JPH08332567A - One side welding method without using backing - Google Patents

Abstract

PURPOSE: To obtain one side welding method without using a backing in which burn through of melted bead is not generated, welding of high welding current is made possible and welding efficiency is improved even in the case of a welding joint of poor joint precision such as reduced root face and generation of root gap. CONSTITUTION: A welding joint, in which one side inclined groove of single bevel groove and single J groove is formed, is constituted by one member W1' having the inclined groove face with <=3mm thickness root face and other member W2, arc welding is executed from front side without using a backing so that the undeposited part of welding joint is <=2mm from the groove root reference point. Further, as for the member W1', the member, in which a back bead B is formed near the groove root reference point at rear face of member along the groove longitudinal direction by bead on plate welding beforehand, is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-side welding method which does not use a backing material, and relates to a welded joint having a root face having a thickness of 3 mm or less, such as a R-shape or a J-shape, in which one inclined groove is formed. The present invention relates to a one-side welding method in which arc welding is performed from the front side without using a backing material so that the non-welded portion of the welded joint is 2 mm or less from the groove root base point.

[0002]

2. Description of the Related Art In manufacturing a box-shaped structure such as a box column for steel frame construction, after assembling members into a box shape, welding is performed from the inside of the box-shaped members. Since it is often difficult to attach a backing material (backing metal), one-sided welding in which a welded joint is welded only from the front side is often forced.

When welding is performed from only one side without using the backing material in this way, in order to secure the required joint strength, as shown in FIG.
As shown in FIG. 6, one member W1 having an inclined groove surface having a root face Rf having a thickness of 2 to 3 mm, and the other member W2 having no groove processing, are J-shaped or shown in FIG. A welded joint is formed in which one inclined groove is formed such that one side thereof is an inclined groove surface, and the non-welded portion L of the welded joint is 2 mm or less when measured from the groove root base point R. A one-side welding method is used in which the above-mentioned groove is carbon dioxide arc-welded from the front side without using a backing material.

[0004]

However, since some welded joints have poor joint accuracy due to groove processing errors and joint assembly errors, the conventional method described above uses the longitudinal direction of the groove during welding of the first layer. At the location where the root face becomes smaller in the (welding line direction) or a root gap (root gap) occurs, the groove root portion of the member with the inclined groove surface largely burns down, and it takes a lot of trouble to repair it. The required melting bead burnout often occurred.
For this reason, the first layer is welded at a low welding current in consideration of the occurrence of burn-through, which causes a problem of poor welding work efficiency.

The present invention has been made in order to solve the above-mentioned problems, and relates to a welded joint in which one sloping groove such as a rectangular groove is formed, in which the non-welded portion of the welded joint has a groove. When performing arc welding from the front side without using the backing material so that the distance is 2 mm or less from the root base point, the root face becomes smaller in the longitudinal direction of the groove, or a root gap occurs. In addition, it is possible to perform welding with a higher welding current than before without causing the melted bead to burn through, thereby improving the welding work efficiency, and to provide a one-sided welding method that does not use a backing material. With the goal.

[0006]

In order to achieve the above-mentioned object, the one-sided welding method according to the present invention which does not use a backing material is one member having an inclined groove face having a root face with a thickness of 3 mm or less and the other member. The above-mentioned member constitutes a welded joint in which one-angled beveled groove such as a R-shaped or J-shaped groove is formed, and the backing material is applied so that the non-welded portion of the welded joint is 2 mm or less from the groove root base point. In the one-sided welding method of performing arc welding of the one sloped groove from the front side without using, as one member having the sloped groove surface, the melt bead is prevented from melting through near the groove root base point on the back surface of the member. In order to do so, a member having a back bead formed in advance along the longitudinal direction of the groove by bead-on-plate welding is used.

[0007]

FIG. 5 is a view showing the structure of a welded joint according to the conventional one-sided welding method, and FIG. 1 is a view showing the structure of a welded joint according to the method of the present invention. In FIG. 5, during the first layer welding in one-sided welding, the part where the temperature rises most on the back side of the joint member is
It is a portion A in the vicinity of the groove root reference point R on the back surface of the member W1 having the inclined groove surface. If there is a portion where the root face Rf is reduced or a root gap is generated due to a groove processing error or a joint assembly error,
A burn-through occurs at the portion A at that portion.

This is because the member W1 having the inclined groove surface and the other member W2 which has not been groove processed have different member heat capacities in the groove root portion, and the heat capacity of the member W1 is larger than that of the member W2. Because of the small size, the member W1 suffers burn-through before melting the groove root portion of the member W2 that has not been groove processed.

On the other hand, in the method according to the present invention,
As shown in FIG. 1, a member having a back bead B formed along the longitudinal direction of the groove by bead-on-plate welding in the vicinity of the groove root base point R on the back surface of the member W1 ′ having an inclined groove surface is used. Therefore, the heat capacity at the groove root portion increases. As a result, even in a welded joint with poor joint accuracy in which the root face Rf becomes small in the longitudinal direction of the groove or a root gap of about 0.5 mm occurs, the joint unwelded portion is opened without causing burn-through. Penetration of the groove root portion can be ensured so as to be 2 mm or less from the root route base point R, and welding can be performed with a higher welding current than in the past. In addition,
Distance d between the groove route base point R and the back bead B shown in FIG.
If it exceeds 4 mm, the effect of preventing burn-through will not be exhibited reliably, so it is preferable to set it to 0-4 mm.

The back bead, which is applied to prevent the molten bead from melting through, is carbon dioxide arc welding, mag arc welding,
It may be formed by consumable electrode type arc welding, which is suitable for excess formation such as covered arc welding. Also, by using filler wire (filler material) for TIG arc welding, plasma arc welding, laser welding, etc. The base material may be formed by non-consumable electrode welding with a filler wire that is extremely resistant to deformation of the base material by heat. In order not to reduce the joint accuracy, it is preferable to form the back bead on the member before processing the inclined groove surface by gas cutting or the like.

[0011]

Embodiments of the present invention will be described below.
First, while forming the square corner joint shown in FIG. 1, for comparison, the square corner joint shown in FIG. 5 without the back bead B is formed, and the first layer formed by carbon dioxide gas arc welding from the groove surface side is constructed. Welding was performed, and the burn-through limit welding currents at various welding speeds were compared. Root face Rf is 1
mm constant, root gap is zero, and 0.5m
There are two types, m. The plate thickness t1 is 12 mm, and the plate thickness t2 is 1.
6 mm, and the groove angle θ is 45 °. The back bead B is formed by carbon dioxide arc welding using an automatic welding device,
The welding conditions are welding current: 170 A, welding voltage: 22.
V, welding speed: 34 cm / min. The distance d between the groove root base point R and the back bead B was about 2 mm. Each member is a mild steel material.

The results are shown in FIGS. 2 and 3. Figure 2 shows the burn-through limit welding current when the root gap is zero,
FIG. 3 shows the burn-through limit welding current when the root gap is 0.5 mm. In both figures, ○ indicates the burn-through limit welding current by the conventional method without back bead B, □ indicates the burn-through limiting welding current by the method of the present invention, ● indicates the burn-through generated welding current by the conventional method, ▲
The black squares ∘ indicate the burn-through generation welding current in the method of the present invention. According to the method of the present invention, the burn-through limit welding current value is significantly higher than that of the conventional method, and in particular, as shown in FIG. 3, when there is a root gap, the difference from the conventional method is remarkable. Become. Further, according to the method of the present invention, 3
It can be seen that at a standard welding speed of 5 to 45 cm / min, the difference in the burn-through limit welding current between when the root gap is zero and when the root gap is present is smaller than that of the conventional method. This confirms that when the welding is carried out at a constant welding current and welding speed, the penetration of the groove root portion can be stably ensured even if the joint accuracy changes.

For a joint in which the root gap fluctuates in the range of 0 to 0.5 mm, the joint non-welded portion has a groove root base point R.
In order to secure the penetration of the groove root portion so as to be 2 mm or less and to perform welding without causing burn-through, in the conventional method, as shown in FIG. 3, welding speed: 35 cm /
In the case of min, it is necessary to set the welding current to 210 A or less. When the first layer is welded at such a low welding current value, the remaining groove cross section becomes large, and the finish welding cannot be performed in the next second layer welding. On the contrary,
According to the method of the present invention, at a welding speed of 35 cm / min, a high welding current of 300 A can be used, so that the second layer of welding can be completed and sufficient penetration of the groove root portion can be ensured. .

Next, in the rectangular joint shown in FIG. 1, as shown in Table 1, the root face Rf is set to 0, 1, 2 m.
As for the welding conditions of the first layer when the second layer can be finish-welded, a welding current: 260A, a welding voltage: 30V, a welding speed: At 35 cm / min, welding of the first layer was performed by carbon dioxide gas arc welding from the groove surface side, and the presence or absence of burn-through was examined. The welding conditions and the distance d of the back bead B are, as described above, the welding current: 170 A, the welding voltage: 22 V, the welding speed: 34 cm / min, and the distance d: about 2 mm. For comparison, the first layer was welded by the conventional method without the back bead B. The results are shown in Table 1.

[0015]

[Table 1]

In Table 1, the mark X indicates that burn-through occurred, and the mark O indicates that burn-through did not occur. As can be seen from Table 1, according to the conventional method, the welding conditions cannot be applied to the square corner joint in which the root face Rf and the root gap fluctuate within the range shown in Table 1. It was confirmed that the welding conditions can be applied by the method according to (2) above without causing burn-through.

FIG. 4 is a drawing-substituting photograph showing the metallographic structure of the square-shaped square joint weld obtained by the method of the present invention. In this example, one-sided welding of the rectangular prismatic joint shown in FIG. 1 was performed. That is, one member W1 ′ having a plate thickness t1 of 12 mm
After the groove processing of the 45 ° inclined groove surface having the root face Rf having a thickness of 1 mm, the back bead B is provided on the back surface of the member at a position where the distance d from the groove root base point R is about 2 mm. By carbon dioxide arc welding with automatic welding equipment,
Welding current: 140A, welding voltage: 20V, welding speed: 2
It was formed along the longitudinal direction of the groove at 5 cm / min. Next, this member W1 'and the other member W2 having a plate thickness t2 of 16 mm were butted against each other to form a rectangular prismatic joint having a root gap of zero.

Then, welding current: 300 A, welding voltage:
Welding of the first layer by carbon dioxide gas arc welding using an automatic welding device at 32 V, welding speed: 45 cm / min, and then welding current: 370 A, welding voltage: 34
V and welding speed: 25 cm / min, and finish welding was similarly performed by carbon dioxide gas arc welding. It was possible to perform welding of the first layer at a higher welding current than before without causing the burn-through of the molten bead, which made it possible to shorten the welding time and improve the welding work efficiency.
In FIG. 4, almost complete penetration reaching the groove root base point is obtained, and so-called “burrs” are generated at the groove root base point portion.

Although the method according to the present invention has been described with reference to the example of the square-shaped square joint in each of the above-mentioned embodiments, the present invention is not limited to this, and in the butt joint, the square joint, the T-joint, the cross joint, etc. It can be applied to a welded joint in which a one-sided bevel groove such as J-shaped or J-shaped is formed.

[0020]

As described above, according to the one-side welding method according to the present invention which does not use a backing material, a member having an inclined groove surface and a member which is not grooved are used to form a grooved groove or the like. On the other hand, when performing arc welding from the front side without using a backing material, a weld joint with a sloped groove is formed, and the welded joint has a slope of 2 mm or less from the groove root base point when performing arc welding from the front side. As the member having the groove surface, a member having a back bead formed on the back surface of the member to increase the heat capacity in the groove root portion is used.
Even in welded joints where the root face becomes smaller in the longitudinal direction of the groove or a root gap occurs and the joint accuracy is poor, it is possible to perform welding at a higher welding current than before without causing melt-through of the molten bead. As a result, the welding work efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of a welded joint according to the method of the present invention.

FIG. 2 is a diagram relating to the method of the present invention, showing the burn-through limit welding current when the root gap is zero.

FIG. 3 is a diagram relating to the method of the present invention and is a diagram showing a burn-through limit welding current when the root gap is 0.5 mm.

FIG. 4 is a drawing-substituting photograph showing the metallographic structure of a square-shaped square joint weld obtained by the method of the present invention.

FIG. 5 is a diagram showing a configuration of a welded joint according to a conventional one-sided welding method.

FIG. 6 is an explanatory view of a one-side welding method of welding from the front side without using a backing material.

[Explanation of symbols]

W1, W1 ', W2 ... Member Rf ... Route face R
... Groove root base point L ... Joint non-welded part t1, t2 ... Plate thickness θ ... R-shaped groove angle B ... Back bead

Claims (1)

[Claims] 1. A member having an inclined groove surface having a root face with a thickness of 3 mm or less and the other member,
A welded joint in which a one-angled beveled groove such as a R-shaped or J-shaped groove is formed, and the welded joint's non-welded portion is 2 mm or less from the groove root base point, without using a backing material, from the front side. In the one-sided welding method for performing arc welding of the one-sided bevel groove, as one member having the beveled groove surface, bead-on in advance in order to prevent melt-through of the molten bead near the groove root base point on the back surface of the member. A one-sided welding method without using a backing material, which uses a member in which a back bead is formed along a groove longitudinal direction by plate welding.