BE496600A - - Google Patents

Description

       

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  DEGASING PROCESS FOR METALS AND LIGHT ALLOYS.



   The present invention relates to an improved process for degassing foundry metals and light alloys.



   It is known that these products deteriorate rapidly, during the fusion, by dissolution of gases and formation of oxides. Castings, obtained from untreated molten metals, are porous and loaded with inclusions.



   To avoid these drawbacks, it has been proposed to bubble chlorine in the molten metal before operating the casting. This degassing process, although effective, is not widely used because of the difficulties inherent in handling chlorine. In an improved process, it has been recommended to replace the bubbling of chlorine by the introduction of solid hexachloroethane which, at the melting temperature, gradually releases chlorine by thermal decomposition,
It has now been discovered the surprising fact that hexachlorcyclohexane, despite its relatively high hydrogen content and although the products of its thermal decomposition contain little or no chlorine,

   can advantageously serve as an active product in the refining charges used for the degassing and refining of metals and light alloys. technical hexachlorcyclohexane is generally obtained by additive chlorination of benzene. The crude chlorination product consists of a mixture of isomers in which the @ isomer predominates. Although the mixture of these isomers is suitable for carrying out the degassing according to the process of the present invention, the @ -isomer, a mixture enriched in O ('isomers or any other hexachlorcyclohexane by-product of the manufacture of the @ isomer.



   The hexachlorcyclohexane-based degassing composition is advantageously used in the form of briquettes or pellets of 40 to 50 grams.



  This composition may contain additional substances such as sodium carbonate and stearin which facilitate briquetting or pelletizing as well as known products having properties of refining the grain of the metal. Good results have been obtained with compositions containing at least 50% hexa-

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   chlorcyclohexane, the remainder being a mixture of low point halides, melting point, boron compounds, sodium carbonate, stearin, etc.



   The amount of hexachlorcyclohexane to be used varies with the nature and the impurities of the metal. Generally 1 g of hexachlorcyclohexane per kilogram of molten metal gives very satisfactory results. A significant improvement can already be observed when adding 0.25 g of hexachlorcyclohexane per kilogram of metal.



    EXAMPLE I.-
An alloy of the ALPAX type (aluminum-silicon) is treated with hexachlorcyclohexane @ at a rate of 1 gr / kg of metal.



   Microphotographic examination of samples taken from the cast metal shows that the porosities found in the untreated metal are completely absent from the metal treated with hexachlorcyclohexane. The grain structure of the treated metal is also significantly finer. These observations are confirmed by the tensile tests which indicate a breaking load of 12.4 Kgr / mm2 for the sample taken from the metal treated with hexachlorcylclohexane a- when it is only 9.2 Kgr / mm2 for the untreated metal sample.



  The elongations are 6.3% and 3.2% respectively.



  EXAMPLE II .-
An aluminum-copper alloy, with a low copper content, is treated after melting with a refining composition having the following composition:
 EMI2.1
 
<tb> Hexachlorcyclohexane <SEP> @ <SEP> 600
<tb>
<tb>
<tb> Chloride <SEP> of <SEP> sodium <SEP> 75
<tb>
<tb>
<tb>
<tb> <SEP> potassium <SEP> <SEP> 75 chloride
<tb>
<tb>
<tb>
<tb> Nitrate <SEP> of <SEP> potassium <SEP> 40
<tb>
<tb>
<tb>
<tb> <SEP> sodium <SEP> fluoride <SEP> 15
<tb>
<tb>
<tb>
<tb> Fluosilicate <SEP> of <SEP> sodium <SEP> 15
<tb>
<tb>
<tb>
<tb> Boric <SEP> <SEP> 100
<tb>
<tb>
<tb>
<tb> Carbonate <SEP> of <SEP> soda <SEP> 50
<tb>
<tb>
<tb>
<tb> Stearin <SEP> 30
<tb>
<tb>
<tb>
<tb>
<tb> 1000
<tb>
 
The refiner is introduced in the form of tablets of approximately 40 g at a rate of 1 g / kg of metal.

   The tensile tests indicate a breaking load of 15.6 Kgr / mm2 for the treated sample and 14.6 Kgr / mm2 for the untreated sample. The elongations are 5.7 and 1.2% respectively.



    CLAIMS the process for degassing metals and light alloys' characterized in that the molten metal is treated with hexachlorcyclohexane.


    

Claims (1)

2. - Method according to claim 1, characterized in that the hexa-chlorcyclohexane used is the @ isomer. 3. - Method according to claim 1, characterized in that the hexa-chlorcyclohexane used is a mixture of isomers containing predominant amounts of isomer @. 4.- Method according to the preceding claims, characterized in that the hexachlorcyclohexane is mixed with other substances capable of refining the grain of the metal. 5. - Compositions for the degassing of metals and light alloys, characterized in that they contain hexachlorcyclohexane. <Desc / Clms Page number 3> 6. Improved light metals and alloys obtained according to the process described above.