DE159757C - - Google Patents

Description

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With »Thermit« (see trademark 42771 and 71235) one designates among other things a mixture of aluminum and iron oxide in approximately equivalent amounts, which has the property of continuing to burn by itself, if it has been ignited at one point. This characteristic remains of the mixture if the metals magnesium, CaI-ciimi, Strontium, barium or the metalloid silicon are used in whole or in part, and if an oxygen compound is allowed to take the place of the iron oxide, the metal of which is is less related to oxygen than the one used for production. All of these blends are also Thermite. They are named for a better distinction according to the metals that are excreted in the reaction, i.e.:

Egg senthcrniit, "nickel thermite, chromium thermite, Mangantherniite, titanthermit, etc. In the following, these terms are intended to be precise those mixtures which are meant in each case are identified and the word "thermite" for can be used as a collective name for the genus of chemical mixtures.

It has already been proposed to introduce therethrough thermite or the effluent from the thermite Mclalle in metal baths that either abandons the thermite to the surface of nüssigen !! vein or bringing it to the testis -V- ^r _"v ^P and the metal äßc ; -f let him flee, or that he is thrown into the stream of incoming liquid metal.

This was done for the purpose of producing metal alloys, that is, to introduce certain metals into the Grimdmetall and thereby ^; also to avoid pore formation in the liquid metal. ,

In all of these cases, however, one does not achieve that the mixture actually burns off takes place at the bottom or at a point below the surface of the bath, since also in the case in which the thermite is placed on the bottom of the vessel, that quickly rises to the surface of the metal bath and only burns there. 'But then the thermite becomes more or less due to the already on the surface of every metal bath contaminates existing slags and oxides, which significantly disrupts the smooth course of the reaction; Consequently are the results in terms of making dense metals or dissolving the resulting Metal in liquid metal not uniformly and above all not, perfectly.

As has been established, there is a greater slagging of the in statu nascendi which is deposited Metal; but also the resulting from the reaction Heat transfer considerably due to this disadvantageous type of burning on the impure Metal surface impaired.

If on the other hand - and this is the essential feature of the following

wrote invention - the response within of the metal bath or even at the .PiO (IeIi

If it causes the same thing and there it is more or less brought to an end, so is the use of heat of the thermite introduced into the bath is much larger, since the hot slag parts too (the corundum) have to rise through the metal bath and so some of their heat release, while when the thermite burns on the surface, the heat of the . Corundum very little to use; canoe, as this is mostly through radiation get lost.

All impurities, gases, etc.

now more easily through the hotter and more liquid metal to the surface, and it a denser metal is produced, free of bubbles, gases, or slag inclusions, and both with cast iron and with cast steel, nickel and bronze castingsii, for which the procedure is particularly valuable. But it can also use this procedure for the other metals. Find use. It becomes - and this is remarkable - that aluminogenic metal absorbed almost quantitatively by the metal bath because there is none Finds an opportunity to slag. Furthermore, there is the great advantage that, since ah the . the lowest point of the bath a higher temperature is generated, a strong surge of the liquid mass is caused. This of course creates a very special one good deslagging and rising of the impurities.

You can now achieve these advantages mentioned by using the respective Thermitmisclning briquetted in some way, or that they are enclosed in packs, preferably in tin cans, and it has to then these briquettes, tin cans or the like. By appropriate handling, ζ. Β. by a sturdy iron rod, hit the bottom of the metal bath and in this position held for some time until the reaction progressed sufficiently or stopped is.

The submerged thermite is then completely used up, so that it is not burned Parts of the thermite hardly or not at all

5.0 still came to the surface and the reaction, As requested, ■ look in the bathroom accomplishes. The immediate driving up unbearable Parts of thermite and its flowing apart on the surface of the metal hade, which can be obtained by first throwing it into the pan and then letting it flow again Metal always enters, becomes practical through the described immersion and holding completely avoided.

It is noteworthy that it is possible to add the loose powder mass by means of the stick echo, despite dismantling the liüchsc, if you only look at the outside Has reacted parts of the powder mass. The slag that forms in the process holds and to a certain extent cement the powdery parts that initially react, so that they are in their shape on the ice stick or on the other holding devices despite the lower weight compared to the metal bath «remain, while on the other hand The slag and metal are sufficiently detached again. So the reaction is towards the inside continued to and undisturbed, and the reacting mass always remains intimately touched by the metal bath that immediately followed.

As a result of the type of reaction described above, it is only possible to use thermite to be introduced in non-briquetted form, only in loose packaging. This shell that looks best Sheet metal, as already mentioned, is only used to introduce the thermite into the bath. This sheet metal shell itself is naturally used by the bath, -z. B. iron or steel bath, very quickly resolved, and the connection between the thermite burning in the metal bath is established only achieved by the aforementioned slag envelope, which is also found on the iron rod of: adheres to itself. One can easily get hold of one by pulling out prematurely Convince the iron bar attached rifle of this. This strange process could can only be determined by experiments and is with the sprinkling of the Thermite, with the Throwing the thermite in the bottom of the pan or in the one flowing into the pan Metal cannot be compared at all, because in all these types of addition the thermite is immediate floats and only reacts on the surface.

The essential novelty lies in the fact that the thermite can be prevented from swimming in the bath and until the reaction has occurred completely or until it has ended completely must hold below the surface.

A certain external resemblance to the introduction of thermite in Metal baths possess the introduction of phosphorus into aluminum baths, like the same in the two British patents 27881/1897 and 22753/1901. The phosphorus is packed here in tin cans and pushed under the surface of the metal bath. Due to the heat of the metal bath, phosphorus vapor develops, which as such is now the Metal bath runs through it. Apart from the fact that, according to the inventor, phosphorus only for Aluminum or bronze baths as an additive; can be used, a reaction occurs here iao of the immersed mass is not in itself, but the phosphorus is only through the

Heat from the metal bath is transferred into ■ vapor form and driven through the metal bath.

An example is intended to explain the processes involved in carrying out the method:
Tn a ladle, in which 5 ° ^OO ^ Ji liquid Guileisen from the cupola are embedded, is on a bar α (Fig. I) a thin-walled can with 12 ¹ /. Kg Ferrotitanthermit (3 Ti ₂ O -j- F " 0 _Λ -j- 3 SlI ₂ ) knocked down, as shown in FIG. 2 and maintained in this position until the reaction is over. The slag produced above is skimmed off or retained in the usual way before pouring. .

The titanium is either absorbed by the casting compound or to accommodate Impurities, especially from gases, are consumed and possibly in the slag transferred, so that under certain circumstances only

ao there are still traces of titanium in the casting compound. Nevertheless, the effect of the metal introduction, namely a dense casting, is achieved.

If the temperature of the metal bath is not high enough to use the thermite can ignite, the inflammation can be caused by adding barium supcroxide - aluminum mixture or a similar mixture which has a low ignition temperature, can be effected in a known manner.

The amount of thermite that is added to a metal bath in this way can be completely arbitrary. If it is a question of freshening up dull casts, so-called tilt casts, this addition will of course have to be taken relatively high; it may be a few percent of the amount to be replenished. . Currently at . In this case it is particularly necessary to enable the heating from below upwards. If, on the other hand, it is a question of vigorous stirring of the liquid metal, e.g. B. cast iron, to which about a small amount of titanium is to be added at the same time in order to also bind the nitrogen, so one is already with ¹ A to V ₂ v. Ii. Thermit get along with the weight of the amount of iron.

Much smaller amounts can be used in cases where only ■ is about limited amounts of a liquid steel mass at a certain point of to bring new to a higher temperature. This opportunity of application is found particularly common in metallurgical practice.

1. when casting steel castings and

2. when casting steel blocks.

In the first of the mentioned applications one attaches the thermite narrow enclosed in cans either from the start j at a certain point of the jig funnel or one leads them later in a shaped funnel from above.

The application of thermite described here proves to be particularly advantageous when casting such steel castings which are very large or which are to be produced with very thin walls. In such pieces often the the steel to professional known hitherto inevitable occurs inconvenience that the inside of the mold locomotive steel is so stiff by the cooling effect of the shape that it is traveling inside the form only as a very viscous mass and it only fills it completely, or that the steel is no longer able to fill the riser funnel. If you now bring within the. ; Raising funnels (Fig. 3) at suitable points on bushes b with thermite, which are ignited by the steel flowing past them and held in place as a result of their storage Molecules again and in this way achieves flawless castings.

The heating of the contents of a rising funnel (Fig. 3 a) by thermite proves z. B. also particularly advantageous in that in this way the in the The steel in the funnel can give a much higher temperature than that in the middle part of the casting has steel, with relatively very little Quantities of thermite. The consequence of this is that the steel in the funnel is considerable remains liquid longer than that in the usable part of the casting, and that the funnel is only really enabled as a storage space for liquid To serve steel, from which the volume reduction of the solidified in the steel castings Steel can be compensated automatically during this time. This will result in the formation of a with complete certainty Avoid voids in the usable cast steel below this funnel.

To avoid cavities, however, one can also use the one enclosed in cans Use thermite in the production of forged or rolled steel ingots. The education Up to now attempts have been made to avoid voids within these steel blocks by that the head of such a block is kept open as long as possible and then hot steel is inserted into it to fill the cavities refills. Nevertheless, Lunker- iao can be found in such blocks as a normal phenomenon that reach down from the top to the first third of the block or even lower.

AS ⁰ ! 1-5'l

These cavities can no longer be filled by refilling because the head of the Block, before the formation of the same occurs, had already frozen so far that it created new, liquid steel could no longer pass through. Thermit now offers a means, the to keep the freezing head of a block fluid longer than before, and the block like this capable of further absorption of liquid steel

ίο to make. The previously proposed application, sprinkle the thermite on the surface of the watering head and there to cause inflammation has not had any practical success, since that of thermite Developed heat could not be conducted to the correct location of the casting. The new way of working is as follows:

Thermit is, as already described above, in briquette form or in sheet metal

ao rifles included, attached to a strong iron rod and with this through the upper solidification crust of the block through about 1 m deep - depending on the size of the Block - pushed into the block (Fig. 4). The thermite ignites immediately and burns off quickly due to the higher temperature of the steel; there is a lively reaction and one of the most used Amount of thermite corresponding heat generation. As a result, the steel inside the block head is restored liquid or liquid and fills the cavity parts, while at the top of the head large open funnel, which can be poured out immediately with the steel held ready got to. This measure can be repeated after a while, and it succeeds in this way Almost all of the cavities are avoided.

In the above description, the use of thermite is particularly mentioned, which is a mixture of a metal oxygen compound, especially an iron oxide with aluminum, represents; but for the purposes mentioned, a halogen compound can also be used in place of the oxygen compound, Instead of aluminum, another reactive metal, such as e.g. B. Magnesium, Silicon, calcium or their carbides are taken in whole or in part.

You can of course use any metal oxygen compound or metal halogen compound or metal sulfur compound, but one will use the latter compounds, if possible, refrain from it, as sulfur can get into the bath under certain circumstances,

It should also be mentioned that instead of metals, carbides or alloys are used the metals mentioned, so z. B. aluminum carbide, calcium carbide, ferrocalcium or Can use ferro-silicon or aluminum-magnesium.

It should also be noted that the reaction naturally does not end below the surface must be carried out, although this is advantageous. .

It should also be noted that the insertion sleeve in the relevant mold on the bottom or on the side, but at least always below the surface of the later casting bath from the start or later is attached or held.

It is only necessary that the reaction takes place for the most part under the bath surface, so that at the same time the peculiar mixing of the bath is ensured to a sufficient extent. With cast steel also, also as described, this mixture, e.g. B. from Thermit, under the actual Surface immersed so to speak in the bath and there the reaction more or less carried out, so that one also here can speak of a ^ bath and a bath surface.

It should also be mentioned that the attachment of the reactive mixtures below the bath surface can also be done in such a way that the whole mass cannot be poured into the bath at once Introduces bath, but that one the mixtures by injecting or pressing in and after bathing for a more convenient application or longer duration of the reaction to achieve.

Claims (1)

Patent claim: Process for the production of pore-free and void-free metal castings by action of reactive, brought under the surface of the metal to be treated Mixtures of a metal, e.g. B. aluminum, with an oxygen or halogen or sulfur compound or Salting of a metal on liquid metals, characterized in that the reactive Mixture firmly arranged or held under the surface of the liquid metal is, for the purpose that the heat released during the reaction to " let certain areas of the casting act and fully utilize it. 1 sheet of drawings.