HIGH-STRENGTH MARTENSITIC STAINLESS STEEL WITH EXCELLENT RESISTANCES TO CARBON DIOXIDE GAS CORROSION AND SULFIDE STRESS CORROSION CRACKING

摘要

The present invention provides a martensitic stainless steel in whichspecified elements in a steel composition are limited. The martensiticstainlesssteel can have high strength of 0.2% proof stress of 860 MPa or more andexcellentcarbon dioxide gas corrosion resistance and sulfide stress-corrosion crackingresistance by limiting the steel composition of specified elements anddefining Mocontent in the steel by relationships with IM values as well as by formingmicrostructure of the steel with main tempered martensite, carbideprecipitatedduring tempering, and intermetallic compounds such as a Laves phase, a a phaseand the like. As a result the martensitic stainless steels of the presentinventioncan be applied to practical steels, which can be widely used in oil well tubesand thelike under environment including carbon dioxide gas, hydrogen sulfide,chlorine ionsor two or more of them, in wide fields.