JPH09164496A - Plate butt welding joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of stress at a welding part and to improve the fatigue strength without executing finish-treating of a groove from the back side by composing the groove of a bent part so as to be formed with bending from the front face side toward the back face side at each butt end of the plates. SOLUTION: A plate 4 is formed thicker than a plate 2. A groove 12 is formed at the butt end of the plate 2 and the plate 4. The groove 12 is, at the butt end of the plate 2 and the plate 4, composed of bent parts 2a, 4a of respectively forming from the front face toward the back face. The groove angle of the groove 12 is 45 deg.. The groove 12 is welded and a butt welding joint 1 is formed. In this welding joint 1, because the throat depth H from a root part 16 is made largely and at only a welding part, a local appearance thickness is increased, the generating stress is reduced, and the fatigue strength of a stop end 20 and the root part 16 is improved. Further, the finish treatment of the back face side of the groove 12 is not required especially to execute, and the function effect can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a butt-welded joint for plates formed by welding grooves formed at the butt ends of the plates.

[0002]

2. Description of the Related Art Three typical examples of conventional butt-welded joints for plates will be described with reference to FIGS. Referring to FIG. 5 showing the first typical example, 50 is one plate and 52 is the other plate, which are thicker than the plate 50. Board 50 and board 5
A groove 54 having a groove angle θ is formed at the abutting end with the groove 2. The groove 54 is formed from the front surface (upper part of FIG. 5) to the back surface (lower part of FIG. 5) at the abutting end of the plates 50 and 52.
It is composed of an inclined surface formed so as to become lower toward. A butt weld joint is formed by welding the groove 54. 56 is a weld metal (bead), 58 is a root portion, 59 is a back bead, and 70 is a toe. The backsides of plates 50 and 52 are positioned substantially coplanar.

Next, the second of the conventional butt-welded joints for plates
A typical example will be described with reference to FIG. In FIG. 6, the same parts as those in FIG. 5 are designated by the same reference numerals. The butt welded joint shown in FIG. 6 is formed by further welding the root portion 58 from the back surface side of the butt welded joint shown in FIG. 5 and then removing the back bead 59. As a result, the root portion 58 forms a flat surface that is substantially the same as the back surfaces of the plates 50 and 52.

Next, the third conventional butt-welded joint for plates
A typical example of will be described with reference to FIG. In FIG. 7, the same parts as those in FIGS. 5 and 6 are designated by the same reference numerals.
In the butt welded joint shown in FIG. 7, a groove 54 of the plate 50 and the plate 52 is formed with a root gap g provided, and a backing metal 60 is attached to the back surface of the groove 54 by temporary welding to form the groove 54. Are formed by welding.

[0005]

The butt-welded joint of plates described above is used, for example, in an arm of a hydraulic excavator (not shown). This arm forms a closed box-shaped structure and is formed by welding an upper plate, both side plates and a lower plate. Of these, the upper plate and the lower plate each have a plate thickness defined according to strength, and the cut plates are joined together by butt welding as described above. Therefore, the above-mentioned butt-welded joint portion is subjected to a severe high-cycle load, and as shown in FIGS. 5 to 7, from the toe 70 of the welded portion, inside the thinner plate 50 having relatively low strength. A crack 72, which is a fatigue fracture, occurs in the weld metal, or as shown in FIGS. 8 to 10, a crack 7 is formed in the weld metal 56 from the root portion 58.
4 may occur.

Fatigue fracture of the toe 70 on the surface side of the plates 50 and 52 is often due to stress concentration due to the notch of the toe 70, and therefore, to improve its fatigue strength. It can be dealt with by performing finishing processing such as grinding, finishing of the grinder and improvement of the welding construction method. On the other hand, the fatigue fracture of the root portion 58 is mostly due to stress concentration due to the notches in the root portion 58 and internal defects due to poor welding, and this is also caused by finishing treatment such as grinder finishing and improvement of welding construction method. It can be handled by doing. However, the root portion 58 is on the back surface side of the plates 50 and 52, and when it is inside the box-shaped structure having the closed shape, it becomes impossible or extremely difficult to deal with by the finishing treatment, and its fatigue The strength cannot be improved.

The present invention has been made on the basis of the above facts, and its main purpose is to reduce the stress generated in the welded portion and improve the fatigue strength without performing the finishing treatment from the back side of the groove. To provide an improved butt weld joint for plates.

Another object of the present invention is to provide an improved butt-welded joint for plates which can reduce the stress generated at the welded portion and improve the fatigue strength.

[0009]

According to the present invention, in a butt-welded joint of plates formed by welding grooves formed at the butt ends of the plates, the grooves are A butt-welded joint for plates, characterized in that each of the butt ends comprises a bent portion formed from the front surface side to the back surface side.

In the butt-welded joint of plates according to the present invention, the groove is composed of bent portions formed at the butt ends of the plates from the front surface side to the back surface side. With this configuration, the throat thickness from the root portion increases, and the apparent plate thickness locally increases only in the welded portion, so that the generated stress decreases and the fatigue strength of the toe portion and the root portion improves. According to this structure, the above-described effects can be achieved without performing a finishing process from the back side of the groove. Therefore, the present invention can be preferably used when the root part is inside the box-shaped structure having a closed shape.

According to the present invention, in addition to the above structure, a cut portion that is substantially parallel to each back surface of the plate is formed at a tip portion on the back surface side of each bent portion. A butt weld joint is provided.

According to this structure, since the relatively sharp uneven portion existing on the back surface side of the welded portion is removed to form the flat cut portion, the degree of stress concentration is reduced and the fatigue strength is further improved. To do. Moreover, since the protruding height of the welded portion toward the back surface is reduced, the internal space of the applied structure can be widened. INDUSTRIAL APPLICABILITY The present invention is suitable for use as a butt-welded joint for plates that can be subjected to finishing treatment from the back surface side of a welded portion, and as a butt-welded joint for plates that cannot be subjected to finishing treatment from the back surface after welding. You can

According to the present invention, in addition to the above structure, there is provided a butt-welded joint for plates, in which a backing plate is welded to the cut portion.

According to this structure, it is possible to prevent burn-through from the root portion during welding work. INDUSTRIAL APPLICABILITY The present invention can be suitably used as a butt-welded joint for plates, which cannot be finished after the welding from the back side of the welded portion.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Embodiments of a butt welded joint of plates improved according to the present invention will be described in detail. First, an embodiment of a butt-welded joint for plates according to the present invention will be described with reference to FIGS. 1 and 4. FIG. 4 shows a part of a closed box structure, an upper plate consisting of plates 2 and 4, side plates 6 and 8 and a lower plate 1.
0. The plates 2 and 4 constituting the upper plate are joined together by the butt welding joint 1 of the plates according to the present invention, and the upper plate and the lower plate 10 are welded by the side plates 6 and 8.
Are linked.

Referring to FIG. 1, the plate 4 is thicker than the plate 2. A groove 12 is provided at the butt end of the plate 2 and the plate 4.
Are formed. The groove 12 is composed of bent portions 2a and 4a formed at the abutting ends of the plate 2 and the plate 4 so as to extend from the front surface (upper part in FIG. 1) to the back surface (lower part in FIG. 1). The groove angle of the groove 12 is preferably 45 °. The butt welded joint 1 is formed by welding the groove 12. In FIG. 1, 14 indicates a weld metal (bead), 16 indicates a root portion, and 18 indicates a toe. The toe 20 is subjected to the usual finishing treatment such as grinder finishing and makeup welding.

According to this butt welded joint 1, as shown in FIGS.
As can be easily understood by comparing with the conventional butt-welded joint shown in FIG. 7, the throat thickness H from the root portion 16 becomes large and the apparent sheet thickness locally increases only in the welded portion, The generated stress is reduced, and the fatigue strength of the toe 20 and the root portion 16 is improved. Butt welded joint 1
According to the above, the action and effect can be achieved without particularly performing the finishing treatment from the rear surface side of the groove 12. Therefore, in the butt-welded joint 1, when the root portion 16 is inside the box-shaped structure having a closed shape as shown in FIG.
For example, it can be suitably used for booms and arms of hydraulic excavators.

FIG. 2 shows another embodiment of the butt-welding joint for plates according to the present invention, and the same portions as those in FIG. 1 are designated by the same reference numerals. In the butt-welded joint shown by reference numeral 20 as a whole, cut portions 22 and 24, which are substantially parallel to the back surfaces of the plates 2 and 4, are formed at the tip portions on the back surfaces of the bent portions 2a and 4a, respectively. There is. The cut portions 22 and 24 have a height h from the back surface of each of the plates 2 and 4,
This height h is set appropriately. The cut portions 22 and 24 can be formed in advance by processing before welding, or can be formed by processing after welding.

According to this butt welded joint 20, a relatively sharp uneven portion (each plate 2) existing on the back surface side of the welded portion.
Since the uneven portion formed by the abutting end portions of 4 and 4 is removed and the flat cut portions 22 and 24 are formed,
The degree of stress concentration is reduced, and the fatigue strength is further improved. Moreover, since the protruding height of the welded portion toward the back surface is reduced, the internal space of the applied structure can be widened. INDUSTRIAL APPLICABILITY The present invention is suitable for use as a butt-welded joint for plates that can be subjected to finishing treatment from the back surface side of a welded portion, and as a butt-welded joint for plates that cannot be subjected to finishing treatment from the back surface after welding. You can

FIG. 3 shows still another embodiment of the butt-welded joint for plates according to the present invention, and the same parts as those in FIGS. 1 and 2 are designated by the same reference numerals. In the butt-welded joint indicated by reference numeral 30 in its entirety, the cut portions 22 and 2
A backing metal 32 is welded to the metal plate 4. This backing gold 3
The 2 is pre-welded before the welding between the plates 2 and 4 takes place.

According to this butt-welded joint 30, it is possible to prevent burn-through from the root portion 16 during welding work. INDUSTRIAL APPLICABILITY The present invention can be suitably used as a butt-welded joint for plates that cannot be finished from the back side of the welded portion.

The present invention has been described above in detail based on the embodiments. However, the present invention is not limited to the above embodiments, and various changes or modifications can be made within the scope of the present invention. Is. In the above-mentioned embodiment, the plate 4 is formed thicker than the plate 2, but the present invention can also be realized as a butt welding joint between plates having the same thickness.

[0023]

As described above, according to the present invention described based on the embodiment, the stress generated in the welded portion is reduced and the fatigue strength is improved without performing the finishing treatment from the back side of the groove. can do. Therefore, although not limited thereto, it can be preferably used when the root part is inside the box-shaped structure having a closed shape. Further, according to another aspect of the present invention, the same effect is achieved by being used as a butt-welded joint for a plate capable of finishing treatment from the back surface side of the welded portion.

[Brief description of the drawings]

1 shows an embodiment of a butt-welded joint for plates according to the present invention, and is a cross-sectional view taken along the line AA of FIG.

FIG. 2 is a sectional view showing another embodiment of a butt-welded joint for plates according to the present invention.

FIG. 3 is a sectional view showing still another embodiment of a butt-welded joint for plates according to the present invention.

FIG. 4 is a perspective view showing a part of a box-shaped structure to which a butt-welded joint of plates according to the present invention is applied.

FIG. 5 is a cross-sectional view showing a first typical example of a conventional butt-welded joint for plates together with one mode of crack generation.

FIG. 6 is a cross-sectional view showing a second typical example of a conventional butt-welded joint for plates in a form similar to that of FIG.

7 is a cross-sectional view showing a third typical example of a conventional butt-welded joint for plates in a form similar to FIG.

8 is a cross-sectional view showing the butt-welded joint of the plate shown in FIG. 5 together with another form of crack generation.

9 is a cross-sectional view showing the butt-welded joint of the plate shown in FIG. 6 together with another form of crack generation.

FIG. 10 is a cross-sectional view showing the butt-welded joint of the plate shown in FIG. 7 together with another form of crack generation.

[Explanation of symbols]

 1, 20 and 30 Butt welded joints 2 and 4 Plates 2a and 4a Bent portion 12 Groove 14 Weld metal 16 Root portion 22 and 24 Cut portion 32 Backing metal H Nod thickness

Claims (3)

[Claims] 1. A butt-welding joint for plates, in which a groove formed at the butt ends of the plates is welded to each other, wherein the groove is provided on the butt end of each of the plates from the surface side. A butt-welded joint for plates, characterized in that it is composed of a bent portion formed to face the back surface side. 2. A butt-welded joint for plates according to claim 1, wherein a cut portion that is substantially parallel to the back surface of each of the plates is formed at the back end of each of the bent portions. . 3. The butt-welded joint for plates according to claim 2, wherein a backing metal is welded to the cut portion.