Effect of Cooling Rates after Finish Rolling on Microstructure and Properties of Microalloyed Steels Used for Fracture Splitting Con-Rods

Abstract

The effect of cooling rates after finish rolling on microstructure and properties of high strength medium carbon microalloyed steels used for fracture splitting con-rods was investigated using the methods of optical microscopy, SEM and TEM, etc. The results show that high cooling rate after finish rolling can increase the percentage of pearlite, reduce the grain size of ferrite and lamellar spacing of pearlite. The precipitations in the steel are composite phases of (V,Ti)(C,N), etc. Their granularity are about 30-170nm, and they will decrease with the speeding up cooling. The yield strength (YS) and ultimate tensile strength (UTS) are improved with increasing the cooling rate. The impact fracture surface shows distinct brittle fracture character.