Optimization of the process route of seamless steel tubes to increase the mechanical - technological properties

An intermediate cooling of tube blanks after the push bench in the seamless tube production process shows increased mechanical-technological properties on the final product. An analysis on grain size and microstructure development and an evaluation of the occurring phenomena of possible precipitations are tested on three different steel grades of intermediate cooled samples in comparison to traditionally processed tubes. Furthermore, spray water quenched tube blanks are reviewed by means of an increase of productivity during intermediate cooling. A complete mechanical – technological profile of the different steel grades was built with included assessment on recrystallized fractions during deforming and precipitation effects on strength, toughness and grain size development. Also the influence of the varying austenite grain sizes on the CCT diagram and following on the phase transformation kinetics has been observed in detail. The results from the trials give a recommendation on the optimal process route for thermomechanical treated seamless tubes with a perfect initial state for rapid cooled AHSS advanced high strength steel tubes.