Prospects for an increase in the production of skelp of strength class K60 for 1420-mm-diam. Gas-line pipe at the NOSTA company

• Published in: Metallurgist (New York) Vol. 44; no. 2; pp. 74 - 78
• Main Authors: Morozov, Yu. D., Éfron, L. I., Shafigin, E. K., Stepashin, A. M.
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01.02.2000
• ISSN: 0026-0894; 1573-8892
• DOI: 10.1007/BF02463535

NOSTA has made a managerial commitment to produce high quality skelp for the natural gas pipeline market which is expected to require over 1.5 million tons of steel skelp (1420 mm dia, 20 mm wall thickness) in the next few years. This pipe must meet severe requirements including weldability, 100% ultrasonic inspection, strength, ductility, toughness, resistance to brittle fracture. Additionally, sulfur and sulfides must be limited to > =0.010% S, segregational uniformity and resistance to stress-corrosion cracking (SCC). NOSTA has progressed and mastered most of the technology required for an integrated manufacturing system to make high- quality steel and rolled products. This includes desulfurization of the pig iron and treatment outside the furnace (to ensure a low content of nonmetallic inclusions). NOSTA has lowered the sulfur content from 0.017% (1994) to 0.006% (1999). NOSTA has also successfully developed and introduced niobium bearing steels (0.003-0.006% Nb), including local thermomechanical treatment (LTMT) of the weld regions of the rolled product. Some pipes have been subject to corrosion, but a three-layer corrosion resistant coating wrap is now being supplied by the factory to master this problem. A new LTMT technique is being evaluated in which the butt weld is heated and deformed (with subsequent recrystallization) and then the HAZ and weld are quenched and tempered. This procedure doubles weld ductility and improves uniformity. NOSTA will also compare single seam pipes with two-seam pipes to determine the equivalence of the two-seam pipe from a manufacturing quality standpoint. While the technology appears to be under control, a great deal of effort and capital is needed to upgrade mills and other production equipment. Schedules for delivery and installation of production facilities are presented.