I-type narrow-gap welding method

Abstract

By performing weaving appropriately under suitable welding conditions, hot cracking of the weld bead can be prevented, or any hot cracks that do occur can be eliminated in the next welding pass. Compared to V-groove and conventional I-groove narrow grooves, carbon dioxide and electricity consumption can be reduced, welding efficiency can be improved, and welding time can be shortened. [Solution] An I-shaped narrow groove welding method is provided in which two steel plates 10A and 10B with thicknesses of 19 to 50 mm are placed parallel to each other to set an I-shaped narrow groove 10a, the root gap is set to a range of 8 to 12 mm, the torch 20 is weaved perpendicular to the welding direction X1 to set the root gap, the torch 20 is set to move at a speed of 18 to 30 cm / min along the welding direction X1 of the I-shaped narrow groove 10a, the welding wire 23 protruding from the contact tip 22 of the torch 20 is inserted into the I-shaped narrow groove 10a, and the torch 20 is weaved at an vibration frequency of 1.5 to 2.0 Hz to weld the inside of the groove in one pass per layer.

Description

Technical Field

[0001] The present invention relates to an I-shaped narrow groove welding method.

Background Art

[0002] Conventionally, in carbon dioxide arc welding, for example, a welding method using an I-shaped narrow groove in which one side is processed to a groove angle of about 0 to 2° to perform welding is known (see, for example, Patent Document 1). In a conventional I-shaped groove, when the bead height of a weld bead is higher than the bead width, hot cracking is likely to occur. Therefore, as a countermeasure against such hot cracking, welding is performed by increasing the number of welding passes to keep the weld bead height low.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, in the conventional welding method using an I-shaped narrow groove, the number of welding passes increases due to countermeasures against hot cracking, which increases the consumption of carbon dioxide gas and electric power, prolongs the welding work time, reduces welding efficiency, and when the plate thickness is large, there is a problem that welding work and quality cannot be ensured with commonly used welding equipment, so there is room for improvement in this respect.

[0005] The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide an I-shaped narrow groove welding method capable of preventing hot cracking of a weld bead or eliminating hot cracking that has occurred in the welding of the next pass by appropriately performing weaving under appropriate welding conditions, suppressing the consumption of carbon dioxide gas and electric power compared to a V-shaped groove and a conventional I-shaped narrow groove, and further reducing the welding work time by improving welding efficiency.

Means for Solving the Problem

[0006] (1) Embodiment 1 of the I-type narrow-gap welding method according to the present invention is an I-type narrow-gap welding method that uses carbon dioxide arc welding to weld steel plates together in a direction perpendicular to the welding direction, and the plate thickness is 28 mm two The process involves setting an I-shaped narrow opening by arranging the first and second steel plates parallel to each other, and setting the root gap of the I-shaped narrow opening to 10 mm. Or 12mm The process includes a setting step and a step of welding by weaving the torch perpendicular to the welding direction using an oscillator head, wherein the root gap is set and a burn-through prevention member is provided on the first and second steel plates to prevent burn-through of molten metal, and the torch moves at a speed along the welding direction of the I-shaped narrow opening. When the aforementioned root gap is 10 mm 18cm / min~ 22 Set to cm / min, With the aforementioned root gap of 12 mm, it is set to 18 cm / min to 23 cm / min. The welding wire protruding from the torch's contact tip is inserted into the I-shaped narrow gap, and the current value is set. Let's set it to 360A. The torch's retraction angle is set to 15°, and the torch's vibration frequency is set to 1.5Hz. weaving This method is characterized by the fact that welding is performed in a single pass within the groove. (2) I-type narrow-gap welding method according to the present invention Embodiment 2 is, This is an I-groove narrow-gap welding method for welding steel plates together perpendicular to the welding direction using carbon dioxide arc welding, comprising the steps of: setting up an I-groove narrow gap by arranging two steel plates, a first and a second, with a thickness of 28 mm, parallel to each other; setting the root gap of the I-groove narrow gap to 8 mm; and performing welding by weaving the torch perpendicular to the welding direction using an oscillator head, wherein a burn-through prevention member is provided on the first and second steel plates to prevent burn-through of molten metal in addition to setting the root gap, the torch is set to move at a speed of 22 cm / min to 24 cm / min along the welding direction of the I-groove narrow gap, the welding wire protruding from the contact tip of the torch is inserted into the I-groove narrow gap, the current value is set to 300 A or 360 A, the torch retraction angle is set to 10°, and the torch is weaved at an oscillation frequency of 2.0 Hz, thereby welding the inside of the groove in one pass per layer. The aforementioned plate thickness is 28 mm in the case of In this case, the current value is set to 360A, and welding is performed by weaving at the vibration frequency of 1.5Hz. It is characterized by the following. (3) Embodiment 3 of the I-type narrow-gap welding method according to the present invention is an I-type narrow-gap welding method that uses carbon dioxide arc welding to weld steel plates together in a direction perpendicular to the welding direction, wherein the plate thickness is 40mm The process of setting an I-shaped narrow opening by arranging two steel plates, the first and second, parallel to each other, and the root gap of the I-shaped narrow opening 10mm or 12mmThe process includes setting the root gap and performing welding by weaving the torch perpendicular to the welding direction using an oscillator head, wherein a burn-through prevention member is provided on the first and second steel plates to set the root gap and prevent burn-through of molten metal, and the torch moves at a speed along the welding direction of the I-shaped narrow opening. When the aforementioned root gap is 10 mm 18cm / min It is set to ~24 cm / min, and 19 cm / min when the aforementioned root gap is 12 mm. The current is set to ~30cm / min, and the welding wire protruding from the torch's contact tip is inserted into the I-shaped narrow gap, and the current value is set to ~30cm / min. When the root gap is 10 mm, the current is 360A, and when the root gap is 12 mm, the current is 300A or 360A. The retraction angle of the torch Let's set it to 15°. The aforementioned torch is characterized by weaving at a vibration frequency of 2.0 Hz, which allows welding to be performed in a single pass within the groove. (4) Embodiment 4 of the I-shaped narrow gap welding method according to the present invention is an I-shaped narrow gap welding method that uses carbon dioxide arc welding to weld steel plates together in a direction perpendicular to the welding direction, comprising the steps of setting an I-shaped narrow gap by arranging two first and second steel plates, each 40 mm thick, parallel to each other, setting the root gap of the I-shaped narrow gap to 8 mm, and performing welding by weaving the torch perpendicular to the welding direction using an oscillator head, and setting the root gap In addition, a burn-through prevention member is provided on the first and second steel plates to prevent burn-through of molten metal. The torch is set to move at a speed of 25 cm / min to 30 cm / min along the welding direction of the I-shaped narrow gap. The welding wire protruding from the contact tip of the torch is inserted into the I-shaped narrow gap, the current is set to 300 A, the retraction angle of the torch is set to 15°, and the torch is weaved at an vibration frequency of 2.0 Hz, thereby welding the inside of the groove in a single pass.

[0007] Embodiments of the I-type narrow-gap welding method according to the present invention According to By weaving the torch at a vibration frequency of 1.5 to 2.0 Hz based on the above-described welding conditions in an I-groove, the groove can be welded in a single pass, preventing the occurrence of hot cracks in the weld bead or eliminating any existing hot cracks in the next pass, thus enabling a suitable weld with suppressed quality degradation. In this way, the ability to use an I-groove reduces the groove cross-sectional area compared to the V-groove commonly used in structural steel welds, thereby reducing the amount of weld material used. This reduces the consumption of welding wire, and consequently, the amount of carbon dioxide and electricity used. As a result, costs can be reduced, welding efficiency can be improved, and welding time can be shortened. Furthermore, the I-groove narrow-gap welding method according to the present invention can reduce carbon dioxide emissions and electricity consumption compared to conventional I-groove narrow-gap welding, thereby reducing costs.

[0008] Thus, in this invention, by performing weaving, the bead surface becomes smooth, and high-temperature cracking can be suppressed by reducing the bead height / bead width ratio after welding is complete. Furthermore, melting both ends of the groove with the arc can suppress fusion defects and penetration defects. Furthermore, since welding is performed in one pass per layer within an I-shaped narrow gap, the number of passes can be reduced compared to multi-pass welding, thereby shortening the welding time and enabling efficient, sound welding with suppressed welding defects, resulting in high-quality welding. For this reason, it is a suitable welding method for factory welding and on-site welding work on columns and beams of steel structures, piers and girders of steel bridges, or piers of steel towers.

[0009] Furthermore, as described above, the present invention makes welding operations more efficient, and the welding process itself becomes easier and simpler, making it easier to control and enabling automation by robots. Furthermore, in this invention, welding can be performed using a general backing plate, eliminating the need for a complex configuration such as being divided into two parts, each fixed to a first steel plate and a second steel plate, thus simplifying the welding process.

[0010] ( 5 ) Aspects of the present invention 5 This is aspect 1 or In the I-shaped narrow-gap welding method of embodiment 3, the I-shaped narrow-gap consists of an initial layer, an intermediate layer, and a surface layer, each having the same thickness, and the measured value of the wire swing width due to weaving is, When the plate thickness is 28 mm or 40 mm and the root gap is 12 mm, From the initial layer to the intermediate layer 9.5mm Set to ru It is preferable.

[0011] In this case, by setting the weaving wire oscillation width within the above range, welding can be more effectively performed inside the groove by one single pass. The occurrence of hot cracking in the weld bead can be prevented, or any hot cracking that has occurred is eliminated during the welding of the next pass, so that suitable welding with suppressed quality degradation can be performed. Specifically, by setting the weaving wire oscillation width within the above range, the oscillation width in the first layer can be the maximum width at which the contact tip does not interfere with the base material, and from the intermediate layer where the tip protrudes out of the groove, the maximum width can be set that allows the welding wire to target both end portions in the weld width direction of the previous pass. Furthermore, from the first layer to the intermediate layer, if the oscillation width is within this range, the ratio of bead height to bead width after welding completion is 1.0 or less, so hot cracking is less likely to occur.

[0012] ( 5 ) Aspect of the present invention 5 In aspect 1 Any one of the four aspects from the four aspects of the I-shaped narrow groove welding method, the extension length of the welding wire protruding from the contact tip is 30 preferably set to mm.

[0013] In this case, by setting the extension length of the welding wire within the above range, welding can be more effectively performed inside the groove by one single pass. The occurrence of hot cracking in the weld bead can be prevented, or any hot cracking that has occurred is eliminated during the welding of the next pass, so that suitable welding with suppressed quality degradation can be performed.

[0016] ( 7 ) Aspect of the present invention 7 In any one of aspects 1 to 6 of the I-shaped narrow groove welding method according to any one of the above aspects, the torch may be moved along the welding direction of the I-shaped narrow groove by a traveling device.

[0017] In this case, by moving the torch in a stable state by the traveling device, welding can be more effectively performed inside the groove by one single pass. The occurrence of hot cracking in the weld bead can be prevented, or any hot cracking that has occurred is eliminated during the welding of the next pass, so that suitable welding with suppressed quality degradation can be performed.

[0020] ( 8 ) Aspects of the present invention 8 This is from Embodiment 1 to Embodiment 7 In any one of the I-type narrow-gap welding methods, the ratio of the bead height to the bead width in the weld bead after welding is completed may be set to be within the range of 1.0 or less.

[0021] In this case, by setting the ratio of the bead height to the bead width of the weld bead after welding to the above range, the groove interior can be welded more effectively in a single pass, preventing the occurrence of hot cracks in the weld bead or eliminating any hot cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0022] (9) Aspect 9 of the present invention is the I-type narrow gap welding method of Aspect 1, in which the thickness of the steel plate is 28 mm and the root gap is 10 mm, the heat input of the welding wire is 39.3~46.8 kJ / cm ru It is preferable.

[0023] In this case, by adopting the above welding conditions for a 28mm thick steel plate, the groove can be welded more effectively in a single pass, preventing the occurrence of high-temperature cracks in the weld bead or eliminating any existing high-temperature cracks in the next pass of welding, thus enabling a suitable weld with suppressed quality degradation.

[0024] (10) Aspect 10 of the present invention is the I-type narrow gap welding method of Aspect 1, in which the thickness of the steel plate is 40 mm and the root gap is 10 mm, the heat input of the welding wire is 35.1~48.0 kJ / cm ru It is preferable.

[0025] In this case, by adopting the above welding conditions for a 40mm thick steel plate, the groove can be welded more effectively in a single pass, preventing the occurrence of high-temperature cracking in the weld bead or eliminating any existing high-temperature cracks in the next pass of welding, thus enabling a suitable weld with suppressed quality degradation. [Effects of the Invention]

[0026] According to the I-groove narrow-gap welding method of the present invention, by performing weaving suitably under suitable welding conditions, high-temperature cracking of the weld bead can be prevented or any resulting high-temperature cracks can be eliminated in the next welding pass. Compared to V-groove and conventional I-groove narrow-gap welding, the consumption of carbon dioxide and electricity can be reduced, and welding time can be reduced by improving welding efficiency. [Brief explanation of the drawing]

[0027] [Figure 1] This is a front view of the I-type narrow-gap welding method according to an embodiment of the present invention, as seen from the welding direction. [Figure 2] Figure 1 shows the main parts of the I-shaped narrow opening. [Figure 3] This is a side view of the I-type narrow-gap welding method, viewed from a direction perpendicular to the welding direction. [Figure 4] Figure 3 is a view along line AA, and is a plan view of the I-shaped narrow opening. [Figure 5] Figures (a) to (d) show the groove cross-sectional shape according to the first embodiment. [Figure 6] This figure shows the relationship between the thickness of the steel plate and the groove cross-sectional area in Comparative Example 1 and Examples 1 to 3 of the First Embodiment. [Figure 7] This is a schematic cross-sectional view showing the welding state in Test Examples 1 to 7 according to the second embodiment. [Figure 8] Figure 7 shows photographs of the welded cross-sections in test examples 1 to 7. [Figure 9] This is a schematic cross-sectional view showing the welding condition in test examples 8 to 10. [Modes for carrying out the invention]

[0028] Hereinafter, embodiments of the I-type 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 in order to make each component visible.

[0029] Figure 1 shows a front view of the I-shaped narrow-gap welding method as seen from the welding direction. Figure 2 shows the main part of the I-shaped narrow-gap in Figure 1. Figure 3 shows a side view of the I-shaped narrow-gap welding method as seen from a direction perpendicular to the welding direction. Figure 4 is a view along the line AA shown in Figure 3, and shows a plan view of the I-shaped narrow-gap. As shown in Figures 1 to 4, the I-shaped narrow-gap welding method of this embodiment is a method of welding steel plates 10A and 10B together in a direction perpendicular to the welding direction X1 (welding width direction X2) using a carbon dioxide arc welding device 2 in the I-shaped narrow-gap 10a of the base material steel plate 10.

[0030] The I-shaped narrow-gap welding method can be suitably used for steel plates 10, for example, for columns and beams used in building steel structures, and has high applicability to welding factory and on-site welds at such construction sites. In steel bridges, it has high applicability to the corner and plate joint welds of columns, and the corner welds of columns (factory). The steel plate 10 has a first steel plate 10A and a second steel plate 10B. As shown in Figure 2, the I-shaped narrow-gap 10a consists of an initial layer 11, an intermediate layer 12, and a surface layer 13, each having the same thickness. The I-shaped narrow-gap 10a is set by arranging two steel plates, the first steel plate 10A and the second steel plate 10B, with a plate thickness t of 19 mm to 50 mm, parallel to each other and facing each other in the welding width direction X2. In the I-shaped narrow-gap welding method according to this embodiment, a welded joint can be formed by welding the I-shaped narrow gap 10a between the first steel plate 10A and the second steel plate 10B, thereby joining the second steel plate 10B to the first steel plate 10A.

[0031] The I-shaped narrow-gap welding method according to this embodiment includes the steps of setting an I-shaped narrow gap by arranging the first steel plate 10A and the second steel plate 10B parallel to each other, setting the root gap RG of the I-shaped narrow gap 10a to a range of 8 mm to 12 mm, and performing welding by weaving the torch 20 perpendicular to the welding direction X1 (welding width direction X2) using an oscillator head (not shown).

[0032] In the I-type narrow-gap welding method, a backing plate 3 (burn-through prevention member) is installed across the first steel plate 10A and the second steel plate 10B to set the root gap RG and prevent burn-through of molten metal. The backing plate 3 is made of a steel plate and is installed to close the opening on one end side of the I-type narrow-gap 10a in the welding direction X1.

[0033] Furthermore, in the I-shaped narrow-gap welding method, a contact tip 22 having a wire hole 22a for feeding the welding wire 23 is inserted into the I-shaped narrow-gap 10a, and welding is performed inside the I-shaped narrow-gap 10a of the first steel plate 10A and the second steel plate 10B in one pass per layer without rotating the contact tip 22 around the nozzle axis O1.

[0034] The contact tip 22 is, for example, a custom-made one and is mounted on the nozzle 21 of the torch 20. The contact tip 22 is a cylindrical conductor that guides the welding wire 23 to the welding bead wa and supplies the welding current, and is a replaceable metal part fixed to the tip of the torch 20.

[0035] The torch 20 is mounted on a welding apparatus 2 that is movable in the welding direction X1 (corresponding to the extension direction of the I-shaped narrow groove 10a), the welding width direction X2, and the groove extension direction X3 (corresponding to the thickness direction of the steel plate 10). Here, the groove extension direction X3 is perpendicular to the welding direction X1 and the welding width direction X2. The torch 20 is set to move at a speed of 18 cm / min to 30 cm / min in the welding direction X1, and its retraction angle β is set to 15° ± 5° (10° to 20°). In this embodiment, the torch angle θ of the torch 20 relative to the plate surface 10b of the steel plate 10, as viewed from the groove extension direction X3, is 90° and coincides with the welding direction X1.

[0036] As shown in Figures 1 and 3, the welding apparatus 2 (traveling apparatus) is a device that allows the torch 20 to move in three directions: the welding direction X1, the welding width direction X2, and the groove extension direction X3. That is, the welding apparatus 2 is equipped with a drive unit 24 that vibrates the torch 20 in direction X2. The welding apparatus 2 also has a control unit (not shown) that controls the torch 20 based on input information pre-programmed for each direction X1, X2, and X3. The movement of the torch 20 in the welding width direction X2 (wire swing direction E1 shown in Figure 2) is a weaving operation with a predetermined swing width (range of the dashed line 20K shown in Figure 1).

[0037] The welding apparatus 2 includes a guide rail (not shown) extending along the groove extension direction X3, and a welding head 25 that can travel on the guide rail. The welding head 25 is integrally provided with a torch 20 equipped with a contact tip 22. As shown in Figure 3, the welding head 25 is equipped with a mechanism that rotates the torch 20 at a retraction angle β when viewed from the welding width direction X2. That is, the torch 20 and contact tip 22 are slidable in the groove extension direction X3 as described above, and are also movable in the welding direction X1 and the welding width direction X2, and the retraction angle β can also be changed.

[0038] The contact tip 22 has an outer diameter of 6 mm. The contact tip 22 is insulated by wrapping it with heat-resistant insulating tape (not shown) or by inserting it into a ceramic tube.

[0039] The protrusion length L (see Figure 2) of the welding wire 23 extending from the contact tip 22 is set to a range of 25 mm to 35 mm.

[0040] In the I-type narrow-gap welding method, welding wire 23 with a wire diameter of 1.2 mm to 1.4 mm is used. In the I-type narrow-gap welding method, the current is set to 300 A to 380 A, the voltage to 30 V to 40 V, the heat input of the welding wire 23 to 23 to 50 kJ / cm, and the welding travel speed to 18 cm / min to 30 cm / min.

[0041] Furthermore, the weaving conditions for the torch 20 are set to an vibration frequency of 1.5 to 2.0 Hz (1.5 to 2.0 reciprocations per second). The amplitude of the weaving of the torch 20 within the I-shaped narrow gap 10a is set to 2.5 to 9.5 mm from the first layer 11 to the intermediate layer 12, and to 5.5 to 15.5 mm in the surface layer 13. The stopping time of the torch 20 due to weaving is set to 0.1 to 0.2 seconds at both the left and right positions in the welding width direction X2. In addition, the ratio of the weld bead height H to the bead width W after welding is completed by weaving is set to be within a range of approximately 1.0 or less. Under these weaving conditions, the welding wire 23 protruding from the contact tip 22 of the torch 20 is inserted into the I-shaped narrow gap 10a, and the torch 20 is weaved at a vibration frequency of 1.5 to 2.0 Hz, thereby welding the inside of the I-shaped narrow gap 10a in a single pass.

[0042] In the I-groove narrow-gap welding method, based on the above welding conditions, current is supplied to the welding wire 23 from a power source (not shown) to generate an arc between the first steel plate 10A, the second steel plate 10B, and the welding wire 23. Then, the torch 20 is moved in the welding direction X1 (the direction perpendicular to the plane of the paper in Figures 1 and 2, and the direction toward the right side of the paper in Figures 3 and 4) at the predetermined movement speed described above. This forms a molten pool behind the arc. By using these welding conditions, it is possible to more reliably prevent insufficient penetration, insufficient fusion, and high-temperature cracking that occur in single-pass welding of a single-layer narrow-gap 10a.

[0043] Next, the operation of the I-type narrow-gap welding method, as configured in this manner, will be explained in detail based on the drawings. The I-shaped narrow-gap welding method according to this embodiment uses carbon dioxide arc welding to weld steel plates 10A and 10B perpendicular to the welding direction. The I-shaped narrow-gap welding method includes the steps of setting an I-shaped narrow gap 10a by arranging two steel plates, a first steel plate 10A and a second steel plate 10B, with thicknesses of 19 mm to 50 mm, parallel to each other; setting the root gap of the I-shaped narrow gap 10a in the range of 8 mm to 12 mm; and performing welding by weaving the torch 20 perpendicular to the welding direction X1 using an oscillator head. In addition to setting the root gap, a backing plate 3 is provided on the first steel plate 10A and the second steel plate 10B to prevent burn-through of molten metal. The torch 20 is set to move at a speed of 18 cm / min to 30 cm / min along the welding direction X1 of the I-shaped narrow gap 10a. A welding wire 23 protruding from the contact tip 22 of the torch 20 is inserted into the I-shaped narrow groove 10a. The torch 20 is weaved at an vibration frequency of 1.5 to 2.0 Hz to weave the inside of the groove in a single pass.

[0044] According to the I-groove narrow-gap welding method of this embodiment, by weaving the torch 20 at an vibration frequency of 1.5 to 2.0 Hz based on the above-described welding conditions in the I-groove narrow-gap 10a, welding can be performed in a single pass for one layer inside the groove. This prevents the occurrence of high-temperature cracking in the weld bead wa, or eliminates any high-temperature cracking that occurs in the next pass of welding, resulting in a suitable weld with suppressed quality degradation. Thus, by enabling the I-groove narrow-gap 10a, the groove cross-sectional area can be reduced compared to the V-groove commonly applied to welds in structural steel frames, thereby reducing the amount of welding required. This reduces the consumption of welding wire 23, and consequently, the amount of carbon dioxide and electricity consumed can be reduced. Therefore, costs can be reduced, welding efficiency can be improved, and welding time can be reduced. Furthermore, the I-groove narrow-gap welding method of this embodiment can reduce carbon dioxide emissions and electricity consumption compared to conventional I-groove narrow-gap welding, thereby reducing costs.

[0045] In this embodiment, weaving makes the bead surface smooth, and high-temperature cracking can be suppressed by reducing the bead height / bead width ratio after welding is complete. Furthermore, melting both ends of the groove with the arc can suppress fusion defects and insufficient penetration. Furthermore, in this embodiment, welding is performed in one pass per layer within the I-shaped narrow groove 10a. Compared to multi-pass welding, the number of passes can be reduced, thereby shortening the welding time and enabling efficient, sound welding with suppressed welding defects, resulting in high-quality welding. Therefore, this welding method is suitable for factory welding and on-site welding work on columns and beams of steel structures, piers and girders of steel bridges, or piers of steel towers.

[0046] Furthermore, in this embodiment, as described above, the efficiency of the welding work can be improved, and the welding work itself becomes easy and simple, making it easier to control and enabling automation by robots. Furthermore, in this embodiment, welding can be performed using a general backing plate 3, eliminating the need for a complex configuration such as being divided into two parts and each being fixed to the first steel plate 10A and the second steel plate 10B, thereby simplifying the welding process.

[0047] In this embodiment, the I-shaped narrow groove 10a consists of a primary layer 11, an intermediate layer 12, and a surface layer 13, each having the same thickness. The weaving amplitude (measured value) is set to 2.5 to 9.5 mm from the primary layer 11 to the intermediate layer 12, and to 5.5 to 15.5 mm in the surface layer 13. With this configuration, by setting the weaving width within the above range, welding can be performed more effectively in a single pass within a single layer, preventing the occurrence of hot cracks in the weld bead wa, or eliminating any hot cracks that do occur in the next pass of welding, resulting in a suitable weld with suppressed quality degradation. Specifically, by setting the weaving width within the above range, the weaving width of the initial layer 11 can be set to the maximum width where the tip and base material do not interfere, and the weld wire 23 from the intermediate layer 12 where the tip emerges from the groove can be set to the maximum width where it can target both ends in the welding width direction of the previous pass. Furthermore, within this range of weaving width from the initial layer 11 to the intermediate layer 12, the ratio of bead height / bead width after welding is 1.0 or less, making it less likely for hot cracks to occur.

[0048] In this embodiment, the protrusion length L of the welding wire 23 extending from the contact tip 22 is set to a range of 25 mm to 35 mm. With this configuration, by setting the protrusion length L of the welding wire 23 within the above range, welding inside the groove can be performed more effectively in a single pass, preventing the occurrence of hot cracks in the weld bead wa or eliminating any hot cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0049] Furthermore, in this embodiment, the heat input to the weld bead wa is 23 to 50 kJ / cm. With this configuration, by setting the heat input to the weld bead wa within the above range, welding can be performed more effectively in a single pass within a single layer inside the groove, preventing the occurrence of high-temperature cracks in the weld bead wa or eliminating any high-temperature cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0050] In this embodiment, the torch 20 is moved along the welding direction of the I-shaped narrow gap 10a by a traveling device. With this configuration, the torch 20 is moved in a stable state by the travel device, allowing for more effective welding of the groove interior in a single pass, preventing the occurrence of high-temperature cracks in the weld bead wa, or eliminating any high-temperature cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0051] Furthermore, in this embodiment, the retraction angle β of the torch 20 is 15°±5°. With this configuration, by setting the retraction angle β of the torch 20 within the above range, welding can be performed more effectively in a single pass within a single layer inside the groove, preventing the occurrence of hot cracks in the weld bead wa or eliminating any hot cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0052] Furthermore, in this embodiment, the ratio of the bead height H to the bead width W in the weld bead wa after welding is set to be within a range of 1.0 or less. With this configuration, by setting the ratio of bead height H to bead width W in the weld bead wa after welding to the above range, the groove interior can be welded more effectively in a single pass, preventing the occurrence of hot cracks in the weld bead wa, or eliminating any hot cracks that do occur in the next pass of welding, thereby enabling suitable welding with suppressed quality degradation.

[0053] Furthermore, in this embodiment, when the steel plate 10 has a thickness of 28 mm and a root gap of 10 mm, the heat input to the weld bead wa is 39 to 47 kJ / cm, and the movement speed of the torch 20 is 18 to 22 cm / min. With this configuration, by adopting the above welding conditions, the inside of the groove can be welded more effectively in a single pass in a 28 mm thick steel plate 10, preventing the occurrence of high-temperature cracks in the weld bead wa, or eliminating any high-temperature cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0054] Furthermore, in this embodiment, when the steel plate 10 has a thickness of 40 mm and a root gap of 10 mm, the heat input to the welding wire 23 is 35 to 48 kJ / cm, and the movement speed of the torch 20 is 18 to 24 cm / min. With this configuration, by adopting the above welding conditions, the inside of the groove can be welded more effectively in a single pass in a 40 mm thick steel plate 10, preventing the occurrence of high-temperature cracks in the weld bead wa, or eliminating any high-temperature cracks that do occur in the next pass of welding, thereby enabling a suitable weld with suppressed quality degradation.

[0055] In the I-groove narrow-gap welding method according to this embodiment, configured as described above, high-temperature cracking of the weld bead wa can be prevented by performing weaving appropriately under suitable welding conditions. Compared to V-groove and conventional I-groove narrow-gap welding, the consumption of carbon dioxide and electricity can be reduced, and welding time can be reduced by improving welding efficiency.

[0056] Next, an example of a method used to support the effectiveness of the I-type narrow-gap welding method according to the above-described embodiment will be explained below.

[0057] (First embodiment) The first embodiment compares the groove cross-sectional areas of Examples 1, 2, and 3 of the I-shaped narrow groove welding method using the I-shaped narrow groove 10a (see Figure 2) of the above-described embodiment with those of Comparative Example 1 of the conventional V-shaped groove welding method.

[0058] Figure 5 shows the groove cross-sectional shape according to the first embodiment, where (a) is the groove cross-sectional shape of a V-shaped groove according to Comparative Example 1, (b) is the groove cross-sectional shape of a narrow I-shaped groove according to Example 1, (c) is the groove cross-sectional shape of a narrow I-shaped groove according to Example 2, and (d) is the groove cross-sectional shape of a narrow I-shaped groove according to Example 3. As shown in Figure 5(a), the V-groove weld of Comparative Example 1 has a plate thickness of 25 mm, a root gap (RG) of 7 mm, a groove angle of 35°, and a groove cross-sectional area of ​​394 mm². 2 As shown in Figure 5(b), the I-type narrow groove weld of Example 1 has a root gap (RG) of 8 mm and a groove cross-sectional area of ​​200 mm².2 The area ratio of the V-shaped weld in Comparative Example 1 to the I-shaped weld in Example 1 is 0.5. As shown in Figure 5(c), the I-shaped narrow groove weld in Example 2 has a root gap (RG) of 10 mm and a groove cross-sectional area of ​​250 mm². 2 The area ratio of the V-shaped weld in Comparative Example 1 to the I-shaped weld in Example 2 is 0.63. As shown in Figure 5(d), the I-shaped narrow groove weld in Example 3 has a root gap (RG) of 12 mm and a groove cross-sectional area of ​​300 mm². 2 The area ratio between the L-shaped section of Comparative Example 1 and the I-shaped section of Example 3 is 0.76.

[0059] Figure 6 shows the steel plate thickness t (mm) and groove cross-sectional area (mm) in Comparative Example 1 and Examples 1-3. 2 This shows the relationship between the two. In Figure 6, the horizontal axis is the thickness t (mm) of the steel plate, and the vertical axis is the groove cross-sectional area (mm). 2 ) As shown in Figure 6, it can be confirmed that in all of Examples 1 to 3, the rate of increase in the groove cross-sectional area when the plate thickness t is increased compared to Comparative Example 1 can be kept small. For example, when the plate thickness t is 25 mm, the groove cross-sectional area of ​​Comparative Example 1 is approximately 400 mm². 2 Therefore, the groove cross-sectional area of ​​Example 1 is approximately 200 mm². 2 Thus, Example 1 has a groove cross-sectional area that is less than half that of Comparative Example 1. In this way, Examples 1 to 3 of the I-groove narrow groove can be made to reduce the amount of welding required, and it can be confirmed that single-pass welding of a single layer is possible within the I-groove narrow groove.

[0060] (Second example) In the second embodiment, the welding condition was visually inspected and the quality of each test example (1-10) was evaluated by varying the welding conditions. Figure 7 is a schematic cross-sectional view showing the welding state in each of the test examples 1 to 7. Figure 8 is a photograph of the weld cross-section in each of the test examples 1 to 7 shown in Figure 7. Figure 9 is a photograph of the weld cross-section in test examples 8 to 10.

[0061] Test examples 1-4 use a plate thickness of 28 mm. Test example 1 is a test in which four layers were welded with one pass per layer at a root gap (RG) of 8 mm. Test example 2 is a test in which three layers were welded with one pass per layer at an RG of 10 mm. Test example 3 is a test in which four layers were welded with one pass per layer at an RG of 10 mm. Test example 4 is a test in which four layers were welded with one pass per layer at an RG of 12 mm. Test examples 5-7 use a plate thickness of 40 mm. Test example 5 is a test in which six layers were welded with one pass per layer at an RG of 8 mm. Test example 6 is a test in which five layers were welded with one pass per layer at an RG of 10 mm. Test example 7 is a test in which six layers were welded with one pass per layer at an RG of 12 mm.

[0062] Test examples 8 and 9 use a plate thickness of 28 mm. Test example 8 is a test in which four layers were welded with a root gap (RG) of 8 mm and one pass per layer. Test example 9 is a test in which four layers were welded with an RG of 12 mm and one pass per layer. Test example 10 is a test in which five layers were welded with a plate thickness of 40 mm and an RG of 10 mm and one pass per layer.

[0063] Table 1 shows the welding conditions and test results for Test Examples 1-4 with a plate thickness of 28 mm. Table 2 shows the welding conditions and test results for Test Examples 5-7 with a plate thickness of 40 mm. Table 3 shows the welding conditions and test results for Test Examples 8 and 9 with a plate thickness of 28 mm, and for Test Example 10 with a plate thickness of 40 mm.

[0064] In Test Examples 1 to 10, test steel plates were welded in a single pass using carbon dioxide arc welding under the specified welding conditions. The welding conditions, as shown in Tables 1 to 3, included the current (A), voltage (V), speed (cm / min), heat input (kJ / cm), welding wire protrusion length (mm), receding angle (°) for each pass, and weaving conditions such as frequency (Hz), swing amplitude (mm) (set value, measured value), L (left side) stop time (seconds), R (right side) stop time (seconds), weld bead height H (mm) after welding completion, weld bead width W (mm) after welding completion, and the ratio H / W after welding completion. Speed ​​is the speed of movement in the welding direction.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] The test results for Test Examples 1 to 10 are shown below. As shown in Figures 8 and 9, the welding condition was evaluated based on visual inspection and ultrasonic testing (Architectural Institute of Japan "Standards and Commentary for Ultrasonic Testing of Welded Parts in Steel Structures") to check for welding defects. If no welding defects were found, the result was evaluated as "Good," and if even one welding defect was found, it was evaluated as "No Good."

[0069] As shown in Figure 8, Table 1, and Table 2, the results of Test Examples 1 to 7 all received a "good" rating, indicating good welding conditions. Therefore, in the I-groove narrow-gap welding method using carbon dioxide arc welding to weld an I-groove narrow gap while satisfying the welding conditions shown in Tables 1 and 2, the following welding conditions can be set. Based on the results of Test Examples 1-7, it can be said that it is preferable to set the root gap (RG) of the I-shaped narrow opening in the range of 8 mm to 12 mm.

[0070] Furthermore, based on the results of Test Examples 1 to 7, it is preferable to set the movement speed of the torch (contact tip) along the welding direction to 18 cm / min to 30 cm / min, and to weave the torch at an vibration frequency of 1.5 to 2.0 Hz. It is also preferable to set the retraction angle of the torch to 15° ± 5°.

[0071] Furthermore, based on the welding conditions of Test Examples 1 to 7, which showed good welding conditions, it is preferable to set the current value to 300A to 360A and the voltage to 30V to 40V, and it is also preferable to set the heat input to the weld bead wa to 23 to 50kJ / cm.

[0072] Furthermore, based on the results of Test Examples 1 to 7, it can be said that, in terms of the weaving amplitude (measured value) of the torch within an I-shaped narrow gap, it is preferable to set the initial layer to the intermediate layer to 2.5 to 9.5 mm, and the surface layer to 5.5 to 15.5 mm.

[0073] Furthermore, based on the results of Test Examples 1 to 7, it can be said that it is preferable to set the torch stopping time due to weaving to 0.1 to 0.2 seconds at both the left and right positions in the welding width direction. In addition, it can be said that it is preferable to set the ratio of the bead height H to the bead width W after the completion of welding by weaving to be in a range of approximately 1.0 or less.

[0074] As shown in Figure 9 and Table 3, the results of Test Examples 8-10 all resulted in a "poor" evaluation, indicating poor welding conditions. Specifically, in Test Example 8, hot cracks occurred at the locations indicated by the arrows in the figure. This is thought to be because the high current of 360A caused the ratio of bead height to bead width of the weld pass after welding to exceed 1.0, resulting in hot cracks (longitudinal cracks) at the top of the pass due to shrinkage. Therefore, it is preferable to set the welding current to 300A, as in Test Example 1. Another possible cause is that the penetration of the next pass was shallow, failing to eliminate the cracks that occurred at the top of the bead. Therefore, increasing the weaving frequency, for example from 1.5Hz to 2.0Hz, smoothing the bead surface, and lowering the voltage increases the penetration depth, which is suitable for removing cracks that occurred in the previous pass.

[0075] In Test Example 9, poor penetration occurred at the locations indicated by the arrows in the figure. This is thought to be due to a small torch swing amplitude, resulting in shallow penetration at the corners. Therefore, it is preferable to set the measured swing amplitude so that the wire target position for the first layer of welding is at the narrow gap corners, between 8.5 mm and 9.5 mm. In addition, in Test Example 9, it is also thought that the molten metal preceded the arc, resulting in shallow penetration. Therefore, it is preferable to set the welding speed so that the molten metal does not precede the arc.

[0076] In Test Example 10, fusion failure occurred at the locations indicated by the arrows in the figure. This is thought to be because, with a retreat angle of 0°, the molten metal preceded the arc, resulting in shallow penetration and fusion failure between passes. Therefore, it is preferable to set the retreat angle from 0° to, for example, 10° to 15°, as in Test Example 6. Furthermore, it was found that it is beneficial to set the welding speed so that the molten metal does not precede the arc.

[0077] Although 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. 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. Embodiments and their modifications include, for example, those that can be easily imagined by those skilled in the art, those that are substantially the same, and those that are equivalent.

[0078] For example, the welding direction can be applied horizontally or vertically (up and down).

[0079] Furthermore, in this embodiment, a welding apparatus 2 having a welding head 25 equipped with a torch 20 is used, and welding is performed while moving the welding head 25 along the welding direction X1. However, the invention is not limited to such a welding apparatus 2, and it is also possible to omit the welding apparatus 2. [Explanation of Symbols]

[0080] 2. Welding equipment 3. Backing plate (anti-melt-off component) 10 steel plate 10A 1st steel plate 10B 2nd steel plate 10a I type narrow gap 11 Elementary section 12 Middle layer 13 Surface layer 20 Torches 22a Wire hole 22 Contact Tips 23 Welding wire wa welding bead X1 Welding direction X2 Weld width direction X3 Groove extension direction β Retraction angle θ Torch angle U Swing amplitude (measured value)

Claims

1. An I-shaped narrow-gap welding method in which steel plates are welded together perpendicular to the welding direction using carbon dioxide arc welding, The process of setting an I-shaped narrow opening by arranging two steel plates, a first steel plate and a second steel plate, each with a thickness of 28 mm, parallel to each other, The steps include setting the root gap at the I-shaped narrow opening to 10 mm or 12 mm, The process includes using an oscillator head and performing welding by weaving the torch perpendicular to the welding direction, The aforementioned root gap is set, and a melt-through prevention member for preventing molten metal from melting through is provided on the first steel plate and the second steel plate. The torch is set to move along the welding direction of the I-shaped narrow opening at a speed of 18 cm / min to 22 cm / min when the root gap is 10 mm, and at a speed of 18 cm / min to 23 cm / min when the root gap is 12 mm. An I-shaped narrow-gap welding method is performed by inserting a welding wire protruding from the contact tip of the torch into the I-shaped narrow groove, setting the current to 360A, setting the torch's retraction angle to 15°, and weaving the torch at a vibration frequency of 1.5Hz to weave the inside of the groove in a single pass.

2. An I-shaped narrow-gap welding method for welding steel plates together perpendicular to the welding direction using carbon dioxide arc welding, The process of setting an I-shaped narrow opening by arranging two steel plates, a first steel plate and a second steel plate, each with a thickness of 28 mm, parallel to each other, The process of setting the root gap at the I-shaped narrow opening to 8 mm, The process includes using an oscillator head and performing welding by weaving the torch perpendicular to the welding direction, The aforementioned root gap is set, and a melt-through prevention member for preventing molten metal from melting through is provided on the first steel plate and the second steel plate. The torch is set to move at a speed of 22 cm / min to 24 cm / min along the welding direction of the I-shaped narrow opening. An I-shaped narrow-gap welding method is performed by inserting a welding wire protruding from the contact tip of the torch into the I-shaped narrow groove, setting the current to 300A or 360A, setting the torch's retraction angle to 10°, and weaving the torch at a vibration frequency of 2.0Hz to weave the inside of the groove in a single pass.

3. An I-shaped narrow-gap welding method in which steel plates are welded together perpendicular to the welding direction using carbon dioxide arc welding, The process of setting an I-shaped narrow opening involves arranging two steel plates, a first steel plate and a second steel plate, each 40 mm thick, parallel to each other. The steps include setting the root gap at the I-shaped narrow opening to 10 mm or 12 mm, The process includes using an oscillator head and performing welding by weaving the torch perpendicular to the welding direction, The aforementioned root gap is set, and a melt-through prevention member for preventing molten metal from melting through is provided on the first steel plate and the second steel plate. The torch is set to move at a speed along the welding direction of the I-shaped narrow opening at 18 cm / min to 24 cm / min when the root gap is 10 mm, and at 19 cm / min to 30 cm / min when the root gap is 12 mm. An I-shaped narrow-gap welding method is performed by inserting a welding wire protruding from the contact tip of the torch into the I-shaped narrow groove, setting the current to 360A when the root gap is 10 mm, and 300A or 360A when the root gap is 12 mm, setting the torch's retraction angle to 15°, and weaving the torch at a vibration frequency of 2.0 Hz to weave the inside of the groove in a single pass.

4. An I-shaped narrow-gap welding method for welding steel plates together perpendicular to the welding direction using carbon dioxide arc welding, The process of setting an I-shaped narrow opening involves arranging two steel plates, a first steel plate and a second steel plate, each 40 mm thick, parallel to each other. The process of setting the root gap at the I-shaped narrow opening to 8 mm, The process includes using an oscillator head and performing welding by weaving the torch perpendicular to the welding direction, The aforementioned root gap is set, and a melt-through prevention member for preventing molten metal from melting through is provided on the first steel plate and the second steel plate. The torch is set to move at a speed of 25 cm / min to 30 cm / min along the welding direction of the I-shaped narrow opening. An I-shaped narrow-gap welding method is performed by inserting a welding wire protruding from the contact tip of the torch into the I-shaped narrow groove, setting the current to 300A, setting the torch's retraction angle to 15°, and weaving the torch at a vibration frequency of 2.0Hz to weave the inside of the groove in a single pass.

5. The aforementioned I-shaped narrow opening consists of a primary layer, an intermediate layer, and a surface layer, each having the same thickness. The I-shaped narrow-gap welding method according to claim 1 or 3, wherein the measured value of the wire swing width due to the weaving is set to 9.5 mm from the first layer to the intermediate layer when the plate thickness is 28 mm or 40 mm and the root gap is 12 mm.

6. The I-shaped narrow-gap welding method according to any one of claims 1 to 4, wherein the protrusion length of the welding wire protruding from the contact tip is set to 30 mm.

7. The I-shaped narrow-gap welding method according to any one of claims 1 to 4, wherein the torch is moved along the welding direction of the I-shaped narrow-gap by a traveling device.

8. I-groove narrow-gap welding method according to any one of claims 1 to 4, wherein the ratio of the bead height to the bead width in the weld bead after welding is set to be within the range of 1.0 or less.

9. The I-shaped narrow-gap welding method according to claim 1, wherein the thickness of the steel plate is 28 mm and the root gap is 10 mm, and the heat input of the welding wire is 39.3 to 46.8 kJ / cm.

10. The I-shaped narrow-gap welding method according to claim 3, wherein the thickness of the steel plate is 40 mm and the root gap is 10 mm, and the heat input of the welding wire is 35.1 to 48.0 kJ / cm.

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