Patent ID: 8900511
Filing Date: 2014-12-02
Classification: C21D,C22C

Abstract:
1. A drill collar for oil drilling comprising a high-strength nonmagnetic stainless steel, consisting of: by weight percent, 0.01 to 0.06% of C, 0.10 to 0.50% of Si, 21.0 to 24.5% of Mn, 0.040% or less of P, 0.010% or less of S, 3.1 to 6.0% of Ni, 0.10 to 0.80% of Cu, 20.5 to 24.5% of Cr, 0.10 to 1.50% of Mo, 0.0010 to 0.0050% of B, 0.010% or less of O, 0.65 to 0.90% of N, at least one element selected from th grouip consisting of Ca and Mg, said at least one element present in an amount of 0.001 to 0.10% , and the remainder being Fe and inevitable impurities; wherein said steel composition satisfies the following formulae (1) to (4): wherein [Cr], [Mo], [N], [Ni], and [C] represent the content of Cr, the content of Mo, the content of N, the content of Ni, and the content of C in said steel, respectively, and {Ni} represents the sum of [Ni], [Cu] and [N], and {Cr} represents the sum of [Cr] and [Mo]; wherein said nonmagnetic stainless steel has a magnetic permeability of 1.003-1.004; and, wherein said nonmagnetic stainless steel has tensile strength of 1279-1475 MPa.