Patent ID: 6962632
Filing Date: 2005-11-08
Classification: C22C,C22F

Abstract:
1. A method of preventing preferential corrosion of an extruded material, the method comprising: homogenizing an aluminum alloy ingot, wherein the aluminum alloy ingot consists of 0.8-1.5 wt % Mn, 0.1-0.7 wt % Fe, and 0.03-0.6 wt % Si, and optionally one or more of 0.00-0.45 wt % Cu, 0.0-0.3 wt % Mg, 0.0-0.3 wt % Cr, 0.0-0.1 wt % Ti, 0.0-0.5 wt % Zn, 0.0-0.3 wt % Zr and 0.0-0.3 wt % Ni, the balance being aluminum and any unavoidable impurities; port hole extruding the aluminum alloy ingot to produce a port hole extruded aluminum alloy; and drawing the port hole extruded aluminum alloy to form a hollow material, wherein a difference in electric conductivity of individual portions in a lengthwise direction of the hollow material is not more than 1 IACS %, and such that an electric conductivity value becomes at least 39.0 IACS %; wherein said homogenizing is regulated to precipitate sufficient Mn prior to extruding and drawing so as to produce said 1 IACS % or less conductivity difference in a lengthwise direction of the hollow material and wherein said homogenizing of the ingot is carried out by maintaining the ingot at a first temperature of 500-630° C. for more than zero but not more than about 24 hours, cooling the ingot down to a second temperature of 400-500° C. at a cooling velocity of not more than 100° C./hr, and maintaining the ingot at said second temperature for about 4 to 48 hours and wherein a preferential corrosion of a welded portion of the hollow material is inhibited.