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Stainless steel: composition of stainless steel fibers

AISI 316L, AISI 601, 302, 304 stainless steel fibers

Metallic fibers chemical composition

The most common: AISI 316L (norme EN 14404)family of austenitic. Here are the compositions of the fibers of AISI 316L, and of AISI 601 (Inconel), compared to others, like stainless steel AISI 304 (EN 1.4301):

TIBTECH innovations logo Type Carbone C Manganese Mn Silicium Si Phosphate P Sulfur S Nickel Ni Chromium Cr Molybdenum Mo Steel Fe
AISI 316L EN1.4404 austénitique 0.03 max 2.00 max 1.00 max 0.045 max 0.03 max 12,5 / 14 17 - 18 2,5 - 3 remaining
AISI 601 - type Inconel - - - - - - 61 24 al : 1 14
AISI 302 EN1.4310 austénitique 0,05-0.15 max 2.00 max 1.00 max 0.045 max 0.015 max 8/9,5 16/18 0,8 max remaining
AISI 304 EN1.4301 austénitique 0.07 max 2.00 max 1.00 max 0.045 max 0.03 max 8/10,5 18/19,5 - remaining
AISI 330Nb EN1.4887 ferritique 0.15 max 2.00 max 1 à 2 0.015 max 0.015 max 33/37 20/23 Nb 1 - 1,5 remaining
AISI 630 EN1.4542 martensitique 0.07 max 1.00 max 0.7 max 0.04 0.03 max 3 - 5 15/17 0,6 max remaining
AISI 904L EN1.4539 austénitique 0.02 max 2 max 0.7 max 0,03 max 0,01 24-26 19-21 4-5 remaining
Fe Cr Al - FeCrAlloy Fer.Chrome.Alu 0.03 0,19 0.21 0,01 cu 0,05 - 20,50 al 5.5 remaining

High temperature resistance: ex: FECRALLOY, AISI 330nb, 601 ... and 316L

The special alloys or stainless steel fiber performances at very high temperatures depend mainly on their Nickel and Chromium content, and to a lesser extent to Molybdenum or other rare earth. One key parameter is the creation of protective oxides on the fiber surface thanks to some catalytic components. That's why, for instance:
  • The alloy AISI 601 has one of the best performances in very high temperature environment thanks to its high Nickel content nickel.
  • Types of alloys such as ferritic can also have good resistance to oxidation in high temperature thanks to their high content of chrome, sometimes reinforced with rare earth or catalyst such as niobium, for example the AISI 330nb.
  • The "steel chromium aluminium" or FeCrAlloy, are also very interesting for gas burners membrane or catalytic applications.
Note: these high performance metallic fibers have their flexibility or processability properties lowered.
To simplify: the highest are the percentages of nickel, chromium or aluminium, the better is oxidation resistance, ... BUT... the stiffer and more fragile the material becomes. This means, in flexible structures, that the best compromise between performance and long term flexibility must be found. That's why the well known AISI 316L still has a promising future!

Fiber diameters and other parameters

It is expressed by the value of diameter unit fibers in micrometres, or « micronage ». We work mainly with 3 standard diameters: 8µ, 12µ et 22µ. The most usual diameters range from 6 to 30 micrometres. Characteristics of the 316L fibers:
Fiber diameters (µm) Electric resistivity (Ω/cm) Tenacity (cN) Elongation
8 170 7 – 8 1%
12 80 17 – 18 1%
22 30 55 – 60 1%
Please note that the tenacity and elongation at break depend very much on the production process: hard drawn or semi-annealed ratio. It also depends on the fiber cross section geometry and on potential weakness points due to crimping or other equivalent processes. That's why fibers can be much more fragile or brittle which may sometimes lead to micro fragmentation that could be dangerous in specific applications « fragile »). Other stainless steel alloys can also be used, especially the ones with more nickel which have an even better high temperature resistance: e.g. the family of AISI 601 ou 845. The product line of steel chromium aluminium, sometimes called FeCrAlloy, is also characterized by its high temperature resistance, but also has drawbacks in terms of rigidity and fragility of the fiber at specific conditions.

Fractal fibers

For fiber types « fractale », which means a surface with many micro and nano-cavities which hold a great quantity of air within the structure. We can measure a theoretical diameter corresponding to the equivalent of a conventional circular section of the same quantity of stainless steel fibers per meter. Another approach is to measure the mean root square diameter « DRCM » well known in the wool industry.

Note : The concept of fractale fibers has been developed by Mr Tiberghien in 2004 when he was working for UGITECH. An article in the Chemical Fibers International paper was published, followed by a conference in Dornbirn.

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fibres fractales

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