Thermal jacket for a metallurgical vessel

Apparatus is to control the temperature of a metallic melt, comprising: a container (20) including an interior and an exterior, said interior containing the metallic melt; a thermal jacket (30); characterized in that said thermal jacket (30) includes a first portion (30a) and a second portion (30b); and an actuator mechanism is coupled to said first and second of said thermal jacket parts, said actuator mechanism adapted to move relatively said first and second parts with respect to said container and selectively positioning said first and second portions in thermal communication with said being container (20) for effecting heat transfer between said vessel and said thermal jacket (30).