Development of Low Carbon Equivalent and Normalized HT50 Steel with High N-V Addition

Abstract

For the decrease of C_eq. of normalized HT50 through the grain refining effect, the effect of reheating, rolling conditions and contents of V, N, Al on the mechanical properties of high N-V added steel has been investigated.
The results obtained are as follows,
1) The decrease of strength and the deterioration of toughness occur with higher content of Al in low temperature reheating. And the strength of as-rolled increases with higher V, N content within a limits of relation, V=3.64N (wt%). On the other hand, in normalized steel the adequate contents of V, N are 0.030.09%, 150200 ppm respectively. The toughness is improved with higher content of V and N, however the excess addition of V, N deteriorates the toughness in as-rolled steel.
2) The mechanical properties of high V-N added steel are influenced by VN precipitates and austenite grain size is subject to VN through Gladman's relation. And the amount of VN precipitates is decided due to the precipitation in equilibrium with residual N after precipitation of AlN.