Aluminum alloy sheet

Abstract

The present invention relates to an Al—Mg—Si sheet which contains, in terms of mass %, 0.3-1.0% Mg, 0.5-1.5% Si, 0.005-0.2% Sn, 0.02-1.0% Fe, and 0.02-0.6% Mn, with the remainder comprising Al and unavoidable impurities, characterized by having a structure wherein compounds that are detected with an SEM having a magnification of 500 diameters and are identified with an X-ray spectrometer include Sn compounds which contain Mn and Fe and which have an Sn content of 1.0 mass % or higher and a diameter of 0.3-20 μm in terms of equivalent circular diameter, the average number density of the Sn compounds being 500-3,000 /mm 2 , and wherein the length of the boundary between each Sn compound and the aluminum matrix is in the range of 3-20/mm on average in terms of value obtained by dividing the total peripheral length of the Sn compound grain by the area thereof determined with the SEM. This aluminum alloy sheet satisfies the formability after natural aging at room temperature and bake hardenability which are required of automotive outer panels, and has excellent filiform rust resistance.

1 . An aluminum alloy sheet which is an Al—Mg—Si alloy sheet comprising, in terms of mass %:
 0.3-1.0% of Mg, 
 0.5-1.5% of Si, 
 0.005-0.2% of Sn, 
 0.02-1.0% of Fe, and 
 0.02-0.6% of Mn, 
 with the remainder being Al and unavoidable impurities, 
 the aluminum alloy sheet having a microstructure wherein: among compounds as examined with an SEM with a magnification of 500 times and identified with an X-ray spectrometer, an Sn compound comprising Mn and Fe, having an Sn content of 1.0 mass % or higher, and having an equivalent circular diameter in a range of 0.3-20 has an average number density in a range of 500-3,000 counts/mm 2 ; and a boundary between the Sn compound and an aluminum matrix has a length in a range of 3-20 /mm on average in terms of a value obtained by dividing a total peripheral length of the Sn compound by an area as examined with the SEM. 
 
     
     
         2 . The aluminum alloy sheet according to  claim 1 , further comprising at least one kind of ingredient selected from the group consisting of
 more than 0% and 0.4% or less of Cr,   more than 0% and 0.3% or less of Zr,   more than 0% and 0.3% or less of V,   more than 0% and 0.1% or less of Ti, more than 0% and 0.4% or less of Cu,   more than 0% and 0.2% or less of Ag, and   more than 0% and 1.0% or less of Zn, in terms of mass %.   
     
     
         3 . An Al—Mg—Si alloy comprising, in terms of mass %,
 0.3-1.0% of Mg, 
 0.5-1.5% of Si, 
 0.005-0.2% of Sn, 
 0.02-1.0% of Fe, and 
 0.02-0.6% of Mn, 
 with the remainder being Al and unavoidable impurities. 
 
     
     
         4 . The Al—Mg—Si alloy of  claim 3 , further comprising at least one kind of ingredient selected from the group consisting of
 more than 0% and 0.4% or less of Cr, 
 more than 0% and 0.3% or less of Zr, 
 more than 0% and 0.3% or less of V, 
 more than 0% and 0.1% or less of Ti, more than 0% and 0.4% or less of Cu, 
 more than 0% and 0.2% or less of Ag, and 
 more than 0% and 1.0% or less of Zn, in terms of mass %. 
 
     
     
         5 . A sheet comprising the Al—Mg—Si alloy of  claim 3 . 
     
     
         6 . A sheet comprising the Al—Mg—Si alloy of  claim 4 . 
     
     
         7 . The sheet according to  claim 5  that comprises an aluminum matrix containing a Sn compound comprising Sn, Mn and Fe, wherein the content of Sn in the compound is 1.0% by mass or higher,
 wherein the Sn compound in the aluminum matrix has an equivalent circular diameter ranging from 0.3 to 20 μm and the Sn compound has an average density ranging from 500 to 3,000 counts/mm 2 , and 
 wherein a boundary between the Sn compound and the aluminum matrix ranges in average length ranging from 3 to 20/mm and has a length in a range of 3-20 /mm on average in terms of a value obtained by dividing a total peripheral length of the Sn compound by an area as examined with the SEM. 
 
     
     
         8 . The sheet according to  claim 6  that comprises an aluminum matrix containing a Sn compound comprising Sn, Mn and Fe, wherein the content of Sn in the compound is 1.0% by mass or higher,
 wherein the Sn compound in the aluminum matrix has an equivalent circular diameter ranging from 0.3 to 20 μm and the Sn compound has an average density ranging from 500 to 3,000 counts/mm 2 , and 
 wherein a boundary between the Sn compound and the aluminum matrix ranges in average length ranging from 3 to 20/mm and has a length in a range of 3-20 /mm on average in terms of a value obtained by dividing a total peripheral length of the Sn compound by an area as examined with the SEM.