CARBON DISTRIBUTION BETWEEN MATRIX, GRAIN BOUNDARIES AND DISLOCATIONS IN ULTRA LOW CARBON BAKE HARDENABLE STEELS

摘要

The evolution of the carbon distribution between bulk, grain boundaries and dislocations during both the continuous annealing and the strain aging (e.g. paint baking) of ULC BH steels is numerically simulated. The calculations are successfully fitted to strain aging experiments and internal friction measurements. An increase of the grain size together with a higher cooling rate from the annealing temperature significantly increases the bake hardenability of ULC BH steels. This is contrary to the situation in low carbon BH steels due to the presence of the cementite particle distribution between grain boundaries and matrix in the latter steel.