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The comparative effect of molybdenum and chromium on critical points, structure and strength properties of low-carbon pipe steel after different cooling regimes is studied. It is shown that for the basic chemical composition 0.06%C–1.50% Mn–Cu–Nb–Ti addition of chromium and molybdenum leads to a reduction in Ar3 and Bs critical points for hot-worked austenite decomposition. It is noted that with use of the optimum accelerated cooling regime the difference is overcome between the effect of molybdenum and chromium on dispersion of the structure and strength properties of low-carbon pipe steel of the alloy system 0.06% C–1.50% Mn–Cu–Nb–Ti.

Results are given for industrial approval of production under casting and rolling complex conditions within the composition of a joint metallurgical company of rolled coil for tube of strength category X70 without adding niobium for three microalloying systems (V–N, V–Ti–N, V–Ti). It is shown that in order to prepare rolled coil of strength category X70 without additional specifications according to Charpy and DWWT tests at negative temperature the most suitable steel system is microalloying with vanadium and nitrogen (V–N system).

This article is devoted to determining the reasons for the fracture of rolled plates in the Z-direction. Technological recommendations are developed to improve plate quality and reduce the rate of rejection of cast and rolled steel. A method is proposed for determining the mechanical properties of the matrix and the axial segregation zone separately on one specimen.

The mechanical properties, microstructure, fractures, and texture of a trial industrial batch of 07Г2MФБ steel sheet (thickness 21.7 mm) for the manufacture of spiral-seam gas-line pipe (diameter 1420 mm) of strength class X70 at OAO Volzhskii Trubnyi Zavod (VTZ) are investigated. It is shown that the selected chemical composition of the steel and thermomechanical rolling technology yield mechanical properties of the sheet and the basic pipe metal complying with VTZ specifications.

The Azovstal’ Metallurgical Combine has conducted tests of the production of plates of low-carbon (0.06–0.08% C) low-alloy steels 06GBD and 06G2B. The plates, ranging up to 45 mm in thickness and having yield points ≥390 and ≥440 N/mm2, respectively, are intended for use in structures employed for critical applications. Both steels are microalloyed with niobium, vanadium, molybdenum, and additions of copper. It is shown that in the quenched-and-tempered state the two steels fully conform to the specifications. The plates are characterized by excellent cold resistance, impact toughness, and weldability (Ce = 0.34–0.37 for steel 06GBD and Ce = 0.38–0.41 for steel 06G2B) and satisfactory values of the ratio σy/σu (≤0.90 for plates with a thickness ≤20 mm and ≤0.85 for plates with a thickness >20 mm). The construction of serial curves describing impact work and the percentage of the ductile component in the fracture of Charpy specimens prepared from plates of steel 06GBD showed that the plates have a high resistance to brittle fracture (impact work was at least 145 J at −70°C, and the percentage of ductile fracture was 100% for 14-mm-thick plates and 80% for 32-mm-thick plates).

A rational technology is proposed for the deoxidation of low-silicon steel. It includes preliminary deoxidation by ferrosilicomanganese in metal tapping from a steel-melting unit and the introduction of aluminum ingots and aluminum rods during out-of-furnace treatment. As a result, the contamination of rolled roll sheets by nonmetallic inclusions decreases and the metal yield increases.