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The problem of achieving a higher level of ductility of pipe steels of strength grades K60 (X70) and K65 (X80) is described. Results of laboratory and industrial experiments are shown, and requirements for pipe microstructure with improved deformation capacity are formulated. Technology is described providing the specified type of structure and steel target mechanical properties, and different production schemes for LTCC are applied making it possible to achieve the prescribed strength and ductility properties over a wide variation range. Results are provided for mass industrial production of rolled product and pipe with high deformation capacity.

Results are provided for a comprehensive study of the structure and properties formation of microalloyed pipe steel produced in an AO United Metallurgical Company (Vyksa) casting and rolling complex conducted under laboratory and industrial conditions. The features of structure formation established are used to create steel compositions for electrically welded pipes and coiled rolled product manufacturing technology corresponding to steels strength classes up to K60 with improved toughness and cold resistance.

A comparative study is provided for the effect of different alloying versions on phase transformation, structure, and mechanical properties of low-alloy pipe steel. Steel alloyed economically with chromium is developed for producing sheet 21.6 (21.7) and 25.8 mm thick of strength class K60 intended for manufacturing pipe up to 1420 mm in diameter for main pipelines with a working pressure of up to 9.8 MPa.

are provided for a study of the effect of microalloying steel with niobium, titanium,, and vanadium on the level of mechanical properties and cold resistance of coiled rolled product for pipe purposes produced under conditions of the OMK-Stal casting and rolling complex (CRC). It is shown that with a standard nitrogen content in steel (less than 0.008%) under CRC conditions introduction into pipe steel of microadditions of vanadium does not provide strengthening for coiled rolled product by a precipitation hardening mechanism. Precipitation of vanadium carbide phase is difficult as a result accelerated strip cooling on the run-out table before winding strip on a coil and use of relatively low coiling temperatures under CRC conditions. Separation of VC particles after tempering at 650°C confirms retention of vanadium in solid solution. The presence of fine VN particles in steel with an increased nitrogen content may be explained by the fact the vanadium nitride phase may precipitate at higher temperatures compared with carbide. Research work has made it possible to assimilate production of cold-resistant coiled rolled product more than 10 mm thick of strength class up to K60 under CRC conditions without microalloying steel with vanadium.

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).

The microstructure of coils of pipe steel alloyed with niobium and titanium produced in a casting and rolling system is studied by means of an optical microscope and a transmission electron microscope. The mechanical properties of the steel coils are also investigated.

The influence of Nb and Ti microadditions on the microstructure and mechanical properties of coiled strip (strength class K56) produced by continuous casting and immediate rolling in a casting and rolling complex at AO OMK Stal’ (Vyksa) is investigated. High niobium content (0.08%) improves the cold strength of the steel in impact-flexure tests and drop tests at temperatures down to–80°C. Adding titanium to steel with 0.04% Nb reduces its strength but improves its plasticity, ductility, and cold strength down to–60°C.