Trials at a pilot plant were performed in order to develop new chemical compositions for the production of API grade X70 and X80 pipeline steels. The pilot hot rolling mill allows trials in a limited scale with the target strip thickness and strip widths between 100 mm and 500 mm. The mechanical properties of the X70 and X80 pipeline steels with thicknesses of 23 mm and 12.7 mm respectively were examined by tensile tests and charpy impact tests. In addition DWT tests were conducted for material with a thickness of 23 mm.
Some of the trials were arranged to estimate the influence of 0.3% nickel and of 0.03% vanadium with and without the addition of titanium stoichiometrical to nitrogen on the basis of a chemical composition with a niobium content above 0.06%. For a selected composition submerged arc welding trials were performed in a welding laboratory.
The results obtained in the small scale trials were used to derive chemical compositions for industrial scale trials including hot strip rolling and the production of helically welded pipes.
This paper will deal with the pilot plant trials, the welding trials and the industrial scale trials. The attained mechanical properties will be presented and compared. Furthermore future trials to develop optimized chemical compositions for pipeline steels and the challenge to transfer results from limited to industrial scale will be discussed.
