combination of these two binders namely the already formed aln and the oxycarbide which are both stable above 1 850 u00b0 c which gives rise to the remarkable properties of this new refractory the resultant binder oxidizes only very slowly in depth because it then gives rise to a very impervious layer of alpha alumina which does not spall from the brick and does not cause it to swell as a result of its thermal stability this complex binder is especially resistant to the slags produced in iron and steel metallurgy even when they are rich in lime and in iron oxide this makes this corundum brick particularly suitable for liming iron or steel making units of the h f type ladles continuous tapping nozzles as well as coal gasification reactors producing liquid ashes it has also been unexpectedly discovered that the firing results in substantially no variation of volume which is contrary to the sintering of alumina powder and allows for a better precision as to final dimensions of the product ______________________________________black corundum 5 2 mm 30 black corundum 2 0 2 mm 30 black corundum 0 0 2 mm 5 alumina fines lt 50 micrometers 15 aluminum lt 74 micrometers 15 ______________________________________ with 5 of phenolic resin used as a provisional binder and source of carbon the chemical analysis of the solid starting materials was as follows ______________________________________black corundum alumina aluminum______________________________________al sub 2 o sub 3 96 25 99 45 al 99 30sio sub 2 0 75 0 10 tio sub 2 2 45 0 05 fe sub 2 o sub 3 0 15 0 05 0 40cao 0 10 0 01 mgo 0 10 0 01 0 05na sub 2 o 0 10 0 32 k sub 2 o 0 10 0 01 100 00 100.