Influence of hot deformation strain rate on the mechanical properties and microstructure of K310 cold work tool steel

K310 is a cold work tool steel used in manufacturing of forging dies. To study hot deformation behavior and flow stress model of the steel, continuous hot compression tests in the range of 900-1100 degrees C with strain rates of 0.01, 0.1 and 1 s(-1) were performed. The dependency of the peak stress, initial stress, steady state stress. peak strain and dynamic recrystallization on Zener-Holloman parameter was determined. It was shown that the function relating stress and strain rate is generally the hyperbolic sine, since the power and exponential laws lose linearity at high and low stresses, respectively. The microstructural results showed that decreasing strain rate and increasing temperature (low Z) lead to decrease in peak strain and peak stress and activation energy for dynamic recrystallization. Meanwhile graph analyzes showed that the necklace structure is developed and grains become finer. Also, hardness results indicated that with increasing strain rate and decreasing temperature (high Z), the hardness is increased. At high temperature and strain rate, existence of cavities in grain boundaries indicated decreasing grain boundary sliding. (C) 2009 Elsevier B.V. All rights reserved.