Duplex Round Bar Peeled
1.4460 is a duplex stainless steel which implies that its microstructure consists of ferrite and austenite in approximately equal proportions. The steel contains more chromium (≈26%) and less nickel (≈6%) than the austenitic types, 1.4301 and 1.4307. In addition, it is alloyed with molybdenum (1.5%) and nitrogen. Like the austenitic grade 1.4404, 1.4460 is classed as “acid-resistant” which is in reality true only for weak acids. Apart from good resistance to corrosion, duplex grades exhibit relatively high strength and, in particular, yield strength is about doubled in comparison with austenitic steels having the same resistance to corrosive attack.
Machined (peeled) round bars in 1.4460 are standardised in EN 10088-3. This standard covers cold-finished round bars with diameters up to 160 mm. However, Tibnor’s programme is even more extensive and encompasses diameters up to and including 244 mm.
Duplex steels like 1.4460 are characterised by very good resistance to corrosion even in aggressive environments containing chlorides, e.g. sea water. A significant advantage over austenitic grades like 1.4404 is a reduced sensitivity to failure as a result of stress corrosion and corrosion fatigue in the presence of chlorides. The favourable corrosion properties in combination with higher strength make 1.4460 an attractive alternative for machine components exposed to corrosive environments such as pump parts working in contact with aggressive liquids and in the energy segment (water power, offshore).
Machined bars in 1.4460 are quite easy to cold form but cold formability is not as good as for austenitic grades. In the event that such is needed, weldability is good. Duplex stainless steels are somewhat easier to machine than austenitic types but working is always facilitated through bespoke tooling.
The surface finish of machined 1.4460 as stocked is 2B as defined in EN 10088-3. Machining, usually peeling, is carried after hot-rolled bars have been annealed; machining marks are evened out by the burnishing action of subsequent straightening. This procedure eliminates any remaining surface defects. The diameter tolerance of machined bars is k12 as stipulated in ISO 286 - 2 which is a zero-plus tolerance. In other words, the actual diameter is marginally larger than the nominal one. In addition, machined bars of stainless steel are rather straight with height of arc less than 0.001 x length.