Fel'dman V. Perfection of chemical composition and modes of thermal treatment for propeller shafts

The object of study is the formation of structure and physical-mechanical properties of steels for the responsible use of products. The goal is the development of chemical composition and heat treatment technology economically alloyed steels for propeller shafts of large vessels, which has high ductility and toughness, coupled with sufficient strength, based on new data about the influence of microalloying and heat treatment on microstructural state and mechanical properties of medium machine-building steels. The subject is the patterns of influence of chemical composition and heat treatment on the structural condition and level of technological, mechanical and operational properties of large forgings of microalloyed hypoeutectoid steel. Methods: metallographic, microprobe, X-ray, dilatometric analysis, optical and scanning electron microscopy, determination of mechanical properties. The innovation of work - the clarification of nature of separate and complex influence of Ca, V, Zr, N, Al, Mo and Cu on the microstructure and mechanical properties of steel containing 0,26-0,32% C; the showing of the possibility of achieving a satisfactory state of macro-and mіcrostructure and mechanical properties needed in massive long (12 m) forgings from ingots weighing 132 tons, obtained by mixing of two batches hypoeutectoid steel; the refining of liquation ability of alloing elements in ingots for the manufacture of particularly large forgings (diameter of 900 mm and a length of 12 m); further developing of ideas about the influence of types of heat treatment on the complex mechanical and performance properties in relation with large-size forgings of microalloyed steel. The degree of implementation: the chemical composition of steel M27 and the method of hardening of long workpieces are developed and patented; the method of quantitative analysis of macro- and microstructure of the steel, the method of predicting the mechanical properties of steel M27 at the stage of melting are developed; the technical conditions TU 29.1-05763599-039:2005 "Billets forged ship shafts of thermoimproved microalloyed steel M27" is developed and implemented. The results of work are implemented at JSC" NKMZ "with economic benefit 253.1 thousand UAH. Scope of use - mechanical engineering.