Appeal 2007-2242
Application 10/352,997
examples is 6.64% (Lee, p. 9, Table 1, steel #13). Lee provides little, if any,
motivation to try at least 7.3% Ni.
With respect to Cr, Lee discloses (Lee, p. 4, ll. 41-44; emphasis
added):
The Cr is an important element for improving the corrosion
resistance. If the content of Cr is less than 22%, the duplex stainless
steel cannot have the required corrosion resistance. On the other
hand, if it exceeds 27%, the precipitation rate of intermetallic
compounds becomes faster, with the result that the corrosion
resistance and the impact toughness are decreased. Therefore, the
content of Cr should be preferably limited to 22-27%.
Applicants claim steel containing “26% or more, but less than 28%”
of Cr (Br. app. A). None of Lee’s 48 examples contains Cr in an amount of
at least 26% (Lee, pp. 9-11). In fact, the highest Cr percentage in any
example is 25.55% (Lee, pp. 9-10, Table 1, steel #19, 32, and 42). Again,
Lee points to a mass percentage different than Applicants’ 26-28%.
Finally, with respect to N, Lee discloses (Lee, p. 4, ll. 55-59; emphasis
added):
The N is a strong austenite stabilizing element, and improves
the corrosion resistance. If the content of N is less than 0.13%, the
duplex stainless steel cannot have the required corrosion resistance,
and promotes the precipitation of the intermetallic compounds. On
the other hand, if the content of N exceeds 0.27%, then the austenite
phase is too much reinforced, with the result that the hot ductility is
decreased. Therefore, the content of N should be preferably limited to
0.13-0.27%. However, if the content of S is less than 0.002%, the
content of N can be increased up to 0.3%.
Applicants claim steel containing “more than 0.3%, but no more than
0.4%” of N (Br. app. A). Lee teaches that the content of N should be
preferably below 0.27% (Lee, p. 4, ll. 58-59). If the content of N exceeds
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