Method for manufacturing joined body

Firstly, an upper base material is disposed above a lower base material. Secondly, a laser beam is irradiated so that an area irradiated with a laser beam at a time of melting start is formed on only an upper surface of the upper base material or on only both the upper surface and an end surface of the upper base material, whereby the end surface of the upper base material and the lower base material are fillet welded. With the end surface as a reference, a side the upper surface and the lower surface are positioned is a first side, and an opposite side of the first side is a second side. The laser beam is set such that an intensity of the laser beam is lower toward the second side from the first peak area within the irradiation area of the laser beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of Japanese Patent Application No. 2019-45944 filed on Mar. 13, 2019 with the Japan Patent Office, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a method for manufacturing a joined body through the laser welding.

There have been various methods proposed for joining materials made of metal by laser welding. For example, in a laser welding method disclosed in U.S. Pat. No. 6,318,797 in Patent Gazette, a fillet welding is performed for two metal plates vertically stacked with an interspace therebetween. In laser welding method thereof, conditions for the laser welding are set so as to form a specified angle between a portion of a welding joint, which faces the interspace, formed of a molten metal because of the laser welding and a metal plate on a lower side.

SUMMARY

However, in the laser welding method disclosed in U.S. Pat. No. 6,318,797 in Patent Gazette, while the metal plates on both upper and lower sides are irradiated with a laser beam, an intensity of laser beam irradiated to the metal plate on the upper side is higher than that to the metal plate on the lower side. Accordingly, there is a risk that the intensity of laser beam irradiated to an edge of the metal plate on the upper side is so high that the edge of the metal plate on the upper side is drastically burned through. In such a case, a throat depth of the welding joint is decreased and the welding strength is correspondingly lowered.

According to one aspect of the present disclosure, it is preferable to increase welding strength.

One aspect of the present disclosure is a method for manufacturing a joined body by joining an upper base material and a lower base material through a laser welding. The upper base material comprises an upper surface, a lower surface and an end surface. The lower surface is positioned on an opposite side from the upper surface. The end surface is positioned between an edge of the upper surface and an edge of the lower surface. The manufacturing method hereof comprises disposing the upper base material above the lower base material in such a manner that the lower surface of the upper base material faces the lower base material, and, the end surface of the upper base material is elongated along the lower base material. The method comprises irradiating a laser beam so as to form an initial irradiation area on only the upper surface of the upper base material or on only both the upper surface and the end surface of the upper base material, whereby the end surface of the upper base material and the lower base material are fillet welded. The initial irradiation area is an area irradiated with the laser beam at a time of melting start because of the fillet welding. Here, with the end surface as a reference, a side where the upper surface and the lower surface are positioned is a first side, and an opposite side of the first side is a second side. Also, a direction the upper surface and the lower surface of the upper base material are opposing is a reference direction. An irradiation direction of the laser beam is inclined relative to the reference direction so that the laser beam travels toward the first side as the laser beam approaches the upper base material. Further, the laser beam is set in such a manner that a first peak area on which the intensity of the laser beam irradiated is the highest among the irradiation area of the laser beam is formed, and that the intensity of the laser beam is lower toward the second side from the first peak area within the irradiation area of the laser beam.

The aforementioned configuration allows an irradiation of the laser beam to only the upper surface of the upper base material, or to only both the upper surface and the end surface of the upper base material when the upper base material starts melting because of the fillet welding. Within the irradiation area of the laser beam, the intensity of the laser beam is lower toward the second side from the first peak area. Consequently, the intensity of laser beam irradiated to or near the end surface of the upper base material can be suppressed, and therefore the area near the end surface of the upper base material can be gradually molten. As a result, the upper base material is suitably burned through and the throat depth of the welding joint is increased. Accordingly, the welding strength is improved.

According to one aspect of the present disclosure, the laser beam may be further set in such a manner that the intensity of the laser beam is lower toward the first side from the first peak area within the irradiation area of the laser beam.

This configuration allows a gradual melting of a part of the upper base material located on the first side of the first peak area within the irradiation area of the laser beam, and therefore the aforementioned part is suitably burned through. As a result, the throat depth of the welding joint is increased and the welding strength is improved.

In one aspect of the present disclosure, the first peak area of the laser beam may be positioned on the upper surface of the upper base material.

In another aspect of the present disclosure, the first peak area of the laser beam may be positioned at a boundary between the upper surface and the end surface.

The aforementioned configuration allows a suitable suppression of the intensity of laser beam irradiated to or near the end surface of the upper base material, whereby the area near the end surface of the upper base material is more gradually molten. As a result, the upper base material is suitably burned through and the throat depth of the welding joint is increased and therefore the welding strength is improved.

In one aspect of the present disclosure, the first peak area of the laser beam may be formed substantially in the middle between an end of the first side and an end of the second side within the irradiation area of the laser beam.

This configuration allows a proper control of the laser beam intensity.

In one aspect of the present disclosure, the upper base material may be arranged with an interspace between itself and the lower base material.

This configuration allows a proper performance of the welding.

In one aspect of the present disclosure, the upper base material may be a plate-shaped member.

This configuration allows a proper performance of the welding.

According to one aspect of the present disclosure, the laser beam may be set in such a manner that at least one second peak area is formed on the first side and/or the second side of the first peak area within the irradiation area of the laser beam. The second peak area is an area in which the intensity of the laser beam is locally high and may be lower than that in the first peak area.

The aforementioned configuration allows a more suitable adjustment of the intensity of the laser beam at a part of the upper base material located on the first side and/or the second side of the first peak area within the irradiation area of the laser beam. As a result, the upper base material is more suitably molten, and the throat depth of the welding joint is increased.

In one aspect of the present disclosure, the initial irradiation area of the laser beam may be formed at an area near a boundary between the upper surface and the end surface of the upper base material.

This configuration allows a gradual melting of the area near the end surface of the upper base material and an increase in amount of the molten upper base material. Accordingly, the throat depth of the welding joint is increased and the welding strength is improved.

According to one aspect of the present disclosure, the fillet welding may be performed by displacing the irradiation area of the laser beam along a path extending in a substantially straight manner.

This configuration further simplifies a configuration of an equipment for performing a laser welding. It also simplifies a process of performing the laser welding, whereby a work efficiency is improved.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

It is to be understood that although some embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments below, but may be implemented in various forms within the technical scope of the present disclosure.

As shown inFIG. 1, a laser welder1of the present embodiment comprises a laser oscillator30, a light path20, and a processing head10.

The laser oscillator30excites a laser medium and amplifies a light emitted from the excited laser medium in order to generate a laser beam40.

The light path20leads the laser beam40generated by the laser oscillator30to the processing head10.

The processing head10irradiates the laser beam40to a base material50to perform a laser welding. The processing head10comprises a collimation device11, a mode setter12, a focusing lens13, and a position corrector14. The processing head10may not comprise the position corrector14.

The collimation device11uses, for example, a lens and/or a mirror to adjust an orientation of the led laser beam40from the laser oscillator30.

The mode setter12uses a member for changing a path of light, for example, a lens, and/or a DOE (Diffractive Optical Element) to set a mode of the laser beam40. The mode herein is a distribution pattern of intensity of the laser beam40within an irradiation area of the laser beam40. The intensity of the laser beam40may be, for example, an energy density of the laser beam40. Specifically, a mode of the laser beam40is set as the laser beam40the orientation of which is adjusted by a collimation device11passes through the member such as a lens provided in the mode setter12.

The focusing lens13is a part for adjusting a diaphragm of the laser beam40the mode of which is set by the mode setter12. When the welding is performed, the diaphragm of the laser beam40is adjusted so as to be converged immediately before reaching the base material50.

The position corrector14is a part for adjusting a position where the laser beam40passing through the focusing lens13is irradiated.

In the present embodiment, the laser welder1performs a fillet welding to join an upper base material60and a lower base material70(seeFIGS. 2 to 4). A joined body80, which is a member comprising the upper base material60and the lower base material70, is produced after this performance (seeFIG. 5). In the present embodiment, the upper base material60and the lower base material70are, for example, flat plate members with rectangular shapes. The upper base material60and the lower base material70may be made from, for example, iron, stainless steel, or aluminum, or may be made from an alloy containing iron, stainless steel, or aluminum. Also, the upper base material60and the lower base material70may be made from metals other than those described above. Furthermore, the upper base material60and the lower base material70may be equal or different in thickness.

Hereinafter, surfaces of the upper base material60and the lower base material70, facing one another along a thickness direction, will be respectively upper surfaces61and71, and lower surfaces62and72. A surface of the upper base material60positioning between an edge of the upper surface61and an edge of the lower surface62will be an end surface63.

The method for manufacturing the joined body80according to the present embodiment comprises an arrangement process and a welding process. These processes will be described hereinafter.

3. Arrangement Process

In the arrangement process, the upper base material60is disposed above the lower base material70(seeFIG. 2). At this time, in the upper base material60and the lower base material70, the upper surfaces61and71are positioned on the upper side, and the lower surfaces62and72are positioned on the lower side. In other words, the lower surface62of the upper base material60faces the upper surface71of the lower base material70, and the end surface63of the upper base material60is elongated along the upper surface71of the lower base material70. Correspondingly, the upper surface71of the lower base material70is partially covered with the upper base material60. Also, an angle of the end surface63to the upper surface71of the lower base material70is substantially 90°. However, the angle is not limited to substantially 90° but may be suitably set.

In the present embodiment, by way of examples, the upper base material60and the lower base material70are arranged with an interspace therebetween. More specifically, for example, the upper base material60and the lower base material70may be arranged in such a manner that the lower surface62of the upper base material60and the upper surface71of the lower base material70have a substantially constantly maintained interspace therebetween. However, the upper base material60and the lower base material70may be arranged in such a manner that, for example, the lower surface62is inclined relative to the upper surface71, or such a manner that the lower surface62and the upper surface71are in contact with each other.

Hereinafter, with the end surface63of the upper base material60as a reference, a side where the upper surface61and the lower surface62of the upper base material60are positioned will be a first side91, and an opposite side from the first side91will be a second side92. In other words, with the end surface63as a reference, a side where a part of the lower base material70covered with the upper base material60is positioned is the first side91, and a side where a part of the lower base material70not covered with the upper base material60is positioned is the second side92. Also, a direction along which the upper surface61and the lower surface62of the upper base material60are opposing (namely, a thickness direction of the upper base material60) will be a reference direction90.

4. Welding Process

The welding process follows the arrangement process. In the welding process, a fillet welding is performed by the laser welder1through the laser welding, along the end surface63of the upper base material60, which is previously arranged accordingly in the arrangement process (seeFIGS. 2 to 4). In the fillet welding, the end surface63of the upper base material60is joined with the upper surface71of the lower base material70arranged relative to the end surface63at substantially 90°. However, in the fillet welding, the end surface63may be joined with the upper surface71arranged relative to the end surface63at a degree other than substantially 90°.

Through the fillet welding, the laser beam40is so irradiated as to form an initial irradiation area43on only the upper surface61of the upper base material60or on only both the upper surface61and the end surface63of the upper base material60. Here, the initial irradiation area43is an area irradiated with the laser beam40at a time of melting start because of the fillet welding. Specifically, in the fillet welding, when the upper base material60newly starts melting because of an irradiation of the laser beam40, the lower base material70is not irradiated with the laser beam40but only the upper base material60is irradiated with the laser beam40. After the upper base material60is molten because of the irradiation of the laser beam40, the lower base material70is irradiated with the laser beam40, resulting in melting of the lower base material70.

FIG. 2shows the upper base material60and the lower base material70to which the laser welding is performed, viewed along an extending direction of the end surface63of the upper base material60in the welding process. As shown inFIG. 2, an irradiation direction of the laser beam40is inclined relative to the reference direction90so that the laser beam travels toward the first side91as the laser beam approaches the upper base material60. Specifically, a laser light source of the laser beam40of the laser welder1is disposed on the second side92relative to the end surface63of the upper base material60. The laser beam40is irradiated from an oblique upside on the upper surface61of the upper base material60. Specifically, an angle93, which is made by the laser beam40and the reference direction90, is an acute angle.

The laser beam40is set in such a manner that a first peak area41on which the intensity of the laser beam40irradiated is the highest among the irradiation area of the laser beam40is formed. A curve42shown inFIG. 2indicates an intensity distribution of the laser beam40along a direction toward the first side91and the second side92from the first peak area41within a planar irradiation area perpendicular to the laser beam40.

As shown by the curve42, in the present embodiment, by way of examples, the first peak area41in form of a point is formed at a position substantially in the middle between an end of the first side91and an end of the second side92within the irradiation area. It is not limited to the above-described, but the first peak area41may be also formed on the first side91or the second side92relative to the above-described position. Also, the first peak area41may not be in form of a point but may have a specific areal extent. As shown by the curve42, the intensity of the laser beam40is lower toward the second side92from the first peak area41and toward the first side91from the first peak area41.

Besides the above-described, the laser beam40may be set in such a manner that at least one second peak area44is formed on the first side91and/or the second side92of the first peak area41within the planar irradiation area perpendicular to the laser beam40(seeFIG. 6). The second peak area44is an area where the intensity of the laser beam40is locally high, and the intensity of the laser beam40of the second peak area44is lower than that of the first peak area41.

A curve45inFIG. 6indicates setting values of an intensity distribution of the laser beam40when two second peak areas44are respectively formed on the first side91and the second side92of the first peak area41within the aforementioned irradiation area of the laser beam40. The intensity of the laser beam40may be, for example, set to correspond to the curve45. A curve46inFIG. 7indicates measured values of an intensity distribution of the laser beam40that is set to correspond to the curve45.

As shown inFIG. 2, in the present embodiment by way of examples, the initial irradiation area43of the laser beam40is positioned on the upper surface61near a boundary64between the upper surface61and the end surface63of the upper base material60. Specifically, the initial irradiation area43is formed at a position on the upper surface61, which is slightly separated from the boundary64, or a position on the upper surface61, which is adjacent to the boundary64. Meanwhile, the first peak area41of the laser beam40is positioned on the upper surface61.

However, it is not limited to the above-mentioned, but the initial irradiation area43may also be formed on a position adjacent to the boundary64on the upper surface61of the upper base material60. In this case, too, the first peak area41of the laser beam40is formed on the upper surface61. Also, the initial irradiation area43may be formed on the upper surface61and the end surface63(seeFIG. 3). In such a case, too, it is preferable that the first peak area41is formed on the upper surface61. As shown inFIG. 3, for this case, the first peak area41may be formed at the boundary64. Also, the first peak area41may be formed on the end surface63.

Through the fillet welding in the welding process, for example, the irradiation area on the upper base material60(namely, the initial irradiation area43) is displaced along a path extending in a substantially straight manner (seeFIG. 4). However, it is not limited to the above-described, the irradiation area may be, for example, displaced along a curved or bent path.

(1) According to the aforementioned embodiment, through the fillet welding in the welding process, when the upper base material starts melting, only the upper surface61of the upper base material60, or only both the upper surface61and the end surface63of the upper base material60are irradiated with the laser beam40. It enables the upper base material60to be sufficiently molten. Furthermore, within the irradiation area of the laser beam40, the intensity of the laser beam40is lower toward the second side92from the first peak area41. Accordingly, the intensity of the laser beam40irradiated to or near the end surface63of the upper base material60is suppressed, resulting in a gradual melting of the area near the end surface63of the upper base material60.

FIG. 5is a sectional view of a welding joint81, which is formed in the joined body80in the welding process, perpendicular to a movement course of the irradiation area of the laser beam40. The fillet welding in welding process melts the entire end surface63of the upper base material60and suitably burns through the upper base material60. This results in that, as shown inFIG. 5, the welding joint81is formed in an area from a top end of the end surface63of the upper base material60to the upper surface71of the lower base material70, and that a throat depth84of the welding joint81is increased and the welding strength can be improved.

In the aforementioned embodiment, by way of examples, a shortest distance between an inner lateral surface82and an outer lateral surface83in the welding joint81is defined as a throat depth. The inner lateral surface82is a part of the welding joint81, which faces the interspace between the upper base material60and the lower base material70. Meanwhile, the outer lateral surface83is a surface on an opposite side from the inner lateral surface82of the welding joint81(namely, a surface exposed outside). A length indicated by “84” in the welding joint81ofFIG. 5is the throat depth. In the arrangement process, there may be a case that the upper base material60and the lower base material70are arranged in such a manner that the lower surface62and the upper surface71are in contact. In such a case, a shortest distance between a part of the welding joint81adjacent to the lower surface62or the upper surface71and the outer lateral surface of the welding joint81may be the throat depth.

(2) Furthermore, the laser beam40is set in such a manner that the intensity of the laser beam40is lower toward the first side91from the first peak area41within the irradiation area of the laser beam40. This setting allows a gradual melting of a part of the upper base material60located on the first side91of the first peak area41within the irradiation area of the laser beam40, resulting in the part suitably burned through. Consequently, the throat depth84of the welding joint81is increased and the welding strength is improved.

(3) The first peak area41of the laser beam40is positioned on the upper surface61of the upper base material60, or at the boundary64between the upper surface61and the end surface63. This suitably suppresses the intensity of the laser beam40irradiated to or near the end surface63of the upper base material60, resulting in a more gradual melting of the area near the end surface63. Consequently, the upper base material60is suitably burned through and therefore the throat depth84of the welding joint81is increased.

(4) The laser beam40may be set in such a manner that at least one second peak area44is formed on the first side91and/or the second side92of the first peak area41within the irradiation area of the laser beam40. This setting allows a more suitable adjustment of the intensity of the laser beam40at a part of the upper base material60located on the first side91and/or the second side92of the first peak area41within the irradiation area of the laser beam40. Consequently, the upper base material60is molten in a more suitable manner, and therefore the throat depth84of the welding joint81is increased.

(5) The initial irradiation area43of the laser beam40may be formed at an area near the boundary64on the upper surface61of the upper base material60. In such a case, while the area near the end surface63of the upper base material60is gradually molten, an amount of the molten upper base material60is increased. Consequently, the throat depth84of the welding joint81is increased, and therefore the welding strength is improved.

(6) Through the fillet welding in the welding process, the irradiation area of the laser beam40is displaced along a path extending in a substantially straight manner. Thus, the laser welder1can be configured more simply. It also simplifies the welding process, resulting in an improvement of work efficiency.

6. Other Embodiments

(1) In the aforementioned embodiment, the upper base material60and the lower base material70are, for example, rectangle plate-shaped members. However, shapes of the upper base material60and the lower base material70are not limited to the above-described but may be, for example, curved or bent plate-shaped members. Also, the lower base material70may be, for example, a pipe-shaped member, and the upper base material60may be joined to an outer circumferential surface of the lower base material70by using the method disclosed in the aforementioned embodiment. Furthermore, each of the upper base material60and the lower base material70may be a part of another member.

(2) A function performed by a single element in the aforementioned embodiments may be achieved by a plurality of elements, or a function performed by a plurality of elements may be achieved by a single element. Also, a part of a configuration in the aforementioned embodiments may be omitted. Further, at least a part of a configuration in one of the aforementioned embodiments may be added to, or may be replaced with, a configuration in another one of the aforementioned embodiments.