The austenitic steel designated 1.4307 belongs to the commonest stainless-steel type containing about 18% chromium and 9% nickel. The carbon content is low, at most 0.03%, which means that the risk for corrosive attack in the vicinity of welds is minimised.
In hollow-bar format, 1.4307 is standardised in EN 10297-2. Tibnor’s programme covers tubes with outside diameters in the range 32-140 mm and inside diameters between 16 and 90 mm. The tubes are manufactured by hot rolling in a tube mil or by hot extrusion. The hot-formed tubes are then finished by annealing and pickling.
Grade 1.4307 exhibits good resistance to corrosion in neutral water both indoors and outdoors. The steel is also fairly immune to atmospheric corrosion. However, the material is less suitable if the environment is acidic or contains chlorides. In such instances, higher alloyed grades will be needed.
1.4307 is characterised by excellent formability and weldability so that if needed, welding or cold-forming are seldom an issue. On the other hand, austenitic stainless grades like 1.4307 are generally troublesome to machine but working is facilitated through bespoke tooling. If good machinability is an important consideration for the application at hand, variants of 1.4307 are available for which the steel has been metallurgically treated for improved machinability.
Hollow bars on offer in grade 1.4307 have after hot forming been annealed and pickled. The surface finish, designated HFD in EN 10297-2, is metallically clean without oxide but some minor imperfections from hot forming can remain. The tolerances on outer diameter (D) and wall thickness (T) are stipulated in detail in EN 10297-2 and EN-ISO 1127 but are at most ±1.5% of D and ±15% for T. Straightness is good with the allowed height of arc at most 0.002 times length.