Ultrathin hot rolled steel strips are obtained from thin slabs using a continuous casting process and production line. The process and production line includes a secondary cooling system, a roughing mill, an induction heating zone to fix temperatures of the intermediate strip chosen between 1000 and 1400.degree. C., a final rolling zone to reduce the thickness of the hot finished strip while keeping a controlled temperature of the hot rolled strip from the last stand of the finishing rolling mill higher than 750.degree. C. The strip is cooled between the last stand of the finishing rolling mill and the coiling station using a specific T.T.T diagram (time-temperature-transformation) for steel quality and strip thickness. A control system is also provided with a master system and six further peripheric sub-systems.