JP2013230479A - Welded joint structure for steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welded joint structure for a steel material capable of preventing an early fracture of a fillet welded section by performing butt-welding using a weld material having strength lower than that of a base material and by using a reinforcement material (backing metal) of the shape having a small stress concentration, and attaining easy construction work and low cost.SOLUTION: In a welded joint structure, base materials 3 are butt-welded with a weld metal having strength lower than that of the base material 3, and a reinforcement material 4 having strength lower than that of the base material 3 is fillet-welded on a back face side of the base material 3 by using the weld material having strength lower than that of the base material 3. An inclined angle is formed between an axis right-angled direction of the base material and a fillet welding line, and a distance from a butt-welded section 1 is set up to be larger at a width-directional intermediate section in comparison with a width-directional end section. In this way, a fully strong joint can be attained at low cost without requiring special weld management by using the weld material having strength lower than that of the base material 3 for the butt-welded section 1 and the fillet welded section 2. Further, stress concentration to an end of the fillet welded section 2 is hardly generated, defects from the end of the fillet welded section 2 can be prevented and the early fracture of the fillet welded section 2 can be prevented.

Description

  [Technical Field] The present invention relates to a welded joint structure for a steel material which prevents a premature breakage at a fillet weld portion, is easy to construct, and is low-cost in a joint structure in which high-strength steel materials are butt-welded.

  In general, when steel materials are butt-welded, for example, as shown in FIG. 3, the base materials are butt-welded in the material axis direction and welded. A backing metal, which is a reinforcing material, is applied to the back surface of the butt welded base metal, and fillet welding is performed at about four locations, and the base material and the backing metal are welded.

  For example, Patent Document 1 is a prior art document relating to a welded joint of steel materials.

  In Patent Document 1, the entire thickness of the backing metal and the base metal is welded, and the stress is transmitted to the backing metal, thereby reducing the stress of the butt weld of the base material and reducing the strength of the butt weld. Also disclosed is a welding method for forming a fully strong joint.

JP 2011-068673 A

  In the prior art shown in FIG. 3, when a tensile force is applied to the welded joint, the stress is concentrated on the end of the fillet weld line where the base metal and the backing metal are welded, and the strength tends to become a starting point of breakage. Hard to come out.

  In the invention described in Patent Document 1, the entire circumference of the backing metal and the base metal is welded. However, when a tensile force is applied to the welded joint, the stress is also applied to the end portion that is a discontinuous portion of the joint cross section. Concentrate, and the edge becomes the starting point of breakage.

  In particular, in Patent Document 1, the stress of the front fillet portion becomes high, and the strength of the other fillet welded portions excluding the front fillet from the entire peripheral fillet cannot be efficiently exhibited. Because of this, there is a concern about the early breakage of the fillet welded portion, which may not be a fully strong joint.

  In addition, when a welded joint of a base material, which is generally a super high strength steel with a strength of 1000 N, is manufactured by simple butt welding, overmatching is achieved in which the welding material is at least as strong as the base material. Is expensive because special welding management and welding materials are required.

  The present invention has been made to solve such problems. In a welded joint structure of steel materials in which high-strength base metals are butt-welded to each other, butt welding is performed using a welding material having a strength lower than that of the base material. By using a reinforcing material (back metal) with a low stress concentration, it is possible to prevent early breakage at fillet welds and to provide a welded joint structure for steel that is easy and low in cost. It is what.

  The present invention is a welded joint structure of steel materials that connect base materials to each other in the axial direction, and the base materials are butt welded with a weld metal having a strength smaller than that of the base material, on the back side of the base material. A reinforcing material having a strength lower than that of the base metal is fillet welded by a weld metal having a strength lower than that of the base material, and a direction perpendicular to the base metal axis and the fillet weld line has an inclination, and the distance from the butt weld is It is a welded joint structure of steel material characterized in that it is larger at the widthwise intermediate portion than at the widthwise end portion.

  The present invention uses a welding material having a strength lower than that of the base material for a butt weld portion between the base materials, a reinforcing material (back metal) attached to the back surface of the base material, and a fillet weld portion between the base material and the reinforcing material. As a result, it is possible to realize a fully strong joint at low cost without requiring special welding management.

  Also, in the fillet welded portion of the reinforcing material that also serves as the backing metal and the base metal, the direction perpendicular to the base metal axis and the fillet weld line are inclined, and the distance from the butt weld of the base material is the width direction end. Compared to the above, by increasing the width in the middle part, stress concentration at the end of the fillet weld is less likely to occur, preventing defects from the end and preventing early breakage at the fillet weld. It is possible.

  For example, if a reinforcing material having a substantially triangular shape as shown in FIGS. 1 and 2 or a reinforcing material having a semi-elliptical shape and a fillet weld having a shape corresponding thereto are used, the fillet weld is larger than in the prior art. As a result, the weld area with the base metal increases.

  The welded joint structure for steel in the present invention is characterized in that the base metal axial direction and the inclination angle of the fillet weld line are constant over the entire length of the weld line.

  In this case, the inclination angle of the fillet weld line does not change in the middle of the weld line, and stress concentration is unlikely to occur in the middle of the weld line, which is suitable when the present invention is applied to an ultra-high strength base material sensitive to stress concentration. .

  In addition, if the shape of the fillet weld line between the base metal and the reinforcing material is a straight line as shown in FIG. 1, the base metal axis perpendicular direction and the fillet weld line have the same inclination angle over the entire length of the fillet weld line. Therefore, for example, the joint strength of fillet welds can be calculated by the maximum strength formula of the oblique weld seam shown in the Architectural Institute of Japan “Design Guidelines for Steel Structure Limits, 3rd Edition” 2010, page 215 .

  Furthermore, it is desirable that the welded joint structure is a steel material in which an inclination angle gradually increases from the width direction end portion toward the width direction intermediate portion with respect to a straight line connecting the end portions of the fillet weld line. This is because the stress concentration of the base material can be reduced as the cross-sectional change from the base material subjected to the tensile force to the reinforcing material is small.

  As a means for reducing discontinuity in the joint cross section of the steel material and preventing premature fracture, for example, as shown in FIG. 2, the fillet weld line is on the inner side of the straight line connecting the ends of the fillet weld line. The shape of the reinforcing material may be a convex curve.

  In this case, if the change in the tilt angle is discontinuous, stress concentration may occur in the discontinuous part, so the fillet weld line shape may change continuously like an arc or sine curve. It is preferable to use a simple shape.

  Since the welded joint structure of steel according to the present invention has the above-described configuration, the following effects can be obtained.

 (1) Since a welding material having a strength lower than that of the base material of the high-strength steel material can be used, special welding management is not required and costs can be reduced.

 (2) In the fillet welded portion of the reinforcing material that also serves as the backing metal and the base metal, the direction perpendicular to the base metal axis and the fillet weld line are inclined, and the distance from the butt weld of the base material is the end in the width direction. By making the middle part in the width direction larger than the part, stress concentration at the end of the fillet weld is less likely to occur, preventing defects from the end and preventing early breakage at the fillet weld To do.

BRIEF DESCRIPTION OF THE DRAWINGS One Embodiment of the steel-welded joint structure which concerns on this invention is shown, (a) is sectional drawing, (b) is the top view seen from the base material back surface. BRIEF DESCRIPTION OF THE DRAWINGS One Embodiment of the steel-welded joint structure which concerns on this invention is shown, (a) is sectional drawing, (b) is the top view seen from the base material back surface. The example of the prior art used for the welded joint structure of steel materials is shown, (a) is sectional drawing, (b) is a top view.

  Hereinafter, specific embodiments of the present invention will be described. Note that the present invention is not limited to the embodiments described below.

  1 and 2 show an embodiment of a welded joint structure of steel materials according to the present invention, where the base materials 3 are butt-welded in the axial direction (butt welded portion 1), and are attached to the back surface of the base material 3. Is fillet welded to the reinforcing material 4 (fillet welded portion 2).

  Compared to the strength of the base material 3, the butt weld 1 and fillet weld 2 are made of a welding material having a low strength. Conventionally, if a high-strength welding material equivalent to or higher than that of the base metal is used, special welding management is required and the cost is high. However, the welded joint structure of the steel material according to the present invention has a lower strength than the base material. Even if it is a joint structure that uses materials and is easy to construct, the joint structure ensures the strength of the base material.

  Further, in the fillet weld portion 2 between the reinforcing member 4 also serving as a backing metal and the base material 3, the shape perpendicular to the base metal axis and the fillet weld line are inclined.

  In the case of FIG. 1, the inclination angle of the base metal 3 axial direction and the fillet weld portion 2 is constant over the entire length, and the distance from the butt weld portion 1 of the base material 3 is the intermediate in the width direction from the width direction end of the base material 3. The shape gradually increases toward the part.

  In the case of FIG. 2, the fillet welded portion 2 between the reinforcing member 4 and the base metal 3 is inclined in the direction perpendicular to the base metal axis and the fillet weld line in the same manner as in FIG. 1. The shape of the reinforcing material is such that the fillet weld line has an inwardly convex curve with respect to the line connecting the two end portions, and the inclination angle gradually increases from the end portion in the width direction of the base metal toward the intermediate portion in the width direction. It is getting bigger.

  This is effective as a means for reducing discontinuity in the joint cross section of the steel material and preventing early breakage.

  However, if the change in the tilt angle is discontinuous, stress concentration may occur at the discontinuous portion (for example, the top of the isosceles triangle formed by the fillet welded portion 2 in FIG. 1). It is preferable to make the shape such that the inclination angle continuously changes like an arc or a sine curve as shown in FIG.

  If the reinforcing material and the fillet welded portion are shaped as shown in FIGS. 1 and 2, the length of the fillet welded portion is longer than that of the prior art, and the weld area with the base material is increased.

  Further, in such a joint structure, the fillet welded portion 2 indicated by the hatched portion is continuous, whereas the portion where the fillet welded portion 2 is not continuous is formed at the width direction end portion of the base material 3. Yes, it is clearly shorter than the length of discontinuous parts. Therefore, stress concentration at the end of the fillet weld is unlikely to occur, defects from the width direction end of the base metal can be prevented, and early breakage at the fillet weld can be prevented.

1 ... Butt weld,
2 ... fillet weld,
3 ... base material,
4 ... Reinforcing material (backing gold)

Claims (3)

  It is a welded joint structure of steel materials that connect base materials to each other in the axial direction, and the base materials are butt welded with a weld metal having a strength smaller than that of the base material, and smaller than the base material on the back side of the base material The reinforcing material of the strength is fillet welded by a weld metal having a strength smaller than that of the base metal, and the direction perpendicular to the base metal axis and the fillet weld line are inclined, and the distance from the butt weld is the width direction end. A welded joint structure for steel, characterized in that the intermediate portion in the width direction is made larger than that of the steel.   The weld joint structure for steel according to claim 1, wherein an inclination angle of the base metal axis direction and the fillet weld line is constant over the entire length of the weld line.   The weld joint structure for steel according to claim 1, wherein an inclination angle gradually increases from the end in the width direction toward the intermediate portion in the width direction with respect to a straight line connecting the end portions of the fillet weld line. .

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