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Abstract

Process for manufacturing a pressure vessel intended to work under pressure between -40.degree. C. and 200.degree. C. in the presence of H.sub.2 S under conditions defined by the NACE MR 0175-97 standard, in which: components of the vessel are manufactured from a steel of chemical composition: 0.03%.ltoreq.C.ltoreq.0.15%; 0%.ltoreq.Si.ltoreq.0.5%; 0.4%.ltoreq.Mn.ltoreq.2.5%; 0.5%.ltoreq.Ni.ltoreq.3%; 0%.ltoreq.Cr.ltoreq.1%; 0%.ltoreq.Mo.ltoreq.0.5%; 0%.ltoreq.Al.ltoreq.0.070%; 0%.ltoreq.Ti.ltoreq.0.04%; 0%.ltoreq.B.ltoreq.0.004%; 0%.ltoreq.V.ltoreq.0.02%; 0%.ltoreq.Nb.ltoreq.0.05%; Cu.ltoreq.1%; S.ltoreq.0.015%; P.ltoreq.0.03%; the balance being iron and impurities resulting from the smelting operation; CET=C+(Mn+Mo)/10+(Cr+Cu)/20+Ni/40<0.35; 800/500 cct<10 s; the components being quenched and tempered; the structure is martensitic or martensitic-bainitic with less than 10% ferrite; the temper temperature is <680.degree. C. Optionally, a stress-relieving operation is carried out at a temperature .gtoreq.595.degree. C. The components are welded under conditions such that the cooling time tc between 800.degree. C. and 500.degree. C. of the HAZ is >5 seconds and a postweld heat treatment is carried out between 595.degree. C. and 680.degree. C., the steel being such that R.sub.m.gtoreq.550 MPa, R.sub.e.gtoreq.450 MPa, A %.gtoreq.17%, K.sub.CV.gtoreq.40 J at -40.degree. C. and the hardness at any point on the surface of the vessel is .ltoreq.248 HV. Vessel obtained and steel.

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First Claim