JP7629803B2 - LMD device - Google Patents

Description

The present invention relates to an LMD (Laser Metal Deposition) device that irradiates a laser beam onto a workpiece and supplies metal powder.

Conventionally, LMD devices have been known that irradiate a workpiece with a laser beam and supply metal powder to the irradiation position to perform build-up welding. For example, Patent Document 1 discloses an LMD device 100 as shown in FIG. 10.

Specifically, the LMD device 100 includes an LMD nozzle 110 that reflects a laser beam off a reflecting mirror 111 and emits the laser beam through a protective glass 112, and a nozzle tip 120 that is attached to the LMD nozzle 110 so as to cover the protective glass 112. The protective glass 112 is intended to prevent contamination of the reflecting mirror 111.

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

As shown in FIG. 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 spaced at equal angular intervals of 90 degrees around the central hole 121. Typically, the metal powder is discharged with a carrier gas.

International Publication No. 2010/142283

However, when overlay welding is performed using an 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.

The present invention aims to provide an LMD device that can prevent scattered metal powder from adhering to the protective glass.

In order to solve the above problem, 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 around the central hole for emitting metal powder together with a carrier gas, and is characterized in that the proximal portion of the central hole from the base end on the protective glass side to the intermediate position is an inverted cone shape that decreases in diameter as it moves away from the protective glass, and at least a portion of the distal portion from the intermediate position to the tip is a cone shape that increases in diameter as it moves away from the protective glass.

According to the above configuration, the central hole has a minimum diameter at the intermediate position, so the flow rate of the protective gas can be increased at this intermediate position. Due to the effect of this increased flow rate and the length of the distal portion from the intermediate position to the tip, it is possible to make it difficult for metal powder that collides with the work surface and scatters to pass through the distal portion. This makes it possible to prevent the scattered metal powder from adhering to the protective glass. Furthermore, since at least a portion 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 makes it possible to improve the shielding performance on the work surface compared to when the distal portion is cylindrical.

An LMD device according to another aspect of the present invention comprises an LMD nozzle that emits a laser beam through a protective glass by reflecting the laser beam 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 around the central hole for emitting metal powder together with a carrier gas, and is characterized in that the proximal portion of the central hole from the base end on the protective glass side to the intermediate position is an inverted cone shape that decreases in diameter as it moves away from the protective glass, and the distal portion from the intermediate position to the tip is cylindrical.

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 this increased flow rate and the length of the distal portion, it is possible to make it difficult for metal powder that collides with the work surface and is scattered to pass through the distal portion. Therefore, it is possible to prevent the scattered metal powder from adhering to the protective glass.

The present invention provides an LMD device that can prevent scattered metal powder from adhering to the protective glass.

1 is a cross-sectional view of an LMD device 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. 2 is a perspective view of a first part of the nozzle tip in the embodiment. FIG. 13 is a perspective view of a first part of another shape. FIG. 4 is a perspective view of a third part of the nozzle tip in the embodiment. FIG. 11 is a cross-sectional view of a modified LMD device. FIG. 11 is a cross-sectional view of another modified LMD device. FIG. 1 is a cross-sectional view of a conventional LMD device. FIG. 11 is a cross-sectional view of a nozzle tip of the LMD device shown in FIG.

Figures 1 to 4 show an LMD device 1 according to one embodiment of the present invention. This LMD device 1 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 1 includes a device body (not shown) that includes a laser oscillator that emits a laser beam 10, a rod-shaped LMD nozzle 2 extending 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. An opening 21a is provided at the tip of the nozzle body 21, and the opening 21a is blocked by protective glass 23. The protective glass 23 is attached to the nozzle body 21 via a support 24.

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.

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 the protective gas, and four powder passages 8 (see Figures 2 and 3) for emitting the metal powder together with the carrier gas around the central hole 7. Furthermore, in this embodiment, the nozzle tip 3 has an annular shielding gas passage 9 for emitting the 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 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 overlaid on the first part 4, and a third part 6 that is overlaid 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.

Although not shown, a seal material (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 third part 6 to ensure sealing.

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 third part 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 area close to the proximal portion 71 and conical in the area close to the tip. However, the distal portion 72 may be conical over its entire length, as in the modified LMD device 1A shown in FIG. 8.

For example, the diameter of the central hole 7 at the intermediate position 70 is set so that the flow velocity at the intermediate position 70 is 10 to 15 m/s when the supply flow rate of the protective gas to the central hole 7 is 2.5×10 ⁻⁴ m ³ /s.

Returning to Figures 1 to 4, it is desirable for the intermediate position 70 to be located distal to 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.

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 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 third part 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 third part 6 is provided with a partition wall 63 that separates the annular shielding gas 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.

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

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 the flow rate of the protective gas can be increased at this intermediate position. Due to the effect of this increased 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 work 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.

(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, as in the 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 in the distal portion 72, as in the previous embodiment. Due to the effect of this increased flow rate and the length of the distal portion 72, it is possible to make it difficult for metal powder that collides with the work 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.

However, if at least a portion of the distal portion 72 is conical as shown in FIG. 1 or FIG. 8, the flow rate of the protective gas can be slowed 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.

In addition, instead of the first part 4 shown in FIG. 5, it is also 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.

In addition, 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 next to the nozzle tip 3.

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 (not shown). 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.

In contrast, 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 wall 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 shielding gas in the shielding gas passage 9 is straightened, and backflow of the shielding gas can be prevented.

(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, 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 at least a portion of a distal portion from the intermediate position to the tip has a cone shape which increases in diameter as it moves away from the protective glass.

According to the above configuration, the central hole has a minimum diameter at the intermediate position, so the flow rate of the protective gas can be increased at this intermediate position. Due to the effect of this increased flow rate and the length of the distal portion from the intermediate position to the tip, it is possible to make it difficult for metal powder that collides with the work surface and scatters to pass through the distal portion. This makes it possible to prevent the scattered metal powder from adhering to the protective glass. Furthermore, since at least a portion 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 makes it possible to improve the shielding performance on the work surface compared to when the distal portion is cylindrical.

For example, the distal portion may be cylindrical near the proximal portion and conical near the tip. Alternatively, the distal portion may be conical along its entire length.

An LMD device according to another aspect of the present invention comprises an LMD nozzle that emits a laser beam through a protective glass by reflecting the laser beam 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 around the central hole for emitting metal powder together with a carrier gas, and is characterized in that the proximal portion of the central hole from the base end on the protective glass side to the intermediate position is an inverted cone shape that decreases in diameter as it moves away from the protective glass, and the distal portion from the intermediate position to the tip is cylindrical.

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 this increased flow rate and the length of the distal portion, it is possible to make it difficult for metal powder that collides with the work surface and is scattered to pass through the distal portion. Therefore, it is possible to prevent the scattered metal powder from adhering to the protective glass.

For example, the focal point of the laser beam may be located within the distal portion of the central hole.

The contact surface of the nozzle tip with the LMD nozzle is formed with a protective gas annular groove surrounding the central hole into which the protective gas is introduced, and the nozzle tip is provided with a partition wall separating the protective gas annular groove from the central hole, and a plurality of communication holes connecting the protective gas annular groove and the central hole may be provided 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 of the nozzle tip with the LMD nozzle, 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 connecting the protective gas annular groove and the central hole, the flow of the protective gas in the central hole is rectified, and the backflow of the protective gas can be prevented.

Each of the plurality of communication holes may be inclined from the protective gas annular groove toward the central hole in a direction away from the protective glass. With this configuration, the protective gas can be sprayed from the communication hole toward the tip of the central hole.

The nozzle tip has an annular shielding gas passage for discharging shielding gas around the at least one powder passage, and 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 constitutes the central hole together with the first part, and a third part that is superimposed on the second part, and the shielding gas passage is formed between the second part and the third part, and a shielding gas annular groove is formed on the contact surface of the third part with the second part, surrounding the shielding gas passage into which the shielding gas is introduced, and a partition wall is provided on the third part to separate the shielding gas annular groove and the shielding gas passage, and this partition wall may be provided with a plurality of openings distributed in the circumferential direction. If 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 multiple openings distributed in the circumferential direction, the flow of shielding gas within the shielding gas passage will be straightened, making it possible to prevent backflow of shielding gas, etc.

REFERENCE SIGNS LIST 1 LMD device 10 Laser beam 11 Focus 2 LMD nozzle 22 Reflecting mirror 23 Protective glass 3 Nozzle tip 4 First part 42 Annular groove for protective gas 43 Communication hole 44 Partition wall 5 Second part 6 Third part 62 Annular groove for shielding gas 63 Partition wall 64 Opening 7 Central hole 70 Intermediate position 71 Proximal part 72 Distal part 8 Powder passage 9 Shielding gas passage

Claims (7)

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 from the central hole, and a plurality of communication holes that connect the annular groove for protective gas with the central hole are provided at equal angular intervals around the central hole . The LMD device of claim 1, wherein the distal portion is cylindrical in a region near the proximal portion and conical in a region near the tip. The LMD device of claim 1, wherein the distal portion is conical along its entire length. 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 from the central hole, and a plurality of communication holes that connect the annular groove for protective gas with the central hole are provided at equal angular intervals around the central hole . The LMD device according to any one of claims 1 to 4, wherein the focal point of the laser beam is located within the distal portion of the central hole. 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. 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 that separates the annular groove for shielding gas from 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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