Simulation of the Carbides Precipitation Mechanism in 34CrMo4 and 42CrMo4 Steels

Abstract

The low-alloyed Cr-Mo steels (25CrMo4, 34CrMo4 and 42CrMo4) are used for production of important technical equipment parts in the petrochemical industry, for transportation of the gaseous hydrocarbons, concentrated acids, and lyes. They are also used for rolling of seamless tubes, in the production of pressure bottles, steel bolts, etc. Steel grades 25CrMo4 and 34CrMo4 represents materials with improved mechanical properties, mainly due to vanadium microalloying. Unfortunately, vanadium microalloyed steels are very sensitive to cracks occurrence after continuous casting and/or heating before hot rolling. This paper deals with vanadium rich precipitates MC, M 3 C 2 and M 7 C 3 formation during continuous casting process. It was verified that vanadium microalloyed steel 34CrMo4 exhibited different carbides formation mechanism and contained significantly higher rate of vanadium in M x C y carbides than steel grade 42CrMo4 using experimental data and ThermoCalc software. Understanding of the vanadium precipitation kinetics is necessary for manufacturing process optimization and internal defects limitation.