JP5900189B2 - Welded joint of steel and method of forming welded joint - Google Patents

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. The present invention relates to a method for forming a joint and a weld 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 / mm2 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 was required, 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 bonded together. 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 part of a steel material and a method for forming the welded joint part, which can prevent welding defects and welding work 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. So that the shape of the reinforcement welded metal portion satisfies the following conditional expression (1). It is characterized by that.

t: Steel plate thickness (mm)
a: Additional height of reinforcement weld metal part (mm)
l: Length (mm) from the open end of the steel material with a groove to the toe of the reinforced metal part
θ : Angle between the axis perpendicular to the steel axis and the groove (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm ² ) of weld metal part in groove and reinforced weld metal part

  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-described reinforced weld metal part is in contact with each other at a point C on the extension line of the groove surface as shown in FIG. 1 based on the result of the numerical analysis based on the limit analysis assuming the plane stress state as the yield condition. It is a substantially oval shape that envelops two similar ellipses 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 formula (2). When a tensile force is generated in the joint, the weld metal part and the inside of the groove corner BOC It is derived from the condition that the joint strength when the reinforced weld metal part linearly reaches the yield stress level is equal to the strength when the entire cross section of the steel base material yields.

Oval arc 2 is an oval arc centered on E (t, t tanθ) and expressed by the following formula (3). When tensile force is generated at the joint, the weld metal part yields on the groove surface OE. From the condition that the joint strength when the strength reaches the stress level and the reinforcement weld metal part inside the corner CED linearly reaches the yield stress level from the point E is equal to the strength when yielding the entire cross section of the steel base metal Led.

  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 reinforcement welded metal part necessary for securing the weld joint with a strength equal to or higher than that of the steel base material is obtained. When the reinforcement welded metal part is provided on one side of the steel material, the above conditional expression Treat as a nearly elliptical arc that satisfies (1).

In the case where the reinforcing weld metal portions are provided on both sides of the groove, the shape of the reinforcing weld metal portions satisfies the following conditional expression (4).

d ', d ": groove depth of each groove (mm)
a ', a ": weld reinforcement height of each reinforcing up welding metal portion (mm)
l ', l ": Length from the open tip of each groove in the steel material having a groove to the toe of each reinforced weld metal part corresponding to the groove (mm)
θ ', θ ": angle axis and each groove perpendicular to the timber axis of the steel material forms (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm ² ) of weld metal part in groove and reinforced weld metal part

The case where reinforcing weld metal portions are provided on both surfaces of the steel material is treated as a substantially elliptic arc satisfying the above 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 materials with a tensile strength of 780 N / mm2 or more, special welding materials and special heat such as preheating and after-heating are required in order to ensure the strength of the welds at least equal to that of the steel base material. Therefore, it is necessary to manage the welding work properly, and there is a problem that the welding workability is lowered and the cost is increased. 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 welded joint of the present invention is applied to a welded joint made of high strength steel with a tensile strength of 780 N / mm2 or more, welding workability is good, welding defects and weld defects can be eliminated, and costs can be reduced. It is.

Also, the weld metal portion and the reinforcing overlay weld metal portion in GMA steel is preferably configured by a single weld bead together.

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 portion into 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-tensile steel with a tensile strength of 780 N / mm2 or more, if a welding material with strength equal to or higher than that of the steel base material is generally used, 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 toe end portion of the reinforcing weld metal portion should 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 a reinforcing weld metal portion is provided on one surface of a steel material in a weld 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 portion 4 in the groove at the groove angle θ, a reinforcing weld metal portion 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 weld joint 1, the joint strength when the weld metal part 4 and the reinforced weld metal part 5 in the groove linearly reach the yield stress level is within the groove corner BOC. The required shape of the reinforcing weld metal part 5 derived from the condition that the steel base material is equal in strength to the case where the entire cross section yields is shown.

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

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 at weld joint 1, the weld metal part reaches the yield stress level on the groove surface OE, and the reinforcement weld metal part inside the corner CED from point E linearly yield stress level. The required shape of the reinforcing weld metal part derived from the condition that the joint strength in the case of reaching the above is equal to the strength in the case of yielding the entire cross section of the steel base material is shown.

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

  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 reinforcement welding over a substantially elliptic arc BCD that envelops the elliptic arcs 1 and 2.

Therefore, the optimum shape of the reinforcing weld metal part necessary to secure the weld joint with a strength equal to or higher than that of the steel base material is as follows when the reinforcing weld metal part is provided on one side of the steel material: A substantially elliptical arc that satisfies

t: Steel plate thickness (mm)
a: Additional height of reinforcement weld metal part (mm)
l: Length (mm) from the open end of the steel material with a groove to the toe of the reinforced weld metal part
θ : Angle between the axis perpendicular to the steel axis and the groove (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm ² ) of weld metal part in groove and reinforced weld metal part

In addition, the elliptical arc that satisfies the conditional expression (7) in the case where the reinforcing weld metal part is provided on one surface of the steel material strictly passes through the inside of the substantially elliptical arc BCD, but actually the steel material of the welded joint portion. Since the effect of plastic restraint by the base metal can be expected and the joint strength is higher than the numerical analysis result, there is no problem in securing the joint strength.

In order to prevent undercut of the weld metal, the length l from the open end E of the steel material to the toe D of the reinforced weld metal portion 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 reinforcing weld metal parts 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. The weld metal portions 4a and 4b and the reinforcing weld metal portions 5a and 5b are provided in the groove, respectively, which is the same as the method of calculating from the elliptic arcs 1 and 2 described above, and reinforcing welds on both surfaces of the steel material. When the metal portions 5a and 5b are provided, they are handled as substantially elliptic arcs that satisfy the following conditional expression (8).

d ', d ": groove depth of each groove (mm)
a ', a ": weld reinforcement height of each reinforcing up welding metal portion (mm)
l ', l ": Length from the open tip of each groove in the steel material having a groove to the toe of each reinforced weld metal part corresponding to the groove (mm)
θ ', θ ": angle axis and each groove perpendicular to the timber axis of the steel material forms (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm ² ) of weld metal part in groove and reinforced weld metal part

Generally, with regard to the strength of the steel material to be used, if welding is performed with a welding material in which the strength of the weld metal part is equal to or greater than that of the steel base material in the welded joint part of high-strength steel material, it is necessary to manage residual heat, etc. Problems such as deterioration of weldability, 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 portion is low with respect to the steel base material, the welding amount is reduced. It is extremely useful because it can solve the problem of welding workability deterioration, welding defects and poor welding at the same time.

Further, the weld metal portion in the groove and the reinforcing weld metal portion 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 can be used not only for multi-layer welding such as carbon dioxide (CO2) gas arc welding but also for high heat input welding for performing one-pass welding such as electrogas arc welding and submerged arc welding. . 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 part in the groove,
5, 5a, 5b ... Reinforcement weld metal part ,
6 ... backing material,
a, a ′, a ″… extra height of the reinforcing weld metal part ,
d ', d "... groove depth of the groove ,
t ... steel plate thickness,
θ ... An angle θ ′, θ ″ formed by an axis perpendicular to the steel material axis and an angle θ formed by an axis perpendicular to the steel material axis and each groove l Reinforced from the open tip of the steel material having the groove Length to the toe of the metal (mm)
l ', l "... Length from the open tip of each groove in the steel material having a groove to the toe of each reinforcing weld metal part corresponding to the groove (mm)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress level of weld metal part in groove and reinforced weld metal part
(N / mm ² )

Claims (6)

A welded joint of a steel material having a butt weld welded in a state where a pair of steel materials having a groove in at least one steel material are butted against each other in the material axis direction , wherein the pair of steel materials has a tensile strength is is at both 780N / mm ² or more, the butt weld, the a weld metal portion joining said pair of steel between in the GMA, meat continuous to and out of the GMA to the weld metal portion A welded welded metal part that joins the pair of steel materials outside the groove, and the welded metal part and the welded welded metal part are lower in strength than the paired steel materials. Formed of metal, and the reinforcement welded metal portion is in contact with each other at a point on the extension of the groove surface of the groove, and the length in the material axis direction of the steel material and the length in the direction perpendicular to the material axis direction the ratio of 3 ^1/2: 1 is of two similar figures oval A substantially elliptical enveloping of the arc, weld joint of a steel material, characterized in that has a shape that satisfies the lower Symbol conditions.

t: Steel plate thickness (mm)
a: Additional height of reinforcement weld metal part (mm)
l: Length (mm) from the open end of the steel material with a groove to the toe of the reinforced metal part
θ : Angle between the axis perpendicular to the steel axis and the groove (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm ² ) of weld metal part in groove and reinforced weld metal part The groove is provided on each of the opposing surfaces of the steel material, the weld metal portion is provided in each groove, and the reinforcing weld metal portion is provided outside each groove, respectively. 2. The weld joint of steel according to claim 1, wherein each of the reinforced weld metal portions is provided with a shape that satisfies the following conditions.

d ', d ": groove depth of each groove (mm)
a ', a ": weld reinforcement height of each reinforcing up welding metal portion (mm)
l ', l ": Length from the open tip of each groove in the steel material having a groove to the toe of each reinforced weld metal part corresponding to the groove (mm)
θ ', θ ": angle axis and each groove perpendicular to the timber axis of the steel material forms (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm ² ) of weld metal part in groove and reinforced weld metal part Welded joint of a steel material according to claim 1 or 2, characterized in that both of the weld metal portion and the reinforcing overlay weld metal portion continuous with the weld metal portion is formed by welding a metal of first welding bead . A method for forming a welded joint of steel materials in which a pair of steel materials having a groove in at least one steel material are butted together in the material axis direction, and the pair of steel materials are joined by butt welding, Tensile strength is 780N / mm for both ² Using the above, a weld metal portion for joining the pair of steel materials in the groove is formed by a weld metal having a strength lower than that of the pair of steel materials, and a weld having a strength lower than that of the pair of steel materials. By reinforcing the metal outside the groove so as to be continuous with the weld metal part, a reinforcement weld metal part for joining the pair of steel materials outside the groove is formed, and the reinforcement weld metal At the time of formation of the portion, the reinforcing weld metal portions are in contact with each other at a point on the extension of the groove surface of the groove, and the length in the axis direction of the steel material and the direction perpendicular to the axis direction of the steel material Ratio to length is 3 ^1/2 A method for forming a welded joint of steel, characterized in that it is formed into a substantially elliptical shape that envelops two similar elliptical arcs that are 1 and satisfies the following conditions.

t: Steel plate thickness (mm)
  a: Additional height of reinforcement weld metal part (mm)
  l: Length (mm) from the open end of the steel material with a groove to the toe of the reinforced metal part
  θ: Angle between the axis perpendicular to the steel axis and the groove (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm) of weld metal part in groove and reinforced weld metal part ² ) The groove is provided on both opposing surfaces of the steel material, the weld metal portion is formed in each groove, and the reinforcement weld metal portion is formed outside each groove, and the reinforcement weld is formed. 5. The method for forming a welded joint portion of steel according to claim 4, wherein at the time of forming the metal portion, any of the reinforcing welded metal portions is formed into a shape having a shape satisfying the following condition.

d ′, d ”: groove depth of each groove (mm)
  a ′, a ”: Extra height of each welded weld metal (mm)
  l ′, l ″: Length from the open end of each groove in the steel material having a groove to the toe of each reinforcing weld metal part corresponding to the groove (mm)
  θ ′, θ ″: Angle between each axis and the axis perpendicular to the steel axis (°)
_b σ _y : Yield stress of steel (N / mm ² )
_w σ _y : Yield stress (N / mm) of weld metal part in groove and reinforced weld metal part ² )   6. The method for forming a welded joint part of steel according to claim 4 or 5, wherein both the weld metal part and the reinforcing weld metal part continuous to the weld metal part are formed by one weld bead.

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