficient, resulting in lamination defects. Occurrence is inevitable.

Therefore, welding heat input amount shall be 30 kJ / cm or more and 300 kJ / cm or less. Preferably it is 90 kJ / cm or more and 280 kJ / cm.

Weaving depth (L) in the plate thickness direction in the weaving of the welding torch: 15 mm or more and 63 mm or less

Although this welding method performs the weaving of a welding torch, the weaving depth L in the plate thickness direction in the weaving of this welding torch, and the maximum width of the weaving in the plate thickness direction mentioned later and the direction orthogonal to a welding line (M). It is important to control it properly.

In addition, the weaving depth L in the plate | board thickness direction in various weaving patterns, and the weaving maximum width M in the plate | board thickness direction and the direction orthogonal to a welding line are shown to (a)-(d) of FIG. Become together.

Here, in the vertical upward welding based on the present welding method, the joining depth and the weaving width in the plate thickness direction are about the same. For this reason, when the weaving depth in a plate thickness direction is less than 15 mm, it is difficult to make the joining depth in superlayer welding into 20 mm or more. On the other hand, when the weaving depth in a plate | board thickness direction exceeds 63 mm, it becomes difficult to make the joining depth in superlayer welding into 65 mm or less. Furthermore, in addition to the excessive heat input of the welding, it becomes difficult to obtain desired mechanical properties in the heat affected zone of the weld metal or steel material, and high temperature cracking or poor fusion of the improved surface due to dispersion of heat during welding. Welding defects, such as slag mixing, tend to occur.

Therefore, the weaving depth in the plate thickness direction is made into 15 mm or more and 63 mm or less. Preferably they are 25 mm or more and 60 mm or less.

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

In order to prevent the unmelting of the improved surface, it is necessary to set the maximum width of the weaving in the direction perpendicular to the plate thickness direction and the weld line (W-6) mm or more. On the other hand, when the maximum width of the weaving in the plate thickness direction and in the direction perpendicular to the weld line exceeds W mm, the molten metal is stretched and welding is not established.

Therefore, the maximum width of the weaving in the plate thickness direction and in the direction perpendicular to the weld line is in the range of (W-6) mm or more and W mm or less. Preferably it is (W-4) mm or more and (W-1) mm or less.

In the case of single layer welding, W is the improvement width in the steel surface which becomes a surface (surface on the welding apparatus (welding torch) side) at the time of welding.

Moreover, the weaving pattern of a welding torch is not specifically limited, As shown to Fig.4 (a)-(d), it is a co-shape seen from the welding line direction (it corresponds with the welding progress direction, and is normally a perpendicular direction), V-shaped, trapezoidal, triangular, or the like. In addition, the locus of the welding torch at each point (point B and point C in FIG. 4A) in which the direction of the welding torch changes in FIGS. 4A to 4D may be uneven, It may be rounded.

However, in the vertical upward welding, the weaving at a point near the welding surface side tends to cause the molten metal to drop. Moreover, when a welding torch operation | deviates from an improvement surface, uniform melting of an improvement surface is not obtained and welding defects, such as a fusion defect, are easy to generate | occur | produce. In particular, the general trapezoidal and triangular weaving pattern which does not require the inversion operation has a small device load, while the welding torch operation at a point near the welding surface side (D of the trapezoidal weaving pattern in Fig. 4B). The point → A point, C point → A point of the triangular weaving pattern in FIG. For this reason, it is preferable to set it as the U-shape or V-shape weaving pattern which does not have the torch operation | movement at the welding surface side from a viewpoint of suppressing dripping of molten metal.

In the V-shaped or triangular weaving pattern, when the improvement gap is large (for example, 6 mm or more), the welding torch operation is shifted from the improvement surface (for example, A point in FIG. 4C). ¡Æ in the operation of point B, the trajectory of the tip of the welding torch is not parallel to the improved surface (near the welding torch), and uniform melting of the improved surface is not obtained, resulting in welding defects such as poor fusion. It becomes easy to do it. Therefore, in such a case, it is most preferable to set it as a U-shaped weaving pattern which can operate a welding torch parallel to an improvement surface.

In addition, the deepest point of the tip of the welding torch during weaving in the plate thickness direction (for example, B and C points in FIGS. 4A and 4B, 4C, and 4 The distance (a) from the steel back surface of point B) in d) is about 2-5 mm normally.

In addition, when the Ko-shaped weaving and the trapezoidal weaving are applied to the above-described improved shape, M ₁ , M ₂ , and M ₃ in FIGS. 4A and 4B are 2 to 18 mm and 0 to 10 mm, respectively. , About 0 to 10 mm.

In addition, the frequency at the time of weaving and stop time (stop time in each point, such as A point shown in FIG. 4) are not specifically limited, For example, a frequency is 0.25-0.5 Hz (preferably 0.4 Hz or more, 0.5 ms or less), and a stop time may be made into about 0 to 0.5 second (preferably 0.2 second or more and 0.3 second or less).

As mentioned above, although basic conditions were demonstrated, in the welding method of this invention, by satisfying the following conditions further, the fall of the molten metal which becomes a problem especially in a vertical direction welding can be suppressed, and stabilization of the bead shape can be further aimed at. Can be.

Total amount of S content and O amount of weld metal in superlayer welding: 450 mass ppm or less

In order to realize a stable vertical upward welding, it is necessary to prevent sagging of the molten metal and to obtain a stable welding bead shape (smooth bead without irregularities), and in particular, in order to prevent sagging of the molten metal, It is important to manage the amount of S and O lowering surface tension and viscosity.

In addition, when the total amount of S and O amounts of the weld metal exceeds 450 mass ppm (hereinafter also referred to simply as ppm), convection of the weld metal becomes outward on the surface in addition to the decrease in surface tension and viscosity, The weld metal is convexed from the center toward the periphery, the molten metal spreads, and sagging of the molten metal tends to occur. For this reason, it is preferable to make S amount and O amount of the weld metal which dominate the surface tension, viscosity, and flow of molten metal into 450 ppm or less in these total amounts. More preferably, it is 400 ppm or less. The lower limit is not particularly limited, but is preferably 15 ppm.

Moreover, S is contained 0.010-0.025 mass% normally in the welding wire in order to lower surface tension and planarize a welding bead. In order to reduce the amount of S of the weld metal, in addition to the reduction of the amount of S of the welding wire itself, it is effective to lower the amount of S in the steel.

In addition, the O amount of the weld metal increases by oxidation of CO _{2 in} the shield gas. For example, if you use 100 volume% CO ₂ gas as a shielding gas, O content in the weld metal, it is increased by 0.040 ~ 0.050 wt%. In order to reduce the amount of O of such a weld metal, addition of Si and Al to a welding wire is effective in addition to the reduction of O normally contained in about 0.003-0.006 mass% in the welding wire itself. In addition, it is also effective to increase the welding current and the arc voltage so as to sufficiently perform slag metal reaction (deoxidation reaction) in the molten metal, flocculation of the slag, and floating on the weld bead surface.

N content of weld metal in superlayer welding: 120 ppm or less

Nitrogen (N) in the weld metal is discharged from the weld metal at the time of solidification to form bubbles. Generation of this bubble causes vibration of the hot water surface, which causes sagging of the molten metal. In particular, when the amount of N in the weld metal exceeds 120 ppm, the molten metal is liable to be easily generated. Therefore, the amount of N in the weld metal in the first layer welding is preferably 120 ppm or less. More preferably, it is 60 ppm or less. The lower limit is not particularly limited, but is preferably 15 ppm.

Moreover, normally, welding wire contains 50-80 ppm of nitrogen (N) as an impurity, and from this, the amount of N in a welding metal increases about 20-120 ppm by mixing of impurity of shield gas and air | atmosphere. On the other hand, since the nozzle inner diameter of arc welding is about 16-20 mm normally, it is difficult to completely shield the weld metal part used as such a nozzle, and to become the joint depth exceeding this nozzle internal diameter, As a result, welding The amount of N in the metal may exceed 200 ppm.

In order to prevent such an increase in the amount of N and to make the amount of N of the weld metal in the first layer welding to 120 ppm or less, or even 60 ppm or less, a gas shield system different from a normal arc welding nozzle is provided. Thereby, it is effective to suppress mixing of the atmosphere with the weld metal.

In addition, since S, O, and N elute from the steel to the weld metal by the steel dilution at the time of welding, S: 0.005 mass% or less, O: 0.003 mass% or less, and N: 0.004 mass% or less The thing is preferable in suppressing S amount, O amount, and N amount of the weld metal in said superlayer welding.

The total amount of Si and Mn in the welding wire used in superlayer welding: 1.5% by mass or more and 3.5% by mass or less

In order to prevent sagging of the molten metal and to obtain a stable weld bead appearance, it is important to form an appropriate amount of slag. The slag is mainly composed of SiO ₂ and MnO, and the amount of slag depends largely on the sum of the Si amount and the Mn amount of the welding wire.

Here, when the sum total of Si amount and Mn amount of a welding wire is less than 1.5 mass%, the slag amount sufficient in order to prevent sagging of molten metal may not be obtained. On the other hand, when the sum total of Si amount and Mn amount of a welding wire exceeds 3.5 mass%, slag may become agglomeration and may interfere with welding after the next layer. Therefore, it is preferable that the sum total of Si amount and Mn amount of the welding wire used for superlayer welding shall be 1.5 mass% or more and 3.5 mass% or less. More preferably, they are 1.8 mass% or more and 2.8 mass% or less.

The total amount of Ti, Al and Zr in the welding wire used in superlayer welding: 0.08 mass% or more and 0.50 mass% or less

TiO ₂ , Al ₂ O ₃ and Zr ₂ O ₃ have a significant effect on the slag physical properties (viscosities), which play an important role in preventing sagging of the molten metal and obtaining a stable weld bead appearance. .

Here, if the sum total of Ti amount, Al amount, and Zr amount of a welding wire is less than 0.08 mass%, the viscosity of slag effective in preventing the molten metal from drooping is not obtained. On the other hand, when the sum total of Ti amount, Al amount, and Zr amount of a welding wire exceeds 0.50 mass%, both slag removal and remelting will become difficult, and there exists a possibility that it may interfere with welding after the next layer.

Therefore, it is preferable that the sum total of Ti amount, Al amount, and Zr amount of the welding wire used for superlayer welding shall be 0.08 mass% or more and 0.50 mass% or less. More preferably, they are 0.15 mass% or more and 0.25 mass% or less.

In addition, what is necessary is just to select suitably the components of the welding wire of that excepting the above according to the component of the after-steel material to weld, but from a viewpoint of suppressing S amount, O amount, and N amount in said welding metal, S: 0.03 mass Welding wire made into% or less, O: 0.01 mass% or less, N: 0.01 mass% or less, Si: 0.05-0.80 mass%, Al: 0.005-0.050 mass% (for example, JIS Z 3312 YGW18 or JIS Z 3319 YFEG-22C, etc.) is preferable.

Shield gas composition: 20 vol% or more of CO ₂ gas

The penetration of the weld is governed by the gouging effect due to the arc itself and the convection of the weld metal in the high temperature state. When the convection of the weld metal is inward, the penetration just under the arc increases because the hot weld metal is convection from top to bottom. On the other hand, when the convection of the weld metal is outward, the hot weld metal is convexed from the center to the left and right directions, the weld bead spreads and the penetration of the improved surface increases. Therefore, in the vertical multi-layer gas shielded arc welding of thick steel, which is the object of the present invention, in order to suppress the slack of the molten (welded) metal and obtain a uniform weld bead shape, it is preferable to make the convection of the weld metal inward. Do.

Here, from the viewpoint of reducing the oxygen (O) that dominates the flow of the weld metal, it is advantageous to suppress the CO ₂ gas low, while on the other hand, the CO ₂ gas is constricted by the dissociation endothermic reaction, There is an effect of making the convection of the weld metal more inward.

Therefore, the shielding gas composition, it is preferable that the CO ₂ gas to more than 20% by volume. More preferably, it is 60 volume% or more. In addition, the remainder other than the CO ₂ gas may be an inert gas such as Ar. In addition, CO ₂ gas: or it may be 100% by volume.

Moreover, penetration of a weld part is influenced also by the directivity of an arc and a gouging effect. Therefore, what is necessary is just to set the polarity of welding according to the characteristic of a welding material.

The conditions other than the above need not be specifically defined, but the melting point is small at the average welding current of less than 270 A, and the surface side is in the same state as the multi-layer welding in which the melting and solidification are repeated for each torch weaving, resulting in poor fusion and slag mixing. easy to do. On the other hand, when the average welding current exceeds 360 A, sagging of the molten (welding) metal is more likely to occur, and it becomes difficult to identify the arc point by the welding fume and the sputtering, making adjustment during construction difficult. For this reason, it is preferable that average welding current shall be 270-360A. Moreover, by setting average welding current to 270-360A, since the stable penetration can be obtained, suppressing generation | occurrence | production of welding fume and sputter | spatter, it becomes further advantageous in implementing this welding method.

About conditions other than this, it should follow a normal method, For example, welding voltage: 32-37V (rise with an electric current), welding speed (upward): 2-15 cm / min (preferably 4 cm / min or more) , 9 cm / min or less), wire protrusion length: 20 to 45 mm, wire diameter: 1.2 to 1.6 mm.

As mentioned above, although the first layer welding condition was demonstrated, in the vertical narrow-line gas shielded arc welding method of this invention, as shown in FIG. 5, at the time of final layer welding, it is to the thick steel material 1 from the welding torch 4 side. As a surface strip for improving the thick steel material 1, the welding is performed while the cooling plate 8 is moved upward in accordance with the upward movement of the welding torch 4. It is important. Thereby, it becomes possible to obtain the beautiful bead appearance easily. In addition, in FIG. 5, illustration of the molten paper and the welding bead in final layer welding is abbreviate | omitted.

Here, as a cooling plate, the metal plate (copper strip) made from water-cooled copper is preferable. Moreover, from a viewpoint of workability, it is preferable to make length in a cooling plate upstream direction (welding line direction) into 0.4-2.0 times the length of a thick steel material.

In addition, the welding conditions in each welding layer other than the above-mentioned are not specifically limited, For example, like welding of a superlayer, what is necessary is just to perform the welding by performing the weaving according to the junction depth. In this case, welding conditions, such as a welding current, a welding voltage, and the wire to be used, may be the same as that of the first layer welding.

Moreover, it is preferable that the number of lamination | stacking until completion of welding shall be about 2-4 layers from a viewpoint of preventing a lamination | stacking defect. In the case of single layer welding, initial layer welding becomes final layer welding.

Example

The two upward steel shields of the improved shape shown in Table 1 were subjected to a vertical upward gas shielded arc welding of the narrow line under the welding conditions shown in Table 2.

Here, all steel materials used were S: 0.005 mass% or less, O: 0.003 mass% or less, and N: 0.004 mass% or less. In addition, gas cutting was used for the improvement process of steel materials, and the improvement surface, such as grinding, was not performed.

In addition, the welding wire used the solid wire of 1.2 mm (phi) which is grade for steel materials strength or one rank higher than it. In addition, the component composition in the used welding wire was S: 0.005 mass% or less, O: 0.003 mass% or less, N: 0.005 mass% or less, Si: 0.6-0.8 mass%, Al: 0.005-0.030 mass%.

The welding current is 200 to 380 A, the welding voltage is 28 to 37 V (rising with the current), the average welding speed is 2.3 to 15.0 cm / min (adjusted during welding), and the average wire protrusion length is 30 mm. , Welding length was 400 mm. Except No. 11, a gas shield system different from the normal arc welding nozzle was provided to perform welding.

Further, Nos. 1 to 19 are multi-layer welding, and even in welding in each layer other than the first layer, a gas shielded arc in which weaving is applied with a welding current in the range of 270 to 330 A and a welding voltage of 28 to 37 V. Welding was performed and the welding joint was finished. In addition, No. 20 completed the welding joint as single layer welding. In addition, in Nos. 1 to 14 and Nos. 19 to 20, a water-cooled copper metal plate capable of slidingly moving in the upward direction as a covering material for improvement of the thick steel material from the welding torch side to the thick steel material at the time of final layer welding ( Copper strips), and the welding was performed while the metal plate was moved upward in accordance with the upward movement of the welding torch. On the other hand, in Nos. 15 to 18, welding was performed without using such a water-cooled copper metal plate at the time of final layer welding.

After the first layer welding, the bead width and the junction depth were measured by observing five sections of arbitrarily selected cross-sectional macrostructures. In addition, about the bead width, the maximum value of the measured value was made into the bead width W in superlayer welding, and about the junction depth, the minimum value of the measured value was made into the junction depth D in superlayer welding. .

Moreover, the droop of the molten metal at the time of superlayer welding was visually evaluated as follows.

◎: No sagging of the weld metal

○: less than two points of sagging of the weld metal

(Triangle | delta): 3 points or more and 4 points or less

×: 5 points or more of sagging weld metal, or welding stop

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

◎: no detection defect

(Circle): detect only the pass defect whose defect length is 3 mm or less

X: Defect which defect length exceeds 3 mm is detected

In addition, the bead surface of the welded joint finally obtained was visually inspected and evaluated as follows.

(Circle): The irregularities of the bead surface are small, and there is enough gloss

×: Big unevenness of the bead surface

These results are written together in Table 2.

As shown in Table 2, in Nos. 1 to 14 and 19 to 20 which are invention examples, although there was no sagging of the first layer weld metal, there were no more than two points. In addition, even in the ultrasonic flaw detection, there was no detection defect or the defect length was 3 mm or less. Moreover, in these invention examples, in the finally obtained melting-point joint, the unevenness | corrugation of the bead surface was small, and the beautiful bead appearance was obtained.

On the other hand, No.15-18 which is a comparative example had the welding metal of five or more points dripping, or the defect whose defect length was more than 3 mm was detected in the ultrasonic flaw inspection. Moreover, in Nos. 15-18 which welded without using a water-cooled copper metal plate at the time of final-layer welding, in the weld joint finally obtained, the unevenness | corrugation of the bead surface was large and sufficient glossiness was not obtained.

In addition, the external photograph of the front side (welding construction side) after the first layer welding of No. 7 which is the invention example in FIG. 6A is shown in FIG. From the figure, in the example of invention of No. 7 which controlled the weaving conditions etc. suitably, it turns out that the junction depth D in superlayer welding is about 28 mm, and the desired junction depth is obtained. At the same time, a stable weld bead shape was also obtained.

1: thick steel
2: improved surface of thick steel
3: Improvement of lower part of steel
4: welding torch
5: welding wire
6: backing strip material
7: welding bead (welding bead in superlayer welding)
8: cold plate
θ: improvement angle
G: improvement gap
h: improvement height of steel bottom part
t: plate thickness
φ: angle of the welding torch relative to the horizontal direction
D: Bonding depth in superlayer welding
W: Weld bead width in superlayer welding
L: Weaving depth in the plate thickness direction
M: Maximum weaving width in the direction of plate thickness and in the direction perpendicular to the weld line

Claims (7)

Vertical angle narrowing gas shield arc welding method which joins the two thick steel materials whose plate | board thickness is 40 mm or more by the improvement angle to 25 degrees or less, and the improvement gap is 20 mm or less by single layer welding or multi-layer welding using weaving. To
At the time of first layer welding, 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 300 kJ / cm or less, and the weaving depth in the plate thickness direction is 15 mm or more. 63 mm or less, and in the case where the weld bead width in the first layer welding is W, the maximum width of the weaving in the plate thickness direction and in the direction perpendicular to the weld line is (W-6) mm or more and W mm or less and 2 mm or more. Weaving of the welding torch is performed, and the joining depth in the first layer welding is made 20 mm or more and 65 mm or less,
In the final layer welding, a cold plate capable of sliding movement in an upward direction is applied to the thick steel material as a covering material for improvement of the thick steel material from the welding torch side, while moving the cold plate upward in accordance with the upward movement of the welding torch. Welding,
Vertical stenosis gas shielded arc welding method. The method of claim 1,
In the weaving of the first layer welding, the vertical narrowing line gas shielded arc welding method in which the weaving pattern of the welding torch viewed from the welding line direction is a U shape. The method according to claim 1 or 2,
The method for vertically narrowing gas shielded arc welding in which the sum total of S amount and O amount of the weld metal in said superlayer welding is 450 mass ppm or less, and N amount is 120 mass ppm or less. The method according to claim 1 or 2,
The vertical direction narrowing gas shielded arc welding method whose sum total of Si amount and Mn amount of the welding wire used by said superlayer welding is 1.5 mass% or more and 3.5 mass% or less. The method according to claim 1 or 2,
A method for vertical narrowing gas shielded arc welding, wherein the total amount of Ti, Al and Zr in the welding wire used in the superlayer welding is 0.08% by mass or more and 0.50% by mass or less. The method according to claim 1 or 2,
The chocheung as shielding gas in the welding, a method improving the vertical direction narrow gas shielded arc welding using a gas containing at least 20 vol.% CO ₂ gas. The method according to claim 1 or 2,
The method for vertical narrowing gas shielded arc welding whose average welding current of said superlayer welding is 270 A or more and 360 A or less.

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