Metal member and method of manufacturing the same

A metal member includes a first plate, and a second plate abutting against and welded to the first plate in at least one butt portion. In the butt portion, a length from a first end to a second end of a welding boundary line between the first plate and the second plate is longer than a length of a straight line connecting the first end to the second end of the welding boundary line.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-121457 filed on Jun. 21, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a metal member and a method of manufacturing the same.

2. Description of Related Art

Butt welding for making metal members abut against each other and welding the metal members together is known. Japanese Unexamined Patent Application Publication No. 2014-205166 (JP 2014-205166 A) discloses a technique for making flat end surfaces of two metal members having a plate shape abut against each other and joining the metal members together by laser welding. In addition, in the technique described in JP 2014-205166 A, a welding boundary line of a butt portion in which the two metal members having a plate shape abut against each other is a straight line.

FIGS. 13 and 14are perspective views showing a metal member501relating to a problem to be solved. A right-handed xyz coordinate system shown in the drawing is provided for convenience to describe a positional relationship between components.

As shown inFIG. 13, the metal member501is obtained by making a first plate502and a second plate503abut against each other in one butt portion SS1and welding the first plate502and the second plate503together. In the butt portion SS1in which the first plate502and the second plate503abut against each other, a welding boundary line LL1between the first plate502and the second plate503is a straight line connecting a first end PP1and a second end PP2of the welding boundary line LL1. In a case where the area of the butt portion SS1, that is, the area of the joint portion in the metal member501is not sufficient with respect to a needed joining strength between the first plate502and the second plate503, the joint portion may fracture.

In order to increase the joining strength between the first plate502and the second plate503, a method of increasing the number of butt portions as shown inFIG. 14can also be considered. In an example shown inFIG. 14, the number of butt portions is three (butt portions SS2, SS3, SS4). However, it may be difficult to increase the number of butt portions due to design limitations.

SUMMARY

The disclosure provides a metal member in which a joining strength of a butt portion between plates joined by butt welding is increased without increasing the number of butt portions of the plates, and a method of manufacturing the same.

A first aspect of the disclosure relates to a metal member. The metal member includes a first plate and a second plate. The second plate abuts against and is welded to the first plate in at least one butt portion. In the butt portion, the length from a first end to a second end of a welding boundary line between the first plate and the second plate is longer than the length of a straight line connecting the first end to the second end of the welding boundary line.

According to the first aspect, during butt welding of the plates abutting against each other, the length of the welding boundary line is set to be longer than the length of the straight line connecting the first end and the second end of the welding boundary line. As a result, the area of the joint portion can be further increased compared to a case where the welding boundary line is a straight line, and thus the joining strength can be further improved.

In the metal member according to the first aspect, the thickness of the first plate and the thickness of the second plate may be different from each other. According to the first aspect, in the metal member, the thickness of a plate used in a portion where the needed strength is relatively high can be made to be relatively large, and the thickness of a plate used in a portion where the needed strength is relatively low can be made to be relatively small. Therefore, the weight of the metal member can be reduced.

In the metal member according to the first aspect, the at least one butt portion may include a first butt portion, a second butt portion, and a curved portion in which the first plate and the second plate abut against and are welded to each other. A first welding boundary line that is a welding boundary line between the first plate and the second plate may be present in the first butt portion, and a second welding boundary line that is a welding boundary line between the first plate and the second plate may be present in the second butt portion. The curved portion may be interposed between the first butt portion and the second butt portion and may connect the first butt portion and the second butt portion to each other. The length from a first end to a second end of the first welding boundary line may be longer than the length of a straight line connecting the first end and the second end of the first welding boundary line. The second welding boundary line may be the shortest line connecting a first end and a second end of the second welding boundary line to each other along a surface of the second plate.

According to the first aspect, during butt welding of the first plate and the second plate, by setting the length from the first end to the second end of the first welding boundary line to be longer than the length of the straight line connecting the first end and the second end to each other, the area of the joint portion can be further increased compared to a case where the welding boundary line is a straight line. As a result, the joining strength can be further improved.

In the metal member according to the first aspect, the second butt portion may include a bent portion having a bending line perpendicular to the second welding boundary line. The first welding boundary line and the curved portion may be on the same side with respect to the bending line. According to the first aspect, in a case where the first welding boundary line and the curved portion are on the same side with respect to the bending line, in the metal member, a protrusion is not formed on the bent portion unlike a case where the curved portion is present in the bent portion. As a result, in a case where the metal member is removed from a bending die after bending, the metal member does not interfere with the bending die in the bent portion.

In the metal member according to the first aspect, an opposite end of the first welding boundary line from the curved portion may be present at a border of the first plate and the second plate. An opposite end of the second welding boundary line from the curved portion may be present at a border of the first plate and the second plate. That is, the first plate and the second plate may be welded in the two butt portions.

A second aspect of the disclosure relates to a method of manufacturing a metal member. The method includes preparing a first plate and a second plate, and making the first plate and the second plate abut against each other in at least one butt portion and welding the first plate and the second plate together. In the butt portion, the length from a first end to a second end of a welding boundary line between the first plate and the second plate is longer than the length of a straight line connecting the first end to the second end of the welding boundary line.

In the method according to the second aspect, the thickness of the first plate and the thickness of the second plate may be different from each other.

In the method according to the second aspect, in the welding, the first plate and the second plate may be made to abut against each other in a first butt portion and a second butt portion and may be welded to each other to form an intermediate product. The method may further include bending the intermediate product formed in the welding. The intermediate product may include a first welding boundary line that is a welding boundary line between the first plate and the second plate in the first butt portion, a second welding boundary line that is a welding boundary line between the first plate and the second plate in the second butt portion, and a curved portion that is interposed between the first butt portion and the second butt portion and connects the first butt portion and the second butt portion to each other. The length from a first end to a second end of the first welding boundary line may be longer than the length of a straight line connecting the first end and the second end of the first welding boundary line. The second welding boundary line may be the shortest line connecting a first end and a second end of the second welding boundary line to each other along a surface of the second plate. In the bending, the intermediate product may be disposed in a bending die such that the second welding boundary line and a bending line are perpendicular to each other and the second welding boundary line is parallel to a direction in which a final product obtained by bending the intermediate product is removed from the bending die and the first welding boundary line and the curved portion are on the same side with respect to the bending line.

According to the second aspect, the first welding boundary line and the curved portion are on the same side with respect to the bending line, in the metal member, and thus a protrusion is not formed on the bent portion unlike a case where the curved portion is present in the bent portion. As a result, in a case where the metal member as a final product is removed from the bending die, the metal member does not interfere with the bending die in the bent portion. Accordingly, the metal member as a final product can be removed from the bending die after bending without interference between the bent portion and the bending die.

According to the aspects, a metal member in which a joining strength of a butt portion between plates joined by butt welding is increased without increasing the number of butt portions of the plates, and a method of manufacturing the same can be provided.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a specific embodiment will be described in detail with reference to the drawings. However, the disclosure is not limited to the following embodiment. In order to clarify the description, the following description and the drawings are appropriately simplified.

First, a configuration of a metal member according to Embodiment 1 will be described with reference toFIG. 1.FIG. 1is a perspective view showing a configuration of a metal member1according to Embodiment 1. A right-handed xyz coordinate system shown inFIG. 1is provided for convenience to describe a positional relationship between components.

As shown inFIG. 1, the metal member1is obtained by making a first plate2and a second plate3abut against each other in at least one butt portion S1and welding the first plate2and the second plate3together. Here, the first plate2and the second plate3are formed of, for example, base metal such as aluminum, iron, stainless steel, titanium, or magnesium.

In the butt portion S1, a length from a first end P1to a second end P2of a welding boundary line L1between the first plate2and the second plate3is longer than a length of a straight line L2connecting the first end P1and the second end P2of the welding boundary line L1. Specifically, the welding boundary line L1is, for example, a wavy curve that oscillates between one side and the other side with respect to the straight line L2.

As described above, during butt welding of plates abutting against each other, by increasing a length of a welding boundary line to be longer than a length of a straight line connecting a first end and a second end of the welding boundary line, the area of the joint portion can be further increased compared to a case where the welding boundary line is a straight line. As a result, the joining strength can be further improved.

In addition, in a case where butt welding progresses from a first end to a second end of a welding boundary line, base metal of the welded portion thermally expands. However, a periphery of the welded portion is cold, and thus the portion that thermally expands due to welding is plastically deformed in a direction in which it is compressed from the periphery and contracts. Further, in a case where the portion that thermally expands due to welding is cooled, the portion pulls the periphery with a strong force. In a case where a welding boundary line is a straight line, a non-welded portion in a butt portion is displaced due to the pulling force. In this portion, the distance between butt end surfaces of plates abutting against each other increases. In a case where the distance between the butt end surfaces increases, it is difficult to weld the plates. Therefore, poor welding is more likely to occur.

On the other hand, in the metal member according to the embodiment, the welding boundary line L1is longer than the straight line L2connecting the first end P1and the second end P2. As a result, the number of tangential directions of the welding boundary line L1is not one and is plural (directions indicated by arrows d1, d2, d3, d4, d5in the drawing). With this configuration, even in a case where base metal in a welded portion thermally expands, a non-welded portion in a butt portion is restricted from being displaced due to the pulling force such that the distance between welded end surfaces of plates abutting against each other increases. As described above, poor welding can be effectively suppressed.

Modification Example 1

FIG. 2is a perspective view showing a modification example of the metal member1according to Embodiment 1. A right-handed xyz coordinate system shown inFIG. 2matches that inFIG. 1. In the example shown inFIG. 1, the thickness of the first plate2and the thickness of the second plate3are the same as each other. However, the thickness of the first plate2and the thickness of the second plate3are not necessarily the same and may be different from each other. As shown inFIG. 2, for example, a thickness t2of the second plate3may be larger than a thickness t1of the first plate2(t2>t1). In the metal member1, the thickness of a plate used in a portion where the needed strength is relatively high can be made to be relatively large, and the thickness of a plate used in a portion where the needed strength is relatively low can be made to be relatively small. Therefore, the weight of the metal member can be effectively reduced.

In addition, in a case where a welding boundary line is a straight line, in a non-welded portion of a butt portion, the distance between butt end surfaces of plates abutting against each other increases due to thermal expansion of a welded portion. During butt welding of plates having different thicknesses, deformation of a non-welded portion caused by thermal expansion of a welded portion tends to become more significant. Therefore, in a case where a welding boundary line is a straight line during butt welding of plates having different thicknesses, poor welding is more likely to occur. Even during butt welding of plates having different thicknesses, by setting the welding boundary line L1to be longer than the straight line L2connecting the first end P1and the second end P2as in the case of the metal member1according to the embodiment, poor welding can be effectively suppressed.

Configuration of Bent Member

First, a configuration of a metal member11according to Embodiment 2 will be described with reference toFIG. 3.FIG. 3is a perspective view showing a configuration of the metal member11according to Embodiment 2. The metal member11is suitable for, for example, a vehicle frame. A right-handed xyz coordinate system shownFIG. 3is provided for convenience to describe a positional relationship between components. As shown inFIG. 3, a first plate12and a second plate13abut against each other and are welded together in a first butt portion S2and a second butt portion S3. That is, the first plate12and the second plate13are welded in the two butt portions. Here, the first plate12and the second plate13are formed of, for example, base metal such as aluminum, iron, stainless steel, titanium, or magnesium.

In the first butt portion S2, a welding boundary line between the first plate12and the second plate13is set as a first welding boundary line L11. In addition, in the second butt portion S3, a welding boundary line between the first plate12and the second plate13is set as a second welding boundary line L13. The first welding boundary line L11and the second welding boundary line L13are connected to each other through a curved portion L12.

A length from a first end P11to a second end P12of the first welding boundary line L11is longer than a straight line L14connecting the first end P11and the second end P12of the first welding boundary line L11. In addition, the second welding boundary line L13is the shortest line connecting a first end P13and a second end P14of the second welding boundary line L13to each other along a surface of the second plate13. An opposite end of the first welding boundary line L11(the second end P12of the first welding boundary line L11) from the curved portion L12is present at a border of the first plate12and the second plate13. In addition, an opposite end of the second welding boundary line L13(the second end P14of the second welding boundary line L13) from the curved portion L12is present at a border of the first plate12and the second plate13.

As described above, during butt welding of the first plate12and the second plate13, by setting the length from the first end P11to the second end P12of the first welding boundary line L11to be longer than the straight line L14connecting the first end P11and the second end P12of the first welding boundary line L11, the area of the joint portion can be further increased compared to a case where the welding boundary line is a straight line. As a result, the joining strength can be further improved. In addition, as described above in Embodiment 1, poor welding caused by thermal expansion of base metal in a welded portion can also be effectively suppressed.

The metal member11includes a bent portion16having a bending line L15perpendicular to the second welding boundary line L13. The first welding boundary line L11and the curved portion L12are on the same side with respect to the bending line L15. In a case where the metal member11is configured as described above, as described below, the metal member11as a final product can be removed from a bending die after bending without interference between the bent portion16and the bending die.

The thickness of the first plate12and the thickness of the second plate13may be different from each other. For example, a thickness t2of the second plate13may be larger than a thickness t1of the first plate12(t2>t1). In the metal member11, the thickness of a plate used in a portion where the needed strength is relatively high can be made to be relatively large, and the thickness of a plate used in a portion where the needed strength is relatively low can be made to be relatively small. Therefore, the weight of the metal member can be effectively reduced. That is, a metal member with a sufficient joining strength and a reduced weight can be provided.

Method of Manufacturing Bent Member

A method of manufacturing the metal member11according to Embodiment 2 will be described with reference toFIGS. 4 to 8.FIG. 4is a flowchart showing the method of manufacturing the metal member11according to Embodiment 2.FIGS. 5 to 8are schematic diagrams showing the method of manufacturing the metal member11according to Embodiment 2. A right-handed xyz coordinate system shown inFIGS. 5 to 8matches that inFIG. 3.

As shown inFIGS. 4 and 5, first, the first plate12and the second plate13that are materials constituting the metal member11are cut (Step S101). Next, as shown inFIGS. 4 and 6, the first plate12and the second plate13are disposed to abut against each other in the first butt portion S2and the second butt portion S3(Step S102).

Next, as shown inFIGS. 4 and 7, the first plate12and the second plate13are welded together in the respective butt portions to form an intermediate product (Step S103). Here, a welding method is not particularly limited, and laser welding is preferably used from the viewpoint of suppressing thermal strain. As shown inFIGS. 4 and 8, the intermediate product10formed in Step S103is bent by pressing (Step S104). That is, as shown inFIG. 8the intermediate product10is disposed in a bending die20and is bent along the predetermined bending line L15.

As shown inFIG. 7, in the intermediate product10, a welding boundary line between the first plate12and the second plate13in the first butt portion S2is set as the first welding boundary line L11, and a welding boundary line between the first plate12and the second plate13in the second butt portion S3is set as the second welding boundary line L13. The first welding boundary line L11and the second welding boundary line L13are connected to each other through a curved portion L12. A length from a first end P11to a second end P12of the first welding boundary line L11is longer than a straight line L14connecting the first end P11and the second end P12of the first welding boundary line L11. In addition, the second welding boundary line L13is the shortest line connecting a first end P13and a second end P14of the second welding boundary line L13to each other along a surface of the second plate13. Further, the bending line L15is perpendicular to the second welding boundary line L13.

In Step S104of performing bending shown inFIG. 4, the intermediate product10(refer toFIG. 8) is disposed in the bending die20such that the second welding boundary line L13is parallel to a direction in which a final product after bending is removed from the bending die20and the first welding boundary line L11and the curved portion L12are on the same side with respect to the bending line L15. As a result, the metal member according to Embodiment 2 can be manufactured.

An effect that is obtained in a case where the intermediate product10is disposed in the bending die20such that the first welding boundary line L11and the curved portion L12are on the same side with respect to the bending line L15will be described below.

FIG. 9is a perspective view schematically showing a state before removing a metal member111according to Comparative Example from a bending die120. A right-handed xyz coordinate system shown inFIG. 9matches that inFIG. 3.FIG. 10is a sectional view taken along line X-X ofFIG. 9. As shown inFIG. 9, the bending line L15intersects the curved portion L12. As a result, as shown inFIG. 10, a protrusion D1is formed on the bent portion16of the metal member111. As a result, in a case where the metal member111as a final product is removed from the bending die120, the metal member111interferes with the bending die120at the protrusion D1of the bent portion16.

FIG. 11is a perspective view schematically showing a state before removing the metal member11according to Embodiment 2 from the bending die20. A right-handed xyz coordinate system shown inFIG. 11matches that inFIG. 3.FIG. 12is a sectional view taken along line XII-XII ofFIG. 11. As shown inFIG. 11, in the metal member11, the first welding boundary line L11and the curved portion L12are on the same side with respect to the bending line L15. As a result, as shown inFIG. 12, in the metal member11, the protrusion D1is not formed on the bent portion16unlike in the metal member111according to Comparative Example. As a result, in a case where the metal member11as a final product is removed from the bending die20, the metal member11does not interfere with the bending die20in the bent portion16. That is, the metal member11as a final product can be removed from the bending die20after bending without interference between the bent portion16and the bending die20.

The disclosure is not limited to the above-described embodiment, and the embodiment can be appropriately modified.