Patent attributes
There is provided a production method of an internally ribbed steel tube, capable of forming spiral ribs stably so as to reduce troubles at the time of cold drawing for forming the spiral ribs of the steel tube. In this production method, the spiral ribs can be formed stably so as to reduce troubles at the time of cold drawing for forming the spiral ribs by straightening bends of a blank tube before the cold drawing for forming the spiral ribs, by optimizing the direction of the spiral rib formation after the bend straightening, and by correcting the drawing schedule depending on the blank tube. The obtained internally ribbed steel tube is well applicable to an increased capacity and a higher temperature/higher pressure operation of a boiler because the steel tube is provided with high formability and excellent quality as a boiler steel tube.
