A problem of manufacturing the composite castings (Al-NaCl) with the help of impregnation is considered. Filler cooling dynamics in steel chill is investigated to avoid a surface impregnation absence. The optimum heating temperatures of filler are determined depending on magnitude of allowance for machining the unimpregnated surface layer. The computation scheme of filler cooling is given for achieving a depth of near-wall layer of filler up to critical temperature for 20 s. at chill temperature of 450°C.