JP2007038288A - Gougingless complete penetration welding method using high current pulse mag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gougingless complete penetration welding method using a high current pulse MAG for a T-joint having an I-shape bevel, a single bevel or a K-shape bevel which does not require a backside chipping work. <P>SOLUTION: The method requires the following conditions when applied for a plate around 17 mm in thickness: (1) a heat input for welding is 1,500-5,000 J/mm; (2) a backside bead leg length is 1.5-6.0 mm; (3) an optimum welding current is in a range of 360±25 A; (4) an optimum welding speed is in a range of 40±10 cpm; (5) an optimum pulse peak voltage is in a range of 40-55 V; (6) an optimum pulse frequency is in a range of around 300-400 Hz; (7) an optimum pulse width is in a range of 1.0-1.5 ms; (8) an optimum target position of wire is in a range of 0 to +1 mm horizontally to the operator side and 0 to +1 mm upward from a root; (9) an optimum moving angle is in a range of 0 to +5°to advancing angle side with respect to a retreating angle of 20°; and (10) an optimum shield gas flow rate is in a range of 20-25 l/min. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gouging-less welding method that is effective even for a thick plate by a large current pulse MAG.

There is a demand for an excellent welding method capable of meeting the recent demands for earthquake-resistant structures and the demand for improving the efficiency of welding work. In addition, there is a need for a welding method that does not require fishing on the back and has excellent workability.
In particular, not only corner joints and butt joints, but also T joints, there is a demand for completely penetration weld joints that are free from defects even with thick plates (about 20 mm or less).
Square joints and butt joints have only two heat dissipating directions from the welded part, but in the case of T joints, the heat dissipating direction from the welded part is three directions, so the cooling rate of the weld metal is large. Therefore, it is more difficult to obtain complete penetration than in the case of corner joints or butt joints under the same welding conditions.
As conventional techniques, for example, Patent Documents 1 and 2 have been proposed.

(JP 2004-106008) (JP 2004-98124)

The technology of Patent Document 1 is
In a welded joint for butt welding the contact portion between the surface of the first base material and the end surface of the second base material, the first groove formed on one side of the contact portion of the second base material The first welding part formed by melting the abutting part by the arc of the welding wire that has been exposed and extruding the melt to the side opposite to the welding side, and the abutting part in the second base material A second welding is performed by melting the contact portion on the second groove side and a part of the first welding portion with an arc of a welding wire facing the second groove formed on the other side. The invention relates to a welded joint in which a contact portion between the first base material and the second base material is butt welded with a welded portion.
The technology of Patent Document 2 is
In a method of welding a first base material having a groove on one side in contact with a second base material in a T-shape, a temporary weld portion between the first base material and the second base material is formed with a predetermined thickness. After removing to the thickness, the welding wire is exposed to a groove weld formed by the first base material and the second base material, and the arc from the welding wire is moved while moving the welding wire in the welding direction. In this case, the groove welded portion is melted from the groove side and the melt is pushed out to the groove back side to form a back bead.

In the case of the invention described in Patent Document 1, the first welding and the second welding are necessary. Further, the specification of the target thick member is unclear, and the specification of the pulsed current is unclear.
In the invention described in Patent Document 2, information on each element of the welding conditions is not sufficiently disclosed. Further, there is a problem that it can be performed only when the standing plate is thinner than the lower plate, and cannot be performed in other cases.
The present invention has been made to solve the above problems, and has taken the following measures.

According to the first aspect of the present invention,
The back is a gouging-less full penetration welding method using a high-current pulse MAG of a T-joint having an I-shaped groove, a re-shaped groove or a K-shaped groove, which does not require fishing,
The welding method satisfies the following conditions (1) to (10).
(1) Weld heat input is 1,500 to 5,000 J / mm
(2) Back bead leg length is 1.5-6.0mm
(3) The optimum welding current is within the range of 390 ± 25A when the plate thickness is about 20mm, within the range of 360 ± 25A when the plate thickness is about 17mm, and 320 ± 25A when the plate thickness is about 12mm. When the plate thickness is about 9 mm, the range is 310 ± 25 A. When the plate thickness is about 6 mm, the range is 360 ± 25 A. When the plate thickness is about 3.2 mm, the range is 300 ± 25 A.
(4) Optimal welding speed is in the range of 40 ± 10 cpm (5) Optimal pulse peak voltage is in the range of 40 to 55 V (6) Optimal pulse frequency is in the range of about 300 to 400 Hz (7) Optimal pulse width is in the range of 1.0 to 1.5 ms (8) The optimal wire aiming position is 0 to +1 mm in the horizontal direction from the root and 0 to +1 mm in the upward direction. In the range of 0 to + 5 ° on the advancing angle side with respect to ° and the plate thickness is less than 9 mm, the range of the receding angle of 0 ± 10 ° (10) The optimal shielding gas flow rate is in the range of 20 to 25 L / min. In the invention of 2,
The back is a gouging-less full penetration welding method using a high-current pulse MAG of a T-joint having a re-shaped groove or a K-shaped groove, which does not require fishing,
The welding method satisfies the following conditions (1) to (10).
(1) Welding heat input is 2,500-5,000 J / mm,
(2) Back bead leg length is 1.5-6.0mm,
(3) Optimal welding current is in the range of 360 ± 25A (when the plate thickness is 17mm), 320 ± 25A (when the plate thickness is 12mm), 310 ± 25A (when the plate thickness is 9mm),
(4) The optimum welding speed is in the range of 40 ± 10 cpm.
(5) The optimum pulse peak voltage is in the range of 40 to 55V.
(6) The optimum pulse frequency is in the range of about 300-320 Hz.
(7) The optimum pulse width is in the range of 1.0 to 1.5 ms.
(8) The optimum target position of the wire is in the range of 0 to +1 mm horizontally from the root and 0 to +1 mm upward.
(9) The optimum movement angle is in the range of 0 to + 5 ° on the advance angle side with respect to the receding angle of 20 °.
(10) The optimum shielding gas flow rate is in the range of 20-25 L / min.
By making a welding method that satisfies the condition
A gouging-less full penetration welding method using a high-current pulse MAG of a T-joint with a re-shaped groove or a K-shaped groove that does not require a backside has been realized.
Also,
When the plate thickness was 9 to 17 mm, welding without defects was possible under the above conditions.

According to the gouging-less welding method of the present invention, it is possible to perform welding without defects, and it is possible to obtain an effect of improving work efficiency by eliminating the need to hang the back.

In the following, an embodiment of a gouging-less welding method using a large current pulse MAG of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of a welded joint according to the present invention.
Reference numeral 1 denotes a first base material (vertical material), and 2 denotes a second base material (cross member) joined to the first base material 1 in a T-shape. The first base material 1 is provided with a mold groove forming surface 4 formed on one side (front side) so as to have a root face 3 at a butt end portion thereof.
The second base material 2 has a flat surface 5 that contacts the root face 3 of the first base material 1, and forms a T-shaped joint with the first base material 1.

Reference numeral 6 denotes a welded portion, and the welded portion 6 is provided on the groove side formed by the mold groove forming surface 4 of the first base material 1 and the flat surface 5 of the second base material 2. This welded portion 6 is formed by extruding from the front side to the back side a melt obtained by melting the groove side portion by an arc from a welding wire described later. A back bead is formed from the melt extruded to the back side.

In order to form the welded portion 6 described above, the root face 3 at the tip of the first base material is brought into contact with the flat surface of the second base material, and the contact portions (welded portion 6 on the groove side of the two base materials). The welding wire has a direct current so that the tip of the welding wire faces from the groove side, an arc is generated from the welding wire, and the two base metal parts near the contact portion are melted by the arc. A current obtained by superimposing a current and a pulsed current is applied.

A shield gas 9 in the range of 20 to 25 L / min is discharged around the welding wire.

A welding power source 10 is connected to the welding wire and the base material 1 or the base material 2 by cables 11 and 12. A voltage detector 13 detects the voltage of the welding current supplied from the welding power source 10 to the welding wire. A current detector 14 detects a welding current supplied from the welding power source 10 to the welding wire.

Next, when the plate thickness was 25 mm, the aspect ratio of the weld metal shape of the weld was R, and the presence or absence of hot cracking when the welding heat input was changed was verified. The results are shown in FIG. 2 with the aspect ratio α on the vertical axis and the welding heat input on the horizontal axis. 1, the aspect ratio α is D / W, where D is the horizontal depth of the weld metal shape of the weld and D is the height W in the vertical direction.
As shown in FIG.
When the welding heat input was 3,000 J / mm or more, the aspect ratio α was 1.3 to 2.8, and no hot cracking occurred.
When the welding heat input was less than 3,000 J / mm, the aspect ratio α was 1.4 to 2.5, and hot cracking occurred.
Considering that the range of the aspect ratio is almost the same, it is found that in the high current pulse MAG welding method, it is necessary to set the welding heat input to 3,000 J / mm in order to prevent hot cracking. It was.

Next, FIG. 3 shows the relationship between the height of the hot crack and the length of the back bead leg when the plate thickness is 25 mm.
As shown in FIG. 3, when the back bead leg length appeared 1.5 mm or more, hot cracking did not occur, and when it was less than that, hot cracking occurred. From this, a criterion for judging the occurrence of hot cracking from the appearance, that it can be judged that there is no hot cracking when the back bead leg length appears 1.5 mm or more, was obtained. Therefore, in an actual welding operation, it is preferable that the back bead appears as large as possible without causing overlap.
In FIG. 6, the characteristics of the base material having a thickness of 25 mm are shown together with other thicknesses. FIG. 7 shows the characteristics of the welding wire (YGW16) together with other characteristics. FIG. 8 shows the welding conditions.

Next, using the specimen (Fig. 1) manufactured with the steel material (plate thickness 17mm) shown in Figs. 9 and 10, the width of the welding condition where hot cracking does not occur in the case of 2mm root face was confirmed. The following ranges were found to be suitable.
That is,
(1) The welding heat input is 2,500 to 5,000 J / mm. If the welding heat input is less than 2,500 J / mm, hot cracking is likely to occur.
(2) The back bead leg length is 1.5 to 6.0 mm. Hot cracking occurred when the back bead leg length was less than 1.5 mm.
(3) The optimum welding current is in the range of 360 ± 25A. If it deviates from this range, too many back-beads will appear, or many defects will occur in the UT.
(4) The optimum welding speed is in the range of 40 ± 10 cpm. Outside this range, UT (ultrasonic inspection) and macro (LP) were confirmed.
(5) The optimum pulse peak voltage is in the range of 40 to 55V. When the pulse peak voltage was 55 V or higher, the back bead was good, but defects were confirmed by macro inspection.
The rise and fall of the current pulse waveform must be steep as shown in FIG.
(6) The optimum pulse frequency is in the range of about 300 to 320 Hz. When the pulse frequency was out of this range, it was difficult to generate back bead and the tendency for defects to increase was confirmed.
(7) The optimum pulse width is in the range of 1.0 to 1.5 ms. When the pulse width was less than 1.0 ms, it was difficult to generate the back bead and the tendency for defects to increase was confirmed.
(8) The optimum target position of the wire is in the range of 0 to +1 mm horizontally from the root and 0 to +1 mm upward. Outside of this range, it was difficult to produce back bead and defects were confirmed.
(9) The optimum movement angle is in the range of 0 to + 5 ° on the advance angle side with respect to the receding angle of 20 °. When tilted further, it became difficult to produce back-beads and defects were confirmed.
(10) The optimum shielding gas flow rate should be in the range of 20-25 L / min. If it was more than this, it would be difficult to produce backside beads and defects were confirmed.

In order to satisfy the above conditions, the welding power source 10 has an optimum welding current of at least 310 ± 25 A to 360 ± 25 A, an optimum pulse peak voltage of 40 to 55 V, and an optimum pulse frequency of about 300 to 320 Hz. The range and optimum pulse width must be able to output a welding power that can be controlled within a range of 1.0 to 1.5 ms.

By using the above welding power source and maintaining the optimum welding speed in the range of 40 ± 10 cpm and controlling the back bead leg length to be 1.5 to 6.0 mm, high temperature cracking can be achieved. It was possible to weld without defects.
Similar effects can be obtained not only for the T joint but also for the corner joint and the butt joint.

In the high current pulse MAG gougingless welding method according to the present invention,
In the case of a plate thickness of 17 mm, the appropriate welding conditions and the fluctuation range are as follows.
The rising and falling edges of a large current pulse waveform must be steep.
The optimum welding current is 360A for proper welding conditions and ± 25A for fluctuation range.
The optimum welding speed is in the range of 40 cpm for the proper welding conditions and ± 10 cpm for the fluctuation range.
The optimum pulse peak voltage is 50V under proper welding conditions and the fluctuation range is -10 to + 5V.
The optimum pulse frequency is in the range of about 300-320Hz for proper welding conditions.
The optimum pulse width is 1.5 ms for proper welding conditions and the fluctuation range is -0.5 to 0 ms.
The optimum target position of the wire is that the proper welding condition is the root part, and the fluctuation range is 0 to +1 mm horizontally from the root part and 0 to +1 mm upward.
The optimum travel angle is 20 ° for the proper welding conditions and the fluctuation range is 0 to + 5 ° on the forward angle side.
The optimum shielding gas flow rate is 25 L / min for proper welding conditions and the fluctuation range is in the range of -5 to 0 L / min.
In the case of a plate thickness of 12 mm, the optimum welding current is in the range of 320 ± 25 A, and the other conditions are approximately the same, although there is a fluctuation of about 10%. When the plate thickness is 9 mm, the optimum welding current is in the range of 310 ± 25 A, and the other conditions are approximately the same, although there is a fluctuation of about 10%.

Next, the range for changing the welding conditions when the root face RF is 0 to 4 mm based on the welding conditions when the root face RF is 2 mm (appropriate welding conditions) was confirmed as follows.
(1) When RF is 4 mm Good results can be obtained by increasing the welding current and decreasing the welding speed.
(2) When RF is 3 mm Good results can be obtained by increasing the welding current by 50 A and reducing the welding speed by 10 cpm from the appropriate welding conditions.
(3) When RF is 1 mm Good results can be obtained by reducing the welding current by 50 A and increasing the welding speed by 10 cpm from the appropriate welding conditions.
(4) When RF is 0 mm Good results can be obtained by reducing the welding current by 70 A and increasing the welding speed by 10 cpm from the appropriate welding conditions.
From the above results, it was confirmed that the fluctuation range of RF at a plate thickness of 17 mm was 0 to 4 mm.
Further, in the case of the plate thicknesses of 12 mm and 9 mm, appropriate welding could be confirmed at the RF fluctuation range of 0 to 4 mm as in the case of the plate thickness of 17 mm.

Further, in the conventional welding method using an inverter-controlled arc welding power source, as shown in FIG. 5, an 8-pass welding process is required when the plate thickness is 17 mm, but the large current pulse MAG used in the present invention is used. In the welding method using a welding power source, six passes are sufficient, and the working time can be greatly reduced.

Further, from the test results shown in FIG. 11, according to the large current pulse MAG gouging-less welding method of the present invention, as in the conventional gouging welding method, it is defect-free and the mechanical properties are equivalent or better. It was confirmed that.
Moreover, it was confirmed from the test results using a macro test piece having a plate thickness of 17 mm that the angular deformation can be suppressed by about 30% compared to the prior art.

Further, the welding method according to the present invention is effective as a gouging-less complete penetration welding method using a large current pulse MAG of a T joint having an I-shaped groove, a ledge-shaped groove or a K-shaped groove, which does not require a back side.
Moreover, an effect is acquired on the following various conditions.
(1) Weld heat input is 1,500 to 5,000 J / mm
(2) Back bead leg length is 1.5-6.0mm
(3) The optimum welding current is within the range of 390 ± 25A when the plate thickness is about 20mm, within the range of 360 ± 25A when the plate thickness is about 17mm, and 320 ± 25A when the plate thickness is about 12mm. When the plate thickness is about 9 mm, the range is 310 ± 25 A. When the plate thickness is about 6 mm, the range is 360 ± 25 A. When the plate thickness is about 3.2 mm, the range is 300 ± 25 A.
(4) Optimal welding speed is in the range of 40 ± 10 cpm (5) Optimal pulse peak voltage is in the range of 40 to 55 V (6) Optimal pulse frequency is in the range of about 300 to 400 Hz (7) Optimal pulse width is in the range of 1.0 to 1.5 ms (8) The optimal wire aiming position is 0 to +1 mm in the horizontal direction from the root and 0 to +1 mm in the upward direction. In the range of 0 to + 5 ° on the advancing angle side with respect to °, and when the plate thickness is less than 9 mm, the range of receding angle 0 ± 10 ° (10) The optimum shielding gas flow rate is in the range of 20 to 25 L / min

It is sectional drawing explaining the welding method of the T joint of embodiment of this invention. It is a figure which shows a verification result about the presence or absence of the generation | occurrence | production of the hot crack at the time of changing plate | board thickness to 25 mm when welding heat input is changed. It is a figure which shows the relationship between the height of a hot crack in the case of plate | board thickness 25mm, and a back bead leg length. It is a figure which shows the rising and falling waveform of the current pulse waveform used for this invention. It is comparison explanatory drawing of the number of passes of a welding process with the method by this invention, and the conventional method. It is the figure which showed the characteristic of the base material of the board thickness of 25 mm used with the thing of other thickness. It is the figure which showed the characteristic of the used welding wire (YGW16) with another. It is the figure which showed the welding conditions in embodiment. It is the figure which showed the characteristic of the steel material (root face 2mm) of the plate | board thickness used 17mm. It is the figure which showed the characteristic of the steel material of plate thickness 17mm used. It is a figure which shows the comparison result of the welding by the high current pulse MAG gouging-less welding method by this invention, and the welding by the conventional gouging welding method.

Explanation of symbols

1 First base material (longitudinal)
2 Second base material (cross member)
3 Root face 4 Re-shaped groove forming surface 5 Flat surface 6 Welded portion 9 Shielding gas 10 Welding power supply 11 and 12 Cable 13 Voltage detector 14 Current detector

Claims (3)

The back is a gouging-less full penetration welding method using a high-current pulse MAG of a T-joint having an I-shaped groove, a re-shaped groove or a K-shaped groove, which does not require fishing,
A welding method that satisfies the following conditions (1) to (10).
(1) Weld heat input is 1,500 to 5,000 J / mm
(2) Back bead leg length is 1.5-6.0mm
(3) The optimum welding current is within the range of 390 ± 25A when the plate thickness is about 20mm, within the range of 360 ± 25A when the plate thickness is about 17mm, and 320 ± 25A when the plate thickness is about 12mm. When the plate thickness is about 9 mm, the range is 310 ± 25 A. When the plate thickness is about 6 mm, the range is 360 ± 25 A. When the plate thickness is about 3.2 mm, the range is 300 ± 25 A.
(4) Optimal welding speed is in the range of 40 ± 10 cpm (5) Optimal pulse peak voltage is in the range of 40 to 55 V (6) Optimal pulse frequency is in the range of about 300 to 400 Hz (7) Optimal pulse width is in the range of 1.0 to 1.5 ms (8) The optimal wire aiming position is 0 to +1 mm in the horizontal direction from the root and 0 to +1 mm in the upward direction. In the range of 0 to + 5 ° on the advancing angle side with respect to °, and when the plate thickness is less than 9 mm, the range of receding angle 0 ± 10 ° (10) The optimum shielding gas flow rate is in the range of 20 to 25 L / min The back is a gouging-less full penetration welding method using a high-current pulse MAG of a T-joint having a re-shaped groove or a K-shaped groove, which does not require fishing,
A welding method that satisfies the following conditions (1) to (10).
(1) Weld heat input is 2,500 to 5,000 J / mm
(2) Back bead leg length is 1.5-6.0mm
(3) The optimum welding current is in the range of 360 ± 25A when the plate thickness is about 17mm, within the range of 320 ± 25A when the plate thickness is about 12mm, and 310 ± 25A when the plate thickness is about 9mm. (4) Optimal welding speed is in the range of 40 ± 10 cpm (5) Optimum pulse peak voltage is in the range of 40 to 55 V (6) Optimal pulse frequency is in the range of about 300 to 320 Hz (7) Optimal pulse width is in the range of 1.0 to 1.5 ms range (8) Optimal wire target position is 0 to +1 mm horizontally from the root and 0 to +1 mm upward (9) Optimum travel angle is 0 on the forward angle side with respect to the receding angle of 20 ° -+ 5 ° range (10) Optimal shielding gas flow rate is in the range of 20-25 L / min The gouging-less full penetration welding method according to any one of claims 1 and 2, wherein the plate thickness is 9 to 17 mm.

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