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RA 253 MA®
RA 253 MA® ESPECIFICAÇÕES TÉCNICAS
RA 253 MA® is a lean austenitic heat resistant alloy with high strength and outstanding oxidation resistance. RA 253 MA obtains its heat resistant properties by advanced control of microalloying additions. The use of rare earth metals in combination with silicon gives superior oxidation resistance to 2000°F. Nitrogen, carbon and to some extent, rare earth and alkali metal oxides, combine to provide creep rupture strength comparable to the nickel base alloys. RA 253 MA has only fair resistance to carburization. 309 is somewhat better in this respect. Austenite stability in RA 253 MA is enhanced by the nitrogen addition, so that formation of embrittling sigma phase is retarded.
RA 253 MA is welded using matching composition RA 253 MA AC/DC covered electrodes, fluxcored and bare wire. GMAW shielding gas may be 100% argon. Improved wetting and bead contour may be had with a mix of 80% minimum argon, 18% maximum helium and 2% maximum CO2. For shortcircuiting arc transfer 68% Ar 30% He 2% CO2 has been satisfactory.
Chemical Composition, %