| The effects
of Mo and Si on formability, high temperature
strength, and oxidation resistance of the
15%Cr ferritic stainless steel were investigated
in order to develop a high heat-resistant,
high formability stainless steel suitable
for automotive exhaust manifolds. The Mo addition
displays a remarkable effect in improving
oxidation resistance and high temperature
strength. The Si addition is effective in
improving oxidation resistance, but was found
to have virtually no effect in improving high
temperature strength. Based on these findings,
a new Mo-added ferritic stainless steel with
excellent heat resistance and formability
was developed. The new steel, JFE-MH1 (15%Cr-0.3%Si-0.5%Nb-1.6%Mo),
possesses the combined advantages of two existing
steels (high formability type and high heat-resistant
type). Specifically, JFE-MH1 steel sheets
and ERW tubes show formability equal to the
values of the existing high formability stainless
steel, JFE429EX (15%Cr-0.9%Si-0.5%Nb), and
high temperature strength, high temperature
fatigue properties, and thermal fatigue properties
superior to those of the existing high heat-resistant
stainless steel JFE434LN2 (SUS444: 19%Cr-0.3%Si-0.3%Nb-1.9%Mo).
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