Influence of Chemical Composition on the Structure, Hardness, and Toughness of High Alloyed Cr-Mo-V Steel

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.

Keywords:

• Air hardening steel
• Hardness
• Impact energy
• Microstructure
• Vanadium