Abstract: A light-guide unit comprises a light-forming rod and a light-transmitting rod, both rods being made from a light-permeable corrosion-resistant refractory material, for instance synthetic corundum, and coaxially arranged relative each other. According to the invention the length of the light-forming rod is equal to the thickness of the metallized layer of a lining, and the length of the light-transmitting rod is not less than the thickness of the remaining portion of the lining. The rods are connected by a protection sleeve made from a material featuring plasticity at the operating temperature of the lining, and disposed in the tube. The tube at the portion wherein the light-forming rod is disposed is filled with a first refractory material having a sintering temperature not higher than the sintering temperature of the lining, and whose resistance to the action of the products of melting is similar to that of the lining.

Abstract: A corrosion-resistant cast iron comprises (by mass %):______________________________________ carbon 2.5 to 3.2 silicon 0.95 to 2.4 manganese 0.8 to 4.0 nickel 12.0 to 18.0 chromium 0.5 to 2.0 copper 4.0 to 8.0 aluminium 0.01 to 0.3 magnesium 0.005 to 0.07 calcium 0.01 to 0.10 rare-earth metals 0.001 to 0.08 barium 0.001 to 0.1 tantalum 0.003 to 0.02 niobium 0.005 to 0.