Materials designation 121-S24B 1

[kclim]

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

 

[kenvlach]

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

 

[kenvlach]

If JIS G 5121 ‘CORROSION-RESISTANT CAST STEELS FOR GENERAL APPLICATIONS’ is what you want, an English language version is available for $65 from Techstreet:

http://www.techstreet.com/cgi-bin/detail?product_id=55402

The latest revision (06/20/03), in Japanese, is available for $29 from Global:

http://global.ihs.com/doc_detail.cf...60611&input_doc_number=g5121&input_doc_title=

 

[kclim]

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

 

[kenvlach]

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.