Experience in the Development of Production of Rolled Stock from Microalloyed Steels for Shipbuilding by NLMK DanSteel

Abstract

Due to general trends in the development of the heavy plate market in the segments of shipbuilding and marine engineering, as well as on the base of the rolling mill 4200, NLMK DanSteel has developed chemical compositions and mastered the production technology of rolled products with a thickness up to 55 mm from low carbon microalloyed steels of grades D36, D40, and D420 in the state of delivery after normalizing rolling (+NR). The developed gauge is actively used in the process of construction of cruise liners. The following aspects have been tested: the metallurgical quality of experimental-industrial, certification, and production lots of heavy plates that have a required strength level, low-temperature impact toughness at –20°C over the entire thickness; a high level of joint mechanical characteristics during welding with the use of various methods at a heat range from 15 ± 1 to 50 ± 2 kJ/cm. The developed steels remain at the required level of strength characteristics after the heat treatment at a soaking temperature above Ac3; and they are recommended for warm (580–600°C) and hot (900–940°C) forming. The results of the examinations have enabled NLMK DanSteel to pass certification tests according to the IACS rules and to confirm the quality of rolled products in accordance with the requirements of DNV-GL, RINA, and other maritime certification societies.