Task: Translation
Input (Czech): D l pro lit  oceli sest v  z t lesa (2) ze   ruvzdorn ho materi lu, obsahuj c ho uhl k. D l obsahuje vrstvu (10), kter    ste n  nebo ·pln  zakr²v  t leso (2) a je schopn  vytvo°en  vrstvy (10a) neprostupn  pro plyny, zoxidovan  a zhuÜt n , kdy  je podrobena teplot  vyÜÜ  ne  1000 .degree.C. Vrstva (10) sest v  ze   ruvzdorn ho materi lu obsahuj c ho z rodky slinov n  zvolen  ze skupiny zahrnuj c  p len² oxid hlinit², reaktivn  p len² oxid hlinit², p ry oxidu k°emi it ho a j l. Zp sob v²roby d lu pro lit  oceli spo  v  v tom,  e zhuÜt n  vrstva (4a, 10a), nepropustn  pro plyny, se vytvo°  na povrchu lic ho kan lu (8) v pr b hu f ze tepeln ho zpracov n .\
Output (English): The invention relates to a part for the casting of steel, said part comprising a body (2) made of carbon-containing refractory material. The part has a layer (10) which coats partially or completely the body (2) and is capable to form a gas impervious layer (10a) which is oxidized and densified when brought to a temperature higher than 1000 degC. The layer (10) is comprised of a refractory material having sintering precursors being selected from the group comprising calcined alumina, reactive calcined alumina, silica fumes, and clay. Process for producing such part for casting steel is characterized in that a densified gas impervious layer (4a, 10a) is formed on a surface of a sprue (9) during heat treatment phase.