Abstract: An apparatus for hardening a steel pipe by quenching it with cooling water, comprises a cylindrical assembly including a casing and a cover, said casing being removably mated with said cover so that said cylindrical assembly may be selectively opened or closed, a plurality of supports disposed within said cylindrical assembly for supporting a steel pipe to be hardened so as to align the steel pipe with said cylindrical assembly, and nozzle means disposed at one end of said cylindrical assembly for injecting cooling water into said cylindrical assembly for cooling water to flow both outside and inside the steel pipe in the longitudinal direction thereof. The steel pipe is uniformly quenched over its entire length.

Abstract: The method of producing steel pipe material for an oil well is characterized in that, as for the chemical composition of steel, B contained steel is adopted avoiding the addition of Ti which increases the values of non-metallic inclusions to decrease machinability, the value of N is limited to not more than 0.003% to be decreased in content of nitrides, coarse crystal grains due to the decreased content of N are prevented through austenizing of steel under rapid heating, so that such a steel pipe material for an oil well can be obtained that which has resistance to sulfide stress corrosion in addition to satisfactory strength and machinability.