Debasis The steel is first annealed, at %7E820 %C2°C for 15-30 minutes for thin sections and for 1 hour per 25 mm thickness for heavy sections, to ensure formation of a fully austenitized structure. This is followed by air cooling to room temperature to form a soft, heavily dislocated iron-nickel lath (untwinned) martensite (hence the "mar-" in mar-aging). Subsequent aging (precipitation hardening) of the more common commercially used alloys for %7E3 hours in 480-500 %C2°C range produces a fine dispersion of Ni3(X,Y) intermetallic phases along dislocations left by martensitic transformation, where X and Y are solute elements added for such precipitation, eg; Mo, Ti, Al, Cu, Si. Newer compositions of maraging steels have revealed other intermetallic stoichiometries and crystallographic relationships with the parent martensite, including rhombohedral and massive complex Ni50(X,Y,Z)50 - usually simplified to Ni50M50. Overaging leads to a reduction in stability of the primary, metastable, coherent precipitates, leading to their dissolution and replacement with semi-coherent Laves phases such as Fe2Ni/Fe2Mo. Further excessive heat-treatment brings about the decomposition of the martensite and reversion to austenite. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Nov 4, 2007 E-mail: nishi@vsnl.com >It has been seen that Maraging Steel are subjected to 48o >deg. C artificial aging from 3 - 12 hours to gain the >fullest hardness, strength and other mechanical attributes >for its end use. Though this category of steel is of very >low carbon steel and its martensite is practically carbon >free, the strength and hardness is basically driven by >precipitation of Ni3Mo and Ti3Mo in Mart Matrix . > >Q1. If by any chance this steel went above 815C ( say 850C ) > for a shift whether all the ppts will go back to solution ? >and then is it reqd. to re-age the item ?