Microstructure and toughness of coarse-grained heat affected zone of vanadium microalloy wear-resisting plate
In recent years, niobium, vanadium, titanium and other alloy elements have been extensively studied on the microstructure and properties of welding heat affected zone (HAZ). There are different views on the effect of vanadium on the toughness of HAZ. Li believes that adding vanadium with a mass fraction of 0.05% to C-Mn wear-resistant plate will reduce the toughness of the critical heat affected zone at low temperature, while Horii's research believes that adding a small amount of vanadium on the basis of C-Mn wear-resistant plate will help improve the toughness of HAZ, and only a large amount of vanadium will reduce the toughness of HAZ.
The Gleeble-3800 was used to simulate the thermal cycling process experienced by welded coarse crystalline heat affected zones (CGHAZ). The microstructure and toughness of V wear-resistant plate, V-N wear-resistant plate, V-Ti wear-resistant plate and V-N-Ti wear-resistant plate CGHAZ under the condition of heat input of 100 kJ/cm were compared, and the precipitated phase was analyzed.
The results show that the toughness of CGHAZ is V-N-Ti wear-resisting plate, V-Ti wear-resisting plate, V-N wear-resisting plate and V wear-resisting plate from high to low. The original austenite grain size can be refined effectively by adding titanium on the basis of the composition of V wear-resistant plate. On the one hand, the addition of nitrogen on the basis of the composition of V-Ti wear-resistant plate promotes the precipitation of (Ti, V) (C, N) /TiN, and inhibits the coarsening of the original austenite grains. On the other hand, it promotes the precipitation of V (C, N), which promotes the formation of polygonal ferrite. The increase of the number of polygonal ferrites can weaken the damage of free nitrogen to toughness, and effectively improve the toughness of CGHAZ.
