Continuous cast aluminium alloy rod and production method and apparatus thereof

Abstract

A continuously cast aluminum alloy rod 101 is produced through a horizontal continuous casting method employing a tubular mold which is supported such that its center axis extends substantially horizontally and which has a forced cooling device. The rod includes a Si-rich portion 104 having a thickness of at least 20 μm on a surface of a lateral side of the rod that has a central angle 103 of at least 30°.

1 . A continuously cast aluminum alloy rod produced through a horizontal continuous casting process employing a tubular mold which is supported such that its center axis extends substantially horizontally and which has a forced cooling means, said rod comprising a Si-rich portion having a thickness of at least 20 μm on a surface of a lateral side of the rod that has a central angle of at least 30°.  
   
   
       2 . The continuously cast aluminum alloy rod according to  claim 1 , wherein the Si-rich portion has a Si microstructure containing primary (α-Al crystals whose percentage area is less than 50% as determined in a micro-crystallographic image obtained from a radial cross section of the rod.  
   
   
       3 . The continuously cast aluminum alloy rod according to  claim 2 , wherein the Si microstructure contains Si grains having an average grain size of 0.1 to 5 μm.  
   
   
       4 . The continuously cast aluminum alloy rod according to any one of  claims 1  to  3 , wherein it contains Si in an amount of 7 to 14 mass %.  
   
   
       5 . The continuously cast aluminum alloy rod according to any one of  claims 1  to  4 , wherein it contains Ca in an amount of at least 0.003 mass %.  
   
   
       6 . The continuously cast aluminum alloy rod according to any one of  claims 1  to  5 , wherein it has a surface roughness Rmax of 50 μm or less and, when being subjected to peeling after casting, has no tool mark on the surface thereof.  
   
   
       7 . A method for producing a continuously cast aluminum alloy rod using a tubular mold which is supported such that its center axis extends substantially horizontally and which has a forced cooling means, said method comprising controlling a difference between a temperature of a molten aluminum alloy being teemed into the tubular mold and a solidification temperature thereof and casting a rod to form an Si-rich portion having a thickness of at least 20 μm on a surface of a lateral side of the rod having a central angle of at least 30°.  
   
   
       8 . The method for producing a continuously cast aluminum alloy rod according to  claim 7 , further comprising controlling a speed of removing the rod from the tubular mold.  
   
   
       9 . The method for producing a continuously cast aluminum alloy rod according to  claim 7  or  8 , further comprising employing as a raw material a molten aluminum alloy containing Si in an amount of 7 to 14 mass % and Ca in an amount of at least 0.003 mass %, regulating a casting speed to be 200 to 1,500 mm/min and the temperature of the molten aluminum alloy to be equal to or higher than a liquidus temperature of the alloy and using as the tubular mold a mold made of a material that is one species or a combination of two or more species selected from among aluminum, copper, and alloys thereof and having an effective mold length of 15 to 70 mm.  
   
   
       10 . The method for producing a continuously cast aluminum alloy rod according to  claim 9 , wherein the molten aluminum alloy is added with Ca in an amount of at least 0.003 mass %.  
   
   
       11 . The method for producing a continuously cast aluminum alloy rod according to  claim 10 , wherein the Ca is metallic Ca having a purity of at least 99.9 mass %.  
   
   
       12 . The method for producing a continuously cast aluminum alloy rod according to any one of  claims 8  to  11 , wherein the tubular mold includes, on its inner wall which comes into contact with the molten aluminum alloy, a ring-shaped permeable porous member having an air permeability of 0.005 to 0.03 L/(cm 2 ×min).  
   
   
       13 . The method for producing a continuously cast aluminum alloy rod according to  claim 12 , wherein the permeable porous member is provided within a range of 5 to 15 mm of the effective mold length.  
   
   
       14 . An apparatus for producing a continuously cast aluminum alloy rod, comprising a melting furnace  502  which reserves therein molten aluminum alloy and from which the molten aluminum alloy is fed; a casting section  504  which is provided with a cylindrical mold  201  and a cooling means  202  and at which the molten aluminum alloy is cast into a solidified cast ingot; a removal drive section  505  at which the solidified cast ingot is removed substantially horizontally from the cylindrical mold to form a continuously cast aluminum alloy rod  101  having a Si-rich portion  104 ; a detection section  506  at which a region of the Si-rich portion is detected and from which detected signals are output; a determination section  508  at which the detected signals are compared with preset determination conditions and from which determination signals are output; and a control unit  509  that controls a temperature of the molten aluminum alloy in the melting furnace, the cooling means of the casting section and a removing speed of the removal drive section so that the detected signals fall within the preset determination conditions based on the determination signals.  
   
   
       15 . The apparatus for producing a continuously cast aluminum alloy rod according to  claim 14 , further comprising a Ca introducing section  503  that is controlled by means of the control unit  509  so that the detected signals fall within the preset determination conditions based on the determination signals.  
   
   
       16 . The apparatus for producing a continuously cast aluminum alloy rod according to  claim 15 , further comprising an analysis section  507  at which a composition of the molten aluminum alloy is analyzed and which outputs Ca amount measurement data signals based on analyzed results to the determination section  508 , and the control unit  509  controls the Ca introducing section  503  so that a Ca amount falls within the preset determination conditions based on the determination signals from the determination section.