JP2006281245A - Structure of backing metal for welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of backing metal for welding in which sudden rigidity change and notch sensitivity are mitigated by reducing stress concentration in a weld zone between a base metal and the backing metal, and in which generation of residual stress due to contraction/deformation in cooling the weld zone is relaxed by deforming the backing metal. <P>SOLUTION: This is the structure of the backing metal used in a welding method in which planar base metals 1, 1 to be welded are abutted on each other at their grooves 1a, 1a and in which the backing metal 5 is arranged that comes into contact with the base metals 1, 1. As the structure, on the base metal side of the backing metal 5, there is provided a space S that is larger than the width Z of a back bead to be formed on the rear side of the base metal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to the structure of a welding backing metal.

  One-sided butt welding is performed as so-called plate joint welding for joining steel plates together, particularly plate joint welding in a closed cross-section structure or a place where welding can be performed only from the front side. In this single-sided butt welding, it is indispensable that a weld bead is formed to the back side and completely welded. However, as described above, in a closed cross-section structure, it is difficult to visually confirm that a weld bead is formed on the back side of the weld.

  Therefore, as shown in FIG. 6, the end surface 1a is formed of the same member as the steel plates (welding base materials) 1 and 1 to be welded, and forms a V-shape at a predetermined angle of the steel plates 1 and 1, for example, 45 °. 1a (hereinafter referred to as "groove portion 1a, 1a") a backing metal 2 having a shallow groove 2a having a cross-sectional arc shape slightly wider than the width l between the lower ends (hereinafter referred to as "groove width l"). Are placed in contact with the back side surfaces 1b and 1b of the groove portions 1a and 1a, and the groove portions 2a of the backing metal 2 are welded together with the groove portions 1a and 1a of the steel plates 1 and 1 as shown in FIG. By doing so, the welding material (weld bead) 3 reaches the back side of the abutting portion to become a welded back bead 3a, and the groove portions 1a, 1a of these steel plates 1, 1 are completely welded. .

As a single-sided butt welding method, a method of arranging and welding a backing material such as ceramics or copper on the back side of the groove portion (see, for example, Patent Document 1), on the back side of the groove portion between the welded portions. There has been proposed a welding method (see, for example, Patent Document 2) in which a copper backing member having a groove for an argon gas reservoir facing the groove portion is arranged to suppress oxidation of the back bead.
Japanese Patent No. 31899643 JP-A-8-206830

  By the way, as shown in FIG.7 and FIG.8, in the structure which welded the backing metal 2 to the groove parts 1a and 1a of the steel plates 1, 1, the base part 3b of the welding material (weld bead) 3 is the steel plates 1, 1 and This is the part where the backing metal 2 is in contact. The root portion 3b is a stress concentration portion due to poor penetration due to heat deprived from the molten metal by the backing metal 2, local shrinkage, and residual stress due to shrinkage deformation of the weld back bead 3a during cooling of the weld. There is a great risk of occurrence of weld defects such as fine cracks resulting from them.

  Further, due to the various factors described above, the backing metal 2 is warped as shown by the arrow B in FIG. 8, and a sharp acute angle θ gap is generated between the steel plates 1, 1 and the backing metal 2, and the notch sensitivity is high. In particular, at the time of loading after welding, there is a sudden stiffness change part due to welding with the backing metal 2 at the base part 3b of the welding back bead 3a, which causes a problem of high stress due to stress concentration and reduces fatigue strength. There's a problem. In particular, when the weld base material and the backing metal are aluminum or an aluminum alloy, the influence of the notch sensitivity is great.

Further, the backing materials disclosed in Patent Document 1 and Patent Document 2 are removed after welding, and are welded together with the welding base material, so that the groove portion of the welding base material is completely formed by the welding back bead. It is different from the backing metal to prove that it was welded.
The present invention has been made in view of the above points, and reduces stress concentration at the welded portion between the weld base material and the backing metal to reduce sudden sensitivity and cutout sensitivity, and to deform the backing metal. An object of the present invention is to provide a structure of a backing metal for welding which is intended to alleviate the generation of residual stress due to shrinkage deformation at the time of welding cooling.

In order to achieve the above object, the invention of the structure of the welding backing metal according to claim 1 is characterized in that the groove portions of the plate-like welding base materials to be welded are brought into contact with each other and contacted with the welding base material. A welding backing metal structure used in a welding method in which a space portion larger than a back bead width generated on the welding base material side of the backing metal is formed on the back side of the welding base material. It is characterized by providing.
The structure of the backing metal for welding according to claim 2 is characterized in that, in claim 1, the thickness of the backing metal is 1/2 to 1/3 of the thickness of the welding base material.

The structure of the backing metal for welding according to claim 3 is characterized in that in claim 1, a marking is provided in the center of the space portion of the backing metal.
The structure of the backing metal for welding according to claim 4 is characterized in that, in claim 1, the width of the space portion of the backing metal is not less than 1.5 times the width of the back bead.
According to a fifth aspect of the present invention, there is provided a welding backing metal structure according to the first aspect, wherein one side of the space portion is opened laterally.

  According to the structure of the backing metal for welding according to claim 1, by providing a space larger on the welding base material side of the backing metal than the back bead width generated on the back side of the welding base material, The wave bead is prevented from cooling rapidly and the generation of residual stress due to shrinkage deformation of the welded part (boundary) between the welded material and the welded base metal can be reduced as much as possible. Can be planned. Moreover, the defect of the weld bead crack at the time of welding cooling can be reduced, and the fatigue strength at the time of load can be improved.

Moreover, according to the structure of the backing metal for welding according to claim 2, the backing metal is made of the welding material by setting the thickness of the backing metal to 1/2 to 1/3 of the thickness of the welding base metal. When melted and solidified, the backing metal is deformed, and the occurrence of residual stress can be reduced.
Further, according to the structure of the backing metal for welding according to claim 3, the groove width (root gap) in the butt welding and the space part of the backing metal are provided by providing a marking in the center of the space part of the backing metal. As a result, it is easy to align the center and improve workability, and it is easy to ensure the quality of welding.

  According to the structure of the backing metal for welding according to claim 4, the width of the space portion of the backing metal is 1.5 times larger than the width of the back bead, so that the groove width in the butt welding is increased. Center alignment between the center and the backing metal space is facilitated and workability is improved, and at the same time, the penetration depth is approximately between the base of the welded back bead and the side wall forming the backing metal space. This space part acts as a heat-insulating space and a deformable space for the backing metal during welding, preventing the occurrence of residual stress due to rapid cooling by the backing metal and shrinkage of the weld bead. it can.

  According to the structure of the welding backing metal of claim 5, the backing metal can be a cantilever structure, and when the steel pipe as the welding base material is butt welded, It is possible to easily cope with this by temporarily fixing the non-opening side to the inner side of the steel pipe opening end on one side and inserting the open side of the space into the opening of the other side of the steel pipe.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view of the structure of a welding backing metal according to the present invention, and is inclined at a predetermined angle, for example, 45 °, of a steel plate 1, 1 as a welding base material to be welded on one side. End surfaces 1a and 1a (hereinafter referred to as “groove portions 1a and 1a”) to be formed are opposed to each other in a substantially V shape with a lower end 1c having a predetermined groove width (root gap) l.

  The backing metal 5 is a steel plate made of the same material as that of the steel plate 1 as a welding base material, and the thickness of the backing metal 5 is approximately 1/2 to 1/3 of the thickness of the steel plate 1. The length is the same as the weld length of the steel plates 1 and 1, and the width W is approximately 1.5 times the groove portion, that is, the maximum width L of the opposing end surfaces 1a and 1a. . As shown in FIG. 2, a groove 5b serving as a space portion wider than the weld back bead width Z is formed at the center of the front surface 5a of the backing metal 5 facing the back side surfaces 1b and 1b of the steel plates 1 and 1. 1 and 1 along the welding direction (hereinafter referred to as “longitudinal direction”).

The groove 5b has a width w that is at least 1.5 times the weld back bead width Z (w ≧ 1.5Z), a depth Y that is substantially the same as the groove width l, and a bottom surface 5c that is a flat surface. ing. The corner R formed by the bottom surface 5c and both side surfaces of the groove 5b is generated when the groove 5b is processed, and may be the corner R as shown in the figure, or may be a right angle.
A marking line 5d (marking) is provided along the longitudinal direction at the center of the bottom surface 5c of the groove 5b. For example, when the groove 5b of the backing metal 5 is formed by extrusion molding, the marking line 5d may be a chevron-shaped ridge or groove, and when formed by a milling machine, the marking line 5d may be marked during processing.

Hereinafter, butt one-side welding using a backing metal will be described.
As shown in FIGS. 1 and 2, the surface 5a of the backing metal 5 is brought into contact with the back side surfaces 1b and 1b of the steel plates 1 and 1, and the marking line 5d at the center of the groove 5b is positioned at the center of the groove width l. And are supported by a jig (not shown). As a result, the center of the groove 5b of the backing metal 5 can be easily and accurately aligned with the center of the groove width l. In this case, both ends of the outer edge portion on one side along the longitudinal direction of the backing metal 5 or appropriate locations along the longitudinal direction are spot welded to the rear side surface 1b of the corresponding steel plate 1 and temporarily fixed. May be. In this state, a closed space portion S having a width Y and a depth Y is defined below and on both sides of the groove width l of the steel plates 1 and 1.

  Next, as shown in FIG. 2, the facing groove portions 1 a, 1 a and the groove width l of the steel plates 1, 1 are welded by, for example, TIG welding. During this welding, the groove portions 1a and 1a of the steel plates 1 and 1 and the central portion of the bottom portion 5c of the groove 5b of the backing metal 5 are melted and welded. In the groove portions 1a and 1a of the steel plates 1 and 1, portions 1a 'and 1a' having a thickness of about a groove width l from the surface thereof are melted together with the welding material 3 (hereinafter referred to as "melting portion 1a '"). Further, the bottom surface 5c of the groove 5b of the backing metal 5 is melted and welded together with the welding material 3 with a depth portion 5c ′ of approximately the groove width l (hereinafter referred to as “melting portion 5c ′”).

Thereby, the welding back bead 3a is formed in the back side of the groove width d of the steel plates 1 and 1, and these steel plates 1 and 1 are welded. Further, since the center portion of the groove 5b of the backing metal 5 can be easily matched with the center of the groove width l of the steel plates 1, 1 by the marking line 5d of the backing metal 5, these steel plates 1, 1 are used. It is possible to prevent welding defects.
By the way, since the width w of the groove 5b of the backing metal 5 is set to be 1.5 times or more of the back bead width Z, gaps (space portions) each having a width of approximately 0.25Z are formed on both sides of the back bead width Z. ) Are formed, and the space portion Sa remains between the base portion 3b of the welded back bead 3a projecting inside the steel plate 1 and the opening ends on both the left and right sides of the groove 5b. And this space part Sa acts as the heat insulation space at the time of welding, and the deformable space of the backing metal 5.

  That is, the welding heat generated when the groove portions 1a and 1a are melted is blocked by the space portion Sa and is prevented from being transmitted to the outside of the groove 5b of the backing metal 5, thereby rapidly cooling the backing metal 5; Generation | occurrence | production of the crack (bead crack) from the base part 3b by the shrinkage | contraction of the welding back bead 3a is prevented effectively. Further, since the thickness of the backing metal 5 is as thin as 1/2 to 1/3 of the thickness of the steel plate 1 as the welding base material, the stiffness of the backing metal 5 is low, and the shrinkage of the welding back bead 3a is reduced. Occasionally, deformation occurs as shown by a two-dot chain line in FIG. 2 to greatly reduce the occurrence of residual stress.

  Furthermore, the welded back bead 3a reaching the melted portions 1a ′, 1a ′ of the steel plates 1, 1 and the melted portion 5c ′ of the backing metal 5 has a convex curved surface toward the groove 5b of the backing metal 5. Therefore, the angle θ formed by the base portion 3b, that is, the back side surface 1b of the steel plate 1 and the base portion 3b of the welded back bead 3a is an obtuse angle. For this reason, the stress concentration in the base portion 3b is reduced, generation of high stress in the portion of the base portion 3b during loading is effectively prevented, and the fatigue strength is greatly improved.

  FIG. 4 shows another embodiment of the backing metal of the present invention, and the backing metal 6 is welded (longitudinal direction) to the center of the front surface 6a in contact with the back side surfaces 1b and 1b of the steel plates 1 and 1. A space 6 is formed by forming a notch 6b having a shape opened along one side. At the center of the bottom surface 6c of the notch 6b, a convex marking line 6d having a triangular cross section along the longitudinal direction (welding direction) is provided. The backing metal 6 has a cantilever structure, and the outer edge 6e on the closed side of the notch 6b is temporarily fixed to the back side surface 1b of the steel plate 1 by spot welding or the like.

  The backing metal 6 having such a shape is effective, for example, when it is formed into an annular shape and steel pipes are butt-welded and welded on one side. That is, the outer edge 6e of the backing metal 6 is temporarily fixed to the inner surface of the open end of one steel pipe by spot welding or the like, and the open side of the notch 6b is inserted into the open end of the other steel pipe. The opposing open ends (grooves) of these steel pipes are welded, and the backing metal 6 is welded with a welded back bead.

  In the above-described embodiment, the butt one-side welding is taken as an example, but the present invention is not limited to this. FIG. 5 shows another embodiment of the backing metal of the present invention, in which the backing metal of the present invention is adopted for fillet welding (square joint). In the backing metal 7, the lower end 1 c of the groove portion 1 a of the steel plate and the groove portion 1 c ′ of the steel plate 1 ′ provided substantially perpendicular to the steel plate 1 have a predetermined groove width (root gap) l. The surface 7a on the front side is in contact with the rear side surface 1b and the end surface 1b ′ of the steel plates 1 and 1 ′ having a lave groove shape disposed so as to face each other. A groove 7b as a space S having a width (w ≧ 1.5Z) wider than the weld back bead width Z is formed in the center of the front surface 7a along the longitudinal direction (welding direction) of the steel plates 1 and 1 ′. A convex marking line 7d having a triangular cross section along the longitudinal direction (welding direction) is provided at the center of the groove 7b. The backing metal 7 temporarily fixes the outer surface of the backing metal 7 to the end faces 1b, 1b 'of the steel plates 1, 1' by welding or the like.

  In the embodiment of the present invention, the shape of the groove is V-shaped and L-shaped, but the present invention is not limited to this. For example, even when other groove shapes (I shape, U shape, J shape, etc.) are applied, it is a matter of course that the same effects as in the present embodiment can be obtained.

It is an assembly | attachment figure of the structure of the backing metal for welding which concerns on this invention. It is a figure which shows the state which welded the welding preform | base_material and backing metal of FIG. It is an enlarged view of the welding part of FIG. It is a figure which shows other embodiment of the structure of the backing metal for welding which concerns on this invention. It is a figure which shows other embodiment of the structure of the backing metal for welding which concerns on this invention. It is an assembly drawing of the structure of the conventional backing metal. It is a figure which shows the state which welded the welding preform | base_material and backing metal of FIG. It is an enlarged view of the welding part of FIG.

Explanation of symbols

1, 1 'steel plate (welded base metal)
1a groove part d groove width 3 welding material 3a weld back wave bead 3b base part of weld back wave bead 5, 7 backing metal 5b groove (space part)
5c Bottom 5d, 7d Marking line S, Sa Space 6 Back metal 6b Notch (space)

Claims (5)

It is a structure of a welding backing metal used in a welding method in which the groove portions of the plate-like welding preforms to be welded are butted together and a backing metal that contacts the welding preform is disposed,
A structure of a welding backing metal, wherein a space larger than a width of a back bead generated on the back side of the welding base material is provided on the welding base material side of the backing metal.   The structure of the backing metal for welding according to claim 1, wherein the thickness of the backing metal is 1/2 to 1/3 of the thickness of the welding base material.   2. The structure of the backing metal for welding according to claim 1, wherein a marking is provided in the center of the space of the backing metal.   The structure of the backing metal for welding according to claim 1, wherein the width of the space portion of the backing metal is 1.5 times or more the width of the back bead.   The structure of the backing metal for welding according to claim 1, wherein one side of the space portion is opened laterally.

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