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To protect the collimator of a transferred plasma arc torch from premature failure due to corrosion, an anti-corrosive covering is applied on the exposed face surface and a portion of the inner exit bore of the collimator. The specification describes several methods for producing the collimator for

To protect the collimator of a transferred plasma arc torch from premature failure due to corrosion, an anti-corrosive covering is applied on the exposed face surface and a portion of the inner exit bore of the collimator. The specification describes several methods for producing the collimator for a plasma torch having an anti-corrosive coating or cladding on the exposed surfaces thereof, including electroplating, electroless plating, flame spraying, plasma spraying, plasma transferred arc, hot isostatic pressing and explosive cladding.

대표청구항 ▼

What is claimed is: 1. In a plasma arc torch of the type having a tubular rear housing section with a cylindrical rear electrode mounted coaxially within the tubular rear housing, said cylindrical rear electrode having a closed inner and an open outer end, an annular vortex generator member dispose

What is claimed is: 1. In a plasma arc torch of the type having a tubular rear housing section with a cylindrical rear electrode mounted coaxially within the tubular rear housing, said cylindrical rear electrode having a closed inner and an open outer end, an annular vortex generator member disposed adjacent the outer end of the rear electrode and a front electrode adjacent a collimating nozzle with an exposed face surface and an inner exit bore therethrough, the collimating nozzle releasably coupled to the tubular rear housing in coaxial alignment with said rear electrode and the vortex generator member, the improvement comprising: (a) an anti-corrosive cladding layer on the exposed face surface of the collimating nozzle, the cladding layer being a metal alloy of a predetermined thickness sufficient to preclude penetration by a secondary arcing at torch operating power levels in excess of 500 KW. 2. The plasma arc torch as in claim 1 and further including an anti-corrosive metal alloy cladding layer on a portion of the inner exit bore of the collimating nozzle. 3. The plasma arc torch as in claim 1 wherein one of the front electrode and collimating nozzle is a copper alloy. 4. The plasma arc torch as in claim 1 wherein the cladding layer is an anti-corrosive alloy applied in one of a flame spray, a plasma spray and a hot isostatic press process. 5. The plasma arc torch as in claim 4 wherein the anti-corrosive alloy comprises one of a nickel-based alloy and a chromium-based alloy. 6. The plasma arc torch as in claim 2 wherein the cladding layer is applied in one of a plasma transferred arc process, an explosion cladding process, a hot isostatic press process and a laser cladding process. 7. The plasma arc torch as in claim 6 wherein the cladding layer comprises corrosion-resistant alloys selected from a group consisting of nickel and chrome alloys. 8. The plasma arc torch as in claim 2 wherein the collimating nozzle comprises: (a) a holder having a generally cylindrical wall and a central longitudinal bore extending therethrough with a counter-bore formed inwardly from one end thereof and a plurality of radial bores extending through the wall in fluid communication with the central bore; (b) a tubular insert having a lumen and dimensioned to fit within said central bore with a predetermined clearance space between the central bore and an outer diameter of the insert, the tubular insert including a circular flange at a distal end thereof surrounding said lumen; and (c) a weld joining a peripheral surface of the circular flange to the holder in the counter-bore such that a face of the circular flange and an exposed surface of the holder together define said exposed face surface and said portion of the inner exit bore of the collimating nozzle. 9. The plasma arc torch as in claim 8 wherein the holder and insert each comprise a copper alloy. 10. The plasma arc torch as in claim 9 wherein the anti-corrosive metal alloy cladding layer on the exposed face surface and said portion of the inner exit bore of the copper collimating nozzle is applied in one of a plasma transferred arc welding process, an explosion bonding process, a hot isostatic pressing process and a laser welding process. 11. The plasma arc torch as in claim 6 wherein the cladding layer comprises one of a nickel alloy and chromium alloy. 12. A method of manufacturing a collimating nozzle for a plasma arc torch, comprising the steps of: (a) machining a holder member from a cylindrical block of copper where the holder member includes a cylindrical outer wall and a longitudinal bore extending therethrough with a counter-bore formed inwardly from one end thereof, and a plurality of radial bores extending through the wall in fluid communication with the central bore; (b) machining a tubular insert member from a block of copper, the tubular insert member having a lumen and dimensioned to fit within said longitudinal bore of the holder member with a predetermined clearance space between the longitudinal bore and an outer diameter of the insert member, the tubular insert member further comprising a circular flange at one end thereof surrounding the lumen; (c) inserting the tubular insert member into the longitudinal bore of the holder member with the circular flange disposed in said counterbore; (d) creating a continuous weld between a periphery of the flange and a wall defining the counterbore; and (e) cladding a predetermined exposed surface of the assembly of step (d) and at least a portion of a wall defining the lumen of the insert member with an anti-corrosive alloy layer having a predetermined thickness sufficient to preclude penetration by secondary arcing at torch operating power levels in excess of 500 KW. 13. The method as in claim 12 wherein the covering material is applied in a hot isostatic press process. 14. A method of manufacturing a collimating nozzle for a plasma arc torch comprising the steps of: (a) machining a holder member from a copper block, said holder member comprising a tubular portion having first and second ends and with a lumen extending therebetween; (b) machining an insert member from a copper block, said insert member having a tubular portion with first and second ends and a lumen extending therebetween, the tubular portion having an outer diameter that is less than a diameter of said lumen of the holder member and a generally circular flange having a face extending radially proximate said first end, the flange ending in a peripheral edge offset from said face; (c) inserting the tubular portion of the insert member within the lumen of the holder member; (d) welding the perpendicular edge of the insert member to the holder member at a location offset of said face and between the first and second ends of the holder member; and (e) cladding the face and a predetermined portion of said lumen of the insert member with a layer of material exhibiting a greater corrosion resistance than copper and of a predetermined thickness precluding penetration of the cladding layer by secondary arcing through to the copper. 15. The method as in claim 14 wherein the covering material is applied in one of a flame spraying process, a plasma spraying process and a hot isostatic press process. 16. A method of manufacturing a collimator nozzle for a plasma arc torch comprising the steps of: (a) providing a first copper billet; (b) cladding a predetermined surface of the first copper billet with a corrosion resistant metallic material to a desired thickness sufficient to resist secondary arc penetration at intended operating power levels in excess of 500 KW; (c) providing a second copper billet; (d) cladding a predetermined surface of the second copper billet with said corrosion resistant metallic material to a desired thickness; (e) machining the first copper billet to form a holder member, the holder member including a generally cylindrical outer wall and a central bore of a first predetermined diameter passing longitudinally through the first copper billet, a counterbore of a second predetermined diameter extending through the cladding on the predetermined surface of the first copper billet and a plurality of radial bores oriented oblique to a longitudinal axis of the first copper billet, said radial bores extending from the outer wall to the central bore; (f) machining the second copper billet to form an insert member, the insert member including a tubular stem of generally circular cross-section and first and second ends with a lumen extending therebetween, the outer diameter of the stem being less than a diameter of the central bore of the first copper billet and a radially extending flange at said first end surrounding the lumen where the flange has a diameter generally equal to the second predetermined diameter of the counterbore of the holder member; (g) inserting the insert member into the counterbore of the holder member with the flange disposed in the counterbore; and (h) forming a continuous weld along a joint between a periphery of the flange and the wall in the holder member defining the counterbore. 17. The method as in claim 16 wherein the cladding steps comprise: (a) placing plates of the corrosion resistant metallic material on the first and second copper billets; and (b) fusion bonding the plates to the billets using a hot isostatic pressing process. 18. The method as in claim 16 wherein the cladding comprises one of a nickel alloy and a chromium alloy. 19. The method as in claim 16 wherein the cladding step includes depositing said corrosion resistant metallic material to said predetermined thickness in a plasma transferred arc process. 20. A method of manufacturing a collimator nozzle for a plasma arc torch, comprising the steps of: (a) providing a first copper billet; (b) providing a second copper billet; (c) cladding a predetermined surface of the second copper billet with said corrosion resistant metallic material to a desired thickness; (d) machining the first copper billet for forming a holder member, the holder member comprising a tubular portion having first and second ends with a lumen extending therebetween; (e) machining the second copper billet and cladding to form an insert member, the insert member having a tubular portion with first and second ends and a lumen extending therebetween, the tubular portion having an outer diameter that is less than a diameter of the lumen of the holder member and a generally circular flange having a face including the predetermined surface extending radially proximate the first end of the tubular portion of the insert member, the flange ending in a peripheral edge offset from said predetermined surface; (f) inserting the tubular portion of the insert member within the lumen of the holder member; and (g) welding the peripheral edge on the flange to the holder member at a location offset of said face and between the first and second ends of the holder member. 21. The method as in claim 20 wherein the cladding steps comprise: (a) placing plates of the corrosion resistant metallic material on the first and second copper billet; and (b) fusion bonding the plates to the first and second billets using hot isostatic pressing. 22. The method as in claim 20 wherein the cladding comprises one of a nickel alloy and a chromium alloy. 23. The method as in claim 20 wherein the cladding step includes depositing said corrosion resistant metallic material to said predetermined thickness in a plasma transferred arc process.