JP7629804B2 - Nozzle Tip - Google Patents

Description

The present invention relates to a nozzle tip that is attached to the end of an LMD (Laser Metal Deposition) nozzle.

Conventionally, LMD devices have been known that irradiate a laser beam onto a workpiece and supply metal powder to the irradiation position to perform build-up welding. The LMD device includes an LMD nozzle that emits a laser beam and a nozzle tip that is attached to the tip of the LMD nozzle.

For example, Patent Document 1 discloses a nozzle tip 100 as shown in Figure 10. This nozzle tip 100 has a central hole 110 for emitting a laser beam together with a protective gas, and four powder passages 120 (two of which are shown in Figure 10) for emitting metal powder around the central hole 110.

The powder passages 120 are arranged at equal angular intervals of 90 degrees around the central hole 110. Generally, the metal powder is released together with the carrier gas. Instead of multiple powder passages 120, it is also possible to adopt an annular powder passage surrounding the central hole 110.

International Publication No. 2010/142283

When performing overlay welding using an LMD device, shielding gas is also discharged toward the molten pool. The shielding gas may be discharged from a dedicated shielding gas nozzle that is provided separately from the nozzle tip. Alternatively, the nozzle tip may be composed of a tip body having a central hole for the laser beam and at least one powder passage, and a cover that covers the tip body, and an annular shielding gas passage may be formed between the tip body and the cover.

However, when a shielding gas passage is formed between the tip body and the cover, the shielding gas may flow unevenly within the shielding gas passage, or may flow back from the tip of the shielding gas passage due to turbulence within the shielding gas passage.

The present invention aims to provide a nozzle tip that can straighten the flow of shielding gas in the shielding gas passage formed between the tip body and the cover.

In order to solve the above problem, the nozzle tip of the present invention is a nozzle tip attached to the tip of an LMD nozzle, and is characterized in that it comprises a tip body having a central hole for emitting the laser beam emitted from the LMD nozzle together with a protective gas, and at least one powder passage for emitting metal powder together with a carrier gas around the central hole, and a cover that is superimposed on the tip body and forms an annular shielding gas passage between the tip body and the cover for emitting shielding gas around the at least one powder passage, and a shielding gas annular groove is formed on the contact surface of the cover with the tip body, surrounding the shielding gas passage into which the shielding gas is introduced, and the cover is provided with a partition wall that separates the shielding gas annular groove from the shielding gas passage, and the partition wall is provided with a plurality of openings distributed in the circumferential direction.

According to the above configuration, an annular shielding gas groove is formed on the contact surface of the cover with the tip body, surrounding the shielding gas passage, and a partition wall separating the annular shielding gas groove from the shielding gas passage is provided with multiple openings distributed in the circumferential direction, so that the flow of shielding gas in the shielding gas passage can be straightened. This makes it possible to prevent backflow of shielding gas, etc.

According to the present invention, the flow of shielding gas in the shielding gas passage formed between the tip body and the cover can be straightened.

FIG. 2 is a cross-sectional view of a nozzle tip and an LMD nozzle according to one embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 4 is a perspective view of a first part of the tip body in the embodiment. FIG. 13 is a perspective view of a first part of another shape. FIG. 4 is a perspective view of a cover in the embodiment. FIG. 11 is a cross-sectional view of a nozzle tip according to a modified example. FIG. 11 is a cross-sectional view of a nozzle tip according to another modified example. FIG. 1 is a cross-sectional view of a conventional nozzle tip.

Figures 1 to 4 show an LMD device including a nozzle tip 3 according to one embodiment of the present invention. This LMD device irradiates a laser beam 10 onto a workpiece (not shown) and supplies metal powder to the irradiation position to perform build-up welding.

Specifically, the LMD device includes a device body (not shown) that includes a laser oscillator that emits a laser beam 10, a rod-shaped LMD nozzle 2 that extends from the device 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.

In this embodiment, 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. The nozzle tip 3 is attached to the LMD nozzle 2 so as to cover the protective glass 23.

A reflecting mirror 22 is disposed in the nozzle body 21 at a position corresponding to the protective glass 23. The LMD nozzle 2 reflects the laser beam 10 emitted from the laser oscillator by the reflecting mirror 22, causing the laser beam 10 to pass through the protective glass 23 and be emitted.

However, the LMD nozzle 2 does not necessarily need to bend the optical path of the laser beam 10 inside, and may emit the laser beam 10 straight along the optical axis direction of the laser oscillator. Also, the LMD nozzle 2 does not need to include the protective glass 23.

The nozzle tip 3 includes a tip body 30 having a central hole 7 for the laser beam 10 and four powder passages 8 (see Figures 2 and 3), and a cover 6 superimposed on the tip body 30. The central hole 7 is for emitting the laser beam 10 together with a protective gas, and the powder passages 8 are for emitting metal powder together with a carrier gas around the central hole 7. Between the tip body 30 and the cover 6, an annular shielding gas passage 9 is formed for emitting shielding gas around the powder passages 8.

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.

In this embodiment, the tip body 30 includes a plate-shaped first part 4 that abuts against the nozzle body 21 of the LMD nozzle 2, and a second part 5 that is overlaid on the first part 4. 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. The cover 6 is overlaid on the second part 5.

Although not shown, a sealant (e.g., an O-ring) 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 cover 6 to ensure a seal.

The second part 5 includes a plate-like portion 51 parallel to the first part 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 part 4. The protruding portion 52 has an outer peripheral surface that tapers toward its tip. Meanwhile, the cover 6 has a housing hole 6a into which the protruding portion 52 is inserted, and the inner peripheral surface of this housing hole 6a tapers in the direction in which the protruding portion 52 protrudes. A shielding gas passage 9 is formed between the inner peripheral surface of this housing hole 6a and the outer peripheral surface of the protruding portion 52.

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 extending from the base end on the protective glass 23 side to an intermediate position 70, and a distal portion 72 extending from the intermediate position 70 to the tip. The focal point 11 of the laser beam is located within the distal portion 72.

The proximal portion 71 is an inverted cone shape that narrows as it moves away from the protective glass 23. On the other hand, at least a portion of the distal portion 72 is a cone shape that expands 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 surface of the distal portion 72 (for example, 10 degrees or less).

In this embodiment, the distal portion 72 is cylindrical in the region close to the proximal portion 71 and conical in the region close to the tip. However, the distal portion 72 may be conical over its entire length, as in the nozzle tip 3A of a modified example shown in FIG. 8. Alternatively, the entire distal portion 72 of the central hole 7 may be cylindrical, as in the nozzle tip 3B of another modified example shown in FIG. 9.

For example, the diameter of central hole 7 at intermediate position 70 is set so that when the flow rate of protective gas supplied to central hole 7 is 2.5×10 ^-4 m ³ /s, the flow velocity at intermediate position 70 is 10 to 15 m/s. However, central hole 7 does not necessarily have to have a minimum diameter at intermediate position 70, and although not shown in the figure, central hole 7 may be entirely inverted cone-shaped.

Returning to Figures 1 to 4, protective gas is supplied to the central hole 7 from the LMD nozzle 2. As shown in Figure 5, a protective gas annular groove 42 is formed on the contact surface of the first part 4 with the nozzle body 21, surrounding the central hole 7, and a protective gas introduction groove 41 is formed extending radially outward from the protective gas annular groove 42.

On the other hand, the nozzle body 21 is formed with a protective gas supply passage 25 that communicates with the protective gas introduction groove 41 as shown in FIG. 1. Protective gas is introduced from this protective gas supply passage 25 through the protective gas introduction groove 41 to the protective gas annular groove 42.

As shown in FIG. 5, the first part 4 is provided with a partition wall 44 that separates the annular groove 42 for protective gas from the central hole 7. The first part 4 also has a plurality of communication holes 43 that connect the annular groove 42 for protective gas with the central hole 7 and are provided 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 hole 43 in a direction toward the tip of the central hole 7.

As shown in FIG. 2, the four powder passages 8 are arranged at equal angular intervals of 90 degrees around the central hole 7. Note that the extension direction of the powder passages 8 can be changed as appropriate, 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.

However, the number of powder passages 8 is not particularly limited as long as the tips of the powder passages 8 are positioned at equal angular 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.

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 with the nozzle body 21 of the first part 4. 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.

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

On the other hand, a shielding gas supply passage 27 that communicates 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.

As shown in FIG. 7, the cover 6 is provided with an annular partition 63 that separates the shielding gas annular groove 62 from the shielding gas passage 9. This partition 63 is provided with a plurality of openings 64 distributed in the circumferential direction. In other words, the partition 63 is divided into a plurality of arc-shaped pieces. In the illustrated example, the number of openings 64 is five, but the number of openings 64 may be four or less, or six or more.

In the circumferential direction around the shielding gas passage 9, it is desirable that the width of each opening 64 be shorter than the width of each of the pieces that make up the partition wall 63.

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

As described above, in the nozzle tip 3 of this embodiment, the annular groove 62 for shielding gas that surrounds the shielding gas passage 9 is formed on the contact surface of the cover 6 with the tip body 30, and a plurality of openings 64 are provided in the partition wall 63 that separates the annular groove 62 for shielding gas from the shielding gas passage 9, so that the flow of shielding gas in the shielding gas passage 9 can be straightened. This makes it possible to prevent backflow of the shielding gas, etc.

In addition, in this embodiment, a baffle plate 65 is provided between the shielding gas introduction groove 61 and the opening 64 located on the extension line of the shielding gas introduction groove 61. This makes it possible to prevent the shielding gas from flowing directly from the shielding gas introduction groove 61 to the opening 64, and also makes it possible to separate the flow of shielding gas from the shielding gas introduction groove 61 into circumferential flows in opposite directions by the baffle plate 65.

(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.

For example, instead of the first part 4 shown in FIG. 5, it is possible to adopt the first part 4A shown in FIG. 6. 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 radially 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.

In contrast, as shown in FIG. 5, if the first part 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 that connects the annular groove 42 for protective gas and the central hole 7, the flow of protective gas within the central hole 7 is straightened, making it possible to prevent backflow of the protective gas, etc.

(summary)
The nozzle tip of the present invention is a nozzle tip attached to the tip of an LMD nozzle, comprising: a tip body having a central hole for discharging a laser beam emitted from the LMD nozzle together with a protective gas, and at least one powder passage for discharging metal powder together with a carrier gas around the central hole; and a cover superimposed on the tip body, forming an annular shielding gas passage between the tip body and the cover for discharging a shielding gas around the at least one powder passage, wherein a shielding gas annular groove is formed on the contact surface of the cover with the tip body, the shielding gas being introduced into the shielding gas passage and surrounding the shielding gas passage, and the cover is provided with a partition wall separating the shielding gas annular groove and the shielding gas passage, and the partition wall is provided with a plurality of openings distributed in the circumferential direction.

According to the above configuration, an annular shielding gas groove is formed on the contact surface of the cover with the tip body, surrounding the shielding gas passage, and a partition wall separating the annular shielding gas groove from the shielding gas passage is provided with multiple openings distributed in the circumferential direction, so that the flow of shielding gas in the shielding gas passage can be straightened. This makes it possible to prevent backflow of shielding gas, etc.

For example, the tip body may include a first part that contacts the LMD nozzle and a second part that is overlaid on the first part and that, together with the first part, defines the central hole.

The cover may be formed with a shielding gas inlet groove extending radially outward from the annular shielding gas groove, one of the multiple openings being located on an extension line of the shielding gas inlet groove, and the cover may be provided with a baffle plate between the shielding gas inlet groove and the one opening. With this configuration, it is possible to prevent the shielding gas from flowing directly from the shielding gas inlet groove to the one opening, and the flow of the shielding gas from the shielding gas inlet groove can be divided into circumferential flows in opposite directions by the baffle plate.

REFERENCE SIGNS LIST 10 Laser beam 2 LMD nozzle 3, 3A, 3B Nozzle tip 30 Tip body 4 First part 5 Second part 6 Cover 61 Shielding gas inlet groove 62 Annular groove for shielding gas 63 Partition wall 64 Opening 65 Baffle plate 7 Central hole 8 Powder passage 9 Shielding gas passage

Claims (2)

A nozzle tip attached to the tip of an LMD nozzle,
a tip body having a central hole for emitting a laser beam emitted from the LMD nozzle together with a protective gas, and at least one powder passage around the central hole for emitting a metal powder together with a carrier gas;
a cover that is superimposed on the tip body and that forms an annular shield gas passage between the tip body and the cover for discharging a shield gas around the at least one powder passage;
a shielding gas annular groove is formed on a contact surface of the cover with the tip body, the shielding gas being introduced therein and surrounding the shielding gas passage;
the cover is provided with a partition wall separating the annular groove for shielding gas from the passage for shielding gas, the partition wall being provided with a plurality of openings distributed in a circumferential direction;
The cover is formed with a shielding gas introduction groove extending radially outward from the shielding gas annular groove,
One of the plurality of openings is located on an extension line of the shielding gas introduction groove,
The cover is provided with a baffle plate between the shield gas introduction groove and the one opening . The nozzle tip according to claim 1 , wherein the tip body includes a first part that abuts against the LMD nozzle, and a second part that is superimposed on the first part and defines the central hole together with the first part.

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