US1146988A - Depositing repair metal across an alternating-current arc. - Google Patents

Description

M. ARENDT. I I-DEPO SIIING REPAIR METAL-ACROSS AN ALTERNATING CURRENT ARC. "VAPPLICATION FILED OCT-23. 1914.

1,146,988; I I Patented July 20,1915.

INVENTOR W ATTORNEYS eity, county, and State f 15 such other I 20 metal.

' 30 length of about 1} 4 STATES PATENT OFFICE.

mon'rou ABENZDT, or new YORK, N. Y., assrcnon r nnmnrcn L. .1. smnum), or P NEW roan, N. Y.

DEPOS ITING REPAIR METAL ACROSS AN ALTERNATING-GURRENT ABC.

To all'wkom, it may concem z Be it known that I MORTON ARENDT, a citizen of the United Eitates, residing in the of New York, have 5 mvented certain new and useful Improvements' in Depositing Repair'Metal Across an Alternating-Current Arc; and I do hereby declare the followin to be a full, clear, r and exact description 0 the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In recentyears extensive use has been.

made of the process .of repairing boilers, and

articles, as are inaccessible cannot readily be handled, by the deposltion of repair 'metal across a direct current are,

playing between the metal to be repaired and thetip of a small electrode of the re air In that process considerable 'fliculty is. experiencedin striking the arc and maintaining it without interruption, and some degree of experience and skill is necessary to the successful carrying out of the operation. The are willnot be maintained until the spot on the metal to be repaired has been Well heated by the electrical energy expended at the point of contact.

' After the are is struck it 1s maintained at a of an inch by skilful mampulation on the part of the operator, and

if it is drawn out'much beyond that length the accompanying decrease in current, due to the increase of the resistance, tends to extin uish the arc. The desirable conditions are, rst, provision for developing the required heating energy at the point of contact, and second, means for maintaining the current value as nearly constant as possi- 40 ble-that is, means for reducing the current variations due to slight alterations of the length of theatre. It is for this latter reason that a ste'adying resistance is always inserted inthe direct current circuit, in series with the electrode. I have discovered that these desirable conditions may be more fully attained by a novel arrangement of alternating current circuit erly proportioned inductance, 1n accordance with the following disclosure, and this discovery is the more remarkable-in view of the fact that it hasheretofore been supposed that alternating current is unsuitable for g I Specification of Letters Patent.

Application filed October as, 1914. Serial No. 868,162;

and

:length of the arc containing a prop-'v carrying on this process of pair metal across the arc, so that it has heretofore been the practice, dation of those skilled in the art, to use a motor-generator for transforming the alternatin current into direct current, wherever a irect current supply is not immedlatel y available.It is the circuit connections and voltages commonly employed used for alternating-current work, the time required to properly heat the surface of the work, where the repairmetal is to be deposited, is almost prohibitive. The welder is constantly trying to strike the are which just as regularly goes only globules ofthe electrode metal are deposited on the work surface, and no homorelatively high initial voltage and inserting a properly proportioned inductance in series and the recommen- -PatentedJuly20,1915.

deposition ofre I In fact true that if v with direct current are out and as a result with the arc, 'I can produce the desired con ditions (a good initial heating energy, jand the maintenance of substantially constant current), to an improved degree, so that the arc may readily be struck and will be maintained, even though the operator varies the to a greater extent than has heretofore been ossible. It will readily be understood t at this increases the facility of the operation not only at its start but throughout, because movements of the hand of the ooerator which would heretofore extinguish the arc, may now occur without extinguishing it. Furthermore, I find that under these conditions, deposition of the repair metal, either on the flator against gravity, may readily be practised with an economy of energy as compared with direct current practice. In fact, only about 60 to 70 per cent. as much energy is required, while a great advantage obtains from the elimination of motor generator sets and the substitution of a simple low cost static transformer; and this saving is accompanied by an increase, rather than a decrease, in the strength of the weld.

In the accompanying diagrammatic drawing I have illustrated a suitable'system.

In this diagram 1 is the article to be repaired; 2 is the repair electrode; 3 is an alternating current source here shown as the and the like, employing iron or steel wire electrodes of from 0.12 inch to 0.19 inch in diameter, results when the voltage applied to the welding circuit is about 110 to 120 volts and the current from 150 to 180 amperes, and the voltage drop across the terminals of the inductance, that is, the induc-' tive voltage component, is between and 105 volts, and the total resistance drop of the system is between 10 and 40 volts, the general rule being that the most economical conditions obtain with the higher inductance and lower resistance drops. For the purpose of attaining the desired resistance drop I may include the adjustable resistance 8 in the circuit or the resistance drop may reside in the leads and the other elements of the circuit. With this described arrangement the power required for proper deposition of the metal to form a homogeneous part of the Work to be repaired, is only from 6%, to 7% kilowatts at about 110-120 volts, while for corresponding results with direct current 10% to 14 kilowatts, that is 150 to 200 amperes at 70 volts, are regularly employed. It will be understood that the inductance 7 may reside in the transformer itself, as by using a transformer in which the magnetic leakage is exaggerated.

If thin metal sheets are to be joined or added to by deposition from the metallic electrodes, the current should be reduced in value by increasing the impedance of the circuit, and the electrodes may. also be reduced in diameter where necessary.

With the above, conditions I find that not only is the welding are readily struck and maintained, but the welding surface is promptly brought to the proper temperature, that is, to such a temperature that the surface becomes incipiently fused or heated to such a degree that the deposited metal will combine therewith homogeneously. This resultis secured whether the work being repaired is placed above or below the electrode, and whether the electrode clamp is provided with a magnetizing coil or not, and whether or not welding powder or flux coatings are used on the electrodes, though'the presence of the latter seems to reduce to some extent the amount of dripping when the metal is to be deposited against gravity. The use, however, of these auxiliaries, namely, the magnetizing coil and flux coatings, is well known in the art and does not form any art of my discovery.

Using t e high inductance and low resistance referred to, I have uniformly made welds having a strength of 46,000 pounds per square inch, somewhat beyond the clastic limit of the structures united by the deposited metal. The break is crystalline in appearance and shows no slag. The weld with a somewhat smaller inductance and slightly greater resistance has substantially the same strength averaging about 44,000 pounds, but the power required is greater, about 9.5 to 10.5 kilowatts, though still slightly less than with direct current. In any case, however, the inductive voltage component should substantially exceed the voltage drop across the arc.

The dropacross the arc will ordinarily vary from about 22 volts to about 30 volts, depending upon the length of the arc. This is a greater variation than can be tolerated in direct current work, but I find that even greater variations can accompan successful welding with my system. .In act, I have successfully welded with the arc voltage varying from 15 to 35 volts.

I have commonly employed a frequency of sixty cycles per second in my work. In general a higher frequency facilitates the work, while lower frequencies tend to make it more difficult. If the available fre uency is too low a static frequency trans ormer,

may be used.

What I claim is: 1. A system for building up upon a metal surface a homogeneous deposit of repair metal, comprising an electrode of the repair metal'connected in an electric circuit with the metal to be repaired, so that an electric arc may be drawn between them, said circuit including a source of alternating current and having inductance of such value that the inductlve voltage component substantially exceeds the voltage drop acrossthe arc.

2. A system for building up upon a metal surface a homogeneous deposit of repair metal, comprising an electrode of the repair metal connected in an electric circuit with the metal to be repaired, so that an electric art: may be drawn between them, a source of alternating electro-motive force in said circuit having a voltage of approximately from 110 to 120 volts, and said circuit having involtage component is from 75 to 105 volts.

3. A system for building up upon a metal surface a homogeneous deposit of repair metal, comprising an electrode for the repair metal connected in an electric circuit with the metal to be repaired, so that an electric arc may be drawn between them, a source of alternating electro-motive force in said cir-- cuit having a voltage of approximately from' 110 to 120 volts, and said circuit having in- In testimon whereof I afiix my signature, ductance of such value that the inductive in presence 0 two witnesses. voltage component is from 75 to 105 volts, MORTON ARENDT. and ohmic resistance of such value that the Witnesses:

5 resistance drop is approximately 10 to 40 KENNETH P. PENNIE,

volts. M. A. BILL.

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