# What does the D stand for in the steel grade 16MND5

I would like to know what does the "D" means in steel grade 16MND5.

According to the standard EN 10027:

16 means 0.16 % C MN 5 means 1.25 % Mn (5 must be divided by 4 to get the Mn mass fraction)

But nothing is specified for D.

• I think it follows the French AFNOR standard, not EN according to p30 here publikationen.bibliothek.kit.edu/270046849/3813880 . Jan 22, 2019 at 13:45
• The "Internationaler Stahlvergleich" suggests that D is used in Chinese/Russian steel names. For example, 16MnDR is equivalent to Material No. 1.0570. The closest ISO code I could find to 16MnD5 was 16MnCr5 (material no. 1.7131). Jan 22, 2019 at 22:14
• ccsteels.com/Structural_steel/2305.html is a datasheet from a chinese company. could D mean Mo?
– mart
Jul 1, 2021 at 20:38

This (Table 1, page 4) gives the composition of 16MND5-A508 as

> C     S     P     Mn   Si   Ni  Cr   Mo   V Cu Co Al N
> 0.159 0.008 0.005 1.37 0.24 0.7 0.17 0.5  <0.1
> Weight % - iron balance.


A508 is the relevant ASTM standards document (not a free publication.)

• It is not ASTM A508 unless is is marked and certified as A508. Oct 19, 2019 at 21:35
• Apparently forging stock likely to be used with ASTM A302, " carbon - 1/2 Mo" . Common pressure vessel steel for use at high temperatures , probably in hydrogen service ( reformers). Oct 29, 2021 at 14:40