EP1147692B1 - Wear part for arc welding torch produced in alloyed copper - Google Patents

Abstract

invention concerns a wear part for electric-arc welding torch, produced in a copper alloy containing principally copper and, in addition, one or several alloy metals selected among tellurium, sulphur, lead, chromium and zirconium. Preferably, the alloy material content ranges between 0.01 % and 5 % and the copper content is at least 90 % to 95 %. The inventive wear part can be a whole or part of an electrode, a nozzle, a cartridge consisting of a nozzle/electrode assembly, an electrode holder and an electrode holder seat. The invention also concerns a plasma torch provided with one or several said wear parts and its use in a plasma cutting operation as well as a TIG, MIG or MAG torch provided with one or several said wear parts and its use in a welding operation.

Description

The present invention relates to the field of wearing parts or consumables for electric arc torches, especially for torches with plasma, comprising an electrode, typically the cathode, one of which end is centered opposite an ejection orifice of a jet formed of gas and an electric arc, such as a plasma jet, said orifice forming a diaphragm constriction and being carried by a wearing part called a nozzle.

Usually, in the case of a plasma torch, a flow suitable pressurized gas, called plasma gas, is introduced into the plasma torch, is then distributed between the electrode and the nozzle, and flows through the orifice of said nozzle towards the workpiece, by example a structural steel sheet to be cut or parts to be welded together.

In general, plasma cutting systems or installations include at least one plasma torch, a power source, a arc ignition system and means for supplying fluids, such as a plasma gas, possibly a shielding gas or a post-injected fluid, and a torch coolant.

The plasma torch can be hand-held or can be mounted on an automatic 2D cutting machine, of portal (X, Y) or 3D type robot type (X, Y, Z).

Usually the plasma cutting process exploits the effects thermal and kinetic of a plasma jet to melt the material to be cut and expel the molten material out of the formed cutting groove following a relative movement of the torch relative to the workpiece of work, that is to say the part to be cut.

In a manner known per se, an arc ignition system, of the high type frequency or short-circuiting of the electrode and the nozzle, is used for establish a pilot arc, generally of low current intensity, between the electrode carried by the torch and forming a cathode, and the nozzle also carried by the torch and forming an anode.

Then, in the case of cutting non-metallic materials, the intensity of the pilot arc current is brought to a generally higher value to reach the desired cutting current intensity value and, eventually, the plasma gas from the pilot arc is replaced by another gas or gas mixture then forming cutting plasma gas (blown arc system or not transferred). A movement is subsequently communicated, usually with a torch, to start the cutting operation properly called.

Alternatively, in the case of cutting materials metal, the pilot arc is transferred to the work piece, forming an anode, the electric circuit of the nozzle is open, the current intensity of the arc is brought to a value corresponding to the intensity of the cutting current, the plasma gas of the pilot arc is possibly replaced by another gas or gas mixture then forming cutting plasma gas (transferred arc system). A movement is then communicated, usually by torch, to begin the operation of actual cutting.

However, in all cases, it is necessary that the constituent materials of the wearing parts that are the electrode and the nozzle are carefully chosen so that these wearing parts can resist physicochemical constraints for as long as possible, in particular thermal, to which they are subjected during the operation of cutting and therefore decrease their replacement frequency when they are worn and unsuitable for ensuring correct and efficient operation of the plasma cutting torch.

In other words, the wear parts of the plasma torch must meet not only severe technical requirements, but also economic requirements because their cost must not be too high given their high replacement frequency.

• une conductivité électrique élevée pour permettre le passage du courant électrique utile sans échauffement excessif du matériau par effet Joule ou, autrement dit, avoir la possibilité de réduire les sections métalliques utiles ou d'allonger les éléments conducteurs sans risque de concentration excessive de chaleur.
• une conductivité thermique et une diffusivité thermique élevées pour permettre la propagation rapide d'un flux de chaleur au sein du matériau, dans lequel est réalisé la tuyère ou l'électrode, depuis une zone de voisinage avec un arc électrique à haute température vers une zone d'échange avec un fluide de refroidissement sans que, localement, la température de fusion du matériau ou de l'un de ses constituants soit atteinte.
• une résistance mécanique suffisante pour supporter les contraintes imposées par le mode d'assemblage des électrodes et des tuyères sur le corps de torche et éventuellement par le frottement de l'extrémité de la tuyère sur la surface à découper.
• une utilisation de matériaux d'usage courant pour un approvisionnement aisé et une bonne usinabilité pour un coût de fabrication, par grande quantité, acceptable et compatible au plan industriel.

More specifically, the technical requirements to be met include:

• a high electrical conductivity to allow the passage of useful electrical current without excessive heating of the material by the Joule effect or, in other words, having the possibility of reducing the useful metallic sections or of lengthening the conductive elements without risk of excessive concentration of heat.
• high thermal conductivity and thermal diffusivity to allow the rapid propagation of a heat flow within the material, in which the nozzle or the electrode is made, from a neighboring area with a high temperature electric arc to an area exchange with a cooling fluid without locally, the melting temperature of the material or one of its constituents is reached.
• sufficient mechanical strength to withstand the stresses imposed by the method of assembling the electrodes and the nozzles on the torch body and possibly by the friction of the end of the nozzle on the surface to be cut.
• use of commonly used materials for easy supply and good machinability at a manufacturing cost, in large quantities, acceptable and compatible on an industrial scale.

Currently, the prior art teaches that wearing parts, that is to say plasma torch electrodes and nozzles must be made in copper. As such, we can cite the documents US-A-3,575,568 and EP-A-444,344 which describe the use of copper electrodes.

However, copper is not an ideal material for making parts of wear, such as nozzles and electrodes, in particular for torches with plasma, due to the low workability of copper and its too high malleability and its too great deformability to the annealed state, which annealed state can be achieved by the combined effects of a significant heating during intensive torch operations at plasma and a temperature holding time, from which it may result from problems during disassembly by unscrewing wearing parts, in particular electrodes and nozzles for replacement. As comparison, the machinability index of copper is only 20 compared to a free cutting brass taken as base 100.

From there, some documents recommend making some of the pieces torch wear of a copper alloy with one or more others materials so as to increase the life of these wearing parts or facilitate their manufacture.

Thus, document JP-A-09035892 teaches a torch electrode plasma formed from a ternary alloy of copper, zirconium and chromium can be used for 350 hours.

In addition, document EP-A-634886 describes a torch nozzle with plasma formed from a binary alloy of more than 99.5% copper and from 0.10 to 0.20% zirconium.

Similarly, document JP-A-03011599 discloses a plasma torch electrode formed from a binary alloy, in this case of copper and 0.01 to 0.15% zirconium.

Furthermore, the document JP-A-760047397 relates to an electrode for plasma torch formed from an alloy of 0.05 to 2% tellurium, 25 to 40% silver or copper and the rest being tungsten.

We can also cite the document DE-A-19626941 which describes an alloy mainly containing aluminum with 3% copper added, 0.5% magnesium and 5% antimony, as well as document WO-A-92/14576 relating to ultra-fine ceramic carbides obtained by plasma.

The problem then is to design wear parts for improved torches, in particular for plasma torches, which are able to respond favorably to requirements and constraints mentioned above, that is to say wearing parts having lifetimes at less as good, or even higher, than those currently in existence, that is to say wearing parts made of copper or the aforementioned alloys, as usually recommended in the prior art, without however present the machining and malleability problems encountered with the copper.

From there it was highlighted, as part of this invention, that certain particular copper alloys not known in the art previous, had interesting and quite unexpected properties, and allowed to achieve wear parts with a lifespan at least equivalent, or even increased, compared to copper wear parts known from the prior art.

In other words, it appears that the addition of small amounts of certain chemical elements specific to copper, in particular tellurium, chromium or lead, confer on the copper alloy thus obtained interesting mechanical and / or machining characteristics, i.e. considerably improved without altering the properties fundamentals of electrical and thermal conductivities, lifetime and corrosion resistance of wear parts made of such an alloy.

Thus, it has been shown that the constituent materials of the wearing parts preferred, i.e. those best suited to the requirements imposed during the operation of the electric arc torch, in particular the electrode and the nozzle in the case of a plasma torch, are particular alloys of copper or alloyed copper with a content of certain additives individuals is non-zero but generally less than 2.5% or even less than 2%, or even less than 1%. In the context of this invention, the percentages (%) are percentages by weight.

In addition, the present invention also intends to provide materials alloys that can be used to make other elements consumables or wearing parts for electric arc torches, in particular for TIG, MIG or MAG welding torches, such as pliers in particular electrode holders or the electrode holder clips, since the prior art does not describe any satisafiant alloy which can be used for make this type of wear part.

A wear part for an electric arc work torch according to the The present invention is defined by claims 1 and 2. Special embodiments of wearing parts according to the The present invention is defined in claims 3 to 8, 13 and 14.

In the context of the present invention, the terms "wearing part" are equivalent to the terms "consumable part" and correspond to elements or parts constituting the parts of the arc work torch likely to undergo significant alteration during torch operation requiring frequent replacement, especially electrodes and nozzles for plasma torches, or clamps electrode holders and electrode holder clips for TIG torches, MIG or MAG.

The electrodes for torch or torch can take forms varied but, in general, an electrode is generally shaped elongated, in particular of general cylindrical or cylindrical-cylindrical shape or shape, and carries an emissive insert, in particular in hafnium, in tungsten or in zirconium, fixed at its active end or lower or downstream end.

Likewise, the nozzles for torches or torches can be coated with various forms but, in general, a nozzle is generally in the form of cup or sleeve, and is pierced with a gas passage orifice.

Such electrodes and nozzles are described in numerous documents of the prior art and, therefore, their arrangement in the torch, their general structure and mode of operation will not be detailed below.

However, as examples, reference may be made to the documents following: EP-A-750449, EP-A-278797, EP-A-573330 and EP-A-817547, which describe plasma torches.

Furthermore, according to the present invention, the choice of the material or materials alloy can be done according to several parameters or conditions.

• des alliages de cuivre et de tellure (Cu-Te) contenant, par exemple, d'environ 0,3% à 0,7% de tellure, de tels alliages sont appelés alliages de type cupro-tellure ; ou
• des alliages de cuivre et de plomb (Cu-Pb) qui présentent des propriétés très voisines de celles du cupro- tellure.

Thus, when easy machinability and a low cost of manufacturing by machining are essential and it is necessary to maintain a correct thermal and electrical conductivity, copperwinds are preferentially used as the material constituting the wearing parts. allies containing elements favoring machining, such as:

• copper and tellurium alloys (Cu-Te) containing, for example, about 0.3% to 0.7% tellurium, such alloys are called cupro-tellurium type alloys; or
• copper and lead alloys (Cu-Pb) which have properties very close to those of cuprotellide.

Indeed, it was highlighted that the addition of these elements insoluble, such as Te and Pb, dispersed into fine globules significantly improves the suitability of copper for machining because these elements make the chips short and brittle by facilitating their fractionation, and it follows that the ability to the machining of these copper alloys is quite comparable to that of free cutting brasses.

Wear parts made of such copper alloys can be used in any plasma arc work application generating a temperature near surfaces around the plasma arc, during torch operation, which does not exceed the melting temperature addition elements constituting the alloy, namely: 330 ° C for lead and 450 ° C for tellurium.

• des alliages de cuivre et de chrome (Cu-Cr) contenant, par exemple, d'environ 0,5% à 1% de chrome, de tels alliages sont appelés alliages de type cupro-chrome ;
• des alliages de cuivre et de zirconium (Cu-Zr) contenant, par exemple, d'environ 0,1% à 0,2% de zirconium, de tels alliages sont appelés alliages de type cupro-zirconium ; ou
• des alliages de cuivre, de chrome et de zirconium (Cu-Cr-Zr) contenant, par exemple, environ 0,8% de chrome et 0,15% de zirconium, de tels alliages sont appelés alliages de type cupro-chrome-zirconium.

On the other hand, when high mechanical strength is desired, as well as good thermal and electrical conductivity, it is preferable to use alloyed brass with structural hardening capable of providing high resistance to deformation, particularly when hot, such as:

• copper and chromium alloys (Cu-Cr) containing, for example, from about 0.5% to 1% of chromium, such alloys are called cupro-chromium type alloys;
• copper and zirconium alloys (Cu-Zr) containing, for example, from about 0.1% to 0.2% of zirconium, such alloys are called cupro-zirconium type alloys; or
• copper, chromium and zirconium alloys (Cu-Cr-Zr) containing, for example, about 0.8% chromium and 0.15% zirconium, such alloys are called cupro-chromium-zirconium alloys .

Indeed, structural hardening is a phenomenon that allows improve the mechanical and electrical characteristics of an alloy, by particular by heat treatment for dissolving the elements addition, by quenching and by tempering.

In practice, a work hardening (E) is applied, either between the hardening (T) and income (R), that is, after income (R), which makes it possible to obtain even higher mechanical characteristics.

These are TER and TRE states for which structural hardening and hardening cumulate their effects.

Such alloys, in the states cited above, have machinability lower than cupro-tellurium, but higher than that of copper unalloyed.

The method of manufacturing a wearing part according to the present invention is defined by claim 9. Wear parts obtained by a such a process are defined in claims 10 and 11.

According to another aspect, the invention also relates to a work torch with the electric arc, in particular a plasma torch or a torch TIG (Tungsten Inert Gas), MIG (Métal Inert Gas) or MAG (Metal Active Gas) comprising at least one wearing part according to the invention, in particular a electrode holder clamp and / or an electrode holder clamp seat.

The invention will now be described in more detail using examples of embodiments shown diagrammatically in the appended figures, which are given by way of illustration but not limitation.

• un corps supérieur 92 réalisé en un matériau conducteur de l'électricité et formant porte-électrode ;
• un corps inférieur 93 réalisé en un matériau conducteur de l'électricité et formant porte-tuyère ; et
• un corps intermédiaire 94 réalisé en un matériau non-conducteur de l'électricité et intercalé entre le corps supérieur 92 et le corps inférieur 93, de sorte d'isoler électriquement le corps supérieur 92 et le corps inférieur 93, l'un de l'autre, et à les maintenir de manière concentrique, l'un à l'autre.

FIG. 9 shows diagrammatically the lower end or active end, seen in longitudinal section, of a plasma cutting torch comprising a torch body 91 comprising:

• an upper body 92 made of an electrically conductive material and forming an electrode holder;
• a lower body 93 made of an electrically conductive material and forming a nozzle holder; and
• an intermediate body 94 made of an electrically non-conductive material and interposed between the upper body 92 and the lower body 93, so as to electrically isolate the upper body 92 and the lower body 93, one of the other, and to hold them concentrically, to each other.

A coating 95, made of an electrically insulating material, binds mechanically the assembly formed by the upper body 92, the body lower 93 and the intermediate body 94, so as to form a single block unique.

An electrode 96, in the form of a cup with a blind bottom and constituting a wear part of the torch, is screwed tightly on the electrode holder formed by the upper body 92.

Similarly, a nozzle 97, in the form of a cup with a bottom pierced with a calibrated orifice 97a for the outlet of the plasma jet, constituting a torch wear part, is screwed tightly to the formed nozzle holder by the lower body 93.

A flow of gas G under pressure is distributed through an orifice 98, via a dip tube 99, towards the interior bottom of the electrode 96, then rises in opposite direction in a circular section chamber 910 fitted between the outer surface of dip tube 99 and inner surface of the electrode holder formed by the upper body 92.

A first portion G1 of said flow of gas G under pressure is derived by a first series of calibrated orifices 921 made in the wall of the electrode holder formed by the upper body 92, then by pipeline between the outer walls of the electrode holder, of electrode 96 and the walls internal of the insulating intermediate 94 and the nozzle 97, before being evacuated outside said nozzle 97 through the ejection orifice 97a.

The second portion G2 of the flow of gas G under pressure is distributed successively by the rings of calibrated orifices 922, 941 and 931, towards an annular section 981 delimited by the external walls of the electrode holder, nozzle 97 and the internal wall of a nozzle 98 made generally made of an electrically insulating material.

The gas flow G1 forms the plasma gas and therefore contributes to the high temperature arc and plasma jet formation when the system plasma cutting is in progress.

The initial gas flow G1 and the residual gas flow G2 form the means of cooling by forced convection of the torch body 91, the electrode 96 and the nozzle 97.

Figures 1 to 8 show, for their part, examples of diagrams of embodiments of nozzles and electrodes, that is to say of parts wear within the scope of the present invention, for different types torches.

• à sa partie supérieure ou amont, un taraudage 4 pour permettre un assemblage par vissage de l'électrode 1 sur un corps de torche, comme montré sur la figure 9,
• à sa partie inférieure ou partie active, un alésage 6' pour recevoir, par emmanchement à force, par sertissage et/ou par brasage, un insert émissif 3 constitué de zirconium, de hafnium ou de tungstène, sous une forme pure ou alliée,
• dans sa partie médiane 5, une forme externe polygonale, notamment hexagonale, pour permettre la prise d'une clé de forme adaptée pour effectuer le vissage et le serrage de l'électrode 1 sur son support dans le corps de torche, comme montré sur la figure 9.

Thus, FIG. 1 shows, in a longitudinal section view, an electrode 1 with a solid body consisting of an electrode body 2, of generally axisymmetric shape in a cup with a blind bottom, comprising,

• at its upper or upstream part, a thread 4 to allow assembly by screwing of the electrode 1 on a torch body, as shown in FIG. 9,
• at its lower part or active part, a bore 6 ′ for receiving, by force fitting, by crimping and / or by brazing, an emissive insert 3 made of zirconium, hafnium or tungsten, in pure or alloyed form,
• in its middle part 5, a polygonal external shape, in particular hexagonal, to allow the taking of a key of shape adapted to carry out the screwing and tightening of the electrode 1 on its support in the torch body, as shown on the figure 9.

In this example, the wearing part, that is to say the electrode 1, is consisting of an alloyed copper of the cupro-tellurium type having tellurium content about 0.3 to 0.7%, the remainder being mainly copper and possibly unavoidable impurities.

This electrode 1 is made from a cupro-tellurium bar of hexagonal section, which is subjected to machining by bar turning high rate, which makes it possible to obtain electrodes at low cost of returns, and with high operating efficiency and long service life.

FIG. 2 represents, for its part, a resistance electrode 1 elevated mechanics of general shape analogous to that of FIG. 1; the Similar or identical parts have the same references.

According to FIG. 2, the electrode 1 comprises, in its middle part 5, an external prismatic or semi-prismatic shape allowing the taking of a form key suitable for screwing and blocking electrode 1 on its support in the torch body.

In addition, a groove 7, intended to receive an O-ring sealing, is made between the thread 4 and a bearing 8 forming a stop assembly.

In this example, the wear part, i.e. the electrode body 2 of electrode 1, is made of copper alloy of the cupro-chrome type having a chromium content of approximately 0.5% to 1%, which allows, despite the weakening of section generated by the groove 7, an electrode of sufficient mechanical strength to withstand tightening and loosening with high torque by means of a wrench, without risk of torsional breakage, shear and / or elongation in the section weakening zone.

Such an electrode has a high thermal resistance because the use of a copper alloy of the cupro-chrome type for the production of the electrode 1 allows its geometric integrity to be preserved, in particular at neighborhood of the emissive insert 3, that is to say without local fusion, despite a high temperature of the active end carrying the insert 3, for example, when a first electric arc is ignited without recourse to a system high frequency (HF) ignition, i.e. after short-circuiting the tip of electrode 1 and the bottom of the torch nozzle.

For such an application, i.e. a short-circuit ignition, cupro-tellurium is hardly recommended because, during the course of the arc between the short-circuit breaking point and the end point of its attachment to the insert emissive 3, tellurium globules, insoluble in copper but entering melts at around 450 ° C, tend to vaporize or run off on corresponding surfaces thereby altering the geometry of these surfaces, disrupt the flow of plasma gas flow and, therefore, to lead to rapid degradation of the cutting performance of the arc plasma column.

Figure 3 shows schematically, a nozzle at low cost for plasma torch within the scope of the present invention.

More precisely, the nozzle 7, of general shape in a bottom cup drilled, has an internal recess 17, a gas passage channel 7a plasmagen and electric arc, and a thread 18 at its upper part external to allow assembly by screwing onto a torch body, as shown in figure 9.

In this example, the use of a copper alloy of the cupro-tellurium type having a tellurium content of 0.3% to 0.7%, as a constituent material of the wearing part, that is to say of the nozzle 7, makes it possible to produce a high-speed machining by machining and therefore leads to obtaining low cost nozzles.

Figure 4 shows schematically, a nozzle with thermal resistance high for plasma torch, generally similar in shape to that of Figure 3; identical or similar parts have the same references.

The nozzle 7 of FIG. 4, of general shape also in a cup with pierced bottom, again includes an internal recess 17 and a channel 7a passage of plasma gas and electric arc.

The dimensions of channel 7a are such that the plasma jet is strongly constricted and a very significant heat exchange ensues between said plasma jet and the nozzle 7, in the region of the walls of said channel 7a, then leading to a heating of said walls to a temperature sometimes reaching more than 500 ° C.

From there, it is better to use, in this case, a constituent material of the nozzle 7, namely a copper alloy of the cupro-chrome type containing 0.5 to 1% chromium, to maintain the geometric integrity of the nozzle 7, in particular of the walls of the channel 7a, that is to say substantially without local fusion, despite a significant temperature of said walls.

Again, cupro-tellurium is much less recommended for above reasons (see Figure 3).

Figure 5 shows schematically, another embodiment of a nozzle 7 with high thermal resistance and moderate cost price entering in the context of the present invention.

• une partie supérieure 19 réalisée en cupro-tellure contenant une teneur en tellure comprise entre 0,3 et 0,7%, comme expliqué ci-avant, permettant un usinage aisé par décolletage à grande cadence et permettant d'obtenir. dès lors, un gain substantiel de prix de revient sur une partie de volume important, et
• une partie inférieure 20, comportant le canal 7a d'éjection du jet plasma, réalisée en cupro-chrome contenant une teneur en chrome de 0,5 à 1%, garantissant une bonne tenue thermique au voisinage d'un jet plasma fortement constricté. La partie inférieure 20 est assemblée par emmanchement à force ou par brasage dans la partie supérieure 19.

The nozzle 7 in FIG. 5 is a composite wearing part, that is to say a nozzle produced in two parts, namely:

• an upper part 19 made of cupro-tellurium containing a tellurium content of between 0.3 and 0.7%, as explained above, allowing easy machining by cutting at high speed and making it possible to obtain. consequently, a substantial gain in cost price over a large part of the volume, and
• a lower part 20, comprising the channel 7a for ejecting the plasma jet, produced in cupro-chrome containing a chromium content of 0.5 to 1%, guaranteeing good thermal resistance in the vicinity of a highly constricted plasma jet. The lower part 20 is assembled by force fitting or by brazing in the upper part 19.

FIG. 6 represents a complex electrode 61 at low cost of returns, according to the invention, composed of a main body 62, produced by example in free-cutting brass (CuZn39Pb2 or CuZn40Pb3), in shape general of revolution and comprising at its lower part or active part, a first bore 65 and a second bore 60 of smaller diameter. A dip tube 63, cylindrical, made of free-cutting brass of a shade similar to that of the main body 62, is force-fitted in the bore 60 of the main body 62. A bore 67 for the passage of gas is made in the main body 62 to be in communication with a hole 68 of identical and coaxial diameter made in the dip tube 63. A series of calibrated orifices 62a is drilled in the upper part of the bore 65 so as to connect the demarcated section 69, on the one hand, by the external wall of the dip tube 63 and, on the other hand, by the inner wall of bore 65, with the environment of electrode 61. The calibrated orifices of the series of calibrated orifices 62a are drilled so as to tangentially open into bore 65. On the other hand, a set 64 consisting of a cylindrical hafnium 64b emissive insert set in a cylindrical tubular casing 64a made of cupro-chrome with a content in chromium between 0.5 and 1%, is force-fitted into the bore 65, so as to completely close off the end of the electrode 61. Thus arranged, the electrode 61 has an internal circuit allowing circulation of a gas flow 66, forming plasma gas, via the holes 67, 68 towards the rear surface of the assembly 64 to cool it, when an electric arc is formed on the underside of the emissive insert 64b, then channeling said flow through section 69 to calibrated orifices 62a to form the currents of gas 66a necessary for the formation of the plasma arc. Facilities additional are practiced on the external periphery of the part upper part of the electrode body 62, namely: a first groove 62b intended to receive a system comprising at least one ball coming from the torch body and allowing the locking of the electrode 61 in said torch body; a second groove 62c intended to receive a seal sealing ring.

Such a complex electrode 61 is used as an element constituting a set of wearing parts, otherwise called cartridge as shown in figure 8.

More specifically, a cartridge 80 according to FIG. 8 comprises a electrode 61, as described above, a nozzle 82 pierced with a calibrated orifice 82a for ejecting the plasma jet and produced in cupro-tellurium (tellurium content from 0.3 to 0.7%), an insulating shim 83 made of material thermosetting plastic, a first O-ring seal 85, a second seal 84. All of these elements 61, 82, 83, 85 is made inseparable by constriction of a thin lip 82b, coming from the body of the nozzle 82, up to the backlash free contact of the insulating shim 83 located then pressed and locked in position on a seat 82c machined in the nozzle 82.

The use and operation of such an assembly or cartridge 80 are notably described in documents EP-A-0326445, US-A-4914271, JP-A-2714421, CA-A-1303684 and DE-A-68903645.0

• un corps principal 72 réalisé en un alliage de type cupro-tellure (cuivre + 0,3 à 0,7% de tellure) pour permettre un usinage par décolletage à grande cadence et pour obtenir ainsi un gain substantiel de prix de revient sur une partie de volume important, et
• un pion cylindrique 73 constitué d'un insert émissif en hafnium 73b, de forme cylindrique, serti dans une enveloppe tubulaire cylindrique 73a, réalisée en un alliage de type cupro-chrome (cuivre + 0,5 à 1% de chrome), garantissant une bonne tenue thermique au voisinage de l'arc. Le pion 73 est emmanché à force dans l'alésage 74 pratiqué à l'extrémité du corps principal 72.

Furthermore, FIG. 7 shows diagrammatically an electrode 71 with high thermal resistance and at moderate cost price, which electrode 71 is produced in two parts, namely:

• a main body 72 made of an alloy of cupro-tellurium type (copper + 0.3 to 0.7% tellurium) to allow machining by high-speed turning and thus to obtain a substantial gain in cost price over a part large volume, and
• a cylindrical pin 73 consisting of an emissive insert of hafnium 73b, of cylindrical shape, set in a cylindrical tubular casing 73a, made of an alloy of cupro-chrome type (copper + 0.5 to 1% chromium), guaranteeing a good thermal resistance in the vicinity of the arc. The pin 73 is force fitted into the bore 74 made at the end of the main body 72.

Although the wearing parts have been described in relation to a plasma cutting torch, it is understood that the wear parts according to the present invention, in particular the electrodes, the nozzles, cartridges formed of an electrode / nozzle assembly, the electrode holders and the electrode holder pliers, are not limited to torches only cutting plasma and that they can also be intended for other types torches or torches, in particular marking torches, TIG, MIG or MAG welding, plasma spraying and, in general, any heat treatment torch for metallic materials or not metal.

Claims (14)

1. Wear part for an electric-arc work torch, in particular for a TIG, MIG or MAG torch, the said wear part being chosen from the group formed by electrode holders and seats for electrode holders, characterized in that at least a portion of the said wear part is made of a copper alloy containing:

   at least 90% copper; and

   at least one alloying material chosen from the group formed by tellurium, lead, zirconium and chromium.
2. Wear part (1, 61, 71, 7, 80) for an electric-arc work torch, in particular for a plasma torch, the said wear part being chosen from the group formed by the electrodes (1, 61, 71), the nozzles (7) and the cartridges (80) formed from an electrode/nozzle combination, at least a portion of the said wear part being made of a copper alloy, characterized in that the said copper alloy contains:

   at least 90% copper; and

   from 0.01% to 5% of an alloying material chosen from the group formed by tellurium and lead.
3. Wear part according to either of Claims 1 and 2, characterized in that the content of alloying material in the copper the copper alloy is from 0.05% to 3%.
4. Wear part according to either of Claims 1 and 2, characterized in that the copper content in the copper alloy is at least 95%.
5. Wear part according to one of Claims 1 to 4, characterized in that the alloying material is tellurium and in that the tellurium content in the copper alloy is between 0.1% and 1.5%.
6. Wear part according to one of Claims 1 to 5, characterized in that the alloying material is tellurium and in that the tellurium content in the copper alloy is between 0.3% and 0.7%.
7. Wear part according to Claim 1, characterized in that the alloying material is chromium and in that the chromium content in the copper alloy is between 0.05% and 3%, preferably between 0.5 and 1%.
8. Wear part according to one of Claims 1 to 4, characterized in that the alloying material is lead and in that the lead content in the copper alloy is between 0.1% and 1.5%, preferably between 0.3% and 0.7%.
9. Process for manufacturing a wear part for an electric-arc torch, made of a copper alloy containing at least 80% copper and at least one alloying material chosen from the group formed by chromium and zirconium, in which process:

   - (a) the said wear part is mechanically machined to the desired shape from an alloy material that has undergone at least one quench-hardening step (Q) or at least one quench-hardening step (Q) and one work-hardening step (W); and

   (b) at least one structural hardening operation is carried out on at least a portion of the alloy material constituting the wear part obtained in step (a) by at least one tempering step (T).
10. Wear part (1, 61, 71, 7, 80) for an electric-arc work torch obtained by the manufacturing process according to Claim 9, in particular for a plasma torch, the said wear part being chosen from the group formed by the electrodes (1, 61), the nozzles (7) and the cartridges (80) formed from an electrode/nozzle combination, at least a portion of the said wear part being made of a copper alloy containing at least 95% copper and from 0.1% to 1% of at least one alloying material chosen from the group formed by chromium and zirconium.
11. Wear part according to Claim 10, characterized in that the alloy is chosen from the group formed by copper-chromium alloys containing about 0.5% to 1% chromium, copper-zirconium alloys containing about 0.1% to 0.2% zirconium and copper-chromium-zirconium alloys containing about 0.70 to 0.90% chromium and 0.12 to 0.18% zirconium.
12. Electric-arc work torch, in particular a plasma torch or a TIG, MIG or MAG torch, which includes at least one wear part according to one of Claims 1 to 8, 10 and 11.
13. Electrode (1, 61, 71) for a plasma torch according to Claim 2, made of a copper alloy containing at least 95% copper and from 0.01% to 5% tellurium.
14. Nozzle (7) for a plasma torch according to Claim 2, made of a copper alloy containing at least 95% copper and from 0.01% to 5% tellurium.

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