British Spec S99 convertion to AISI 3

[COKA]

Does anybody know where I can find the American Spec (AISI?) equivalence of the British Spec S99?
S99 chemistry: 0.36-0.44 C, 0.1-0.35 Si, 0.45-0.70 Mn, 0.025 P max, 0.020 S max, 0.50-0.80 Cr, 0.45-0.65 Mo, 2.30-2.80 Ni, Fe balance.
If there is no equivalent, does anybody know the embrittlement relief time and temperature of S99 as well as tensile strength?
Thank you,

Coka

 

[metengr]

COKA;
The web site below identifies the S99 as a British Standard aircraft quality EN 26 High Tensile steel (2.5% NiCrMo) supplied by Interlloy;

http://www.interlloy.com.au/data_sheets/high_tensile_steels/en26.html

The technical data sheet has all the information you need regarding mechanical properties and welding and stress relief temperature/time parameters.

 

[COKA]

Thank you, Thank you, Thank you. A star for you!

Coka

 

[TVP]

The link provided by metengr did not discuss hydrogen embrittlement relief. The time and temperature required for such relief is determined by the strength and/or hardness of the component. Presumably if you are using a VAR (Vacuum Arc Remelting) grade like S99, then this is for an aerospace application. If this is correct, then there should be a standard to which you must adhere, whether it is an internal standard from Boeing, P&W, etc., or a consensus industry standard like ASTM B 850 or SAE/USCAR-5. I can give you additional information on time and temperature if you provide some details on how the part was heat treated, how it was cleaned (acid cleaning?), and how it was suface treated (electroplating?). However, this will be based on the ASTM & SAE/USCAR standards, not any aerospace standards, so keep this in mind.

 

[COKA]

TVP,
Yes, this is for an aerospace application, and I have been trying to get more info for the past couple of days. I should be getting an answer soon. Basically what I was trying to do is to find the american equivalence for S99. EN 26 is as a matter of fact an australian alloy. By having an american equivalency, I can consult the Aerospace Structural Metals Handbook and get more information. Do you have any other ideas?

Coka

 

[TVP]

First, there is no direct US equivalent to this grade (ASTM, SAE, SAE AMS, etc.). Second, this type of steel is used in the quenched & tempered condition, which means that the final strength is highly dependent on the heat treating parameters used. One specification lists the yield strength = 1125 MPa minimum & tensile strength = 1550 MPa minimum, hardness > 444 HB. However, this grade can be hardened in excess of these requirements. At this strength level, ASTM B 850 would require embrittlement relief to be 18 hours at 190-220 C. Feel free to provide additional details on the heat treatment if you have them.