JPH09155550A - End crack preventing method in high speed one side submerged arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a weld joint part from end crack so as to form a good weld joint part. SOLUTION: Plates 63a, 63b to be welded are arranged in the same plane while butting each end face subjected to edge preparation. A rectangular tab plate 61 is arranged so as to be abutted to end faces of the plate 63a, 63b to be welded including an end part 65 in the longitudinal direction of the joint part. A pair of slits 62a, 62b are arranged at both sides of extended line of the joint in parallel with the extended line. In the tab, plate 61, retaining parts 61a, 61b for plate to be welded are tack-welded to the plate 63a, 63b to be welded respectively. Further, the joint part is subjected to one side submerged welding with using three or four piece multi-electrodes under conditions of a wire diameter of a first electrode of 4.0 to 4.8mm, a wire diameter of a second electrode and thereafter of 4.8 to 6.4mm, a distance between a first and second electrodes of 20 to 70mm a distance between a second and third electrodes of 150 to 250mm and a welding speed of 90-200mm/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing cracks occurring at the end of a welded joint, and more particularly to a method for preventing terminal cracks in high speed single-sided submerged arc welding.

[0002]

2. Description of the Related Art Usually, when one-sided submerged arc welding is carried out by abutting the end faces of the plates to be welded to each other, the unsteady part of the weld metal, that is, the start and end parts of the welded joint are appropriately treated, and the crater Tabs are attached to the beginning and end of the joint to handle the.

FIG. 2 is a perspective view showing a welding method of a terminal end portion of a welded joint in a conventional submerged arc welding method. As shown in FIG. 2, the welded plates 13a and 13
In b, the end faces in the longitudinal direction subjected to the groove processing are butted against each other and arranged on the same plane. Then, the welded plates 13a, 13b including the end portion 15 in the longitudinal direction of the joint portion.
The rectangular tab plate 11 is arranged so as to abut the end surface of the. The tab plate 11 is attached to the end faces of the plates 13a and 13b to be welded by temporary welding or the like.

Thus, before welding, the plate 13a to be welded,
After the tab plate 11 is attached to the end surface of 13b, submerged arc welding is performed in the direction of the white arrow by the first electrode 21, the second electrode 22, and the third electrode 23, and the welding portion at the joint portion is welded. The metal 14 is formed.

Also, at the starting end of the welded joint, a tab plate is attached in the same manner as at the terminal end, and if a suitable treatment such as gouging is applied to the tab plate, a problem due to welding occurs in particular. There is no. However, FIG.
When the arc of the first electrode 21 rides on the tab plate 11 at the terminal end portion 15 of the welded joint shown in (1), at the same time, the plates to be welded 13a and 13b undergo a rapid rotational deformation in the arrow direction.

When the first electrode 21 rides on the tab plate 11, arc heat acts on the tab plate 11, and the tab plate 11 is thermally expanded by the arc heat. Therefore, the welded plate 13
The restraint force of the tab plate 11 restraining the a and 13b is momentarily released. Then, the welded plates 13a, 1
3b will be rotationally deformed centering around the end portion 15 of the welded joint due to the thermal stress contained therein due to heat input during welding.

Therefore, at the terminal end portion 15 of the welded joint due to the deformation of the welded plates 13a and 13b, as shown in FIG.
A crack 16 (hereinafter, referred to as “end crack”) may occur in the weld metal 14.

[0008] Such end cracking occurs particularly remarkably when performing welding by a high heat input welding process such as one-sided submerged arc welding. Therefore, many welding construction methods have been proposed to prevent terminal cracking.

FIG. 4 shows a conventional submerged arc welding construction method (Japanese Patent Publication No. 51-18234 and Japanese Patent Publication No. 53-1215) in which external pressure is applied to a plate to be welded and a tab plate by a pressing means to prevent terminal cracking. ) Is a figure which shows. This figure 4
As shown in FIG. 3, the plates to be welded 33a and 33b are arranged on the same plane by abutting the end faces in the longitudinal direction, which have been groove processed, against each other. Then, the rectangular tab plate 31 is arranged so as to come into contact with the end faces of the plates to be welded 33a and 33b including the longitudinal end portion 35 of the joint portion. Also,
This tab plate 31 is a plate to be welded 33a, 3
It is attached to the end face of 3b.

Then, on the side end faces of the plates to be welded 33a and 33b, from the direction perpendicular to the welding line 34 in the joint,
External pressures of the same magnitude and opposite directions are applied to the straight lines by the pressing means 38a and 38b.
a and 33b are sandwiched. Further, the pressing means 37a is also attached to the tab plate 31 from a direction perpendicular to the extension line of the welding line 34.
And 37b, external pressures of the same magnitude and in opposite directions are applied in a straight line, and the tab plate 31 is clamped.

In this way, the plates to be welded 33a, 33b
And the first and second tab plates 31 with external pressure applied and restrained.
By performing submerged arc welding with the third electrodes 41, 42, 43, rotational deformation of the plates 33a, 33b to be welded is prevented and terminal cracking of the welded joint is prevented.

However, welding with such a construction method requires a considerable amount of equipment, and it is also necessary to adjust the external pressure. If the adjustment is inadequate, the welded plate 33 will be affected by the external pressure.
In some cases, a and 33b may undergo vertical deformation in the vertical direction, causing terminal cracks in the weld metal.

Another conventional submerged arc welding method for preventing end cracking is a method in which a sealing cascade bead is formed in advance at the end of a welded joint (Japanese Patent Laid-Open No. 5-285662). FIG. 5 is a cross-sectional view showing an end portion of a welded joint according to this welding construction method. As shown in FIG. 5, the welded plate 53 and another welded plate (not shown) welded together with the welded plate 53.
The respective end faces are subjected to groove processing such as the Y-shaped groove 56, and are butt-joined. Then, welding with low heat input is applied to the upper portion of the root face 54 of the groove 56 in the vicinity of the end portion 55 of this joint portion, and the step-shaped sealing cascade bead 5 is formed.
Form 2 After that, the tab plate 5 is attached to the end portion 55 of the joint portion.
After abutting against each other and attaching by temporary welding or the like, main welding by submerged arc welding is performed on the groove of the joint portion. in this way,
By forming the sealing cascade beads 52 in advance on the end portion 55 of the joint portion, the welding of the joint portion can be completed while retaining the restraining force at the end portion 55, and thus the deformation of the end portion is suppressed. be able to.

However, the sealing cascade beads 52
Since the back bead is not formed at the terminal end portion of the welded joint where is formed, it is necessary to rework. In addition, if the welding conditions for welding on the sealing cascade beads 52 by the main welding are inappropriate, the sealing cascade beads 52 are almost melted at the time of welding. For this reason,
The binding force at the terminal end portion 55 is completely lost, and terminal cracking occurs in the weld metal.

Further, by using three or more electrodes, 90c
Japanese Patent Application Laid-Open No. HEI-3 is a method for performing welding at a welding speed of m / min or more.
No. 238174, the total value of welding current × voltage at each of the first and second electrodes or the third and fourth electrodes preceding at the time of welding is high, and the thermal energy applied to the welded plate is high. Will become bigger. For this reason,
The amount of deformation of the plate to be welded at the terminal end of the welded joint becomes large, and it is difficult to prevent terminal cracking even if appropriate processing is performed on the tab plate and the terminal end.

Furthermore, Japanese Patent Publication No. 52-30375 discloses that a tab plate is provided with a pair of slits.
A method of preventing end cracking is disclosed. FIG. 6 is a top view showing a tab plate used in this method for preventing termination cracking. As shown in FIG. 6, the welded plates 63a and 63b
Are arranged on the same plane with their end faces in the longitudinal direction, which have been groove processed, butted against each other. Then, the welded plates 63a, 63b including the end portion 65 in the longitudinal direction of the joint portion.
A rectangular tab plate 61 is arranged so as to abut the end surface of the. The tab plate 61 includes welded plates 63a and 63b.
Slits 62a and 62b are provided on both sides of the extension line of the welding line 64 at the joint portion of. Further, the ends of the both end regions 61a and 61b of the tab plate 61 are temporarily welded to the end faces of the plates 63a and 63b to be welded at welded portions 66a and 66b, respectively.

After the tab plate 61 provided with such a pair of slits is attached to the end faces of the welded plates 63a and 63b, a submerged arc is formed along the welding line 64 at the joint portion of the welded plates 63a and 63b. Weld. Then, as compared with the case where welding is performed using a tab plate without slits, although the binding force against the rotational deformation of the plates 63a and 63b to be welded is weak, the arc heat is also received when the arc moves to the tab plate 61. The central region 61c of the tab plate 61 and both end regions 61a, 6 of the tab plate 61 that restrain the end portion of the weld joint.
Since it is thermally separated from 1b, a stable restraining force can be applied to the end portion until the welding is completed, and the occurrence of end cracking is prevented.

[0018]

However, in the welding method disclosed in Japanese Patent Publication No. 52-30375, when the heat input to the welding is large, the welding plates 63a and 63b are rotationally deformed by the welding heat. The thermal stress to do so increases. As described above, the welded plates 63a, 6
3b has a low restraining force against the rotational deformation, and the welded plate 63
If the thermal stresses of a and 63b become larger than the restraining force of the tab plate 61, the deformation of the end portion 65 cannot be suppressed, and the end portion 65 of the welded joint is cracked.

The present invention has been made in view of the above problems, and can prevent terminal cracking of a welded joint and prevent terminal cracking in high-speed single-sided submerged arc welding capable of forming a good welded joint. The purpose is to provide a method.

[0020]

A method for preventing terminal cracks in high-speed single-sided submerged arc welding according to the present invention is directed to the end face of a welded plate to the end faces of other welded plates, and the end of the joint in the longitudinal direction. The end surface of the plate to be welded and the other plate to be welded, by attaching a tab plate provided with slits on both sides of the extension line of the joint portion, respectively,
In a method of preventing terminal cracking of a welded joint when submerged arc welding the joint, a wire diameter of the first electrode is 4.0 to 4.8 m using 3 or 4 electrodes.
m, the diameter of the wires of the second, third and fourth electrodes is 4.8 to 6.4 mm, and the distance between the first and second electrodes is 20.
Each electrode is arranged so that the distance between the second electrode and the third electrode is 150 to 250 mm, and the welding speed is 9 mm.
It is characterized by welding at 0 to 200 cm / min.

Further, the welding current and welding voltage of the first electrode used for the high-speed one-sided submerged arc welding are respectively L _i
(A) and L _v (V), the welding current and welding voltage of the second electrode are T _i1 (A) and T _v1 (V), the welding current and welding voltage of the third electrode are T _i2 (A), respectively. And T _v2 (V) and the welding current and voltage of the fourth electrode are T _i3 (A) and T _v3 (V), respectively, and the thickness and welding speed of the plate to be welded are t (mm) and v, respectively. (Cm / min), then the first
And the welding heat input H1 (J / cm) by the second electrode is H1 =
L _i × L _v / t + T _i1 × T _v1 / t, the welding heat input H2 (J / cm) by the third electrode or the third and fourth electrodes is H2 = T _i2
Assuming that × T _v2 / t + T _i3 × T _v3 / t, the welding heat inputs H1 and H2 and the welding speed v are [(100v-3500)
/1.7]<H1<[(100v-2000)/1.
7], [100v / 3.5] <H2 <[(100v + 5
000) /3.5] and [H1 / H2] <1.45, and the thickness t is preferably t ≦ 25 mm.

[0022]

The present inventors have conducted various experimental researches to develop a method for preventing terminal cracks in high-speed single-sided submerged arc welding, which can prevent terminal cracks in the welded joint and form a good welded joint. I went.

Generally, in order to prevent cracking of the end portion of a welded joint when the end surface of a welded plate is butted against the end surfaces of other welded plates and submerged arc welding is performed, the end portion is rapidly deformed. It is considered effective to prevent this from occurring and to minimize the rotational deformation of the plate to be welded due to welding heat.

Therefore, first, regarding the abrupt deformation of the end portion, the end portion of the joint portion is brought into contact with the end surface of the welded plate, which is attached by temporary welding or the like to restrain the welded plate. We paid attention to the deformation of the tab plate that processes the crater. For example, in the case of using a flat tab plate, when the preceding electrode rides on the tab plate during welding, arc heat acts on the tab plate, so that the tab plate undergoes rapid thermal expansion. At the same time, the thermal stress due to the thermal expansion of the plate to be welded, which was restrained just before the riding of the electrode, is released. Therefore, the plate to be welded undergoes rapid rotational deformation around the end portion of the welded joint, so that end cracking occurs.

As a result of considering the cause of such a terminal crack, in order to prevent the terminal crack, the thermal stress which causes the welded plate to rotationally deform due to the welding heat is gradually released, and the tab plate itself. It is thought that it is necessary to suppress the deformation due to the welding heat. Therefore, in order to realize these, the tab plate is provided with a portion for constraining the plate to be welded (hereinafter referred to as "weld plate constrained portion") and a portion for processing craters (hereinafter referred to as "crater processing unit"). It has been concluded that it is optimal to have separate slits.

However, as described above, since the tab plate with slits has a low restraining force, when the welding heat input is large, the thermal stress of the plate to be welded and the amount of deformation of the tab plate are large, and the conventional welding process is performed. Even if a tab plate with slits is used in the method, it is difficult to prevent terminal cracking of the welded joint.

Therefore, the inventors of the present application should reduce the rotational deformation of the plate to be welded due to the welding heat and sufficiently restrain the plate to be welded even if the tab plate with slits is used when the welding heat input is large. If the welding method is a welding method in which the number of electrodes used is 3 or 4, and the welding heat input is suppressed by increasing the welding speed and the welding heat input is dispersed, It has been found that end cracking can be prevented.

Welding conditions for submerged arc welding in the method for preventing terminal cracks according to the present invention will be described below.

Number of electrodes: 3 or 4 The number of electrodes used for welding affects the welding speed and the bead shape. That is, as one of the methods for suppressing the deformation of the end portion of the welded joint due to the arc heat, increasing the welding speed can be mentioned.
It is necessary to set it to 0 cm / min or more. If two electrodes are welded while maintaining this welding speed, it is not possible to secure a sufficient amount of welding, and it is not possible to stably form the front bead and the back bead. On the other hand, if the number of electrodes is 5 or more, the welding speed is 200 cm / min or less, 3 in welding.
Alternatively, the heat input for welding becomes too high as compared with the case where four electrodes are used. Therefore, in order to weld at a welding speed of 90 cm / min or more to form a sound and stable weld bead, it is necessary that the number of electrodes is 3 or 4.

First electrode wire diameter: 4.0 to 4.
8 mm In the single-sided submerged arc welding according to the present invention, the first electrode and the second electrode ensure a sound back bead and obtain the necessary welding amount. However, if the wire diameter of the first electrode is less than 4.0 mm, the range of the current that can be properly used is low, so that it is possible to stably melt the back surface of the welded plate at a welding speed of 90 cm / min or more. Have difficulty. When the diameter of the wire of the first electrode exceeds 4.8 mm, an extremely high current is required to melt the back surface of the plate to be welded, and the arc spreads too much. Becomes too wide, which is not preferable in terms of bead integrity. Therefore, the diameter of the wire of the first electrode is set to 4.0 to 4.8 mm.

Wire diameter of the second, third and fourth electrodes:
4.8 to 6.4 mm After the second electrode, that is, when the diameters of the wires of the second, third, and fourth electrodes are less than 4.8 mm, the arc concentration is too good, and the height of the back bead increases. It becomes too large. Further, since the arc spreads poorly, it is not possible to secure a sound bead width, and the bead width becomes unstable. On the other hand, the diameter of the wire after the second electrode is 6.4 m.
When it exceeds m, the concentration of the arc becomes poor and it is not possible to secure a back bead of an appropriate height. Further, since the arc spreads too much, undercutting tends to occur. Therefore, the diameters of the wires of the second, third and fourth electrodes are set to 4.8 to 6.4 mm.

When the wire diameters of the first electrode and the second electrode exceed 4.8 mm and 6.4 mm, respectively, the welding current value is increased in order to maintain the current density flowing in the wires. Will be required. Then, the energy applied to the plate to be welded by the first electrode and the second electrode becomes large, which increases the amount of deformation at the terminal end portion of the welded joint of the plate to be welded, resulting in terminal cracking. Therefore, the diameters of the wires in the first electrode and the electrodes subsequent to the second electrode must be within the above range.

Distance between first and second electrodes: 20 to 70
In order to form a sound and stable back bead at a welding speed of 90 mm / min or more, it is not enough to use only the first electrode, and the second electrode needs to be assisted. In order to fully exhibit the roles of the first electrode and the second electrode, the molten pool at the time of welding needs to be a single pool. Usually, the length of the molten pool formed by the first electrode is
It is about 50 to 70 mm, and in order to form a stable single pool with the first electrode and the second electrode, the first electrode and the second electrode
It is necessary that the distance to the electrode is within 70 mm.
If the distance between the first electrode and the second electrode is less than 20 mm, the distance between the electrodes is too short, and the arc interference between the mutual electrodes causes the arcs of the first and second electrodes to become unstable, resulting in a back bead. It cannot be stably formed. Therefore,
The distance between the first and second electrodes is 20 to 70 mm.

Distance between second and third electrodes: 150 to 2
The distance between the second electrode and the third electrode of 50 mm is a necessary factor for the welding quality in order to prevent vertical cracking, secure the stability of the front bead, and obtain a sound weld without slag inclusion and fusion failure. Is. Further, this inter-electrode distance is also a factor necessary to disperse welding heat input between the leading first and second electrodes and the trailing third and fourth electrodes from the viewpoint of preventing terminal cracking.

The distance between the second electrode and the third electrode is 150 mm
If the welding speed is less than 90 cm / min,
The length of the molten pool formed by the first and second electrodes is 100 to 1
Since it is about 50 mm, the molten pool formed by the first, second, and third electrodes becomes a single pool, and the welded shape of the welded portion becomes vertically long, which may cause vertical cracking. In addition, the heat input cannot be dispersed, the deformation of the plate to be welded becomes large at the terminal end portion of the welded joint, and it becomes difficult to suppress the deformation of the plate to be welded with the tab plate with slits. On the other hand, the distance between the second electrode and the third electrode is 250 mm
If it exceeds, it is good to disperse the heat input, but in terms of welding quality, it becomes impossible to secure a sound penetration depth by the third electrode. Therefore, the stability of the arc of the third electrode is deteriorated, which may adversely affect the stable formation of the surface bead, or slag entrainment may occur. Therefore, the distance between the second and third electrodes is 150 to 250 m.
m.

Distance between third and fourth electrodes: 20 to 60
When welding using a mm 4 electrode, the distance between the third electrode and the fourth electrode is 20 m in terms of welding quality and welding workability.
If it is less than m, the blow-up during welding becomes strong and the workability deteriorates. Further, the arcs of both electrodes become unstable due to mutual arc interference of the third and fourth electrodes, and it becomes impossible to stably form the front bead. On the other hand, when the distance between the third electrode and the fourth electrode exceeds 60 mm, slag entrainment occurs and the width of the front bead becomes unstable. Therefore, the distance between the third and fourth electrodes is preferably 20 to 60 mm.

Welding speed: 90 to 200 cm / min In order to suppress the deformation of the end portion of the welded joint due to arc heat, it is effective to reduce the welding heat input or increase the welding speed. In particular, when the welding speed is increased, the portion where the arc heat acts on the plate to be welded, that is, the arc point is moved faster, so that the spread width of heat in the plate to be welded is reduced, and as a result, the welded joint in the plate to be welded is reduced. The deformation of the terminal end of the is reduced. In other words, even with the same amount of welding heat input,
In welding with a high welding speed, the amount of deformation of the plate to be welded becomes small. Especially, in order to obtain this effect, the welding speed is 90c.
It is necessary to be m / min or more, but if it exceeds 200 cm / min, it is not possible to obtain a stable shape front bead and back bead. Therefore, the welding speed is 90 to 200 cm
/ Min.

Next, the tab plate with slits attached to the terminal end of the welded joint will be described. The shape of the tab plate with slits used in the present invention is not particularly limited. It suffices that a slit is formed so that a cut is made from the end face of the tab plate that comes into contact with the plate to be welded and that the slit plate extends to the surface opposite to the end face. Therefore, this slit does not necessarily have to be parallel to the welding line of the plate to be welded.

Further, it is necessary that at least two slits are formed in the tab plate, the region sandwiched by the slits serves as a crater processing portion, and both end regions of the tab plate function as welded plate restraining portions. To do. That is, the crater processing portion has a function of preventing craters from being generated on the plate to be welded by stopping the energization of the arc after the electrode that has welded the plate to be welded climbs on the crater processing portion. On the other hand, the plate-to-be-welded restraint portion does not deform even after the electrode rides on the tab plate, and thus has a function of continuing to hold the plate-to-be-welded.

If the position at which welding is terminated by stopping the energization of the arc of the welding electrode exceeds the tip of the slit, the welded plate constraining portion is likely to be thermally deformed. It is preferable that the area is from the end of the tab plate that abuts the end face of the slit to the tip of the slit.

Next, the welding heat input will be described. Increasing the welding speed in order to suppress thermal deformation of the plate to be welded means that the arc point on the plate to be welded moves faster. The faster the movement of the arc point on the plate to be welded, the smaller the width of the spread of heat in the plate to be welded, and the smaller the deformation of the plate to be welded due to the welding heat. Therefore, even with the same welding heat input, the amount of deformation of the plate to be welded can be reduced by increasing the welding speed and performing welding.

Further, even if the heat input is the same and the welding speed is the same, dispersing the welding heat input is effective in reducing the deformation amount of the plate to be welded. Considering the soundness of the welding quality as a method of dispersing the welding heat input, one melting pool is used for the first and second electrodes, and one melting pool and two melting pools are used for the third or third and fourth electrodes. It is conceivable to weld them together.

By following the above welding conditions, cracks at the end of the welded joint can be prevented, but in order to prevent cracks at the end of the weld joint more reliably, the thickness of the plate to be welded and the heat input The ratio may be specified.

Plate thickness: 25 mm or less Generally, the heat input for welding is related to the plate thickness of the plate to be welded, and the thicker the thickness, the larger the heat input for welding. For this reason, in order to more reliably prevent cracks at the terminal end of the welded joint, the plate thickness of the plate to be welded is preferably 25 mm or less.

Next, the relationship between welding heat input and welding speed will be described. In the present invention, welding heat input is divided into two, heat input by the first electrode and the second electrode and heat input by the third electrode and the fourth electrode. Generally, when performing submerged arc welding using four electrodes, the heat input by the first and second electrodes is H1 (J / cm), and the heat input by the third and fourth electrodes is H2 (J / cm). Then, H1 and H2 are represented by the following mathematical formulas 1 and 2, respectively.

[0046]

## EQU1 ## H1 = L _i × L _v / t + T _i1 × T _v1 / t

[0047]

H2 = T _i2 × T _v2 / t + T _i3 × T _v3 / t where L _i : welding current (A) of the first electrode L _v : welding voltage (V) of the first electrode T _i1 : second Electrode welding current (A) T _v1 : Welding voltage of second electrode (V) T _i2 : Welding current of third electrode (A) T _v2 : Welding voltage of third electrode (V) T _i3 : Of fourth electrode Welding current (A) T _v3 : Welding voltage of the fourth electrode (V) t: Plate thickness (mm) (t ≦ 25 mm).

Heat input H expressed by the above equations 1 and 2
The relationship between 1 and H2 and the welding speed is the welding speed (cm /
It is preferable that the following mathematical formulas 3 and 4 are satisfied, where v is (minute).

[0049]

(3) (100v-3500) /1.7 <H1 <(1
00v-2000) /1.7

[0050]

(4) 100v / 3.5 <H2 <(100v + 500
0) /3.5

H1 is the upper limit value ((100v-
2000) /1.7) or more or H2 is the upper limit value ((100v + 5000) /3.5) or more of the above formula 4, the heat input is excessive and the amount of deformation of the welded plate increases. . On the other hand, H1 is the lower limit value ((10
0v-3500) /1.7) or less, or when H2 is the lower limit value (100v / 3.5) or less of the above-mentioned numerical formula 4, since the heat input to the welded plate is small, a sound welding bead is obtained. Is difficult. Therefore, it is preferable that the heat inputs H1 and H2 satisfy the above equations 3 and 4, respectively.

Heat input ratio: H1 / H2 <1.45 Even when the heat inputs H1 and H2 described above satisfy the above equations 3 and 4, respectively, the heat input ratio H1 / H2 is 1.45. It is preferably smaller. This is H1
When /H2≧1.45, the amount of weld metal formed by the first and second electrodes increases, and the penetration of the welded plate by the third or third and fourth electrodes becomes insufficient, This is because the crack susceptibility becomes high with respect to the deformation of the plate to be welded that occurs at the terminal end of the welded joint. Therefore,
The heat inputs H1 and H2 preferably satisfy H1 / H2 <1.45.

In the single-sided submerged arc welding according to the present invention, the front side flux, the backing flux and the electrode wire are required as the welding material. However, these welding materials have appropriate workability and weld metal according to the purpose. The present invention is not particularly limited as long as the above can be obtained.

[0054]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples that fall outside the scope of the claims of the present invention.

FIG. 1 is a top view showing a tab plate used in this embodiment. As shown in FIG. 1, the plates 3a and 3b to be welded are arranged in the same plane such that the end faces in the longitudinal direction subjected to the groove processing are butted against each other. Then, the rectangular tab plate 1 is arranged so as to come into contact with the end surfaces of the welded plates 3a and 3b including the longitudinal end 5 of the joint portion. The tab plate 1 is provided with a pair of slits 2a and 2b on both sides of the extension line of the joint portion in parallel with the extension line. Further, in the tab plate 1, the welded plate restraint portions 1a and 1
b is provisionally welded to the welded plates 3a and 3b, respectively. In addition, the dimension of this tab board 1 is horizontal a: 200 to 400 m.
m, length b: 200 to 400 mm, slit length c: 100
˜250 mm, distance d between slits: 50 to 80 mm.

After arranging the tab plates having the slits 2a and 2b at the joint ends of the plates 3a and 3b to be welded in this manner, submerged arc welding was applied to the joint along the welding line 4.
The welded plates 3a and 3b used at this time are all steel plates SM.
400 was used, and the composition of this component is shown in Table 1 below. The composition of the wire and the flux used in this welding are shown in Tables 2 and 3 below.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3] _{Other: CO 2, B 2 O 3} , Fe-Si, Fe-Mn or the like.

Using the above welding materials, single-sided submerged arc welding is performed on the plates 3a and 3b to be welded with 3 or 4 electrodes. The plate thickness of the steel plate at this time, the number of electrodes, the diameter of the wire of each electrode and the welding The welding conditions for speed are shown in Table 4 below. In addition,
Regarding welding conditions outside the scope of the claims of the present invention, the condition values are underlined.

[0061]

[Table 4]

The distances between the electrodes are shown in Table 5 below.
Regarding welding conditions outside the scope of the claims of the present invention, the condition values are underlined.

[0063]

[Table 5]

Table 6 below shows the welding current and welding voltage at the first, second, third and fourth electrodes.

[0065]

[Table 6]

The heat input H1 and the heat input H2 calculated by the above equations 1 and 2 are shown in Table 7 below. Table 7 below shows the upper and lower limits of the heat inputs H1 and H2 in Equations 3 and 4 and the heat input ratio H1 / H2.

[0067]

[Table 7]

The results of welding under the welding conditions shown in Tables 4, 5 and 6 are shown in Table 8 below. In addition, in Table 8 below, “∘” indicates that the terminal crack did not occur, “◯” indicates that the terminal crack sometimes occurred depending on the condition of the tab plate, and “x” indicates that the terminal crack occurred. "In the terminal status column. In addition, by observing cracks and bead shape of the welded portion, "◎" when the welded portion is excellent, "○" when the welded portion is good, and "x" when the welded portion is defective. Is shown in the column of welding evaluation in Table 8 below.

[0069]

[Table 8]

As shown in Table 8 above, Example Nos. 1 to 1
Regarding No. 4, good bead and melted shape were obtained, and a sound weld metal could be obtained without cracking at the terminal end of the welded joint.

In Examples Nos. 15 and 16, since the welding heat input H1 by the first and second electrodes is high,
When a small tab plate with a small restraint force was used, some cracks might occur at the end of the welded joint.

In Example No. 17, when the welding heat input H2 by the third electrode is low and the heat input ratio H1 / H2 is large, when a small tab plate with a small restraining force is used,
Some cracks may occur at the end of the welded joint.

Regarding Example No. 18, the third and fourth examples are given.
Since the welding heat input H2 by the electrode is high, when a small tab plate having a small restraining force is used, some cracks may occur at the terminal end of the welded joint.

On the other hand, in Comparative Example No. 1, since the number of electrodes used was 2 and the welding heat input H1 was high, the shapes of the front and back beads were not stable, and the underbeads due to lack of extra space, especially in the front beads. A cut etc. occurred.

In Comparative Examples Nos. 2 and 6, since the distance between the first and second electrodes was out of the scope of the claims, the shape of the back bead became unstable.

In Comparative Example No. 3, since the distance between the second and third electrodes was long, sufficient penetration could not be obtained, and slag entrainment and fusion failure occurred.

In Comparative Example No. 4, since the welding speed was low, the amount of rotational deformation of the plate to be welded was large, and cracking occurred at the end of the weld joint due to abrupt deformation.

In Comparative Example No. 5, since the distance between the second and third electrodes was short, the back bead formed by the preceding electrode was remelted and a stable back bead could not be obtained. Further, the molten pool became a single pool, and the welded shape of the welded portion became vertically long, so cracks occurred at the terminal end of the welded joint.

In Comparative Example No. 7, the front bead shape became unstable because the distance between the third and fourth electrodes was long.

In Comparative Example No. 8, although the welding heat inputs H1 and H2 were within the predetermined range, the welding speed was high, so that the normal front and back beads could not be formed.

[0081]

As described above, according to the present invention,
When submerged arc welding is performed by arranging a tab plate with a slit at the end of the joint by abutting the end face of the plate to be welded with the end face of another plate to be welded, the number of electrodes used, the diameter of each electrode wire, and the placement Since the interval and the welding speed are appropriately defined, it is possible to prevent the occurrence of cracks at the end portion of the welded joint, and it is possible to form a good welded portion.

Further, by appropriately defining the heat input during the welding, it is possible to more reliably prevent the cracking of the terminal end portion.

[Brief description of the drawings]

FIG. 1 is a top view showing a tab plate used in an embodiment of the present invention.

FIG. 2 is a perspective view showing a welding method of an end portion in a conventional submerged arc welding construction method.

FIG. 3 is a diagram showing weld cracks occurring at the terminal end of the welded joint.

FIG. 4 is a top view showing a welding method of a terminal portion in a conventional submerged arc welding construction method.

FIG. 5 is a cross-sectional view showing a welding method of a terminal portion in a conventional submerged arc welding construction method.

FIG. 6 is a top view showing a welding method of a terminal portion in a conventional submerged arc welding construction method.

[Explanation of symbols]

1, 11, 31, 51, 61; tab plates 2a, 2b, 62a, 62b; slits 3a, 3b, 13a, 13b, 33a, 33b, 53,
63a, 63b; Plate to be welded (steel plate) 4, 34, 64; Welding line 5, 15, 55, 65; End portion 6a, 6b, 66a, 66b; Temporary welded portion 14; Weld metal 16; Weld crack 21, 41 First electrode 22, 42; second electrode 23, 43; third electrode 37a, 37b, 38a, 38b; pressing means 52; sealing bead 54; root portion 56; groove

Claims (2)

[Claims] 1. An end face of a plate to be welded is abutted against an end face of another plate to be welded, and an end portion in the longitudinal direction of this joint portion is included, and an end face of the plate to be welded and another plate to be welded is connected to the joint. In the method of preventing terminal cracking of the welded joint portion when submerged arc welding the joint portion by attaching tab plates provided with slits on both sides of the extension line of the portion, the third or fourth electrode is used. The diameter of the wire of one electrode is 4.0 to 4.8 mm, the diameter of the wire of the second, third and fourth electrodes is 4.8 to 6.4 mm, and the first and second
High-speed single-sided welding, characterized in that the electrodes are arranged such that the distance between the electrodes is 20 to 70 mm and the distance between the second and third electrodes is 150 to 250 mm, and the welding speed is 90 to 200 cm / min. End crack prevention method in submerged arc welding. 2. The welding current and welding voltage of the first electrode used in the high-speed one-sided submerged arc welding are respectively L
_i (A) and L _v (V), the welding current and welding voltage of the second electrode are T _i1 (A) and T _v1 (V), and the welding current and welding voltage of the third electrode are T _i2 (A), respectively. ) And T _v2 (V) and the welding current and welding voltage of the fourth electrode are T _i3 (A) and T _v3 (V), respectively, and the thickness and welding speed of the plate to be welded are t (mm) and v (cm / min), then the first
And the welding heat input H1 (J / cm) by the second electrode is H1 =
L _i × L _v / t + T _i1 × T _v1 / t, the welding heat input H2 (J / cm) by the third electrode or the third and fourth electrodes is H2 = T _i2
Assuming that × T _v2 / t + T _i3 × T _v3 / t, the welding heat inputs H1 and H2 and the welding speed v are [(100v-3500)
/1.7]<H1<[(100v-2000)/1.
7], [100v / 3.5] <H2 <[(100v + 5
000) /3.5] and [H1 / H2] <1.45, and further, the thickness t is t ≦ 25 mm, the terminal cracking in high-speed single-sided submerged arc welding according to claim 1. Prevention method.