UnitedO States Patent (19) (11) 3,890,168 Shumway (45) June 17, 1975

(54) EXOTHERMIC COMPOSITION 3, 6, 14 E. Rylander et al...... 75/27 3, 60,537 2/1964 Trafton...... 149/37 76) Inventor. Harold A. Shumway, 25529 via 3,726,727 4, 1973 lish, O. l48/24 Brava, Valencia, Calif. 9355 3,740, 99 6/1973 Gammill...... 75/27 22 Filed: Nov. 29, 1972 FOREIGN PATENTS OR APPLICATIONS 21) Appl. No.: 310,330 317,287 6/1963 France...... 75/27 508,328 4/1971 Germany ...... 148/24 Related U.S. Application Data 63 Continuation-in-part of Ser. No. 74,092, Sept. 21, Primary Examiner-Winston A. Douglas 1970, abandoned. Assistant Examiner-Mark Bell 52) U.S. Cl...... 148/24; 49/37; 148126; 57 ABSTRACT 295; 228/56 A pyro-welding procedure is disclosed herein in which (5) Int, Cl...... 2: 39 a solid shaped weld element, including a compatible (58) Field of Search...... ! ki's . $o 5. heat generating source, a ferrous weld material 194; 29/498.5, y source, characteristic control materials and alloy ing agents, is disposed between the opposing surfaces (56) References Cited of ferrous structures intended to be joined. Means are UNITED STATES PATENTS provided for igniting the weld element to effect weld 2,282,175 5/1942 Emerson...... 75/27 ing of the ferrous structures. Preheating means may be 2,482,093 9/1949 Carlson...... 75/27 included that may take the form of ignitable strips dis 2,490,327 12/1949 Soffel...... 75127 posed adjacent the weld element adapted to thermally 8. 33 Sk ------1837 prepare the opposing surfaces of the ferrous structure 3,089,798 5/1963 Rejdak.....ayer...... 149/37 for receiving theth meltelted ferous weld materialial. 3,104,996 9/1963 Boddey...... 148/24 9 Claims, 5 Drawing Figures

PATENTED JUN 7 1975 * 3S Ol S8

INVENTOR. aézz246%/47/4 - LBY 60 (2224 3,890,168 1 2 EXOTHERMC WELDING COMPOSITION Therefore, it is among the primary objects of the The present invention is a continuation-in-part of co present invention to provide a novel welding device, pending application Ser. No. 074,092, filed Sept. 21, composition, and apparatus utilizing an exothermic re 1970, and now abandoned. action to produce the molten ferrous weld in situ at the proper temperature and under properly con BACKGROUND OF THE INVENTION trolled conditions. l, Field of the Invention Another object of the present invention is to provide This invention relates to apparatus, composition, and a novel exothermic reaction welding process, composi process for pyro-welding ferrous parts together utiliz tion, and apparatus wherein opposing surfaces of fer ing an integral, shaped, solid weld element as the O rous parts may be readily joined in an integral joint by source of heat and ferrous weld material. The heat is remotely igniting a solid heat generating material with generated by an exothermic reaction. out the aid of a welding operator. 2. Brief Description of the Prior Art Yet another object of the present invention is to pro Welding is a method for joining of parts so as to vide a novel welding process whereby pyrotechnics form an integral structure or construction. It is metal 5 may be employed to ignite and form the weld material lurigical or physical process wherein a weld material is into an integral connection with opposing surfaces of melted in situ between the opposing surfaces of the the steel part without the aid of a welding operator. steel parts to be joined. With an external heat source, Still another object of the present invention is to re such as a torch or the like, the edges of the steel parts duce the cost of welding structures incorporating fer or to be joined are heated to a temperature suffi rous parts by eliminating the weld operator and cient to accomplish the intermetallic fusion or bonding wherein the weld joint is formed by employing ignitable of the melted weld material thereto. pyrotechnics. In the past, difficulties have been encountered when A further object of the present invention resides in practicing conventional welding techniques which are providing a preheating means for conditioning the wall due to the degree of cleanliness required, the shape of 25 portions of ferrous parts intended to be joined so that the joined edges, the skill of the operator, and the heat the surfaces may readily receive and bond with molten ing facilities. Some prior art devices employ exother weld material subsequently supplied to the preheated mic reactions to produce a weld between ferrous parts. 32S. Such prior art devices are disclosed in U.S. Pat. Nos. 30 BRIEF DESCRIPTION OF THE DRAWINGS 2,870,498; 2,932,886; and 3,461,543. However, these The features of the present invention which are be prior art processes and devices have not been found en lieved to be novel are set forth with particularity in the tirely desirable since difficulties are experienced in ob appended claims. The present invention, both as to its taining uniform heating at a suitable temperature and organization and manner of operation, together with in the degree of skill required to join the metals by ef 35 further objects and advantages thereof, may best be un fecting simultaneous heating of the base metal work derstood by reference to the following description, piece parts and the melting of the weld material. These taken in connection with the accompanying drawings, prior art processes and devices require the presence of in which: a skilled operator, and it is extremely difficult to be as FIG. 1 is a perspective view showing a pair of ferrous sured of a proper weld without employing destructive 40 plates being joined together by means of a weld joint testing techniques. utilizing exothermic reaction; Therefore, a need has long existed to provide a sim F.G. 2 is a view similar to the view of FIG. 1 illustrat ple and relatively economical welding process, compo ing a preheating means separating a solid weld element sition, and apparatus so that great labor saving can be from the opposing wall surfaces of the parts to be produced and so that the labor of lesser skilled men 45 joined; than conventionally employed may be used. FIG. 3 is another perspective view of the present in SUMMARY OF THE INVENTION vention showing the preheat material terminated at its opposite ends in dams or end pieces; Accordingly, the difficulties and problems encoun FIG. 4 is another perspective view, in cross-section, tered with the prior art welding articles and systems are 50 of the welding apparatus shown in FIG. 3; and obviated by the present invention which provides a FIG. 5 is a perspective view of a typical installation novel apparatus, process, and composition for produc of the solid weld element carried in a gap having a ing a weldable joint between ferrous parts that includes downwardly opening entrance for vertical welding pro supporting the opposing wall surfaces of the parts to be cedures. joined so as to define a gap therebetween. A solid weld 55 element is nested in the gap. The weld element further DESCRIPTION OF THE PREFERRED includes a suitable ignitable or pyro composition EMBODIMENT adapted to substantially instantaneously ignite to pro Referring to FIG. 1, a pair of ferrous plates intended duce molten ferrous weld material and to heat the op to be joined together are indicated by the numerals 10 posing wall surfaces so as to receive and fuse with the and 11 and are disposed at right angles with respect to molten weld material. each other so as to define a weld gap or cavity between One form of the invention may include preheat the terminating end of plate 11 and the wall face of part means which may be a strip of ignitable material sepa 10. Located within the cavity or gap there is disposed rating the weld element from the wall surfaces. The a plurality of solid weld element means which, in the strip burns ahead of the weld element so that the sur 65 present instance, take the form of rods having a center faces are adequately prepared to receive the molten core of flux material. A typical rod is indicated by nu ferrous weld material. meral 12 and its solid composition is composed of suit 3,890, 168 3 4 able exothermic reactants, slag control materials, fer comprises not only the weld material formed by the rod rous weld material sources, and alloying agents, while or rods but includes the material of strip 23. the flux material is indicated by numeral 13 and may be It is to be understood that although the solid rods il any suitable cleansing agent. lustrated at 12 or 21 comprise heat generating means For the purpose of practicing the invention, it is pre 5 in which each rod may include a solid central core ferred that an elongated flange 14 be carried on the which is of a different composition from the surround surface of the face of part 10 so as to be able to support ing material, the preferred embodiment is one in which and hold the terminating end of steel part 11. The the composition of the solid shaped weld element is flange 14 may be composed of a ceramic material or uniform throughout. may be integrally formed with part 10 so as to be avail () Referring now to FIG. 3, it can be seen that the igni able for use. When so formed, flange 14 is integral with tion may take place by means of electricity employing 10 adjacent the weld site so as to function as a support. resistant heating techniques. A power supply 24 is elec If convenient, the flange 14 may be welded to the sur trically connected to a pair of identified by face 10 for temporarily supporting the end of part 11 numerals 25 and 26 which are carried on the ends of 5 the weld cavity, such as by with the ends of until the permanent weld has been made. strip 23. However, it is to be understood that the end Preferably, the opposing end surface of steel part 11 pieces 25 and 26 may take the form of end stops or facing the opposing surface of part 10 to which it is to dams for the weld cavity without employment as elec be attached, is angled at an approximate 45 so that the trodes. In this instance, the torch 16 may be employed weld gap or cavity is substantially V-shaped in cross 20 for providing the preheat as well as heat for the weld section. The angled end surface of steel part 11 is indi material. By employing resistance heating techniques, cated by numeral 15 and runs across the length of the the rod 21 will ignite across its entire length at substan part 11. The weld cavity is filled with the plurality of tially the same time so as to immediately form the weld. rods 12 and each rod may be of such a composition that The strip 23 will ignite before the ignition of rod 21. A the weld material may be composed of the same mate 25 feature resides in the embodiment of FIG. 3 in that the rial as the base parts to be joined or the weld material end pieces or dams 25 and 26 will close off the weld may be of a different material altogether. When the cavity at its opposite ends so as to more precisely con weld cavity has been nested with the plurality of rods, fine the molten weld material as it is ignited. the peripheries of the rods will come into contact with Referring to FIG. 4, the invention as shown in FIG. the opposing wall surfaces to be joined. 30 3 is substantially illustrated in cross-section wherein it Ignition of the exothermic reaction in the rods may can be seen that the rod 21 substantially occupies the be readily achieved by means of a high temperature weld cavity defined by the strip of preheat material 23 torch 16 which expels a jet flame 17 into the weld cav and that the electrical connections for the power sup ity occupied by the plurality of rods 12. A temperature ply to the weld cavity are by means of the preheat strip of 4000-6000 Fahrenheit ignites the rods to form the 35 23. In this latter instance, it is preferred that the end molten weld material and in turn to form a permenent stops be composed of an insulating material, such as ce weld as indicated by numeral 20. During the melting ramic composition, while the electrical connection of procedure, the cleansing agent or flux will melt and the power supply will be to the side pieces of the elec spread to cleanse the opposing wall surfaces of the trically conductive preheat strip 23. When energized, parts intended to be joined. At this elevated tempera the resistance heat will be generated from one end of ture, it is believed that the weld may proceed at a con the preheat strip to its opposite end to instantaneously venient rate of two inches per second. and simultaneously cause heating and melting of the Referring now to FIG. 2, another embodiment of the preheat material followed by ignition of the weld ele present invention is shown wherein the weld element ment, rod 21. comprises a rod 21 which is of sufficient diameter to 45 It will be understood that, although preheat strip 23 occupy the distance between the opposing wall sur is illustrated in the drawing, the preferred embodiment faces to be joined. The single rod 21 is of the same does not utilize a preheat strip. This is illustrated, for composition as previously described and may encase a example, in FIG. 5. suitable flux or cleansing agent 22 as a core. Addition Referring now to FIG. 5 in detail, it can be seen that ally, the embodiment shown in FIG. 2 includes a strip 50 the welding process and apparatus of the present inven of preheat material indicated by numeral 23 which foll tion will operate in conjunction with overhead sections lows the general outline of the weld cavity by lying be wherein the opening to the weld cavity faces in a down tween the rod 2 and the opposing surfaces intended to ward direction. In such instances, the rod 21 may be be joined. Also, a portion of the strip material 23 lies forced into the cavity so that its peripheral surfaces will against the portion of flange 14 which defines the V 55 be in interfering relationship with the upwardly taper shaped cavity. The preheat strip is intended to burn ap ing walls of the cavity. Since the wall surface of plate proximately one inch ahead of the weld metal and is 11 is angularly disposed with respect to the surface of composed of material adapted to burn at the elevated plate 10, the entrance to the cavity is substantially large temperature of between 2000-3000 Fahrenheit. The compared to the bottom of the cavity so that rod may composition of the preheat strip may include any suit be placed in an interference type fit so that it will be able pyrotechnic composition which may be readily ig temporarily retained in the cavity during the ignition nited and caused to burn within this temperature range. and melting period. Also, if it is desired to retain the By burning the material of the strip 23, the opposing rod in place without the use of an interference fit, it is wall surfaces of the steel parts are properly heated so 65 conceivable to use a suitable adhesive or bonding agent as to receive the melted weld material of the rods 12 or for temporarily restraining the rod in the cavity. 21 when the pyrotechnic composition of the rod or The weld element 21 may be used within a cavity as rods are similarly ignited. A weld 20 is produced which previously described or may be used in connection with www.rsso-o-o-o-Hui-o-or-m-m-m-

3,890,168 5 6 butt joints where a cavity is not defined. In fact, the melting point of the ferrous metal contributes to the weld rod 21 as well as the plurality of rods may also be production of a weld which is free of glass or slag and used in connection with butt joints. When a cavity is is substantially void free. It has been found that the in defined either by the opposing surfaces of the metal clusion of calcium, silicon, and materials, parts to be joined, or the V-shaped cross-sectional strip as described more particularly hereinafter, results in 23, it is preferred to employ the back-up plate 14 so as the depression of the melting point of the slag to a value to keep the weld from dropping out from between the approximately equal to that of the ferrous weld metal. opposing wall surfaces. It is to be understood that such The density of the resultant slag or glass is such that it a back-up plate is conventional in the art, and it may floats out of the weld while the weld material is still be readily adhered to the metal part by an suitable O molten. The particular compound or alloy form in means, such as or adhesive bonding. which the slag melting point depressant materials are It is also to be understood that the pair of metal parts supplied is not particularly critical so long as they react being joined may be of any metal composition and that to form the slag control compounds at the reaction the present invention is not limited to steel parts. Also, temperatures provided by the exothermic reactants. In the composition of the weld element may include any 5 suitable controlling agents for determining the rate of general, calcium, silicon, and magnesium have been burn, composition of slag, and weld material in accor found to be effective slag melting point depressants. dance with the concept of the invention. Black ox One convenient form for the provision of calcium and ide, FeO, the aluminum will serve as an adequate heat silicon is to use the compound calcium silicide. This generating agent or material. The flux, if used, may be material absorbs a substantial amount of heat in react of any suitable composition and may take the composi ing to the corresponding calcium and silicon oxides. In tion of titanium oxide and lime, borox and flint glass. order to insure a hot enough environment to produce In actual operation, a permanent weld may be pro a good weld additional materials, such as potassium duced by initially placing a weld element into a pre perchlorate and potassium dichromate, are added to pared weld cavity between the opposing wall surfaces 25 the admixture. Pure metallic calcium is dangerous to of ferrous parts intended to be joined. Each of the weld handle, particularly in finely divided form because of elements contains an intimate admixture of exothermic its tendency to react with moisture in the air; so for material, slag control material, and alloying material. safety reasons, calcium may be provided in the form of The exothermic reaction causes the formation of mol a suitable calcium aluminum alloy which does not ex ten ferrous material as a product of the reaction. Once 30 hibit these dangerous properties. One such suitable cal the molten weld material has been formed, it will fuse cium alloy is that composed of an admixture of 80 per with the opposing wall surfaces of the ferrous parts. An cent by weight calcium and 20 percent by weight alu operator is not needed to precisely control the temper minum. ature or the flow of molten weld material since the con The glass or slag is often quite viscous at tempera trol of the weld material is substantially dictated by the 35 tures approximately the melting point of the ferrous preparation of the weld site and the positioning of the metal. In order to render the slag less viscous, calcium preformed weld element. Therefore, labor costs are fluoride may be added. Calcium fluoride does not enter greatly reduced and a considerable time saving is into the reaction at the temperatures involved in a ther achieved in the construction of ferrous products. This metic reaction. Calcium fluoride merely changes phase is especially evident in the building and construction 40 from the solid to the liquid and then back to the solid trades wherein the frames of high rise buildings are of phase again. The visible effect of including calcium flu steel construction with many welds at crucial locations. oride in the weld is that it produces a more homogene The problem of producing structurally sound ferrous ous slag free weld, which appears to have a polished welds quickly, cheaply, and with semiskilled or un surfce. In handling calcium fluoride in the finely di skilled labor had not previously been satisfactorily 45 vided state care must be taken to prevent this material solved. Various thermetic welding compositions, de from picking up water out of the atmosphere. The pres vices, and procedures have been proposed; generally, ence of water in the weld element tends to produce however, these procedures entail using a thermetic re voids in the weld and the extreme it will cause the weld action as the source of heat to replace the more con material to explode and splatter out of the weld cavity. ventional electrical arc or gas flame heat source. One 50 The physical form of the materials comprising the conventional procedure employs the thermetic reac weld element and the weld element itself has been tion to produce a molten pool of iron in a . The found to be of importance in producing a satisfactory molten pool of iron is then conducted from the crucible weld. The materials that go into the weld element to the welding site where the heat contained within the should be finely divided and thoroughly blended. In molten metal is sufficient to produce fusion with the 55 general, the materials should be reduced to such a size parent metal structure so as to form the weld. Using that they will all pass through a lo0 mesh Tyler screen. conventional thermetic admixture of iron oxide (Fe3O4 Preferably the aluminum is of such a size that it will which is a stable form of iron oxide, including both fer pass through a 200 mesh Tyler screen. When a calcium rous oxide and ferric oxide and which is black in color) aluminum alloy is employed, it has been found that the and aluminum turnings in a loose admixture produces coarser fractions may be of such a size that they will a weld that is splattered considerably and is an admix pass through a 32 mesh Tyler screen but will be re ture of aluminum oxide, glass or slag with iron and in tained on an 80 mesh Tyler screen. Preferably, how cluded voids. The weld has no significant structural ever, the major proportion of this calcium aluminum strentgh and is essentially valueless. alloy will pass through an 80 mesh Tyler screen. The According to the present invention, it has been deter 65 blending of the materials should be such that each por mined that the inclusion of materials that reduce the tion of the weld element has substantially the same melting point of the slag or glass to at or below the characteristics. 3,890, 168 7 8 The blended loose powder form of the composition der the weld unusable. The 5 percent stoichiometric occupies approximately 50 percent of its theoretical excess of iron oxide generally produces an unsatisfac volume. One hundred percent of its theoretical volume tory weld. is the volume occupied by the material alone without In order to produce the desired characteristics that any voids. The material should be compressed to a are compatible with the material being welded, it is value of from about 60 to 80 percent of its theoretical necessary to include various alloying materials in the volume and preferably from about 60 to 70 percent of weld element. These materials have as their main pur its theoretical volume. Compressing the admixture to pose production of welds having the desired physical more than about 80 percent of its theoretical volume characteristics, but they also necessarily enter into the sedates the exothermic reaction to the point where a O stoichiometry of the exothermic reaction. The chro satisfactory weld cannot be achieved. Compaacting the mium contained in potassium dichromate produces an loose powder form of the composition into a solid alloying effect. The potassium dichromate itself also shaped article accomplishes at least three things. The increases the heat to the reaction. Magnesium serves as shaped article is easier to handle than the loose pow a reducing agent just like the aluminum, except that the der. The heat generated by the weld element is concen 15 net effect of replacing aluminum with magensium re trated since the same heat is generated within a smaller sults in reducing the temperature of the reaction for a space. The compaction expels air and the moisture given unit volume of weld element. The inclusion of al contained in that air from the interior of the weld ele loying materials in the form of metallic oxides, such as ment. The presence of air within the weld element pro nickel oxide and molybdenum oxide, provides materi notes the formation of voids in the weld and causes als that react like the iron oxide except as with the mag splattering of the weld material during the formation of nesium the temperature of the reaction for a given unit the weld. volume of the weld element is reduced. The calcium Preferably the composition in its powdered form ei and silicon materials absorb heat and to that extent ther during the blending operation or just prior to the tend to cool the reaction. Materials that pass through compression step is subjected to heating, vacuum, ni 25 the reaction substantially unaltered, such as calcium trogen purge, or some combination of these treatments fluoride or , merely absorb heat and to that ex so as to expel moisture and air from the powder compo tent tend to cool the reaction. The following formula sition. It is particularly important that moisture be re tions have been found to be effective in producing sat moved because the steam generated by the presence of isfactory pyro-welds. moisture during the welding operation seriously im 30 TABLE pairs the quality of the weld by forming voids and by splattering material out of the weld cavity. IV W The problem of the production of voids and splatter Wt. 2 Wt Wt. 9% W. Wt. 2 ing of material dictates that gas evolving reactants must FeO," 66.0 70 72.O. 700 57.2 be excluded insofar as possible from the composition of 35 Al 3.2 2.5 0.5 12.0 11.4 Mg 5 4.5 2.0 1.9 the weld element. For this reason, exothermic reactants CaSi O.2 4.5 3.0 3.8 that include nitrogen or hydrogen producing materials Ca/A* * 16.5 8.5 10.0 9.5 CaF 2.5 3.7 cannot be used. Potassium perchlorate and potassium KCrO, 4.6 7.6 dichromate generate some gas during the reaction, as NiO, 2.0 KCO, 25 indicated by the presence of smoke evolving from the Min-k 0.5 .8 weld site when these materials are present in the weld Crick .8 element. It has been determined, however, that the vol MoO 0.8 atilization of the potassium takes place under such con C++ k is 0.5 ditions that it does not tend to form voids or cause "Stable, black mixture of iron oxides derived from millscale 45 "Calcium-aluminum alloy, 80% Ca, 20% Alby weight splattering of the weld material. For this reason, small **"High carbon ferromanganese amounts of these materials may be tolerated in the weld ****High carbon ferrochrome element. The weld element should be stored and han ***** powder dled in a dry environment so as to prevent it from pick ing up water out of the atmosphere. The composition of formula V produces a hard It has been found that the composition must be very 50 facing alloy deposit. The material of formula IV pro carefully balanced to substantially stoichiometric val duces a weld material that has the characteristics simi ues if a satisfactory weld is to be achieved. It is partly lar to 1015 or 1010 . The weld produced for this reason that composite welding elements utilizing a weld element having the composition of for wherein the composition of various segments of the mula II contains a small amount of slag included in the welding element differ from one another have proven 55 weld. This weld is not as satisfactory as those of other to be very difficult to use. If the stoichiometry of the re compositions. action is such that an excess of reducing agent is pres A weld produced utilizing a weld element composed ent, the excess reducing agent will show up as an alloy of the formulation I was analyzed and was found to ing material in the weld. Where the reducing agent is have the following composition by weight: carbon - aluminum, this results in a very brittle weld that can be 0.04, chromium - 1.24%, nickel - 0.67, silicon - 1.93, shattered by a hammer blow. Where there is an excess phosphorous - 0.024, sulfur - 0.028, aluminum - 0.50, of metallic oxide, the energy required to heat the ex and the balance iron. This weld was slag free and was cess cools the reaction to such an extent that it is diffi very hard and dense. The slag was deposited on the top cult to achieve a satisfactory weld. A 2 percent stoi 65 of the weld and was easily chipped off. This weld was chiometric excess of aluminum will produce a very brit tested structurally and was found to have an ultimate tle weld. A 2 percent stoichiometric excess of iron strength of l 17,890 pounds per inch and a yeild oxide will cool the reaction somewhat but will not ren of 89,430 pounds per square inch. The weld exhibited

3,890, 168 9 10 7 percent elongation and 8.9 percent area reduction. formulation. Quantities in excess of this amount tend to The carbon content of the weld apparently occurs as an produce a slag that is so high in aluminum oxide that impurity from the iron oxide. The iron oxide is derived its melting point is greatly in excess of that of the fer from mill scale which contains a proportion of carbon. rous metal. This tends to produce slag inclusions in the The phosphorous and sulfur apparently also came from weld. The materials, such as magnesium, calcium, and the same source. It does not appear that these elements silicon that are added to depress the melting point of migrated into the weld from the two parent structural the slag are generally approximately equal in weight steel plates that were joined together by the weld. percent to the elemental aluminum. In general, the In general, the reactants in these formulations appear combined weight percentage of the slag melting point in the final weld product as follows: the aluminum, () depressants does not vary from the weight percentage magnesium, calcium, and silicon appear as the corre of the elemental aluminum by more than about 5 per sponding oxides in the slag which is glass like in its cent and preferably by no more than about 3 percent. characteristics; the calcium fluoride appears in the slag, Magnesium, calcium, and silicon have been found to be the iron, chromium, nicket, manganese, molybdenum, effective slag melting point depresants. The silicon is and carbon appear in the weld metal alloyed together, very effective but because it reacts slowly it tends to ap the potassium is volatilized and disappears from the pear as an alloying agent in the weld where it reduces soild phase at the site of the weld, and some aluminum the ductility of the metal. For applications where it is and silicon appear in the weld metal as alloying ingredi desired to have a ductile weld material, it is necessary citS. to reduce the quantity of silicon and to compensate by The above formulations may he varied over wide increasing the quantity of calcium and magnesium. In ranges provided that the stoichiometry is carefully ob general, the slag melting point depressants range from served so that the reducing agents are carefully bal about 5 to 20 weight percent of the total formulation anced against the other reactants, and the reactants and preferably from about 9 to 15 weight percent of the providing the exothermic reaction are present in quan total composition. The melting point depressants are all tities sufficient to produce the heat required to provide materials, the oxides of which form glasses. In general, a good weld. The alloying materials may be varied as calcium, when used as one of the glass-forming slag desired to produce in the completed weld whatever melting point depressants, is present in amounts rang predetermined characteristics are needed. In general, ing from about 2 to 15 weight percent and preferably the attempt is usually made to produce a weld having from about 5 to 10 weight percent. When present as a approximately the same characteristics as the parent 30 glass forming slag melting point depressant, silicon is metal to which the weld is applied. The formulation generally provided in quantities not exceeding about 5 in the above table is, for example, very much like armor weight percent. When present as a glass-forming slag plate in its characteristics and is particularly useful in melting point depressant, magnesium is generally not welding armor plate structures. Suitable reactants for provided in amounts exceeding about 10 weight per alloying purposes include the oxides; for example, 35 cent and preferably not more than about 5 weight per nickel, chromium, manganese, molybdenum, tungsten, cent. Like the alloying materials, calcium fluoride is cobalt, vanadium, and the like. These materials are in provided in a predetermined effective amount to cluded in the proportions necessary to provide the de achieve whatever degree of fluidity is desired in the sired amount of alloying agent in the final weld. These molten slag. Other slag fluidizers may be employed if materials may also be provided in the metallic form ei 40 desired. In addition to depressing the melting point of ther alone or alloyed with one another as desired. the slag, the calcium, magnesium, and silicon also ap These materials must be accounted for in the stoichi parently decrease the density of the slag so that it rises ometry of the formulation in order to avoid a formula more rapidly through the molten metal in the weld. tion in which there is an excess or a deficiency of re When it is desired to use oxidizing agents, such as po ducing agent. Carbon may be provided in the elemental 45 tassium dichromate and potassium perchlorate, to in form as, for example, graphite, or it may be included in crease the heat generated by the exothermic reaction, some other alloy, such as high carbon ferromanganese. these materials are provided in effective amounts as Carbon also occurs as an impurity in the commercially may be required to achieve the desired temperature. In available iron oxide. The mixture of iron oxides that is general the combined weight of such oxidizing agents preferred for use in this invention is that having the ap 50 should not exceed about 10 percent by weight of the proximately formula FeaQ. The exothermic reaction is total formulation. provided primarily by the iron oxide and elemental alu The materials included in the formulation have sev minum. The exact proportions of iron oxide to alumi eral characteristics in common. They are all powdered num must be adjusted in view of the other ingredients materials capable of being compacted in admixture in the formulation so as to achieve a stoichiometric bal with one another into a structurally coherent integral ance; however, reducing the elemental aluminum con shaped article for use as a weld element. These finely centration below about 9 weight percent generally pro divided materials do not, with the sole exception of the duces a reaction that is not hot enough to achieve a sat oxidizing agents, give off volatile materials at the reac isfactory weld. Likewise, reducing the iron oxide below tion temperatures encountered in these formulations. about 50 weight percent produces a reaction that is not Organic materials are not included in these formula hot enough to accomplish the desired weld. In general, tions because they tend to evolve gases at the reaction the iron oxide and aluminum combined should account temperatures here involved. In general the reaction for not less than about 65 weight percent of the total temperatures of these formulations are from about formulation. In general, the combined elemental alumi 65 4000 to 6000 Fahrenheit. num and iron should not exceed about 85 weight per The rate at which the weld element burns is increased cent of the total formulation. The elemental aluminum by compression over the rate at which the loose powder should not exceed about 15 weight percent of the total burns. The rate at which a weld element burns in 3,890,168 11 12 creases with increasing mass, apparently because of a composition. greater concentration of heat at the flame propagation 5. An exothermic welding composition of claim 1 face. In general, the formulas set forth in the above wherein the powdered glass-forming slag melting point table burn at rates of from about 1 to 3 inches per sec depressant includes calcium. ond. 5 6. An exothermic welding composition of claim 1 What is claimed is: wherein the powdered glass-forming slag melting point 1. A stoichiometrically balanced; homogeneously ad depressant includes silicon. mixed exothermic welding composition comprising the 7. An exothermic welding composition of claim 1 ingredients: from about 65 to 85 weight percent of an wherein the powdered glass-forming slag melting point admixture of powdered elemental aluminum and pow O depressant includes magnesium. dered iron oxide with from about 9 to 15 weight per 8. An exothermic welding composition of claim 1 cent of said composition being said powdered elemen wherein the powdered glass-forming slag melting point tal aluminum, from about 5 to 20 weight percent of depressant includes calcium silicide. powdered glass-forming slag melting poing depressants 9. A stoichiometrically balanced, homogeneously ad selected from the group consisting of calcium, silicon 5 mixed exothermic welding composition comprising the and magnesium materials which during welding yield ingredients from about 65 to 85 weight percent of an calcium, silicon and/ or magnesium, and an amount of admixture of powdered elemental aluminum and pow selected powdered alloying agents effective to form a dered iron oxide, from about 9 to 15 weight percent of predetermined alloy, said composition being com said composition being powdered elemental aluminum, pressed to between about 60 and 80 percent of its theo an amount of powdered glass-forming slag melting retical volume whereby the quantity of entrained air in point depressant selected from the group consisting of said composition is mimized. calcium, silicon and magnesium materials which during 2. An exothermic welding composition of claim 1 welding yield calcium, silicon and/ or magensium suffi wherein the ingredients are selected from those inor cient to depress the melting point of the slag produced ganic reagents that do not evolve any substantial 25 during the reaction of said exothermic welding compo amounts of gases at the reaction temperature of said sition to approximately the melting point of a metallic exothermic welding composition. weld material produced by said reaction, the combined 3. An exothermic welding composition of claim 1 in weight percentage of said powdered glass-forming slag cluding an amount of powdered calcium fluoride effec melting point depressant varying from the weight per tive to reduce to a predetermined value the viscosity of 30 a slag formed by the burning of said exothermic weld cent of said powdered elemental aluminum by no more ing composition. than about 5 weight percent, and an amount of pow 4. An exothermic welding composition of claim 1 in dered alloying agent effective to provide a predeter cluding an amount of powdered oxidizing reagent ef mined weld alloy, said composition being compressed fective to increase to a predetermined value the heat 35 into an integral, structurally coherent weld element, generated by the burning of said exothermic welding k k : k

40

45

SO

55

65