USE OF A STEEL ALLOY FOR WELL PIPES FOR PERFORATION OF BOREHOLE CASINGS, AND WELL PIPE

• Main Authors: PETERS, ANDREAS, HALFPAP, CHRISTOPHER, TRITTEL, ROLF
• Format: Patent
• Language: English; French; German
• Published: 17.02.2010
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

Use of a steel alloy for well pipes of perforating units for perforation of borehole casings, with the steel alloy comprised, in mass-%, of Carbon (C) 0.12-0.25, Manganese (Mn) 0.5-2.0, Silicon (Si) 0.1-0.5, Nitrogen (N) 0.006-0.015, Sulfur (S) <0.005, Chromium (Cr) 0.1-1.5, Molybdenum (Mo), <0.3, Nickel (Ni) <1.0, Vanadium (V) <0.25, Niobium (Nb) 0.010-0.15, Titanium (Ti) 0.02-0.06, Boron (B) 0.001-0.006, Calcium (Ca) <0.0025, and iron as well as impurities resulting from smelting as remainder, wherein the steel alloy is heated at a heating rate of 1-100 K/s to an austenitizing temperature between 10 to 50° C. above its transformation temperature Ac3, and held at this austenitizing temperature between 0.1 and 10 minutes and austenitized, subsequently quenched at a quenching rate of >50K/s, so as to adjust a martensite content of >95%, wherein the remainder is formed of lower bainite, wherein the structure is then tempered starting from room temperature between 1 and 25 minutes at temperatures between 280° C. and 700° C., and finally cooled in air or quenched in water to room temperature, wherein the steel has a tensile strength Rm ranging from 600 MPa to 1,350 MPa at transverse notch impact toughnesses in a range between 210 and 70 J/cm2 at room temperature, wherein the product of tensile strength and transverse notch impact toughness lies in the strength range between 750 MPa and 1,200 MPa in a range of 141,000 to 165,000 MPa*J/cm2.