Effects of Annealing Temperature on Microstructure and Property of Aluminum-Free Ultrahigh Carbon Steel

The annealing treatments at 800-1 100℃ were conducted on an aluminum-free ultrahigh carbon steel with nominal composition of Fe-1.58C-1.97Cr-0.26Si-0.73Mn-0.09Mo, and then the effects of the annealing temperature on the microstructure and mechanical properties of the steel were studied by the methods such as phase analysis, microstructural observation, mechanical property tests. The results show that at the annealing temperature of 800℃, a large number of net-like carbides existed in the microstructure of the tested steel. When the annealing temperature increased to 860℃, the net-like carbides disappeared and the microstructure of fine and evenly distributed cabides and pearlite was obtained. When the annealing temperature increased further to 1 100℃, the pearlite became coarse and net-like carbides precipitated again in the tested steel. With the increase of annealing temperature, the tensile strength and impact energy of the tested steel first increased then decreased and both reached the peak values at 860℃, which were 1 017 MPa and 15 J, respectively.