The Effect of Vanadium Content on Mechanical Properties and Structure of Self-Hardening Steel X 160C rMo 12-1

The aim of this research was to examine the influence of vanadium on the structure, hardness and tensile strength of X160CrMo12-1 self-hardened steels. It is known that vanadium affects the process of solidification of this alloy in a way that narrows temperature interval of crystallization. Vanadium, as an alloying element, moves liquidus and solidus lines toward higher temperatures, approximately for 25 to 30 С. In addition, vanadium forms V6C5 carbides, which, are partly distributed between present phases in the steel; carbide (CrFe)7C3 and austenite. The presence of vanadium enables the formation of (CrFe)23C6 carbide and its precipitation into austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite, i.e., vanadium reduces remained austenite and improves steel air-hardening. Vanadium concentration over 2.5% significantly improves the impact toughness. The basic problem in the application of high alloyed Cr-Mo steels is to increase their impact toughness and thereby sustain a relatively high value of hardness. Recent studies, concerning to the chemical composition and heat treatment regime, show that it is possible to get a martensitic structure with a very small amount of retained austenite. Investigations are directed toward the testing of the influence of alloying elements such as molybdenum, manganese and especially vanadium. Vanadium has great influence to the crystallization process. With increasing of its content, the eutectic point moves toward lower carbon concentrations and the temperature interval of solidification is narrowing.