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Materials designation 121-S24B

Materials designation 121-S24B

Materials designation 121-S24B

(OP)
Hello all,

Recently found a materials spec on a Toshiba drawing for a steam turbine casing:

121-S24B

There was no other accompanying information. I suspect it may be related to a Japanese industrial standard (JIS), although I haven't turned up much going down that path.

Based on other casing materials, it is suspected to be a low alloy steel casting (or possibly forging).

Does anyone have any ideas what exactly the designation refers to?

TIA

RE: Materials designation 121-S24B

I found a stainless steel casting alloy of similar designation which seems suitable for this application.  Information from http://www.metalinfo.com (A free sample search is offered as an inducement to subscribe to their annual service).

Society                JIS
Standard             G5121
Grade                 SCS24
Revision             1991-03-01
Ferrous/Nonfer     F
Type of Metal       steel, stainless steel
Other name         ASTM CB7Cu-1, ACI CB7Cu

Partial Chemical Composition:   
 Element        Symbol       Max. %    
  Carbon          C           0.07           
  Manganese   Mn        1.00           
  Silicon           Si         1.00           
  Phosphorus    P          0.04           
  Sulfur            S           0.04           
  Iron             Fe          78.85          
  Chromium    Cr         17.50          
  Copper          Cu          4.00           
  Nickel            Ni           5.00               
  Niobium        Nb          0.45  
Note: Wt.%, Min. available for paid subscribers.

Hope this helps,
Ken

RE: Materials designation 121-S24B

(OP)
Gotta give you a star for the website and the mad search skillz :)

The steel you've described looks like an austenitic of sorts...

but (from what I've been told from people on site, haven't actually seen it myself yet) the casing is magnetic. Also, the casing is huge, and isn't really exposed to corrosive conditions - so it probably isn't a stainless on a cost/performance basis.

On past experience, we'd expect the material to be a low alloy (Cr Mo) steel - but then again, this could be completely different.

Thanks for the heads up Kenvlach

RE: Materials designation 121-S24B

It should be somewhat magnetic -- the composition is similar to S17400 (17-4PH), a precipitation hardening, martensitic SS.
Besides resistance to corrosion/oxidation, the alloying gives high temperature creep resistance.

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