DE3111611C1 - Process for preventing segregation of an aluminothermic mixture - Google Patents

Description

The invention relates to a method for preventing segregation of an aluminothermic mixture during storage and transport.

Aluminothermic mixtures consist of finely divided aluminum and heavy metal oxides, with the Mixture to dampen the reaction and / or to form an alloy during the reaction finely divided metals, metal oxides or other alloy elements, such as. B. iron filings, copper, copper oxides, Chromium, manganese, carbon or the like can be added.

To achieve a uniform reaction and its controlled course, it is necessary that the reactants contained in the aluminothermic mixture within a given particle size range and with a desired particle size distribution.

The different specific weights of the reactants in the aluminothermic mixture as well as their specific particle shape cause during transport and storage, especially with shaking Stress that cannot be ruled out during loading and transport, changes the optimally set mixing ratio of the reactants during production a packaging unit, e.g. B. a cloth bag containing 7 to 15 kg of aluminothermic mixture as the usual form of packaging for aluminothermic welding compounds for carrying out aluminothermic Rail connection welds.

This segregation can lead to an uneven course of the aluminothermic reaction. Is for For example, in the case of aluminothermic rail welding, the reaction is too violent due to segregation or unevenly, e.g. B. a part of the melt can be thrown out of the crucible, whereby the Operating personnel is at risk and there is also undesirable defective welds as a result of missing weld metal or the formation of alloys Composition can come. Separated aluminothermic mixtures can also react too slowly, which can lead to heat losses and thus also to faulty welds. Since the predominant part of the aluminothermic Gemisehe used for rail connection welding such sources of error must be ruled out for reasons of road safety.

Attempts have been made to counteract the segregation of aluminothermic mixtures by the reactants are pelleted. However, this requires inorganic or organic binders. A possible organic binding agent is water glass, with which the aluminothermic mixtures can be increased and solidify with CO2.

However, this introduces foreign elements into the reaction mixture which are in the molten metal can disturb. If organic binders are used, the organic components can be used Gas development during the reaction and thus lead to porous reaction products. Another disadvantage pelletized mixtures lies in the increase of the Schüiivoiumens. Due to the sudden development of heat in the aluminothermic reaction, the air contained in the bed expands and causes violent splashing of the reaction mass at the beginning of the reaction.

The invention is based on the object of a simple solution to the problem of preventing the To find segregation of the aluminothermic mixtures optimally mixed during production without substances that remain in the aluminothermic reaction must be added to the mixture or disturb in case of staying. In particular, the bulk density of the reaction mixture should not be reduced will. All application properties of the aluminothermic mixture should be unchanged stay.

It is well known to use powdery, pourable materials such. B. ground coffee in airtight Packing containers such as plastic bags, evacuating the air from the packaging and the container to close airtight in the evacuated state. The packaging material hugs it tightly packaged well.

Another packaging method is described in DE-OS 26 45 882, which describes a method for forming a evacuated, sealed pack by providing a pouch with an open mouth that closes a containing the packaging product by inserting a steam injection nozzle into the mouth area of the Bag and by injecting steam by means of the nozzle into the bag, which is characterized is that air is pushed out of the interior of the bag by means of the steam, while pulling forces are transverse are brought into action via a side region of the mouth of the bag in such a way that these forces Stretch the bag sideways and lay the mouth of the bag flat on the nozzle, after which the nozzle out of the bag is removed while the lateral tensile forces are maintained in the lateral area such that the bag closes progressively behind the nozzle, and that the evacuated bag is then sealed or is welded.

From CH-PS 4 05 153 is also an oxygen-free, gas-tight packaging made of flexible packaging material for Filling goods that develop carbon dioxide, e.g. B. coffee beans known, characterized by at least one Insert provided within the packaging container, soft a means for binding the carbon dioxide contains.

This prior art thus teaches a packaging technique, the basic idea of which is the packaging of a Free-flowing goods in the smallest of spaces, with simultaneous protection against the effects of oxygen, in particular to preserve flavorings. Problems of segregation do not play a role here and are in this prior art is not discussed.

It is therefore surprising that the invention The object can be achieved in a simple manner that the alüminothermal mixture with a small amount of a CCV binding agent in a flexible, essentially airtight plastic film Fills the existing packaging unit, the air in the packaging unit by CO2 displaced and the packaging unit in a manner known per se, including a possible hermetically sealed with a small volume of CO2.

As a result of the absorption of the carbon dioxide, the film forming the packaging unit is laid down within a short period of time Time close to the alüminothermal mixture, which is solidified into a block. There is no segregation more is possible. At the point of use, the packaging unit is torn open or cut open the slide opened. The alüminothermal mixture is back immediately after opening the packaging free-flowing and can be poured into the reaction crucible.

The CO2-binding agent can be distributed in the aluminothermic mixture. This is possible above all if the CCh-binding agent does not interfere with the alüminothermal reaction and does not contaminate the molten metal obtained. Particularly preferred, therefore, as an effective, inexpensive and metallurgically indifferent CXV binder is finely divided soda lime. In the aluminothermic reaction, the majority of the alkali carbonate evaporates as oxide, the alkaline earths are absorbed by the slag. ⁴ ^

However, the CO2-binding agent can be packed separately and packed in a CXV-permeable manner in the packaging unit. The CO ₂ -binding agent can be packaged in a cartridge or a bag made of paper or textile material. It is then possible, after opening the packaging of the aluminothermic mixture before the reaction, to remove the cartridge or the pouch containing the agent which has absorbed the carbon dioxide.

The packaging unit for the alüminothermal mixture usually consists of a sack or Bag made of thermoplastic plastic film, which is closed in a simple manner by welding can be. To achieve higher strength, you can also use a film, which in particular is lined with paper on the outside.

In particular, polyethylene films with a thickness of about 0.1 to 0.3 mm have proven suitable as film material.

The following example shows a possible implementation of the method according to the invention.

example

A tube made of polyethylene film is transversely welded into a bag with a width of 20 cm and 40 cm long. 10 kg of an aluminothermic mixture of iron oxide, Aluminum grit, fine blasting granules and manganese powder filled in. A cotton fabric pouch with the Dimensions 5 x 5 cm, which contains 5 g of soda lime, is also inserted. The ones in this packaging unit Any air present is now removed by blowing in CO2 and replaced by CO2. Then the The bag is welded shut and the alüminothermal mixture is distributed in the form of a plate. After a few minutes the film is so tightly placed around the alüminothermal mixture that a plate-shaped, rigid block originated. This rigid block is easy to box and ship. Even after one Observation time of several months, there is no noticeable change in the nature of the packaged, rigid mixture. At the point of use, the film is cut open and the bag with the Soda lime taken. The mixture is free-flowing again and can, as originally mixed, into the Pouring the pouring pot. The alüminothermal reaction thus proceeds in the desired manner and leads to reaction products of a defined amount and composition.

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Claims (5)

Patent claims: 1. Method of preventing segregation of an aluminothermic mixture on storage and transport, characterized in that the aluminothermic mixture is put together with a small amount of a CCV binding agent into one of more flexible, essentially airtight plastic film fills the existing packaging unit, which is in the packaging unit displaced air by CO2 and the packaging unit in a manner known per se including the smallest possible volume of CO2 hermetically sealed. 2. The method according to claim 1, characterized in that the CCV binding agent in the aluminothermic mixture is distributed. 3. The method according to claim 1, characterized in that the CXV binding agent in one CCh-permeable container packed in the Packaging unit is inserted. 4. The method according to claim 3, characterized in that the CO2-binding agent in one Bag made of paper or textile material is inserted into the packaging unit. 5. The method according to one or more of the preceding claims, characterized in, that soda lime is used as a CCV binding agent.