JPH07256456A - One-side submerged arc welding - Google Patents

Abstract

PURPOSE:To obtain weld beads of high quality with defectless penetration in sheet connection joining using at least three electrodes by executing tack welding in a groove, then executing high-speed welding by specifying the wire diameters of the respective electrodes, tack welding bead length and bead height. CONSTITUTION:The inside of the single Vee groove is subjected to one-side submerged arc welding by using at least the three electrodes. The wire diameter of the preceding first electrode is specified to 4.0 to 4.8mm, the wire diameter of the succeeding second electrode to 4.8 to 6.4m and the wire diameter of the third and subsequent electrodes to 6.4 to 8.0m. The single Vee groove shape having a bevel angle of 45 to 80 deg. and a route part of 3 to 7mm is subjected to sheet connection joining. At this time, the tack welding in the groove is executed under the conditions of the tack welding bead length of >=20mm and the bead height h of 3.0<=h<=300/V+5 [where V is a welding speed (cm/min)]. The inside of the groove is then welded at a speed of 100 to 200 (cm/min). The shape of the tack welding beads is preferably smoothed on the start side of the tack welding beads.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-sided submerged arc welding method in which three or more electrodes are used and a flux is used as a backing, and particularly, the welding speed is as high as 100 to 200 cm / min. The present invention relates to an efficient one-sided submerged arc welding method.

[0002]

2. Description of the Related Art In the one-sided welding method of submerged arc welding, when the welding speed is less than 100 cm / min, the front and back beads can be formed relatively stably, and As shown in FIG. 5, a weld metal having a good penetration shape can be obtained. In butt welding, it is necessary to intersperse temporary welding in the groove prior to main welding, but depending on the height and welding state of this temporary welding bead, one-sided submerged welding is performed. The quality of the weld bead obtained by the main welding by arc welding is not significantly impaired.

By the way, in recent years, there has been a strong demand for higher efficiency in single-sided submerged arc welding, and accordingly, high-speed single-sided welding has been studied. A number of research reports and proposals regarding speed and welding conditions have been made for the purpose of stably forming the back bead and securing the amount of welding in welding (for example, JP-A-3-238174 and JP-A-5-33).
7651).

As pointed out in these research reports or publications, if the welding heat input (J / cm) is represented by (welding current × welding voltage) / welding speed, high-speed welding (1
In the range of (00 to 200 mm / min), the welding heat input inevitably decreases. This means that the welding heat input per unit area in the groove is reduced, so if there is a discontinuous portion in the groove or a temporary welding bead that absorbs a large amount of heat, less than 100 cm / min. However, there is a problem that the tack bead has a great influence on the stable formation of the back bead, especially in the main welding, though it is not a problem at the speed of.

Further, as shown in FIG. 6, when the arc passes over the temporary bead having the temporary height h, the arc tip position becomes higher than the normal arc length by the height h. Forming a large temporary bead is not preferable in terms of stable formation of the back bead. Therefore, as shown in FIG. 7, undercutting or bead wobbling occurs. In addition, problems such as slag entrapment and excessive surface beading occur.

Further, the arc of the leading electrode may be stopped especially at the discontinuous portion due to the temporary bead. Then, in spite of the high-speed welding, inconveniences such as unstable formation of the back bead and arc stop will occur, so the welding work efficiency will decrease, and conversely the number of rework steps will increase compared to the case of conventional speed welding. become.

Further, if it is attempted to solve these problems by making the height of the temporary bead as low as possible, there are the following problems. That is, during the main welding, the temporary bead is subjected to thermal stress that acts as a tensile force in the direction perpendicular to the welding line, but if the height of the temporary bead is low, the temporary bead breaks due to the thermal stress received during the main welding. To do. In high-speed welding, the welding heat input is lower than in the case of welding at normal speed, so the thermal stress is low, but if the height of the tack bead is too low, the tack bead breaks. The breakage of the temporary bead becomes a factor that causes cracks in the weld metal formed by single-sided submerged arc welding.

As described above, in the conventional high speed submerged arc welding method, various problems associated with high speed welding have not been solved yet, and in order to form a stable bead and obtain a sound welding bead, Is insufficient.

The present invention has been made in view of the above problems, and is 100 to 200 cm / in single-sided submerged arc welding using three or more electrodes.
A high-efficiency one-sided submerged arc welding method that has a welding speed as high as a minute and has the same stability as a weld bead obtained at a speed of less than 100 cm / min, and that a high quality weld bead with sound penetration can be obtained. The purpose is to provide.

[0010]

The single-sided submerged arc welding method according to the present invention uses at least three electrodes, and the wire diameter of the preceding first electrode is 4.0 to 4.8 m.
m, and the wire diameter of the second electrode in the subsequent line is 4.8 to 6.4.
mm, the wire diameter of the third and subsequent electrodes is 6.4 to 8.
0 mm, groove angle of 45 ° to 80 ° and 3 to 7 m
In the one-sided submerged arc welding method for Y-shaped grooved plate joint welding having a root portion of m, a metal-based flux-cored wire, a solid wire, or a coated arc welding rod is used, and the temporary bead length is 20 mm or more,
Bead height h (mm) is 3.0 ≦ h ≦ 300 / V + 5
[However, V is welding speed (cm / min)], after temporarily welding the inside of the groove, the inside of the groove is 100 to 200.
It is characterized by welding at a speed of (cm / min).

[0011]

The present inventors have obtained the following findings as a result of repeating various experimental studies in order to solve the above-mentioned problems of the prior art.

In single-sided submerged arc welding using three electrodes or more, and particularly using flux for the backing, when the welding speed is as high as 100 to 200 cm / min, a stable and sound front bead and back bead are obtained. In order to obtain a bead, a conventional technique (for example, Japanese Patent Laid-Open No. 32381/1990) is used.
No. 74, Japanese Patent Laid-Open No. 3-268876), it is not enough to select the welding conditions, and the shape of the temporary bead in the groove affects the shape.

On the other hand, it has been found that a stable and sound weld bead can be obtained by defining the height h of the temporary bead in the groove as in claim 1. That is, the upper limit of the temporary bead height h is set to 30 from the relationship with the welding speed V.
By limiting to 0 / V + 5 and limiting the lower limit of the tack bead height to 3.0 mm from the viewpoint of securing the strength of the tack bead, even in high speed welding, the same stability as the welding bead obtained at the conventional welding speed can be obtained. In addition, a sound and high quality weld bead can be obtained.

The shape of the temporary bead is such that the starting side of the temporary bead is smooth, so that continuous welding is possible and the problem of arc stop is eliminated. The height and shape of these temporary bead can be adjusted by a welding method and a method of removing unnecessary portions of the temporary bead with a grinder or the like. The second aspect defines the conditions for eliminating the arc stop by making the shape of the temporary bead smooth.

The reasons for limiting the numerical conditions defined in claims 1 and 2 of the present invention will be described below. (1) Welding speed and tack bead height In high-speed welding, if tack welding performed in the groove to be welded is processed under the same conditions as in the conventional speed, the stability of the back bead is remarkably increased. make worse. Then, the inventors of the present application have found that the unstable part of the back bead and the temporary mounting part in the groove are substantially coincident with each other, and the unstableness of the rear bead is due to the absorption of arc heat by the temporary bead, remelting and arc length. It was found that the variation of Therefore, in order to obtain a stable bead shape and a sound joint, it is necessary to make the shape of the temporary bead appropriate.

As a result of investigating the welding quality by varying the welding speed and the tacking height, a correlation was found between the welding speed and tacking height and the welding quality. That is, in FIG. 1, when the welding speed was 100 to 200 cm / min, the horizontal axis represents the welding speed and the vertical axis represents the height of the temporary bead, so that a stable bead shape and sound melting were obtained. It is the graph figure which represented the thing with (circle), and represented the thing which is not. Figure 1
As shown in FIG. 3, when the tacking height h is a line segment represented by h = 300 / V + 5 or less, a weld metal exhibiting a stable bead shape and a sound penetration shape can be obtained. If the upper limit of this tacking height is exceeded, undercutting of the back bead will occur, bead waviness will occur, and the weld metal formed by the leading electrode will rise to near the surface of the steel plate, Penetration at the electrode is not sufficiently obtained, and slag entrainment and cracking occur.

On the other hand, the lower limit of the tacking height h needs to be a tacking bead height sufficient to withstand thermal stress, and as a result, 3.0 mm is the lower limit of the tacking height.

Regarding the welding conditions, it is desirable that the sum of the current values of the first electrode and the second electrode is in the range of 2000 to 3000 (A).

(2) Temporary bead shape The temporary bead provided in the groove has different treatment on the start side or the end of the bead depending on the operator. In the tack bead shown in FIG. 3, when the ratio L2 / L1 of the length L2 of the parallel portion of the tack beat to the welding length Ll of tack welding exceeds 0.8, both ends of the tack bead suddenly increase. It will start up, resulting in a very discontinuous weld line. For this reason, the arc of the leading electrode becomes unstable, and the arc may stop due to a sudden arc fluctuation. Therefore, in order to obtain a smooth temporary bead shape, the ratio L2
/ L1 is preferably 0.8 or less.

As shown in FIG. 4, the cross-sectional shape of the temporary bead is such that the height difference h1 between the apex of this bead and the point where the bead contacts the groove surface is 1.5 mm or less. Is desirable.

For the tack welding, any of a metal-based flux-cored wire, a solid wire, a coated arc welding rod, a titania-based flux-cored wire, or the like may be used. In particular, the metal-based flux-cored wire, the solid wire or the coating is used. It is preferable to use an arc welding rod because the amount of slag is small.

(3) Groove shape (root length and groove angle) The groove shape of the butt portion has a great influence on the stability and penetration of the front bead and the back bead formed by single-sided submerged arc welding. .

In single-sided submerged arc welding, the Y-shaped groove shape is most preferable in order to obtain stable front and back beads and sound penetration. As shown in FIG. 2, the root portion of the Y-shaped groove is the current, voltage, and
Since it affects the speed, stable back bead formation becomes difficult when the root portion exceeds 7 mm. On the other hand, if the root portion is kept as low as possible, the accuracy of the root portion cannot be ensured, and similarly it becomes difficult to form a stable back bead. For this reason, it is necessary to limit the root portion to 3 to 7 mm, which forms a stable back bead.

Since the groove angle affects the formation of the front bead, the penetration shape, and the welding amount, a groove with an angle of more than 80 ° has a large internal cross-sectional area of the groove and requires a larger welding amount, which results in high speed. Not suitable for welding. On the other hand, if the angle is narrower than 45 °, the point at which the arc is generated becomes too high, which is not preferable for ensuring stable formation of the back bead and ensuring a sound penetration shape. Therefore, the groove angle is 45
It is necessary to make it up to 80 °, which ensures a stable back
A surface bead and a sound penetration are obtained.

(4) Wire Diameter of First Electrode, Second Electrode, Third Electrode and Electrode Subsequent to Third Electrode If Present, In the high speed single-sided submerged arc welding method according to the present invention, the first electrode and the third electrode The two electrodes ensure a sound back bead and obtain the required amount of welding. However, if the wire diameter of the preceding first electrode is less than 4.0 mm, the range of current that can be properly used is narrow, so 10
In high-speed welding of 0 cm / min or more, it is difficult to stably melt the steel sheet back side. On the contrary, when the wire diameter of the first electrode exceeds 4.8 mm, an extremely high current is required to melt the steel sheet to the back surface side, and since the arc spreads too much, the flow width becomes wide,
As a result, the back bead width becomes excessive. Therefore, the wire diameter of the first electrode needs to be 4.0 to 4.8 mm.

If the wire diameter of the second electrode is less than 4.8 mm, the concentration of the arc is too good, and the back bead is excessively large and the arc spreads poorly. The width cannot be secured and the bead width becomes unstable. On the other hand, the wire diameter of the second electrode is 6.4 mm
If it exceeds, the concentration of the arc becomes poor, and it is not possible to secure an appropriate extra height of the back bead, and since the arc spreads too much, undercut is likely to occur. Therefore, the wire diameter of the second electrode needs to be 4.8 to 6.4 mm.

The wire diameter of these electrodes is 6.4 to 8.0 mm including the third electrode and the electrodes subsequent to this third electrode, if any.
If the wire diameter of these electrodes is less than 6.4 mm, a wide front bead width cannot be ensured and the bead stability is poor in high speed welding due to poor arc spread.
Further, when the wire diameter of these electrodes exceeds 8.0 mm, the concentration of the arc deteriorates, so that it is not possible to secure a sufficient penetration depth without the risk of vertical cracking. Therefore, it is necessary that the wire diameter of the third electrode and the electrode following the third electrode be 6.4 to 8.0 mm.

(5) Temporary welding bead length The temporary welding bead in the groove is used to reduce the gap between the butted plates and to obtain a sound bead shape and penetration in the one-sided submerged arc welding. Depending on the shape of this tack welding bead, it becomes an obstacle in single-sided submerged arc welding (main welding), but after the tack welding, the bead shape is formed into an appropriate shape by a blinder, or the tack welding method is used. By appropriately controlling the conditions of (1) and processing the temporary bead into a predetermined shape, this problem is solved.

On the other hand, the length of the provisional bead is not inconvenient even if the provisional bead is applied to the entire length of the welding line for single-sided submerged arc welding if the shape is appropriate. . However, the temporary bead length is 20 mm
If shorter, single-sided submerged arc welding (main welding)
The temporary bead may be broken by the thermal stress (tensile force in the direction perpendicular to the welding line) generated at. Then,
When the temporary bead is broken, the plate undergoes a rapid deformation, which causes cracks in the weld metal. Therefore, it is necessary to set the length of the temporary bead in the groove to 20 mm or more. It is desirable that the interval between the temporary beads is 2000 mm or less.

[0030]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples. The steel plates shown in Table 1 below are shown in Table 2 below.
One-sided submerged arc welding was performed using the wire shown in Fig. 3 and the flux shown in Table 3 below. The welding test conditions are shown in Table 4 (Examples) and Table 5 (Comparative Examples) below. The quality of the welded portion obtained by this welding test is shown in Table 6 (Examples) and Table 7 (Comparative Examples) below.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3] (*) CO ₂ , B ₂ O ₃ , Fe-Si, Fe-Mn, etc.

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

However, in Tables 4 and 5, the groove shape column is Y-shaped and indicates the groove angle and the length of the root portion. In Tables 6 and 7, ⊚ indicates extremely stable, ∘ indicates stable, Δ indicates slightly stable, and x indicates unstable.

In Table 5, Comparative Example 1 has a temporary mounting height of 7
When the groove angle is too high, the comparative example 2 has a large groove angle of 85 °, the comparative example 3 has a temporary attachment length of 15 mm, which is too short, and the comparative example 4 has a small groove angle of 40 °. In Example 5, when the tacking height is as low as 2.8 mm, in Comparative example 6, the second electrode diameter is as small as 4.0 mm, in Comparative example 7, the welding speed is too fast and the ratio of L1 / L2 is 0. 9 is large, Comparative Example 8 has a too high temporary mounting height of 7 mm, and Comparative Example 9 has a small diameter of the second electrode and the third electrode.

As shown in Tables 6 and 7, by satisfying the conditions defined in claim 1 of the present application, any one of the shape of the front bead, the penetration depth by the electrodes after the second electrode and the stability of the back bead is obtained. Was excellent, and neither cracking nor arc stop occurred. On the other hand, in the case of the comparative example deviating from claim 1 of the present application, any of the surface bead shape, the penetration depth by the electrodes after the second electrode, and the stability of the back bead were inferior. Further, in Comparative Examples 3 and 5, cracking occurred.

[0041]

As described above, according to the present invention,
Since the electrode diameter, groove shape, and the length and height of the temporary bead were properly set, 100 to 200c in single-sided submerged arc welding using three or more electrodes
High-speed welding of m / min can be performed with a weld bead having a stability equal to or higher than that of the conventional one and with a sound penetration, and inconveniences such as cracking and arc stop can be avoided.

[Brief description of drawings]

FIG. 1 is a graph illustrating the requirements for a temporary mounting height defined by the present invention, with the horizontal axis representing the welding speed and the vertical axis representing the height of a temporary bead.

FIG. 2 is a diagram illustrating requirements for a groove shape.

FIG. 3 is a diagram illustrating requirements for a temporary bead.

FIG. 4 is a diagram for explaining requirements for temporary beading similarly.

FIG. 5 is a schematic view showing a bead shape of a welded portion.

FIG. 6 is a diagram illustrating a problem due to the shape of a temporary bead.

FIG. 7 is a schematic diagram illustrating undercutting and slag winding.

Claims (2)

[Claims] 1. Using at least three electrodes, the wire diameter of the leading first electrode is 4.0 to 4.8 mm, and the wire diameter of the following second electrode is 4.8 to 6.4 mm, the third.
Single-sided submerged arc for Y-shaped groove joint welding with a wire diameter of 6.4 to 8.0 mm after the electrode and a groove angle of 45 ° to 80 ° and a root portion of 3 to 7 mm In the welding method, the temporary bead length is 20 mm or more, and the bead height h (mm) is 3.0 ≦ h ≦ 3.
00 / V + 5 (where V is the welding speed (cm / min)), after temporarily welding the inside of the groove, the inside of the groove is 100
A single-sided submerged arc welding method, which comprises welding at a speed of 200 to 200 (cm / min). 2. The tack welding is performed under a condition that a ratio L2 / L1 of the welding length Ll of the tack welding to the length L2 of the parallel portion of the tack beat is 0.8 or less. One-sided submerged arc welding method.