Appeal No. 2003-1332 Page 6
Application No. 09/797,143
reductions in production down time and improved manufacturing efficiency. Danis
teaches (column 2, line 33 to column 3, line 1) that:
The steel raw material used for forming the valve body may comprise any
cold formable grade of low-carbon or 35 low-alloy steel which is susceptible to
case hardening such as by carbonitriding or carburizing including steel having a
carbon content ranging from about 0.03% to about 0.6%. Carbon contents in a
range of from about 0.08% to about 0.25% are prepared for maximum
workability of the material as may be required in the most complex forming
operations. In addition to the carbon constituents in the steel, the steel may
further contain in addition to conventional quantities of impurities, up to about 5%
of intentional alloying elements employed in standard SAE steel grades including
alloying constituents such as nickel, manganese, chromium, molybdenum,
boron, silicon, vanadium, etc.
The specific composition of the steel or low-alloy steel can be varied
within the aforementioned definition to provide a resultant steel having a degree
of ductility sufficient to enable cold-formation of the steel blanks into a valve of
the desired configuration. . . .
A steel which has been found eminently as satisfactory in accordance with
the practice of the present invention comprises a fully annealed SAE 1018 steel
which has a sufficient degree of ductility to enable cold deformation of the blank
into poppet-type valve configurations of the most complex configuration presently
employed in commercial automobile engines. The composition of an SAE 1018
steel typically includes 0.15-0.20% carbon, 0.60-0.90% manganese, 0.4%
maximum phosphorous, 0.5% maximum sulfur, and the balance iron.
Danis teaches that the valve made from a low carbon steel is subjected to a
case-hardening treatment to provide a hard surface layer on the surfaces thereof to
increase its wear resistance. Danis provides (column 4, lines 53-72) that:
The type of case hardening and the degree of case hardening achieved
will also vary consistent with the intended end use of the valves. In many cases
it is necessary that only the valve tip indicated at 16 in FIG. 4 be fully hardened
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