Appeal 2007-2359
Application 90/006,951
14. According to the Specification, if the Si content is too low, the alloy
strength is too low; and if the Si content is too high, the extrudability of the
alloy is reduced. The Si content of the alloy is 0.35–0.60,
preferably 0.40-0.59. (359 patent at 2:64–3:5.)
15. The presence of iron is said to be unavoidable in practice because it is
too expensive to remove; and, in certain applications at least 0.15 % Fe is
said to be desirable. Iron may be present up to 0.35 %. (359 patent
at 3:6-16.)
16. Most importantly, Fe is said to be present in as-cast alloy ingots as
large plate-like β-AlFeSi particles (359 patent at 3:12–13), which are said to
contribute to a reduction in surface quality at a given temperature and
extrusion speed (Parson's Declaration8 at 6).
17. According to the Specification, β-AlFeSi is preferably converted to
substantially (at least 80%) α-AlFeSi by a heat-treatment referred to as
"homogenisation" (henceforward "homogenization"). (359 patent at 3:13-16
and at 4:19–26.)
18. According to the Specification, the inventors discovered that adding
an appropriate level of Mn, given by the equation
wt% Mn ≥ 0.3 × wt% silicon - 0.12
promotes the β- to α-AlFeSi transformation during homogenization,
decreases the AlFeSi particle size, and increases the "degree of
spheroidization" of the AlFeSi particles in the alloy. (359 patent at 3:24-52.)
8 Declaration of Nicholas Charles Parson, one of the inventors, under
37 C.F.R. § 1.132, filed in the reexamination on 3 January 2006.
6
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