Metal treatment – Stock – Ferrous
Patent
1992-04-01
1993-03-23
Yee, Deborah
Metal treatment
Stock
Ferrous
148327, C22C 3844, C22C 3850
Patent
active
051960737
ABSTRACT:
A stainless steel having a two-phase structure of austenite and ferrite, the steel consisting essentially of in weight-% not more than 0.03% C, not more than 0.03% N, the total amount of C+N not being more than 0.05%, 1.5-2.5% Si, 0.5-2% Mn, not more than 0.03% P, not more than 0.010% S, 22-26% Cr, 8-11% Ni, 2-3% Mo, 0.35-0.55% Ti, % Cr+3.3.times.% Mo being at least 29.0, balance iron and impurities, said steel having been subjected to a heat treatment consisting of solution annealing in the temperature range 1100.degree.-1250.degree. C. and water quenching followed by aging in a temperature range 500.degree.-600.degree. C. for at least 30 min, wherein precipitates consisting essentially of Ni.sub.16 Ti.sub.6 Si.sub.7, so called G-phase, are precipitated in the form of particles evenly distibuted in the ferrite, said particles typically having a size of 10-50 .ANG., imparting the material an improved yield srength in the annealed and aged condition, said yield strength amounting to at least 800 MPa in combination with a Charpy V impact strength of at least 25 J, a critical pitting temperature (CPT) higher than about 50.degree. C. in 3% NaCl-solution at 200 mV SCE, and a pitting potential Ep in 0.1N-NaCl-solution, 80.degree. C., of at least about 300 mV SCE.
REFERENCES:
patent: 3717455 (1973-02-01), Hede et al.
patent: 3929520 (1975-12-01), Hellner et al.
patent: 4353755 (1982-10-01), Solomon
patent: 4793875 (1988-12-01), Larson
Liljas Mats
Pleva Jaroslav
Stenvall Peter
Avesta Aktiebolag
Yee Deborah
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