Abstract
The investigation of the influence of vanadium to the structure, hardness, and impact toughness of air-hardening steel type X180CrMo12-1 is presented in this article. Vanadium has influence to the hardening process of these alloys by narrowing temperature range of the crystallization. Furthermore, in the process of separation of primary austenite from the solution, V6C5 carbides are formed, blocking further growth of austenite dendrites and helping the formation of small grained structure. This alloying element moves liquidus and solidus lines toward higher temperatures. Vanadium, similar to molybdenum, forms V6C5 carbides, and is distributed between present phases in the steel, carbide (Cr,Fe)7C3, and austenite. The existence of vanadium enables formation of (Cr,Fe)23C6 carbide and its precipitation in the austenite during the cooling process, and its transformation into martensite in local regions around fine carbide particles. So, actually, vanadium decreases the amount of remained austenite and improves steel air-hardening. Even in small vanadium concentrations, the impact toughness is improved, while the hardness is on the satisfactory level.