Production of plates of strength category DNV SAWL 450 SFDU, intended for manufacturing pipe with a 39 mm wall thickness for submarine pipelines, is mastered under industrial conditions at the 5000 mill of Vyksa Metallurgical Plant (VMZ). The effect of chemical composition and steel manufacturing technology on features of microstructure formation (including its morphological features and excess phase precipitation) is studied. This makes it possible to formulate the optimum ferrite-bainite microstructure after TMT and provide the required strength level and cold resistance for plates, including manufacture of double length workpieces.