Austenitic steels with designations 1.4301 and 1.4307 are the commonest stainless types and contain about 18% chromium and 9% nickel. The difference between the two grades is that in 1.4301, the maximum allowed carbon content is higher than for 1.4307 which can mean that 1.4301 has marginally higher strength. In practice, the difference in carbon between 1.4301 and 1.4307 is often of little significance. However, if welding is to be performed, 1.4307 is the preferred alternative since corrosion resistance in the vicinity of the weld could be impaired for 1.4301.
Ground round bars in 1.4301/1.4307 are standardised in EN 10088-3. This standard covers cold-finished round bars with diameters up to 250 mm even though it is normally only smaller dimensions that are available in ground execution. Tibnor’s programme encompasses diameters up to and including 50 mm.
Grades 1.4301 and 1.4307 show good resistance to corrosion in neutral water both indoors and outdoors. The steels also exhibit immunity from atmospheric corrosion. However, these stainless grades are less suitable if the environment is acidic or contains chlorides. In such instances, higher alloyed grades will be needed.
Ground bars of 1.4301 and 1.4307 exhibit good cold formability and in the event that such is needed, excellent weldability. Austenitic stainless grades like 1.4301 and 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, the sulphur-alloyed austenitic grade 1.4305 could constitute a better alternative.
The surface finish of ground bars of 1.4301/1.4307 as stocked is 2G as defined in EN 10088-3. Grinding is carried after hot-rolled bars have been annealed, pickled as needed and the surface pre-processed through either cold drawing or peeling. Any remaining surface defects are eliminated. The diameter tolerance of ground bars is h9 as stipulated in ISO 286 - 2 which is a zero-minus tolerance. In other words, the actual diameter is marginally less than the nominal one. In addition, ground bars of stainless steel are very straight (height of arc less than 0.001 x length) with fine surface (Ra <1µm).