Narrow-gap arc welding method

Abstract

To provide a narrow-gap arc welding method that can reduce the amount of welding while ensuring good workability and minimizing the possibility of welding defects. [Solution] A narrow-gap arc welding method is provided in which a V-groove 22 is provided at one end of a first base material 10 and a second base material 20, and the V-groove 22 and the other end 12 or surface 11 are narrow-gap arc welded. The groove angle θ1 of the V-groove 22 is in the range of 30 to 35 degrees, the root gap G is in the range of 4 mm to 6 mm, the arc output current is set in the range of 380 A to 410 A, and the arc output voltage is set in the range of 42 V to 45 V for arc welding.

Description

Technical Field

[0001] The present invention relates to a narrow groove arc welding method.

Background Art

[0002] In arc welding, based on the description of "Welding Groove Standard" in "Steel Structure Work" of the Architectural Institute of Japan's Architectural Construction Standard Specification JASS6, a groove angle of 35 degrees and a root gap (root interval) of 7 mm are generally applied. However, in arc welding under the setting of this groove angle and root gap, the welding amount often increases, so reducing the welding amount has become one of the problems in arc welding.

[0003] Therefore, as one of the measures to reduce the welding amount, a so-called narrow groove arc welding method of increasing the groove angle or narrowing the root gap compared to the specifications described in JASS6 above can be considered. However, in the measure of increasing the groove angle, it becomes difficult to insert the welding torch into the groove, and it becomes difficult for the operator to visually recognize the welding location, so it is not preferable. On the other hand, according to the measure of narrowing the root gap, although the welding amount can be reduced while ensuring good workability, the problems when the root gap is narrowed include the possibility of welding defects such as hot cracks occurring during the solidification process of the weld metal. From the perspective of efficient arc welding, this problem becomes more prominent by increasing the current.

[0004] From the above, a narrow groove arc welding method that can reduce the welding amount while ensuring good workability and reducing the possibility of welding defects is desired.

[0005] Here, Patent Document 1 proposes a narrow-gap butt welding method for thick steel plates. This narrow-gap butt welding method uses thick steel plates with a thickness of 12 mm or more, has a root gap of 2 mm or less and a groove angle of 30 degrees or less, and performs gas shielded arc welding of the first layer at the bottom of the narrow groove at a welding speed of 15 to 25 mm / sec, satisfying the range of 1.5 to 10.01 for the QL value calculated as QL = I × E / [S × (G + 5 × tanθ)] / 60, and satisfying the range of 1.0 or more for the QH value calculated as QH = [G × S × 60 × (G + tanθ) / (I × E)] + tanθ. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-51030 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the narrow-gap butt welding method for thick steel plates described in Patent Document 1, the arc stability is excellent even in the first layer of multi-layer welding, and stable penetration can be obtained. However, because the root gap is too narrow at 2 mm or less, the above-mentioned problem, namely the possibility of high-temperature cracking, may occur.

[0008] This invention has been made in view of the above problems, and aims to provide a narrow-gap arc welding method that can reduce the amount of welding while ensuring good workability and minimizing the possibility of welding defects. [Means for solving the problem]

[0009] To achieve the above objective, one embodiment of the narrow-gap arc welding method according to the present invention is: A narrow-gap arc welding method comprising: providing a V-groove at one end of a first base material and a second base material; and performing narrow-gap arc welding between the V-groove on one end of the first base material and the other end or surface of the second base material, The groove angle of the aforementioned V-shaped groove is in the range of 30 to 35 degrees. The root gap is in the range of 4mm to 6mm. Set the arc output current to a range of 380A to 410A. This method is characterized by performing arc welding with the arc output voltage set to a range of 42V to 45V.

[0010] According to this embodiment, a V-groove is provided at one end of a first base material and a second base material, and in a method of narrow-groove arc welding this V-groove to the other end or surface, the groove angle is maintained in the range of 30 to 35 degrees in accordance with the JASS6 specifications to ensure good workability, the root gap is set to a range of 4 mm to 6 mm which is narrower than the JASS6 specifications, the arc output current is set in the range of 380 A to 410 A, and the arc output voltage is set in the range of 42 V to 45 V, thereby reducing the amount of welding while making the root gap narrower than the general specifications and reducing the amount of welding.

[0011] To reduce the possibility of welding defects, setting the arc output current to a range of 380A to 410A, slightly higher than the normal setting of 300A to 350A, allows for efficient arc welding while lowering the possibility of hot cracking.

[0012] Furthermore, by setting the arc output voltage to a range of 42V to 45V, the possibility of undercutting, which can be a problem when the voltage is too high, can be reduced.

[0013] Furthermore, another embodiment of the narrow-gap arc welding method according to the present invention is: A narrow-groove arc welding method comprising providing grooves at both ends of a first base material and a second base material, forming a V-shaped groove by the ends of the first and second base materials, and performing narrow-groove arc welding in the V-shaped groove, The groove angle of the V-shaped groove is in the range of 30 to 35 degrees. The root gap is in the range of 4mm to 6mm. Set the arc output current to a range of 380A to 410A. This method is characterized by performing arc welding with the arc output voltage set to a range of 42V to 45V.

[0014] According to this embodiment, grooves are provided on both the first and second base materials, and even in a method of narrow-groove arc welding to a V-shaped groove formed by both grooves, by performing arc welding under the same groove angle range, root gap range, arc output current range, and output voltage range as in the case of the L-shaped groove described above, good workability can be ensured, the possibility of welding defects can be reduced, and the amount of welding can be reduced by making the root gap narrower than the general specifications.

[0015] Furthermore, another embodiment of the narrow-gap arc welding method according to the present invention is: Arc welding is performed with a backing plate placed at the bottom of the aforementioned L-shaped groove or V-shaped groove.

[0016] According to this embodiment, by installing a backing plate at the bottom of an L-shaped groove or V-shaped groove and performing arc welding, the occurrence of burn-through and welding defects can be prevented.

[0017] Furthermore, another embodiment of the narrow-gap arc welding method according to the present invention is: It is characterized by being a gas-shielded arc welding system.

[0018] According to this aspect, by applying gas shielded arc welding, an oxidizing shielding gas such as a CO2·Ar+CO2 mixed gas (in the case of MIG welding of Al alloys, an inert gas such as an Ar·He+Ar mixed gas) is sent around the arc, and while blocking the molten part from the atmosphere, the wire is continuously supplied by a motor-driven roller or the like, and welding is performed while maintaining a constant arc length. As a result, the molten metal and the arc can be protected from the atmosphere, and the arc can be stably maintained, leading to an improvement in weldability.

[0019] Also, another aspect of the narrow groove arc welding method according to the present invention is characterized in that it is either semi-automatic welding or robot welding.

[0020] According to this aspect, by being either semi-automatic welding or robot welding, high-precision and efficient high-current arc welding can be realized. When applying robot welding using a gas shielded arc welding machine, even more efficient high-current arc welding can be realized. Here, the welding robot at least has a manipulator equipped with a welding torch at its tip, a controller that executes the operation control of the manipulator, and a programming pendant that stores a series of welding operations in the manipulator, and a series of operations will be taught by teaching.

Effects of the Invention

[0021] As can be understood from the above description, according to the narrow groove arc welding method of the present invention, while ensuring good workability and reducing the possibility of welding defects, the welding amount can be reduced.

Brief Description of the Drawings

[0022] [Figure 1] It is a diagram showing an example of a groove to which the narrow groove arc welding method according to the embodiment is applied. [Figure 2] It is a diagram showing another example of a groove to which the narrow groove arc welding method according to the embodiment is applied. [Figure 3]This figure shows the results of welding tests that verified the current and voltage ranges that do not cause welding defects in a root gap narrower than conventional specifications. [Modes for carrying out the invention]

[0023] The narrow-gap arc welding method according to the embodiment will be described below with reference to the attached drawings. In this specification and drawings, substantially identical components may be denoted by the same reference numerals to avoid redundant explanations.

[0024] [Narrow-gap arc welding method according to an embodiment] An example of a narrow-gap arc welding method according to the embodiment will be described with reference to Figures 1 and 2. Here, both Figures 1 and 2 are diagrams showing an example of a groove to which the narrow-gap arc welding method according to the embodiment is applied.

[0025] The example of a groove shown in Figure 1 is an example of narrow-groove arc welding of the end face 12 of a first steel base material 10 and a V-groove 22 at the end of a second steel base material 20. There is no groove on the end face 12 of the first base material 10, a root gap G is set between the end face 12 and the V-groove 22, the groove angle of the V-groove is θ1, and arc welding is performed with a backing plate 30 placed at the bottom.

[0026] Here, in addition to the illustrated example, for example, the V-groove 22 of the second base material 20 may be placed on the wide surface 11 of the first base material 10 with a root gap G provided, and arc welding may be performed with a backing plate 30 similarly placed at the bottom of the root gap G.

[0027] The plate thickness T of the first base material 10 and the second base material 20 can be set to a range of, for example, 6 mm to 60 mm, so that base materials of various thicknesses, from thin plates to thick plates, can be welded.

[0028] The groove angle θ1 of the V-groove 22 is in the range of 30 to 35 degrees, and this groove angle range is within the range of normal specifications as defined in JASS6.

[0029] On the other hand, the root gap G will be in the range of 4mm to 6mm, which is narrower than the standard 7mm specified in JASS6, but will not be set to an excessively narrow root gap.

[0030] In this narrow-gap arc welding, the arc output current is set to a range of 380A to 410A, and the arc output voltage is set to a range of 42V to 45V for arc welding.

[0031] Regarding the output current, it will be set in a high current range slightly higher than the 300A to 350A range used in general arc welding, and regarding the output voltage, it will be set in a high voltage range slightly higher than the 40V or less range used in general arc welding.

[0032] This output current range and output voltage range are determined based on the results of welding tests conducted by the inventors, as described below. This range reduces the likelihood of both hot cracking and undercutting, which are welding defects, occurring in narrow-gap arc welding with a root gap G narrower than that of normal specifications.

[0033] Narrow gap arc welding is performed by either semi-automatic welding or robotic welding, and one of the following types of welding is applied: submerged arc welding, gas shielded arc welding (CO2 arc welding), MAG (Metal Active Gas Welding) arc welding, MIG (Metal Inert Gas Welding) arc welding, or TIG (Tungsten Inert Gas) arc welding. Among these, gas shielded arc welding is preferred because it protects the molten metal and arc from the atmosphere and maintains the arc stably, resulting in good weldability.

[0034] Furthermore, the welding speed should be set to a range of 20 cm / min to 35 cm / min, and the heat input should be maintained within an appropriate range.

[0035] According to this narrow-gap arc welding method, by maintaining the groove angle θ1 of the V-shaped groove 22 within the range of 30 to 35 degrees in accordance with the specifications of JASS6, there is no hindrance for the worker to visually inspect the welding area, the welding torch can be smoothly inserted into the groove, and thus good workability can be ensured.

[0036] Furthermore, by setting the root gap G to a range of 4 mm to 6 mm, which is narrower than the general specifications defined in JASS6, the number of welding passes can be reduced, and the amount of welding can be reduced. Here, the minimum width of the root gap G is set to 4 mm, and since it is not made excessively narrow, high-temperature cracking, which is likely to occur when the root gap G is excessively narrow, can be suppressed.

[0037] Furthermore, by setting the arc output current to a range of 380A to 410A, which is slightly higher than the usual 350A or less, efficient narrow-gap arc welding can be achieved. Since the output current is not excessively high, high-temperature cracking, which is likely to occur when the output current is excessively high, can be suppressed.

[0038] Furthermore, by setting the arc output voltage to a range of 42V to 45V, which is slightly higher than the usual 40V or less, efficient narrow-gap arc welding can be achieved. This expands the weld bead width, suppressing hot cracking, and because the output voltage is not excessively high, it suppresses undercutting, which is likely to occur when the output voltage is excessively high.

[0039] On the other hand, another example of a groove shown in Figure 2 is a narrow-groove arc welding example of a V-groove 27 formed by a groove 14 at the end of a first steel base material 10A and a groove 24 at the end of a second steel base material 20.

[0040] After setting the sum of the groove angles θ2 and θ3 of both grooves 14 and 24 to be in the range of 30 to 35 degrees, similar to the groove angle θ1, narrow groove arc welding is performed with the root gap G, arc output current, and output voltage set to the ranges already described.

[0041] This narrow-gap arc welding method also allows for a reduction in the amount of welding while ensuring good workability and minimizing the possibility of welding defects.

[0042] [Welding Test and Results] The inventors used two types of wires commonly used in arc welding, with diameters of 1.2 mm and 1.4 mm. They set the groove angle of the V-groove to 30 degrees, the root gap to 5 mm, and performed narrow-gap arc welding by varying the arc output current and output voltage. They conducted welding tests to check for the occurrence of hot cracks and undercuts in each narrow-gap arc weld. The test results are shown in Figure 3.

[0043] As shown in Figure 3, in narrow-gap arc welding with a groove angle of 30 degrees and a root gap of 5 mm using two different diameter wires, the output current range in which hot cracking and undercuts, which are welding defects, do not occur (or are unlikely to occur) is identified as 380A to 410A, and similarly, the output voltage range in which hot cracking and undercuts do not occur (or are unlikely to occur) is identified as 42V to 45V.

[0044] Furthermore, in this welding test, a similar narrow-gap arc welding was performed with a root gap of 3 mm. As a result of the test at this root gap, hot cracking was confirmed in the first layer. Therefore, it was determined that the root gap should be less than 7 mm in order to reduce the amount of welding, but with a minimum width of 4 mm.

[0045] Based on the above construction test results, it has been demonstrated that by performing narrow-gap arc welding with a groove angle of 30 to 35 degrees (conventional specifications), a root gap of 4 mm to 6 mm, an arc output current range of 380 A to 410 A, and an arc output voltage range of 42 V to 45 V, it is possible to reduce the amount of welding while ensuring good workability and minimizing the possibility of welding defects.

[0046] Furthermore, other embodiments may be used in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited in any way to the configurations shown herein. In this regard, modifications can be made without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of Symbols]

[0047] 10,10A: First base material 11: Surface (wide surface) 12: End (end face) 14: End (end face, bevel) 20,20A: Second base material 22: End (end face, bevel, V-shaped bevel) 23: Bevel 24: End (end face, bevel) 27:V-shaped bevel 30: Backing metal

Claims

1. A narrow-gap arc welding method comprising: providing a V-groove at one end of a first base material and a second base material; and performing narrow-gap arc welding between the V-groove on one end of the first base material and the other end or surface of the second base material, The groove angle of the aforementioned V-shaped groove is in the range of 30 to 35 degrees. The root gap is in the range of 4 mm to 6 mm. Set the arc output current to a range of 380A to 410A. A narrow-gap arc welding method characterized by performing arc welding with the arc output voltage set to a range of 42V to 45V.

2. A narrow-groove arc welding method comprising providing grooves at both ends of a first base material and a second base material, forming a V-shaped groove by the ends of the first and second base materials, and performing narrow-groove arc welding in the V-shaped groove, The groove angle of the V-shaped groove is in the range of 30 to 35 degrees. The root gap is in the range of 4 mm to 6 mm. Set the arc output current to a range of 380A to 410A. A narrow-gap arc welding method characterized by performing arc welding with the arc output voltage set to a range of 42V to 45V.

3. The narrow groove arc welding method according to claim 1 or 2, characterized in that a backing plate is placed at the bottom of the V-shaped groove or the L-shaped groove and arc welding is performed.

4. The narrow gap arc welding method according to claim 1 or 2, characterized in that it is a gas shielded arc welding method.

5. The narrow gap arc welding method according to claim 4, characterized in that it is either semi-automatic welding or robotic welding.

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