Aluminum alloy free from aluminum carbide

Abstract

An aluminum alloy for producing an aluminum strip for lithographic print plate carriers, a method for producing an aluminum alloy for lithographic print plate carriers, in which, during the production of the aluminum alloy, after the electrolysis of the aluminum oxide, the liquid aluminum, up to the casting of the aluminum alloy, is supplied to a plurality of purification steps, as well as an aluminum strip for lithographic print plate carriers and a corresponding use of the aluminum strip for lithographic print plate carriers include a carbide content of less than 10 ppm, and preferably less than 1 ppm. As a result, the aluminum alloy, the method for producing the aluminum alloy, the aluminum strip, and corresponding use of the aluminum strip for lithographic print plate carriers described herein allow for the use of virtually gas-tight coatings.

1 . Aluminum alloy for producing an aluminum strip for lithographic print plate carriers, the aluminum alloy having an aluminum carbide content of less than 10 ppm, wherein the aluminum alloy has the following alloying constituents in % by weight:
 0.05%≦Mg≦0.3%,
 Mn≦0.3%, 
   0.4%≦Fe≦1%,   0.05%≦Si≦0.5%,
 Cu≦0.04%, 
 Ti≦0.04%, 
   
     unavoidable impurities individually max. 0.01%, in total max. 0.05% and remainder Al. 
   
   
       2 . Aluminum alloy according to  claim 1 , wherein the aluminum alloy has the following alloying constituents in % by weight:
 0.1%≦Mg≦0.3%,
 Mn≦0.05%, 
   0.3%≦Fe≦0.4%,   0.05%≦Si≦0.25%,
 Cu≦0.04%, 
 Ti≦0.04%, 
   
     unavoidable impurities individually max. 0.01%, in total max. 0.05% and remainder Al. 
   
   
       3 . Method for producing an aluminum alloy for lithographic print plate carriers, in which during the production of the aluminum alloy after electrolysis of the aluminum oxide, liquid aluminum, up to casting of the aluminum alloy, is supplied to a plurality of purification steps and a proportion of aluminum carbides in the aluminum alloy is lowered by one or more purification steps to less than 10 ppm, wherein after the electrolysis of the aluminum oxide, the liquid aluminum is supplied to a stirring station, in which inert gases are introduced into the liquid aluminum whilst stirring, the duration of the stirring and blowing in of the inert gas into the aluminum melt in the stirring station being at least 10 minutes. 
   
   
       4 . Method according to  claim 3 , wherein a composition of the aluminum alloy corresponds to an aluminum alloy of the type AA1xxx, AA3xxx, or AA8xxx. 
   
   
       5 . Method according to  claim 3 , wherein the liquid aluminum supplied to the stirring station is obtained at least partially from cold metal. 
   
   
       6 . Method according to  claim 3 , wherein aluminum fluorides are added during the stirring of the liquid aluminum in the stirring station. 
   
   
       7 . Method according to  claim 3 , wherein to add alloying constituents, the aluminum is supplied to a furnace and is left to stand in the furnace for at least more than 30 minutes after the alloying has taken place in the furnace by stirring and the addition of the alloying constituents. 
   
   
       8 . Method according to  claim 3 , wherein a gas flushing with inert and/or reactive gases takes place in the furnace. 
   
   
       9 . Method according to  claim 3 , wherein the aluminum alloy is supplied, after the furnace, to a rotor degassing and is flushed with a mixture of inert and/or reactive gases. 
   
   
       10 . Method according to  claim 3 , wherein the aluminum alloy is subjected to at least one segregation step. 
   
   
       11 . Method according to  claim 3 , wherein the aluminum alloy is filtered prior to the continuous or strip casting, the filter having a high filter effectivity for particles with a size of less than or equal to 5 μm. 
   
   
       12 . Aluminum strip for lithographic print plate carriers produced by continuous or discontinuous casting of an aluminum alloy with subsequent hot and/or cold forming, the aluminum alloy being produced using a method according to  claim 3 . 
   
   
       13 . Aluminum strip according to  claim 12 , wherein the rolling oil residues on the aluminum strip for lithographic print plate carriers have been removed by annealing and degreasing the strip. 
   
   
       14 . Aluminum strip according to  claim 12 , wherein the aluminum strip is subjected to a first degreasing using an acid or alkaline medium and then subjected to a further degreasing using a pickling process. 
   
   
       15 . Use of the aluminum strip for lithographic print plate carriers according to  claim 12  for producing lithographic print plate carriers with a gas-tight coating. 
   
   
       16 . Method according to  claim 3 , wherein a composition of the aluminum alloy has an aluminum carbide content of less than 10 ppm and has the following alloying constituents in % by weight:
 0.05%≦Mg≦0.3%,
 Mn≦0.3%, 
   0.4%≦Fe≦1%,   0.05%≦Si≦0.5%,
 Cu≦0.04%, 
 Ti≦0.04%, 
   
     unavoidable impurities individually max. 0.01%, in total max. 0.05% and remainder Al.