Steel designation

[simal]

I have recently seen German documentation containing the material designation of '1.7784.5'. The item in question is a high tensile steel bolt. Can someone tell me what designation system this is and where I might find it's material properties on the internet?

 

[TVP]

I found a listing for grade 1.7784 in the reference book Stahlschlüssel. It appears to be an aerospace grade alloy steel, but no standard or specification was provided. The composition is as follows:

C = 0.38-0.43
Si = 0.80-1.00
Mn = 0.20-0.40
P = 0.015 max
S = 0.010 max
Cr = 4.75-5.25
Mo = 1.20-1.40
V = 0.40-0.60

 

[diamondjim]

Looks similar to a 40CrMo Steel
with high Si values. In the
Stahlschlüssel it probably has
the mechanical properties in one
of the sections or equivalent steel
designation.