Abstract: Method for thermal surface treatment in line in a continuous casting machine associated with furnaces to heat hot-charge blooms, the method being applied to fine-grain structural steels and being suitable to obviate the precipitation of compounds of aluminum, vanadium, niobium and the like and to eliminate or at least to reduce greatly the surface faults due to tension, the method being carried out in a continuous casting line comprising at least a mould (13), a secondary cooling chamber (14), an extraction and straightening assembly (15) and a shearing assembly (17), the method being applied in cooperation with the extraction and straightening assembly (15) and including an intense, concentrated cooling of the surface of a bloom (19) passing through by applying a cooling fluid under pressure, which is water-based and is sprayed by a plurality of sprayer nozzles (18), the cooling being adapted to the dimensions of the bloom (19) and being such as to produce a surface temperature between about 400.degree. C.