PREPARATION OF STEEL PIPE WITH HIGH CRUSHING STRENGTH

摘要

PURPOSE:To enhance the corrosion resistance and the crushing strength of a steel pipe, by a method wherein a steel pipe used as an oil well pipe is uniformly cooled from the periphery thereof by a specific amount of cooling water while transferred to a pipe axis direction in a heated state. CONSTITUTION:A heated steel pipe 1 still holding heat after hardening and tempering treatment in an oil well pipe preparing process or in a stage after hot straightening processing is uniformly cooled by cooling water from a ring shaped nozzle 2 surrounding said pipe while transferred to the pipe axis direction thereof at a speed V. In this case, the cooling starting temp. of the heated steel pipe 1 is set to a temp. defined by the formula [II] upto a temp. not higher than an tempering temp., while the amount of cooling water is set to an amount defined by the formula [ I ]. As the result, an oil well pipe excellent in both corrosion resistance and crushing strength can be prepared.