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The paper presents the results of studies of a new cast high-strength austenitic corrosion-resistant steel, which can be successfully used in shipbuilding for the manufacture of fittings. The authors included data on the structural-phase state of steel, the results of evaluating the mechanical properties, wear and corrosion resistance of the metal of castings in the cast and heat-treated state. The mechanical properties of steel are considered in detail in a wide temperature range. The impact strength was considered at low temperatures and static strength at 20 to 350 ° C. It is shown that steel has higher mechanical and corrosive properties in a wide temperature range than those of traditional stainless steels. The corrosion resistance of steel is considered. This is intergranular and pitting corrosion; the main types of corrosion are peculiar for shipbuilding. It has been shown that cast steel is superior to traditional corrosion-resistant steels in pitting corrosion resistance estimated by the pitting coefficient PREN and the critical temperature of pitting. The new cast steel has the same wear resistance as Hadfield steel.

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Corrosion-resistant steels with a high nitrogen content are used as structural materials for high-load critical products. Their high strength and ductility, austenite stability, corrosion and wear resistance are highly relevant for parts and structures operating in marine environments. In addition to a high level of operational properties, they are subject to the requirement of manufacturability, including weldability. Welding of such steels, due to the high concentration of nitrogen, is a complex technological operation, and it is necessary to avoid the appearance of gas nitrogen pores, hot cracks, a sharp drop in mechanical properties in any zones of welded joint. In this work, we investigated the regularities of changes in microhardness in different zones of welded joints (base metal, heat-affected zone of the weld, fusion zone and weld metal) of two grades of austenitic Cr-Ni-Mn-Mo-N high-strength steels with a high equilibrium nitrogen content (up to 0.6%). They fundamentally differ in the structural state of the base metal being welded: deformed (hot-rolled sheet) and cast (metal of a heat-treated cast plate). It has been shown that despite the use of different welding methods (MIG, MMA and TIG), the options for welding fillers and the type of weld groove, there are general patterns for each of the two types of base metal. The work also evaluated the correlation between these regularities and such basic characteristics of the structure and properties of rolled and cast metal of welded joints, such as the grain size and values ​​of the yield stress.

Martensitic stainless steels with 13 % Cr are widely used in many industries due to their high level of mechanical properties and acceptable corrosion resistance. The paper consolidates information about the guaranteed level of properties and the heat treatment conditions necessary for its implementation. The properties after the treatment proposed by the researchers are compared with the known properties for industrial metal. Dependences of hardness of the hardened steels of 13Cr type with 0.20 – 0.5 % C on austenitization temperature and accompanying changes in the structure were analyzed, the temperatures providing maximum hardening and the temperatures at which the steel ceases to harden were identified. Influence of the austenitization duration, heating and cooling rates on the steels properties is described. The review considers mechanical properties and corrosion resistance after quenching, quenching and tempering in relation to the structural-phase states of steels. It is shown in detail how the type of secondary phases during tempering, their quantity and distribution affect the corrosion resistance of steels with 13 % Cr. It increases with an increase in the heating temperature during austenitization and decreases with an increase in tempering temperature due to precipitation of Cr23C6 carbides and depletion of the matrix in chromium to concentrations below 12 %. The tempering temperature of 500 – 550 °C is recognized as the worst: due to the intense precipitation of carbides, the steel is not passivated, the corrosion rate is maximal. For steels of 20Kh13 type, low tempering quenching (for a combination of high strength, good corrosion resistance and satisfactory ductility) or, more often, high tempering at ~(650 – 700) °C (good ductility, satisfactory corrosion resistance) is recommended. For steels of 40Kh13 type, a temperature of ~700 °C is not recommended due to the increased concentration of carbides and insufficient corrosion resistance. Examples are given of increasing the wear resistance of steels of 40Kh13 type due to surface treatments, from nitriding to laser and plasma surface hardening.