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12.1.1 Technical Information
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Material Specifications
Subject to availability a wide
range of standard items are
normally available in grades A2
and A4 stainless steel. As these
are the most popular grades we
give below some information
about these two types of
stainless, together with some
typical applications.
All the information is given for
basic guidance only. If the
application is of a critical nature
or has stringent specifications,
independent advice should be
sought to ensure that the correct
grades are specified.
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Grade A2 (AISI 304)
Grade A2 is an Austenitic grade of
stainless steel. It has excellent
resistance to atmospheric corrosion
except in severe industrial and marine
environments. Oxidation resistance is
satisfactory for use up to 850ºC.
Resistance to nitric acid and other
oxidising chemicals is excellent.
Resistance to other mineral and organic
acids is good within certain limits of
temperature and concentration.
Generally unsuitable for solutions of
hydrochloric acid and chlorides,
particularly if evaporation at high
temperatures can occur.
Additional Special Features:
This grade can be described as non-
magnetic except when heavily cold
worked. It is not hardenable by heat
treatment, but is greatly strengthened
by cold working. Special coatings can
be applied to prevent thread seizure at
high temperatures. High strength and
toughness at sub- zero temperatures
down to minus 250ºC. Significant stress
relaxation above 575ºC.
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Grade A4 (AISI 316)
Grade A4 is an Austentic grade of
stainless steel. It has a higher corrosion
resistance than A2 grade in many
chemical environments, including contact
with dilute sulphuric acid, and acetic
acid over a wide range of temperature
and concentration. Resistance to
atmospheric staining and pitting in
industrial and urban areas, and also is
suitable for marine conditions - not
immersed in sea water.
Additional Special Features:
As in Grade A2 above except:-
Satisfactory oxidation resistance up to
800ºC. Significant stress relaxation
above 600ºC.
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Typical Applications
Grade A2
Civil and chemical engineering
projects. Food processing, medical
and brewing equipment and many
types of domestic appliances. As
fasteners for aluminium alloy,
plastic coated steel assemblies.
Cryogenic equipment, special
purpose building and masonry
fixings.
Grade A4
Fasteners for boat deck fittings,
chemical plant, swimming pools
and dye vats. Fertiliser, rayon
and sewage treatment plants.
Dairy equipment. Medical
sterilising equipment. Special
purpose building and masonry
fixings.
Fasteners are available on request
in many other corrosion resistant
materials. Contact us with your
enquiries for availability and
technical details.
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