amount and morphology of carbo-nitride precipitated in Nb-V-Ti-B and Nb-V-Ti microalloy steel EH420 rolling at 900~1000℃ with deformation 40%~60% by electron microanalysis and physical-chemistry phase analysis technique. The test results showed that the amount of carbo-nitride precipitated in steel rolling at 900 ℃ was more than that rolling at 1000 ℃; with degree of deformation increased from 40% to 60%
the precipitated carbo-nitride amount increased while average size decreased; and Ti-Nb carbo-nitride precipitated at whole rolling course
but V carbo-nitride precipitated only at lower rolling temperature.