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Description of material
BIOVAL® AV177AL is a Cr-Ni-Al precipitation hardening stainless steel with moderate corrosion resistance and high strength, obtained by different kinds of heat treatments. In the annealed condition, this grade has a soft austenitic structure, with values of strength substantially close to the TP 300 series. A considerable increase of the mechanical properties as Rp, Rm and HB, is obtained by the transformation of Austenite to Martensite by cryogenic treatment (cond.R), by conditioning close to room temperature (cond.T) and by heavy cold deforming (cond. C). All these treatments must be followed by a hardening (cond. RH, TH and CH) heat treatment, at a specific temperature, maintaining a low level of distortion of pieces.
Stainless steel springs or devices where high Rm and HB and resistance corrosion better than 400 martensitic series are required.
Argon Oxygen Decarburization
The structure and chemical composition of BIOVAL® AV177AL gives about the same corrosion resistance of austenitic 300 series steels, but better than the martensitic 400 series. Depending on environments and final use, attentive evaluations should be done in terms of H-embrittlement and stress corrosion cracking.
BIOVAL® AV177AL can be cold drawn and cold headed in the annealed condition, but it’s important to know that this grade has a very high cold working hardening factor due to its rapid formation of Martensite structure.
Machining is the same as of austenitic TP 302 or TP 304 in the annealed condition, but it is very difficult after hardening due to the higher hardness of Martensite.
BIOVAL® AV177AL is weldable by the typical inert gas processes, because these methods have a protective effect on the weld metal, avoiding the loss of Aluminum. Normally, neither preheating nor post-welding heat treatments are necessary. FZ and HAZ have mechanical properties close to the base steel in the annealed condition. Obviously, solution annealing, conditioning and precipitation hardening is mandatory to obtain high strength of the weld.
BIOVAL® AV177AL could have a certain amount of Ferrite in its austenitic structure, mainly in large sections or ingots. This situation should be well considered in order to avoid cracks primed by ferrite during hot deforming or forging.