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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.

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.

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.

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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