Precipitation Behaviors and Strengthening of Carbides in H13 Steel during Annealing

Deploying optical microscopy, transmission electron microscopy, electron diffraction and energy dispersive spectrometer analysis. This article analyze the categories and shapes of carbides of three different positions in H13 ingot after annealing: upside, middle and bottom of ingot. It is found that the microstructure of H13 after annealing is composed of granular pearlite+ small amounts of ferrite and carbide phase. The categories of carbides mainly include M23C6 and MC, precipitation temperatures of which are figured out through thermodynamic calculation. Through the test of mechanical properties, it is found sample at the bottom has the optimal mechanical property. Through statistics of amounts and average sizes of precipitates and calculation of precipitation strengthening, it is found that, from upside to bottom of H13 after annealing, the size of precipitates decreases with increase of precipitation volume fraction, and contributions of precipitates to yield strength enhance gradually.