Venik wrote in message ...
Wolfhenson wrote:

Any steel
containing 5% nickel or more is considered to be resistant to
atmospheric corrosion in addition most nickel steels contain chromium
in similar quantity as nickel and that is another element that makes
the steel stainless.

Let's stick to technical definitions: stainless steel is a ferrous alloy
with a minimum of 10.5% chromium content. Major elements of the MiG-25
were made of appoximately 80% of VNS-2, VNS-4, and VNS-5 alloys, 11%
D-19T aluminum alloy and 8% OT4-1 titanium alloy, none of which falls
under this definition.

The steels used by Russian aircraft makers would probably be more
correctly described as corrosion resistant austinitic steels.
Stainless Steel AFAIKS is only one type of austinitic steel.

Steel, Titanium, Aluminium all have approximetly the same tensile
strength per unit weight. Aluminium being less dense than steel is
weaker for the same cross sectional area and more must be used. For
some structures of an aircraft that are under compressive forces the
thicker guages of Aluminium used provides superior stiffness and
resistence to buckling although tensile strength is the same.

Steel is a perfectly good material for highly concentrated stressed
components such as the wing, spars and tail. In these areas Aluminium
looses its advantage. Aluminium is good for Most parts of the
fueselage where stresses are less concentrated.

Titanium falls in between Aluminium and Steel in Density and Heat
resistence.

Steel has superior thermal resistence than Titanium and Titanium
better than Aluminium. The use of corrosion resitent steels on many
parts of Russian aircraft may have more to do with resistence to
atmopsheric corrosion due to moisture than that due to high
temperature oxidation.

Steel most defintely is not an inferior material to Titanium: in many
cases it is superior in physical properties. It all depends on what
the objective is.