US2422965A - Aluminothermic unit - Google Patents

Description

June24, 1947. H. E. HlRscHLAND ETAL u 2,422,965

ALUMINOTHERMIC UNIT I Filed March 17, 1944 2 Sheets-Sheet l Syvum/vtm', Heesen?- E. H/Rs cfa/wvo, Saz/L man. /fvl u Jne 24, 1947- H. E. HlRscHLAND ET'AL 2422,965

ALUMINOTERMIC UNIT Filed March 17, 1944 -2 sheets-sheet 2 Patented June 24, 1947 2,422,965 ALUMINOTHERMTC UNIT Herbert E. Hirschland, Cranford, and Saul Ricklin, Rahway, N. J., assignors to Metal & Thermit Corporation, New York, N. Y., a corporation of New Jersey Application March 17, 1944, Serial No. 526,970

7 Claims.

This invention relates to aluminothermic units; and it comprises a self-contained unit or crucible, containing an aluminothermic powder and being useful for cutting metals, lmaking small welds, etc.; said unit comprising a casing, usually constructed of heat resisting material, serving to form a compartment for holding an aluminothermic powder, means for igniting said powder, a pouring plate at the bottom of said-compartment constructed of heat-resistant material and provided with a tapping hole having a diameter ranging from about e to inch, a metal tapping plate above said pouring plate adapted to cause automatic tapping of the unit, and means for holding the unit a spaced distance above the metal to be worked upon; all as more fully hereinafter set forth and as claimed.

Aluminothermic welding methods, making use of large size crucibles, have been known for many years and the technique involved in the use of such units has reached a high stage of development. It has been found however that there is also a considerable demand for self-contained aluminothermic units capable of being used in cutting operations, making small welds and for other purposes requiring an intense source of heat and/or small quantity of superheated molten iron or steel. We have found that small units of this type diiier from larger units in several important construction details.

We have found, for example, that units holding up to about 1 pound of aluminothermic powder can be constructed principally of cardboard, wood or other combustible material, rather than ci a refractory material. The apparent reason for this is that the aluminothermic reaction is completed in such a short time that the walls do not have suiiicient time to burn through before the aluminothermic metal has completely discharged. For units holding large quantities of aluminothermic powder, for example over 1 pound, it is best to employ a pre-cast inner lining of ceramic material. But for some purposes satisfactory results can be obtained by using a come bustible material, such as cardboard, which has been reproofed, for example by the application of a thin coating of ceramic material. It is also advantageous, of course, to reproof the containers used in the smaller units, either by the same or an equivalent method.

W e have also found that it is important to have the aluminothermic powder enclosed in a compartment having a pouring plate at the bottom which is constructed of heat-resistant and preferably heat-conducting material, such as compressed carbon or graphite. This plate must be provided with a tapping hole having a critical diameter within the range of about to Tse inch, if it is desired to produce a maximum cutting effect.

In addition we have found it important to provide an automatic tapping plate above the pouring plate. This tapping plate can be made from 30 gauge steel, for example, and has the function of retaining the aluminothermic powder in the container and of temporarily restraining the flow of aluminogenetic metal until the slag and metal have separated and a sufficient quantity of metal has collected to burn through the plate. We have further found that, in order to produce a maximum cutting effect, the unit must be provided with means for supporting it at a distance ranging from about 1/2 to 2 inches above the metal to be cut, thus furnishing a space for the metal to be washed away. In order to make such a unit fully self-contained, it is desirable to provide a small package of ignition powder in contact with the aluminothermic powder and a fuse by means of which this powder can be ignited. Two embodiments of this type of unit have been developed and tested, which appear to have important utility in a number of different operations.

Our invention can be described with somewhat greater accuracy by reference to the accompanying drawing which shows, more or less diagrammatically, two modifications of our aluminothermic unit. In this showing,

Fig. 1 is a vertical section through a small size unit provided with integral stand and a single ignition fuse,

Fig. 2 is a plan view of the small unit,

Fig. 3 is a vertical section through a larger unit provided with a sliding stand and two ignition fuses,

Fig. 4 is a horizontal section through the larger unit taken along the line fi-4 of Fig. 3, while Fig. 5 is a perspective view of the larger unit set up ready to be ignited, and on a reduced scale.

In the various figures, like elements are represented by like reference numerals. The unit is constructed with an outer water-proof casing I which isjsealed at the top and bottom to render it impervious to moisture. The larger unit is provided with a separate stand 2 (Figs. 3 to 5) which slides on the outer surface of the casing, while in the smaller unit the lower part of the casing 2a forms an integral stand, as shown in Fig. l. Both forms are provided with liners 3, which, in the smaller unit, is constructed of cardboard. This cardboard liner is advantageously iireproofed. A satisfactory reproong can be obtained by dipping the cardboard liner in a thin ceramic slip, formed from a refractory clay, magnesite or Alundum, mixed with sodium silicate, if desired. The resulting ceramic coating reduces the development of steam and lowers the violence of the reaction. The liner of the larger unit is preferably formed by a. pre-cast Crucible of ceramic material, such as Alundum, magnesite or other refractory material. The liners form a central compartment 8 which is filled with an aluminothermic powder which, when ignited, produces a mass of molten,.superheated iron or steel. This compartment is closed at the bottom with a heat-resistant or refractory pouring plate 4, having a central tapping or pouring hole 24 and being surmounted by a tapping plate v oi thin steel, usually about 30 gauge in thickness.

At the top the aluminothermic compartment is closed by a fuse plate 6, which may be of cardboard or ceramic material. Fuses I I pass through openings in the fuse plate which are made water tight by means of bushings or gaskets I2. To the inner ends of the fuses there Vare attached bags I3, usually of Cellophane, these bags being i'llled with a conventional ignition powder I4 adapted to start the rzlhermit reaction. The fuse plates .are also provided Awith filling openings i5 which are sealed with water-proof tapes I6 alter the aluminothermic compartment is lled.

Above the fuse plate there is a fuse compart ment l formed by an .extension 9 of the liner I and closed at the top by a metal cover IE! which has acentral opening I8 through which the fuses can be reached, after removal of the friction cap El. Thecover I0 is usually spaced from the top oi the fuse plate by cardboard spacers I9.

The bottom sections of the two Lmits are constructed differently, although in both a thin metal sealing plate 2U is provided. In the smaller unit the cardboard casing .extends below the laluminon thermic compartment and the pouring plate to iorm what might be called a pouring compartment or false bottom 2|. This should' have a height of roughly 1/2 -to one inch. The bottom alate Z' is spaced from the pouring plate il by means of a cardboard spacer 22.

vThe bottom of the larger unit is closed oi by the bottom sealing yplate 2B, which is advantageously provided with a 4central depression 23. A cardboard spacer 22a separates the bottom plate from the pouring plate 13 and, if this spacer has a depth oi about of van inch or more, the depression in the bottom plate is not required. The stand 2 of the larger unit is a separate casing formed of a strip of cardboard, the ends of which may be joined by staples, as at 2d; see Fig. 4. This stand has a height which is a fraction of the height of the unit as a whole and has a sliding t on the cardboard casing. Normally the stand is left in its upper position, as shown in Fig. 3, where it occupies but little space. But when the unit is readied for use, it is slid down into its operating position, shown in Fig. 5.

It will be noted that the corners of the stand are slotted in inverted V-shape to provide push-in support tabs 25. When the stand is slid down to the point where the tops of the tabs are below the bottom of the unit, the tabs can be pushed in,

shown in Fig. 5, to form a support for the bottom Aor the unit to rest upon. In this position the stand supports the body of the unit about 1 inch from the base upon which the unit is placed. The stand is also equipped with cut-outs 28 on each side to provide for the unobstructed washing away of the metal. The metal cap I'I of the unit can be removed Vby a knife or screw driver and -ie ends .of the fuses il can then be brought out through the opening I 3, as shown in Fig. 5. The unit is now readyvfor operation. The smaller unit is readied for use in a similar manner eX- cept that it is not necessary to move a stand into position, since thestand is integral with the body of this unit.

When the unit is ready-to be used and placed in position on the metal which is to be worked upon, it is only necessary to ignite one of the fuses. The fuse ignites the ignition powder which in turn starts the aluminothermic reaction. This reaction results in the formation of a mass of superheated molten steel in the bottom of the crucible, this requiring a period of from about 10 to 15 seconds, after ignition of the powder, for larger units holding 2 to 21/2 pounds of aluminothermic powder and 5 to 6 seconds in the case of smaller units holding 250 to 300 grams of powder. The aluminothermic steel melts through the tapping plate and passes through the counter-sunk tappinghole in the pouring plate. It will be noted that this steel in both modifications drops a short ydistance before striking the bottom sealing plate. lt burns ythrough this plate immediately andthe unit then delivers a small stream of superheated molten steel for a period of several seconds. The stream of molten metal delivered from the larger unit described above is capable of cutting through from 3A; to 1 inch of solid steel, while ine smaller unit will cut through a steel plate having a thickness of about 1A inch or more. This steel is, of course, capable of producing small welds and of furnishing heat for various other operations, as well as being useful for cutting metal.

We have found it' important to provide a distance or" at least about 1A; inch between the tapping hole and the bottom sealing plate in order to avoid plugging of the tapping hole. If the molten steel drops through this distance before striking the sealing plate it always cuts directly through this plate without stoppage.

As mentioned previously we have found that `the size of the tapping hole in the pouring plate is critical for the production of a maximum cutting eiect. This is seen from the fact that, if this hole is made 1A; inch in diameter, the larger unit described above will cut through steel having a thickness of up to 1 inch whereas, in contrast, if made 1/2 inch, the molten stream will cut through no more than about 1/2 inch of steel. If the hole is made smaller than 1% inch, the unit is likely t0 plug and the depth of penetration is also reduced. With the smaller unit the optimum size tapping hole is from about 1% to 1/4 inch, while the optimum size of the larger unit ranges up to about 151, inch. Other factors being equal, the smaller the tapping hole the greater the cutting effect produced. It is therefore desirable to provide the smallest tapping hole which is still suiciently large to ensure discharge of the molten metal and to avoid plugging.

We have further found that, in order to prevent plugging of the tapping holey it is important to have this hole counter-sunk. With a deeply counter-sunk tapping hole and/ or a thinner pouring plate it is possible to reduce the size of the orifice slightly without causing plugging. For example, in the case of the small unit, using a pouring plate with a thickness of 1A; inch, the minimum size of tapping hole which can be employed is about 1A; inch when counter-sunk to a depth of about 1/3 inch. But if the thickness of this plate is reduced to 1A; inch and if the tapping hole is counter-sunk throughout its depth, the orice can be made as small as fg inch. This tends to prevent cooling and consequent congelation of the metal as it passes through the tapping hole. Owing to the smaller volume of metal discharged from the smaller unit, this unit is Somewhat more likely to become plugged than the larger unit; hence the counter-sinking of the tapping hole is more important in the case of the smaller unit.

As stated previously the pouring plate -can be made from any heat-resistant and preferably a heat-conducting material, such as compressed carbon or graphite. If not made of a heat-conducting material, there is a tendency for the hole in this plate to enlarge too much during the pouring operation. This plate should have a thickness of about 1A; to 1A; inch. The tapping hole should have a height above the Work piece Within the range of about 1/2 to 2 inches to produce maximum cutting eect. This pouring height is provided by the false bottom in the small unit and by the legs of the stand 2 in the larger unit.

The materials of construction which are used in making our Thermit unit can be varied rather widely. As mentioned previously the Thermit reaction and the rate of discharge of the units are so rapid that the walls of the Thermit compartment can be constructed of materials which are only slightly resistant to fire. This is particularly true of the small unit. With the larger unit it is more important to have the wall of the Thermit compartment nre resistant, since otherwise this wall may burn through and spill the Thermit steel before the unit has completely discharged. If desired the inner lining of the Thermit compart- 1 ment may be constructed of the same material of which the pouring plate is made, that is, of compressed carbon or graphite. In this case the pouring plate may be made integral with the lining.

While we have described what we consider to be the best embodiments of our invention, it is evident, of course, that many variations can be made in the specific constructions described, without departing from the purview of this invention. Any of the conventional aluminothermic powders can be employed in our units but, of course, it is advantageous to employ those producing a maximum heating eiect since the greater the heat developed, the greater the result produced. The usual iron Thermit, composed of about 1 part of finely divided aluminum metal mixed with 3 parts of magnetic iron scale, is the cheapest and one of the most useful mixtures which can be employed. This mixture produces about one-half its weight of molten iron having a temperature roughly twice that of molten steel. This composition can be varied in many ways, such as by the addition of iron or steel punchings. For certain applications, it is possible to add up to -15 per cent of steel punchings for example. This provides a larger quantity of molten steel but it has the disadvantages that this steel has a lowerl temperature and that the unit has a slightly greater tendency to plug. Any of the usual ignition powders can be employed. For example, a mixture of barium nitrate, aluminum powder and black powder can be used. 1f necessary, the units can be made completely waterproof by dipping them as a whole in molten paraiin or by coating them with other waterproof coating compositions. For some purposes, such as welding, it is permissible to employ tapping holes which have diameters outside the range of from 1%; to 1%: inch. But, as stated previously, for maximum cutting eiiect this hole should be made the smallest size which is suiciently large to ensure the discharge of the aluminogenetically produced metal from the unit and should be hel-d above the Work a distance of from about 1/2 to 2 inches. Other modiiications of this invention which fall within the scope of the following claims will be immediately evident to those skilled in this art.

What we claim is:

l. An aluminothermic unit comprising an outer casing, la fuse plate serving to divide the interior of the casing into a compartment lled with an aluminothermic powder and an upper fuse compartment, a heat-resistant pouring plate at the bottom of said aluminothermic compartment and provided with la tapping hole, a bottom sealing plate'spaced from said pouring plate and serving as a lower seal, a top plate serving to close the top of said fuse compartiment and to seal the top of the uni-t, at least one fuse passing through said fuse plate, a package of ignition powder attached to the lower end of said fuse and in contact with said aluminothermic powder, and a removable cover in said top plate adapted to provide access to said fuse.

2. An aluminothermic unit comprising an outer casing forming an enclosed space, a fuse plate and a heat-resistant pouring plate provided with a pouring hole and serving to divide said enclosed space into an upper fuse compartment, a centnal aluminothermic compartment and a lower pouring compartment, a bottom plate sealing the pouring compartment and a top plate sealing the fuse compartment, lat least one fuse passing through said sealing plate, and, a mass of ignition powder in contact with the lower end of said fuse and with an aluminothermic powder filling said aluminothermic compartment.

3. The aluminothermic unit of claim 2 wherein said pouring plate has a thickness of from about 1/8 to 1/4 inch and is spaced from said bottom plate by at least 1A; inch.

4. The aluminothermic unit of claim 2 wherein said pouring compartment has a height of from about y.; to 2 inches.

5. The aluminothermic unit of claim 2 wherein said pouring hole is countersunk and has a diameter ranging from about to fe inch.

6. The aluminothermic unit of claim 2 wherein a metal tapping plate is provided above said pouring plate, said tapping plate being adapted to hold said aluminothermic powder in said aluminothermic compartment and to delay the ow of aluminogenetic metal until the separation of slag and metal has taken place.

7. The aluminothermic unit of claim 1 wherein said pouring plate is spaced from said bottom sealing plate a distance of at least about 1/8 inch.

HERBERT E. I-HRSCHLAND. SAUL RICKLIN.

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

UNITED STATES PATENTS Number Name Date '717,840 Goldschmidt Jan. 6, 1903 778,117 Culin Dec. 20, 1904 1,324,006 Buckham Dec. 2, 1919 1,883,755 Begtrup Oct. 18, 1932 1,838,357 Bottrill Dec. 29, 1931 1,430,959 Dutcher Oct. 3, 1922 1,068,267 Nditch July 22, 1913 1,299,869 Steinmetz Apr. 8, 1919

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