Steel names preceded with X mean it is a high alloy steel, the X itself only notifies the reader of the name that the numbers behind the composition are nominal percentages. If the name is not preceded with an X it means the numbers are modified with a multiplier. The first number before the composition is always Carbon and always has a multiplier of 100. This is done because carbon is the most common alloying element in steel and always has to be considered, without carbon all other alloying elements are less effective, if there is any useful effect at all. A steel without carbon can basically not be hardened to a usable level (and isn't considered a steel either), no matter how much Cr,Mo,Si etc. one would add.
For example: - X105CrMo17 steel has 1,05% carbon, 17% chrome content and a unspecified level of Molybdenum.
In the same system the 34CrNiMo6 steel has a nominal carbon content of 0.34%,a chrome content of 1,5%,an unspecified content of nickel and molybdenum (there is no X , so this is a low alloy steel. The chrome number has been modified by a factor 4. would there have been a X in the beginning of the name the Cr content would be 6%)
The multiplier system is confusing at first but it has its merits, mainly because it is for low alloy steels and thus it gives a name without any decimals or ridiculously large numbers. It is mainly used for alloying and corrosion purposes. It is only one of many usable systems, making the job of a materials engineering professional a bit more interesting. Many steels also have names according to the Din W-Nr(Werkstoff-Number) e.g. 1.4404 ( this would be an AISI SS316L, DIN X2CrNiMo17-12-2, UNS S31603 etc. All defining the same steel, in this case a low carbon stainless steel).
| Elements | Multiplier | |
|---|---|---|
| wt.% | Co, Cr, Mn, Ni, Si, W (High Contents) | x4 |
| wt.% | Al, Be, Cu, Mo, Nb, Pb, Ta, Ti, V, Zr (Low Contents) | x10 |
| wt.% | N, P, S, Ce (Very Low Contents) | x100 |
| wt.% | B (Trace Amounts) | x1000 |
Special Thanks For His Contributiojns To Leon Koyen
Last updated - 05/25/19