JP2014008515A - Weld junction of steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a weld junction of a steel material having joint strength higher than the whole cross-section strength of the steel material to be welded, and having superior weld workability and economical efficiency, and thereby weld defects and welding failures can be prevented.SOLUTION: A weld junction 1 of a steel material has a groove on at least one steel material 2, and welded with a weld metal in a substantially elliptical reinforcement groove built up on the weld metal 4 in the groove and on the surface of the steel material 2 continued to the weld metal 4 in the groove, the weld junction having a strength lower than that of the steel material and having reinforcement welding only on a single side of the steel material. A reinforcement weld metal 5 satisfies the following conditional expression, wherein t: board thickness, a: excess weld metal height, l: length from a groove end to a reinforcement end, q: groove angle,s: yield stress degree of the steel material, ands: yield stress degree of the weld metal.

Description

  The present invention is a butt-welded joint for high-strength steel materials, which has a joint strength that is equal to or greater than the total cross-sectional strength of the steel materials to be welded, is excellent in welding workability and economy, and prevents welding defects and welding work defects. It relates to the joint.

  Generally, when a steel material is butt-welded, an overmatching joint in which the strength of the welding material is larger than the strength of the base steel material is required. However, in order to realize an overmatching joint of high-strength steel materials, the cost is high and the construction is not easy, so welding may be performed with a welding material having a strength lower than that of the base material.

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

  In Patent Document 1, the inside of the groove of both members to be butt welded is welded with a material having a lower strength than that of the same member, and the weld metal in the groove and the surfaces of both members adjacent to the weld metal are further provided. A weld joint is disclosed in which a weld metal is built up, and the weld metal in the groove and the weld metal built up on the surfaces of both members adjacent to the weld metal are continuous.

Japanese Patent Laid-Open No. 60-027474

Conventionally, in butt welding of ultra-high-strength steel with a tensile strength of 780 N / mm ² or more, in order to ensure the strength of the welded part to be equal to or higher than that of the steel base material, special welding materials and residual heat and afterheating Therefore, special welding construction management such as the above has become necessary, leading to a decrease in welding workability and an increase in cost.

  Furthermore, from the viewpoint of securing strength, various alloying elements are added to the welding material, so that the weldability is poor compared to the steel base material, and welding defects such as weld cracks in the first layer of the weld zone and poor welding are also issues. there were.

  In Patent Document 1, a welding material having a slightly lower strength than a steel base material is used for overlay welding in the groove of the steel member and on the surface of the steel material, and the weld metal in the groove and the weld metal on the surface of the steel material are connected. A continuous welding method is disclosed.

  However, in the welded joint described in Patent Document 1, overlay welding metal is provided on the steel surface for reinforcing joint strength. If the shape and size are not appropriate, if a tensile force is generated in the welded joint, It is conceivable that stress concentrates on the end or discontinuous portion of the weld overlay, causing cracks in the weld early and eventually causing breakage. In addition, build-up welding to the steel surface must be kept to a minimum from the viewpoint of cost rationalization.

  The present invention is intended to solve such problems. In a butt-welded joint made of high-strength steel, the joint has a strength greater than the total cross-sectional strength of the steel to be welded, and is excellent in welding workability and economy. An object of the present invention is to provide a welded joint portion of a steel material capable of preventing welding defects and welding construction defects.

  A weld joint of a steel material according to the present invention is a butt weld joint of steel material having a groove in at least one steel material, and is a substantially elliptical arc that is built up on the surface of the weld metal in the groove and the steel material continuous therewith. The shape of the reinforcing weld metal is such that the shape of the reinforcing weld metal satisfies the following conditional expression (1). It is characterized by this.

t: Steel plate thickness (mm)
a: Extra height of reinforced weld metal (mm)
l: Length from the open end of the steel material to the reinforced embankment end (mm)
q: Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal

  The present invention uses a welding material that is excellent in weldability and weldability and has a low strength against steel, and ensures the strength of the joint within the groove and the overall cross-sectional strength of the steel on the surface of the steel. The above-mentioned problem has been solved by carrying out reinforcement welding in a substantially elliptical arc shape which is the minimum and optimum shape of the above.

Further, the optimum shape of the above-mentioned reinforced weld metal is in contact with each other at a point C on the extension line of the groove surface as shown in FIG. 1 as a result of numerical analysis based on limit analysis assuming a plane stress state as a yield condition. It is a substantially elliptical shape that envelops two similar elliptical arcs 1 and 2. The elliptic arcs 1 and 2 are elliptic arcs having an aspect ratio of 1: 3 ^1/2 from the result of limit analysis.

  Oval arc 1 is an oval arc centered on O (0, 0) and expressed by the following equation (2). When tensile force is generated in the joint, weld metal and reinforcement inside the groove corner BOC It is derived from the condition that the joint strength when the prime weld metal linearly reaches the degree of yield stress is equal to the strength when the entire cross section of the steel base material yields.

  Elliptical arc 2 is an elliptical arc centered on E (t, t tanθ) and expressed by the following formula (3). When a tensile force is generated in the joint, the weld metal yields on the groove surface OE. In addition, the joint strength when the reinforcement weld metal inside the corner CED reaches the degree of yield stress linearly from the point E is derived from the condition that the joint strength is equal to the strength when yielding the entire cross section of the steel base metal .

  From the above, in order to ensure that the weld joint has a strength equal to or higher than that of the steel base material, it is only necessary to carry out reinforcement welding over a substantially elliptical arc BCD enveloping the elliptical arcs 1 and 2.

  Therefore, in the present invention, the optimum shape of the reinforcing weld metal necessary for securing the weld joint with a strength equal to or higher than that of the steel base material, and the above-mentioned conditional expression (1) when the reinforcing fill is provided on one side of the steel material. Treat as a nearly elliptical arc to fill.

  Further, in the case where reinforcement welding is provided on both sides of the groove, the shape of the reinforcement welding metal satisfies the following conditional expression (4).

d ', d ”: groove depth (mm)
a ', a ": Extra height of reinforced weld metal (mm)
l ', l ”: Length from the open end of the steel material to the tough end of reinforcement (mm)
q ', q ": Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal

  The case where the reinforcement is provided on both surfaces of the steel material is treated as a substantially elliptic arc satisfying the conditional expression (4).

  Strictly speaking, the elliptical arc satisfying the conditional expressions (3) and (4) passes through the inside of the substantially elliptical arc BCD, but in reality, the effect of plastic restraint by the steel base material of the welded joint is expected. The joint strength is higher than the numerical analysis result, so there is no problem in securing the joint strength.

In the welded joint portion of the steel material according to the present invention, the steel material is desirably a high strength steel having a tensile strength of 780 N / mm ² or more.

Conventionally, in butt welding of ultra-high-strength steel with a tensile strength of 780 N / mm ² or more, in order to ensure the strength of the welded part to be equal to or higher than that of the steel base material, special welding materials and residual heat and after-heating etc. Special welding construction management is required, and degradation of welding workability and cost increase have been problems. Further, various alloy elements are added to the welding material from the viewpoint of securing strength, and the weldability is poor compared with the steel base material, and there are problems of welding defects and poor welding.

Therefore, if the weld joint of the present invention is applied to a welded joint of high strength steel with a tensile strength of 780 N / mm ² or more, welding workability is good, welding defects and welding defects are eliminated, and costs can be reduced. Is possible.

  Further, it is desirable that the weld metal in the groove and the reinforcing weld metal of the steel material are constituted by one weld bead integrated.

  For example, in high heat input welding that performs one-pass welding such as electrogas arc welding or submerged welding, the toughness of the heat-affected zone (HAZ) of the steel to be welded tends to be a problem, but according to the present invention, the amount of welding can be reduced. Accordingly, it is possible to reduce the welding heat input, so that the effect of improving the toughness of the heat-affected zone (HAZ) of the welded steel can be expected. Further, in the above-described one-pass welding, it is easy to finish the reinforcing weld metal in a smooth shape, and therefore, fatigue failure due to bead irregularity is less likely to occur.

  The welded joint portion of the steel material according to the present invention has the above configuration, and the following effects are obtained.

(1) For welded joints of high-strength steel materials with a tensile strength of 780 N / mm ² or more, when using a welding material with strength equal to or higher than that of the steel base material in general, it is necessary to manage residual heat and after-heating, etc. However, when a welding material having a strength lower than that of the steel base material is used, the above-described welding workability, welding defects, and welding defects are improved.

(2) If the weld joint of the steel according to the present invention is applied to a butt weld joint of high strength steel having a tensile strength of 780 N / mm ² or more, the effect of reducing the welding amount is great.

 (3) It is easy to prevent welding defects such as undercut at the open tip of the steel surface. In order to prevent undercutting, the length l from the necessary open end portion of the steel material to the reinforcement welded metal toe portion may be at least about 5 mm. It is also easy to prevent welding defects such as undercuts at the open front end of the steel surface.

 (4) In high heat input welding such as electrogas arc welding or submerged arc welding, for example, deterioration in the toughness of the heat affected zone (HAZ) of the steel to be welded is likely to be a problem. Since the welding heat input can be reduced along with the reduction of the welding temperature, the effect of improving the toughness of the heat-affected zone (HAZ) of the steel to be welded can be expected.

1 shows an embodiment of a welded joint portion of steel materials according to the present invention, and is a cross-sectional view in the case where reinforcement welding is performed on one surface of a steel material. It is explanatory drawing which expanded embodiment of FIG. 1 shows an embodiment of a welded joint portion of steel materials according to the present invention, and is a cross-sectional view in a case where reinforcement welding is performed on both surfaces of the steel materials.

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

  The present invention can be applied to a butt weld joint of steel materials in a structural member. For example, flat joints of steel plates, column joints of steel pipe columns and H-shaped steel columns, joints between steel pipe columns and through diaphragms, joints between through diaphragms and beam flanges, and the like.

  1 and 2 show an embodiment in which reinforcement welding is provided on one surface of a steel material in a welded joint 1 of the steel material according to the present invention. The end portions of one steel material 2 and the other steel material 3 are butted together and a groove EOA is provided at the tip of the steel material 2. On the outside of the weld metal 4 in the groove having a groove angle θ, a reinforcing weld metal 5 is provided in a substantially elliptic arc BCD formed from one steel material 2 to the other steel material 3. A backing metal 6 is welded to the back surface of the steel material 2.

  The elliptical arc 1 is an elliptical arc that can be expressed by the following equation (5) around O (0,0). When a tensile force is generated in the welded joint 1, the joint strength when the weld metal 4 in the groove and the reinforcing weld metal 5 linearly reach the yield stress level within the groove corner BOC is the steel base. The required shape of the reinforcement weld metal 5 derived from the condition that it is equal to the strength when yielding the entire cross section of the material is shown.

t: Steel plate thickness (mm)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal

  The elliptical arc 2 is an elliptical arc that can be expressed by the following equation (6) with E (t, t tanθ) as the center. When a tensile force is generated in the weld joint 1, the weld metal reaches the yield stress level on the groove surface OE, and the reinforcement weld metal inside the corner CED linearly reaches the yield stress level from the point E. This shows the required shape of the reinforcing weld metal derived from the condition that the joint strength in this case is equal to the strength in the case of yielding the entire cross section of the steel base material.

t: Steel plate thickness (mm)
q: Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal

  From the above, in order to ensure that the weld joint has a strength equal to or higher than that of the steel base material, it is only necessary to perform reinforced overlay welding over the elliptical arc BCD enveloping the elliptical arcs 1 and 2.

  Therefore, the optimum shape of the reinforcing weld metal required to secure the weld joint with a strength equal to or higher than that of the steel base material is a substantially elliptical arc that satisfies the following conditional expression (7) when a reinforcing fill is provided on one side of the steel material. It becomes.

t: Steel plate thickness (mm)
a: Extra height of reinforced weld metal (mm)
l: Length from the open end of the steel material to the reinforced embankment end (mm)
q: Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal

  In addition, although the elliptical arc that satisfies the conditional expression (7) in the case where the reinforcement is provided on one side of the steel material, strictly speaking, it passes through the inside of the substantially elliptical arc BCD, it is actually due to the steel base material of the welded joint portion. Since the effect of plastic restraint can be expected and the joint strength is higher than the numerical analysis result, there is no problem in securing the joint strength.

  Further, in order to prevent undercut of the weld metal, the length l from the open end E of the steel material to the reinforcing peak weld metal toe D is preferably 5 mm or more. Moreover, in order to prevent welding defects and cracks such as blow holes in the first layer, the groove angle θ provided in the steel material to be welded is preferably about 30 to 60 °.

  FIG. 3 shows an embodiment in which reinforcement welds are provided on both surfaces of the steel material in the weld joint 1 of the steel material according to the present invention. As in FIGS. 1 and 2, the ends of one steel material 2 and the other steel material 3 are butted and joined, and the steel material 2 is provided with grooves having different groove angles θ ′ and θ ″ on the left and right. In this case, the weld metal 4a, 4b in the groove and the reinforcement weld metal 5a, 5b are provided in the same manner as the method of calculating from the elliptic arcs 1, 2 described above, and the reinforcement weld metal 5a, When 5b is provided, it is treated as a substantially elliptic arc satisfying the following conditional expression (8).

d ', d ”: groove depth (mm)
a ', a ": Extra height of reinforced weld metal (mm)
l ', l ”: Length from the open end of the steel material to the tough end of reinforcement (mm)
q ', q ": Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal

  Generally, with regard to the strength of the steel material used, if welding is performed with a welding material in which the strength of the weld metal is equal to or higher than that of the steel base material in the welded joint of high strength steel material, it is necessary to manage residual heat, etc. Problems such as a decrease in welding, welding defects, and welding defects.

Therefore, particularly when the present invention is applied to a welded joint made of a high strength steel material having a tensile strength of 780 N / mm ² or more and a welding material in which the strength of the weld metal is low with respect to the steel base material, the welding amount is suppressed. However, it is extremely useful because it can solve the problem of welding workability, welding defects, and welding defects at the same time.

  Further, the weld metal in the groove and the reinforcing weld metal 6 may be constituted by a plurality of weld beads, or both may be constituted by one weld bead.

Therefore, the welding method of the weld joint 1 is used not only for multi-layer welding such as carbon dioxide (CO ₂ ) gas arc welding but also for high heat input welding that performs one-pass welding such as electrogas arc welding and submerged arc welding. it can. As the groove shape provided in the steel material 2 of the welded joint 1, a la shape, a V shape, a K shape, an X shape or the like can be applied.

  In addition, although the butt weld part of the steel materials from which plate | board thickness differs is shown, this invention is applicable also to the butt-weld part of steel materials with the same plate | board thickness.

1 ... welded joint,
2 ... Steel,
3 ... Steel,
4, 4a, 4b ... weld metal in the groove,
5, 5a, 5b ... Reinforcement weld metal,
6 ... backing material,
a, a ', a "... height of reinforcement,
d ', d "... height of reinforcement,
t ... steel plate thickness,
θ, θ ′, θ ″: groove angle,
l, l ′, l ″: Length from the open end of the steel material to the end of the reinforced weld metal

Claims (4)

A steel butt weld joint having a groove in at least one steel material, wherein a weld metal in the groove and a substantially elliptical arc-shaped reinforcing weld metal deposited on the surface of the steel material continuous thereto are welded. A welded joint portion of steel material that is lower in strength than steel material and that is subjected to reinforcement welding on only one surface of the steel material so that the shape of the reinforcement welding metal satisfies the following conditions.

t: Steel plate thickness (mm)
a: Extra height of reinforced weld metal (mm)
l: Length from the open end of the steel material to the reinforced embankment end (mm)
q: Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal A steel butt weld joint having a groove in at least one steel material, wherein a weld metal in the groove and a substantially elliptical arc-shaped reinforcing weld metal deposited on the surface of the steel material continuous thereto are welded. 2. The steel material according to claim 1, wherein the steel material has lower strength than that of the steel material, and reinforcement welding is performed on both surfaces of the steel material so that the shape of the reinforcement welding metal satisfies the following conditions. Welded joints.

d ', d ”: groove depth (mm)
a ', a ": Extra height of reinforced weld metal (mm)
l ', l ”: Length from the open end of the steel material to the tough end of reinforcement (mm)
q ', q ": Angle between the axis perpendicular to the steel axis and the groove (°)
_b s _y : Yield stress of steel (N / mm ² )
_w s _y : Yield stress (N / mm ² ) of weld metal in groove and reinforced weld metal The steel steel weld joint according to claim 1 or 2, wherein the steel material has a tensile strength of 780 N / mm ² or more.   The weld joint of steel materials according to claim 1, 2 or 3, wherein the weld metal in the groove and the reinforcing weld metal are one weld bead.

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