Precipitation behaviors of carbides in H13 steel during ESR, forging and tempering

The characteristics of precipitates in H13 steel under three different states, i. e., annealed electroslag remelting (ESR), annealing and tempering, were studied by means of carbon extraction replica technique, transmission electron microscopy, electron diffraction and energy dispersive spectroscopy. It is observed that these precipitates is composed of square-shaped ones, roundshaped ones and irregular ones below 200 nm in size, which are defined as V₈C₇, Cr₂₃C₆ and Cr₃C₂ (Cr₂VC₂), respectively. The evolution of these precipitates was analyzed, and thermodynamic calculations of precipitation were performed in the liquid phase region, the liquid-solid phase region and the solid phase region. Thermodynamic calculation and transmission electron microscopy results show that Cr₂₃C₆ and V₈C₇ cannot precipitate in both the liquid phase region and the liquid-solid phase region, but they start to precipitate only when cooling to the solid phase.