All austenitic stainless steel fasteners are normally non-magnetic in the annealed condition. Cold working (normally drawing) procedures enhanced levels of tensile strength.
These grades cannot be hardened by thermal treatment. Heat Treatment is by solution annealing – heated to 1010-1120✬ and cooled rapidly.
The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures. Grade 304 is considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60✬. Grade 304 is excellent in a wide range of atmospheric environments and many corrosive media, although it is subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60✬. 304H will become sensitized in the temperature range of 425-860✬ this is not a problem for high temperature applications, but will result in reduced aqueous corrosion resistance. Grade 304L is more resistant to carbide precipitation and can be heated into the above temperature range. Continuous use of 304 in the 425-860✬ range is not recommended if subsequent aqueous corrosion resistance is important. Good oxidation resistance in temperatures up to 870✬. Grade 304H with its higher carbon content finds application at elevated temperatures. Grade 304L, the low carbon version of 304, does not require post-weld annealing and so is extensively used in heavy gauge components (over about 6 mm). The balanced austenitic structure of Grade 304 enables it to be severely deep drawn without intermediate annealing Grade 304 also has outstanding welding characteristics. It has excellent forming and welding characteristics.
Grade 304 is the standard “18/8” stainless it is the most versatile and most widely used stainless steel. Please enquire as to properties required. We can also produce flats and squares not covered by the standard, on request, to reduce machining costs (up to 101.6 mm (“4”) square and flats to 100 mm x 50 mm (4” x 2”]). We stock round bar from 10 mm to 60 mm diameter, and hexagons from 10 mm to 37 mm AF. Therefore, A2-70 is an austenitic, acid proof stainless grade (usually 304 material – 304 or 304L) which has been cold worked to provide a minimum tensile strength of 700N/mm² (MPa). The “70” denotes the minimum tensile strength to be met by the material (actually the bolt, screw or nut after manufacture).
DIN 267 PART 11 FULL
The designation A4-80 derives from “A” meaning the material is a cold worked austenitic stainless, divided into 5 grades (1-5) according to material characteristics (see Annex B of DIN ES ISO 3506-1: 1997 for full description of each grade). Material to meet the properties of A2-70 is one element of our product range. Midland Bright Steels supplies a range of material that enable fastener manufacturers and others to produce products that meet or exceed the properties required in the above standard. DIN ES ISO 3506-1: 1997 specifies the mechanical properties of bolts, screws and nuts made of austenitic (amongst others) stainless steels, when tested over an ambient temperature range of 15✬ to 25✬.
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