US RE15466 E
Description (OCR text may contain errors)
Rei ssnied 0a. 10, 1922.
Re.15,466 p UNITED STATES PATENT OFFICE.
THOMAS E. MURRAY, J 11., OF BROOKLYN, NEW YORK.
METHOD OF ELECTRIC WELDING.
in Drawing. Original 1m. 1,281,636 and 1,281,637, dated umber 15,1915, Serial 1m. 215,710 and 215,711, filed February 6, 1918. Application for reissueflled January 16, 1922. Serial No. 529,783.
To all whom it may cancer-n:
Be it known that I, THOMAS E. MURRAY, J r., a citizen of the United States,residing at Brooklyn, New York,.have invented a certain new and useful Improvement in Methods of Electric \Velding, of which the following is a specification.
The invention is an improvement in the art of electricwelding, whereby a weld can be secured of a strength equal to that of the metal welded, and a single, integral homegeneous body may be formed, and this can be one continuously over a contactarea of considerable extent with great uniformity and great econom of time and labor.
As common y practised, electric welding is a sticking together of the opposing bodies by rendering their surfaces plastic or pasty and ressing them into more or less close contact. fhe result is attraction between the molecules at the surfaces of the respective bodies, caused first by rendering-said molecules mobile by heat, and then moving them by the pressure into closer proximity and sointo their fields of mutual attraction. In old physical nomenclature, the surfaces are then said to adhere.
While temperature of a degree suflicient to make the opposing surfaces adhesive will effect a union, the strength of said union is a to destruction; nor from the tests of one joint can the strength of other joints certainly be, inferred. A given joint may be amply strong to meet conditions involving small strain, as, for example, the uniting of electrical line conductors or the parts of' utensils or light structures, but it may be wholly inade uate to withstand the demands of heavy loa s or shocks orof moving machinery.
The effort to make stronger joints has led to moderately increasing current strength, or both current strength and current duration, for the purpose of obtaining greater plasticity or fluidity of the metal; but this leads primarily to burning of the metal. Increase of pressure leads to greater extrusion of metal at the joint which is intensified when the fluidity or plasticity of the metal is augmented. The result. is then merely surface adhesion; as lJHfQlTP- OVHI a larger area. To
increase the duration of the current deteriorallps the physical condition of the metal it- I Another cause of uncertainty and unreliability of the welded joint is the great dif-v ficulty, and often practical impossibility, of insuring a uniform current flow per unit area of welding surface. If other materials are present in the metal, especially substances --of lower conductibilty, the current will cause unequal heating of the surface, with a result that one part may be burned before a proper plastic condition is produced elsewhere. So also if the surfaces exhibit protuberances which may contact before the more depressed portions, the current may burn or the protuberances before the lastnamed portions are suitably heated, or even 1f the opposed surfaces are not rigorously parallel, the current will become concen trated and so affect the portions of said surfaces which first make contact. Increasing the current to obtain greater plasticity or' continuing it for longer periods, or using greater mechanical pressure does not over- 7 come these difficulties .I have discovered after much study and research, that I can produce' an electrically welded union possessing a strength as great as that of an integral mass of the same ma terial of like cross-sectional area by subjecting the bodies to be welded to an electric current of extremely and'abnormally high ampere strength existing for a 'very'brief period of time. t
' When the area is small, say about five square inches or under, I prefer to use cur rents of about one hundred thousand amperesto the square inch When the area is large, say about twenty square inches or above, I prefer to use currents .of about fifty 9 square inches in less than three-seconds. I
am actually welding two pieces ofsteel having an area of five square inches in less than one-half a second; two pieces of steel having a thickness of .109 inches and a length of eightydive inches in less than two seconds;
two pieces of steel having a. thickness of onesixteenth of an inch and a total length of threehundred and fifty inches in less than three seconds. In each of these cases I am using a current of extremely and abnormally high ampere strength existing for a very brief period of time.
The operation is so rapid that it is impossible to becertain of the stages through which the work passes. I can state nth certainty only the methods used and, the re,.
sults achieved. My theory is as follows:
The weld is not caused by surface mole;- ular attraction or adhesion but by a complete dissociation of the molecules for a oertain distance inward from the surface of eaclr body, followed by the intermingling of the molecules ofone body with those of the other, and their mutual attraction developed within the momentarily gaseous film. so that the said molecules become united throughout the mass. .Under the old physical nomenclature, theyv cohere It'- the two bodies are of the same material, then, after welding there is no solution of contr.
nuity, and the two bodiessimply become integrally one body' If the two bodies are of di'fiierent materials then while there is still no solution of continuity, a portion of the welded massis compositeand partakes'.
of the nature of'both bodies; that is to say,
if, for example, copper and zinc be the materials a portion of the welded mass will be an alloy or mixture of the two metals.
The enormousl f high temperature developed, gasifiest e metal or metals of the bodies instantly, and in the brief time period.
permits the molecules "to interminglej and cohere. With such ampere strengths there is no time for any burning of the metal or for the conduction of heat away throughthe-mass before the gasificationrof the metal and the inter-mingling of molecules occurs.
()1? course, the temperature. is far above that which would, permit the metal to become plastic or pasty. Because there is complete cohesion of themolecules within the mass the physical condition of the metal. is the same at the place of union asanywhere else. Therefore the same strength everywhere follows as a necessary consequence. This can be accomplished in no other way, so tar as I know. d
When currents of such extreme ampere trode in contact- With all four sides.
ess to use a high voltage.
and naturally so since the intermingling produced isot gases in which the molecules are free and comparatively widely separated. So also there appears to be no limitation of surface areas which can be united. With a suitably strong momentary current it is as easy to weld areas of say twenty square inches as areas of one square inch.
Another advantageous result attending my use of enormously strongcurrent is lhe neutralization of the dillicultiesdue to radiation from the heated bodies to the holding electrodes when the area of contact between said bodies and said. electrodes is largely increased; To take a simple illustration: Assume that two bars m easuri'ng incross sectional area one square inch, are to be united. The best conditions are attained when each bar is inclosed, in a copper elec Iic'ach electrode is one inch in width, then the 'cont aot area of each electrode with its bar is four square inches. As already pointed out, I; can buttrweld. these bars by my process and be certain that the strength at the union Will be equal to thatof the integral met-a1. Suppose,- however, while keeping the area the same, the l form of that area be changed as, to illustrate, let the surface area instead of one square inch in thesha peofa greater. This is increased radiation surface of the bar, and, therefore the heat developed will escape to the electrode niore rapidly than before. This loss 'i-s,as l-have' stated easily counteracted byan increasein the ampere strength of the current. I It 'a current of given high ampere strength will produce a perfect union when. thegcontact area is a square or other regular figure of uniform dimensions. the same result may be obtained when the figure is changed to one in which the dimensions widely differ by increasing the current strength. All that is necessary for a given shape is to go on increasing the current strength until the perfect union is produced. After that, with unchanged conditions as to shape, material,-
etc, the welding'ot like bodies-may be. repeated. indefinitely.
Practical applications to the invention to these long narrow joints are indicated in specific cases referred to above.
lt is unnecessary in carrying out my procl have made good welds using about eight volts on the secondary ol a transformer.
This invention is to be distinguished from the method known as"percussive Welding and from similar processes in which, by means of an uncontrolled condenser discharge a considerable current is passed in an instant through small points or spots of contact such as the ends of wires or rods or the socalled spot welding in which considerable areas are in contact but the welding is effected at separated points in the contact area. My invention is useful in welding considerable areas of contactand making a continuous weld'over such areas by passing the current through substantially the entire area of the contact, the current being proportioned to such area. Examples of the considerable areas to which my invention is applied in this way. are recited Also my process is distinguished in that it uses a steady current (that is, of steady amperage) throughout the period of application, the amperage at the end of the eriod being nearly equal to the average. 11 the percussive methods referred to, the condenser discharge produces a high voltage and a comparatively low amperage which tapers off gradually to zero. And where the time interval'is practically uncontrolled in V the said methods, with my method it varies inversely or in the opposite direction from the variation in current'density, as indicated in the examples given above.
Though I have described with great particularity of detail certain embodiments of my invention yet it is not to understood therefrom thatthe. invention is restricted to the particular embodiments described. Various modificatibns thereof may be made by those. skilled in the art without departure from. the invention as defined in the following claims.
1; The improvement in the art of electric welding, which consists in subjecting the bodies to be united to, a current of extremely high ampere strength and of very brief duration. whereby said bodies are-caused to form a single homogeneous body without solution of continuity.
2. The improvement in the art of electric welding, which consists in subjecting the bodies to be united to a current of extremely high ampere strength and of very brief duration, and thereby producing molecular dissociation at each of the opposing faces of.
said bodies and an intermingling of the dissociated molecules, whereby said bodies are caused to form a single homogeneous body without solution of continuity.
3. The improvement in the art of electric welding, which consists in subjecting two bodies of respectively different metals to a current of extremely high ampere strength and very brief duration. and thereby pro brief predetermined and regulated period of time as distinguished from a sudden uncontrolled discharge.
5. The improvement in the art of electric welding, which consists in subjecting two bodies of respectively different metals to a current of extremely high ampere strength applied for a very brief predetermined and regulated period of time (as distinguished from a sudden and uncontrolled discharge).
6. The improvement in the artof electric Welding, which consists in bringinginto contact and under pressure considerable surfaces of the bodies to beunited, the area of the contact surfaces having a length sub stantially greater than its width, and passing through substantially the entire surface in contact a current of extremely high ampere strength per unit of area of the contact surfaces and of very brief duration.
7. The improvement in the art of electric welding, which consists in bringing into contact and under pressure considerable surfaces of the bodies to be united, the area of the contact surfaces having a length substantially greater than its width, and passing through such bodies a current of extremely high ampere strength per unit of areaof the contact surfaces, and of ye brief duration, the said ampere strength being greater than the ampere strength necessary to accomplish the same result in Welding two bodies of identical material whereof the length of the contact area is equal to the width. thereof.
8. The method of electrically welding. bodies 'whereof the contact area is one in which the length is greater than the Width, which consists in subjecting said bodies to a current of extremely high ampere strength.
tact and under pressure considerable areas of the bodies to be united and passing through substantially the entire area in contact a current of extremely high ampere strength per unit of area of the contact surfaces and of very brief duration.
10. The improvement in the art of electric welding, which consists in subjecting the bodies to be united to a current of extremely high ampere strength and of very brief duration, maintaining the high amperage throughout the period of application of the current.
11. The improvement in'the art of electric welding which consists in bringing into contact and under pressure considerable areas of two bodies of respectively different metals and passing through substantially the entire areas in contact a currentof extremely high ampere strength per unit of areaof the contact surfaces and of Verybrief duration.
12. The improvement in the art of electric welding, which consists in subjecting the bodies to be united to a current of extremely high ampere strength in proportion to the contact area and of a very brief duration varying in an inverse proportion to the cur-,
THOMAS E. MURRAY, JR.