Inclined narrow groove welding method

Abstract

To efficiently perform sound welding by suppressing weld defects while suppressing a welding amount and preventing the occurrence of high temperature cracks in flat position welding.SOLUTION: In a narrow groove 50 of horizontal welding, a lower groove angle θ on a lower plate 5A side is set to 35 ° to 45 ° upward from the horizontal, and an upper groove angle α is set to be larger than the lower groove angle θ in a range of 2 ° to 5 °. In the inclined narrow groove welding method, a root gap RG of a narrow groove 50 is set in a range of 9 mm-12 mm, a backing metal 6 is provided which is attached to a lower plate 5A and an upper plate 5B and positions a groove surface lower end part 5A of the upper plate 5B and sets a groove angle and the root gap RG, a contact tip having a wire hole for feeding a weld wire into the narrow groove 50 is inserted, and the lower plate 5A and the upper plate 5B are welded without rotating the contact tip around a nozzle shaft in one pass in the narrow groove 50.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an inclined narrow groove welding method. [Background technology]

[0002] BACKGROUND ART Conventionally, in carbon dioxide gas arc welding, a horizontal welding method is known that shortens the positioning time and welding time of workpieces to be welded in horizontal welding and reduces welding defects (see, for example, Patent Document 1). Patent Document 1 describes a method of welding in a horizontal position, in which the groove angle on the lower plate side of the groove is set 35 to 55 degrees upward from the horizontal, and the groove angle on the upper plate side is made parallel to the lower plate side to reduce the groove cross-sectional area, and a contact tip with an eccentric hole is inserted into this groove, and the contact tip is rotated to rotate the tip of the welding wire passing through the contact tip, thereby rotating the arc at high speed and welding one layer at a time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-206827 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional horizontal welding methods using carbon dioxide gas arc welding generally involve multi-pass welding with a 35° bevel, so there is a need for a welding method that can reduce the amount of welding, weld more efficiently, and reduce welding defects, and there is room for improvement in this regard.

[0005] The present invention was made in consideration of these circumstances, and its purpose is to provide an inclined narrow groove welding method that can efficiently perform sound welding with reduced welding defects by reducing the amount of welding in downward welding and enabling single-pass welding of the inside of the groove in one layer while preventing the occurrence of hot cracking. [Means for solving the problem]

[0006] (1) Aspect 1 of the inclined narrow gap welding method according to the present invention is an inclined narrow gap welding method in which welding is performed at an angle using carbon dioxide gas arc welding, and includes the steps of: setting the lower groove angle of the narrow groove of the horizontal welding on the lower plate side to 35 to 45 degrees upward from the horizontal; setting the upper groove angle on the upper plate side to be larger than the lower groove angle by 2 to 5 degrees; and setting the root gap of the narrow groove in the range of 9 to 12 mm. Burn-through prevention members are attached to the lower plate and the upper plate, and position the lower end of the groove surface of the upper plate, set the groove angle and the root gap, and prevent burn-through of molten metal. a contact tip having a wire hole for feeding welding wire into the narrow groove, and is inserted into the narrow groove; the lower plate and the upper plate are welded in one layer, one pass, inside the groove, without rotating the contact tip about the nozzle axis. A backing plate is attached to the lower plate and the upper plate, and positions the lower end of the groove surface of the upper plate and sets the groove angle and the root gap. A contact tip having a wire hole for feeding welding wire into the narrow groove is inserted into the narrow groove, and the lower plate and the upper plate are welded in one pass, without rotating the contact tip about the nozzle axis.

[0007] According to the first aspect of the inclined narrow gap welding method of the present invention, the lower groove angle on the lower plate is set to 35 to 45 degrees upward from the horizontal, and the root gap of the narrow groove is set in the range of 9 to 12 mm, which results in downward welding inside the groove (within the plate thickness) and horizontal welding near the surface, making the welding work easier. Furthermore, by setting the welding conditions in this way, the cross-sectional area of ​​the groove can be reduced, the amount of welding can be reduced, the occurrence of hot cracking can be prevented, and single-layer single-pass welding can be made possible. In addition, in the present invention, the upper groove angle is set to be larger than the lower groove angle by 2 to 5 degrees, resulting in a narrow groove, which makes it easier to see the target position at the tip of the groove. Furthermore, the degree of freedom in the movable range of the contact tip within the narrow groove can be ensured, improving welding workability. Furthermore, since the increase in the amount of welding, which occurs when the upper groove angle is larger than the lower groove angle by more than 5 degrees, can be prevented, the amount of welding wire, carbon dioxide, and electricity used can be reduced.

[0008] In this way, by performing welding under the above-mentioned welding conditions, it is possible to perform single-pass welding in one layer inside the groove, which shortens the welding time compared to multi-pass welding, efficiently suppresses welding defects, and produces sound welding with high quality. Therefore, this welding method is suitable for factory welding and on-site welding work for steel building columns, steel bridge legs, steel towers, etc.

[0009] Furthermore, in the present invention, compared to the conventional horizontal welding current for a 35° V-groove (e.g., 240 A to 300 A, φ1.4 mm), the downward groove welding (φ1.4 mm) of the present invention can be increased to approximately 365 A, allowing for more efficient welding. Furthermore, since the efficiency of the welding work can be improved as described above, the construction time required for the welding work can be reduced and the production volume can be increased. Furthermore, since the welding work is easy and simple, the welding worker does not need to have a high level of skill. Furthermore, in the present invention, welding can be performed using a general backing metal, and there is no need for a complex configuration such as dividing the metal into two parts and fixing each part to an upper plate and a lower plate, thereby simplifying the welding work. Furthermore, in the present invention, it is not necessary to rotate the contact tip around the nozzle axis, and welding can be performed using a general welding machine. Therefore, the welding device does not need to have a complex mechanism for rotating the contact tip, and operation control during welding is easy, allowing for high-quality welding.

[0010] (2) In a second aspect of the present invention, in the inclined narrow gap welding method of the first aspect, it is preferable that the torch equipped with the contact tip is provided so as to be movable in the horizontal direction.

[0011] In this case, by moving the torch horizontally, blowholes that occur due to insufficient gas shielding caused by a narrow groove can be prevented.

[0012] (3) In a third aspect of the present invention, in the inclined narrow gap welding method of the first or second aspect, it is preferable that the target position of the first layer of welding at the contact tip is the lower groove.

[0013] In this case, by setting the target position of the first layer at the sharp root portion, which becomes a narrow groove at the bottom of the groove, as the lower groove, a more sound penetration can be achieved.

[0014] A fourth aspect of the present invention may be characterized in that, in the inclined narrow gap welding method of any one of the first to third aspects, the contact tip has an outer diameter of 6 mm and is insulated by being wrapped with heat-resistant insulating tape or being inserted into a ceramic tube.

[0015] In this case, it is possible to prevent the contact tip inserted into the narrow groove from coming into contact with the groove surface and causing a short circuit.

[0016] (5) A fifth aspect of the present invention may be characterized in that, in the inclined narrow gap welding method of any one of the first to fourth aspects, a torch equipped with the contact tip is mounted on a welding device having a vertical and forward / backward movement distance of 30 cm, the horizontal movement speed of the contact tip of the torch is set to 15 cm / min to 65 cm / min, the torch angle is 0 degrees to 50 degrees, and the retraction angle is 0 degrees to 10 degrees.

[0017] In this case, by setting the operating conditions of the torch provided in the welding device as described above, it is possible to efficiently weld the inside of the narrow groove having the above-mentioned shape. [Effects of the Invention]

[0018] The inclined narrow gap welding method of the present invention reduces the amount of welding by downward welding, and enables welding of the inside of the groove in one layer with one pass while preventing the occurrence of hot cracking, thereby enabling sound welding with efficient suppression of welding defects. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view showing an inclined narrow groove welding method according to an embodiment of the present invention. FIG. [Figure 2] 2 is a diagram for explaining the cross-sectional shape of the narrow groove shown in FIG. 1. FIG. [Figure 3] FIG. 2 is a diagram for explaining the cross-sectional shape of the narrow groove shown in FIG. 1, showing a welded state. [Figure 4] FIG. 4 is a diagram illustrating the cross-sectional shape of the narrow groove before welding in FIG. [Figure 5] 4A and 4B are cross-sectional views showing the groove shape of the first embodiment, where (a) is a diagram of a comparative example and (b) is a diagram of the embodiment. [Figure 6] FIG. 10 is a diagram showing the results of the first example, illustrating the relationship between the thickness of the steel plate and the cross-sectional area of ​​the groove. [Figure 7] 10(a) to 10(c) are cross-sectional views schematically showing the welding states of Test Examples 1 to 3 according to the second embodiment. [Figure 8]10(a) to 10(c) are cross-sectional views schematically showing the welding states of Test Examples 4 to 6 according to the second embodiment. [Figure 9] 10(a) to 10(c) are photographs of weld cross sections of Test Examples 1 to 3 according to the second embodiment. [Figure 10] 10(a) to 10(c) are photographs of weld cross sections of Test Examples 4 to 6 according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the inclined narrow gap welding method according to the present invention will be described with reference to the drawings. Note that in each drawing, the scale of each component may be appropriately changed as necessary to make each component large enough to be visible.

[0021] As shown in Figures 1 to 4, the inclined narrow gap welding method of this embodiment is a method in which a narrow groove 50 of a base material steel plate 5 is inclined using a welding device 1 and carbon dioxide arc (MAG) welding to weld the inside of the plate thickness in a one-layer, one-pass construction.

[0022] This inclined narrow groove welding method can be suitably used for steel plates 5, for example, in bridge piers, and is highly applicable to welding of on-site welds in such piers. In steel bridges, it is highly applicable to on-site welds of columns and corner welds (in factories) of columns. The steel plate 5 has a lower plate 5A and an upper plate 5B. This welding method involves welding a narrow groove 50 between the lower plate 5A and the upper plate 5B to form a welded joint in which the upper plate 5B is joined to the lower plate 5A.

[0023] The inclined narrow gap welding method according to this embodiment includes the steps of setting the lower groove angle θ of narrow groove 50 for horizontal welding on the lower plate 5A side to 35 to 45 degrees upward from horizontal, setting the upper groove angle α on the upper plate 5B side to be larger than the lower groove angle θ by 2 to 5 degrees, and setting the root gap RG of narrow groove 50 in the range of 9 to 12 mm. The lower groove angle θ is preferably 35 degrees.

[0024] In the inclined narrow gap welding method, a contact tip 22 having a wire hole 21 for feeding out a welding wire 10 is inserted into the narrow groove 50, and the inside of the groove between the lower plate 5A and the upper plate 5B is welded in a single layer, without rotating the contact tip 22 around the nozzle axis O1.

[0025] The contact tip 22 is, for example, a homemade one, and is provided on the torch 20. The contact tip 22 is a cylindrical conductor that guides the electrode wire to the welding part and supplies the welding current, and is a replaceable metal part that is fixed to the tip of the torch 20. Torch 20 is mounted on welding equipment 1 with a travel distance of 30 cm in the up-down direction Z and the front-rear direction Y (corresponding to the direction of thickness t of steel plate 5). The speed of movement of torch 20 along the groove extension direction X in the horizontal direction of contact tip 22 is set to 15 cm / min to 65 cm / min, the torch angle β is set to 0 degrees to 50 degrees, and the retraction angle β1 is set to 0 degrees to 10 degrees. Torch angle β is the inclination angle of torch 20 with respect to the horizontal direction.

[0026] 1, the welding device 1 is provided with a contact tip 22 that is movable horizontally in a groove extending direction X. Here, the groove extending direction X is a direction perpendicular to the up-down direction Z and the front-rear direction Y.

[0027] The welding device 1 has a guide rail (not shown) that extends along the groove extension direction X, and a welding head (not shown) that can travel on the guide rail. A torch 20 equipped with a contact tip 22 is integrally provided on the welding head. The welding head has a mechanism that rotates the torch 20 in the up-down direction Z, the front-back direction Y, and at a torch angle β. In other words, the torch 20 and the contact tip 22 can slide in the groove extension direction X, and can also move in the up-down direction Z and the front-back direction Y, and the torch angle β can also be changed.

[0028] The contact tip 22 has an outer diameter of 6 mm. The contact tip 22 is insulated by being wrapped with heat-resistant insulating tape (not shown) or by being inserted into a ceramic tube.

[0029] In this inclined narrow gap welding method, welding wire 10 with a wire diameter of 1.2 mm to 1.4 mm is used. In the inclined narrow gap welding method, the current value is set to 240 A to 365 A, the voltage is set to 21 V to 42 V, and the welding travel speed is set to 18 cm / min to 50 cm / min. By using these welding conditions, it is possible to more reliably prevent poor penetration and poor fusion that occur in narrow groove 50 during single-layer, single-pass welding.

[0030] In the inclined narrow gap welding method, the target position of the first layer P1 (layer indicated by reference numeral 1 in FIGS. 7 and 8) of welding is the lower groove 5b.

[0031] Furthermore, as shown in FIG. 2, in the inclined narrow gap welding method, it is preferable that the ratio (h / W) of the height h to the width W is 1.0 or less.

[0032] In the inclined narrow gap welding method, based on the above welding conditions, electricity is applied to the welding wire 10 from a power source (not shown) to generate an arc between the steel plate 5 and the welding wire 10. Then, the torch 20 is moved in the direction of travel (the direction perpendicular to the paper surface in FIG. 1) at a set moving speed. As a result, a molten pool is formed behind the arc.

[0033] Next, the operation of the inclined narrow gap welding method configured as above will be described in detail with reference to the drawings. The inclined narrow gap welding method according to this embodiment uses carbon dioxide arc welding (MAG welding) to perform welding at an angle. The inclined narrow gap welding method includes the steps of: setting the lower groove angle θ of horizontally welded narrow groove 50 on the lower plate 5A side to 35 to 45 degrees upward from the horizontal; setting the upper groove angle α on the upper plate 5B side to be larger than the lower groove angle θ by 2 to 5 degrees; and setting the root gap RG of narrow groove 50 in the range of 9 to 12 mm to prevent burn-through of the weld metal. In the inclined narrow groove welding method, a backing plate 6 is attached to a lower plate 5A and an upper plate 5B, and is provided to position the lower end 5a of the groove face of the upper plate 5B and set the groove angle and root gap RG. A contact tip 22 having a wire hole 21 for feeding out a welding wire 10 into the narrow groove 50 is inserted, and the lower plate 5A and the upper plate 5B are welded inside the groove in a single layer, single pass construction without rotating the contact tip 22 around the nozzle axis O1.

[0034] According to the inclined narrow gap welding method of this embodiment, the lower groove angle θ on the lower plate 5A is set to 35 to 45 degrees upward from horizontal, and the root gap RG of the narrow groove 50 is set in the range of 9 to 12 mm. This allows downward welding inside the groove (within the plate thickness) and horizontal welding near the surface, making welding easier. In other words, this prevents the increased welding volume and costs that would occur if the lower groove angle θ were greater than 45 degrees, and reduces the amount of shrinkage that would occur if the lower groove angle θ were less than 35 degrees, improving workability. Furthermore, this prevents the difficulties that would occur if the root gap RG were greater than 12 mm. By setting the welding conditions in this way, the cross-sectional area of ​​the groove can be reduced, the amount of welding can be reduced, the occurrence of hot cracking can be prevented, and one-layer, single-pass welding within the groove can be made possible.

[0035] In addition, in this embodiment, the upper groove angle α is set to be larger than the lower groove angle θ by 2 to 5 degrees to form a narrow groove 50, which makes it possible to favorably view the target position of the welding wire 10 at the tip of the groove. Furthermore, the degree of freedom of the movable range of the contact tip 22 within the narrow groove 50 can be ensured, thereby improving the workability of welding. Furthermore, since it is possible to prevent an increase in the amount of welding, which occurs when the upper groove angle α is larger than the lower groove angle θ by more than 5 degrees, the amounts of welding wire 10, carbon dioxide gas, and electricity used can be reduced.

[0036] In this way, by performing welding under the above-mentioned welding conditions, it is possible to perform single-pass welding in one layer inside the groove, which shortens the welding time compared to multi-pass welding, efficiently suppresses welding defects, and produces sound welding with high quality. Therefore, this welding method is suitable for factory welding and on-site welding work for steel building columns, steel bridge legs, steel towers, etc.

[0037] Furthermore, in this embodiment, compared to the conventional horizontal welding current for a 35° V-groove (e.g., 240 A to 300 A, φ1.4 mm), the downward groove welding (φ1.4 mm) of the present invention can be increased to approximately 365 A, allowing for more efficient welding.

[0038] Furthermore, in this embodiment, as described above, the efficiency of the welding work can be improved, so that the construction time required for the welding work can be reduced and the production volume can be increased.

[0039] Furthermore, in this embodiment, the welding work is easy and simple, so the welding worker does not need to have a high level of skill.

[0040] Furthermore, in this embodiment, welding can be performed using a general backing metal, and there is no need for a complex configuration such as dividing the metal into two parts and fixing each part to an upper plate and a lower plate, thereby simplifying the welding work.

[0041] Furthermore, in this embodiment, it is not necessary to rotate the contact tip 22 around the nozzle axis O1, and welding can be performed using a general welding machine. Therefore, the welding device does not need to have a complex mechanism for rotating the contact tip 22, and operation control during welding is easy, allowing for high-quality welding.

[0042] In this embodiment, the torch 20 having the contact tip 22 is preferably provided so as to be movable in the horizontal direction. Therefore, by employing a double nozzle for the electrode nozzle, it is possible to prevent blowholes that occur due to insufficient gas shielding caused by the narrow groove 50.

[0043] In addition, in this embodiment, by setting the target position of the first layer P1 at the lower groove 5b in the acute root portion that forms the narrow groove 50 at the groove bottom, it is possible to achieve a more sound penetration.

[0044] In this embodiment, the contact tip 22 is set to have an outer diameter of 6 mm, and is insulated by being wrapped with heat-resistant insulating tape (not shown) or by being inserted into a ceramic tube. Therefore, it is possible to prevent the contact tip 22 inserted into the narrow groove 50 from coming into contact with the groove surface and causing a short circuit.

[0045] In this embodiment, the torch 20 equipped with the contact tip 22 is mounted on a welding device 1 with a travel distance of 30 cm in the vertical direction Z and the front-rear direction Y. The speed of travel of the contact tip 22 of the torch 20 along the horizontal direction is set to 15 cm / min to 65 cm / min, the torch angle β is 0 degrees to 50 degrees, and the retraction angle β1 is 0 degrees to 10 degrees. Therefore, by setting the operating conditions of torch 20 provided in welding device 1 as described above, the inside of narrow groove 50 having the above-described shape can be efficiently welded.

[0046] In the inclined narrow gap welding method according to the present embodiment configured as described above, downward welding reduces the amount of welding and enables single-pass welding of the inside of the groove by single-layer single-pass construction while preventing the occurrence of hot cracking, thereby enabling sound welding with efficient suppression of welding defects.

[0047] Next, examples performed to verify the effects of the inclined narrow groove welding method according to the above-described embodiment will be described below.

[0048] (First Example) The first example compares the groove cross-sectional areas of Example 1, which is an inclined narrow groove welding method using the narrow groove 50 (see Figure 2) of the above-mentioned embodiment, and Comparative Example 1, which is a welding method using a conventional V-shaped groove.

[0049] Fig. 5(a) shows the groove cross-sectional shape of a V-groove according to a comparative example, and Fig. 5(b) shows the groove cross-sectional shape of a narrow groove according to an embodiment. As shown in Figure 5(a), the comparative example of the narrow groove welding has a groove angle of 35°, a root gap of 7 mm, a reinforcement height of 3 mm, and a root face (RF) of 0. Note that the root face (RF) refers to the length of the vertical plane excluding the slope of the groove. As shown in Figure 5(b), the narrow groove welding of the example has a lower groove angle θ of 35°, an upper groove angle α of 37° (lower groove angle θ + 2°), a root gap RG of 10 mm, and a reinforcement height of 3 mm.

[0050] Figure 6 shows the relationship between the steel plate thickness t (mm) and the groove cross-sectional area (mm) when the lower groove angle θ is 35°. 2 ) in Fig. 6. In Fig. 6, the horizontal axis is the thickness t (mm) of the steel plate, and the vertical axis is the cross-sectional area of ​​the groove (mm 2 ) As shown in Fig. 6, it can be confirmed that the increase rate of the groove cross-sectional area is kept small in the examples compared to the comparative examples even when the plate thickness t is larger. For example, when the plate thickness t is 100 mm, the groove cross-sectional area of ​​the comparative example 1 is approximately 4300 mm 2 The cross-sectional area of ​​the groove in the example is approximately 1500 mm 2The cross-sectional area of ​​the groove in the example is less than half that of the comparative example. Therefore, it is possible to keep the welding amount small and confirm that one layer, one pass welding is possible within the groove.

[0051] (Second Example) In the second example, the welding conditions were changed in Test Examples 1 to 6, and the welding state was visually confirmed and the quality of each was evaluated. Figures 7(a) to (c) are cross-sectional views schematically showing the welded states of Test Examples 1 to 3, respectively. Figures 8(a) to (c) are cross-sectional views schematically showing the welded states of Test Examples 4 to 6, respectively. Figures 9(a) to (c) are photographs of the welded cross sections of Test Examples 1 to 3, respectively. Figures 10(a) to (c) are photographs of the welded cross sections of Test Examples 4 to 6, respectively.

[0052] In Test Examples 1 to 6, which differed in plate thickness, narrow gap, and backing plate shape, test steel plates were welded in one layer using carbon dioxide arc welding under the welding conditions shown in Tables 1 to 6. As shown in Tables 1 to 6, the welding conditions were the current (A), voltage (V), speed (cm / min), welding wire heat input (kJ / cm), wire extension (mm), target position, nozzle type, torch angle (°), and sweepback angle (°) per pass. Regarding the target position, the nozzle indicates the length in the axial direction of the nozzle. For example, "60+cover" indicates the use of a 60 mm tip and cover (representing a slide nozzle), and "Straight 85" indicates the use of a straight 85 mm nozzle for horizontal welding near the surface. Additionally, the "S" values ​​shown in Figures 7(a) to (c) and Figures 8(a) to (c) indicate the measured root gap values ​​on the start side of the test piece, and the "E" values ​​indicate the measured root gap values ​​on the end side of the test piece.

[0053] The welding conditions and test results for Test Examples 1 to 6 are shown below. The welding condition was evaluated based on visual inspection and ultrasonic flaw detection (Architectural Institute of Japan, "Ultrasonic flaw detection inspection standards and commentary for welded parts of steel structures") to check for the presence or absence of welding defects. If no welding defects were found, the condition was rated as "Good", and if even one welding defect was found, the condition was rated as "No Good".

[0054] As shown in Figures 7(a), 9(a) and Table 1, in Test Example 1, the plate thickness was 36 mm, the lower groove angle θ was 35°, and the upper groove angle α was 37° (θ + 2°), and a backing metal was used. In Test Example 1, the welding material was YM-55C with a diameter of 1.4 mm, the shielding gas was CO2 at 60 (inside the groove) and 35 liters / min (surface), and a custom-made contact tip with an outer diameter of 6 mm (length of 60 mm) and a standard tip (commercially available) were used. In Table 1, "α" in the target position indicates the lower plate, and "β" indicates the upper plate. Test Example 1 was evaluated as "good."

[0055] [Table 1]

[0056] As shown in Figures 7(b), 9(b) and Table 2, in Test Example 2, the plate thickness was 36 mm, the lower groove angle θ was 40°, and the upper groove angle α was 42° (θ + 2°), and a backing metal was used. In Test Example 2, the welding material was YM-55C with a diameter of 1.4 mm, the shielding gas was CO2 at 60 (inside the groove) and 35 liters / min (surface), and a custom-made contact tip with an outer diameter of 6 mm (length of 60 mm) and a standard tip (commercially available) were used. In Table 2, "α" in the target position indicates the lower plate, and "β" indicates the upper plate. Test Example 2 was evaluated as "good."

[0057] [Table 2]

[0058] As shown in Figures 7(c), 9(c), and Table 3, in Test Example 3, the plate thickness was 36 mm, the lower groove angle θ was 40°, and the upper groove angle α was 42° (θ + 2°), and a backing metal was used. In Test Example 3, the welding material was YM-55C with a diameter of 1.4 mm, the shielding gas was CO2 at 60 (inside the groove) and 35 liters / min (surface), and a custom-made contact tip with an outer diameter of 6 mm (length of 60 mm) and a standard tip (commercially available) were used. In Table 3, "α" in the target position indicates the lower plate, and "β" indicates the upper plate. Test Example 3 was evaluated as "good."

[0059] [Table 3]

[0060] As shown in Figures 8(a), 10(a) and Table 4, in Test Example 4, the plate thickness was 36 mm, the lower groove angle θ was 45°, the upper groove angle α was 47° (θ + 2°), and a backing metal was used. In Test Example 4, the welding material was YM-55C with a diameter of 1.4 mm, the shielding gas was CO2 at 65 liters / minute, and a custom-made contact tip with an outer diameter of 6 mm (length of 60 mm) and a standard tip (commercially available) were used. The sweep angle was 10°. In Table 4, "α" in the target position indicates the lower plate, and "β" indicates the upper plate. Test Example 4 was evaluated as "good."

[0061] [Table 4]

[0062] As shown in Figures 8(b), 10(b) and Table 5, in Test Example 5, the plate thickness was 36 mm, the lower groove angle θ was 45°, and the upper groove angle α was 47° (θ + 2°), and a backing metal was used. In Test Example 5, the welding material was YM-55C with a diameter of 1.4 mm, the shielding gas was CO2 at 65 liters / min (inside the groove), and a custom-made contact tip with an outer diameter of 6 mm (length of 60 mm) and a standard tip (commercially available) were used. The sweep angle was 10°. In Table 5, "α" in the target position indicates the lower plate, and "β" indicates the upper plate. Test Example 5 was evaluated as "good."

[0063] [Table 5]

[0064] As shown in Figures 8(c), 10(c) and Table 6, in Test Example 6, the plate thickness was 36 mm, the lower groove angle θ was 35°, and the upper groove angle α was 37° (θ + 2°), and a reverse groove was used. In Test Example 5, the welding material was YM-55C with a diameter of 1.4 mm, the shielding gas was CO2 at 65 liters / min (inside the groove), and a custom-made contact tip with an outer diameter of 6 mm (length of 60 mm) and a standard tip (commercially available) were used. The sweep angle was 0° for Pass Nos. 1 to 4 and 0° for Pass Nos. 5 to 10. In Table 6, "α" in the target position indicates the lower plate, and "β" indicates the upper plate. Test Example 6 was evaluated as "good."

[0065] [Table 6]

[0066] The welding results for Test Examples 1 to 6 showed good weld conditions. This shows that in an inclined narrow gap welding method in which welding is performed at an angle using carbon dioxide gas arc welding, it is preferable to set the lower groove angle of the narrow groove on the lower plate side of horizontal welding to 35 to 45 degrees upward from the horizontal, it is preferable to set the upper groove angle to 2 degrees larger than the lower groove angle, and it is preferable to set the root gap of the narrow groove in the range of 9 to 12 mm.

[0067] Furthermore, the results of Test Examples 1 to 6 showed that it is preferable to set the horizontal movement speed of the torch (contact tip) to 17 cm / min to 65 cm / min, the torch angle to 0 degrees to 45 degrees, and the retraction angle to 0 degrees to 10 degrees.

[0068] Furthermore, based on the welding conditions of Test Examples 1 to 6, which produced good welding conditions, it can be said that the wire diameter of the welding wire is preferably 1.4 mm, the current value is preferably set to 240 A to 360 A, the voltage is preferably set to 21 V to 40 V, and the welding travel speed is preferably set to 18 cm / min to 65 cm / min.

[0069] Table 7 shows the results of mechanical tests conducted on Test Examples 4 and 5. Specifically, joint tensile tests, hardness tests, and weld metal tensile tests were conducted. As a result, all test items exceeded the evaluation criteria and were judged to be "pass."

[0070] [Table 7]

[0071] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and their modifications include, for example, those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are equivalent.

[0072] For example, in the above embodiment, the torch 20 is provided so as to be movable in the horizontal direction, but it is not limited to being movable in the horizontal direction.

[0073] In this embodiment, the target position of the first layer P1 of welding in the contact tip 22 is the lower groove, but it is not limited to this position of the lower groove.

[0074] Furthermore, in this embodiment, the contact tip 22 is set to an outer diameter of 6 mm and is insulated by wrapping it with heat-resistant insulating tape or inserting it into a ceramic tube, but other insulating configurations can also be adopted.

[0075] In addition, in this embodiment, a welding device 1 having a welding head equipped with a torch 20 is used, and welding is performed while the welding head is moved along the welding direction, but the welding device is not limited to this type of welding device 1, and it is also possible to omit the welding device. [Explanation of symbols]

[0076] 1. Welding equipment 5 steel plate 5A lower plate 5B Upper Plate 5a Lower end of groove surface 6 Backing metal (burn-through prevention material) 10 welding wire 20 Torch 21 Wire hole 22 Contact Tip 50 Narrow groove X Groove extension direction Y Front-to-rear direction Z vertical direction

Claims

1. An inclined narrow gap welding method in which welding is performed at an angle using carbon dioxide gas arc welding, A process of setting the narrow groove of the horizontal welding at a lower groove angle on the lower plate side at 35 degrees to 45 degrees upward from the horizontal; A step of setting an upper groove angle on the upper plate side to be larger than the lower groove angle by 2 degrees to 5 degrees; setting the root gap of the narrow groove in the range of 9 mm to 12 mm; and a burn-through prevention member attached to the lower plate and the upper plate, which positions a lower end of the groove surface of the upper plate, sets the groove angle and the root gap, and prevents burn-through of molten metal; This is an inclined narrow groove welding method in which a contact tip having a wire hole for feeding out a welding wire is inserted into the narrow groove, and the lower plate and the upper plate are welded inside the groove in one layer, in one pass, without rotating the contact tip around the nozzle axis.

2. 2. The inclined narrow gap welding method according to claim 1, wherein the torch equipped with the contact tip is provided so as to be movable in a horizontal direction.

3. The inclined narrow groove welding method according to claim 1, wherein a target position of a first layer of welding at the contact tip is a lower groove.

4. 2. The inclined narrow gap welding method according to claim 1, wherein the contact tip has an outer diameter of 6 mm and is insulated by being wrapped with heat-resistant insulating tape or being inserted into a ceramic tube.

5. The torch equipped with the contact tip is mounted on a welding device having a vertical and horizontal movement distance of 30 cm, 5. The inclined narrow groove welding method according to claim 1, wherein the moving speed of the contact tip along the horizontal direction of the torch is set to 15 cm / min to 65 cm / min, the torch angle is 0 degrees to 50 degrees, and the retraction angle is 0 degrees to 10 degrees.

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