The austenitic steel with designation 1.4404 contains molybdenum in addition to chromium and nickel. The difference against 1.4301/1.4307 apart from the presence of molybdenum is that the nickel content is greater. This type of stainless steel is often referred to as acid resistant which is to some degree a misnomer since the material resists attack only by weak acids. 1.4404 has low carbon content which means that it can be welded without risking impairment of corrosion resistance in the vicinity of the weld. In terms of strength, 1.4404 is more or less equivalent to the lower alloyed grades 1.4301/1.4307.
Machined round bars in 1.4404 are standardised in EN 10088-3. This standard covers cold-finished round bars with diameters up to 250 mm. Tibnor’s programme is more extensive and encompasses diameters up to and including 300 mm.
The presence of molybdenum along with chromium renders 1.4404 resistant to corrosion in weak acids and water containing chlorides so long as the chloride concentration is not too high; an example of an environment where the steel works well is salt-laden coastal atmosphere.
Machined bars of 1.4404 are relatively easy to cold form and, in the event that it is required, weldability is excellent. Austenitic stainless grades like 1.4404 are generally troublesome to machine but working is facilitated through bespoke tooling.
The surface finish of machined 1.4404 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 or k13 as stipulated in ISO 286 - 2 which are zero-plus tolerances. 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.