US3198932A

US3198932A - Arc electrode

Info

Publication number: US3198932A
Application number: US183880A
Authority: US
Inventors: Merle H Weatherly
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1962-03-30
Filing date: 1962-03-30
Publication date: 1965-08-03
Anticipated expiration: 1982-08-03
Also published as: BE641318A; DE1515230B1; AT253900B; NL290760A; GB1022282A; DK109220C; NL139681B

Description

Aug. 3, 1965 INVENTOR MERLE H. WEATHERLY BY A ORNEY 1965 M. H. WEATHERLY 3,198,932

ARC ELECTRODE Filed March 30. 1962 2 sh t s 2 INVENTOR. MERLE H. WEATHERLY ATTORNEY United States Patent 3,198,932 ARC ELECTRODE Merle H. Weatherly, Indianapolis, Ind., assignor to Union Carbide Corporation, a corporation of New York Filed Mar. 30, 1962, Ser. No. 183,880 35 Claims. (Cl. 219145) This invention relates to arc electrodes, more particularly this invention relates to an improved non-consumable electrode for use in electric arc processes such as cutting, welding and electric arc furnace processing of metals.

Electrically conductive materials, such as tungsten, have been used for many years as high current electrodes in arc devices. The addition of emissive oxides, such as thoria, yttria and calcia, to the refractory electrode is also well known to increase the current carrying capacity. Such electrodes can be used in a substantially non-consumable fashion up to current levels of thousands of amperes. This is true only in substantially inert gas atmospheres, such as argon and helium. When chemically reactive gases, such as oxygen, carbon dioxide or methane are used, the refractory metal electrodes are rapidly consumed.

Electrodes constructed of low melting point, high thermally-conductive metals, such as copper, silver and aluminum, are known to be resistant to damage as an anode in many reactive gases. However, these low melting point materials cannot be used as cathodes at high current levels without the use of special protecting means such as magnetic rotation of the arc.

The present invention is involved with improving electrodes so that they exhibit stable, high current operation under substantially any atmospheric conditions. Such electrodes are especially useful in various processes requiring arc torches. For example, in welding and metal cutting, reactive gases such as oxygen can now be used with non-consumable electrodes. In coating and crystal growth applications where power is fed to the torch, the use of this electrode allows the powder to be fed through the torch past the electrode without using an auxiliary shielding gas for the cathode.

Accordingly it is the main object of this invention to provide an electrode which exhibits stable operation under substantially any atmospheric condition.

It is another object to provide an electrode which will operate stably in reactive gas atmospheres.

Yet another object is to provide an electrode which will exhibit stable operation at high currents in any atmospheric condition.

Still another object is to provide an electrode having a high density insert of a highly electron emissive material which will not be substantially eroded by vaporization and ejection of such material for substantially longer periods of time.

A further object is to provide an electrode for use in reactive gas atmospheres which includes an insert material such as the metals zirconium and thorium.

Still another object is to provide a method for Working materials with an electric are operating in a reactive gas atmosphere.

Another object is to provide apparatus for carrying out a method for working materials in a reactive atmosphere.

Other objects will become apparent from a consideration of the following description and drawings wherein:

FIGURE 1 is a cross-sectional view taken in elevation of the electrode of the invention;

FIGURE 2 is a schematic of exemplary apparatus in which the electrode of the invention may be used;

FIGURE 3 is a view looking in the direction 33 at the electrode shown in FIGURE 1;

FIGURES 4-6 are cross-sections of various modifications of the electrode shown in FIGURE 1.

The objects of the invention are accomplished in general by a non-consumable electrode which consists of an insert of a material which is a good electron emitter, or which becomes a good emitter upon reaction with a reactive gas, embedded in a holder of metal which is characterized by its high thermal conductivity. The holder is cooled by a coolant such as water and the insert material is always separated from said coolant by a mass of the high heat conducting metal holder such that the heat dissipation from the insert material to the cooling fluid is substantially improved.

More specifically, a preferred embodiment of the electrode according to the invention for use with reactive gases including oxygen and nitrogen consists of a watercooled copper holder having embedded therein an insert of zirconium.

In addition a method for working materials is accomplished according to the invention by striking an electric arc from an electrode consisting of a fluid-cooled high heat conductivity metal holder having metallurgically bonded thereto an insert of a metal such as zirconium, thorium, lanthanunrand strontium. The arc struck is maintained in an atmosphere of a reactive gas such as oxygen, air, nitrogen, carbon monoxide, carbon dioxide, methane, etc. The resulting arc gas is applied to the material to be worked.

One typical apparatus for carrying out the method of the invention includes the combination of a fluid-cooled metal electrode holder having a high heat conductivity and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium, the insert being metallurgically bonded to the holder; with a gas directing nozzle; means for feeding a reactive gas to the inlet of the nozzle; and means for connecting the electrode to a source of power for drawing an are from the electrode to the work to be treated.

Referring to the drawings and particularly to FIGURE 1, the electrode E of the invention consists of a metal holder 1 having an insert 5. The metal used for such holder must have a high thermal conductivity. Examples of such metals are copper, silver, aluminum, brass, molybdenum tunsten, columbium, tantalum, and steel as well as alloys containing major constituents of at least one of these metals. The holder 1 is provided with a cooling chamber 3 through which cooling fiuid is circulated during operation. A space is provided in the front face of the holder 1. The insert 5 of a highly emissive material i position in the space provided.

In practice, it has been found that various types of materials may be used as the insert material depending upon whether the torch is being operated in conjunction wi h a reactive or an inert gas. Thus, it has been found that the materials of thoria, zirconia, ceria, y-ttria, tantalum oxide, magnesium oxide, lanthanum oxide, gadolinium oxide, calcium oxide, strontium oxide, a mixture of strontiurn oxide and calcium oxide, and a barium oxide-strontium oxide mixture can be used in current ranges greater than 200 amperes for relatively long periods of time in an inert atmosphere.

In reactive atmospheres, inserts made from materials which are themselves good emitters or which form good emitting materials upon reacting with such reactive atmospheres have been found to be operative in current ranges greater than 200 amperes for relatively long periods of time. For example, materials such as thorium, zirconium, strontium and lanthanum or compounds of these materials, specially their oxides have been found to provide exemplary service.

In addition, it has been found that zirconium will operate successfully in other reactive atmospheres such s carbon monoxide, carbon dioxide, methane, nitrogen or nitrogen-hydrogen mixtures. This is because the insert material will form a compound with the particular gas being used. Thus, when operating in an atmosphere of nitrogen, zirconium nitride will be formed which in itself is a good emitter. It should be understood that these materials and gases are listed by way of example only. A number of materials that can be used with varying gases will be shown hereinafter by way of example.

It also has been found that additions of silver to powders of zirconium, lanthanum, thorium, or strontium increases the life of the electrode as compared to'powder inserts without silver. The silver apparently improves the heat transfer from the insert without substantially increasing the Work function of the insert. The silver may be mixed with the powdered insert material as a powder itself, or it may be alloyed with the insert material.

For purposes of this disclosure, the term reactive gas includes, for example, gases such as air, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, nitrogenhydrogen mixtures and other similar gases. v

The characteristics of the materials that can be used as an insert is that it must be a good electron emitter. Work function which is defined in the literature as a measure of the energy necessary to get the material to emit electrons, is a way of predicting if a material is a good emitter. A material is a good emitter if its work function is low. The lower the work function the less heat is necessary to get the material to emit which in turn diminishes the heatdissipation problem. The problem of heat dissipation is critical and will be discussed in greater detail hereinafter.

In discovering the inventive electrode combination several critical features were found to be necessary to provide an electrode having a long operating life at high current levels.

The most important criticality is that of heat dissipation. It was found that water cooling of the holder was essential to prevent the are from attaching to the holder. Further, the insert must be sufficiently cooled to prevent excessive vaporization but not cooled to the point where it becomes a poor emitter. Erosion of the insert, which is a prime reason for failure of the electrode, may occur by vaporization and rejection of molten drops fromsurface A (see FIG. 1). Therefore, good heat conduction from face A is important to minimize erosion.

The resistance to heat transfer from face A of the insert to the cooling Water can be divided into four parts: (1) heat transfer through the insert from face A to face B, (2) heat transfer across face B, (3) heat transfer through the holder to the face C, (4) heat transfer from face C to the cooling water.

Heat dissipation has been improved in the present elec trode by providing a circulating cooling fluid through the holder to carry away the heat transferred across face C.

Further improvement in heat dissipation has been achieved across face B by providing a metallurgical bond between the insert material and the holder. For example, one type bond which has provided for good heat dissipation between a zirconium insert and a cooper holder is made as follows: first a zirconium rod is cleaned in an acid solution (mixture of hydroiiuric and nitric acid)- Then zinc chloride is melted and the zirconium immersed therein which results in the formation of zirconium chloride and free zinc which plates the zirconium. Next silver is melted and the insert is dipped therein, thus applying a silver coating. Then silver is melted into the cavity of the insert holder. The zirconium insert with the silver coating is inserted into the cavity. Heat is then applied until the silver flows around the insert.

The heat dissipation through the insert itself is increased by providing a high density material substantially free from air spaces and pores. For the purposes of this dis-. closure the term high density is used to mean a density of about 90% of the theoretical density for the metals.

3 For the compounds of the metals the term is used to mean a density of about The preferred geometrical shape for the insert is a cylinder. It has been found that optimum operating conditions are achieved when the cylinder has a length of from about V inch to about /2 inch. If the insert becomes too short there Will be an insufficient amount of metal to stand up under the erosive effects of the arc. However, the solution to this problem is not simply in increasing the length of the insert since if the length becomes excessive and erosion does occur, the amount of erosion will become large enough that double arcing to the inner face of the electrode cavity for the insert will occur. A typical length of insert which is admirably suited to the invention is about /s inch.

While the above geometry is preferable for most electrode applications, ring or tubular shaped inserts or irregular shaped inserts could also be employed as well as multiple inserts. FIGURES 4-6 illustrate insert arrange ments which have been used successfully. FIGURE 6 shows an annular insert which has been successfully used. Under optimum conditions, the arc is operated from the entire annular insert surface. Multiple inserts are shown in FIGURES 4 and 5. \Vhen multiple inserts are used, the overall current carrying capacity of the electrode combination is increased since each of the inserts can carry about the same current as an electrode combination of the type shown in FIGURE 1, having an insert of the same size.

Regardless of which configuration is being used, certain dimensional relationships for both the electrode insert and the electrode body must be maintained for stable arc operation and good current carrying capacity of the electrode. Thus it has been found that the distance from the insert to the cooling chamber should be optimurnly chosen for best operating results. That is, for the configuration shown in FIGURE 1, and using a /s inch long insert, the operation life of the insert was 1 hour when operating at 300 amperes with the cooling chamber located inch from the face A of the insert. Under the same conditions, with the cooling passage being 7 inch from the insert face, the life of the insert increased to about 3% hours. With the passage /2 inch from the face, the operating life was about 4- hours. When the distance was increased to /8 inch, however, the operat-' ing life dropped to 2 hours.

' Although the electrode according to the invention, may comprise many different combinations of holder and insert material depending on the intended use, the following is a description of one of the most important applications of the invention electrode, namely oxygen cutting of metals.

FIGURE 2 is an illustration of typical apparatus in which the invention electrode can be used for cutting. For example, referring to FIGURE 2, the electrode E of the invention is threaded onto an electrode body '10. Positioned in the body it) is a tubular member 12 through which coolant is supplied to the Water chamber 14 in electrode holder 16. The circulating coolant leaves the torch through passage 18 and coolant outlet 29. A reactive gas such as oxygen is suplied to torch body through gas inlet 22 and passed down through annular chamber 24 to the are area. electrode and aids in constricting the arc. Such nozzle 25 is cooled by supplying water to the nozzle through inlet 28 and then around passage 30 and out outlet 32.

In most applications, the gas is introduced into the torch so as to impart an axial flow. Under such conditions, the insert is preferably made flush with the face of the electrode holder. However, the gas may be introduced into the torch in a manner such that a swirling or vortex flow is achieved. Under such a condition, it is preferred that the insert be recessed from the face of the holder for minimum electrode erosion.

In operation, the arc is struck between insert 34 and anode 36. While the invention is primarily directed to an A nozzle 26 surrounds the inventivev improved cathode structure for direct current operation, it should be understood that the invention is also useful for alternating current power. The oxygen gas passes around electrode combination 1634 and out nozzle 26. The resulting high intensity are is useful for cutting metals.

It is to be understood that the electrode of the invention may be used in a torch that operates either transferred or non-transferred.

The insert materials which have been found to be most useful when operating in ambient atmosphere or other reactive gases are the metals lanthanum, strontium, zirconium, and thorium.

It is postulated that the metal to be used as an insert when operating in a reactive gas atmosphere such as oxygen should be characterized by the fact that the compound formed by the reaction with the gaseous atmosphere should have a high melting point, low work function, and high boiling point.

The ideal electrode for cutting applications wherein a gas such as oxygen, nitrogen, or nitrogen-hydrogen mixtures is the arc gas, comprises a water-cooled copper holder and a zirconium metal insert which is preferably metallurgically bonded to the holder.

The following are examples of the inventive electrode which have been useful in cutting with a reactive gas as the arc gas.

EXAMPLE I Use metallurgically bonded insert cathode in oxidizing atmosphere Apparatus of the type shown in FIGURE 2 was used. The torch consisted of a in. dia., water-cooled copper electrode holder. A zirconium insert inch in diameter was coated with zinc and silver brazed in a cavity in the tip of the electrode holder. The external face of the zirconium material was flush with the face of the electrode tip. This electrode was mounted inside a Water-cooled nozzle having a in. dia. outlet. The distance from the face of the insert to the cooling passages was 7 inch. Oxygen gas at 95 c.f.h. was passed around the cathode and out through the nozzle while an arc of 300 amperes at 90-108 volts was maintained from the cathode through the nozzle to a water-cooled copper anode. The arc was very stable during a 7 /2 hour operating period.

A A inch diameter by /s inch long insert operating under conditions similar to Example I lasted for 3 /2 hours. A .180 inch diameter by inch long insert lasted 2% hours. Thus, it is postulated that operating life of the insert at relatively high currents can be increased by increasing the diameter. insert operating at from l50-5OO amperes at 90 volts under similar conditions but Without a metallurgical bond operated for only 17 minutes before appreciable erosion occurred.

EXAMPLE II Zirconium insert cathode in N H mixture The apparatus of the type shown in FIGURE 2 was used. A A1, inch diameter by inch long zirconium in- O sert was used and the electrode holder was made of silver EXAMPLE III Zirconium insert cathode in carbon dioxide atmosphere The apparatus used was the same as in Example II excepting that the electrode holder was water-cooled copper. Carbon dioxide was passed around the cathode in the same manner at the rate of 85 c.f.h. while the same type of I" Also, a zirconium arc at 300 amperes and -110 volts was maintained for twenty-five 6-minute periods.

EXAMPLE IV Zirconium insert cathode in carbon monoxide atmosphere The apparatus used was of the type shown in FIG- URE 1. The torch consisted of a .480 inch diameter water-cooled copper electrode With a .090 inch by inch long zirconium insert. An undetermined amount of carbon monoxide was passed around the cathode through a inch nozzle while an arc of |l=50 amperes and 56 volts was maintained between the cathode through the nozzle to a workpiece for a period of 5 minutes. There was very little erosion of the insert.

EXAMPLE V Thorium insert cathode in oxidizing atmosphere The apparatus used consisted of 0.480 inch diameter Water-cooled copper electrode having a 0.086 diameter by A1 inch insert thorium powder. Oxygen was passed around the cathode in the same manner as in Example I at the rate of 75 c.f.h. The cathode operated with no substantial erosion for 1 hour at 300 amperes and for 1 hour and 10 minutes at 500 amperes. The voltage varied from 72 to 92 volts.

In another application, the inventive electrode can be used without any nozzle whatsoever. In such case, the ambient atmosphere is the arc gas. In this case silver is the preferred electrode holder material. Whenever the electrode material surrounding the insert becomes oxidized, the oxide oan act as an electron emitter. Some of the arc current is thus transferred to the surrounding electrode area and the arc stability is impaired. Copper oxide is particularly bad in this respect. Silver oxide, on the other hand, is relatively unstable and decomposes at the arc temperatures. There is thus no emitter present on the silver surface to cause arcing similar to the copper oxide which forms on copper electrodes under simila conditions.

EXAMPLE VI Silver-zirconia insert cathode The cathode consisted of a 0.7 in. dia. silver electrode.

' A 0.086 in. dia. hole A; in. deep was drilled in the electrode face and filled with stabilized zirconia. This cathode was then operated in the open air with no nozzle and no gas flow introduced around the electrode. At an arc length of in. from a water-cooled copper anode the arc was 32 volts and amperes. There was no arcing from the silver. The cathode was operated about 15 minutes in static air and the arc attachment at the zirconia cathode appeared to 'be quite stable.

The folowing examples are illustrations of the various combinations of the insert holder and insert materials which can be used with various arc gases. The examples are intended to illustrate the breadth of the inventive concept and are not intended to limit the invention.

EXAMPLE VII Use of insert cathode in inert atmosphere The torch consisted of a inch diameter water-cooled electrode holder having a .128 inch diameter zirconia insert. The external face of the insert was flush with the electrode holder, its face being inch from the cooling passage. The electrode was mounted in a inch diameter nozzle. Argon gas at the rate of 45 c.f.h was Passed around the cathode through the nozzle while an arc of 200 amperes and 30 volts was maintained through the nozzle to a water-cooled anode. The insert ran for about 5 minutes and then failed. Under the same conditions, but using a inch diameter holder, the insert operated for 6 minutes at 400 amperes without failure. Thus, it again appears that increasing the size of the electrode holder increases the operating life of the insert.

EXAMPLE VIII Use of zirconia insert cathode in oxidizing atmosphere The apparatus used was of the type shown in FIGURE 2. The torch consisted of a inch diameter watercooled copper electrode holder having a inch diameter by /1 inch long, high density stabilized zirconia insert. The electrode was mounted in a inch nozzle. Oxygen gas at the rate of 95 c.f.h. was passed around the cathode through the nozzle while an arc of 300 amperes and 99 to 106 volts was maintained between the insert cathode through the nozzle to a water-cooled nozzle anode. Under these conditions the torch operated for 2 /2 hours before failure of the cathode.

EXAMPLE IX Use of zirconia insert cathode in methane EXAMPLE X Yttrium oxide insert cathode Apparatus of the type shown in FIGURE 2 was used. The electrode consisted of a 0.7 inch diameter copper electrode. A 0.086 inch dia. hole of /8 in. deep was drilled in the face of the copper electrode. This hole was filled with yttrium oxide powder. Argon gas at 27 c.f.h. was passed around the cathode and out through a watercooled nozzle having a inch diameter while an arc of 47 volts and 110 amperes was maintained between the insert cathode and a workpiece. The are was maintained for 10 minutes with no visible torch damage. Operation A in argon gave a very stable arc over a gas flow rate range of 1060 c.f.h.

- EXAMPLE XI Magnesium oxide insert cathode Apparatus of the type described in Example X above was used with magnesium oxide powder as the cathode insert. Argon gas at 27 c.f.h. passed around the cathode and out through the nozzle while an arc of 52 volts and 102 amperes was maintained for 5 minutes between the insert cathode and the workpiece.

EXAMPLE XII Tantalum oxide insert cathode Apparatus of the type described in Example X above was used with tantalum oxide powder as the cathode insert. Argon gas at 27 c.f.h. passed around the cathode and out through the nozzle while an arc of 51 volts and 102 amperes was maintained for 4 minutes between the insert cathode and the workpiece.

EXAMPLE x111 Strontium oxide insert cathode Apparatus of the type described in Example X was used with the exception that a powdered insert of strontium oxide inch in diameter was used. Argon at the rate of 45 c.f.h. was passed around the cathode and through the nozzle while an arc of from 200 to 300 amperes at 62 volts was maintained between the cathode through the nozzle and a workpiece. The torch operated for several minutes without damage.

EXAMPLE XIV Calcium oxide-strontium oxide insert cathode All of the dimensions as well as the type of apparatus was the same as in Example XIII. The insert consisted of a 50-50 mol percent mixture of calcium oxide and strontium oxide. Under the same gas flow the insert operated for several minutes without faliure at currents up to 350 amperes at 62 volts.

EXAMPLE XV Strontium oxide insert cathode in reactive atmosphere Apparatus of the type described in Example XIII was used with the exception that the powdered strontium oxide insert was .125 inch in diameter. Oxygen at the rate of c.f.h. was passed around the cathode in the same manner while the same type of arc, at 300 amperes and volts was maintained. The insert operated for about 25 minutes without failure.

EXAMPLE XVI Tantalum carbide insert in carbon dioxide atmosphere The apparatus was used the same as in Example IV excepting a solid tantalum carbide rod .144 inch in diameter by /4 inch long was used as the insert. Carbon dioxide gas was passed around the cathode at an undetermined rate while the same type of are at 300 amperes and 90 volts was maintained for 14 minutes without noticeable erosion of the cathode.

EXAMPLE XVII Lanthanum oxide insert in oxidizing atmosphere The apparatus used was the same as in Example IV excepting the insert consisted of a .086 inch diameter x inch long powdered lanthanum oxide. Oxygen at the rate of 95 c.t.h. was passed around the cathode in the same manner. Also in the same manner, an arc of from 200 to 250 amperes and 86-110 volts was maintained for about 5 minutes without erosion of the cathode.

EXAMPLE XVIII Calcium oxide insert cathode The torch consisted of a 0.480 inch diameter watercooled copper electrode having a 0.086 diameter by inch powdered calcium oxide insert. Argon gas at the rate of 4-5 c.f.h. was passed around the cathode through a inch nozzle while an arc of 500 amperes and 56 volts was maintained between the cathode through the nozzle to a workpiece for one hour. There was substantially no erosion of the cathode.

EXAMPLE XIX Gadolinium oxide insert cathode This apparatus was the same as in Example XVII excepting the use of a /8 inch nozzle and a powdered gadolinium oxide insert 0.89 inch in diameter by A5 inch deep. Argon was fed to the torch at the rate of 45 c.f.h. The arc had a current of 250 amperes at from 37-43 volts; After 24 minutes there was substantially no erosion at the cathode.

EXAMPLE XX Lanthanum oxide insert in inert atmosphere All of the conditions were the same as in Example V excepting the insert material and the arc current and voltage. The insert was powdered lanthanum oxide. The are current varied from 150 to 300 amperes at from 32- 40 volts. There was substantially no erosion of the cathode after 13 minutes.

EXAMPLE XXI Samarium oxide insert cathode All of the conditions were the same as in Example V excepting the insert material and the arc current and voltage. The insert was powdered Samarium oxide. The are current varied from 200 to 300 amperes at from 43 to 47 volts. The cathode operated for 6 minutes without substantial erosion.

EXAMPLE XXII Zirconium carbide insert cathode All of the conditions were the same as in Example V excepting the insert material and its length and the arc current and voltage. The insert was powdered zirconium carbide having a length of A inch. The are current varied from 300 to 400 amperes at from 48 to 54 volts. The cathode operated for 7 minutes without substantial erosion. Argon at the rate of 45 c.f.h. was passed through the torch.

EXAMPLE XXIII Annular insert cathode The cathode consisted of a 0.7 in. dia. copper electrode having a water-cooled copper tip. A circular cavity 0.124 in. I.D., 0.190 in. OD. and 0.060 in. deep was machined in the flat face of the copper tip. The relatively open torch nozzle had a diameter of about A; in. Stabilized zirconia powder was packed into the annular insert cavity in the cathode face. Argon gas at 12 c.f.h. was passed through the torch and an arc of 22 volts and 200 amperes was maintained to a water-cooled copper workpiece. The torch was tested at currents as high as 380 amperes and the arc was observed to cover substantially the entire insert region. A magnetic field might be used to aid in spinning the arc around the entire insert region.

EXAMPLE XXIV se of electrode with two inserts Two 0.086 in. holes A" deep were drilled in a fiatfaced copper holder. The centers of the holes were "3&2" apart. Thus the holes were separated by about of solid copper. Both holes were packed with stabilized ZrO powder. The cathode was initially operated in argon with a transferred are using a dia. nozzle. However, the point of arc attachment could not be observed so an open nozzle was used. (After operating with a nozzle, it was evident that at some time the arc had originated from both Zr inserts.) Operating at 120 amps with the open nozzle, the arc was attached to only one insert. As the current increased to 150 amps, there was a faint flow from the other insert. With a further increase in current to 170 amps, there was an are from both inserts that appeared of equal intensity. The arcs converged at a point approximately below the face of the copper to form one arc column.

Argon flow was 45 c.f.h. and the arc voltage was 26 volts.

EXAMPLE XXV Use of electrode with three inserts Three holes 0.086 dia. x A" deep were packed with ZrO The holes were equally spaced apart in a flat-faced copper tip of about /2 in. dia. A glass nozzle was used so that the arcs could be easily observed.

The cathode would emit from only one insert until the other has been conditioned by arcing. An arc was obtained separately from each insert by using a carbon rod for short starting. The edge of the insert holder nearest to the insert from which an arc was desired was contacted and the arc would initiate from that insert. After all inserts had been conditioned, the cathode was withdrawn about up inside the dia. glass nozzle and the current was gradually increased while using an argon atmosphere. At about 250 amps there was an arc from two inserts. At 380 amps all three inserts were emitting. The voltage was 30 volts. A change in the shape of the arc column occurred when each additional arc started. The are column did not appear to be any larger than with one arc. Upon decreasing the current, there were 3 arcs down to 250 amps and 2 arcs at the lowest generator setting (110 amps).

No loss of copper was observed.

In addition to the use of an electron holder having a low melting point relative to the insert, the following example shows that a holder having a higher melting point relative to the insert can also be used. This indicates that a wider variety of combination of materials can be used as well as less water cooling.

EXAMPLE XXVI Use of higher melting point electrode holder A inch diameter by 3 inch long molybdenum rod was used as the holder for a 50-50 mol percent mixture of CaOSrO insert. The insert was .140 inch in diameter by /3 inch long. This combination was wedged into a 4 inch diameter cavity in a second electrode made of copper and having a inch diameter. This electrode was mounted in a glass nozzle having a diameter of inch. Argon gas at the rate of 45 c.f.h. was passed around the cathode through the nozzle while an arc of from 180 to 250 amperes at from 2530 volts was maintained from the cathode through the nozzle to a workpiece. Oxygen was then bled into the system and areas of oxidation of the molybdenum rod observed. There was no oxide observed within 1 inch of the copper holder and no oxide within inch of the end containing the insert. Molybdenum oxide vaporizes at around 800 C. while the oxide is formed at a much lower temperature. Therefore, for 7 inch, the end of the molybdenum rod containing the insert was above about 800 C. while the remainder of the rod was relatively cool. An electrode combination such as described would be useful for cooled torches operating at high current.

EXAMPLE XXVH Insert cathode with powder feed Apparatus of the type shown in FIGURE 1 was used. The torch consisted of a .480 inch diameter water-cooled electrode holder having a .086 inch diameter zirconia insert. An arc of from 120 to 150 amperes at 45 volts was maintained for several minutes between the insert cathode through a inch nozzle, to an anode workpiece. Argon gas containing stainless steel powder was fed through the torch at the rate of 20-60 c.f.h. There was no erosion of the cathode.

EXAMPLE XXVIH Zirconium-silver insert In this example, apparatus of the type of FIGURE 2 was used. A inch diameter by 4; inch deep cavity was drilled into a inch water-cooled copper holder. A mixture of weight percent zirconium and 30 weight percent silver powder was then compacted into this cavity. Oxygen gas at the rate of c.f.h. was passed around the electrode through a 4 inch nozzle while an arc of 500 amperes at 88 volts was maintained from the electrode through the nozzle to an anode workpiece for 35 minutes without failure.

A powdered zirconium insert of the same size will operate for about 5 minutes at 300 amperes before failure.

EXAMPLE XXIX Use of insert in air In this extmple, apparatus of the type of FIGURE 2 was used. A A by inch zirconium insert was brazed into a cavity formed in a inch diameter water-cooled copper holder. Air at the rate of c.f.h. was passed around the electrode through a inch nozzle while an arc of 300 amperes at volts was maintained from the electrode through the nozzle to an anode workpiece for about 7 hours without failure of the electrode.

What is claimed is:

1. A non-consumable electrode capable of maintaining a stable electrical arc in a reactive gas atmosphere comprising a fluid cooled metal holder having a high heat conductivity and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium, provided in said holder as the arc attaching portion of said electrode.

2. Electrode according to claim 1 wherein said insert is metallurgically bonded to said fluid cooled metal holder.

3. A non-consumable electrode capable of maintaining a stable electrical'arc at high current levels in a reactive atmosphere comprising a fluid cooled metal holder having a high heat conductivity and an insert of at least one oxide of the metals taken from the class consisting of zirconium, thorium, lanthanum, and strontium, provided in said holder as the arc attaching portion of said electrode.

4. A non-consumable electrode capable of maintaining a stable electrical arc in an oxygen atmosphere comprising a fluid cooled holder made from at least one metal taken from the class consisting of copper, silver, aluminum, brass, and steel; and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium, provided in said holder as the arc attaching portion of said electrode.

5. A non-consumable electrode capable of maintaining a stable electrical arc in a nitrogen atmosphere comprising a fluid cooled holder made from at least one metal taken from the class consisting of copper, silver, aluminum, brass, steel, molybdenum, columbium, tantalum, and tungsten and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium, provided in said holder as the arc attaching portion of said electrode.

6. A non-consumable electrode capable of maintaining a stable electrifiaharciiii ani't'rogen-hydrogen atmosphere comprising a fluid cooled holder made from at least one metal taken from the class consisting of copper, silver, aluminum, brass, steel, molybdenum, columbium, tantalum, and tungsten and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium, provided in said holder as the arc attaching portion of said electrode.

7. A non-consumable electrode capable of maintaining a stable electrical arc in a carbon monoxide atmosphere comprising a fluid cooled holder made from at least one metal taken from the class consisting of copper, silver, aluminum, brass, and steel and an. insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum, and strontium, provided in said holder as the arc attaching portion of said electrode.

8. A non-consumable electrode capable of maintaining a stable electrical arc in a carbon dioxide atmosphere comprising a fluid cooled holder made from at least one metal taken from the class consisting of copper, silver, aluminum, brass, and steel, and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum, and strontium, provided in said holder as the arc attaching portion of said electrode.

9. A non-consumable electrode capable of maintaining a stable electrical arc in a methane atmosphere comprising a fluid cooled holder made from at least one metal taken from the class consisting of copper, silver, aluminum, brass, and steel, and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum, and strontium, provided in said holder as the arc attaching portion of said electrode.

10. A non-consumable electrode capable of maintaining a stable electrical arc in a reactive gas atmosphere comprising a water-cooled copper holder, and a zirconium insert metallurgically bonded to said copper holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

11. A non-consumable electrode capable of maintaining a stable electrical arc in an oxygen gas atmosphere comprising a watercooled copper holder, and a zirconium insert metallurgically bonded to said copper holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

12. A non-consumable electrode capable of maintaining a stable electrical arc in a nitrogen gas atmosphere cornprisim a water-cooled copper holder, and a zirconium insert metallurgically bonded to said copper holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

13. A non-consumable electrode capable of maintaining a stable electrical arc in a nitrogen-hydrogen gas atmosphere comprising a water-cooled copper holder, and a zirconium insert metallurgically bonded to said copper holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

I l-t. A non-consumable electrode capable of maintaining a stable electrical arc in a carbon monoxide gas atmosphere comprising a water-cooled copper holder, and a zirconium insert metallurgically bonded to said copper holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

15. A non-consumable electrode capable of maintaining a stable electrical arc in a carbon dioxide gas atmosphere comprising a Water-cooled copper holder, and a zirconium insert metallurgically bonded to said copper.

holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

. 16. A non-consumable electrode capable of maintaining a stable electrical arc in a methane gas atmosphere comprising a water-cooled copper holder, and a zirconium insert metallurgically bonded to said copper holder, at the arcing end thereof and said zirconium insert being the arc attaching portion of said electrode.

17. Electrode as defined in claiml wherein said insert is cylindrical in shape.

18. Electrode as defined in claim 17 wherein said insert has a length of from about to about inch.

19. Electrode as defined in claim 17 wherein said insert has a length of about inch.

20. Electrode as defined in claim 1 wherein said insert is an annular ring.

21. Electrode as defined in claim 1 wherein a plurality of said inserts are metallurgically bonded to said copper holder.

22. A non-consumable electrode capable of maintaining a stable electrical arc in a reactive gas atmosphere comprising a fluid cooled metal holder having a high heat conductivity and an insert consisting of silver mixed with at least one metal taken from the class consisting of zirconium, thorium, lanthanum, and strontium, provided as the arc attaching portion of said electrode.

23. An arc torch comprising in combination a fluidcooled metal electrode holder having a high heat conductivity and an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium, said insert being metallurgically bonded to said holder and being the arc attaching portion of said electrode; a gas directing nozzle spaced from and adjacent the tip of said electrode holder; means for feeding a reactive gas around said electrode holder; and means for connecting said electrode holder to a source of power for drawing an arc from said insert to a workpiece which is also connected to said power source.

24. A method for Working materials with an electric are which comprises striking an electric arc from an electrode consisting of a fluid-cooled high heat conductivity metal holder having an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum, and strontium, said insert being the arc attaching portion of said electrode; maintaining such are in a reactive gas atmosphere so as to produce a hot arc gas and then directing the hot arc gas into contact with the material to be worked.

25. Process according to claim 24 wherein the reactive gas is air.

26. Process according to claim 24 wherein the reactive gas is oxygen.

27. Process according to claim 24 wherein the reactive gas is nitrogen.

28. Process according to claim 24 wherein the reactive gas is carbon dioxide.

29. Process according to claim 24 wherein the reactive gas is nitrogen-hydrogen mixture.

30. Process according to claim 24 wherein the reactive gas is carbon monoxide.

31. A method for cutting metals which comprises connecting a workpiece to be cut and an electrode consisting of a water-cooled high heat conductivity metal holder, having an insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium metallurgically bonded to said holder in circuit relationship; striking an are between said insert and said workpiece; feeding a reactive gas around said electrode and into the region of said arc; applying the resulting arc effiuent against said workpiece; and cutting such metal workpiece with such are efiluent.

32. Method according to claim 31 wherein said reactive gas is oxygen.

33. A method for working materials with an electric are which comprises striking an electric are from an electrode consisting of a water-cooled copper holder having a zirconium insert, said insert being the arc attaching portion of said electrode; maintaining such are in an oxygen atmosphere so as to produce a hot arc gas and then directing such hot arc gas into contact with the material to be worked.

34. A method for Working materials with an electric are which comprises striking an electric arc from an electrode consisting of a Water-cooled copper holder having a zirconium insert, said insert being the arc attaching portion of said electrode; maintaining such are in a nitrogen atmosphere so as to produce a hot arc gas and then directing such hot arc gas into contact with the material to be worked.

35. A method for working materials with an electric arc etiiuent which comprises connecting the material to be worked in circuit relationship with an electrode consisting of a water-cooled high heat conductivity metal holder having metallurgically bonded thereto a high density insert of at least one metal taken from the class consisting of zirconium, thorium, lanthanum and strontium; striking an arc between said insert and said material to be worked; maintaining such arc in a reactive gaseous atmosphere; and applying the resulting arc etfiuent against said material.

References Cited by the Examiner UNITED STATES PATENTS 794,902 7/05 Vogel 313354 1,007,869 11/11 Hill 313-354 1,589,017 6/26 Lincoln 21974 2,186,319 1/40 Bilton 219- 2,544,711 3/51 Mihhalapov 219-74 2,587,331 2/52 Jordan 219l21 2,594,905 4/52 Gallagher 219-446 2,640,135 5/53 Cobine 219 2,694,763 11/54 Muller 21974 2,863,981 12/58 Thomas et al. 219-74 2,874,265 2/59 Reed et al. 219121 2,886,692 5/59 Oyler et al. 21969 2,922,028 1/60 Butler et a1. 219-145 2,960,594 11/60 Thorpe 21975 3,102,949 9/63 Browning et al. 219-445 FOREIGN PATENTS 620,227 3/49 Great Britain.

625,201 2/36 Germany.

RICHARD M. WOOD, Primary Examiner.

Claims

1. A NON-CONSUMABLE ELETRODE CAPABLE OF MAINTAINING A STABLE ELECTRICAL ARC IN A RELATIVE GAS ATMOSPHERE COMPRISING A FLUID COOLED METAL HOLDER HAVING A HIGH HEAT CONDUCTIVITY AND AN INSERT OF AT LEAST ONE METAL TAKEN FROM THE CLASS CONSISTING OF ZIRCONIUM, THORIUM, LANTHANUM AND STRONTIUM, PROVIDED IN SAID HOLDER AS THE ARC ATTACHING PORTION OF SAID ELECTRODE.