A process model to describe the strength contribution from precipitation hardening during coiling after hot rolling has been developed for V and Nb HSLA steels. Experimental measurements of ageing behaviour on the V steel were conducted on coil material which was received in an underaged condition. The size and composition of precipitates was examined on replicas using scanning transmission electron microscopy. The precipitates were observed to be V rich and a substantial increase in precipitate size occurred as a function of ageing time. The modelling approach developed by Shercliff and Ashby for aluminium alloys was extended to microalloyed steels. The model assumes particle coarsening is the rate controlling process and that the precipitates are initially sheared by dislocations with a transition to non‐shearable precipitates at peak strength. After calibration of the model, good agreement was observed between the model predictions and experimental data. A model for ageing in a Nb HSLA steel was also developed using literature values for the ageing behaviour.