A continuous casting facility includes an ingot mould with walls (1) formed by cooled metal walls (2) on top of which is provided a feeder bush (3) of a heat insulating material. Pressurised gas injection apertures, such as a slot (10), open into the ingot mould, at least at the interface between said feeder bush and metal wall. The facility comprises means (13 to 17) connected to said apertures for supplying a gas or gas mixture with a thermal expansion capacity controllable on the basis of the cast metal alloy composition and casting conditions. By controlling the thermal expansion capacity of the injected gas, the density of the heat flow extracted from the cast metal in the area where solidification starts can also be adjusted. The invention is particularly useful for the continuous casting of steel.