| Tokyo,
June 4, 2003 - JFE Steel Corporation announced
today that it has developed a ferritic stainless
steel, "JFE-SX1," 1)
with the corrosion resistance and formability
required for automobile fuel tanks and other
fuel system applications.
The new ferritic stainless steel has demonstrated
sufficient corrosion resistance for fuel tank
materials in the common external corrosion
tests (15-year/150,000-mile durability) performed
by the American Iron and Steel Institute (AISI)
in conjunction with the Strategic Alliance
for Steel Fuel Tanks (SASFT)2)
for the selection of steel materials used
in fuel tanks.
In February 2003, the SASFT common corrosion
test results and a prototype fuel tank (see
photograph) produced with JFE-SX1 for display
purposes by Horie Metal Co. were presented
at two international conferences held in Detroit.
This was the first time that this new fuel
tank material was displayed to the public,
and the prototype fuel tank generated wide
interest from automakers and parts manufacturers.
Terne (lead-tin) plated steel sheets have
been widely used for conventional automobile
fuel tanks, but automakers are moving away
from lead and similar materials because of
stiffer environmental regulations. Several
alternatives have been suggested, including
plastics and steels (Al plated, Sn-Zn plated,
stainless), but none of these materials have
so far demonstrated the ability to meet increasingly
strict environmental regulations, such as
the standards and requirements of California's
Air Resources Board (CARB). This has raised
the need for a common test that can provide
objective evaluations of material suitability.
SASFT was formed in 2001 to address this need
by providing empirical evaluations of steel
materials for potential use in fuel tanks.
JFE Steel has been a leading advocate and
developer of ferritic stainless steel for
use in fuel tanks. Unlike plastic tanks, ferritic
stainless steel does not pose a risk of fuel
emission and it is easily recyclable.
Ferritic stainless steel also offers advantages
for other aspects of the fuel system:
| 1) |
Potential elimination or
simplification of coating processes due to
the excellent corrosion resistance of stainless
steel |
| 2) |
Ability to clear regulations
on fuel emission and materials recycling. |
JFE Steel selected ferritic
stainless steel rather than austenitic stainless
steel (i.e. SUS 304) because of concerns about
stress corrosion cracking3).
JFE-SX1 was specifically
selected for further development because its
corrosion-resistant performance is closer
than any other ferritic stainless steel to
the performance of SUS 304. JFE-SX1 is the
only ferritic stainless steel entered
in AISI's SASFT program. Testing demonstrated
that JFE-SX1 with a simple coat had adequate
external corrosion resistance to assure 15-year/150,000-mile
durability. Testing consisted of the compound
cyclic corrosion test (SAE J2334) and the
salt spray test (ASTM B117).
A fuel tank requires, not
only corrosion resistance, but also press
formability.
Because fuel tanks are fabricated into extremely
complex and irregularly contoured shapes in
order to achieve maximum volume for the space
available within the automobile. Research
at JFE Steel successfully raised JFE-SX1's
r-value (Lankford value)4)
to more than 2.3 (0.8mmt), which
represents an extraordinary improvement. The
r-value is an index of the deep drawability
of steel.
JFE Steel is now developing
technology to commercialize JFE-SX1 as its
No.1 product in ferritic stainless
steel, which combines the corrosion resistance
and formability required by fuel tanks and
fuel system parts.
| Notes: |
| 1) |
"JFE-SX1" is the
new name of "RSX-1," changed to
coincide with the change in company name to
JFE. |
| 2) |
SASFT: An alliance of automakers
and manufacturers of parts, coatings and materials
from around the world organized by AISI. The
alliance's main objective is to select steel
fuel tank materials that meet California's
Air Resources Board (CARB) standards. Activities
began in 2001, with corrosion test results
announced at two international conferences
held in Detroit in February 2003. |
| 3) |
Stress Corrosion Cracking
(SCC): A phenomenon in which metals crack
and fracture under stress load. The most common
examples come from corrosion in salty environments.
From a practical standpoint, this is the most
problematic destructive phenomenon that stainless
steel experiences. |
| 4) |
r-value: The ratio
of width strain to thickness strain on a steel
sheet deformed by tensile stress. The larger
the value, the larger the decline in width
against the decline in thickness. This restrains
fracture and loss of strength in deep drawing,
and enhances formability and deep drawability. |
Prototype fuel tank (laser-welded,
700mm x 500mm x 120mm)
displayed at international conferences
in Detroit
Produced by Horie Metal Co.
Material: JFE-SX1 (18Cr-1.45Mo-Ti) |
|
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