Development of high productivity casting of bars with ultrafine solidification microstructure

The final industrial goal of this project is to develop a technology for high productivity casting of small round section bars (85 mm diameter) with ultrafine solidification structure that means equiaxed structure with very low segregation. The final target is to reach productivity per strand of 30 t/h with this small diameter. To achieve this objective, two main existing technologies are combined: - a technology that leads to precisely control the initial solidification of the shell without being affected by hydrodynamic turbulence in particular level variations of the meniscus; such a method implies the use of a refractory feed head located above the cooling copper mould; - a technology that refines the internal structure of the product by inoculating the liquid metaI with steel powder, injected through a nozzle such as the hollow jet nozzle (HJN). IRSID has carried out equipment modification on its pilot continuous caster (modular mould, transformation into vertical-curved configuration) in order to adapt feed head technology to the casting of 85 mm diameter round bars at high casting speed (> 4 rn/min). Casting trials have been performed on this pilot caster in order to develop the technologies. First results were obtained concerning the influence of casting parameters: mould taper, steel grade, casting speed. CRM has studied hydrodynamic turbulence on a water model with feed head mould technology. Experimental casts were conducted on the CRM pilot to assess the feasibility of casting with a feed head mould and with low superheat.