CA3130243A1 - Torch nozzle for plasma powder welding - Google Patents

Abstract

An object of the present invention is to provide a torch nozzle having a cooling structure with an enhanced cooling effect. A torch nozzle 10 according to the invention has an attachment surface 11 to be attached to a tip of a torch head for plasma powder overlay welding, and a distal end surface f12 acing a workpiece, the torch nozzle comprising an arc passing hole 20 extending through the attachment surface to the distal end surface and configured to pass therethrough a plasma arc generated by an electrode rod inserted from the attachment surface, a plurality of powder gas channels 40 arranged at intervals in the circumferential direction outside the arc passing hole and each extending through the attachment surface to the distal end surface, and a cooling water passage 50 disposed between the attachment surface and the distal end surface to surround the powder gas channels and in communication with a cooling water inlet and a cooling water outlet formed in the attachment surface, wherein the cooling water passage 50 is formed in a meander shape, and includes a first section 55 extending along an outer periphery of each of the powder gas channels, and a second section 56 positioned between each pair of the adjacent powder gas channels and extending toward the arc passing hole.

Description

TORCH NOZZLE FOR PLASMA POWDER WELDING
FIELD OF INVENTION
[0001] The present invention relates to a torch nozzle used in plasma powder welding, more specifically to a torch nozzle for plasma powder welding having an increased water quenching effect achieved by an improved cooling structure while making the size smaller.
BACKGROUND ART

[0002] Plasma powder welding is a technique for overlay welding on a workpiece by injecting powders serving as build-up materials into a plasma arc, melting the powders, and feeding the melt to the workpiece. The plasma arc is discharged toward the workpiece from an arc passing hole formed at the center of a torch nozzle attached to a tip of a torch head. The powders are discharged through powder gas channels formed around the arc passing hole, together with an inert gas such as argon gas. A shielding gas comprising an inert gas such as argon gas is supplied to the outer circumference of the torch nozzle.

[0003] The torch nozzle is heated to a very high temperatures by a plasma arc. For this reason, the torch nozzle is provided inside thereof with a cooling water passage for supplying water to cool the torch nozzle itself. (See, for example, Patent Document 1).
LIST OF PRIOR ART

[0004] Patent Document 1: JP H01-162578 Al Date Recue/Date Received 2021-09-09 PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] For the piping made up of small-diameter tubes (for example, an inner diameter of 80 mm or less), the torch head and torch nozzle must be made smaller. However, reducing the size of the torch nozzle results in an increase in thermal load, which causes an increase of spatter, an increase of works of removing the adhered spatter, and a shortened life of the torch nozzle. Accordingly, there is a need to improve the cooling effect on the torch nozzle.

[0006] An object of the present invention is to provide a torch nozzle having a cooling structure with an enhanced cooling effect.
MEANS OF SOLVING THE PROBLEMS

[0007] In one embodiment of the invention, a torch nozzle has an attachment surface to be attached to a tip of a torch head for plasma powder overlay welding, and a distal end surface facing a workpiece, the torch nozzle comprising:
an arc passing hole extending through the attachment surface to the distal end surface and configured to pass therethrough a plasma arc generated by an electrode rod inserted from the attachment surface;
a plurality of powder gas channels arranged at intervals in the circumferential direction outside the arc passing hole and each extending through the attachment surface to the distal end surface; and a cooling water passage disposed between the attachment surface and the distal end surface to surround the powder gas channels and in communication with a cooling water inlet and a cooling water outlet formed in the attachment surface;
wherein the cooling water passage is formed in a meander shape and includes a first section extending along an outer periphery of each of the powder gas channels, and a second section positioned between each pair of the adjacent powder gas channels and extending toward the arc Date Recue/Date Received 2021-09-09 passing hole.

[0008] With the torch nozzle in the embodiment mentioned above, the cooling water inlet and the cooling water outlet are positioned adjacent to each other on a concentric circle about the arc passing hole, and the cooling water passage includes an inlet-side bent portion in communication with the cooling water inlet and an outlet-side bent portion in communication with the cooling water outlet, the inlet-side bent portion and the outlet-side bent portion being bent to each other in mutually approaching directions.

[0009] In another embodiment of the invention, a torch nozzle has an attachment surface to be attached to a tip of a torch head for plasma powder overlay welding, and a distal end surface facing a workpiece, the torch nozzle comprising:
an arc passing hole extending through the attachment surface to the distal end surface and configured to pass therethrough a plasma arc generated by an electrode rod inserted from the attachment surface;
a plurality of powder gas channels arranged at intervals in the circumferential direction outside the arc passing hole and each extending through the attachment surface to the distal end surface; and a cooling water passage disposed between the attachment surface and the distal end surface to surround the powder gas channels and in communication with a cooling water inlet and a cooling water outlet formed in the attachment surface, wherein the cooling water inlet and the cooling water outlet are positioned adjacent to each other on a concentric circle about the arc passing hole, the cooling water passage includes an inlet-side bent portion in communication with the cooling water inlet and an outlet-side bent portion in communication with the cooling water outlet, and the inlet-side bent portion and the outlet-side bent portion are bent to each other in mutually approaching directions.

[0010] With the torch nozzle in another embodiment, the cooling water passage extends annularly around the arc passing hole.

Date Recue/Date Received 2021-09-09

[0011] With the torch nozzle in the foregoing embodiments, the cooling water inlet and the cooling water outlet are positioned between a pair of the adjacent powder gas channels.

[0012] With the torch nozzle in the foregoing embodiments, the cooling water passage has an inner surface provided with an agitation member configured to stir a cooling water flow.

[0013] A torch head is provided at a tip thereof with the torch nozzle as mentioned above.
ADVANTAGEOUS EFFECTS OF THE INVENTION

[0014] According to the torch nozzle of the present invention, the cooling water passage is formed in a meander shape and includes a section extending toward the arc passing hole, so that peripheral edges of the arc passing hole can be effectively cooled even if heated to high temperatures.

[0015] In addition, according to the torch nozzle of the present invention, the cooling water passage comprises an inlet-side bent portion in communication with the cooling water inlet and an outlet-side bent portion in communication with the cooling water outlet, wherein the inlet-side and outlet-side bent portions are bent in mutually approaching directions, so that the portion between the cooling water inlet and the cooling water outlet can be effectively cooled.

[0016] With the torch nozzle of the present invention, the cooling water passage has the shape as mentioned above. Therefore, the torch nozzle is featured with sufficient cooling ability even if made smaller. The torch nozzle of the present invention has advantages in that an increase in the thermal load of the torch nozzle is suppressed, the spatter is reduced, the works of removing the adhered spatter is alleviated, and the longer life of the torch nozzle is attained.

Date Recue/Date Received 2021-09-09 BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is a perspective view of a torch nozzle according to one embodiment of the invention, when viewed from an attachment surface side.
FIG. 2 is a plan view of the torch nozzle.
FIG. 3 is a front view of the torch nozzle.
FIG. 4 is a bottom view of the torch nozzle.
FIG. 5 shows sectional views of the torch nozzle, wherein 5 (a) to 5 (c) are views taken along the lines A-A, B-B, and C-C shown in FIG. 2, respectively.
FIG. 6 shows sectional views of the torch nozzle, wherein 6 (d) and 6 (e) are views taken along the lines D-D and E-E shown in FIG. 3, respectively.
FIG. 7 shows sectional views of the torch nozzle, wherein 7 (f) and 7 (g) are views taken along the lines F-F and G-G shown in FIG. 2, respectively.
FIG. 8 shows sectional views of the torch nozzle having four agitation members provided in the cooling water passage, wherein 8 (c), 8 (d), and 8 (e) are views taken along the line C-C
shown in FIG. 2, the line D-D shown in FIG. 3, and the line E-E shown in FIG.
3, respectively.
Date Recue/Date Received 2021-09-09 FIG. 9 shows sectional views of the torch nozzle having two agitation members provided in the cooling water passage, wherein 9 (c), 9 (d), and 9 (e) are views taken along the line C-C
shown in FIG. 2, the line D-D shown in FIG. 3, and the line E-E shown in FIG.
3, respectively.
FIG. 10 shows sectional views of the torch nozzle having the cooling water passage in a circular shape prepared for the comparison purpose, wherein 10 (c), 10 (d), 10 (e), and 10 (f) are views taken along the line C-C shown in FIG. 2, the line D-D shown in FIG. 3, the line E-E shown in FIG. 3, and the line F-F shown in FIG. 2, respectively.
FIG. 11 shows temperature distribution diagrams of the torch nozzles of the Inventive Example 3 and the reference example provided in the first embodiment, wherein 11 (a) shows temperature distributions of a cross section taken along the line A-A shown in FIG. 2, 11 (f3) shows temperature distributions of the entire of the distal end surface, and 11(y) shows enlarged temperature distributions of an evaluation surface at the center of the distal end surface.
MODE FOR CARRYING OUT THE INVENTION

[0018] A torch nozzle 10 of one embodiment of the present invention will be described below with reference to the drawings.

[0019] The torch nozzle 10 is a device loaded on a torch head (not shown) used in plasma powder welding. The torch head has a protruded electrode rod usually made of tungsten. The torch head comprises a plurality of powder gas feeding ports, a cooling water supply port for supplying the cooling water, a cooling water collection port for collecting the cooling water, and a Date Recue/Date Received 2021-09-09 shielding gas feeder for feeding the shielding gas. The torch head has four powder-feeding ports at intervals of 75 to 105 around its circumference, with the electrode rod at the center, and is provided between adjacent powder-feeding ports with the cooling water supply port and the cooling water collection port. This structure of the torch head will be understood from the arrangement of the attachment surface 11 of the torch nozzle 10, which will be described below. The structure of the torch head and the positions and number of the feeding ports are not limited to those described above.

[0020] FIG. 1 is a perspective view of the torch nozzle 10 when viewed from the attachment surface 11 to be loaded on the torch head. FIG. 2 is a plan view of the torch nozzle 10, with the attachment surface 11 facing upward. FIG. 3 is a front view of the torch nozzle 10. FIG. 4 is a bottom view of the torch nozzle 10 when viewed from a distal end surface 12 facing a workpiece.
FIG. 5 includes sectional views taken along the lines A-A to C-C shown in FIG.
2. FIG. 6 includes sectional views taken along the lines D-D and E-E shown in FIG. 3.
FIG. 7 includes sectional views taken along the lines F-F and G-G shown in FIG. 2.

[0021] The torch nozzle 10 can be made of a material such as chromium copper and is formed into a shape described below using a 3D printer. The material and the manufacturing method of the torch nozzle 10 are not limited to them.

[0022] As shown in FIG. 1 and other figures, the torch nozzle 10 may be formed into a cylindrical column having a forward end with a slightly tapered shape. An electrode rod of the torch head can be inserted into a central portion on the top face of the torch nozzle, which serves as an attachment surface 11 to be loaded on the torch head. The attachment surface 11 is formed with an arc passing hole 20 in shape tapered toward the distal end surface 12 as shown in FIGS. 5 (a) to 5 (c). As shown in FIG. 4, the arc passing hole 20 extends through the torch nozzle 10 and is opened in the distal end surface 12.

[0023] The attachment surface 11 has a flange extending outwardly from the outer periphery Date Recue/Date Received 2021-09-09 thereof and is formed with a plurality of shielding gas paths 30 to flow a shielding gas. In the illustrated embodiment, the shielding gas paths 30 are recesses formed in the flange of the attachment surface 11. When the torch nozzle 10 is loaded on the torch head, the shielding gas flow paths 30 communicate with a shielding gas feeder and supply the shielding gas. The shielding gas flow paths 30 may be through-holes.

[0024] As shown in FIGS. 1, 2, and 5 (c), the arc passing hole 20 is formed therearound with powder gas channels 40 (individual powder gas channels are indicated by reference numerals 40a, 40b, 40c, and 40d in the figures) at an interval of 750 to 105 . The powder gas channels 40a, 40b, and the powder gas channels 40c, 40d are opened in the bottom of curve-shaped recesses 41, 41 formed in the attachment surface 11. The recesses 41, 41 are connected to the powder gas feeding ports formed in the torch head. Each of the powder gas channel 40 is inclined toward the central portion of the arc passing hole 20 from the attachment surface 11 to the distal end surface 12 and is opened in the vicinity of the arc passing hole 20 on the side of the distal end surface 12, as shown in FIG. 4.

[0025] The attachment surface 11 of the torch nozzle 10 includes a cooling water inlet 51 and a cooling water outlet 52 in communication with a cooling water passage 50. In the embodiments illustrated in FIGS. 1 and 2, the cooling water inlet 51 and the cooling water outlet 52 are respectively formed in the bottom of gasket attachment recesses 51a and 52a of the attachment surface 11, and may be connected to the cooling water supply port and the cooling water collection port of the torch head, via gaskets mounted on the recesses 51a and 52a.

[0026] The cooling water passage 50 is provided within the torch nozzle 10 to extend along the outside the arc passing hole 20 and the powder gas channels 40. The cooling water is supplied to the cooling water passage 50 from the cooling water supply port of the torch head via the cooling water inlet 51 to cool the torch nozzle 10, and is discharged from the cooling water outlet 52 to the cooling water collection port.

Date Recue/Date Received 2021-09-09

[0027] The cooling water inlet 51 and the cooling water outlet 52 are preferably provided adjacent to each other between a pair of the powder gas channels 40a and 40d, on a concentric circle thereabout. As the cooling water inlet 51 and the cooling water outlet 52 are provided between the powder gas channels 40a and 40d, the cooling water inlet 51 and the cooling water outlet 52 can be positioned closer to the arc passing hole 20, so that the cooling effect on the torch nozzle 10 is increased.

[0028] As shown in FIGS. 6 (d) and 6 (e), in more detail in FIGS. 7 (f) and 7 (g), the inside of the cooling water inlet 51 has an inlet-side bent portion 53 and the cooling water outlet 52 has an outlet-side bent portion 54, and the inlet-side and outlet-side bent portions 53, 54 are bent to each other in mutually approaching directions. The inlet-side bent portion 53 is a flow path extending from the cooling water inlet 51 toward the distal end surface 12, and is bent toward the outlet-side bent portion 54 in a substantial dogleg shape, as shown in the illustration.
Likewise, the outlet-side bent portion 54 is a flow path extending from the cooling water outlet 52 toward the distal end surface 12, and is bent toward the inlet-side bent portion 53 in a substantial dogleg shape, as shown in the illustration. The cooling water inlet 51 and the cooling water outlet 52 are required to have a distance therebetween to connect to the cooling water supply and cooling water collection ports of the torch head, resulting in a decrease of the cooling ability between the cooling water inlet 51 and the cooling water outlet 52. According to the present embodiment, the inlet-side bent portion 53 and the outlet-side bent portion 54 create a flow path of the cooling water between the cooling water inlet 51 and the cooling water outlet 52 to provide an increased cooling ability.

[0029] As described above, the cooling water passage 50 positioned between the cooling water inlet 51 and the cooling water outlet 52 extends around the arc passing hole 20 and along the outer periphery of the powder gas channels 40. In the torch nozzle 10, the arc passage hole 20 receives heat generated by an arc and is heated in a region therearound. If the cooling water passage 50 is located at a position closer to the arc passing hole 20, the cooling effect on the torch nozzle 10 can be increased, accordingly. With the present invention, the cooling water passage 50 is formed in a meander shape to extend a position closer to the arc passing hole 20 as shown in the cross-sectional views in FIGS. 6 (d) and 6 (e), instead of an annular shape. Specifically, the cooling water passage 50 may comprise a first section 55 extending along an outer periphery of each of the powder gas channels 40, and a second section 56 extending toward the arc passing hole 20, wherein the first and Date Recue/Date Received 2021-09-09 second sections 55, 56 are continued. With reference to the longitudinal sectional view of the torch nozzle 10, as seen in FIG. 5 (c), the first section 55 of the cooling water passage 50 is located outside the powder gas channel 40 and runs near the circumference of the torch nozzle 10. As seen in FIGS. 5 (a) and 5 (b), the second section 56 of the cooling water passage 50 is located between powder gas channels 40 and runs in the vicinity of the arc passing hole 20, i.e., near a position closer to an inner circumference of the arc passing hole 20.

[0030] As described above, the cooling water passage 50 formed in a meander shape provides a direct cooling for the region heated to high temperatures in the arc passing hole 20, thus increasing the cooling ability to the torch nozzle.

[0031] In a more preferable embodiment, the cooling water passage 50 is formed such that the flow path is positioned as close as possible to the arc passing hole 20 and the wall of the flow path on the arc passing hole 20 side has a large area while ensuring the strength required for the torch nozzle 10. In the illustrated embodiment as shown in FIG. 5 (c), the first section 55 of the cooling water passage 50 includes, on the inner circumferential side, an inclined surface that conforms to the incline of the powder gas channel 40, and also includes, on the outer circumferential side, a surface that is partially recessed on the distal end surface 12 side and shaped to conform to the shape of the circumferential face of the torch nozzle 10. The second section 56 includes an inclined surface that conforms to the shape of the arc passing hole 20, as shown in FIG. 5 (a). This feature makes the cross-sectional area of the cooling water passage 50 larger, makes the flow resistance of cooling water in the flow path smaller and allows as much cooling water as possible to be distributed to increase the cooling ability. The torch nozzle 10 that includes the cooling water passage 50 described above may be produced preferably using a 3D printer.

[0032] In the embodiment shown in FIGS. 1 to 7, the cooling water passage 50 is configured to communicate the inlet-side bent portion 53 and the outlet-side bent portion 54 with the cooling water inlet 51 and the cooling water outlet 52, respectively, and is formed in a meander shape Date Recue/Date Received 2021-09-09 including the first section 55 extending along the outer periphery of the powder gas channel 40 and the second section extending toward the arc passing hole 20 at between the powder gas channels 40.
This is the best mode of the present invention. In another embodiment, the inlet-side bent portion 53 and the outlet-side bent portion 54 may be connected by a cooling water passage in an annular shape, although the cooling ability may slightly drops. Alternatively, the cooling water passage 50 may be formed in a meander shape with the first section 55 and the second section 56 free from the inlet-side bent portion 53 and the outlet-side bent portion 54.

[0033] With the torch nozzle 10 of the present invention, the cooling water passage 50 formed as described above can perform heat exchange with cooling water effectively to increase the cooling effect on the torch nozzle 10. The torch nozzle 10, even if downsized, has an improved cooling ability, prevents an increase in the thermal load between the torch nozzle 10 and the torch head, reduces spatter, decreases works of removing the adhered spatter, and achieves a longer life of the torch nozzle.

[0034] <Variation of Embodiments>
The cooling ability is further increased by stirring the flow of cooling water flowing through the cooling water passage 50 to form a flow of cooling water colliding with the inner surface of the cooling water passage 50. To implement this flow, one or more agitation members 60 may be provided in the cooling water passage 50, as shown in FIGS. 8 and 9.
The agitation members 60 may be in the form of a fin, a baffle plate, or a protrusion.

[0035] FIG. 8 shows an embodiment in which four agitation members 60 are provided, and FIG.
9 shows an embodiment in which two agitation members 60 are provided. A
plurality of agitation members 60 causes the water in the cooling water passage 50 to stir unifoimly to increase the cooling ability.

[0036] In the case where only one agitation member 60 is provided, the agitation member 60 is preferably formed at a position close to the cooling water inlet 51. The agitation member 60 provided on the upstream side is advantageous in that the stirring effect can be maintained longer Date Recue/Date Received 2021-09-09 throughout the cooling water passage 50 (even in the midstream and the downstream side), as compared with the case where the agitation member 60 is provided in the midstream or on the downstream side.

[0037] To increase the cooling ability, the cooling water passage 50 may include, in addition to the first section 55 extending around each powder gas channel 40, a cooling water passage that runs between the inner circumferential side of the powder gas channel 40 and the arc passing hole 20.
In the case where the inlet-side bent portion 53 and the outlet-side bent portion 54 are connected by an annular-shaped cooling water passage, the cooling water passage 50 may comprise a single flow path that runs on the inner circumferential side of the powder gas channels 40.

[0038] The foregoing embodiments are merely to explain the present invention and should not be construed to limit the invention defined in the appended claims or narrow the scope of the present invention. Also, the structural elements of the present invention are not limited to those described in the embodiment given above, and various modifications can be, of course, made within the technical scope recited in the appended claims.

[0039] For example, the outer shape of the torch nozzle 10, the shape of the arc passing hole 20, the shape of the powder gas channels 40, and the number of powder gas channels

40 are, of course, not limited to those of the embodiment given above. Also, the sectional shape of the cooling water passage 50, the meander shape of the cooling water passage 50, and the like are not limited to the embodiments given above. The meander shape of the cooling water passage 50 is not only formed in a plane parallel to the attachment surface 11 but also may be formed in an up-down direction perpendicular to the attachment surface 11.
EXAMPLES
[0040] Torch nozzles were produced as described below to compare the cooling effect on the Date Recue/Date Received 2021-09-09 torch nozzles. The torch nozzles were produced by a 3D printer using a chromium copper powder (with a specific heat at constant pressure of 385 J/kg=K and a thermal conductivity of 324 W/m=K).

[0041] <First Embodiment>
The Inventive Example 1 is an example of a cooling water passage 50 that comprises an inlet-side bent portion 53 and an outlet-side bent portion 54 provided in a cooling water inlet 51 and a cooling water outlet 52, respectively. The cooling water passage 50 between the inlet-side bent portion 53 and the outlet-side bent portion 54 is an annular shape and runs outside powder gas channels 40. This example relates to only the "bent portion."

[0042] Inventive Example 2 is a cooling water passage 50 that is formed in a meander shape, and includes a first section 55 extending along an outer periphery of powder gas channels 40 and a second section extending toward an arc passing hole 20 at between adjacent powder gas channels 40. This example relates to only the "meander shape" without the "bent portion."

[0043] Inventive Example 3 is an example of a cooling water passage 50 that comprises an inlet-side bent portion 53 and an outlet-side bent portion 54 provided in a cooling water inlet 51 and a cooling water outlet 52, respectively, and is formed in a meander shape and includes a first section 55 extending along an outer periphery of powder gas channels 40 and a second section 56 extending toward an arc passing hole 20 at between adjacent powder gas channels. This example is shown in FIGS. 1 to 7 and relates to both "bent portion" and the "meander shape." The sectional view of the cooling water passage 50 is shown in FIGS. 5 to 7.

[0044] Reference Example shown in FIG. 10 is provided as an example of a torch nozzle 70 prepared for the purpose of comparison wherein a cooling water inlet 72 and a cooling water outlet 73 were connected directly to an annular cooling water passage 71. This example does not include both the "bent portion" and the "meander shape." The sectional view of the cooling water passage 71 is substantially triangle shape, as shown FIG. 10 (c).

Date Recue/Date Received 2021-09-09

[0045] The arc passing hole 20 of the torch nozzle 10 in Inventive Examples 1 to 3 and Reference Example was heated to 1000 C. Cooling water at a temperature of 15 C
was supplied from the cooling water inlet at a flow rate of 500 liters/h. With regard to the distal end surface 12, a circular region surrounding the powder gas channels 40 is identified as an evaluation surface 13 (See FIG. 11). The average temperature of the evaluation surface and the temperature of the cooling water discharged from the cooling water outlet were measured. The lower the average temperature of the evaluation surface, the higher the cooling ability, and the higher the temperature of the discharged cooling water, the higher the cooling ability, because heat exchange between the torch nozzle and cooling water is performed effectively. The results are shown in Table 1. The temperature distribution diagrams of Inventive Example 3 and Reference Example are shown in FIG. 11, wherein FIG. 11 (a) shows temperature distributions of a cross-section taken along the line A-A shown in FIG. 2, FIG. 11 (fl) shows temperature distributions of the entire distal end surface 12, and FIG. 11(y) shows enlarged temperature distributions of the evaluation surface 13 at the center of the distal end surface 12.

[0046]
[Table 1]
Inventive Example 1 Inventive Example 2 Inventive Example 3 Reference Example With bent portion and Without bent portion Feature With bent portion With meander shape meander shape and meander shape Average temperature of evaluation surface ( C) Temperature of discharged 33 33.9 34.3 32.8 cooling water ( C) Date Recue/Date Received 2021-09-09

[0047] Referring to Table 1, Inventive Example 1 indicates that the average temperature of the evaluation surface decreased by 23 C, and the temperature of the discharged cooling water increased by 0.2 C, as compared to Reference Example. In Inventive Example 1, the cooling water passage includes an inlet-side bent portion and an outlet-side bent portion in the cooling water passage. As there is formed the cooling water flow path between the cooling water inlet and the cooling water outlet, a non-cooled region is not present therebetween.

[0048] Referring again to Table 1, Inventive Example 2 indicates that the average temperature of the evaluation surface decreased by 91 C, and the temperature of the discharged cooling water increased by 1.1 C, as compared to Reference Example. In Inventive Example 1, the cooling water passage is formed in a meander shape and includes a section extending toward the arc passing hole, thus cooling the vicinity of the arc passing hole.
In addition, a comparison of Inventive Examples 1 and 2 indicates that the meander shape of the cooling water passage in Example 2 provides a cooling effect more significant than that of Inventive Example 1.

[0049] A comparison of Inventive Example 3 with Reference Example is made with reference to FIG. 11. In FIG. 11, a dark color portion close to the arc passing hole 20 has a temperature of about 750 C to 1000 C, a light color portion in the vicinity of the powder gas channels 40 has a temperature of about 400 C to 750 C, and the outer circumferential side of the evaluation surface 13 has a temperature of about 150 C to 400 C.
With reference to FIG. 11(a), Inventive Example 3 comprising the section 56 extending toward the arc passing hole 20 shows a decrease of the temperature of the region in the vicinity of the arc passing hole 20. Inventive Example 3 comprising the inlet-side bent portion and the outlet-side bent portion (not illustrated) shows a decrease of the temperature of the region opposing the section 56 across the arc passing hole 20.
Date Recue/Date Received 2021-09-09 FIGS. 11 (P.) and 11 (y) also show that a decrease of the temperature was achieved in both the distal end surface 12 and the evaluation surface 13.

[0050] Furthermore, as can be taken from Table 1, Inventive Example 3 exhibited excellent cooling ability than Reference Example and Inventive Examples 1 and 2. This is due to the synergistic effect of providing an inlet-side bent portion and an outlet-side bent portion and forming the cooling water passage in a meander shape. Accordingly, it can be said that the embodiment of Inventive Example 3 is the best mode of the invention.

[0051] <Second Embodiment>
Torch nozzles having agitation members 60 formed in the cooling water passage 50 of Inventive Example 3 were prepared as Inventive Examples 4 and 5. The cooling water passage in Example 4 is formed with four agitation members 60, as shown in FIG. 8. The cooling water passage in Example 5 is formed with two agitation members 60, as shown in FIG.
9. Examples 4 and 5 were compared with the torch nozzle of Inventive Example 3 without agitation members, with respect to the cooling ability based on the average temperature of the evaluation surface and the temperature of the discharged cooling water.
The heating temperature of the torch nozzle and the temperature of the cooling water supplied were the same as those of the First Embodiment. The agitation members 60 were formed in the first section 55 as shown in FIGS. 8 and 9 The results are shown in Table 2.

[0052]
[Table 2]

Date Recue/Date Received 2021-09-09 Inventive Example 3 Inventive Example 4 Inventive Example 5 Number of agitation 0 4 2 members Average temperature of evaluation surface ( C) Temperature of discharged 34.3 34.6 34.5 cooling water ( C)

[0053] Table 2 shows that the cooling ability is enhanced by the presence of the agitation members disposed in the cooling water passage. The cooling ability of Example 4 having four agitation members is superior to that of Example 5 having two agitation members because there is occurred more collision of the cooling water with the cooling water passage, which results in more agitation.

[0054] <Third Embodiment>
Torch nozzles having one single agitation member 60 formed at different positions in the cooling water passage 50 of Inventive Example 3 were prepared as Inventive Examples 6-10. The agitation member in Example 6 is disposed in the inlet-side bent portion 53.
The agitation member in Example 7 is disposed on the upstream, i.e., in the section immediately under the inlet-side bent portion 53 (indicated as 55a in FIG. 8). The agitation member in Example 8 is disposed on the midstream, i.e., in the section immediately under the inlet-side bent portion 55a (indicated as 55b in FIG. 8). The agitation member in Example 9 is disposed on the downstream, i.e., in the section immediately above the outlet-side bent portion 54 (indicated as 55d in FIG 8). The agitation member in Example 10 is disposed in the outlet-side bent portion 54.
The cooling ability of Examples 6-10 was compared based on the average temperature of the evaluation surface. The heating temperature of the torch nozzle and the temperature of supplied cooling water were the same as those of the First Embodiment. The results are shown in Table 3.

Date Recue/Date Received 2021-09-09

[0055]
[Table 3]
Inventive Example 3 Inventive Example 6 Inventive Example 7 Inventive Example 8 Inventive Example 9 Inventive Example 10 Position of agitation No agitation member In inlet-side bent In outlet-side bent Upstream Midstream Downstream member portion portion Average temperature of evaluation surface ( C)

[0056] Table 3 shows that the cooling ability of Examples 6-10 are superior to that of Example 3 without agitation member. A comparison between Examples 6-10 exhibits that the highest cooling ability is achieved by Example 8 wherein the agitation member is disposed in the midstream of the cooling water passage.
Example 6 wherein the agitation member was disposed in the inlet-side bent portion and Example 7 wherein the agitation member was disposed on the upstream were inferior to Example 8 with respect to the cooling ability. The reason for this could be due to that the cooling water flowing from the torch head enters the torch nozzle while changing the direction of flow at the inlet-side bent portion, and the cooling water is stirred, and thus the agitation effect provided by the agitation member is small. On the other hand, the agitation member disposed in the midstream of the cooling water passage as in Example 8 serves to stir the cooling water again during passing through the meander-shaped path, thus improving the cooling ability effect over the entire of the cooling water passage.
Example 9 wherein the agitation member was disposed on the downstream and Example wherein the agitation member was disposed in the outlet-side bent portion are observed to have the cooling effect provided by the presence of the agitation member. However, these Examples cannot achieve a higher cooling effect than in Example 8. The agitation member, if disposed in the cooling water passage, is preferably in the midstream, in more particular, at a position 1/4 to 3/4 of the cooling water passage from the upstream side of the cooling water passage, and more preferably at a position 1/3 to 2/3 of the cooling water passage from the upstream side of the cooling water passage.

Date Recue/Date Received 2021-09-09

Claims (7)

WHAT IS CLAIMED IS:

1. A torch nozzle having an attachment surface to be attached to a tip of a torch head for plasma powder overlay welding, and a distal end surface facing a workpiece, the torch nozzle comprising:
an arc passing hole extending through the attachment surface to the distal end surface and configured to pass therethrough a plasma arc generated by an electrode rod inserted from the attachment surface;
a plurality of powder gas channels arranged at intervals in the circumferential direction outside the arc passing hole and each extending through the attachment surface to the distal end surface; and a cooling water passage disposed between the attachment surface and the distal end surface to surround the powder gas channels and in communication with a cooling water inlet and a cooling water outlet formed in the attachment surface, wherein the cooling water passage is formed in a meander shape and includes a first section extending along an outer periphery of each of the powder gas channels, and a second section positioned between each pair of the adjacent powder gas channels and extending toward the arc passing hole.

2. The torch nozzle according to claim 1, wherein the cooling water inlet and the cooling water outlet are positioned adjacent to each other on a concentric circle about the arc passing hole, the cooling water passage includes an inlet-side bent portion in communication with the cooling water inlet and an outlet-side bent portion in communication with the cooling water outlet, and the inlet-side bent portion and the outlet-side bent portion are bent to each other in mutually approaching directions.

3. A torch nozzle having an attachment surface to be attached to a tip of a torch head for plasma powder overlay welding, and a distal end surface facing a workpiece, the torch nozzle comprising:
an arc passing hole extending through the attachment surface to the distal end surface and configured to pass therethrough a plasma arc generated by an electrode rod inserted from the attachment surface;
a plurality of powder gas channels arranged at intervals in the circumferential direction Date Recue/Date Received 2021-09-09 outside the arc passing hole and each extending through the attachment surface to the distal end surface; and a cooling water passage disposed between the attachment surface and the distal end surface to surround the powder gas channels and in communication with a cooling water inlet and a cooling water outlet formed in the attachment surface, wherein the cooling water inlet and the cooling water outlet are positioned adjacent to each other on a concentric circle about the arc passing hole, the cooling water passage includes an inlet-side bent portion in communication with the cooling water inlet and an outlet-side bent portion in communication with the cooling water outlet, and the inlet-side bent portion and the outlet-side bent portion are bent to each other in mutually approaching directions.

4. The torch nozzle according to claim 3, wherein the cooling water passage extends ammlarly around the arc passing hole.

5. The torch nozzle according to any one of claims 1 to 4, wherein the cooling water inlet and the cooling water outlet are positioned between a pair of the adjacent powder gas channels.

6. The torch nozzle according to any one of claims 1 to 5, wherein the cooling water passage has an inner surface provided with an agitation member configured to stir a cooling water flow.

7. A torch head provided at a tip thereof with the torch nozzle according to any one of claims 1 to 6.
Date Recue/Date Received 2021-09-09