JP7234639B2 - Flanged plate-wound laser-welded steel pipe and method for producing plate-wound laser-welded steel pipe with flange - Google Patents

Description

TECHNICAL FIELD The present invention relates to a flanged plate-wound laser-welded steel pipe and a method for manufacturing a flanged plate-wound laser-welded steel pipe.

For the purpose of reducing fuel consumption by reducing the weight of automobiles, thereby reducing _CO2 emissions, or improving collision safety for passenger protection, it is desired to reduce the wall thickness and increase the strength of vehicle body structural members. In order to meet this need, parts made by forming steel pipes into predetermined shapes using the hydroforming method have begun to be used. In the hydroforming method (hydraulic tube expansion molding method), a blank pipe is placed inside a split mold whose internal shape is the final product shape, and liquid is introduced into the blank pipe from the end of the blank pipe to apply internal pressure, and both pipes This is a method in which a compressive load is applied in the direction of the tube axis from the end using a cylinder for pressing, and the tube is pressed into the final shape.

By applying the hydroforming method to metal pipes and making them into prescribed parts, it is possible to reduce the weight of parts by reducing the number of parts, and to integrally form and improve the precision of parts with complex shapes. As a result, the weight and cost of automobiles can be reduced. becomes possible.

By the way, automobile parts are generally manufactured by press-molding metal plates and joining press-molded products together by spot welding or mash seam welding. The press-formed products are provided with a flange portion for welding together the press-formed products. For this reason, automobile parts manufactured from press-formed products have overlapping flange portions. When joining such an automobile part to another automobile part, the parts are welded or fastened together using this flange portion.

On the other hand, since parts manufactured by the hydroforming method (hereinafter referred to as hydroforming parts) are made of metal pipes, they do not originally have a flange portion for welding. For this reason, conventional welding joining between parts using flange portions cannot be applied to hydroformed parts. Therefore, in order to apply a hydroformed part to an automobile part, it was necessary to join a flange member to the hydroformed part, and a new facility for joining the hydroformed part and the flange member was also required. rice field.

In order to solve such a problem, Patent Document 1 discloses a method of forming a steel pipe by forming a steel plate into a tubular shape and then welding it, in which the ends of the steel pipe are formed so as to overlap each other, and then overlap. A method of manufacturing a steel pipe with a flange, in which the steel pipe portion is formed by joining the parts by laser welding, and then the unwelded portion at the end of the steel plate superimposed on the outer peripheral side is raised by bending to form the flange portion. is described.

However, in the method for manufacturing a flanged steel pipe described in Patent Document 1, as the strength of the steel plate increases, it is becoming difficult to form only the flange portion by bending while maintaining the shape of the steel pipe portion.
In addition, in the flanged steel pipe obtained by the manufacturing method described in Patent Document 1, the flange portion is formed by bending after forming the steel pipe portion. It may interfere with the hydroforming process.

As another example of a method for manufacturing a flanged steel pipe, a steel pipe is set between upper and lower dies and heated by electric current, and then high-pressure air is supplied into the steel pipe while the space between the upper and lower dies is narrowed. By doing so, a part of the steel pipe bulges into the gap between the upper and lower molds, and then the upper and lower molds are further brought to the bottom dead center, and the bulging part is crushed by the upper and lower molds to form a flange. A method of manufacturing a flanged steel pipe is known in which the material is formed into a shape, and the material is quenched by water-cooling the mold to increase the strength of the material. However, since the flange portion formed by this method is formed by expanding a portion of the steel pipe and then crushing it with upper and lower molds, the flange portion is formed by partially overlapping the steel pipe. Therefore, the thickness of the flange portion is about twice the thickness of the steel pipe. This defeats the purpose of weight reduction.

JP 2005-279684 A

The present invention has been made in view of the above circumstances, and has a flanged sheet-wrapped laser welded steel pipe in which the plastic strain in the vicinity of the flange is reduced, the weight is reduced, and the joint strength of the flange is excellent, and its manufacture. The object is to provide a method.

In order to solve the above problems, the present invention employs the following configuration.
[1] A steel pipe portion formed by forming a steel plate into a tubular shape and having a laser-welded portion extending along the pipe axis direction;
A flanged steel pipe that is a blank pipe used for manufacturing parts by a hydroforming method, comprising a flange portion that protrudes from the outer peripheral surface of the steel pipe portion and extends along the laser welded portion,
The flange portion is a part of the steel plate formed by bending one end of the steel plate forming the steel pipe portion along the pipe axis direction, and is integrated with the steel pipe portion via the bent portion. cage,
The laser welded portion is a fillet welded portion formed between the other end of the steel plate and the bent portion. A plate wound laser welded steel pipe with a flange, characterized in that it is formed across .
[2] A steel pipe portion formed by forming a steel plate into a tubular shape and having a laser-welded portion extending along the pipe axis direction;
A flanged steel pipe that is a blank pipe used for manufacturing parts by a hydroforming method, comprising two or more mutually spaced flange portions that protrude from the outer peripheral surface of the steel pipe portion and extend along the laser welded portion. There is
Each of the two or more flange portions is a portion of the steel plate formed by bending a part of one end of the steel plate forming the steel pipe portion along the pipe axis direction. It is integrated with the steel pipe part,
The laser welded portion at the location where the flange portion is provided is a fillet welded portion formed between the other end of the steel plate and the bent portion, and the weld metal of the fillet welded portion is the steel pipe It is formed over the entire thickness direction of the part,
The laser welded portion at the location where the flange portion is not provided is a butt welded portion formed between the other end and the one end of the steel plate, and the weld metal of the butt welded portion is the steel pipe portion. A plate-wrapped laser-welded steel pipe with a flange, characterized by being formed over the entire thickness direction.
[ 3 ] The plate-wrapped laser-welded steel pipe with a flange according to [1] or [2], wherein the laser-welded portion extends along the axial direction of the pipe without welding defects.
[ 4 ] The fillet weld includes a first weld toe on the other end side of the steel plate and a second weld toe on the bent side,
The angle at the first weld toe is 70° or less,
The flanged, plate-wound, laser-welded steel pipe according to any one of [1] to [3], wherein the second weld toe has an angle of 70° or less.
[ 5 ] The Vickers hardness of the weld metal of the fillet weld is 1.2 times or more higher than the Vickers hardness of the steel plate, according to any one of [1] to [4]. Sheet wound laser welded steel pipe with flange.
[ 6 ] The Mn amount in the weld metal of the fillet weld is 95% or more with respect to the Mn amount in the steel plate, according to any one of [1] to [5]. Sheet wound laser welded steel pipe with flange.
[ 7 ] A method for manufacturing a plate-wrapped laser-welded steel pipe with a flange, which is a base pipe used for manufacturing parts by the hydroforming method, comprising:
When forming a steel plate into a tubular shape, a steel plate having a flange portion formed by bending one end along the plate longitudinal direction is oriented so that the longitudinal direction of the plate is the direction of the pipe axis, and the flange portion protrudes to the outer peripheral side. or a forming step of forming a flange portion by bending one end of the steel plate to the outer peripheral side along the longitudinal direction of the plate while forming the steel plate into a tubular shape;
A welding step of butting and laser-welding the bent portion provided on the steel plate and the other end of the steel plate when forming the flange portion;
with
In the welding step, welding is performed so as to form a weld metal over the entire thickness direction of the steel plate .
[ 8 ] The method for producing a plate-wrapped laser- welded steel pipe with a flange according to [7], wherein welding is performed while a welding filler material is being supplied in the laser welding.
[ 9 ] The method for producing a flanged plate wound laser welded steel pipe according to [8] , wherein the welding filler material is a welding wire having a diameter of 0.6 to 1.6 mm.
[ 10 ] In the laser welding , the beam diameter at the focused spot is 0.4 to 1 mm, the incident angle of the laser is 30 to 60° with respect to the flange portion , and the direction of the tube axis is 75 to 105 ° .

The flange portion of the plate-wrapped laser-welded steel pipe with a flange of the present invention is a part of a steel plate formed by bending one end of the steel plate forming the steel pipe portion, and is integrated with the steel pipe portion via the bent portion. Therefore, the thickness of the flange portion is the same as the thickness of the steel pipe portion. As a result, the flanged steel pipe of the present invention can be made lighter than conventional products in which the wall thickness of the flange portion is twice the wall thickness of the steel pipe.
In addition, since the flange part is integrated with the steel pipe part through the bent part, the joint strength of the flange part to the steel pipe part is higher than that of conventional products in which the flange part is attached to the steel pipe part by welding. can do.
Furthermore, the laser welded portion of the flanged sheet-wrapped laser welded steel pipe of the present invention is a fillet welded portion in which the other end of the steel plate is butted against the bent portion and welded, so the heat input during welding reduces the dislocation density. and the plastic strain at the bend is reduced. The plastic strain of the bent portion can be made smaller than the plastic strain of the conventional product in which the flange portion is formed by bending the formed steel pipe portion.
As described above, the plate-wrapped laser-welded steel pipe with flanges of the present invention has less plastic strain than conventional products, achieves weight reduction, and has excellent joint strength at the flange portion.

Furthermore, according to the plate-wrapped laser welded steel pipe with a flange of the present invention, the steel plate forming the steel pipe portion and the flange portion are integrated, and the other end of the steel plate is butted against the bent portion that is the base end of the flange portion. Therefore, when stress is applied to the flange in the direction in which it protrudes, the equivalent plastic strain that occurs near the welded portion causes the flange to be formed by bending after the steel pipe is formed by lap welding. Compared to the equivalent plastic strain of conventional products, it is greatly reduced.

In addition, in the flanged sheet-wrapped laser-welded steel pipe of the present invention, since the welded portion is a laser-welded portion, the weld metal can be formed in the entire thickness direction of the steel pipe portion, and the joint strength of the welded portion can be increased. can. As a result, a high-pressure fluid can be introduced in the hydroforming process using the flanged steel pipe of the present invention as a raw material, and the workability of the hydroforming process can be further enhanced.

In addition, in the flanged plate-wrapped laser-welded steel pipe of the present invention, since the angles of the first weld toe and the second weld toe of the fillet weld are each 70° or less, the angle between the flange and the steel pipe is Stress concentration can be reduced even when a tensile stress is applied in the steel pipe portion or a tensile stress is applied in the circumferential direction of the steel pipe portion.

In addition, since the laser-welded portion of the flanged sheet-wrapped laser-welded steel pipe of the present invention has a weld metal with a Vickers hardness that is 1.2 times or more higher than the Vickers hardness of the steel plate, the joint strength of the laser-welded portion is further increased. Furthermore, the processability of hydroforming can be further improved.

In addition, since the laser-welded portion of the plate-wrapped laser-welded steel pipe with flange of the present invention has a weld metal containing 95% or more of Mn relative to the amount of Mn in the steel plate, it is possible to suppress a decrease in the strength of the weld metal.

Next, the method for manufacturing a plate-wrapped laser welded steel pipe with a flange according to the present invention includes a forming step of forming a flanged steel plate having a flange portion into a tubular shape, and Since the welding step of butting and welding the other ends of the two is provided, there is no need to attach the flange portion after the welding step as in the conventional method, and the process can be simplified. Moreover, since the fillet weld is formed in the bent portion, it is possible to reduce the plastic strain remaining in the bent portion when the flange portion is formed.

In addition, according to the method for manufacturing a plate-wrapped laser-welded steel pipe with a flange according to the present invention, since the welding is performed by a laser welding method, the weld metal can be formed in the entire thickness direction of the steel pipe portion, and the laser-welded portion can be joined. Strength can be increased. As a result, a high-pressure fluid can be introduced in the hydroforming process using the flanged steel pipe of the present invention as a raw material, and the workability of the hydroforming process can be further enhanced.

1A is a schematic side view showing an example of a flanged steel pipe according to an embodiment of the present invention; FIG. 1B is a schematic plan view of the flanged steel pipe shown in FIG. 1A; FIG. 1C is a view showing the flanged steel pipe shown in FIG. 1A, and is a schematic cross-sectional view taken along line a-a' in FIG. 1A. FIG. 2A is a schematic side view showing another example of a flanged steel pipe that is an embodiment of the present invention; 2B is a schematic plan view of the flanged steel pipe shown in FIG. 2A; FIG. 2C is a view showing the flanged steel pipe shown in FIG. 2A, and is a schematic cross-sectional view taken along line b-b' in FIG. 2A. 2D is a view showing the flanged steel pipe shown in FIG. 2A, and is a schematic cross-sectional view taken along line c-c' of FIG. 2A. FIG. 3 is a schematic cross-sectional view of a main part of the flanged steel pipe according to the embodiment of the present invention. FIG. 4 is a process schematic diagram explaining a method for manufacturing a flanged steel pipe according to an embodiment of the present invention. FIG. 5 is a schematic perspective view illustrating a welding process in the method for manufacturing a flanged steel pipe according to an embodiment of the present invention; FIG. 6 is a process schematic diagram explaining a manufacturing method of a flanged steel pipe of a comparative example. FIG. 7 is a schematic cross-sectional view of a main part of a flanged steel pipe of a comparative example. FIG. 8 is a contour diagram showing equivalent stress and equivalent plastic strain when stress is applied to the flange portion of the flanged steel pipe of the example. FIG. 9 is a contour diagram showing the equivalent stress and equivalent plastic strain when stress is applied to the flange portion of the flanged steel pipe of the comparative example. FIG. 10 is a graph showing the relationship between the angle and the equivalent stress at the first weld toe; FIG. 11 is a process schematic diagram explaining another example of the method for manufacturing a flanged steel pipe according to an embodiment of the present invention.

Hereinafter, a plate-wrapped laser-welded steel pipe with a flange according to the present embodiment and a method for manufacturing the same will be described.
A plate-wrapped laser-welded steel pipe with a flange (hereinafter referred to as a flanged steel pipe) of the present embodiment comprises a steel pipe formed into a tubular shape and having a laser-welded portion extending along the pipe axial direction; one or two or more flange portions protruding from the outer peripheral surface of the steel pipe portion and extending along the laser welded portion, and the flange portion is formed by bending one end of a steel plate forming the steel pipe portion along the pipe axial direction. A portion of a formed steel plate that is integrated with a steel pipe section through a bend, and a laser weld is a fillet weld formed between the other end of the steel plate and the bend. . The bent portion is a flanged steel pipe formed by subjecting a part of the steel plate to plastic working before welding.

As a result of the inventor's intensive research on the present invention, the following findings were obtained.
(1) When attaching a flange to a steel pipe, fillet welding is superior in consideration of subsequent processing by hydroforming and joining of the flange and other members.
(2) Fillet welding requires proper conditions such as the angle between the flange portion and the weld metal, and between the steel pipe portion and the weld metal, such as the amount of weld metal.
(3) In addition, when the steel pipe member is integrally molded as it is to form the flange portion, it is necessary to remove strain due to plastic working after molding. Desirably, it is necessary to heat-treat at a predetermined temperature.
In the flanged steel pipe of the present invention, a fillet weld is formed between the flange portion and the steel pipe portion. In addition, the flange portion is a part of the steel plate that is formed by bending one end of the steel plate forming the steel pipe portion along the pipe axis direction. Density is reduced and plastic strain is also reduced. As a result, even if it is processed by hydroforming, there is no risk of damage to the laser welded part, and even if another member is joined to the flange, it has excellent characteristics such as fatigue resistance. become a thing.

Also, if there is a defect in the weld metal (so-called weld defect), for example, an undercut or the like will occur, and a predetermined strength cannot be obtained, and the weld will break in the vicinity of the weld metal. Therefore, it is necessary to eliminate the weld defect.
In addition, by setting the angle of the weld toe of the fillet weld to 70° or less, the equivalent strain concentrated on the toe can be reduced. Desirably, the angle is 60° or less.
Furthermore, in order to suppress breakage from the laser welded portion, generally in welding, the hardness of the weld metal is made higher than the strength of the base material. In the present invention, since the Vickers hardness of the weld metal is increased to about 1.2 times that of the steel plate (steel pipe portion) by laser welding, breakage from the weld metal can be suppressed.
Also, in the weld metal formed by laser welding, the content of Mn, which has a high affinity for oxygen, tends to decrease. If the Mn content is low, the strength of the weld metal is lowered, so it is necessary to make the Mn content 95% or more of the steel plate. In order to reduce welding defects and suppress a decrease in Mn yield, it is preferable to perform welding while adding a welding filler material during laser welding.

The steel plate forming the steel pipe portion is preferably made of, for example, a high-strength steel plate having a tensile strength of 980 MPa or more, 1180 MPa or more, or 1470 MPa or more. The steel plate is preferably so-called DP steel (DP: Dual Phase) or TRIP steel (TRIP: Transformation Induced Plasticity). However, since TRIP steel has a high Si content, joining by resistance welding is difficult, and joining by laser welding is preferable.

Further, the thickness t of the steel plate (the thickness of the steel pipe portion and the thickness of the flange portion) is preferably 1.4 mm or less, for example. Moreover, the ratio t/D between the thickness of the steel plate, that is, the thickness t (mm) of the steel pipe portion and the outer diameter D (mm) of the steel pipe portion may be 1.8% or less. The example of the steel plate described above is merely an example, and other steel plates may be used.

In addition, the laser welded portion has a weld metal formed between the other end of the steel plate and the bent portion, and the Vickers hardness of the weld metal is 1.2 times or more higher than the Vickers hardness of the steel plate. preferable. The Vickers hardness is measured with a load of 10 g, and the Vickers hardness is measured on the cross section of the steel pipe portion and the weld metal perpendicular to the pipe axis direction.

The bend is preferably included in the heat affected zone of the laser weld. That is, it is preferable that heat input during welding is applied to the bent portion.

The flanged steel pipe of the present embodiment may be used as an automobile part as it is, or may be used as a base pipe for hydroforming. A flanged steel pipe processed into a predetermined shape by the hydroforming method is used as an automobile part.

Next, in the method of manufacturing a flanged steel pipe according to the present embodiment, when forming a steel plate into a tubular shape, a steel plate having a flange portion formed by bending one end along the longitudinal direction of the steel plate is bent along the longitudinal direction of the steel pipe. Alternatively, a steel plate is formed into a tubular shape and one end of the steel plate is bent to the outer peripheral side along the longitudinal direction of the steel plate to form the flange portion. and a welding step of butting and laser-welding the bent portion provided in the steel plate and the other end of the steel plate when forming the flange portion.

As the flanged steel plate, it is preferable to use a steel plate in which a flange portion is formed by bending one end of the steel plate in advance along the longitudinal direction of the plate. Alternatively, it is preferable to form the flange portion by bending one end of the steel plate toward the outer peripheral side along the longitudinal direction of the steel plate when forming the steel pipe.

In the forming process, it is preferable to form the steel sheet into a tubular shape by press forming, but the forming process may use other forming methods other than the press forming method.

As described above, it is effective to supply a welding filler material other than the base metal in order to suppress weld defects and a decrease in the Mn content of the weld metal.
Welding wire is generally used as the welding filler metal, but plates and powder are also acceptable. If a welding wire is used, the diameter of the wire is preferably 0.6-1.6 mm. If it is 0.6 mm or less, the amount of deposited metal is small, and if it exceeds 1.6 mm, irradiation of the base material with the laser is remarkably hindered. Desirably, the diameter of the wire is 0.9-1.2 mm.

In the laser welding method, the beam diameter at the focused spot should be 0.4 to 1 mm. If the thickness is less than 0.4 mm, the entire weld cannot be melted. Moreover, when the beam diameter exceeds 1 mm, sufficient power density cannot be obtained.

The reason why the incident angle of the laser is set to 30 to 60° with respect to the flange portion is to stably focus the laser beam on the butt portion to be welded. Moreover, it is preferable to irradiate from a direction of 75 to 105° with respect to the tube axis, and it is most suitable to irradiate from a direction of 90°. Irradiation outside the range of 75 to 105° requires a large amount of energy to form a beam hole.

In the welding process, the laser welding may be performed while purging at least the laser irradiated portion with an inert gas.

Hereinafter, a flanged steel pipe and a method for manufacturing the same will be described with reference to the drawings.
FIG. 1A shows a schematic side view of an example of the flanged steel pipe of this embodiment. FIG. 1B shows a schematic plan view of the flanged steel pipe. Further, FIG. 1C shows a schematic cross-sectional view taken along line aa' of FIG. 1A.

A flanged steel pipe 1 shown in FIGS. 1A, 1B and 1C includes a steel pipe portion 2 and one flange portion 3 . The steel pipe portion 2 is formed by forming a steel plate into a tubular shape. A laser welded portion 4 is formed in the steel pipe portion 2 . The laser welded portion 4 extends along the pipe axis direction of the steel pipe portion 2 . Moreover, the flange portion 3 protrudes from the outer peripheral surface 2A of the steel pipe portion 2 and extends along the laser welded portion 4 . The flange portion 3 of the flanged steel pipe 1 shown in FIGS. 1A and 1B is one continuous flange portion extending along the axial direction of the steel pipe portion 2 .

The steel pipe portion 2 is formed by cutting out a rectangular steel plate in plan view, bending one end in the width direction of the steel plate to form a flange portion, and bending the steel plate with the flange so that the longitudinal direction of the steel plate is the pipe axis direction. In addition, the steel pipe is formed into a tubular shape so that the flange portion protrudes toward the outer peripheral side of the steel pipe, and the steel pipe is welded.

The flange portion 3 is a portion of a steel plate formed by bending one end 2a of the steel plate forming the steel pipe portion 2 along the pipe axis direction. The flange portion 3 is integrated with the steel pipe portion 2 via the bent portion 2b. In other words, the flange portion 3 is formed by protruding a portion of the steel pipe portion 2 from the outer peripheral surface of the steel pipe portion 2 . In addition, "integrated" means that the steel pipe portion 2 and the flange portion 3 are not joined by means such as welding.

The steel pipe portion 2 and the flange portion 3 are originally made of the same steel plate. The steel plate that is the raw material of the steel pipe portion 2 and the flange portion 3 is preferably a high-strength steel plate having a tensile strength of 980 MPa or more, 1180 MPa or more, or 1470 MPa or more. Also, the steel plate is preferably so-called DP steel or TRIP steel. Further, the thickness t of the steel plate (the thickness of the steel pipe portion and the thickness of the flange portion) is preferably 1.4 mm or less, for example. Moreover, the ratio t/D between the thickness of the steel plate, that is, the thickness t (mm) of the steel pipe portion 2 and the outer diameter D (mm) of the steel pipe portion 2 may be 1.8% or less.

Next, the laser welded portion 4 will be described with reference to FIGS. 1A to 1C and 3. FIG. FIG. 3 is an enlarged schematic cross-sectional view of the laser welded portion 4. As shown in FIG. As shown in these figures, the laser-welded portion 4 is a fillet-welded portion in which the other end 2c of the steel plate forming the steel pipe portion 2 is abutted and welded to the bent portion 2b. The laser welded portion 4 is a welded portion formed by a laser welding method. A weld metal 4 a is formed in the laser welded portion 4 . The weld metal 4a is formed between the other end 2c of the steel plate forming the steel pipe portion 2 and the bent portion 2b. The weld metal 4a is exposed from the outer peripheral surface 2A and the inner peripheral surface 2B of the steel pipe portion 2, respectively. That is, the weld metal 4 a is formed over the entire thickness direction of the steel pipe portion 2 . A heat affected zone 4b exists around the weld metal 4a. In particular, the heat-affected zone 4b on the bent portion 2b side extends to a range close to the outer peripheral surface 2A of the steel pipe portion 2 .

The laser welded portion 4 includes a first weld toe portion A on the other end portion 2c side of the steel plate and a second weld toe portion B on the bent portion 2b side. The angle θ at the first weld toe A is 70° or less. Also, the angle ψ at the second weld toe portion B is set to 70° or less. The angles θ and ψ are more preferably 60° or less. By setting the angles θ and ψ to be 70° or less, even when a tensile stress is applied between the flange portion 3 and the steel pipe portion 2 or a tensile stress in the circumferential direction of the steel pipe portion 2, each Stress concentration at the weld toes A, B can be reduced. The angle θ at the first weld toe A is the angle formed between the surface of the steel pipe portion 2 and the laser welded portion 4, as shown in FIG. It is the angle between the surface of 3 and the laser welded portion 4 . The projecting direction of the flange portion 3 substantially coincides with the radial direction of the steel pipe portion 2 . In other words, the projecting direction of the flange portion 3 is approximately 90° with respect to a tangential line that is virtually provided on the surface of the steel pipe portion 2 . Therefore, the sum of the angle θ at the first weld toe A and the angle ψ at the second weld toe B is ideally approximately 90°.

The Vickers hardness of the weld metal 4 a is preferably 1.2 times or more higher than the Vickers hardness of the steel plate forming the steel pipe portion 2 . Thereby, the joint strength of the laser welded portion 4 is improved. It is preferably 1.4 times or more.

In addition, the inner diameter of the steel pipe portion 4 is substantially uniform over the entire circumference of the steel pipe portion 4 . This is because the laser welded portion 4 of the present embodiment is a fillet welded portion, not a lap weld as in the conventional product, and there is no overlapping portion between steel plates. Therefore, the flanged steel pipe of the present embodiment has better workability in the hydroforming method than the conventional product formed into a tubular shape by lap welding.

Next, another example of the flanged steel pipe of this embodiment will be described with reference to FIGS. 2A to 2D. FIG. 2A shows a schematic side view of another example of the flanged steel pipe of this embodiment. FIG. 2B shows a schematic plan view of the flanged steel pipe. 2C shows a schematic cross-sectional view taken along line b-b' in FIG. 2A, and FIG. 2D shows a schematic cross-sectional view taken along line c-c' in FIG. 2A.

The difference between the flanged steel pipe 11 shown in FIGS. 2A to 2D and the flanged steel pipe 1 shown in FIGS. 1A to 1C is the number of flange portions, and the flanged steel pipe 11 shown in FIGS. 2A to 2D has a plurality of flange portions. 13. Specifically, it has four flange portions 13A to 13D. The following description will focus on the differences in the flange portions.

The flanged steel pipe 11 shown in FIGS. 2A-2D comprises a steel pipe portion 12 and four flange portions 13A-13D. The steel pipe portion 12 is formed by forming a steel plate into a tubular shape. A laser welded portion 14 is formed in the steel pipe portion 12 . The laser welded portion 14 extends along the pipe axis direction of the steel pipe portion 2 . The flange portions 13A to 13D protrude from the outer peripheral surface 12A of the steel pipe portion 12 and extend along the laser welded portion . Each of the flange portions 13A to 13D of the flanged steel pipe 11 extends along the pipe axis direction of the steel pipe portion 2. As shown in FIG. Moreover, each of the flange portions 13A to 13D is not continuous and is an independent separate flange portion.

The steel pipe portion 12 is obtained by cutting out a rectangular steel plate in plan view, providing a plurality of notch portions at one end in the width direction of the steel plate, and bending a portion where the notch portion is not provided to form a plurality of flange portions. Then, the steel plate with the flange is formed into a tubular shape so that the longitudinal direction of the plate is the direction of the pipe axis and the direction of protrusion of the flange portion is directed toward the outer peripheral side of the steel pipe, and laser welding is performed. .

Each of the flange portions 13A to 13D is a portion of a steel plate formed by bending one end 12a of the steel plate forming the steel pipe portion 12 along the pipe axis direction. The flange portions 13A to 13D are integrated with the steel pipe portion 12 via the bent portion 12b.

FIG. 2C shows a cross-sectional view of the steel pipe portion 12 at the location where the flange portion 13B is provided. This cross-sectional shape is the same as the cross-sectional shape shown in FIG. 1C. That is, the configuration of the flange portions 13A to 13D is substantially the same as the configuration of the flange portion 3 of the flanged steel pipe 1 shown in FIGS. 1A to 1C.

Next, the laser welded portion 14 will be described with reference to FIGS. 2A to 2D. As shown in FIG. 2C, the laser welded portion 14 at the location where the flange portion is provided is a fillet welded portion in which the other end 12c of the steel plate forming the steel pipe portion 12 is butted and welded to the bent portion 12b. . The cross-sectional shape of the laser welded portion 14 at the location where the flange portion is provided is the same as the cross-sectional shape shown in FIG. 1C or FIG.

In addition, as shown in FIG. 2D, the laser welded portion 14 at the location where the flange portion is not provided is a welded portion in which the other end 12c of the steel plate forming the steel pipe portion 12 is butted against the end portion 12d of the steel plate and welded. is. The end portion 12d of the steel plate is the end portion of the steel plate at the location where the notch portion is provided in the steel pipe portion before forming.

The laser welded portion 14 is a welded portion formed by a laser welding method. A weld metal is formed on the laser-welded portion 14 in the same manner as the laser-welded portion 4 shown in FIG. The weld metal is exposed from the outer peripheral surface 12A and the inner peripheral surface 12B of the steel pipe portion 12, respectively, and is formed over the entire thickness direction of the steel pipe portion 12. As shown in FIG. The Vickers hardness of the weld metal is preferably 1.2 times or more higher than the Vickers hardness of the steel plate forming the steel pipe portion 12 .

Next, a method for manufacturing a flanged steel pipe according to this embodiment will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view for explaining a method for manufacturing a flanged steel pipe. 1A to 1C, the flanged steel pipe 11 shown in FIGS. 2A to 2D is also explained below. It can be manufactured by a method.

The method for manufacturing a flanged steel pipe according to the present embodiment includes a forming step of forming a steel plate having a flange portion into a tubular shape, and a welding step of performing laser welding. In addition, before the forming step, a pretreatment step of bending the steel plate to form a flange portion may be performed.

In the pretreatment step, as shown in FIG. 4, a steel plate 22 formed into a rectangular shape in plan view is prepared. Next, the flange portion 3 is formed by bending one end 2a of the steel plate in the width direction along the longitudinal direction of the plate. Thus, the flanged steel plate 32 is manufactured.

Next, in the forming step, as shown in FIG. 4, the flanged steel plate 32 is formed into a tubular shape so that the longitudinal direction of the flanged steel plate 32 is the direction of the pipe axis and the projecting direction of the flange portion 3 is directed toward the outer peripheral side of the steel pipe. to mold. Although there is no particular limitation on the method for forming the flanged steel plate 32 into a tubular shape, it is preferable to use a press forming method. That is, the flanged steel plate 32 may be formed into a tubular shape by gradually bending along the plate width direction.

Next, in the welding process, as shown in FIG. 4, the other end 2c of the flanged steel plate 32 formed into a tubular shape is butted against the bent portion 2b provided along with the formation of the flange portion 3, and a laser beam is applied to the butted portion. By irradiating L, a laser welded portion 4 is formed between the other end 2c and the bent portion 2b. Thus, the steel pipe portion 2 is formed. As shown in FIG. 5, the laser beam L is applied while relatively moving along the axial direction (longitudinal direction) of the tubular flanged steel plate 32 . Thereby, a laser welded portion 4 is formed along the pipe axis direction.

It is preferable to blow an inert gas onto the irradiated portion of the laser beam L. As shown in FIG. The inert gas may be, for example, a mixed gas of Ar (argon) and CO ₂ or nitrogen gas. Although the steel is partially heated at the irradiated portion of the laser beam L and easily oxidized, the oxidation of the steel is prevented by blowing the inert gas. In the laser welding method, since the steel heating area is relatively narrow, the oxidation of the welded portion can be sufficiently suppressed by blowing inert gas.

Also, in order to suppress welding defects and a decrease in the Mn content of the weld metal, welding may be performed while supplying a welding filler material. When a welding wire is used as the welding filler material, the wire preferably has a diameter of 0.6 to 1.6 mm. In the laser welding method, the beam diameter at the focused spot is preferably 0.4 to 1 mm. Further, the incident angle of the laser beam may be 30 to 60° with respect to the flange portion 3. The angle of incidence of the laser beam with respect to the tube axis is preferably from a direction in the range of 75 to 105°.

In addition, although the bent portion 2b is in a state in which plastic strain is introduced by undergoing the forming process, the bent portion 2b is included in the heat-affected zone of the laser welded portion 4 due to the heat input during laser welding, and the plasticity is reduced. Strain is relaxed.

Moreover, FIG. 11 shows another example of the method for manufacturing the flanged steel pipe of the present embodiment. A steel plate 20 is prepared as shown in FIG. 11(a), then a portion 20a of the steel plate 20 is bent as shown in FIG. 11(b), and then as shown in FIG. 11(c). Then, one end of the steel plate 20 in the width direction is bent to form the flange portion 23 .

Next, as shown in FIG. 11(d), the other end 20b in the width direction of the steel plate 20 is brought into contact with the bent portion 20c that has been bent, and finally, as shown in FIG. 11(e), , forming a laser weld 24 at the abutment. As described above, in the present embodiment, while forming the steel plate into a tubular shape, one end of the steel plate is bent toward the outer peripheral side along the longitudinal direction to form the flange portion, and the flange portion is provided on the steel plate when forming the flange portion. A flanged steel pipe may be produced by butting and laser welding the bent portion and the other end of the steel plate.

As described above, in the flanged steel pipes 1 and 11 of the present embodiment, the flange portion 3 is a part of the steel plate formed by bending one end of the steel plate forming the steel pipe portions 2 and 12. Since it is integrated with the steel pipe portions 2 and 12 via 2b, the thickness of the flange portion 3 is the same as the thickness of the steel pipe portions 2 and 12. As shown in FIG. As a result, the flanged steel pipes 1 and 11 of the present embodiment can be made lighter than conventional products in which the wall thickness of the flange portion is twice the wall thickness of the steel pipe.

In addition, since the flange portion 3 is integrated with the steel pipe portions 2 and 12 via the bent portion 2b, compared to conventional products in which the flange portion is attached to the steel pipe portion by fillet welding, the steel pipe portion 2 , 12 can be increased.

Furthermore, the laser welded portions 4 and 14 of the flanged steel pipes 1 and 11 of the present embodiment are fillet welded portions in which the other ends 2c and 12c of the steel plate are butted against the bent portion 2b and welded. The dislocation density is reduced by the heat input, and the plastic strain of the bent portion 2b is reduced. The plastic strain of the bent portion 2b can be made smaller than the plastic strain of the conventional product in which the flange portion 3 is formed by bending the steel pipe portions 2 and 12 after forming.

As described above, the flanged steel pipes 1 and 11 of the present embodiment have reduced plastic strain, achieve weight reduction, and have excellent joint strength of the flange portion 3 as compared with conventional products.

Furthermore, according to the flanged steel pipes 1 and 11 of the present embodiment, the steel plates forming the steel pipe portions 2 and 12 and the flange portion 3 are integrated with each other, and the bent portion 2b serving as the base end of the flange portion 3 is provided with a steel plate. Since the other ends 2c and 12c are butted against each other, the equivalent plastic strain generated in the vicinity of the laser welded portions 4 and 14 when stress is applied to the flange portion 3 in the direction of its protrusion is the same as the lap weld. Therefore, the equivalent plastic strain is greatly reduced compared to the conventional product in which the flange portion 3 is formed by bending after the steel pipe portion 2 is formed.

In addition, since the flanged steel pipes 1 and 11 of the present embodiment have the laser-welded portions 4 and 14, the weld metal 4a can be formed in the entire thickness direction of the steel pipe portions 2 and 12, and laser welding can be performed. The joint strength of the parts 4 and 14 can be increased. As a result, high-pressure fluid can be introduced in the hydroforming process using the flanged steel pipes 1 and 11 as raw materials, and the workability of the hydroforming process can be further enhanced.

In addition, in the flanged steel pipes 1 and 11 of the present embodiment, the angles θ and ψ of the first weld toe A and the second weld toe B of the fillet weld are 70° or less, respectively. Even when a tensile stress is applied between the steel pipe portion 3 and the steel pipe portion 2 or a tensile stress is applied in the circumferential direction of the steel pipe portion 2, stress concentration can be reduced.

In addition, since the laser-welded parts 4, 14 of the flanged steel pipes 1, 11 of the present embodiment have the weld metal 4a whose Vickers hardness is 1.2 times or more higher than the Vickers hardness of the steel plate, the laser-welded parts 4, 14 The bonding strength can be further increased, and the workability of hydroforming can be further increased.

In addition, since the laser welded portions 4, 14 of the flanged steel pipes 1, 11 of the present embodiment have the weld metal 4a containing 95% or more of Mn with respect to the Mn amount in the steel plate, the strength of the weld metal 4a is reduced. can be suppressed.

In addition, since the bent portions 2b of the flanged steel pipes 1 and 11 of the present embodiment are included in the heat affected zones 4b of the laser welded portions 4 and 14, the plastic strain is reduced. The plastic strain of the bent portion 2b is smaller than the plastic strain of the conventional product in which the flange portion is formed by bending the steel pipe portion 2 after forming. Thus, the flanged steel pipes 1 and 11 of the present embodiment can make the plastic strain of the bent portion 2b smaller than that of the conventional product.

Next, the method for manufacturing a flanged steel pipe according to the present embodiment includes a forming step of forming the flanged steel plate 22 having the flange portion 3 into a tubular shape, and a bending portion 2b provided along with the formation of the flange portion 3. Since the welding step of butting and welding the other ends 2c of the steel plates 22 is provided, there is no need to attach the flange portion after the welding step as in the conventional method, and the steps can be simplified. In addition, since the fillet welded portion is formed in the bent portion 2b, it is possible to reduce the plastic strain remaining in the bent portion 2b when forming the flange portion.

In addition, according to the method for manufacturing the flanged steel pipe of the present embodiment, the welding is performed by the laser welding method. , 14 can be increased. As a result, high-pressure fluid can be introduced in the hydroforming process using the flanged steel pipes 1 and 11 as raw materials, and the workability of the hydroforming process can be further enhanced.

In the flanged steel pipe of the present invention, the equivalent plastic strain generated in the vicinity of the welded portion when stress is applied to the flange portion in the direction of protrusion is significantly reduced compared to the conventional product. explain.

As an example, a flanged steel pipe shown in FIGS. 1A to 1C and 3 was manufactured. The steel plate used as the material was a high-strength steel plate with a tensile strength of 980 MPa. This high strength steel plate was DP steel. The plate thickness of the steel plate was 1 mm. The outer diameter of the steel pipe portion was 80 mm. The protrusion height of the flange portion from the outer peripheral surface of the steel pipe portion was 20 mm.

Laser welding uses a 6 kW class disk laser, the welding filler material uses a commercially available 100 k class microwire with a diameter of 0.9 mm, the beam diameter is 0.8 mm at the focused spot, and the laser incident angle is The angle was 45° with respect to the flange portion and 90° with respect to the tube axis direction.

Since the microwire was used as the welding filler material, the amount of Mn contained in the weld metal is When measured by Kantback analysis, it was almost the same as that of the base steel plate, and was 100% of the Mn content of the base steel plate.

Further, when the Vickers hardness of the weld metal and the Vickers hardness of the steel pipe portion were measured for the flanged steel pipe of the example, the Vickers hardness of the weld metal was 1.2 times or more higher than the Vickers hardness of the steel pipe portion. rice field.

Next, a flanged steel pipe of Comparative Example was manufactured. As shown in FIG. 6, the flanged steel pipe of the comparative example is formed by forming a steel pipe portion 62 by forming a welded portion 64 on an overlapping portion 52a of a steel plate 52 formed into a tubular shape by a laser welding method. A flange portion 63 is formed by raising the welded portion by bending. The steel plate 52 used as the raw material for the flanged steel pipe of the comparative example was the same as that of the example. FIG. 7 shows a cross-sectional schematic diagram of a welded portion 64 of a flanged steel pipe of a comparative example. In the flanged steel pipe of the comparative example shown in FIG. 7, a welded portion 64 formed by lap welding was formed in the overlapped portion 52a of the steel plates as the raw materials. Then, the end portion of the steel plate was bent by bending to form the flange portion 63 .

The equivalent stress and equivalent plastic strain in the vicinity of the welded portion when a tensile stress is applied to displace each flange portion by 1 mm in the projecting direction while the steel pipe portions of the flanged steel pipes of Examples and Comparative Examples are restrained. It was measured. FIG. 8 is a contour diagram showing the equivalent stress and equivalent plastic strain of the flanged steel pipe of the example. Further, FIG. 9 shows a contour diagram of the equivalent stress and equivalent plastic strain of the flanged steel pipe of the comparative example. FIGS. 8(a) and 9(a) are schematic diagrams of the vicinity of the flange portion and welded portion of the flanged steel pipe, respectively, and FIGS. 8(b) and 9(b) are respectively the flange portions of the flanged steel pipe. Fig. 8(c) and Fig. 9(c) are contour diagrams showing the distribution of equivalent plastic strain near the flange and the weld of a flanged steel pipe, respectively. is.

As shown in FIG. 8, in the flanged steel pipe of the example, the equivalent stress and equivalent plastic strain are concentrated in the first weld toe A, whereas in the comparative example, the It can be seen that the equivalent stress and equivalent plastic strain are concentrated in the steel pipe portion 65 . Further, as shown in Table 1, when comparing the maximum equivalent stress and the maximum equivalent plastic strain between the examples and the comparative examples, it can be seen that the examples are lower than the comparative examples. Therefore, in the flanged steel pipes of Examples, even when tensile stress is applied to the flange portion, concentration of the equivalent stress and equivalent plastic strain at a specific portion can be avoided, and the tensile stress applied to the flange portion can be avoided. It can be seen that this is an advantageous structure.

Next, the flanged steel pipes shown in FIGS. 1A to 1C and 3 were prepared by changing the angle of the first weld toe A from 10° to 80°. The structure was the same as that of the flanged steel pipe of the above example, except that the angle was changed. Then, the maximum equivalent stress at the first weld toe portion was measured when a tensile stress was applied in the circumferential direction of the steel pipe portion. The results are shown in FIG. The sum of the angle θ at the first weld toe A and the angle ψ at the second weld toe B is approximately 90°.

As shown in FIG. 10, when the angle θ of the first weld toe A is set to 10°, the maximum equivalent stress of the first weld toe A decreases, but on the other hand, the second weld toe B increases, there is a possibility that a large equivalent stress will be concentrated on the second weld toe portion B when a tensile stress is applied to the flange portion in its projecting direction. Moreover, when the angle θ of the first weld toe A is set to 80°, the maximum equivalent stress of the first weld toe A increases. From the above, it can be seen that the angles of the first weld toe A and the second weld toe B are preferably in the range of 10° to 80°.

REFERENCE SIGNS LIST 1, 11 Flanged steel pipe (plate wound laser welded steel pipe with flange) 2, 12 Steel pipe portion 2A Peripheral surface 2a, 12a One end 2b, 12b Bent portion 2c, 12c Other end 3 , 13A to 13D... flange portion, 4, 14... laser welded portion, 4a... weld metal, 22... steel plate with flange.

Claims (10)

a steel pipe portion formed by forming a steel plate into a tubular shape and having a laser welded portion extending along the pipe axis direction;
A flanged steel pipe that is a blank pipe used for manufacturing parts by a hydroforming method, comprising a flange portion that protrudes from the outer peripheral surface of the steel pipe portion and extends along the laser welded portion,
The flange portion is a part of the steel plate formed by bending one end of the steel plate forming the steel pipe portion along the pipe axis direction, and is integrated with the steel pipe portion via the bent portion. cage,
The laser welded portion is a fillet welded portion formed between the other end of the steel plate and the bent portion. A plate wound laser welded steel pipe with a flange, characterized in that it is formed across . a steel pipe portion formed by forming a steel plate into a tubular shape and having a laser welded portion extending along the pipe axis direction;
A flanged steel pipe that is a blank pipe used for manufacturing parts by a hydroforming method, comprising two or more mutually spaced flange portions that protrude from the outer peripheral surface of the steel pipe portion and extend along the laser welded portion. There is
Each of the two or more flange portions is a portion of the steel plate formed by bending a part of one end of the steel plate forming the steel pipe portion along the pipe axis direction. It is integrated with the steel pipe part,
The laser welded portion at the location where the flange portion is provided is a fillet welded portion formed between the other end of the steel plate and the bent portion, and the weld metal of the fillet welded portion is the It is formed over the entire thickness direction of the steel pipe,
The laser welded portion at the location where the flange portion is not provided is a butt welded portion formed between the other end and the one end of the steel plate, and the weld metal of the butt welded portion is the steel pipe portion. A plate-wrapped laser-welded steel pipe with a flange, characterized by being formed over the entire thickness direction . 3. The plate-wrapped laser-welded steel pipe with a flange according to claim 1, wherein the laser-welded portion extends along the axial direction of the pipe without any welding defect. The fillet weld includes a first weld toe on the other end side of the steel plate and a second weld toe on the bent side,
The angle at the first weld toe is 70° or less,
4. The flanged, plate-wound, laser-welded steel pipe according to any one of claims 1 to 3, wherein the second weld toe has an angle of 70[deg.] or less. The flanged plate according to any one of claims 1 to 4 , wherein the Vickers hardness of the weld metal of the fillet weld is 1.2 times or more higher than the Vickers hardness of the steel plate. Winding laser welded steel pipe. The flanged plate according to any one of claims 1 to 5, wherein the amount of Mn in the weld metal of the fillet weld is 95% or more of the amount of Mn in the steel plate. Winding laser welded steel pipe. A method for manufacturing a plate-wrapped laser-welded steel pipe with a flange, which is a base pipe used for manufacturing parts by a hydroforming method, comprising:
When forming a steel plate into a tubular shape, a steel plate having a flange portion formed by bending one end along the plate longitudinal direction is oriented so that the longitudinal direction of the plate is the direction of the pipe axis, and the flange portion protrudes to the outer peripheral side. or a forming step of forming a flange portion by bending one end of the steel plate to the outer peripheral side along the longitudinal direction of the plate while forming the steel plate into a tubular shape;
A welding step of butting and laser-welding the bent portion provided on the steel plate and the other end of the steel plate when forming the flange portion;
with
In the welding step, welding is performed so as to form a weld metal over the entire thickness direction of the steel plate . 8. The method for producing a plate wound laser welded steel pipe with a flange according to claim 7, wherein the laser welding is performed while supplying a welding filler material. 9. The method for producing a flanged plate wound laser welded steel pipe according to claim 8 , wherein the welding filler material is a welding wire having a diameter of 0.6 to 1.6 mm. In the laser welding , the beam diameter at the focused spot is 0.4 to 1 mm, the laser incident angle is 30 to 60 ° with respect to the flange portion , and 75 to 105 ° with respect to the pipe axis direction. 10. The method for producing a plate-wrapped laser-welded steel pipe with a flange according to any one of claims 7 to 9 .

Images