JP2008168319A - Butt welded joint of steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a butt welded joint of medium and heavy gage steel plates capable of achieving highly efficient welding execution utilizing the characteristic of the laser beam welding, in the butt welded joint of ends of the medium and heavy gage steel plates, and ensuring high quality and high performance of the welded joint. <P>SOLUTION: In the butt welded joint of the ends 1a of steel plates 1 having the thickness of ≥10 mm and ≤30 mm, a bevel shape is made an X bevel. The bevel root face part 2 of a center portion of the plate thickness is welded by the deep penetration welding in one pass, and remaining bevel portions 3, 4 on both sides in the direction of the plate thickness are subjected to the finish welding in one pass. The butt welded joint of the medium and heavy gage steel plates has a sectional shape of three-layered structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a butt-welded joint between medium-thick steel plates.

  Generally, arc welding such as gas shielded arc welding or submerged arc welding is used for butt welding of medium-thickness steel plates having a plate thickness of about 20 mm. Recently, the application of high energy density beam welding such as electron beam and laser beam is also spreading. Such beam welding has an advantage that the welding speed is higher than that of arc welding and thermal damage to the base material is small.

In particular, laser welding can be performed in the atmosphere, and the development of large-capacity oscillators in recent years has combined with the expansion of the range of applications from thin plates as small as several millimeters to thick plates exceeding 10 mm. ing.
On the other hand, the following proposals have been made as conventional techniques related to laser welding of thick plates.

In Patent Document 1, in butt welding of a metal plate, a groove shape is an I-shaped groove having a width of 2 to 4 mm, and a laser beam is irradiated while oscillating in the width direction of the groove gap, and the gap is filled. Therefore, a narrow groove laser welding method for supplying filler metal and performing welding has been proposed.
In Patent Document 2, while supplying a filler wire to a narrowly set I-shaped groove, a laser beam is passed through the narrow groove width space, and a weld layer is formed by irradiating the tip of the filler wire. A narrow groove laser welding method has been proposed in which a welding layer is sequentially formed from the back to the front by repeating this to perform lamination welding.

In Patent Document 3, the groove shape when butt-welding thick plates is a Y-shaped narrow groove, and the I-type root face portion is welded in one pass, and then the second layer or more is the focus of the laser beam. There has been proposed a laser welding method in which a welding material is supplied and multilayer welding is performed on a V-shaped groove portion while irradiating a beam with a position separated from the root face portion by 1/20 or more of the focal length.
In Patent Document 4, in butt welding of a Y-type narrow groove having a root face and a groove, when welding the I-type root face part, a laser is irradiated from the groove side to melt the root face part. A butt laser welding method has been proposed in which an amount of filler material set in accordance with the groove angle is supplied to the melted portion.
JP-A-62-220293 JP-A-9-201687 JP-A-7-323386 Japanese Patent Laid-Open No. 2002-273587

  However, in the methods of Patent Documents 1 and 2, the groove shape of the butt weld is an I-shaped groove with a narrow gap, and a filler wire is inserted into the narrow gap and a laser beam is irradiated to the filler wire. However, considering the case where a structure having a welding length of several meters is welded, there remains a problem in practicality such as the need to strictly manage the groove gap dimension.

Further, in the method of Patent Document 3, the energy density of the beam is reduced by defocusing in order to suppress the occurrence of welding defects, and the high energy density, which is the greatest feature of laser welding, is sacrificed.
Furthermore, in the method of Patent Document 4, it is necessary to supply a solution corresponding to the groove angle in order to form a stable back wave, but in an actual structure, the groove angle is set to the entire length of the weld line. It is difficult to keep it constant over time, and problems remain in practicality.

As described above, the technologies proposed in the above patent documents aim to improve the construction efficiency by laser welding, but are practical in terms of the dimensional accuracy of the groove gap, the stable supply of filler wire, and the target accuracy of beam irradiation. On the contrary, it seems to be an inefficient method.
The present invention was made paying attention to such points, and in the butt-welded joint between the ends of the steel plates of medium thickness plates, the features possessed by laser welding with the same construction management as the conventional welding construction as much as possible. The objective is to propose a butt-welded joint for medium-thickness steel plates that can realize high-efficiency welding work that is utilized, and can also improve the quality and performance of the welded joint.

  In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention is a butt weld joint between end portions of steel plates having a plate thickness of 10 mm or more and 30 mm or less, and the groove shape is X groove. The groove root face part at the center of the plate thickness was welded in one pass by deep penetration welding, and the remaining groove portions on both sides in the plate thickness direction were then finished and welded in one pass, respectively. It has the laminated structure of.

  Here, the thickness of the steel sheet is defined as 10 mm or more and 30 mm or less as follows. If the plate thickness is less than 10 mm, it is possible to perform welding only by laser welding. Therefore, it is considered that there is no problem even if the present invention is not applied, so the lower limit is set to 10 mm. When the plate thickness exceeds 30 mm, the dimension of the groove root face portion 2 becomes long, and there is a possibility that sufficient deep penetration welding cannot be ensured. Therefore, the upper limit value is set to 30 mm.

Next, the invention described in claim 2 is characterized in that, in the configuration described in claim 1, deep penetration welding of the groove root face portion is performed at least by laser welding.
Next, the invention described in claim 3 is characterized in that arc welding is applied to the finish welding of the groove portions on both sides in the plate thickness direction with respect to the configuration described in claim 1 or claim 2. It is.

According to the present invention, a butt weld joint between the ends of a steel plate made of a medium thickness plate is used for deep penetration welding in which the groove root face portion at the center portion of the plate thickness is specified in one pass while the plate thickness is specified. By making each groove portion located on both sides in the thickness direction a welded joint having a three-layer structure in which one-pass finish welding is performed, overall welding heat input can be reduced. As a result, deterioration of HAZ toughness and HAZ softening are suppressed, and high performance of the welded joint can be achieved. Moreover, since thermal distortion is small and the amount of welding material used can be reduced, the cost can be reduced. That is, the welding process is performed three times, the overall welding heat input can be reduced, and the performance of the welded joint is improved.
At this time, when Claim 2 is applied, deep root welding of the groove root face portion is possible, the welding speed of the groove root face portion is excellent, and the efficiency of the welding work is improved.

Next, embodiments of the present invention will be described with reference to the drawings.
(Constitution)
FIG. 1 is a schematic cross-sectional view of a butt-welded joint between steel plates in the present embodiment.
First, the both ends 1a of the steel plate 1 are grooved into X grooves. Here, reference numeral 2 is a groove root face part formed in the central part in the plate thickness direction, and reference numerals 3 and 4 indicate groove portions on both sides (back side and front side) in the plate thickness direction, respectively. Yes.

  In this butt welding, first, the groove root face portion 2 at the central portion of the plate thickness is main-welded by one-pass deep penetration welding. Reference numeral 5 denotes the deep penetration weld. Subsequently, the groove portion 3 on the back surface side and the groove portion 4 on the front surface side are finish welded. At this time, the penetration portions of the respective back surface finish welds 6 and the surface finish welds 7 are not overlapped. However, a part of the deep penetration weld 5, the back surface finish weld 6 and the surface finish weld 7 each overlap the penetration.

  Here, as the deep penetration welding of the groove root face portion 2, application of laser welding, electron beam welding, plasma welding or the like can be considered. Of these, laser welding is preferred. That is, electron beam welding can be deepest and deeply welded, but has a drawback that it cannot be used in the atmosphere. Plasma welding is inferior in welding speed compared to other welding methods. In view of the above, laser welding is suitable because laser welding that can be performed in the atmosphere and has recently been developed with high output and excellent beam quality.

  In addition, for example, general arc welding such as gas shield arc welding or submerged arc welding can be applied to finish welding of the groove portions 3 and 4 on the back surface side and the front surface side. In the present embodiment, the three-layer structure in which the penetration portions of the back surface finish weld portion 6 and the surface finish weld portion 7 are not overlapped with each other, the cross-sectional areas of the groove portions 3 and 4 can be reduced. For this reason, welding can be performed by one-pass gas shield arc welding or submerged arc welding, and there is no problem with respect to the soundness of the welded joint.

(Function and effect)
Next, details of the present embodiment will be described.
In general, for butt welding of medium-thickness steel plates with a plate thickness of about 20 mm, a multi-layer welded joint by gas shield arc welding with relatively low welding heat input, as in the above-mentioned conventional example, increases welding heat input There are two-sided single-layer welded joints by submerged arc welding that achieve high efficiency, and one-pass large heat input welded joints by electrogas arc welding. When such high heat input welding is applied, deterioration of HAZ toughness and HAZ softening become problems. On the other hand, approaches from the material side such as optimization of the composition of steel materials and approaches from the welding work side such as application of high energy density beam welding have been studied. There are overwhelmingly many technologies.
Therefore, the present inventors have studied from the viewpoint of the welding construction in consideration of practicality while effectively utilizing the features of laser welding in order to realize high-efficiency welding construction and high performance of the welded joint at the same time. This invention was made by trying.

  In the present embodiment, as shown in FIG. 1, in order to ease the dimensional accuracy of the groove gap, the stable supply of filler wire, and the target accuracy of beam irradiation, which are the impediments to practicality that have been problems in conventional laser welding, as much as possible. In addition, the need for controlling the groove gap is eliminated by setting the groove shape to an X groove having a root face portion at the center of the plate thickness. Further, when welding the groove root face portion 2 at the center of the plate thickness by one-pass deep penetration welding, it is not necessary to add a filler wire for filling the lack of weld metal, and the aim of beam irradiation There is no need to control the filler wire. At this time, in order to suppress welding defects such as porosity and blow, it is desirable that the deep penetration welding of the root face portion be through-welded. Furthermore, since the groove portion 3 on the back surface side is finish-welded by ordinary arc welding in the next step, the unevenness state of the back bead of the deep penetration weld portion 5 of the route fail portion is not necessarily important. Don't be.

That is, in this embodiment, deep root welding of the groove root face portion 2 is performed by butt welding of thick plates by high energy beam welding typified by laser welding, and thereafter the cross-sectional areas on the back surface side and the front surface side are small. By laminating the groove portions 3 and 4 by arc welding, the laminated structure of the weld joint becomes a three-layer structure, but overall weld heat input is reduced and the performance of the weld joint is improved.
Here, the plate thickness is limited to 10 mm or more and 30 mm or less because if the plate thickness is less than 10 mm, welding is possible only by laser welding, so it seems that there is no problem even if the present invention is not applied. If the plate thickness exceeds 30 mm, the dimension of the groove root face portion 2 becomes long, and sufficient deep penetration welding may not be ensured.

  Moreover, in the said embodiment, although the case where the groove root face part 2 performs deep penetration welding only by laser welding is illustrated, it is not limited to this. Laser hybrid welding combining laser welding and arc welding may be used. In laser hybrid welding, although the condition factors to be controlled increase, the aim accuracy with respect to the weld line can be relaxed compared to the case of laser welding alone, so that the groove root face portion 2 is surely deep-welded. Is effective.

Next, examples of the present invention will be described.
For butt welding of steel plates having thicknesses of 12 mm, 20 mm, 25 mm, and 28 mm, a welded joint (invention example) according to the present invention and a conventional welded joint (comparative example) were compared. Note that the test steel sheet is a low alloy steel having a tensile strength of 490 MPa manufactured by the TMCP process.
Table 1 shows welding conditions and results of inventive examples according to the present invention and comparative examples according to the conventional method.

  In invention examples 1 to 4, with the groove shape as the X groove, the groove root face portion is first subjected to deep penetration welding by laser welding, and then the groove portion on the back side and the front side is subjected to MAG welding or submerging. This is a case where finish welding is performed by one-pass welding by arc welding. For laser welding, a fiber laser having higher energy density and superior beam quality than a conventional laser was used.

Inventive example 5 is the same as in inventive examples 1 to 4, in which the groove shape is X groove and the groove root face part is deep penetration welded by plasma welding instead of laser welding. In the case of plasma welding, deep penetration can be obtained, but the welding speed must be very slow, 0.3 m / min, compared to laser welding, which is inferior to laser welding.
In Comparative Example 6, the groove shape is an I groove, the gap is set to 1 mm, and finishing is performed by one-pass deep penetration welding by laser welding alone.
In Comparative Example 7, the groove shape is a Y groove, the I-type root face portion is subjected to two-layer welding by laser welding, and then the groove portion on the surface side is finished by submerged arc welding. .

  In Invention Examples 1 to 5, it is easy to completely match the groove root face portion at the central portion of the plate thickness. As a result, it is not necessary to add a filler wire, and high precision management of the target position of beam irradiation, There are few factors that hinder welding workability. In addition, since the groove portions corresponding to the upper and lower parts of the deep penetration welded portion are subjected to finish welding by general-purpose arc welding, it is not always necessary to form a back wave in the welding of the groove root face portion. Is easy. Furthermore, welding defects such as porosity, which are a problem in beam welding, are reduced in the frequency of occurrence and good joint properties by making the first stage groove root face part through welding.

On the other hand, in Comparative Example 6, since the thick plate is finished by one pass of laser welding, a slight shift in the target position of the beam irradiation affects the final joint properties, so it is necessary to strictly manage the groove gap dimension. is there. Furthermore, in deep penetration welding with a narrow groove, a recess is likely to occur on the back surface, and poor penetration is likely to occur.
In Comparative Example 7, the Y groove is used, and the welding workability is the same as that of the present invention example. However, since 2-pass laser welding becomes non-through welding, welding defects such as porosity are likely to occur. .

It is a section schematic diagram showing the structure of the butt-welding joint of the steel plate concerning the embodiment based on the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 1a End part 2 Groove root face part 3 Groove part on the back side 4 Groove part on the surface side 5 Deep penetration weld part of the groove root face part 6 Finish weld part 7 on the back side groove part Surface side Finish weld of groove

Claims (3)

A butt-welded joint between the ends of a steel plate having a plate thickness of 10 mm to 30 mm,
The groove shape is the X groove, and the groove root face at the center of the plate thickness is welded in one pass by deep penetration welding, and then the remaining groove portions on both sides in the plate thickness direction are each finished in one pass. A butt-welded joint for steel sheets, characterized in that the cross-sectional shape has a three-layer laminated structure.   The butt weld joint for steel sheets according to claim 1, wherein the deep penetration welding of the groove root face portion is performed by at least laser welding.   The butt-welded joint for steel sheets according to claim 1 or 2, wherein arc welding is applied to finish welding of the groove portions on both sides in the plate thickness direction.

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