LMD Device

Abstract

To provide an LMD (Laser Metal Deposition) device capable of suppressing scattered metal powder from adhering to a protective glass.SOLUTION: An LMD device 1 includes: an LMD nozzle 2 penetrating into a protective glass 23 and ejecting by reflecting a laser beam 10 by a reflection mirror 22; and a nozzle tip 3 mounted on the LMD nozzle 2 so as to cover the protective glass 23. The nozzle tip 3 has a central hole 7 for ejecting the laser beam 10 together with protective gas, and at least one power passage for ejecting metal powder together with carrier gas around the central hole 7. A proximal part 71 from a base end at the protective glass 23 side to an intermediate position 70 in the central hole 7 has a reverse conical shape with a diameter reduced as separating from the protective glass 23, and at least a part in a distal part 72 from the intermediate position 70 to the tip has a conical shape with a diameter expanded as separating from the protective glass 23.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an LMD (Laser Metal Deposition) apparatus that irradiates a laser beam onto a workpiece and supplies metal powder. [Background technology]

[0002] Conventionally, there has been known an LMD apparatus that performs build-up welding by irradiating a workpiece with a laser beam and supplying a metal powder to the irradiation position. For example, Patent Document 1 discloses an LMD apparatus 100 as shown in FIG.

[0003] Specifically, the LMD device 100 includes an LMD nozzle 110 that emits a laser beam through a protective glass 112 by reflecting the laser beam off a reflecting mirror 111, and a nozzle tip 120 attached to the LMD nozzle 110 so as to cover the protective glass 112. The protective glass 112 is intended to prevent the reflecting mirror 111 from being contaminated.

[0004] The nozzle tip 120 has a central hole 121 for emitting the laser beam together with a protective gas, which is supplied into the central hole 121 from the LMD nozzle 110.

[0005] 11, the nozzle tip 120 also has four powder passages 122 (two of which are shown in FIG. 11) for discharging the metal powder around the central hole 121. The powder passages 122 are arranged at equal angular intervals of 90 degrees around the central hole 121. Generally, the metal powder is discharged together with a carrier gas. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2010 / 142283 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, when overlay welding is performed using the LMD device 100 as shown in FIG. 10, metal powder that collides with the work surface and scatters may pass through the central hole 121 and adhere to the protective glass 112.

[0008] Therefore, an object of the present invention is to provide an LMD device that can prevent scattered metal powder from adhering to a protective glass. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, an LMD device according to one aspect of the present invention comprises an LMD nozzle that emits a laser beam through a protective glass by reflecting it with a reflecting mirror, and a nozzle tip that is attached to the LMD nozzle so as to cover the protective glass, has a central hole for emitting the laser beam together with a protective gas, and has at least one powder passage for emitting metal powder together with a carrier gas around the central hole, wherein a proximal portion of the central hole from the base end on the protective glass side to an intermediate position has an inverted cone shape that decreases in diameter as it moves away from the protective glass, and at least a portion of a distal portion from the intermediate position to the tip has a cone shape that increases in diameter as it moves away from the protective glass.

[0010] According to the above configuration, the central hole has a minimum diameter at the intermediate position, so that the flow rate of the protective gas can be increased at this intermediate position. Due to the effect of this increase in flow rate and the length of the distal portion from the intermediate position to the tip, it is possible to make it difficult for the metal powder that collides with the work surface and scatters to pass through the distal portion. Therefore, it is possible to suppress the scattered metal powder from adhering to the protective glass. Moreover, since at least a part of the distal portion is conical, it is possible to slow down the flow rate of the protective gas at the tip of the central hole and to release the protective gas in a spreading manner. This allows the shielding performance on the work surface to be improved compared to when the distal portion is cylindrical.

[0011] Furthermore, an LMD device according to another aspect of the present invention comprises an LMD nozzle which emits a laser beam through a protective glass by reflecting it with a reflecting mirror, and a nozzle tip which is attached to the LMD nozzle so as to cover the protective glass, has a central hole for emitting the laser beam together with a protective gas, and has at least one powder passage around the central hole for emitting metal powder together with a carrier gas, wherein a proximal portion of the central hole from the base end on the protective glass side to an intermediate position has an inverted cone shape which decreases in diameter as it moves away from the protective glass, and a distal portion from the intermediate position to the tip has a cylindrical shape.

[0012] According to the above configuration, since the distal portion of the central hole is cylindrical, the flow rate of the protective gas can be increased at this distal portion. Due to the effect of increasing the flow rate and the length of the distal portion, it is possible to make it difficult for the metal powder that collides with the work surface and scatters to pass through the distal portion. Therefore, it is possible to suppress the adhesion of the scattered metal powder to the protective glass. Effect of the Invention

[0013] According to the present invention, there is provided an LMD device capable of preventing scattered metal powder from adhering to a protective glass. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of an LMD device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 4 is a perspective view of a first part of the nozzle tip in the embodiment. [Figure 6] FIG. 13 is a perspective view of the first part in another shape. [Figure 7] FIG. 4 is a perspective view of a third part of the nozzle tip in the embodiment. [Figure 8] FIG. 13 is a cross-sectional view of a modified LMD device. [Figure 9] FIG. 13 is a cross-sectional view of another modified LMD device. [Figure 10] FIG. 1 is a cross-sectional view of a conventional LMD device. [Figure 11] FIG. 11 is a cross-sectional view of a nozzle tip of the LMD device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 to 4 show an LMD apparatus 1 according to one embodiment of the present invention. This LMD apparatus 1 irradiates a laser beam 10 onto a workpiece (not shown) and supplies metal powder to the irradiated position to perform build-up welding.

[0016] Specifically, the LMD device 1 includes an apparatus main body (not shown) including a laser oscillator that emits a laser beam 10, a rod-shaped LMD nozzle 2 extending from the apparatus main body, and a nozzle tip 3 attached to the tip of the LMD nozzle 2. The LMD nozzle 2 includes a hollow nozzle body 21. An opening 21a is provided at the tip of the nozzle body 21, and the opening 21a is closed by a protective glass 23. The protective glass 23 is attached to the nozzle body 21 via a support 24.

[0017] A reflecting mirror 22 is disposed in the nozzle body 21 at a position corresponding to the protective glass 23. In the LMD nozzle 2, the laser beam 10 emitted from the laser oscillator is reflected by the reflecting mirror 22, and is then emitted through the protective glass 23.

[0018] The nozzle tip 3 is attached to the LMD nozzle 2 so as to cover the protective glass 23. The nozzle tip 3 has a central hole 7 for emitting the laser beam 10 together with a protective gas, and four powder passages 8 (see FIGS. 2 and 3) for emitting metal powder together with a carrier gas around the central hole 7. Furthermore, in this embodiment, the nozzle tip 3 has an annular shielding gas passage 9 for emitting a shielding gas around the powder passage 8.

[0019] The protective gas, carrier gas, and shielding gas may all be the same gas, or one or all of them may be different gases, for example, at least one of the protective gas, carrier gas, and shielding gas is argon gas.

[0020] In this embodiment, the nozzle tip 3 includes a plate-shaped first part 4 that abuts against the nozzle body 21 of the LMD nozzle 2, a second part 5 that is superimposed on the first part 4, and a third part 6 that is superimposed on the second part 5. The central hole 7 and the powder passage 8 are formed in the first part 4 and the second part 5. In other words, the second part 5, together with the first part 4, constitutes the central hole 7 and the powder passage 8.

[0021] Although not shown in the figures, sealing materials (e.g., O-rings) for ensuring sealing properties may be sandwiched between the nozzle body 21 and the first part 4, between the first part 4 and the second part 5, and between the second part 5 and the third part 6.

[0022] The second component 5 includes a plate-like portion 51 parallel to the first component 4, and a protruding portion 52 protruding from the plate-like portion 51 along the central hole 7 in the opposite direction to the first component 4. The protruding portion 52 has an outer circumferential surface that tapers toward its tip. Meanwhile, the third component 6 has an accommodation hole 6a into which the protruding portion 52 is inserted, and the inner circumferential surface of this accommodation hole 6a tapers in the protruding direction of the protruding portion 52. A shielding gas passage 9 is formed between the inner circumferential surface of this accommodation hole 6a and the outer circumferential surface of the protruding portion 52.

[0023] In the central hole 7, the protective gas flows in a direction away from the protective glass 23. The central hole 7 includes a proximal portion 71 from the base end on the protective glass 23 side to an intermediate position 70, and a distal portion 72 from the intermediate position 70 to the tip. The focal point 11 of the laser beam is located in the distal portion 72.

[0024] The proximal portion 71 has an inverted cone shape that decreases in diameter as it moves away from the protective glass 23. On the other hand, at least a portion of the distal portion 72 has a cone shape that increases in diameter as it moves away from the protective glass 23. The taper angle of the cone is set to an extent that the protective gas does not peel off from the inner peripheral surface of the distal portion 72 (for example, 10 degrees or less).

[0025] In this embodiment, the distal portion 72 is cylindrical in a region close to the proximal portion 71 and conical in a region close to the tip. However, the distal portion 72 may be conical over its entire length, as in a modified LMD device 1A shown in FIG.

[0026] For example, the diameter of the central hole 7 at the intermediate position 70 is 2.5×10 -4 m 3 When the flow rate is 100 m / s, the flow velocity at the intermediate position 70 is set to be 10 to 15 m / s.

[0027] 1 to 4, it is desirable that the intermediate position 70 is located closer to the tip side than the center of the central hole 7 in the axial direction of the central hole 7. In this embodiment, the intermediate position 70 is located approximately in the center of the protruding portion 52 of the second component 5 in the axial direction of the central hole 7 (which is also the overlapping direction of the first to third components 4 to 6), and the length of the proximal portion 71 is approximately twice the length of the distal portion 72.

[0028] A protective gas is supplied to the central hole 7 from the LMD nozzle 2. As shown in Fig. 5, a protective gas annular groove 42 surrounding the central hole 7 is formed on the contact surface of the first part 4 with the nozzle body 21, and a protective gas inlet groove 41 extending radially outward from the protective gas annular groove 42 is also formed.

[0029] 1, a protective gas supply passage 25 communicating with the protective gas introduction groove 41 is formed in the nozzle body 21. The protective gas is introduced from the protective gas supply passage 25 through the protective gas introduction groove 41 to the protective gas annular groove 42.

[0030] 5, the first component 4 is provided with a partition wall 44 that separates the annular groove 42 for protective gas from the central hole 7. The first component 4 is also provided with a plurality of communication holes 43 that connect the annular groove 42 for protective gas with the central hole 7 at equal angular intervals around the central hole 7. Each communication hole 43 is inclined from the annular groove 42 for protective gas toward the central hole 7 in a direction away from the protective glass 23. Therefore, the protective gas can be sprayed from the communication holes 43 in a direction toward the tip of the central hole 7.

[0031] 2, the four powder passages 8 are disposed at equal angular intervals of 90 degrees around the central hole 7. Note that as long as the tips of the powder passages 8 are positioned at equal angular intervals of 90 degrees around the tip of the central hole 7, the extension direction of the powder passages 8 can be changed as appropriate.

[0032] However, the number of powder passages 8 is not particularly limited as long as the tips of the powder passages 8 are positioned at equiangular intervals around the tip of the central hole 7. Alternatively, instead of multiple powder passages 8, a ring-shaped powder passage 8 surrounding the central hole 7 may be used.

[0033] Metal powder and carrier gas are supplied to each powder passage 8 from the LMD nozzle 2. As shown in Fig. 5, the base end of each powder passage 8 opens to the contact surface of the first part 4 with the nozzle body 21. Meanwhile, the nozzle body 21 is formed with a powder supply path 26 that communicates with the four powder passages 8, as shown in Fig. 3. Metal powder and carrier gas are introduced into each powder passage 8 from this powder supply path 26.

[0034] Shielding gas is supplied to the shielding gas passage 9 from the LMD nozzle 2. As shown in Fig. 7, an annular shielding gas groove 62 surrounding the shielding gas passage 9 (i.e., the above-mentioned accommodation hole 6a) is formed on the contact surface of the third part 6 with the second part 5, and a shielding gas inlet groove 61 extending radially outward from the annular shielding gas groove 62 is also formed. In addition, a through hole 91 penetrating the second part 5 and the first part 4 is provided at a position corresponding to the outer end of the shielding gas inlet groove 61 in the second part 5 and the first part 4, as shown in Fig. 4.

[0035] Meanwhile, a shielding gas supply passage 27 communicating with the through hole 91 is formed in the nozzle body 21. Shielding gas is introduced from this shielding gas supply passage 27 through the through hole 91 and the shielding gas introduction groove 61 to the shielding gas annular groove 62.

[0036] 7, the third component 6 is provided with a partition wall 63 that separates the shielding gas annular groove 62 from the shielding gas passage 9. The partition wall 63 is provided with a plurality of openings 64 distributed in the circumferential direction.

[0037] In this embodiment, one opening 64 is located on an extension line of the shielding gas introduction groove 61. For this reason, the third component 6 is provided with a baffle plate 65 on the imaginary boundary line between the annular groove for shielding gas 62 and the shielding gas introduction groove 61 (the extension line of the outer wall surface of the annular groove for shielding gas 62).

[0038] As described above, in the LMD device 1 of this embodiment, the central hole 7 has a minimum diameter at the intermediate position 70, so that it is possible to increase the flow rate of the protective gas at this intermediate position. Due to the effect of this increase in flow rate and the length of the distal portion 72 from the intermediate position 70 to the tip, it is possible to make it difficult for metal powder that collides with the workpiece surface and is scattered to pass through the distal portion 72. Therefore, it is possible to prevent the scattered metal powder from adhering to the protective glass 23.

[0039] (Modification) The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0040] For example, as in a modified LMD device 1B shown in Fig. 9, the entire distal portion 72 of the central hole 7 may be cylindrical. With this configuration, the flow rate of the protective gas can be increased at the distal portion 72, as in the above embodiment. Due to the effect of increasing the flow rate and the length of the distal portion 72, it is possible to make it difficult for metal powder that collides with the workpiece surface and is scattered to pass through the distal portion 72. Therefore, it is possible to prevent the scattered metal powder from adhering to the protective glass 23.

[0041] However, if at least a part of the distal portion 72 is conical as shown in Fig. 1 or 8, the flow rate of the protective gas can be slowed down at the tip of the central hole 7, and the protective gas can be released in a spreading manner. This improves the shielding performance on the work surface compared to when the entire distal portion 72 is cylindrical. In other words, the oxygen concentration at the processing point can be reduced.

[0042] Also, instead of the first part 4 shown in Fig. 5, a first part 4A shown in Fig. 6 can be used. In this first part 4A, a protective gas introduction groove 41 formed on the contact surface of the first part 4A with the nozzle body 21 extends in the radial direction from the central hole 7. In this case, the protective gas may form a swirling flow in the central hole 7, or may flow back from the tip of the central hole 7 due to turbulence in the central hole 7.

[0043] In contrast, as shown in FIG. 5 , if the first component 4 has an annular groove 42 for protective gas surrounding the central hole 7, a partition wall 44 between the annular groove 42 for protective gas and the central hole 7, and a communication hole 43 connecting the annular groove 42 for protective gas and the central hole 7, the flow of protective gas within the central hole 7 is rectified, making it possible to prevent backflow of the protective gas, etc.

[0044] Alternatively, the nozzle tip 3 may not include the third component 6, and a dedicated shielding gas nozzle that emits shielding gas toward the molten pool (not shown) may be provided on the side of the nozzle tip 3.

[0045] Incidentally, when the nozzle tip 3 includes a third part 6 and a shielding gas passage 9 is formed between the third part 6 and the second part 5, a shielding gas introduction groove 61 formed on the contact surface of the third part 6 with the second part 5 may extend radially from the shielding gas passage 9, similar to the first part 4A shown in Fig. 6, although not shown in the figures. However, in this case, the shielding gas may flow unevenly within the shielding gas passage 9, or may flow back from the tip of the shielding gas passage 9 due to turbulence within the shielding gas passage 9.

[0046] In contrast to this, as in the above embodiment, if an annular shielding gas groove 62 is formed on the contact surface of the third part 6 with the second part 5, surrounding the shielding gas passage 9, and a partition 63 separating the annular shielding gas groove 62 from the shielding gas passage 9 is provided with a plurality of openings 64 distributed in the circumferential direction, the flow of the shielding gas in the shielding gas passage 9 is straightened, thereby making it possible to prevent backflow of the shielding gas, etc.

[0047] (summary) An LMD device according to one aspect of the present invention comprises an LMD nozzle which emits a laser beam through a protective glass by reflecting it with a reflecting mirror, and a nozzle tip which is attached to the LMD nozzle so as to cover the protective glass, has a central hole for emitting the laser beam together with a protective gas, and has at least one powder passage around the central hole for emitting metal powder together with a carrier gas, and is characterized in that a proximal portion of the central hole from the base end on the protective glass side to an intermediate position is inverted cone-shaped with a diameter decreasing as it moves away from the protective glass, and at least a portion of a distal portion from the intermediate position to the tip is cone-shaped with a diameter increasing as it moves away from the protective glass.

[0048] According to the above configuration, the central hole has a minimum diameter at the intermediate position, so that the flow rate of the protective gas can be increased at this intermediate position. Due to the effect of this increase in flow rate and the length of the distal portion from the intermediate position to the tip, it is possible to make it difficult for the metal powder that collides with the work surface and scatters to pass through the distal portion. Therefore, it is possible to suppress the scattered metal powder from adhering to the protective glass. Moreover, since at least a part of the distal portion is conical, it is possible to slow down the flow rate of the protective gas at the tip of the central hole and to release the protective gas in a spreading manner. This allows the shielding performance on the work surface to be improved compared to when the distal portion is cylindrical.

[0049] For example, the distal portion may be cylindrical near the proximal portion and conical near the tip, or the distal portion may be conical along its entire length.

[0050] Furthermore, an LMD device according to another aspect of the present invention comprises an LMD nozzle which emits a laser beam through a protective glass by reflecting it with a reflecting mirror, and a nozzle tip which is attached to the LMD nozzle so as to cover the protective glass, has a central hole for emitting the laser beam together with a protective gas, and has at least one powder passage around the central hole for emitting metal powder together with a carrier gas, wherein a proximal portion of the central hole from the base end on the protective glass side to an intermediate position has an inverted cone shape which decreases in diameter as it moves away from the protective glass, and a distal portion from the intermediate position to the tip has a cylindrical shape.

[0051] According to the above configuration, since the distal portion of the central hole is cylindrical, the flow rate of the protective gas can be increased at this distal portion. Due to the effect of increasing the flow rate and the length of the distal portion, it is possible to make it difficult for the metal powder that collides with the work surface and scatters to pass through the distal portion. Therefore, it is possible to suppress the adhesion of the scattered metal powder to the protective glass.

[0052] For example, the focal point of the laser beam may be located within the distal portion of the central bore.

[0053] The nozzle tip may have a protective gas annular groove surrounding the central hole, through which the protective gas is introduced, on the contact surface with the LMD nozzle, a partition wall separating the protective gas annular groove from the central hole, and a plurality of communication holes communicating the protective gas annular groove and the central hole at equal angular intervals around the central hole. When a protective gas introduction path extending radially from the central hole is formed on the contact surface with the LMD nozzle of the nozzle tip, the protective gas may form a swirling flow in the central hole, or may flow back from the tip of the central hole due to turbulence in the central hole. In contrast, if the first holding member has a protective gas annular groove surrounding the central hole, a partition wall between the protective gas annular groove and the central hole, and a communication hole communicating the protective gas annular groove and the central hole, the flow of the protective gas in the central hole is rectified, and therefore the backflow of the protective gas can be prevented.

[0054] The protective gas may be injected from the communication holes toward the tip of the central hole, the communication holes being inclined from the protective gas annular groove toward the central hole in a direction away from the protective glass.

[0055] The nozzle tip has an annular shielding gas passage for discharging a shielding gas around the at least one powder passage, the nozzle tip includes a first part that abuts against the LMD nozzle, a second part that is superimposed on the first part and that forms the central hole together with the first part, and a third part that is superimposed on the second part, the shielding gas passage is formed between the second part and the third part, a shielding gas annular groove is formed on the contact surface of the third part with the second part, the shielding gas is introduced into the shielding gas passage and the third part is provided with a partition wall that separates the shielding gas annular groove and the shielding gas passage, and the partition wall may be provided with a plurality of openings distributed in the circumferential direction. When an introduction path extending radially from the shielding gas passage is formed on the contact surface of the third part with the second part, the shielding gas may flow unevenly in the shielding gas passage, or may flow back from the tip of the shielding gas passage due to turbulence in the shielding gas passage. In contrast, if an annular shielding gas groove is formed on the contact surface of the third part with the second part, surrounding the shielding gas passage, and a partition wall separating the annular shielding gas groove from the shielding gas passage is provided with a plurality of openings distributed circumferentially, the flow of shielding gas within the shielding gas passage will be straightened, making it possible to prevent backflow of shielding gas, etc. [Explanation of symbols]

[0056] 1 LMD device 10 Laser Beam 11 focus 2 LMD nozzle 22 Reflective mirror 23 Protective Glass 3 Nozzle Tip 4. First Part 42 Annular groove for protective gas 43 Communication hole 44 Bulkhead 5. Second Part 6. Third Part 62 Annular groove for shielding gas 63 Bulkhead 64 Aperture 7 center hole 70 intermediate position 71 Proximal 72 Distal 8 Powder aisle 9 Shielding gas passage

Claims

1. an LMD nozzle that emits a laser beam through a protective glass by reflecting the laser beam with a reflecting mirror; a nozzle tip attached to the LMD nozzle so as to cover the protective glass, the nozzle tip having a central hole for emitting the laser beam together with a protective gas, and at least one powder passage around the central hole for emitting metal powder together with a carrier gas; a proximal portion of the central hole from a base end on the protective glass side to an intermediate position has an inverted cone shape that decreases in diameter as it moves away from the protective glass, and at least a portion of a distal portion from the intermediate position to a tip has a cone shape that increases in diameter as it moves away from the protective glass, a protective gas annular groove surrounding the central hole into which the protective gas is introduced is formed on a contact surface of the nozzle tip with the LMD nozzle; The nozzle tip is provided with a partition wall that separates the annular groove for protective gas and the central hole, and a plurality of communication holes that connect the annular groove for protective gas and the central hole are provided at equal angular intervals around the central hole.

2. The LMD device of claim 1 , wherein the distal portion is cylindrical in a region proximal to the proximal portion and conical in a region proximal to the tip.

3. The LMD device of claim 1 , wherein the distal portion is conical along its entire length.

4. an LMD nozzle that emits a laser beam through a protective glass by reflecting the laser beam with a reflecting mirror; a nozzle tip attached to the LMD nozzle so as to cover the protective glass, the nozzle tip having a central hole for emitting the laser beam together with a protective gas, and at least one powder passage around the central hole for emitting metal powder together with a carrier gas; a proximal portion of the central hole from a base end on the protective glass side to a middle position has an inverted cone shape that decreases in diameter as it moves away from the protective glass, and a distal portion from the middle position to a tip has a cylindrical shape; a protective gas annular groove surrounding the central hole into which the protective gas is introduced is formed on a contact surface of the nozzle tip with the LMD nozzle; The nozzle tip is provided with a partition wall that separates the annular groove for protective gas and the central hole, and a plurality of communication holes that connect the annular groove for protective gas and the central hole are provided at equal angular intervals around the central hole.

5. The LMD device of any one of claims 1 to 4, wherein a focal point of the laser beam is located within the distal portion of the central hole.

6. 6. The LMD device according to claim 1, wherein each of the plurality of communication holes is inclined from the protective gas annular groove toward the central hole in a direction away from the protective glass.

7. the nozzle tip has an annular shield gas passage for discharging a shield gas around the at least one powder passage; the nozzle tip includes a first part that contacts the LMD nozzle, a second part that is superimposed on the first part and that defines the central hole together with the first part, and a third part that is superimposed on the second part, The shielding gas passage is formed between the second part and the third part, a shielding gas annular groove, into which the shielding gas is introduced, surrounding the shielding gas passage, is formed on a contact surface of the third component with the second component; The LMD device according to any one of claims 1 to 6, wherein the third part is provided with a partition wall separating the annular groove for shielding gas and the passage for shielding gas, and the partition wall is provided with a plurality of openings distributed in a circumferential direction.

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