Effect of silicon on the kinetics of Nb(C, N) precipitation during the hotworking of Nb-bearing steels

The effect of Si on the rate of Nb(C, N) precipitation was investigated by using fractional softening measurements. Compression specimens, with diamet ers of 7.6 mm and lengths of 11.4 mm, were prepared from four Nh microalloy ed steels containing a range of Si concentrations from 0.01 mass% to 0.41 m ass%. Double-hit compression tests, with a strain of 0.3 for each pass and a strain rate of 6.1/sec., were employed. A solution heat treatment was app lied immediately prior to each test. It was found that the rate of Nb(C,N) precipitation in hot deformed austenite increases with Si concentration. Th is phenomenon is attributed to the increases in the activities of C and N t hat result from Si addition.