INFLUENCE OF DIRECT ROLLING ON PRECIPITATION EVOLUTION IN HSLA STEEL SLABS.

In the 'Controlled Rolling' of HSLA slabs by the conventional method, it is possible to condition the austenite by adjusting the time- and temperature-cycle for the reheating of the slab prior to rolling. The reheating step permits the micro-alloying elements to be taken into solution in austenite to the required degree. However, in the Direct Rolling Process, such a flexibility for pre-conditioning the austenite structure does not exist. Thus the starting structure for rolling is that inherited from the as-cast state. Therefore, it is important to understand the precipitation behaviour of micro-alloying elements as influenced by the base chemistry, solidification processing and subsequent cooling of the slab in the caster.