US733957A - Process of manufacturing homogeneous metal castings. - Google Patents

Description

UNITED STATES Patented July 21, 1903.

' PATENT OFFICE.

PROCESS OF MANUFACTURING HOMOGENEOUS METAL CASTINGS.

SPECIFICATION forming part Of Letters Patent N0. 733,957, dated July 21, 1903.

Application filed November 6, 1902. Serial No. 130,352. (No specimens.)

[0 Our invention relates to a process of manufacturing homogeneous metal castings by' bringing into the molten metal a mixture of a metal with an oxygen or sulfur containing metallic compound or with a halogenous compound or salt or the like, which mixture undergoes a react-ion when ignited. Such mixtures will be called thermit in the following specification. 1

It has already been proposed to put thermit or the metals obtained by the reaction of the thermit into molten metals by either putting the thermit on the surface of the liquid metal, or by putting the same on the bottom of the mold or casting boxes and by running the metal onto the same, or by throwing the thermit into the liquid metal as it flows out. This has been done for the purpose of obtaining metal alloys-1'. e., of bringing other metals into the molten metal-but at the same time 0 with the purpose of avoiding the formation of air-bubbles in the molten metal. In all cases it was not possible for the reaction, of the thermit to take place really at the bottom or at a place beneath the surface of the molten 3 5 metal, as even in case the thermit were put in the bottom of the mold it quickly rises up to the surface and reacts or burns only at the surface. The thermit is in this case rendered impure already more or less at the surface of the molten metal by slag and oxids, whereby the reaction is considerably disturbed, and in consequence thereof the results of the process as regards the manufacturing of a homo-. geneous metal or of a metal alloy are not always the same and are not always perfect. It s has been found that a greater scoritication of the metal separated in stain. nascend takes place; but besides this disadvantage the further disadvantage exists inasmuch as the heat 5o arising by the reaction is not transferred as well to the molten metal on account of the reaction taking place at the surface of the scorified metal.

In order to avoid these disadvantages, our new process consists in causing the reaction '55 of the thermit to take place within the molten metal, or even at the bottom of the same. hereby attain a much better utilization of the heat arising from the reaction, asthe hot slag must rise through the molten metal, and consequently will transfer part of its heat to the metal, while in case of the reaction taking place at the surface of the molten metal the heat of this slag is not nearly utilized on'account of the same being lost by radiation. I 5 the reaction'iakes place within the molten metal, all the impurities, gases, or the like can rise through the hotter and thinner lid" uid metal to the surface, wherebya more compact metal free from air-bubhles, flaws, 0 7 the like is obtained, which is very important for castings of iron, steel, nickel, bronze, and the like, for which the process is especially important; but it will be understood that the process may also be usedfor other metals. It is remarkable that the aluminogenetic metal (the metal separated by the reaction of the thermit) is nearly wholly. taken up by th molten metal, and it does not find any opp tunity of scorifying.

The process has the further great advantage that, owing to a high temperature being produced at the bottom of the liquid metal, a strong ebullition of the latter takes plac thereby naturally effecting an excellent rrs- 5 ing of slag and other-impurities. We attain hereby a perfectly new and peculiar pollng processz'. e., a process of ebullition of the mass-which process was hitherto carried into effect by dippinga piece of green wood there- 9 in. This poling process can, contrary to the process hitherto known,also be used when casting iron and steel, especially when making great quantities of castings of these metals; but it may also be used for other metals, bronze, and the like.

It will he understood that in using this process the raising of the temperature of the bath brings forward great advantages.

It is to be noted that it is already known IOU now to repair gudgeons of shafts which have been broken off by ignitingnpon the same a suitable quantity of thermit and then casting upon the same, molten iron or steel. In this case the'cast-iron or the steel is naturally cast upon the highly-heated metal and slags provided in a certain way at the bottom. The metal being separated by the re action of the thermit is naturally also in this process taken up into the casting; but in carrying this process into eifect the liquid metal must always be stirred up in order to loosen the congealed slag from the joining spot.

It will be clear that this process has nothing to do with the poling process and with the ebullition. of the molten metal taking place by means of the hot slag and metal parts rising in stata nascendi.

This process is carried into effect by forming the thermit mixture in any convenient manner into bricks or packing the same up in sheet-metal boxeslor the like. The bricks, sheet-metal boxes, or the like must by suitable means-for instance, by means of a strong iron rodbe pushed down to the bottom of the mold and must be kept for acertain while in this position until the reaction has proceeded sufficiently far or is entirely finished. The thermit is then gradually consumed by the burning of the same going on in the molten metal. By holding the thermit underneath the surface of the bath hardly any unburned parts of the same come to the surface, so that as desired the reaction goes on perfectly within the molten metal. The rising of u n burned parts of the thermitand the spreading of this unburned thermit upon the surface of the metal-bath which always took place when putting the thermitinto the mold and then running the metal onto the same, is entirely avoided by dipping the thermit into the bath and holding it underneath the surface of the same on account of the rising slags forming an envelop around the thermitpowder and holding the same down in the bath in such a waythat the envelop of slag forming around the same gradually and equally rises; but a certain quantity of slag always remains at the end of the rod,which quantity holds the unburned thermit-powder down. It is a very astonishing fact that it is possible to hold the loose powder within the bath by means of the rod, though the box surrounding the same is immediately melted as soon as the reaction begins; but it will be clear that the slag arising by the reactionglues the thermit-powder together, so that this powder remains in its position and does not rise, though the specific weight of the same is much lighter than the weight of the molten metal. On the other hand, a sufficient quantity of slag and metal always gradually gets loose and rises. The

- reaction consequently goes on equally toward the center of the bodyof thermit, and the reacting mass always remains in direct contact with the surrounding molten metal. On account of the reaction taking place in the manner described above it is possible to hold the thermit underneath the surface of the metal even in case the thermit. is not formed into bricks, but is only surrounded by a box. This box, which preferably consists of sheet metal, is only for the purpose of introducing the thermit into the bath. It will be clear that this Sheetunetal box is quickly melted and that the thermit is only retained by the envelop of slag mentioned above, which envelop adheres to the iron rod. By pulling the rod out of the bath before the reaction is finished' one can easily see how it is going on. This process could only he found out by means of experiments, and it will be clear that the same cannot be compared with throwing the thermit on the bottom of the mold or crucible or into the stream of the liquid metal running into the mold, as in all those methods of adding the thermit the latter immediately floats upon the surface, and the reaction conseqnently only takes place at the surface of the molten metal. The idea of preventing the thermit from floating on the surface of the metal and of holding the same underneath the same until the reaction goes on or is completed is entirely new.

It will be clear that by means of this process the metal can be alloyed with all the metals which are to be added. The capability of alloying these metals is in this process a very considerable one, as the metals to be alloyed are added to the molten metal in stata nascend-i. As the metals are added, furthermore, at the bottom or within the molten metal and as the same has a high temperature, a very equal dividing up of these metals takes place, which dividing up is still favorably supported by the ebullition, so that stirring up of the molten metal (which stirring up can especially in case of large quantities only be eifected with great difficulties) is not necessary. It will be clear that any suitable metal can in this way be added to the molten metal; so, for instance, titanium may be added to cast iron or steel. For this purpose a thermit is selected of which the oxygen-containing compound is partly replaced by titanic acid. Also other substances may be added in these cases to the thermit-such as, for instance, lime, magnesia, silicic acid,or compounds by means of whichthese substances are developed (in ring the reaction. By means of these additions a thinner liquid slag is obtained. The velocity with which the reaction of the thermit takes place may be reduced by suitable additions. By this means the effect of the reaction upon'the liquid metal takes place for a longer time.

By this process the formation of gas-bubbles is avoided, as the gases are bound by the metals or metalloids added (such as manganese, titanium, silicon, and the like) in sta tu nascendz', thereby transforming these metals into slag.

In order to make the matter more clear, several examples of carrying out the process are given.

v I. There is a casting-ladle or similar device ICC in which five thousand kilograms of molten cast-iron have been run from the cupolafurnace. containing twelve and one-half kilograms of ferro-titanium thermit (one-fourth per cent. of the quantity of cast-iron) to a bar and puts the same into the molten metal, where it is held until the reaction has taken place. The composition of the ferro-titanium thermit may be seen from the following formula:

The slag arising by the reaction is skimmed before pouring the metal into the mold in the usual manner. The titanium has either been taken up by the molten metal or has been absorbed by the gases, thereby taking up the impurities and being transferred into slag, so that there may be only very small quantities of the titanium in the metal-bath; but even in spite of only very small quantities being contained in the same the efiect of the process-i. e., homogeneous casting-is obtained;

II. In this example shall be shown in what manner considerable quantities of metal can be brought into the molten metal. One takes a casting-ladle containing three thousand kilograms of liquid steel, into which one thousand kilograms of nickel thermit are brought. As this cannot be easily effected at once, single boxes each containing about ten kilograms of nickel thermit are fixed to iron rods and are either simultaneously or one after the other introduced into the molten metal in which the reaction takes place in the mannerdescribcd above, whereby a great quantity of nickel is brought into the steelbath. The nickel thermit to be used consists of equivalent quantities according to the formula:

fills a crucible with, for instance, fifty kilograms of molten copper and brings into this copper a box. (preferably manufactured of i sheet-copper) containing two kilograms of manganese thermit mixed according to the following formula:

The manganese which is formed mixes withthe copper, so forming manganese copper.

In case the temperature of the molten metal is not high enough for igniting the thermit the ignition can be effected by adding a mixture of peroxid of barium and alu-- several per cent. of the mass to be reheated.

One fixes a thin sheet-metal box Especially in this case is it absolutely necessary to effect the heating from the bottom to the top. In case, however, only an ebullition of the liquid metal-for instance, of liquid cast-iron to which at the same time titanium shall be added in order to bind the nitrogenshall be efiected, one-eighth to onehalf per cent. of thermit will be sufficient. Still smaller quantities of thermit can be used in case only a small part of the liquid metal is to be heated at a certain part of the mold and is to be brought again to higher temperatures. This is advantageously used in two diiferent cases which occur very often in practice 2'. e., first, in casting pieces of steel of various section; second, in casting blocks of wroughtsteel. In the first case a box filled with thermit is placed into the side walls of themold at the desired place by pressing this box into the side walls in case the mold is manufactured of soft material or by arranging special holes inthe moldfor taking these boxes up, or the box is introduced into the molten metal by fixing the box to a rod and pushing the same into the mold at the desired place. This mode of using the thermit is especially advantageous in casting such steel castings which are of great extent or which have very thin walls. In such castings very often the disadvantage occurs that the molten steel flowing through the'mold gets pasty during the flowing by the coolingelfect of the mold, so that the steel moves on as a pasty mass through the mold and does sometimes not completely fill the same, or it happens that the steel is no more able to fill the rising funnel. Ifin such molds boxes with thermitare fixed in suitable places which are ignited by means of the steel flowing along the same, the heat arising by the reaction of the thermit will reheat the steel which is in the state of congealingand will cause the same to againbecome thin or liquid, thereby obtaining excellent castings. The reheating of the contents of the rising funnel by means of thermit is, for instance, especially advantageous on account of permitting of heating the steel in the rising funnel to a higher temperature than the steel in the mold. This can be attained with very small quantities of thermit. The consequence is that the steel in the funnel remains liquid much longer than the steel in the mold, so that by-this means the funnel can really serve as a storage-room for the liquid steel, by means of which storage-room the diminution of the volume of the congealing steel is immediately compensated. The metal does not consequently fall in in the middle of the rising funnel so far that a hole arises which sometimes even goes down into the mold.

In order to avoid these holes arising by the falling in of the metal during the congelation, boxes filled with thermit may be used, especially in the manufacture of blocks of wrought-steel. Attempts have been made hitherto to avoid these holes by holding the runner open as long as possible and always ICC &

casting into the same small quantities of hot steel. In spite of this process being'used defective parts or holes are sometimes found in castings. These holes can sometimes not be filled afterward by casting steel into the same on account of the runner congealing before the holes begin to form, so that no new liquid steel can be cast in. When using thermit, the head of the block can be kept fluid much longer and the steel can always follow, so that no holes can arise. If the thermit is put on the surface of the casting-head, no practical success can be obtained, as the developed heat cannot be conducted to the right place. This latter process is advantageously carried into effect in the following manner: The thermit formed into briquets or inclosed in sheet-metal boxes is fixed to a strong iron rod and is pushed by means of the same through the upper congealed crust of the block until about one meter underneath the surface, (according to the extent of the block.) The thermitis thenimmediatelyignited and burns quickly. A reaction then takes' place by means of which a certain quantity of heat is developed. The steel in the head of the block is thus rendered liquid or more thinly liquid and fills the holes which may arise. By this process a great open funnel is formed in the head, which funnel must always be cast outwith steel. This operation can be repeated and it can so be attained that the holes are entirely avoided.

In the specification thermit? is always mentioned, which consists of a mixture of aluminium with an oxygen-containing metal compound, especially oxid of iron; but it will be understood that instead of.the above oxygen-containing metal compound halogenous compounds or sulfur-containing compounds and instead of aluminiu 01 another metal-as, for instance, magnesium, silicium, calcium, or the carbide of these metals-may be partly or wholly used. It will be clear that any oxygen-containing metal compound or halogenous metal compound or sulfur-containing metal compound can be used. The latter compounds will mostly not advantageously be used on account of the sulfur coming into the molten metal. It must further be mentioned that instead of the metals the carbid or alloys of the metals may be used; so, for instance, aluminium carbid, calcium carbid, ferro calcium, ferro silicium, aluminium,

magnesium, or the like. It must further be mentioned that it is not necessary to carry out the whole reaction underneath the surface of the bath, though it will be more advantageous to do so.

It will be understood that the box containing the thermit can also be fixed in the mold at the bottom of or at the side of the same, but beneath the surface of the molten metal when the same is run in. It is only neces; sary that the reaction take place partly underneath' the surface of the molten metal in order to attain the peculiar process of pol ing, which process could never be obtained up to the present time.

It must still be mentioned that the thermit can be introduced underneath the surface of the molten metal in any other convenient way-by, for instance, spraying, pressing, or the like in such a way that the cbullition takes place for a longer time.

Having thus fully described the nature of this invention, what we desire to secure by Letters Patent of the United States is 1. The process of manufacturing homogeneous metal castings, consisting in bringing a mixture of an oxygen-containing metal compound and a metal capable of reacting with this metal compound in reaction under the surface of the molten metal and holding the mixture under the surface of the molten metal while the reaction goes on,for the purpose set forth.

2. The process of manufacturing homogeneous metal castings, consisting in bringing a mixture of an oxygen-containing metal compound and aluminium in reaction under the surface of the molten metal and holding the mixture under the surface of the molten metal while the reaction goes on, for the purpose set forth.

In testimony whereof we have signed our names to this specification in the presence of the subscribing witnesses.

' HANS GOLDSCIIMIDT.

\VALTHER MATl-IESIUS.

Witnesses as to signature of Hans Gold- Schmidt:

WILLIAM ESSENWEIN, PETER LIEBER. I

Witnesses as to signature of \Valther Maihesius:

R. IIEYRICII, G. MEYER.