Austenitic, non-magnetic, stainless steel alloy and articles mad

Alloys or metallic compositions – Ferrous – Nine percent or more chromium containing

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420 59, C22C 3844

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053085779

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BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to an austenitic, non-magnetic, stainless steel alloy and articles made therefrom and, more particularly, to such an alloy which, when significantly warm-worked but not subsequently annealed, has an outstanding combination of non-magnetic behavior, high yield strength, and good corrosion resistance, particularly resistance to chloride stress corrosion cracking.
Chromium-manganese stainless steel alloys are used in the manufacture of oilwell drilling equipment, including certain kinds of drill collars and housings for measurement-while-drilling (MWD) assemblies. More specifically, modern deep-well drilling methods, including directional drilling, require close monitoring of the location of the borehole to minimize deviations from the desired course. This may be accomplished by incorporating electrical measuring equipment in certain drill collar sections. However, since such measurements are disturbed by magnetic behavior, those drill collars containing such equipment must be non-magnetic, meaning here and throughout this application, having a relative magnetic permeability of less than about 1.02. Also, drill collars and other such articles are required to have high strength, particularly, a room temperature 0.2% offset yield strength of at least about 100 ksi. Chromium-manganese stainless steels have been favored in the manufacture of such articles because they satisfy both of these requirements at reasonable cost.
The following are hitherto known chromium-manganese stainless steel alloys, the compositions of which are listed in Table I: UNS S28200; UNS S21300; the experimental alloy described in V. Cihal and P. Pohoril, "Austenitic chromium-Manganese Steels Resistant to SCC in Concentrated Chloride Solutions" in Stress Corrosion Cracking and Hydrogen Embrittlement of Iron Base Alloys, 1170-1182, NACE (1977), identified here as Heat No. 7412; U.S. Pat. No. 3,075,839, issued to E. J. Dulis et al. on Jan. 29, 1963; U.S. Pat. No. 3,112,195, issued to H. Souresny on Nov. 26, 1963; U.S. Pat. No. 3,904,401, issued to D. L. Mertz et al. on Sep. 9, 1975 (UNS S28200 and UNS S21300 are both exemplary alloys of this patent); U.S. Pat. No. 4,514,236, issued to W. T. Cook et al. on Apr. 30, 1985; U.S. Pat. No. 4,523,951, issued to R. J. Andreini et al. on Jun. 18, 1985; Duvall XM-19H; and U.S. Pat. No. 4,481,033, issued to K. Fujiwara et al. on Nov. 6, 1984. The foregoing alloys suffer from one or more deficiencies. For example, UNS S28200 and UNS S21300 (representative of the 3,904,401 patent) have less than desirable stress corrosion cracking (SCC) resistance. The alloy described by Cihal et al. contains excessive amounts of ferrite, causing undesirable magnetic behavior. Further, the balance of elements in these alloys reflects a lack of recognition of the important relationship between the manganese and the nickel plus copper contents of the alloy on the one hand, and the chromium plus molybdenum contents on the other hand, in ensuring good resistance to SCC in chromium-manganese stainless steel alloys.
Recent developments in deep-well drilling methods have placed more stringent demands on parts such as drill collars.


TABLE III __________________________________________________________________________ w/o Ex/Ht Cr + Mo - 14.6 No. C Mn Si Cr Ni Mo Cu N Ni + 2 Cu Cr + Mo 1.5 Fe __________________________________________________________________________ 1* 0.052 17.46 0.45 17.56 0.99 1.06 0.06 0.48 1.11 18.62 2.68 Bal. 2* 0.049 17.38 0.48 17.42 0.99 1.04 0.06 0.50 1.11 18.46 2.57 Bal. 3 0.036 15.13 0.39 14.79 0.23 1.48 0.24 0.31 0.71 16.27 1.11 Bal. 4 0.021 14.89 0.41 15.09 <0.01 0.98 <0.01 0.35 <0.01 16.07 0.98 Bal. 5 0.024 14.93 0.43 13.92 <0.01 1.92 <0.01 0.35 <0.01 15.84 0.83 Bal. 6 0.039 14.74 0.37 14.74 <0.01 1.50 <0.01 0.31 <0.01 16.24 1.09 Bal. 7 0.038 13.18 0.37 14.68 <0.01 1.49 <0.01 0.29 &

REFERENCES:
patent: 4822556 (1989-04-01), Cordea et al.
patent: 4957700 (1990-09-01), Honkura et al.
patent: 5094812 (1992-05-01), Dulmaine et al.

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