Effect of rolling water cooling rate on nano-carbide precipitates and preciptation strengthening of Ti microalloyed steel

Precipitation strengthening has an important contribution for Ti microalloy steel strength. With regard to Ti microalloyed steel produced by different rolling water cooling rate, the nano-carbide precipitates in Ti microalloyed steel were obtained by nondestructive electrolysis extraction technology, and its effect on steel strengthening were also calculated based on the phase composition and particle size distribution. The results show that a large number of nano-sized M₃C and MC precipitate exists in the Ti microalloyed steel. However, the higher water cooling rate weakens the precipitation behavior of both M₃C and MC, which induces that their mass fraction in Ti microalloyed steel decreases. In addition, with the increasing water cooling rate, the size of M₃C precipitate decreases, while that of MC precipitate has no significant relationship with the water cooling rate. Generally speaking, the high water cooling rate improves M₃C precipitation strengthening and weakens MC precipitation strengthening, but the strengthening contribution of MC precipitate still could not be ignored.