Stainless Steel Round Bar Machined EN 1.4547
1.4547 (Outokumpu 254 SMO®) is a high-alloyed austenitic steel with excellent resistance to corrosion such that it can withstand exposure to the most demanding environments such as sea water, hydrochloric acid, hydrofluoric acid and other acids containing chlorides. The steel is alloyed with 20% chromium, 18% nickel and has a very high content of molybdenum, 6%, as well as small additions of copper and nitrogen. The carbon content is very low, only 0,01%. The high alloy content together with the presence of nitrogen mean that 1.4547 is characterised by higher strength than “ordinary” austenitic grades like 1.4307 or 1.4404.
Rounds in 1.4547 are standardised in EN 10088-3. This standard covers round bars with diameters up to 160 mm. Tibnor’s programme comprises machined bars in diameters up to and including 160 mm.
1.4547 is a so-called super-austenitic steel showing very good resistance to attack from aggressive chemicals as well as a high degree of immunity to pitting and crevice corrosion in chloride-containing environments, such as sea water. Furthermore, the high nickel content promotes resistance to stress-corrosion cracking in the presence of chlorides to which lesser alloyed austenitic grades like 1.4307 and 1.4404 are prone. The material finds use in the chemical industry as well as in the marine and offshore segments. In the form of bars, 1.4547 is suitable for machine parts subjected to highly aggressive environments.
The steel is quite weldable so long as the heat input is not too high and a suitable consumable is chosen. Cold-forming operations can normally be carried out without any difficulty even though the higher base strength means that the forces needed will be higher than for 1.4307 or 1.4404. 1.4547 is difficult to machine being characterised by high forces and rapid tool wear. Machining is facilitated through the use of bespoke tooling.
The surface finish of machined 1.4547 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.