US2422038A - Anodes for intensive arcs - Google Patents

Description

Patented June 10, 1947 ANODES FOR INTENSIVE ARCS Jean Francois Parisot, Paris, France, assignor to Societe; Le Garbone Lorraine, a corporation of France No Drawing. Application July 25, 1945, Serial No. 607,093. In France January 17, 19 42 In a number of prior French Patents of Le Carbone Lorraine anodes for intensive arcs are described which are constituted by a tubular casing termed the bark or sheath which is made ofcommerciallyfpure carbon and of a central core formed. by a special composition contained inside said sheath.

These anodes, when submitted to an electric are producing a current density of about 0.6 to 1.2 amperes per square millimeter of their cross sectional area, may produce spontaneously the phenomenon generally termed Beck effect. It is known t this phenomenon appears when the .density of current is gradually increased; it is characterized by an elevation of a few volts in the .voltagedrop in the arc, by a deepening of the crater reaching about one half of the diameterof the anode, by a considerable brilliancy of the gaseous mass at the bottom of the crater, by a rapid increase of this brilliancy when the density of current; increases and finally by a particular appearance of the anodic flame.

In the French Patent 770,345 of June-9, 1933, L8 Carbone Lorraine has described ,an anode the core of whichis formed by a body of carbon to which is incorporated, siliconor silicon carbide. The same applicant company has described in the French Patent 79'7-,2 0 8.of January 25, 1935, a core containing one or more metals the atomic number of which is comprised between 22 and 29 and eventually compounds of rare earths.

The comparison of the intensive arc anodes established in conformity with the above mentioned patents, with normal intensive arc anodes the core of which is mineralized with fluorides or oxides of rare earths, has shown that silicon or silicon carbide reduces by about 40 to 60% the brilliancy produced by the standard anodes, whereas metallic iron causes only a 10 to loss of this brilliancy. On the contrary, it is possible to rise by 5 to 20% above the standard anode brilliancy by associating in suitable proportions the iron and rare earths in the core.

Experience has shownhowever that the anodes having a score containing metallic iron show certaindrawbacks. Pulverulent iron is oxidized either before or after its incorporation in the anode. During operation, this iron oxide is re,- duced in the vicinity of the crater, and sparks of molten metal spurt out and are blown away by the reduction gases so that metal particles mayengage the optic system of the projecting apparatuses and becomeincrusted therein.

,My invention has iorits objects-to remove this drawback and 1 tofurther the manufacture oi the 15 Claims. (01. l76 121) aucde- I con i ts in p n i l in replacing the iron by certain nono gydable ferrous alloys conta nin i Pa ticula n 9 more metals the atomic numbers are comprised inclusively beween 22 nd. 28.-

.Such are chromium and nickel-containing austenitic or martensitic steel containing eventu ally other metals such as aluminium, together withcarbon, silicon, etc,

However, these stainless alloys are tough and diflicult to crush; on the other hand the presence of important contents of nickel and chromium increases to an eg ia gger ated degree the green radiations in the light.

In conformity with my invention, I may replace iron by nonoxydable ferrosilicon which it is easy to crush, I have just stated that silicon considerably reduces the luminous efiiciency of the intense arc lncontradistinction with iron. It was therefore not possible to foresee that the application to the anodes of ferrosilicon rich in silicon might lead to an advantageous luminous efiiciency as disclosed hereinafter. Experience shows that from this standpoint, ferrosilicon acts substantially in the same manner as iron even with a proportion of 2 atoms of silicon for 1 atom of iron, in spite'of the higher proportion of silicon.

Commercial ferrosilicons belong generally to the types 20-25%, 40-50% or -80% of silicon. All are inoxidable and unaltered in the presence of moist air and they resist the chemical attack of most acids. ingly easy degree when their contents in silicon increases. The intermediary type containing .0 C fi li l ce ned? Su an l the formula: SizEe.

The manufacture of my improved intensive anodes mayb executed in accordance with the known methqd Th car qn sh ath are fir a e d a thick paste is injected therein which is constituted by subdivided carbon, pulverulent ferrosilicon and an organic binder. This paste may include moreover other mineral substances finely crushed and intimately admixed therewith. The carbon is then baked for hardening the core.

It is also possible to introduce inside the carbon sheath, a solid hard rod of carbon and ferrosilicon-with the eventual addition of further mineralmaterial. These substancesare agglomerated by means of a binding material liable to be carbonized such .as coal tar ,for instance. When th ee pqsitie ha en d a hro apress so as to ,iormrods of suitable cross-sec They are crushed to anincreas- 3 tion, it is hardened through calcination in a reducing medium at a high temperature. The rods thus prepared are then stuck inside their sheaths.

4 standard commercial type known under the trade name Orlux 544.

Example 4.By substituting weight for weight ferrosilicon at 45% for that containing 25% of In the following example, the final composi- 5 silicon, one obtains the compositions IV bis, V tion is defined by t proportions o miheralizing bis, VI bis, which are respectively similar to commaterial on one hand and carbon on the other; positions IV, V, VI. For anodes of '7 mm. diamthese proportions are given out by weight. eter and under same conditions for comparisons,

Example 1.Difi"erent anodes have received a the following results are obtained for 40 and 50 core having the following composition: amperes.

Table I Table IV No n I II III Intensity IV bis Vbis v1 bis 'gf ffgf Ferrosilicon at 50 G8 80 40a b 92 98 122 100 carter 1111111IIII:IIIIIIIIIII IIIIIIII 50 32 503 61 72 98 Anodes the diameter of which is 7 mm. as in The composition VI bis operating under 40 common use f cinematographic projections have 20 amperes produces substantially the same light spontaneously produced the Beck efiect for noras the test anode under p mal intensities of 40-50 amperes. With the new It is possible thus With the new anodes, es anode in conformity with the invention, and for sired. to save electric energy or else fit a same length of are as for the anode chosen for y an increase in luminous efficiencycomparison, a higher drop in voltage is observed The influence of ferrosilicon at 45% 011 the which lies between 2 and 4 volts according to the Voltage at the terminals of the are remains of intensity used while the luminous efiiciency lies the Same magnitude as that of ferrosilicon at between 95 93% and 70% of that f the test 25%: the increase is all the greater when the ode for d with only rare earths, said mci y proportion of rare earths contained in the core decreasing with increasing current densities. is Smaller- Example 2.By replacing weight fo weight The advantages of the invention will appear in the Formulae I, II, III, the ferrosilicon at 25% from the following indications. It is possible to by that containing 5 of smooth the compostchoose a composition rich in rare earths with tiohs I his, II his, n his are obtaihod The enough ferrosilicon for increasing the brilliancy resulting arcs are comparable to those of the corof the Crater as compared to thefitjenderd responding compositions I, II; III; thus for an- The compositlon VII cohtammg 33% of odes of 7 mm. the composition I bis operating un- Compounds of rare earths and 41% of silicon at o amperos has provided 3 loss light than ferrosilicon with 21% of carbon provides the composition I but 6% more at ampere the results recorded in Table V. Said table shows The very high contents of ferrosilicon at 45% 40 the Comparison between the usual ah0de have lesser advantages as concerns efiiciency, ihg diameters of 7 and 3 opel'etmg at chiefly for high current, densitie different current intensities of 30 to 65 amperes,

Example 3.Rare earths of the eerie group the light intensities h given out as under the form of commercial fluoride are asso- 45 e of that provlded by the test carbons ciated with ferrosilicon containing 25% silicon,- tammg only rare earths of the standard grade which leads to the following compositions; already mentioned Orlux 544.

Table II Table V No IV V VI 50 Intensity of the current in amperes Diameter of the anode in mm.

Ceric fluorides 10 2o 39 30 as 40 45 50' t5 Fcrrosilicon 70 41 Carbon 20 20 20 The luminous efiiciency when compared with 105 82 the test anode comprising only rare earths increases with the contents of the latter and reach On the contrary, if an allowable fraction of the and pass beyond those of the test anode in the luminous efficiency is sacrificed, it is possible to case of the composition VI. In the case of an- 60 use a composition containing less rare earths odes of 7mm. the following results are obtained: which leads to a substantial economy. In particular, it is possible to use a composition VIII Table containing about 21% of compounds of rare earths, 53% of ferrosilicon containing 45% Si Intensity IV V VI afi gfi and 26% of carbon. This composition allows as a matter of fact an economy of 53 to 62% of the 88 87 113 rare earths, taking into account all the variable 07 so 98 100 interfering conditions. 74 97 100 It is finally possible to chose intermediary compositions, those containing the less rare earths The composition VI is therefore at least equal leading to the most important economies at the to the composition having rare earths as a base. expense of the luminous efiiciency while those But the latter containing about 60-70% of rare containing the most rare earths lead to a smaller earths are much less economical. All the combut yet substantial economy with a high lumiparisons have been made with anodes of the nous efficiency. For the composition VII, this aunties "scone-my varies between and 20%"accordin'g to the conditions of use. i

In the economical position of to-day, the novel compositions described are of advantage as the rare earths are generally imported by sea from long distances. The use of ferrosilicons as partial or complete substitutes for the rare earths allows thus such importations to be done away with partly or totally.

In particular, if it is desired to totally eliminatethe rare earths, while retaining the same luminous efficiency, it is sufiicient to use ferrosilicon-containing anodes. with mean current densities for instance:

1 aJmm. for 6 mm. diameter 0.8-0.85 a./mm. for 8 mm. diameter 0.75-0.8 a./mm. for 9 mm. diameter 0.65-0.70 a./mm. for 13 mm. to 16 mm. diameter.

When it is desired to operate with higher current densities without reducing the luminous efficiency, it is preferable for the ferrosilicon to be used in proportions which are lower when the rate of utilization, i. a, the density of current, is higher, provided there are incorporated simultaneously rare earths. Whatever the rate of operation may be, there is always an economy made in rare earths, taking into account all the modifications which may appear for instance in the density of the core and in the rate of combustion of the coal.

The association of ferrosilicons with rare earths is also preferable when a supply of low voltage current is available as is often the case in projection halls. For this kind of application,

the above referred to composition VIII is particularly available.

Generally speaking, it has been foundthat ferrosilicon has a remarkable stabilizing action on the arcs which considerably reduces the fluctuations in light produced by the rare earths in intense arcs.

On the other hand, it is known that the coupling of two similar anodes of the normal intense type allows the obtention of an alternating intense arc. with pure ferrosilicon are not suitably applicable in such a case. Anodes containing ferrosilicons with a sufiicient amount of rare earths are perfectly satisfactory. For instance, the composition VIII has provided with 8 mm. carbons a luminous eiiiciency which is higher by 6% than that of the test anode Orlux 542 containing rare earths, under an intensity of 80 amperes; for 85 amperes the eiiiciency falls underneath that of the test anode. This composition allows a clear economy of 10% in rare earths.

In addition to the principal components which are ferrosilicon and. compounds of rare earths, it is possible to incorporate to the cores of the improved anodes, metals having atomic numbers comprised between 22 and 29 or alloys of such metals with one another or with silicon. The results are similar but the corresponding anodes are more expensive and. generally speaking of minor advantages for general utilization, so that they should be reserved for special applications.

Of course the present invention is by no means limited to the form of execution and numeric values given out by way of examples. The different details of execution and application may vary as desired without widening the scope of the invention.

Experience has shown that anodes What I claim is: I

1. An anode for intensiveelectric'arcs adapted to produce spontaneously the Beck effect, comprising a sheath of carbon and a core constituted by-a base of commercially pu're carbon admixed with an inoxidable ferrous alloy.

2. An anode for intensive electric arcs adapted to produce spontaneously the Beck .efiefc't. comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with an inoxidable ferrous alloy, containing at least onemetal having an atomic number comprised between 22 and 29 inclusively.

3. An anode for intensive ele'ctric'arcs adapts to. produce spontaneously the Beck .efieot, comprising a sheath of carbon and a core constituted bya base of commercially pure carbonadmixed with ferrosilicon rich in silicon.

4. An anode for intensive electric arcs adapted to produce spontaneously the Beck effect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with an inoxidable ferrous alloy and rare earths.

5. An anode for intensive electric arcs adapted to produce spontaneously the Beck effect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with a ferrosilicon containing between about 25 and 45% of silicon and compounds of rare earths.

6. An anode for intensive electric arcs adapted to produce spontaneously the Beck effect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed. with a ferrosilicon containing between about 25 and 45% of silicon and a metal the atomic number of which is comprised between 22 and 29.

7. An anode for intensive electric arcs adapted to produce spontaneously the Beck effect, comprising a sheath of carbon and. a core constituted by a. base of commercially pure carbon admixed with a ferrosilicon containing between about 25 and 45% of silicon, compounds of rare earths and a metal the atomic number of which is comprised between 22 and 29 inclusively.

8. An anode for intensive electric arcs adapted to produce spontaneously the Beck efiect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with ferrosilicon and alloys of a metal having an atomic number comprised between 22 and 29 inclusively.

9. An anode for intensive electric arcs adapted to produce spontaneously the Beck eflect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with ferrosilicon and alloys of a metal having an atomic number comprised between 22 and 29 inclusively and silicon.

10. An anode for intensive electric arcs adapted to produce spontaneously the Beck effect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with ferrosilicon, alloys of a metal having an atomic number comprised between 22 and 29 inclusively and rare earths.

11. A composition for the core of anodes adapted for use in intensive arcs producing the Beck eiiect containing about 50 to of ferrosilioon with silicon contents between 25 and 45% and 50 to 20% of commercially pure carbon.

12. A composition for the core of anodes adapted for use in intensive arcs producing the Beck efiect containing between about 10 to 40% of compounds of rare earths, between about 70 and 40% of ferrosilicon having contents comprised substantially between 25 and 45% and about 20% of carbon.

13. An anode for intensive electric arcs adapted to produce spontaneously the Beck efiect, comprising a sheath of carbon and a core constituted by a base of commercially pure carbon admixed with a ferrosilicon containing betweenabout 25 and 45% of silicon.

14. An anode for intensive electric arcs adapted to product spontaneously the Beck effect, comprising a sheath of carbon and a core containing about 38% of compounds of ceric earth, about 41% of ferrosilicon containing about 45% of silicon, and about 21% of carbon.

15. An anode for intensive electric arcs adapted 15 Number to produce spontaneously the Beck effect, comprising a sheath of carbon and a core containing about 21% of rare earths, about 53% of ferrosili- 'con containing 45% of silicon and about 26% of carbon.

JEAN FRANCOIS PARISOT.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 7 Name Date 955,273 Ladofif Apr. 19, 1910 2,140,881 Parisot Dec. 20, 1938 FOREIGN PATENTS Country Date 456,040 Great Britain Nov. 2, 1936 475,252 Great Britain Nov. 16, 1937