Cooling control system of a coiling mandrel (102; 202; 302; 402; 502; 602) for metal products originating from a hot rolling mill plant comprising: (i) a coiling mandrel (102; 202; 302; 402; 502; 602) which comprises (a) an internal shaft (108; 308) with a plurality of sectors; (b) an external drum which as a whole contains coaxially said internal shaft and which is circumferentially subdivided into a plurality of segments arranged in a direct or indirect coupling connection with said sectors, wherein the indirect coupling connection is realized by wedges coupled (106; 306) to anyone of said sectors and interposed between said segments and said sectors; (c) an internal and/or external cooling system of the mandrel; wherein said segments are movable in a radial direction with respect to said internal shaft (108; 308) by an axial movement of the latter, subsequently to the internal shaft (108; 308), causing the consequent radial expansion or collapse of the drum; the cooling control system being characterized in that said mandrel (102; 202; 302; 402; 502; 602) is provided with (d) a group of temperature detection sensors (130, 132, 134, 136; 234, 236; 332, 336; 43N; 53N; 63N; 3N); and (ii) a control unit configured to: - receive temperature data measured in the mandrel, and said control unit being provided with an algorithm which: - compares said data with temperature nominal values, - increases, reduces or maintains constant the flow of the cooling liquid based on the difference determined between the measured value of the temperature and the target nominal value of the temperature. (i) a coiling mandrel (102; 202; 302; 402; 502; 602) which comprises (a) an internal shaft (108; 308) with a plurality of sectors; (b) an external drum which as a whole contains coaxially said internal shaft and which is circumferentially subdivided into a plurality of segments arranged in a direct or indirect coupling connection with said sectors, wherein the indirect coupling connection is realized by wedges coupled (106; 306) to anyone of said sectors and interposed between said segments and said sectors; (c) an internal and/or external cooling system of the mandrel; wherein said segments are movable in a radial direction with respect to said internal shaft (108; 308) by an axial movement of the latter, subsequently to the internal shaft (108; 308), causing the consequent radial expansion or collapse of the drum; the cooling control system being characterized in that said mandrel (102; 202; 302; 402; 502; 602) is provided with (d) a group of temperature detection sensors (130, 132, 134, 136; 234, 236; 332, 336; 43N; 53N; 63N; 3N); (a) an internal shaft (108; 308) with a plurality of sectors; (b) an external drum which as a whole contains coaxially said internal shaft and which is circumferentially subdivided into a plurality of segments arranged in a direct or indirect coupling connection with said sectors, wherein the indirect coupling connection is realized by wedges coupled (106; 306) to anyone of said sectors and interposed between said segments and said sectors; (c) an internal and/or external cooling system of the mandrel; wherein said segments are movable in a radial direction with respect to said internal shaft (108; 308) by an axial movement of the latter, subsequently to the internal shaft (108; 308), causing the consequent radial expansion or collapse of the drum; the cooling control system being characterized in that said mandrel (102; 202; 302; 402; 502; 602) is provided with wherein said segments are movable in a radial direction with respect to said internal shaft (108; 308) by an axial movement of the latter, subsequently to the internal shaft (108; 308), causing the consequent radial expansion or collapse of the drum; the cooling control system being characterized in that said mandrel (102; 202; 302; 402; 502; 602) is provided with (d) a group of temperature detection sensors (130, 132, 134, 136; 234, 236; 332, 336; 43N; 53N; 63N; 3N); and (ii) a control unit configured to: - receive temperature data measured in the mandrel, and said control unit being provided with an algorithm which: - compares said data with temperature nominal values, - increases, reduces or maintains constant the flow of the cooling liquid based on the difference determined between the measured value of the temperature and the target nominal value of the temperature. - receive temperature data measured in the mandrel, and said control unit being provided with an algorithm which: - compares said data with temperature nominal values, - increases, reduces or maintains constant the flow of the cooling liquid based on the difference determined between the measured value of the temperature and the target nominal value of the temperature.