MANUFACTURE OF NONMAGNETIC STEEL FOR DRILL COLLAR COMBINING HIGH CORROSION RESISTANCE WITH HIGH STRENGTH

摘要

PURPOSE:To manufacture the titled steel having always stable and superior homogeneity, ductility, and toughness by a simplified method, by specifying respective conditions of the rolling, etc., and also of ageing treatment of a steel having a specific composition which contains sufficient amount of Cr and Ni and in which C and N contents are reduced to minimum, respectively. CONSTITUTION:A steel which has a composition consisting of, by weight, =2.0%, Si, =2.0% Mn, 25-40% Ni, 18-30% Cr, 0.1-1.5% Al, 1.5-3.0% Ti, 0.0005-0.020% Ca, =0.020% C, =0.010% N, and the balance Fe and containing, if necessary, one or 2 = kinds among =3.0% Mo and =0.5% each of Zr, Nb and V is used. This steel is subjected to (a) rolling or forging at 750 deg.C at =5% draft and then to ageing treatment treatment at 650-850 deg.C, or to (b) rolling or forging at 750-850 deg.C at 5-10% draft and then to ageing treatment at 650-850 deg.C, or to (c) rolling of forging at 750-850 deg.C at =10% draft.