METHOD FOR PRODUCING HOT-ROLLED SEAMLESS PIPES FROM TRANSFORMABLE STEEL, IN PARTICULAR FOR PIPELINES FOR DEEP-WATER APPLICATIONS, AND CORRESPONDING PIPES

摘要

A method for producing hot-rolled seamless pipes from transformable steel for pipelines in which the pipe ends are hot-upsetted in order to achieve a thickened wall portion after a final rolling process of the pipes to provide pipes with excellent fatigue, corrosion, and welding properties. A pre-selected ratio between a wall thickness of the pipe end and a wall thickness of a wall body adjoining the pipe end is set by the hot-upsetting process such that a pipe is achieved with a pipe end which has a lower strength than the pipe body after a uniform tempering process of the entire pipe following the hot-upsetting process by using a previously ascertained wall thickness-dependent cooling rate during the tempering process.

主权项

1. A method for producing hot-rolled, seamless pipes from transformable steel, for pipelines, the method comprising hot-upsetting pipe ends of pipes in order to achieve a thickened wall portion after a final rolling process of the pipes, and administering a uniform hardening and tempering treatment of the entire pipe following the hot-upsetting process, wherein a preselected ratio between a wall thickness of the pipe end and a wall thickness of a pipe body adjoining the pipe end is set by the hot-upsetting process such that the pipe end has a lower strength than the pipe body after the uniform hardening and tempering treatment of the entire pipe by using a previously ascertained wall thickness-dependent cooling rate during the hardening and tempering treatment.