Drilling oil casing and manufacturing method thereof

The invention discloses a drilling oil casing and a manufacturing method thereof. The drilling oil casing comprises the following chemical components in percent by weight: 0.08-0.15 percent of C, 0.8-1.5 percent of Si, 1.5-3.0 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.005 percent of S, 0.5-1.5 percent of Cr, 0.2-0.4 percent of Mo, 0.05-0.2 percent of Nb, 0.005-0.01 percent of Al, 0.001-0.002 percent of Ca, 0.0008-0.002 percent of B, 0.0001-0.0005 percent of RE, and the balance of Fe and inevitable impurities. The manufacturing method mainly comprises the following steps that a hot rolled strip is longitudinally sheared, the sheared hot rolled strip is manufactured into a tube blank through molding and welding, then the tube blank is subjected to hot stretch-reducing, on-line full tube body stepped controlled cooling is conducted on the high-temperature tube blank, the high-temperature tube blank is cooled to 500 DEG C and 350 DEG C respectively, and then is air-cooled to